ORCID Profile
0000-0002-2213-8786
Current Organisation
Swinburne University of Technology
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Nanomaterials | Transition metal chemistry | Catalysis and mechanisms of reactions | Physical Chemistry of Materials | Manufacturing Engineering | Organic Chemistry | Natural Products Chemistry | Organic Green Chemistry | Manufacturing Processes and Technologies (excl. Textiles) | Metals and Alloy Materials | Physical Chemistry (Incl. Structural) | F-Block Chemistry | Electrochemistry | Inorganic chemistry |
ANZSRC Socio-Economic Objective (SEO)
Education and Training Systems not elsewhere classified | Energy Storage (excl. Hydrogen) | Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in Engineering | Chemical Fertilisers | Coated Metal and Metal-Coated Products
Related Links
Publications
Electrosynthesis of Highly Transparent Cobalt Oxide Water Oxidation Catalyst Films from Cobalt Aminopolycarboxylate Complexes
Publisher: Wiley
Date: 31-03-2015
Abstract: Efficient catalysis of water oxidation represents one of the major challenges en route to efficient sunlight-driven water splitting. Cobalt oxides (CoOx ) have been widely investigated as water oxidation catalysts, although the incorporation of these materials into photoelectrochemical devices has been hindered by a lack of transparency. Herein, the electrosynthesis of transparent CoOx catalyst films is described by utilizing cobalt(II) aminopolycarboxylate complexes as precursors to the oxide. These complexes allow control over the deposition rate and morphology to enable the production of thin, catalytic CoOx films on a conductive substrate, which can be exploited in integrated photoelectrochemical devices. Notably, under a bias of 1.0 V (vs. Ag/AgCl), the film deposited from [Co(NTA)(OH2 )2 ](-) (NTA=nitrilotriacetate) decreased the transmission by only 10 % at λ=500 nm, but still generated >80 % of the water oxidation current produced by a [Co(OH2 )6 ](2+) -derived oxide film whose transmission was only 40 % at λ=500 nm.
Aggregation induced emission transformation of liquid and solid-state N-doped graphene quantum dots
Publisher: Elsevier BV
Date: 04-2021
Synchrotron-Based XANES Speciation of Chromium in the Oxy-Fuel Fly Ash Collected from Lab-Scale Drop-Tube Furnace
Publisher: American Chemical Society (ACS)
Date: 07-2011
DOI: 10.1021/ES200545E
Abstract: Speciation of chromium (Cr) in the fly ash collected from oxy-firing of Victorian brown coal has been reported for the first time to address the potential formation of toxic Cr(VI) and the variation of the quantities of Cr(III)-bearing species with flue gas composition. Synchrotron-based X-ray absorption near-edge structure (XANES) was employed for Cr speciation. Apart from a pure O(2)/CO(2) mixture (27/73, v/v) versus air, the O(2)/CO(2) mixtures doped with SO(2), HCl, and steam in idually or together to simulate real flue gas have also been tested. Under all of the conditions tested here, the fractions of Cr(VI) in the fly ashes are insignificant, constituting no more than 5% of the total Cr. The test of Cr-doped brown coal in pyrolysis further confirmed that the Cr(VI) formation preferentially occurred through a local oxidation of Cr(III) at the oxygen-containing functions sites within coal matrix, rather than through an oxidation by external bulk O(2). This reaction is also highly temperature-dependent and slower than the interaction between Cr(III) and other metals such as iron oxide. Increasing temperature to 1000 °C inhibited the oxidation of Cr(IIII) to Cr(VI). Shifting the combustion gas from air to O(2)/CO(2) exerted little effect on the Cr(VI) formation. Instead, the formation of iron chromite (FeCr(2)O(4)) was facilitated in O(2)/CO(2), probably due to a strong reducing microenvironment formed by the CO(2) gasification reaction within the char matrix. The accumulation of HCl in flue gas favored the vaporization of chromium as gaseous chloride/oxychloride, as expected. The coexistence of SO(2) inhibited this phenomenon by promoting the formation of sulfate. The presence of steam was even beneficial for the inhibition of water-soluble Cr sulfate through stabilizing the majority of Cr into alumino-silicate which is in the slagging phase.
Theoretical study of K3Sb/graphene heterostructure for electrochemical nitrogen reduction reaction
Publisher: Springer Science and Business Media LLC
Date: 29-09-2022
Water-oxidation catalysis by manganese in a geochemical-like cycle
Publisher: Springer Science and Business Media LLC
Date: 15-05-2011
DOI: 10.1038/NCHEM.1049
Abstract: Water oxidation in all oxygenic photosynthetic organisms is catalysed by the Mn₄CaO₄ cluster of Photosystem II. This cluster has inspired the development of synthetic manganese catalysts for solar energy production. A photoelectrochemical device, made by impregnating a synthetic tetranuclear-manganese cluster into a Nafion matrix, has been shown to achieve efficient water oxidation catalysis. We report here in situ X-ray absorption spectroscopy and transmission electron microscopy studies that demonstrate that this cluster dissociates into Mn(II) compounds in the Nafion, which are then reoxidized to form dispersed nanoparticles of a disordered Mn(III/IV)-oxide phase. Cycling between the photoreduced product and this mineral-like solid is responsible for the observed photochemical water-oxidation catalysis. The original manganese cluster serves only as a precursor to the catalytically active material. The behaviour of Mn in Nafion therefore parallels its broader biogeochemistry, which is also dominated by cycles of oxidation into solid Mn(III/IV) oxides followed by photoreduction to Mn²⁺.
Highly active screen-printed electrocatalysts for water oxidation based on β-manganese oxide
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3EE40429C
Fe L-Edge X-ray Absorption Spectroscopy of Low-Spin Heme Relative to Non-heme Fe Complexes: Delocalization of Fe d-Electrons into the Porphyrin Ligand
Publisher: American Chemical Society (ACS)
Date: 07-12-2006
DOI: 10.1021/JA065627H
High performance acidic water electrooxidation catalysed by manganese–antimony oxides promoted by secondary metals
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3EY00046J
Abstract: Modification of the manganese–antimony oxide nanocomposites with lead produces an active and highly robust electrocatalyst for anodes of hydrogen-generating water electrolysers with proton conducting electrolytes.
Probing the Fate of Mn Complexes in Nafion: A Combined Multifrequency EPR and XAS Study
Publisher: American Chemical Society (ACS)
Date: 07-01-2016
The role of the epipeptide EpeX in defining competitive fitness in intra-species mixed isolate colony biofilms ofBacillus subtilis
Publisher: Cold Spring Harbor Laboratory
Date: 09-02-2023
DOI: 10.1101/2023.02.09.527868
Abstract: Bacteria engage in competitive interactions with neighbours that can either be of the same or different species. Multiple mechanisms are deployed to ensure the desired outcome and one tactic commonly implemented is the production of specialised metabolites. The Gram-positive bacterium Bacillus subtilis uses specialised metabolites as part of its intraspecies competition determinants to differentiate between kin and non-kin isolates. It is, however, unknown if the collection of specialised metabolites defines competitive fitness when the two isolates start as a close, interwoven community that grows into a densely packed colony biofilm. Moreover, the identity of the most effective specialised metabolites has not been revealed. Here, we determine the competition outcomes that manifest when 21 environmental isolates of B. subtilis are in idually co-incubated with the model isolate NCIB 3610 in a colony biofilm. We correlated these data with the suite of specialised metabolite biosynthesis clusters encoded by each isolate. We found that the epeXEPAB gene cluster correlated with a strong competitive phenotype. This cluster is responsible for producing the epipeptide EpeX. We demonstrated that EpeX is a competition determinant of B. subtilis in an otherwise isogenic context. When we competed the NCIB 3610 EpeX deficient strain against our suite of environmental isolates we found that the impact of EpeX in competition is isolate-specific, as only one of the 21 isolates showed increased survival when EpeX was lacking. Taken together, we have shown that EpeX is a competition determinant used by B. subtilis that impacts intra-species interactions in an isolate-specific manner.
Fe L-Edge X-ray Absorption Spectroscopy Determination of Differential Orbital Covalency of Siderophore Model Compounds: Electronic Structure Contributions to High Stability Constants
Publisher: American Chemical Society (ACS)
Date: 26-02-2010
DOI: 10.1021/JA9090098
Photon-Induced, Timescale, and Electrode Effects Critical for the in Situ X-ray Spectroscopic Analysis of Electrocatalysts: The Water Oxidation Case
Publisher: American Chemical Society (ACS)
Date: 25-10-2019
Arsenic Mobilization in a Seawater Inundated Acid Sulfate Soil
Publisher: American Chemical Society (ACS)
Date: 15-02-2010
DOI: 10.1021/ES903114Z
Abstract: Tidal seawater inundation of coastal acid sulfate soils can generate Fe- and S0(4)-reducing conditions in previously oxic-acidic sediments. This creates potential for mobilization of As during the redox transition. We explore the consequences for As by investigating the hydrology, porewater geochemistry, solid-phase speciation, and mineralogical partitioning of As across two tidal fringe toposequences. Seawater inundation induced a tidally controlled redox gradient Maximum porewater As (~400 μg/L) occurred in the shallow (<1 m), intertidal, redox transition zone between Fe-oxidizing and S0(4)-reducing conditions. Primary mechanisms of As mobilization include the reduction of solid-phase As(V) to As(lll), reductive dissolution of As(V)-bearing secondary Fe(lll) minerals and competitive anion desorption. Porewater As concentrations decreased in the zone of contemporary pyrite reformation. Oscillating hydraulic gradients caused by tidal pumping promote upward advection of As and Fe(2+)-enriched porewater in the intertidal zone, leading to accumulation of As(V)-enriched Fe(lll) (hydr)oxides at the oxic sediment-water interface. While this provides a natural reactive-Fe barrier, it does not completely retard the flux of porewater As to overtopping surface waters. Furthermore, the accumulated Fe minerals may be prone to future reductive dissolution. A conceptual model describing As hydro-geochemical coupling across an intertidal fringe is presented.
Pulcherrimin formation controls growth arrest of the Bacillus subtilis biofilm
Publisher: Proceedings of the National Academy of Sciences
Date: 19-06-2019
Abstract: Biofilm formation by Bacillus subtilis is a communal process that culminates in the formation of architecturally complex multicellular communities. Here we reveal that the transition of the biofilm into a nonexpanding phase constitutes a distinct step in the process of biofilm development. Using genetic analysis we show that B. subtilis strains lacking the ability to synthesize pulcherriminic acid form biofilms that sustain the expansion phase, thereby linking pulcherriminic acid to growth arrest. However, production of pulcherriminic acid is not sufficient to block expansion of the biofilm. It needs to be secreted into the extracellular environment where it chelates Fe 3+ from the growth medium in a nonenzymatic reaction. Utilizing mathematical modeling and a series of experimental methodologies we show that when the level of freely available iron in the environment drops below a critical threshold, expansion of the biofilm stops. Bioinformatics analysis allows us to identify the genes required for pulcherriminic acid synthesis in other Firmicutes but the patchwork presence both within and across closely related species suggests loss of these genes through multiple independent recombination events. The seemingly counterintuitive self-restriction of growth led us to explore if there were any benefits associated with pulcherriminic acid production. We identified that pulcherriminic acid producers can prevent invasion by neighboring communities through the generation of an “iron-free” zone, thereby addressing the paradox of pulcherriminic acid production by B. subtilis .
Ultrasmall CoO(OH)x Nanoparticles As a Highly Efficient “True” Cocatalyst in Porous Photoanodes for Water Splitting
Publisher: American Chemical Society (ACS)
Date: 19-06-2017
Anodic deposition of NiOx water oxidation catalysts from macrocyclic nickel(ii) complexes
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CY00017F
Evolution of Oxygen–Metal Electron Transfer and Metal Electronic States During Manganese Oxide Catalyzed Water Oxidation Revealed with In Situ Soft X‐Ray Spectroscopy
Publisher: Wiley
Date: 06-02-2019
Abstract: Manganese oxide (MnO
Local structure and photocatalytic property of sol–gel synthesized ZnO doped with transition metal oxides
Publisher: Springer Science and Business Media LLC
Date: 12-2011
Engineering disorder at a nanoscale: A combined TEM and XAS investigation of amorphous versus nanocrystalline sodium birnessite
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/CH15412
Abstract: The term amorphous metal oxide is becoming widely used in the catalysis community. The term is generally used when there are no apparent peaks in an X-ray diffraction pattern. However, the absence of such features in X-ray diffraction can mean that the material is either truly amorphous or that it is better described as nanocrystalline. By coprecipitating a sodium birnessite-like phase with and without phosphate (1.5 %), we are able to engineer two very similar but distinct materials – one that is nanocrystalline and the other that is amorphous. The two closely related phases were characterized with both Mn K-edge X-ray absorption spectroscopy and high-resolution transmission electron microscopy. These structural results were then correlated with catalytic and electrocatalytic activities for water oxidation catalysis. In this case, the amorphous phosphate-doped material was less catalytically active than the nanocrystalline material.
Tuning Catalyst Selectivity for Ammonia vs Hydrogen: An Investigation into the Coprecipitation of Mo and Fe Sulfides
Publisher: American Chemical Society (ACS)
Date: 06-06-2023
Exploring CuBi2O4 as a Promising Photocathode Material for PEC Water Splitting
Publisher: American Chemical Society (ACS)
Date: 05-09-2023
Cobalt Electrochemical Recovery from Lithium Cobalt Oxides in Deep Eutectic Choline Chloride+Urea Solvents
Publisher: Wiley
Date: 18-06-2021
Abstract: Electrochemical recovery of the cobalt in deep eutectic solvent shows its promise in recycling and recovery of valuable elements from the spent lithium‐ion battery due to its high selectivity and minimal environmental impacts. This work unveiled the roles of the substrates, applied potentials, and operating temperatures on the performance of cobalt electrochemical recovery in a deep eutectic choline chloride+urea solvent. The solvent contains cobalt and lithium ions extracted from lithium cobalt oxides – 3an essential lithium‐ion battery cathode material. Our results highlight that the substrate predetermines the cobalt recovery modes via substrate–cobalt interactions, which could be predicted by the cobalt surface segregation energies and crystallographic misfits. We also show that a moderate cathode potential under −1.0 V vs. silver quasi‐reference electrode at 94–104 °C is essential to ensure a selective cobalt recovery at an optimal rate. We also found that the stainless‐steel mesh is an optimal substrate for cobalt recovery due to its relatively high selectivity, fast recovery rate, and easy cobalt collection. Our work provides new insights on metal recovery in deep eutectic solvents and offers a new avenue to control the metal electrodeposition modes via modulation of substrate compositions and crystal structures.
Oxidant or Catalyst for Oxidation? A Study of How Structure and Disorder Change the Selectivity for Direct versus Catalytic Oxidation Mediated by Manganese(III,IV) Oxides
Publisher: American Chemical Society (ACS)
Date: 24-10-2018
Comment on “Rivalry in Bacillus subtilis colonies: enemy or family?”
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9SM02141H
Abstract: It is well known that biofilms are one of the most widespread forms of life on Earth, capable of colonising almost any environment from humans to metals.
Lateral interactions govern self-assembly of the bacterial biofilm matrix protein BslA
Publisher: Proceedings of the National Academy of Sciences
Date: 30-10-2023
Abiotic transformations of nitrogen mediated by iron sulfides and related species from early Earth to catalyst design
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3QI01553J
Rates of Water Exchange for Two Cobalt(II) Heteropolyoxotungstate Compounds in Aqueous Solution
Publisher: Wiley
Date: 17-03-2011
Abstract: Polyoxometalate ions are used as ligands in water-oxidation processes related to solar energy production. An important step in these reactions is the association and dissociation of water from the catalytic sites, the rates of which are unknown. Here we report the exchange rates of water ligated to Co(II) atoms in two polyoxotungstate sandwich molecules using the (17)O-NMR-based Swift-Connick method. The compounds were the [Co(4)(H(2)O)(2)(B-α-PW(9)O(34))(2)](10-) and the larger αββα-[Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)](16-) ions, each with two water molecules bound trans to one another in a Co(II) sandwich between the tungstate ligands. The clusters, in both solid and solution state, were characterized by a range of methods, including NMR, EPR, FT-IR, UV-Vis, and EXAFS spectroscopy, ESI-MS, single-crystal X-ray crystallography, and potentiometry. For [Co(4)(H(2)O)(2)(B-α-PW(9)O(34))(2)](10-) at pH 5.4, we estimate: k(298)=1.5(5)±0.3×10(6) s(-1), ΔH(≠)=39.8±0.4 kJ mol(-1), ΔS(≠)=+7.1±1.2 J mol(-1) K(-1) and ΔV(≠)=5.6 ±1.6 cm(3) mol(-1). For the Wells-Dawson sandwich cluster (αββα-[Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)](16-)) at pH 5.54, we find: k(298)=1.6(2)±0.3×10(6) s(-1), ΔH(≠)=27.6±0.4 kJ mol(-1) ΔS(≠)=-33±1.3 J mol(-1) K(-1) and ΔV(≠)=2.2±1.4 cm(3) mol(-1) at pH 5.2. The molecules are clearly stable and monospecific in slightly acidic solutions, but dissociate in strongly acidic solutions. This dissociation is detectable by EPR spectroscopy as S=3/2 Co(II) species (such as the [Co(H(2)O)(6)](2+) monomer ion) and by the significant reduction of the Co-Co vector in the XAS spectra.
The majority of the matrix protein TapA is dispensable for biofilm formation by Bacillus subtilis
Publisher: Cold Spring Harbor Laboratory
Date: 07-10-2019
DOI: 10.1101/794164
Abstract: Biofilm formation is a co-operative behaviour where microbial cells become embedded in an extracellular matrix. This biomolecular matrix plays a key role in the manifestation of the beneficial or detrimental outcome mediated by the collective of cells. Bacillus subtilis is an important bacterium for understanding the general principles of biofilm formation and is a plant growth-promoting organism. The protein components of the B. subtilis matrix include the secreted proteins BslA, which forms a hydrophobic coat over the biofilm, and TasA, which forms protease-resistant fibres needed for structuring. A third protein TapA (for T asA a nchoring and assembly p rotein) is needed for biofilm formation and helps TasA fibre formation in vivo but is dispensable for TasA-fibre assembly in vitro . Here we show that TapA is subjected to proteolytic cleavage in the biofilm and that only the first 57 amino acids of the 253-amino acid protein are required for biofilm architecture. However, through the construction of a strain which lacks all eight extracellular proteases, we show that proteolytic cleavage by these enzymes is not a prerequisite for TapA function. It remains unknown why TapA is synthesized at a full length of 253 amino acids when the first 57 are sufficient for biofilm structuring, but the findings do not exclude the core conserved region of TapA having a second role beyond that of structuring the B. subtilis biofilm.
Insight into pH‐Dependent Formation of Manganese Oxide Phases in Electrodeposited Catalytic Films Probed by Soft X‐Ray Absorption Spectroscopy
Publisher: Wiley
Date: 20-06-2018
Abstract: MnO
Intrinsically stable in situ generated electrocatalyst for long-term oxidation of acidic water at up to 80 °C
Publisher: Springer Science and Business Media LLC
Date: 13-05-2019
Redox Properties of Iron Sulfides: Direct versus Catalytic Reduction and Implications for Catalyst Design
Publisher: Wiley
Date: 27-04-2022
Abstract: In electrocatalysis we seldom think about the competing direct reduction reactions that may happen alongside catalytically mediated reduction‐ with direct redox chemistry often happening slower but in competition with, catalysis. One class of compounds of interest from this perspective are iron sulfides. In addition to being structurally similar to many metalloproteins, iron sulfides are also among nature‘s strongest chemical reductants and reported to act as catalysts for key chemical reactions including proton, nitrite, and nitrate reduction. It is important that iron sulfides can act as catalysts because they are also strong enough reductants to mediate some of the same reactions directly. This is paradoxical because in order to be a catalyst for reduction, an iron sulfide cannot also be oxidised. To investigate this phenomenon further, we assembled a test set of iron sulfides spanning both amorphous iron sulfide (FeS am ) as well as the crystalline iron sulfides greigite, pyrite, and troilite. These were used to explore the relationship between direct reduction and catalysis of a reduction reaction with a secondary electron source, NO 2 − was chosen as a test substrate. The trends in direct reduction followed the least stable material (FeS am ) to the most stable material (FeS 2 ). Of the phases studied, troilite (FeS) showed the largest difference between direct and catalytic reduction, however amorphous iron sulfide showed the greatest selectivity for NH 3 /NH 4 + production as both a direct reductant and a catalyst.
The Diverse Structures and Functions of Surfactant Proteins.
Publisher: Elsevier BV
Date: 07-2016
Extraction of metals from mildly acidic tropical soils: Interactions between chelating ligand, pH and soil type
Publisher: Elsevier BV
Date: 06-2020
BslA-stabilized emulsion droplets with designed microstructure
Publisher: The Royal Society
Date: 16-06-2017
Abstract: Emulsions are a central component of many modern formulations in food, pharmaceuticals, agrichemicals and personal care products. The droplets in these formulations are limited to being spherical as a consequence of the interfacial tension between the dispersed phase and continuous phase. The ability to control emulsion droplet morphology and stabilize non-spherical droplets would enable the modification of emulsion properties such as stability, substrate binding, delivery rate and rheology. One way of controlling droplet microstructure is to apply an elastic film around the droplet to prevent it from relaxing into a sphere. We have previously shown that BslA, an interfacial protein produced by the bacterial genus Bacillus , forms an elastic film when exposed to an oil- or air–water interface. Here, we highlight BslA's ability to stabilize anisotropic emulsion droplets. First, we show that BslA is capable of arresting dynamic emulsification processes leading to emulsions with variable morphologies depending on the conditions and emulsification technique applied. We then show that frozen emulsion droplets can be manipulated to induce partial coalescence. The structure of the partially coalesced droplets is retained after melting, but only when there is sufficient free BslA in the continuous phase. That the fidelity of replication can be tuned by adjusting the amount of free BslA in solution suggests that freezing BslA-stabilized droplets disrupts the BslA film. Finally, we use BslA's ability to preserve emulsion droplet structural integrity throughout the melting process to design emulsion droplets with a chosen shape and size.
New Developments in Charge Transfer Multiplet Calculations: Projection Operators, Mixed-Spin States and π-Bonding
Publisher: AIP
Date: 2007
DOI: 10.1063/1.2644448
Tunable living bacterial networks: A multi-scaled description of their self-assembly and mechanical behaviour
Publisher: Cold Spring Harbor Laboratory
Date: 05-09-2023
Economic significance of biofilms: a multidisciplinary and cross-sectoral challenge
Publisher: Springer Science and Business Media LLC
Date: 26-05-2022
DOI: 10.1038/S41522-022-00306-Y
Abstract: The increasing awareness of the significance of microbial biofilms across different sectors is continuously revealing new areas of opportunity in the development of innovative technologies in translational research, which can address their detrimental effects, as well as exploit their benefits. Due to the extent of sectors affected by microbial biofilms, capturing their real financial impact has been difficult. This perspective highlights this impact globally, based on figures identified in a recent in-depth market analysis commissioned by the UK’s National Biofilms Innovation Centre (NBIC). The outputs from this analysis and the workshops organised by NBIC on its research strategic themes have revealed the breath of opportunities for translational research in microbial biofilms. However, there are still many outstanding scientific and technological challenges which must be addressed in order to catalyse these opportunities. This perspective discusses some of these challenges.
Density and temperature controlled fluid extraction in a bacterial biofilm is determined by poly-γ-glutamic acid production
Publisher: Cold Spring Harbor Laboratory
Date: 21-12-2020
DOI: 10.1101/2020.12.21.423644
Abstract: A hallmark of microbial biofilms is the self-production of extracellular matrix that encases the cells resident within the community. The matrix provides protection from the environment, while spatial heterogeneity of expression influences the structural morphology and colony spreading dynamics. Bacillus subtilis is a model bacterial system used to uncover the regulatory pathways and key building blocks required for biofilm growth and development. Previous reports have suggested that poly- γ -glutamic acid (PGA) production is suppressed during biofilm formation and does not play a major role in biofilm morphology of the undomesticated isolate NCIB 3610. In this work we report on the observation of multiple travelling fronts that develop during the early stage of B. subtilis colony biofilm formation. We find the emergence of a highly motile population of bacteria that is facilitated by the extraction of fluid from the underlying agar substrate. Motility develops behind a moving front of fluid that propagates from the boundary of the biofilm towards the interior. The extent of proliferation is strongly modulated by the presence of extracellular polysaccharides (EPS). We trace the origin of this moving front of fluid to the production of PGA. We find that PGA production is correlated with higher temperatures, resulting in a mature biofilm morphology that is distinct from the biofilm architecture typically associated with B. subtilis . Our results suggest that B. subtilis NCIB 3610 produces distinct biofilm matrices in response to environmental conditions.
Water oxidation catalysis by nanoparticulate manganese oxide thin films: Probing the effect of the manganese precursors
Publisher: American Chemical Society (ACS)
Date: 29-03-2013
DOI: 10.1021/CM3041345
Mixed Silver–Bismuth Oxides: A Robust Oxygen Evolution Catalyst Operating at Low pH and Elevated Temperatures
Publisher: American Chemical Society (ACS)
Date: 11-10-2202
Forward and Reverse (Retro) Iron(III) or Gallium(III) Desferrioxamine E and Ring-Expanded Analogues Prepared Using Metal-Templated Synthesis from endo-Hydroxamic Acid Monomers
Publisher: American Chemical Society (ACS)
Date: 19-03-2015
DOI: 10.1021/ACS.INORGCHEM.5B00141
Abstract: A metal-templated synthesis (MTS) approach was used to preorganize the forward endo-hydroxamic acid monomer 4-[(5-aminopentyl)(hydroxy)amino]-4-oxobutanoic acid (for-PBH) about iron(III) in a 1:3 metal/ligand ratio to furnish the iron(III) siderophore for-[Fe(DFOE)] (ferrioxamine E) following peptide coupling. Substitution of for-PBH with the reverse (retro) hydroxamic acid analogue 3-(6-amino-N-hydroxyhexanamido)propanoic acid (ret-PBH) furnished ret-[Fe(DFOE)] (ret-ferrioxamine E). As isomers, for-[Fe(DFOE)] and ret-[Fe(DFOE)] gave identical mass spectrometry signals ([M + H(+)](+), m/zcalc 654.3, m/zobs 654.3), yet for-[Fe(DFOE)] eluted in a more polar window (tR = 23.44 min) than ret-[Fe(DFOE)] (tR = 28.13 min) on a C18 reverse-phase high-performance liquid chromatography (RP-HPLC) column. for-[Ga(DFOE)] (tR = 22.99 min) and ret-[Ga(DFOE)] (tR = 28.11 min) were prepared using gallium(III) as the metal-ion template and showed the same trend for the retention time. Ring-expanded analogues of for-[Fe(DFOE)] and ret-[Fe(DFOE)] were prepared from endo-hydroxamic acid monomers with one additional methylene unit in the amine-containing region, 4-[(6-aminohexyl)(hydroxy)amino]-4-oxobutanoic acid (for-HBH) or 3-(7-amino-N-hydroxyheptanamido)propanoic acid (ret-HBH), to give the corresponding tris(homoferrioxamine E) macrocycles, for-[Fe(HHDFOE)] or ret-[Fe(HHDFOE)] ([M + H(+)](+), m/zcalc 696.3, m/zobs 696.4). The MTS reaction using a constitutional isomer of for-HBH that transposed the methylene unit to the carboxylic acid containing region, 5-[(5-aminopentyl)(hydroxy)amino]-5-oxopentanoic acid (for-PPH), gave the macrocycle for-[Fe(HPDFOE)] in a yield significantly less than that for for-[Fe(HHDFOE)], with the gallium(III) analogue for-[Ga(HPDFOE)] unable to be detected. The work demonstrates the utility and limits of MTS for the assembly of macrocyclic siderophores from endo-hydroxamic acid monomers. Indirect measures (RP-HPLC order of elution, c log P values, molecular mechanics, and density functional theory calculations) of the relative water solubility of the ligands, the iron(III) macrocycles, and the apomacrocycles were consistent in identifying for-DFOE as the most water-soluble macrocycle from for-DFOE, ret-DFOE, for-HHDFOE, ret-HHDFOE, and for-HPDFOE. From this group, only for-DFOE is known in nature, which could suggest that water solubility is an important trait in its natural selection.
Defect‐Induced Pt–Co–Se Coordinated Sites with Highly Asymmetrical Electronic Distribution for Boosting Oxygen‐Involving Electrocatalysis
Publisher: Wiley
Date: 28-11-2018
Abstract: Rational design and synthesis of hetero-coordinated moieties at the atomic scale can significantly raise the performance of the catalyst and obtain mechanistic insight into the oxygen-involving electrocatalysis. Here, a facile plasma-photochemical strategy is applied to construct atomically coordinated Pt-Co-Se moieties in defective CoSe
Mobility of arsenic and selected metals during re-flooding of iron- and organic-rich acid-sulfate soil
Publisher: Elsevier BV
Date: 07-2008
Pulcherrimin formation controls growth arrest of theBacillus subtilisbiofilm
Publisher: Cold Spring Harbor Laboratory
Date: 09-03-2019
DOI: 10.1101/570630
Abstract: Biofilm formation by Bacillus subtilis is a communal process that culminates in the formation of architecturally complex multicellular communities. Here we reveal that the transition of the biofilm into a non-expanding phase constitutes a distinct step in the process of biofilm development. Using genetic analysis we show that B. subtilis strains lacking the ability to synthesize pulcherriminic acid form biofilms that sustain the expansion phase, thereby linking pulcherriminic acid to growth arrest. However, production of pulcherriminic acid is not sufficient to block expansion of the biofilm. It needs to be secreted into the extracellular environment where it chelates Fe 3+ from the growth medium in a non-enzymatic reaction. Utilizing mathematical modelling and a series of experimental methodologies we show that when the level of freely available iron in the environment drops below a critical threshold, expansion of the biofilm stops. Bioinformatics analysis allows us to identify the genes required for pulcherriminic acid synthesis in other Firmicutes but the patchwork presence both within and across closely related species suggests loss of these genes through multiple independent recombination events. The seemingly counterintuitive self-restriction of growth led us to explore if there were any benefits associated pulcherriminic acid production. We identified that pulcherriminic acid producers can prevent invasion from neighbouring communities through the generation of an “iron free” zone thereby addressing the paradox of pulcherriminic acid production by B. subtilis . Understanding the processes that underpin the mechanism of biofilm formation, dispersal, and inhibition are critical to allow exploitation and to understand how microbes thrive in the environment. Here, we reveal that the formation of an extracellular iron chelate restricts the expansion of a biofilm. The countering benefit to self-restriction of growth is protection of an environmental niche. These findings highlight the complex options and outcomes that bacteria need to balance in order to modulate their local environment to maximise colonisation, and therefore survival.
Cover Feature: Redox Properties of Iron Sulfides: Direct versus Catalytic Reduction and Implications for Catalyst Design (ChemCatChem 12/2022)
Publisher: Wiley
Date: 24-05-2022
Mixed metal–antimony oxide nanocomposites: low pH water oxidation electrocatalysts with outstanding durability at ambient and elevated temperatures
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1TA07293E
Abstract: Stability of the anode catalysts for PEM water electrolysers can be substantially improved by combining the catalytic component with antimony oxides. However, the mechanisms of the catalyst stabilisation differ depending on the active element used.
Towards hydrogen energy: Progress on catalysts for water splitting
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/CH12048
Abstract: This article reviews some of the recent work by fellows and associates of the Australian Research Council Centre of Excellence for Electromaterials Science (ACES) at Monash University and the University of Wollongong, as well as their collaborators, in the field of water oxidation and reduction catalysts. This work is focussed on the production of hydrogen for a hydrogen-based energy technology. Topics include: (1) the role and apparent relevance of the cubane-like structure of the Photosystem II Water Oxidation Complex (PSII-WOC) in non-biological homogeneous and heterogeneous water oxidation catalysts, (2) light-activated conducting polymer catalysts for both water oxidation and reduction, and (3) porphyrin-based light harvesters and catalysts.
Phosphorylated manganese oxide electrodeposited from ionic liquid as a stable, high efficiency water oxidation catalyst
Publisher: Elsevier BV
Date: 02-2013
Co-doped ZnO nanopowders: Location of cobalt and reduction in photocatalytic activity
Publisher: Elsevier BV
Date: 02-2012
Early stages of insulin fibrillogenesis examined with ion mobility mass spectrometry and molecular modelling.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5AN01253H
Abstract: Mass spectrometry shows insulin oligomers [I] n where n ranges from 1-12, and ion mobility analysis reveals ∼60 structurally distinct species across this oligomer distribution. Experimental data trains MD simulations to characterize a persistent prefibrillar protein oligomer that is a dimer enriched in β sheets.
Mixed Metal-Antimony Oxide Nanocomposites: Low pH Water Oxidation Electrocatalysts with Outstanding Durability at Ambient and Elevated Temperatures
Publisher: American Chemical Society (ACS)
Date: 22-02-2021
DOI: 10.26434/CHEMRXIV.13602764
Abstract: Proton-exchange membrane water electrolysers provide many advantages for the energy-efficient production of H sub /sub , but the current technology relies on high loadings of expensive iridium at the anodes, which are often unstable in operation. To address this, the present work scrutinises the properties of antimony-metal (Co, Mn, Ni, Fe, Ru) oxides synthesised as flat thin films by a solution-based method for the oxygen evolution reaction in 0.5 M H sub /sub SO sub /sub . Among the non-noble-metal catalysts, only cobalt-antimony and manganese-antimony oxides demonstrate high stability and reasonable activity under ambient conditions, but slowly lose activity at elevated temperatures. The ruthenium-antimony system is highly active, requiring an overpotential of 0.39 ± 0.03 and 0.34 ± 0.01 V to achieve 10 mA cm sup -2 /sup at 24 ± 2 and 80 °C, respectively, and remaining remarkably stable during one-week tests at 80 °C. The i S /i -number for this catalyst is higher than that for the high-performance benchmark Ir-based systems. Density functional theory analysis and physical characterisation reveal that this high stability is supported by the enhanced hybridisation of the oxygen p- and metal d-orbitals induced by antimony, and can arise from two distinct structural scenarios: either formation of an antimonate phase, or nanoscale intermixing of metal and antimony oxide crystallites.
The Oxidation of Peroxide by Disordered Metal Oxides: A Measurement of Thermodynamic Stability “By Proxy”
Publisher: Wiley
Date: 18-05-2018
Abstract: It is often noted that disordered materials have different chemical properties to their more "ordered" cousins. Quantifying these effects in terms of thermodynamics is challenging in part because disordered materials can be difficult to characterise and are frequently relatively unstable. During the course of our experiments to understand the effects of disorder in catalysts for water oxidation we observed that many disordered manganese and cobalt oxide water oxidation catalysts directly oxidised peroxide in contrast to their more ordered analogues which catalysed its disproportionation, that is, MnO
Sorption of Arsenic(V) and Arsenic(III) to Schwertmannite
Publisher: American Chemical Society (ACS)
Date: 18-11-2009
DOI: 10.1021/ES902461X
Abstract: This study describes the sorption of As(V) and As(III) to schwertmannite as a function of pH and arsenic loading. In general, sorption of As(V) was greatest at low pH, whereas high pH favored the sorption of As(III). The actual pH of equivalent As(V) and As(III) sorption was strongly loading dependent, decreasing from pH approximately 8.0 at loadings 4.6). Sorption of As(V) and As(III) caused significant release of SO(4)(2-) from within the schwertmannite solid-phase, without major degradation of the schwertmannite structure (as evident by X-ray diffraction and Raman spectroscopy). This can be interpreted as arsenic sorption via incorporation into the schwertmannite structure, rather than merely surface complexation at the mineral-water interface. The results of this study have important implications for arsenic mobility in the presence of schwertmannite, such as in areas affected by acid-mine drainage and acid-sulfate soils. In particular, arsenic speciation, arsenic loading, and pH should be considered when predicting and managing arsenic mobility in schwertmannite-rich systems.
Cobalt complexes with tripodal ligands: implications for the design of drug chaperones
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2DT30727H
Abstract: Extensive research is currently being conducted into metal complexes that can selectively deliver cytotoxins to hypoxic regions in tumours. The development of pharmacologically suitable agents requires an understanding of appropriate ligand-metal systems for chaperoning cytotoxins. In this study, cobalt complexes with tripodal tren (tris-(2-aminoethyl)amine) and tpa (tris-(2-pyridylmethyl)amine) ligands were prepared with ancillary hydroxamic acid, β-diketone and catechol ligands and several parameters, including: pK(a), reduction potential and cytotoxicity were investigated. Fluorescence studies demonstrated that only tpa complexes with β-diketones showed any reduction by ascorbate in situ and similarly, cellular cytotoxicity results demonstrated that ligation to cobalt masked the cytotoxicity of the ancillary groups in all complexes except the tpa diketone derivative [Co(naac)tpa](ClO(4))(2) (naac = 1-methyl-3-(2-naphthyl)propane-1,3-dione). Additionally, it was shown that the hydroxamic acid complexes could be isolated in both the hydroxamate and hydroximate form and the pK(a) values (5.3-8.5) reveal that the reversible protonation/deprotonation of the complexes occurs at physiologically relevant pHs. These results have clear implications for the future design of prodrugs using cobalt moieties as chaperones, providing a basis for the design of cobalt complexes that are both more readily reduced and more readily taken up by cells in hypoxic and acidic environments.
Fe L-Edge XAS Studies of K4[Fe(CN)6] and K3[Fe(CN)6]: A Direct Probe of Back-Bonding
Publisher: American Chemical Society (ACS)
Date: 22-07-2006
DOI: 10.1021/JA061802I
Abstract: Distinct spectral features at the Fe L-edge of the two compounds K3[Fe(CN)6] and K4[Fe(CN)6] have been identified and characterized as arising from contributions of the ligand pi orbitals due to metal-to-ligand back-bonding. In addition, the L-edge energy shifts and total intensities allow changes in the ligand field and effective nuclear charge to be determined. It is found that the ligand field term dominates the edge energy shift. The results of the experimental analysis were compared to BP86 DFT calculations. The overall agreement between the calculations and experiment is good however, a larger difference in the amount of pi back-donation between Fe(II) and Fe(III) is found experimentally. The analysis of L-edge spectral shape, energy shift, and total intensity demonstrates that Fe L-edge X-ray absorption spectroscopy provides a direct probe of metal-to-ligand back-bonding.
Insights into the van der Waals Radius of Low-Spin Ni(ii) fromMolecular Mechanics Studies and the Crystal Structures of [Ni(cis-cyclohexane-1,3-diamine)2]Cl2, [Ni{(R)-5,5,7-trimethyl-1,4-diazacyclohep
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/CH02099
Abstract: The structures of three bis(diamine)nickel(II) complexes, chosen to shed light on the van der Waals radius of nickel(II), are described. [Ni(cis-1,3-chxn)2]Cl2 (cis-1,3-chxn = cis-cyclohexane-1,3-diamine) crystallizes in the monoclinic space group P21/n, with a 6.397(2), b 16.463(4), c 7.229(2) Å, b 90.70(2)�, and its structure has been refined to an R value of 0.031 on 1214F. [Ni{(R)-tmdz}2]Cl2�H2O (tmdz = 5,5,7-trimethyl-1,4-diazacycloheptane) crystallizes in the orthorhombic space group P212121, with a 10.678(1), b 11.073(5), c 17.968(6) Å, and its structure has been refined to an R value of 0.031 on 1586F. [Ni(dmdz)2](ClO4)2 (dmdz = 5,7-dimethyl-1,4-diaza- cycloheptane) crystallizes in the monoclinic space group P21/n, with a 9.582(1), b 10.390(2), c 11.817(3) Å, β 96.19(2)�, and its structure has been refined to an R value of 0.059 on 817F. In all three structures, short Ni���H and Ni���C interactions, ranging from 2.37 to 2.61 Å and 2.99 to 3.03 Å, respectively, are observed. Using molecular mechanics modelling to reproduce these separations, we have arrived at a van der Waals radius of 1.35 Å for low-spin nickel(ii). Analysis of Ni���O contacts in the solid state leads to a van der Waals radius of about 1.26 Å, which is consistent with the molecular mechanics derived value since these are usually longer.
Effect of manganese oxide minerals and complexes on gold mobilization and speciation
Publisher: Elsevier BV
Date: 06-2015
Enhancing Photocatalysis: Understanding the Mechanistic Diversity in Photocatalysts Modified with Single‐Atom Catalytic Sites
Publisher: Wiley
Date: 27-10-2023
Fe and S K-edge XAS determination of iron-sulfur species present in a range of acid sulfate soils: Effects of particle size and concentration on quantitative XANES determinations
Publisher: IOP Publishing
Date: 11-2009
Adsorption of the natural protein surfactant Rsn-2 onto liquid interfaces
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6CP07261E
Abstract: Using simulation and experiment we investigated the interfacial adsorption of the novel protein surfactant Rsn-2, unveiling the role of its flexible termini in this process.
Improvement of Catalytic Water Oxidation on MnOx Films by Heat Treatment
Publisher: Wiley
Date: 04-03-2013
Abstract: Manganese oxides (MnOx ) are considered to be promising catalysts for water oxidation. Electrodeposited MnOx films from aqueous electrolytes have previously been shown to exhibit a lower catalytic action than films deposited from ionic liquids when tested in strongly alkaline conditions. In this study, we describe a thermal treatment that converts the MnOx films deposited from aqueous electrolytes to highly catalytic films with comparable activity to ionic-liquid-deposited films. The films deposited from aqueous electrolytes show a remarkable improvement in the catalysis of water oxidation after heat treatment at a low temperature (≤120 °C) for 30 min. The films were characterised by using XRD and SEM, and energy-dispersive X-ray (EDX), FTIR and Raman spectroscopy, which indicate that dehydration occurs during the heat treatment without significant change to the microstructure or bulk composition. The X-ray absorption spectroscopy (XAS) results show the growth of small amounts (ca. 3-10 %) of reduced Mn species (Mn(II) or Mn(III) ) after heat treatment. The dehydration process removes structural water and hydroxyl species to result in a conductivity improvement and a more active catalyst, thereby contributing to the enhancement in water oxidation performance.
Role of Advanced Analytical Techniques in the Design and Characterization of Improved Catalysts for Water Oxidation
Publisher: Elsevier
Date: 2013
Comment on “Direct Observation of Tetrahedrally Coordinated Fe(III) in Ferrihydrite”
Publisher: American Chemical Society (ACS)
Date: 02-10-2012
DOI: 10.1021/ES303084E
DFT study of the systematic variations in metal-ligand bond lengths of coordination complexes: the crucial role of the condensed phase
Publisher: American Chemical Society (ACS)
Date: 09-2007
DOI: 10.1021/IC701166P
Abstract: The experimental M-A and M-B distances in several series of [MAnBm-n]-type complexes have been studied by DFT. Many of the structural features of the series, such as trans influences and sterically induced bond elongations, are not reproduced correctly in gas-phase DFT calculations. However, the correct trends are recovered by explicitly including environmental effects via the COSMO solvation model. These observations imply that the condensed-phase environment plays a critical role in determining the geometric structure of coordination complexes. Thus, any apparently satisfactory reproduction of the condensed-phase structure by an in vacuo calculation may mask an incorrect treatment of the interplay between different ligands attached to the same metal center.
Electrodeposited MnOx Films from Ionic Liquid for Electrocatalytic Water Oxidation
Publisher: Wiley
Date: 21-05-2012
Photoactive semiconducting metal oxides: Hydrogen gas sensing mechanisms
Publisher: Elsevier BV
Date: 05-2022
Statistical and Molecular Mechanics Analysis of the Effects of Changing Donor Type on Bond Length in the Two Series [CoIIINnO6-n] and [Ni
Publisher: American Chemical Society (ACS)
Date: 19-04-2002
DOI: 10.1021/IC010930Z
Abstract: Changes in bond lengths across the series of complexes [Co(III)N(n)O(6-n)] and [Ni(II)N(n)O(6-n)], (n = 0-6) have been examined by a statistical analysis of the bond lengths in 256 Co(III) and 205 Ni(II) complexes. In both cases a systematic reduction in both metal-N and metal-O bond lengths is observed as oxygen donors replace nitrogen in the coordination sphere. In the case of Co(III), the reduction in bond lengths is linear across the series, whereas, in the case of Ni(II), it is more asymptotic in nature. It was found that this systematic change to the inner coordination sphere produced a much larger range of bond lengths than had previously been observed by changes to the outer sphere. The trends across the two series were reproduced using molecular mechanics however, the magnitude of the change was not initially predicted correctly in either case. Alterations to molecular mechanics parameters that reproduced the trends in the [Co(III)N(n)O(6-n)] series also resulted in a significant overall improvement in the predictions of Co(III)-N bond lengths in a series of Co(III) hexaamines, with all being reproduced within 0.006 A. This improvement was taken as an indication that the bond-length reduction across the series is largely steric in origin.
Biofilm hydrophobicity in environmental isolates of Bacillus subtilis
Publisher: Microbiology Society
Date: 13-09-2021
DOI: 10.1099/MIC.0.001082
Abstract: Biofilms are communities of bacteria that are attached to a surface and surrounded by an extracellular matrix. The extracellular matrix protects the community from stressors in the environment, making biofilms robust. The Gram-positive soil bacterium Bacillus subtilis, particularly the isolate NCIB 3610, is widely used as a model for studying biofilm formation. B. subtilis NCIB 3610 forms colony biofilms that are architecturally complex and highly hydrophobic. The hydrophobicity is linked, in part, to the localisation of the protein BslA at the surface of the biofilm, which provides the community with increased resistance to biocides. As most of our knowledge about B. subtilis biofilm formation comes from one isolate, it is unclear if biofilm hydrophobicity is a widely distributed feature of the species. To address this knowledge gap, we collated a library of B. subtilis soil isolates and acquired their whole genome sequences. We used our novel isolates to examine biofilm hydrophobicity and found that, although BslA is encoded and produced by all isolates in our collection, hydrophobicity is not a universal feature of B. subtilis colony biofilms. To test whether the matrix exopolymer poly γ-glutamic acid could be masking hydrophobicity in our hydrophilic isolates, we constructed deletion mutants and found, contrary to our hypothesis, that the presence of poly γ-glutamic acid was not the reason for the observed hydrophilicity. This study highlights the natural variation in the properties of biofilms formed by different isolates and the importance of using a more erse range of isolates as representatives of a species.
Founder cell configuration drives competitive outcome within colony biofilms
Publisher: Springer Science and Business Media LLC
Date: 05-02-2022
DOI: 10.1038/S41396-022-01198-8
Abstract: Bacteria can form dense communities called biofilms, where cells are embedded in a self-produced extracellular matrix. Exploiting competitive interactions between strains within the biofilm context can have potential applications in biological, medical, and industrial systems. By combining mathematical modelling with experimental assays, we reveal that spatial structure and competitive dynamics within biofilms are significantly affected by the location and density of the founder cells used to inoculate the biofilm. Using a species-independent theoretical framework describing colony biofilm formation, we show that the observed spatial structure and relative strain biomass in a mature biofilm comprising two isogenic strains can be mapped directly to the geographical distributions of founder cells. Moreover, we define a predictor of competitive outcome that accurately forecasts relative abundance of strains based solely on the founder cells’ potential for radial expansion. Consequently, we reveal that variability of competitive outcome in biofilms inoculated at low founder density is a natural consequence of the random positioning of founding cells in the inoculum. Extension of our study to non-isogenic strains that interact through local antagonisms, shows that even for strains with different competition strengths, a race for space remains the dominant mode of competition in low founder density biofilms. Our results, verified by experimental assays using Bacillus subtilis , highlight the importance of spatial dynamics on competitive interactions within biofilms and hence to related applications.
Engineering Disorder into Heterogenite-Like Cobalt Oxides by Phosphate Doping: Implications for the Design of Water-Oxidation Catalysts
Publisher: Wiley
Date: 23-12-2017
Catalytic Activity and Impedance Behavior of Screen-Printed Nickel Oxide as Efficient Water Oxidation Catalysts
Publisher: Wiley
Date: 30-11-2015
Abstract: We report that films screen printed from nickel oxide (NiO) nanoparticles and microballs are efficient electrocatalysts for water oxidation under near-neutral and alkaline conditions. Investigations of the composition and structure of the screen-printed films by X-ray diffraction, X-ray absorption spectroscopy, and scanning electron microscopy confirmed that the material was present as the cubic NiO phase. Comparison of the catalytic activity of the microball films to that of films fabricated by using NiO nanoparticles, under similar experimental conditions, revealed that the microball films outperform nanoparticle films of similar thickness owing to a more porous structure and higher surface area. A thinner, less-resistive NiO nanoparticle film, however, was found to have higher activity per Ni atom. Anodization in borate buffer significantly improved the activity of all three films. X-ray photoelectron spectroscopy showed that during anodization, a mixed nickel oxyhydroxide phase formed on the surface of all films, which could account for the improved activity. Impedance spectroscopy revealed that surface traps contribute significantly to the resistance of the NiO films. On anodization, the trap state resistance of all films was reduced, which led to significant improvements in activity. In 1.00 m NaOH, both the microball and nanoparticle films exhibit high long-term stability and produce a stable current density of approximately 30 mA cm(-2) at 600 mV overpotential.
Direct Formation of 2D-MnOx under Conditions of Water Oxidation Catalysis
Publisher: American Chemical Society (ACS)
Date: 05-04-2018
Tunable Biogenic Manganese Oxides
Publisher: Wiley
Date: 28-08-2017
Abstract: Influence of the conditions for aerobic oxidation of Mn2+(aq) catalysed by the MnxEFG protein complex on the morphology, structure and reactivity of the resulting biogenic manganese oxides (MnO
Structural measures of element–oxygen bond covalency from the changes to the delocalisation of the carboxylate ligand
Publisher: Royal Society of Chemistry (RSC)
Date: 2005
DOI: 10.1039/B411434E
Abstract: The data set of more than 40,000 crystal structures containing the carboxylate group that have been deposited in the CSD has been used to examine the structural changes that occur in the carboxylate C-O bond lengths upon binding to different elemental centres. We report here quantifiable structural changes that are dependent on the elemental centre with which the group is interacting. For the main-group elements the trends are entirely periodic and follow those traditionally associated with covalency elements exhibiting electronegativity closest to that of oxygen exhibit the largest structural change. In addition, we find the measure is extendable to both the transition metals and the lanthanoids and actinoids. Amongst the transition metals the trends of Pauling neutrality are not only maintained, but are quantifiable. The difference between the two C-O bond lengths increases with oxidation state and decreases with an increase in coordination number. All of the lanthanoids exhibit covalency within error of each other and the bonds to the actinoids are found to be more covalent than those to the lanthanoids. From the data analysis we are able to derive a correlation between the lengths of the two carboxylate arms that allows us to quantify percentage covalent character defined in terms of the resonance contributions to the carboxylate group.
Highly efficient rutile TiO2 photocatalysts with single Cu(ii ) and Fe(iii ) surface catalytic sites
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5TA07036H
Abstract: Single Cu( ii ) and Fe( iii ) surface catalytic sites dramatically enhance the activity of rutile TiO 2 in photocatalytic degradation of 4-chlorophenol.
Impurity Tolerance of Unsaturated Ni-N-C Active Sites for Practical Electrochemical CO2 Reduction
Publisher: American Chemical Society (ACS)
Date: 09-02-2022
Intrinsic Catalytic Activity for the Alkaline Hydrogen Evolution of Layer-Expanded MoS2 Functionalized with Nanoscale Ni and Co Sulfides
Publisher: American Chemical Society (ACS)
Date: 19-05-2022
The association and aggregation of the metamorphic chemokine lymphotactin with fondaparinux: from nm molecular complexes to μm molecular assemblies.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5CC05801E
Abstract: Transmission electron microscopy and drift tube ion mobility-mass spectrometry are used to study the assemblies formed by the metamorphic chemokine lymphotactin in the presence of a model glycosaminoglycan.
Nitrogen Vacancy Induced Coordinative Reconstruction of Single‐Atom Ni Catalyst for Efficient Electrochemical CO2 Reduction
Publisher: Wiley
Date: 15-09-2021
Abstract: Transition metal nitrogen carbon based single‐atom catalysts (SACs) have exhibited superior activity and selectivity for CO 2 electroreduction to CO. A favorable local nitrogen coordination environment is key to construct efficient metal‐N moieties. Here, a facile plasma‐assisted and nitrogen vacancy (NV) induced coordinative reconstruction strategy is reported for this purpose. Under continuous plasma striking, the preformed pentagon pyrrolic N‐defects around Ni sites can be transformed to a stable pyridinic N dominant Ni‐N 2 coordination structure with promoted kinetics toward the CO 2 ‐to‐CO conversion. Both the CO selectivity and productivity increase markedly after the reconstruction, reaching a high CO Faradaic efficiency of 96% at mild overpotential of 590 mV and a large CO current density of 33 mA cm ‐2 at 890 mV. X‐ray adsorption spectroscopy and density functional theory (DFT) calculations reveal this defective local N environment decreases the restraint on central Ni atoms and provides enough space to facilitate the adsorption and activation of CO 2 molecule, leading to a reduced energy barrier for CO 2 reduction.
Iron-Monosulfide Oxidation in Natural Sediments: Resolving Microbially Mediated S Transformations Using XANES, Electron Microscopy, and Selective Extractions
Publisher: American Chemical Society (ACS)
Date: 04-2009
DOI: 10.1021/ES8036548
Abstract: Iron-monosulfide oxidation and associated S transformations in a natural sediment were examined by combining selective extractions, electron microscopy and S K-edge X-ray absorption near-edge structure (XANES) spectroscopy, The sediment examined in this study was collected from a waterway receiving acid-sulfate soil drainage. It contained a high acid-volatile sulfide content (1031 micromol g(-1)), reflecting an abundance of iron-monosulfide. The iron-monosulfide speciation in the initial sediment s le was dominated by nanocrystalline mackinawite (tetragonal FeS). At near-neutral pH and an 02 partial pressure of approximately 0.2 atm, the mackinawite was found to oxidize rapidly, with a half-time of 29 +/- 2 min. This oxidation rate did not differ significantly (P < 0.05) between abiotic versus biotic conditions, demonstrating that oxidation of nanocrystalline mackinawite was not microbially mediated. The extraction results suggested that elemental S (S8(0)) was a key intermediate S oxidation product Transmission electron microscopy showed the S8(0) to be amorphous nanoglobules, 100-200 nm in diameter. The quantitative importance of S8(0) was confirmed by linear combination XANES spectroscopy, after accounting for the inherent effect of the nanoscale S8(0) particle-size on the corresponding XANES spectrum. Both the selective extraction and XANES data showed that oxidation of S8(0) to SO4(2-) was mediated by microbial activity. In addition to directly revealing important S transformations, the XANES results support the accuracy of the selective extraction scheme employed here.
A phenomenological description of BslA assemblies across multiple length scales
Publisher: The Royal Society
Date: 28-07-2016
Abstract: Intrinsically interfacially active proteins have garnered considerable interest recently owing to their potential use in a range of materials applications. Notably, the fungal hydrophobins are known to form robust and well-organized surface layers with high mechanical strength. Recently, it was shown that the bacterial biofilm protein BslA also forms highly elastic surface layers at interfaces. Here we describe several self-assembled structures formed by BslA, both at interfaces and in bulk solution, over a range of length scales spanning from nanometres to millimetres. First, we observe transiently stable and highly elongated air bubbles formed in agitated BslA s les. We study their behaviour in a range of solution conditions and hypothesize that their dissipation is a consequence of the slow adsorption kinetics of BslA to an air–water interface. Second, we describe elongated tubules formed by BslA interfacial films when shear stresses are applied in both a Langmuir trough and a rheometer. These structures bear a striking resemblance, although much larger in scale, to the elongated air bubbles formed during agitation. Taken together, this knowledge will better inform the conditions and applications of how BslA can be used in the stabilization of multi-phase materials. This article is part of the themed issue ‘Soft interfacial materials: from fundamentals to formulation’.
Counting vacancies and nitrogen-vacancy centers in detonation nanodiamond
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6NR01888B
Abstract: Detonation nanodiamond particles (DND) contain highly-stable nitrogen-vacancy (N-V) centers, making it important for quantum-optical and biotechnology applications. However, due to the small particle size, the N-V concentrations are believed to be intrinsically very low, spawning efforts to understand the formation of N-V centers and vacancies, and increase their concentration. Here we show that vacancies in DND can be detected and quantified using simulation-aided electron energy loss spectroscopy. Despite the small particle size, we find that vacancies exist at concentrations of about 1 at%. Based on this experimental finding, we use ab initio calculations to predict that about one fifth of vacancies in DND form N-V centers. The ability to directly detect and quantify vacancies in DND, and predict the corresponding N-V formation probability, has a significant impact to those emerging technologies where higher concentrations and better dispersion of N-V centres are critically required.
Capturing the active sites of multimetallic (oxy)hydroxides for the oxygen evolution reaction
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0EE01609H
Abstract: The catalytic active sites of NiFe and NiFeCr (oxy)hydroxides are revealed by operando spectroscopic techonologies for alkaline water oxidation.
First principles study of single Fe atom supported on TiO2(001) for nitrogen reduction to ammonia
Publisher: Elsevier BV
Date: 2022
Monometallic interphasic synergy via nano-hetero-interfacing for hydrogen evolution in alkaline electrolytes
Publisher: Springer Science and Business Media LLC
Date: 02-2023
DOI: 10.1038/S41467-023-36100-3
Abstract: Electrocatalytic synergy is a functional yet underrated concept in electrocatalysis. Often, it materializes as intermetallic interaction between different metals. We demonstrate interphasic synergy in monometallic structures is as much effective. An interphasic synergy between Ni(OH) 2 and Ni-N/Ni-C phases is reported for alkaline hydrogen evolution reaction that lowers the energy barriers for hydrogen adsorption-desorption and facilitates that of hydroxyl intermediates. This makes ready-to-serve Ni active sites and allocates a large amount of Ni d -states at Fermi level to promote charge redistribution from Ni(OH) 2 to Ni-N/Ni-C and the co-adsorption of H ads and OH ads intermediates on Ni-N/Ni-C moieties. As a result, a Ni(OH) 2 @Ni-N/Ni-C hetero-hierarchical nanostructure is developed, lowering the overpotentials to deliver −10 and −100 mA cm −2 in alkaline media by 102 and 113 mV, respectively, compared to monophasic Ni(OH) 2 catalyst. This study unveils the interphasic synergy as an effective strategy to design monometallic electrocatalysts for water splitting and other energy applications.
Density and temperature controlled fluid extraction in a bacterial biofilm is determined by poly-γ-glutamic acid production
Publisher: Springer Science and Business Media LLC
Date: 17-12-2022
DOI: 10.1038/S41522-022-00361-5
Abstract: A hallmark of microbial biofilms is the self-production of an extracellular molecular matrix that encases the resident cells. The matrix provides protection from the environment, while spatial heterogeneity of gene expression influences the structural morphology and colony spreading dynamics. Bacillus subtilis is a model bacterial system used to uncover the regulatory pathways and key building blocks required for biofilm growth and development. In this work, we report on the emergence of a highly active population of bacteria during the early stages of biofilm formation, facilitated by the extraction of fluid from the underlying agar substrate. We trace the origin of this fluid extraction to the production of poly- γ -glutamic acid (PGA). The flagella-dependent activity develops behind a moving front of fluid that propagates from the boundary of the biofilm towards the interior. The extent of fluid proliferation is controlled by the presence of extracellular polysaccharides (EPS). We also find that PGA production is positively correlated with higher temperatures, resulting in high-temperature mature biofilm morphologies that are distinct from the rugose colony biofilm architecture typically associated with B. subtilis . Although previous reports have suggested that PGA production does not play a major role in biofilm morphology in the undomesticated isolate NCIB 3610, our results suggest that this strain produces distinct biofilm matrices in response to environmental conditions.
Implanting Ni-O-VOx sites into Cu-doped Ni for low-overpotential alkaline hydrogen evolution
Publisher: Springer Science and Business Media LLC
Date: 06-2020
DOI: 10.1038/S41467-020-16554-5
Abstract: Nickel-based catalysts are most commonly used in industrial alkaline water electrolysis. However, it remains a great challenge to address the sluggish reaction kinetics and severe deactivation problems of hydrogen evolution reaction (HER). Here, we show a Cu-doped Ni catalyst implanted with Ni-O-VOx sites (Ni(Cu)VOx) for alkaline HER. The optimal Ni(Cu)VOx electrode exhibits a near-zero onset overpotential and low overpotential of 21 mV to deliver –10 mA cm −2 , which is comparable to benchmark Pt/C catalyst. Evidence for the formation of Ni-O-VOx sites in Ni(Cu)VOx is established by systematic X-ray absorption spectroscopy studies. The VOx can cause a substantial d ening of Ni lattice and create an enlarged electrochemically active surface area. First-principles calculations support that the Ni-O-VOx sites are superactive and can promote the charge redistribution from Ni to VOx, which greatly weakens the H-adsorption and H 2 release free energy over Ni. This endows the Ni(Cu)VOx electrode high HER activity and long-term durability.
Nanoscale structural disorder in manganese oxide particles embedded in Nafion
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3TA14738J
Abstract: High degree of structural disorders in birnessite phase particles in Nafion are responsible for high photo-electrochemical water-oxidation activity.
Founder cell configuration drives competitive outcome within colony biofilms
Publisher: Cold Spring Harbor Laboratory
Date: 08-07-2021
DOI: 10.1101/2021.07.08.451560
Abstract: Bacteria typically form dense communities called biofilms, where cells are embedded in a self-produced extracellular matrix. Competitive interactions between strains within the biofilm context are studied due to their potential applications in biological, medical, and industrial systems. Combining mathematical modelling with experimental assays, we reveal that the spatial structure and the competitive dynamics within biofilms are significantly affected by the location and density of founder cells. Using an isogenic pair of Bacillus subtilis strains, we show that the observed spatial structure and relative strain biomass in a mature biofilm can be mapped directly to the locations of founder cells. Moreover, we define a predictor of competitive outcome that accurately forecasts relative abundance of strains based solely on the founder cells’ access to free space. Consequently, we reveal that variability of competitive outcome in biofilms inoculated at low founder density is a natural consequence of the random positioning of founding cells in the inoculum. Extending our study to non-isogenic strain pairs of B. subtilis, we show that even for strains with different antagonistic strengths, a race for space remains the dominant mode of competition in biofilms inoculated at low founder densities. Our results highlight the importance of spatial dynamics on competitive interactions within biofilms and hence to related applications.
The putative role of the epipeptide EpeX in Bacillus subtilis intra-species competition
Publisher: Microbiology Society
Date: 08-06-2023
DOI: 10.1099/MIC.0.001344
Abstract: Bacteria engage in competitive interactions with neighbours that can either be of the same or different species. Multiple mechanisms are deployed to ensure the desired outcome and one tactic commonly implemented is the production of specialised metabolites. The Gram-positive bacterium Bacillus subtilis uses specialized metabolites as part of its intra-species competition determinants to differentiate between kin and non-kin isolates. It is, however, unknown if the collection of specialized metabolites defines competitive fitness when the two isolates start as a close, interwoven community that grows into a densely packed colony biofilm. Moreover, the identity of specialized metabolites that have an active role in defining the outcome of an intra-species interaction has not been revealed. Here, we determine the competition outcomes that manifest when 21 environmental isolates of B. subtilis are in idually co-incubated with the model isolate NCIB 3610 in a colony biofilm. We correlated these data with the suite of specialized metabolite biosynthesis clusters encoded by each isolate. We found that the epeXEPAB gene cluster was primarily present in isolates with a strong competitive phenotype. This cluster is responsible for producing the epipeptide EpeX. We demonstrated that EpeX is a competition determinant of B. subtilis in an otherwise isogenic context for NCBI 3610. However, when we competed the NCIB 3610 EpeX-deficient strain against our suite of environmental isolates we found that the impact of EpeX in competition is isolate-specific, as only one of the 21 isolates showed increased survival when EpeX was lacking. Taken together, we have shown that EpeX is a competition determinant used by B. subtilis that impacts intra-species interactions but only in an isolate-specific manner.
X-ray Absorption Spectroscopy and Density Functional Theory Studies of [(H3buea)FeIII-X]n- (X = S2-, O2-, OH-
Publisher:
American Chemical Society (ACS)
Date:
12-07-2006
DOI:
10.1021/JA061618X
Abstract: Iron L-edge, iron K-edge, and sulfur K-edge X-ray absorption spectroscopy was performed on a series of compounds [Fe(III)H(3)buea(X)](n-) (X = S(2-), O(2-), OH(-)). The experimentally determined electronic structures were used to correlate to density functional theory calculations. Calculations supported by the data were then used to compare the metal-ligand bonding and to evaluate the effects of H-bonding in Fe(III)(-)O vs Fe(III)(-)S complexes. It was found that the Fe(III)(-)O bond, while less covalent, is stronger than the Fe(III)(-)S bond. This dominantly reflects the larger ionic contribution to the Fe(III)(-)O bond. The H-bonding energy (for three H-bonds) was estimated to be -25 kcal/mol for the oxo as compared to -12 kcal/mol for the sulfide ligand. This difference is attributed to the larger charge density on the oxo ligand resulting from the lower covalency of the Fe-O bond. These results were extended to consider an Fe(IV)(-)O complex with the same ligand environment. It was found that hydrogen bonding to Fe(IV)(-)O is less energetically favorable than that to Fe(III)(-)O, which reflects the highly covalent nature of the Fe(IV)(-)O bond.
Iron L-Edge X-ray Absorption Spectroscopy of Oxy-Picket Fence Porphyrin: Experimental Insight into Fe–O2 Bonding
Publisher: American Chemical Society (ACS)
Date: 10-01-2013
DOI: 10.1021/JA3103583
Evolution of Oxygen–Metal Electron Transfer and Metal Electronic States During Manganese Oxide Catalyzed Water Oxidation Revealed with In Situ Soft X‐Ray Spectroscopy
Publisher: Wiley
Date: 06-02-2019
Electron shuttle-induced oxidative transformation of arsenite on the surface of goethite and underlying mechanisms
Publisher: Elsevier BV
Date: 03-2022
DOI: 10.1016/J.JHAZMAT.2021.127780
Abstract: The redox process of electron shuttles like cysteine on iron minerals under aerobic conditions may largely determine the fate of arsenic (As) in soils, while the interfacial processes and underlying mechanisms are barely explored. This work systematically investigates the interfacial oxidation processes of As(III) on goethite induced by cysteine. Results show that the addition of cysteine significantly enhances the oxidation efficiency (~ 40%) of As(III) (C
Structural Measure of Metal−Ligand Covalency from the Bonding in Carboxylate Ligands
Publisher: American Chemical Society (ACS)
Date: 03-04-2003
DOI: 10.1021/IC034198A
Abstract: The data set of over 40 000 crystal structures containing the carboxylate group that has been reported to the CSD has been used to extract structural changes to the carboxylate group upon binding to different elemental centers. We find quantifiable structural changes to the carboxylate group depending on the elemental center it is interacting with. The trends follow those traditionally associated with covalency elements exhibiting electronegativity closest to that of oxygen exhibit the largest structural change. In addition, we find the measure is extendable to transition metal systems where we observe the trends of Pauling neutrality not only are maintained but also are quantifiable i.e., the structural change increases with oxidation state, i.e., II < III 5c > 6c. Further, the measure gives us a quantifiable measure of the difference between the covalencies of the long and short bonds of Cu(II) complexes. From the bond lengths of the bound carboxylate arm, we are able to derive bond orders and hence calculate the covalent character in the adjoining metal-carboxylate bonds. As such, we have a structurally derived quantification of metal-ligand covalency.
Visible light active rGO nanosheet encapsulated Pd quantum-sized dots decorated TiO2 nano-spheres for hydrogen gas sensing at low temperatures
Publisher: Elsevier BV
Date: 10-2023
Biofilm hydrophobicity in environmental isolates of Bacillus subtilis
Publisher: Cold Spring Harbor Laboratory
Date: 29-04-2021
DOI: 10.1101/2021.04.29.441976
Abstract: Biofilms are communities of bacteria that are attached to a surface and surrounded by an extracellular matrix. The extracellular matrix protects the community from stressors in the environment, making biofilms robust. The Gram-positive soil bacterium Bacillus subtilis , particularly the isolate NCIB 3610, is widely used as a model for studying biofilm formation. B. subtilis NCIB 3610 forms colony biofilms that are architecturally complex and highly hydrophobic. The hydrophobicity is linked, in part, to the localisation of the protein BslA at the surface of the biofilm, which provides the community with increased resistance to biocides. As most of our knowledge about B. subtilis biofilm formation comes from one isolate, it is unclear if biofilm hydrophobicity is a widely distributed feature of the species. To address this knowledge gap, we collated a library of B. subtilis soil isolates and acquired their whole genome sequences. We used our new isolates to examine biofilm hydrophobicity and found that, although BslA is encoded and produced by all isolates in our collection, hydrophobicity is not a universal feature of B. subtilis colony biofilms. To test whether the matrix exopolymer poly γ-glutamic acid could be masking hydrophobicity in our hydrophilic isolates, we constructed deletion mutants and found, contrary to our hypothesis, that the presence of poly γ-glutamic acid was not the reason behind the observed hydrophilicity. This study highlights the natural variation in the properties of biofilms formed by different isolates and the importance of using a more erse range of isolates as representatives of a species. Raw sequence reads and annotated assemblies have been submitted to the European Nucleotide Archive under accession PRJEB43128.
The Bacterial Hydrophobin BslA is a Switchable Ellipsoidal Janus Nanocolloid.
Publisher: American Chemical Society (ACS)
Date: 14-10-2015
DOI: 10.1021/ACS.LANGMUIR.5B02347
Abstract: BslA is an hiphilic protein that forms a highly hydrophobic coat around Bacillus subtilis biofilms, shielding the bacterial community from external aqueous solution. It has a unique structure featuring a distinct partition between hydrophilic and hydrophobic surfaces. This surface property is reminiscent of synthesized Janus colloids. By investigating the behavior of BslA variants at water-cyclohexane interfaces through a set of multiscale simulations informed by experimental data, we show that BslA indeed represents a biological ex le of an ellipsoidal Janus nanoparticle, whose surface interactions are, moreover, readily switchable. BslA contains a local conformational toggle, which controls its global affinity for, and orientation at, water-oil interfaces. This adaptability, together with single-point mutations, enables the fine-tuning of its solvent and interfacial interactions, and suggests that BslA could be a basis for biotechnological applications.
Phase transformation of nanosized zero-valent iron modulated by As(III) determines heavy metal passivation
Publisher: Elsevier BV
Date: 08-2022
DOI: 10.1016/J.WATRES.2022.118804
Abstract: Nanoscale zero-valent iron (nZVI) has been extensively used for the passivation of cadmium (Cd) or arsenic (As) from wastewaters, while the underlying mechanisms of nZVI reaction with coexisting Cd and As are largely overlooked. Herein, the interactions of Cd and As during the course of nZVI transformation and the corresponding effects on respective pollutant removal have been systematically investigated. Batch experiments results show that As(III) addition significantly promotes the passivation of Cd(II) by nZVI, and the removal capacity increases by 7.8 times compared to that of Cd(II) alone. However, the adsorption and oxidative transformation of As(III) are barely affected under a relatively low Cd(II) concentration. It is conducive to the adsorption of Cd(II) and As(III) using nZVI under neutral conditions. The transformation of nZVI to lepidocrocite dominates in the Cd(II) single system, while it mainly converts to amorphous Fe oxyhydroxide with the addition of As(III). As(III) notably reduces the surface charge of Fe oxyhydroxide intermediates and to form the ternary complexes with Cd (Fe-As-Cd), which is the predominant mechanism for the promoted Cd(II) passivation. This work provides new understanding of nZVI transformation coupled to Cd(II) and As(III) passivation, which are likely contributing to the heavy metalloids regulation in waters and subsurface environments.
High energy X-ray imaging of heterogeneity in charged and discharged lead-acid battery electrodes
Publisher: Elsevier BV
Date: 02-2023
Overall electrochemical splitting of water at the heterogeneous interface of nickel and iron oxide
Publisher: Springer Science and Business Media LLC
Date: 06-12-2019
DOI: 10.1038/S41467-019-13415-8
Abstract: Efficient generation of hydrogen from water-splitting is an underpinning chemistry to realize the hydrogen economy. Low cost, transition metals such as nickel and iron-based oxides/hydroxides have been regarded as promising catalysts for the oxygen evolution reaction in alkaline media with overpotentials as low as ~200 mV to achieve 10 mA cm −2 , however, they are generally unsuitable for the hydrogen evolution reaction. Herein, we show a Janus nanoparticle catalyst with a nickel–iron oxide interface and multi-site functionality for a highly efficient hydrogen evolution reaction with a comparable performance to the benchmark platinum on carbon catalyst. Density functional theory calculations reveal that the hydrogen evolution reaction catalytic activity of the nanoparticle is induced by the strong electronic coupling effect between the iron oxide and the nickel at the interface. Remarkably, the catalyst also exhibits extraordinary oxygen evolution reaction activity, enabling an active and stable bi-functional catalyst for whole cell water-splitting with, to the best of our knowledge, the highest energy efficiency (83.7%) reported to date.
Preparation and Characterization of Catalysts for Clean Energy: A Challenge for X-rays and Electrons
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/CH12016
Abstract: One of the most promising approaches to addressing the challenges of securing cheap and renewable energy sources is to design catalysts from earth abundant materials capable of promoting key chemical reactions including splitting water into hydrogen and oxygen (2H2O → 2H2 + O2) as well as both the oxidation (H2 → 2H+) and reduction (2H+ → H2) of hydrogen. Key to elucidating the origin of catalytic activity and improving catalyst design is determining molecular-level structure, in both the ‘resting state’ and in the functioning ‘active state’ of the catalysts. Herein, we explore some of the analytical challenges important for designing and studying new catalytic materials for making and using hydrogen. We discuss a case study that used the combined approach of X-ray absorption spectroscopy and transmission electron microscopy to understand the fate of the molecular cluster, [Mn4O4L6]+, in Nafion.
Reduction of the photocatalytic activity of ZnO nanoparticles for UV protection applications
Publisher: Inderscience Publishers
Date: 2012
Formation of a Nanoparticulate Birnessite‐Like Phase in Purported Molecular Water Oxidation Catalyst Systems
Publisher: Wiley
Date: 17-06-2014
In Situ Reconstruction of V‐Doped Ni2P Pre‐Catalysts with Tunable Electronic Structures for Water Oxidation
Publisher: Wiley
Date: 17-04-2021
Abstract: Nickel‐based electrocatalysts are promising candidates for oxygen evolution reaction (OER) but suffer from high activation overpotentials. Herein, in situ structural reconstruction of V‐doped Ni 2 P pre‐catalyst to form highly active NiV oxyhydroxides for OER is reported, during which the partial dissolution of V creates a disordered Ni structure with an enlarged electrochemical surface area. Operando electrochemical impedance spectroscopy reveals that the synergistic interaction between the Ni hosts and the remaining V dopants can regulate the electronic structure of NiV oxyhydroxides, which leads to enhanced kinetics for the adsorption of *OH and deprotonation of *OOH intermediates. Raman spectroscopy and X‐ray absorption spectroscopy further demonstrate that the increased content of active β‐NiOOH phase with the disordered Ni active sites contributes to OER activity enhancement. Density functional theory calculations verify that the V dopants facilitate the generation of *O intermediates during OER, which is the rate‐determining step for realizing efficient O 2 evolution. Optimization of these properties endows the NiV oxyhydroxide electrode with a low overpotential of 221 mV to deliver a current density of 10 mA cm −2 and excellent stability in the alkaline electrolyte.
Just in case it rains: building a hydrophobic biofilm the Bacillus subtilis way.
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.MIB.2016.07.012
Abstract: Over the millennia, erse species of bacteria have evolved multiple independent mechanisms to structure sessile biofilm communities that confer protection and stability to the inhabitants. The Gram-positive soil bacterium Bacillus subtilis biofilm presents as an architecturally complex, highly hydrophobic community that resists wetting by water, solvents, and biocides. This remarkable property is conferred by a small secreted protein called BslA, which self-assembles into an organized lattice at an interface. In the biofilm, production of BslA is tightly regulated and the resultant protein is secreted into the extracellular environment where it forms a very effective communal barrier allowing the resident B. subtilis cells to shelter under the protection of a protein raincoat.
Ligand Field and Molecular Orbital Theories of Transition Metal X-ray Absorption Edge Transitions
Publisher: Springer Berlin Heidelberg
Date: 2011
DOI: 10.1007/430_2011_60
Database Analysis of Transition Metal Carbonyl Bond Lengths: Insight into the Periodicity of π Back-Bonding, σ Donation, and the Factors Affecting the Electronic Structure of the TM−C⋮O Moiety
Publisher: American Chemical Society (ACS)
Date: 17-04-2007
DOI: 10.1021/OM061072N
Redox Activity and Two-Step Valence Tautomerism in a Family of Dinuclear Cobalt Complexes with a Spiroconjugated Bis(dioxolene) Ligand
Publisher: American Chemical Society (ACS)
Date: 24-05-2013
DOI: 10.1021/JA4021155
Abstract: A family of dinuclear cobalt complexes with bridging bis(dioxolene) ligands derived from 3,3,3',3'-tetramethyl-1,1'-spirobis(indane-5,5',6,6'-tetrol) (spiroH4) and ancillary ligands based on tris(2-pyridylmethyl)amine (tpa) has been synthesized and characterized. The bis(dioxolene) bridging ligand is redox-active and accessible in the (spiro(cat-cat))(4-), (spiro(SQ-cat))(3-), and (spiro(SQ-SQ))(2-) forms, (cat = catecholate, SQ = semiquinonate). Variation of the ancillary ligand (Mentpa n = 0-3) by successive methylation of the 6-position of the pyridine rings influences the redox state of the complex, governing the distribution of electrons between the cobalt centers and the bridging ligands. Pure s les of salts of the complexes [Co2(spiro)(tpa)2](2+) (1), [Co2(spiro)(Metpa)2](2+) (2), [Co2(spiro)(Me2tpa)2](2+) (3), [Co2(spiro)(Me3tpa)2](2+) (4), [Co2(spiro)(tpa)2](3+) (5), and [Co2(spiro)(tpa)2](4+) (6) have been isolated, and 1, 4, and 6 have been characterized by single crystal X-ray diffraction. Studies in the solid and solution states using multiple techniques reveal temperature invariant redox states for 1, 2, and 4-6 and provide clear evidence for four different charge distributions: 1 and 2 are Co(III)-(spiro(cat-cat))-Co(III), 4 is Co(II)-(spiro(SQ-SQ))-Co(II), 5 is Co(III)-(spiro(SQ-cat))-Co(III), and 6 is Co(III)-(spiro(SQ-SQ))-Co(III). Of the six complexes, only 3 shows evidence of temperature dependence of the charge distribution, displaying a rare thermally induced two-step valence tautomeric transition from the Co(III)-(spiro(cat-cat))-Co(III) form to Co(II)-(spiro(SQ-cat))-Co(III) and then to Co(II)-(spiro(SQ-SQ))-Co(II) in both solid and solution states. This is the first time a two-step valence tautomeric (VT) transition has been observed in solution. Partial photoinduction of the VT transition is also possible in the solid. Magnetic and spectroscopic studies of 5 and 6 reveal that spiroconjugation of the bis(dioxolene) ligand allows electronic interaction across the spiro bridge, suggesting that thermally activated vibronic coupling between the two cobalt-dioxolene moieties plays a key role in the two-step transition evident for 3.
Characterization of Energy Materials with X-ray Absorption Spectroscopy─Advantages, Challenges, and Opportunities
Publisher: American Chemical Society (ACS)
Date: 15-02-2022
Lipid‐induced polymorphic amyloid fibril formation by α‐synuclein
Publisher: Wiley
Date: 26-09-2023
DOI: 10.1002/PRO.4736
Abstract: Many proteins that self‐assemble into amyloid and amyloid‐like fibres can adopt erse polymorphic forms. These forms have been observed both in vitro and in vivo and can arise through variations in the steric‐zipper interactions between ꞵ‐sheets, variations in the arrangements between protofilaments, and differences in the number of protofilaments that make up a given fibre class. Different polymorphs arising from the same precursor molecule not only exhibit different levels of toxicity, but importantly can contribute to different disease conditions. However, the factors which contribute to formation of polymorphic forms of amyloid fibrils are not known. In this work, we show that in the presence of 1,2‐dimyristoyl‐sn‐glycero‐3‐phospho‐L‐serine, a highly abundant lipid in the plasma membrane of neurons, the aggregation of α‐synuclein is markedly accelerated and yields a ersity of polymorphic forms under identical experimental conditions. This morphological ersity includes thin and curly fibrils, helical ribbons, twisted ribbons, nanotubes, and flat sheets. Furthermore, the amyloid fibrils formed incorporate lipids into their structures, which corroborates the previous report of the presence of α‐synuclein fibrils with high lipid content in Lewy bodies. Thus, the present study demonstrates that an interface, such as that provided by a lipid membrane, can not only modulate the kinetics of α‐synuclein amyloid aggregation but also plays an important role in the formation of morphological variants by incorporating lipid molecules in the process of amyloid fibril formation. This article is protected by copyright. All rights reserved.
A Two-Step Valence Tautomeric Transition in a Dinuclear Cobalt Complex
Publisher: American Chemical Society (ACS)
Date: 20-03-2012
DOI: 10.1021/IC3002527
Abstract: A dinuclear cobalt complex with cobalt centers bridged by a bis(dioxolene) ligand exhibits a rare two-step valence tautomeric transition.
Systematic microscopical analysis reveals obligate synergy between extracellular matrix components during Bacillus subtilis colony biofilm development
Publisher: Cold Spring Harbor Laboratory
Date: 16-06-2022
DOI: 10.1101/2022.06.16.496330
Abstract: Single-species bacterial colony biofilms often present recurring morphologies that are thought to be of benefit to the population of cells within and known to be dependent on the self-produced extracellular matrix. However, much remains unknown in terms of the developmental process at the single cell level. Here, we design and implement systematic time-lapse imaging and quantitative analyses of the growth of Bacillus subtilis colony biofilms. We follow development from the initial deposition of founding cells through to the formation of large-scale complex structures. Using the model biofilm strain NCIB 3610, we examine the movement dynamics of the growing biomass and compare with those displayed by a suite of otherwise isogenic matrix-mutant strains. Correspondingly, we assess the impact of an incomplete matrix on biofilm morphologies and sessile growth rate. Our results indicate that radial expansion of colony biofilms results from ision of bacteria at the biofilm periphery rather than being driven by swelling due to fluid intake. Moreover, we show that lack of exopolysaccharide production has a negative impact on cell ision rate, and the extracellular matrix components act synergistically to give the biomass the structural strength to produce aerial protrusions and agar substrate-deforming ability.
Geometric Structure Determination of N694C Lipoxygenase: A Comparative Near-Edge X-Ray Absorption Spectroscopy and Extended X-Ray Absorption Fine Structure Study
Publisher: American Chemical Society (ACS)
Date: 26-07-2008
DOI: 10.1021/IC800580F
Durable Electrooxidation of Acidic Water Catalysed by a Cobalt‐Bismuth‐based Oxide Composite: An Unexpected Role of the F‐doped SnO2 Substrate
Publisher: Wiley
Date: 26-04-2022
Abstract: Aiming to design a catalyst for stable electrooxidation of water at low pH, the present work explores the properties and structural features of electrodeposited composite oxides based on Bi and Co, which were anticipated to provide stability and catalytical activity, respectively. Materials deposited as very thin ( ca 50 nm) films on F‐doped SnO 2 (FTO) substrate do not initially exhibit high activity in 0.1 M H 2 SO 4 , but are activated during operation through the electrooxidatively‐induced enrichment of the catalytic surface with Co and Sn oxides. The latter originate from the FTO support and are identified as an important component of the catalyst through control experiments with a Sn‐free substrate and with Sn 2+ intentionally added at the electrodeposition stage. A distinctive feature of the Co−Bi−Sn‐based electrocatalyst is the slow but persistent improvement in the activity during operation in 0.1 M H 2 SO 4 at both ambient and elevated (60 °C) temperatures, which contrasts with the continuously degrading behaviour of state‐of‐the‐art oxygen evolution catalysts at low pH. This is demonstrated by 9‐day‐long galvanostatic tests at 10 mA cm −2 , during which the Co−Bi−Sn‐based thin film catalyst shows no degradation and sustains stable water oxidation at ca 1.9 V vs . reversible hydrogen electrode. The effects of tin leaching from the support detected herein might have implications to other acidic water oxidation catalysts supported on high‐surface area doped SnO 2 materials.
Fe L- and K-edge XAS of Low-Spin Ferric Corrole: Bonding and Reactivity Relative to Low-Spin Ferric Porphyrin
Publisher: American Chemical Society (ACS)
Date: 16-01-2009
DOI: 10.1021/IC802248T
Highly dispersed and disordered nickel-iron layered hydroxides and sulphides: Robust and high-activity water oxidation catalysts
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8SE00129D
Abstract: A rapid low-temperature microwave-assisted synthesis of nickel(iron) layered hydroxides and sulphides that exhibit robust catalytic activity for electrooxidation of alkaline water is introduced.
A Surfactant-Free and Scalable General Strategy for Synthesizing Ultrathin Two-Dimensional Metal-Organic Framework Nanosheets for the Oxygen Evolution Reaction
Publisher: Wiley
Date: 08-08-2019
Abstract: Metal-organic framework (MOFs) two-dimensional (2D) nanosheets have many coordinatively unsaturated metal sites that act as active centres for catalysis. To date, limited numbers of 2D MOFs nanosheets can be obtained through top-down or bottom-up synthesis strategies. Herein, we report a 2D oxide sacrifice approach (2dOSA) to facilely synthesize ultrathin MOF-74 and BTC MOF nanosheets with a flexible combination of metal sites, which cannot be obtained through the delamination of their bulk counterparts (top-down) or the conventional solvothermal method (bottom-up). The ultrathin iron-cobalt MOF-74 nanosheets prepared are only 2.6 nm thick. The s le enriched with surface coordinatively unsaturated metal sites, exhibits a significantly higher oxygen evolution reaction reactivity than bulk FeCo MOF-74 particles and the state-of-the-art MOF catalyst. It is believed that this 2dOSA could provide a new and simple way to synthesize various ultrathin MOF nanosheets for wide applications.
Exploration of TiO2 as substrates for single metal catalysts: A DFT study
Publisher: Elsevier BV
Date: 12-2020
Examining the pharmacological and psychological treatment of child and adolescent ADHD in Australia: Protocol for a retrospective cohort study using linked national registry data
Publisher: BMJ
Date: 11-2022
DOI: 10.1136/BMJOPEN-2022-064920
Abstract: Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder which affects 5% of children globally. In Australia, it is estimated that 4.1% of children and adolescents have ADHD. While research has examined the treatment and outcomes of children with ADHD attending public mental health services during their time in the public system in Australia, it is not known what treatment they received before and after these treatment episodes, which will provide a more complete understanding of these children’s treatment journey. We will link clinical data from cohorts of children and adolescents treated in the public child and youth mental health and/or child development services in Brisbane, Melbourne and Sydney to the Medicare Benefits Schedule (MBS), Pharmaceutical Benefits Scheme (PBS) and National Death Index. MBS data will demonstrate the treatment journey with respect to clinicians seen, and treatment episodes from the public health service data sets will be examined to assess if the type and intensity of treatment are related to treatment outcomes. PBS data will reveal all psychotropic medications prescribed, allowing an examination of not just ADHD medications, but also other psychotropics which may indicate co-occurring conditions (eg, anxiety and mood disorders). Statistical analyses will include descriptive statistics to describe the rates of specific medications and clinician specialties seen. Linear and logistic regression will be used to model how treatment and sociodemographic variables relate to routinely collected outcome measures in the public health system while controlling for covarying factors. This study has been approved by the following institutional ethics committees: (1) Children’s Health Queensland Hospital and Health Service (HREC/21/QCHQ/76260), (2) The University of Queensland (2021/HE002143) and (3) The Australian Institute of Health and Welfare (EO2021/4/1300). Findings will be disseminated through peer-reviewed journals, conferences, professional associations and to public mental health services that treat ADHD.
NiFeCr Hydroxide Holey Nanosheet as Advanced Electrocatalyst for Water Oxidation
Publisher: American Chemical Society (ACS)
Date: 15-11-2017
Abstract: By introducing chromium into a nickel-iron layered double hydroxide (LDH), a nickel iron chromium hydroxide nanomesh catalyst has been achieved on nickel foam substrate via electrodeposition followed by partial etching of chromium. The electrodeposited chromium acts as a sacrificial template to introduce holes in the LDH to increase the electrochemically active surface area, and the remaining chromium synergistically modulates the electronic structure of the composite. The obtained electrode shows extraordinary performance for oxygen evolution reaction and excellent electrochemical stability. The onset potential of the as-prepared electrode in 1 M KOH is only 1.43 V vs RHE, and the overpotential to achieve a high current density of 100 mA·cm
Highly active nickel oxide water oxidation catalysts deposited from molecular complexes
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C2EE23862D
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Amount: $450,000.00
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Amount: $4,889,410.00
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View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE150100049
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