ORCID Profile
0000-0001-9368-2538
Current Organisations
University of Leeds
,
University of Western Australia
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Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8RE00211H
Abstract: A continuous-flow platform enables rapid kinetic profiling and accelerated production of block copolymer nano-objects via RAFT aqueous dispersion polymerization.
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1NR10337G
Abstract: Prussian Blue (PB) analogue metal coordination nanocages comprised of mesoporous walls (ca. 3.5 nm pore width) encapsulating a cavity approaching ca. 100 nm in diameter (surfactant free) are presented as an advance in rational metal coordination polymer nanostructure design. The synthesis employs lanthanide ions (Gd(3+) or Er(3+)) which function initially as peripheral coordination crosslinkers of metallo-surfactant templated miniemulsion droplets, and, subsequently, as promoters in the removal of the organic component of those surfactants via metal-assisted ester hydrolysis. The success of this synthetic strategy relies entirely on the periphery coordination event occurring prior to the ester hydrolysis surfactant removal step. Crucially, this one-pot sequential synthesis was achieved using a newly developed metallo-surfactant designed to have a reduced ester hydrolysis rate. Syntheses of this innovative metallo-surfactant, intermediary PB analogue coordination polymer organo-nanoshells and the subsequent conversion to hollow metal coordination nanocages are fully characterised using a wide variety of techniques, including TEM, SEM, EFTEM, EDX, TGA, WAXD, NMR, N(2) adsorption, etc., and represent the first designed synthesis of hollow metal coordination nanocages containing a large nanoscale cavity (wall of hollow nanosphere is mesoporous hence nanocage).
Publisher: Wiley
Date: 24-10-2023
Publisher: American Scientific Publishers
Date: 12-2012
Abstract: Graphite nanoplatelets were produced by sonication of thermally reduced graphite oxide produced from three precursor graphites. The thicknesses of the resulting graphite nanoplatlets were measured by X-ray diffraction and transmission electron microscopy. The type and size of the precursor graphite plays an important role in the final graphite nanoplatelet quality. The thinnest graphite nanoplatelets (average thickness of 4-7 nm) were obtained from Sri Lankan powdered graphite (average particle size of 0.1-0.2 mm). Thicker graphite nanoplatelets (average thickness of 30-60 nm), were obtained from a Canadian graphite (with an average flake size of 0.5-2 mm). Graphite nanoplatelets obtained by acid intercalation of Sri Lankan graphite were much thicker (an average thickness of 150 nm). Graphite nanoplatelet/epoxy composites containing 4 wt.% graphite nanoplatelets derived from Canadian or Sri Lankan natural graphite have electrical conductivities significantly above the percolation conductivity threshold. In contrast, corresponding composites, produced with (4 wt.%) commercial graphite nanoplatelets, either as-received or re-exfoliated, were electrically insulating. This behaviour is attributed to the highly wrinkled morphology, folded edges and abundant surface functional groups of the commercial graphite nanoplatelets. Thermal reduction of graphite oxide produced from natural flake graphite is therefore a promising route for producing graphite nanoplatelets fillers for electrically-conducting polymer composites.
Publisher: American Chemical Society (ACS)
Date: 18-03-2008
DOI: 10.1021/JP8009113
Publisher: IOP Publishing
Date: 07-2010
Publisher: Springer Science and Business Media LLC
Date: 22-03-2019
DOI: 10.1038/S42004-019-0138-Z
Abstract: Indium phosphide based quantum dots have emerged in recent years as alternatives to traditional heavy metal (cadmium, lead) based materials suitable for biomedical application due to their non-toxic nature. The major barrier to this application, is their low photoluminescent quantum yield in aqueous environments (typically 5%). Here we present a synthetic method for InP/ZnS quantum dots, utilizing a controlled cooling step for equilibration of zinc sulfide across the core, resulting in a photoluminescent quantum yield as high as 85% in organic solvent and 57% in aqueous media. To the best of our knowledge, this is the highest reported for indium phosphide quantum dots. DFT calculations reveal the enhancement in quantum yield is achieved by redistribution of zinc sulfide across the indium phosphide core through thermal diffusion. By eliminating the need for a glove box and relying on Schlenk line techniques, we introduce a widely accessible method for quantum dots with a realistic potential for improved biomedical applications.
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B9NJ00626E
Publisher: Research Square Platform LLC
Date: 04-01-2023
DOI: 10.21203/RS.3.RS-1020270/V1
Abstract: Periodontal disease is a significant burden for oral health, causing progressive and irreversible damage to the support structure of the tooth. This complex structure, the periodontium, is composed of interconnected soft and mineralised tissues, posing a challenge for regenerative approaches. Materials combining silicon and lithium are widely studied in periodontal regeneration, as they stimulate bone repair via silicic acid release while providing regenerative stimuli through lithium activation of the Wnt/β-catenin pathway. Yet, existing materials for combined lithium and silicon release have limited control over ion release amounts and kinetics. Porous silicon can provide controlled silicic acid release, inducing osteogenesis to support bone regeneration. Prelithiation, a strategy developed for battery technology, can introduce large, controllable amounts of lithium within porous silicon, but yields a highly reactive material, unsuitable for biomedicine. This work debuts a strategy to lithiate porous silicon nanowires (LipSiNs) which generates a biocompatible and bioresorbable material. LipSiNs incorporate lithium to between 1% and 40% of silicon content, releasing lithium and silicic acid in a tailorable fashion from days to weeks. LipSiNs combine osteogenic, cementogenic and Wnt/β-catenin stimuli to regenerate bone, cementum and periodontal ligament fibres in a murine periodontal defect.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1EN00384D
Abstract: Arsenic slows the structural ordering and transformation of As-bearing green rust formed from ferrihydrite under anoxic and circum-neutral pH conditions.
Publisher: Springer Science and Business Media LLC
Date: 09-11-2020
Publisher: Oxford University Press (OUP)
Date: 08-2014
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3RA43846E
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 17-11-2010
Publisher: Springer Science and Business Media LLC
Date: 16-11-2015
DOI: 10.1038/NMAT4478
Abstract: The chemical functionality within porous architectures dictates their performance as heterogeneous catalysts however, synthetic routes to control the spatial distribution of in idual functions within porous solids are limited. Here we report the fabrication of spatially orthogonal bifunctional porous catalysts, through the stepwise template removal and chemical functionalization of an interconnected silica framework. Selective removal of polystyrene nanosphere templates from a lyotropic liquid crystal-templated silica sol-gel matrix, followed by extraction of the liquid crystal template, affords a hierarchical macroporous-mesoporous architecture. Decoupling of the in idual template extractions allows independent functionalization of macropore and mesopore networks on the basis of chemical and/or size specificity. Spatial compartmentalization of, and directed molecular transport between, chemical functionalities affords control over the reaction sequence in catalytic cascades herein illustrated by the Pd/Pt-catalysed oxidation of cinnamyl alcohol to cinnamic acid. We anticipate that our methodology will prompt further design of multifunctional materials comprising spatially compartmentalized functions.
Publisher: American Society for Microbiology
Date: 15-11-2019
DOI: 10.1128/AEM.01379-19
Abstract: Aerobic methane-oxidizing bacteria are ubiquitous in the environment. Two well-characterized strains, Mc . capsulatus (Bath) and Methylosinus trichosporium OB3b, representing gamma- and alphaproteobacterial methanotrophs, respectively, can convert selenite, an environmental pollutant, to volatile selenium compounds and selenium-containing particulates. Both conversions can be harnessed for the bioremediation of selenium pollution using biological or fossil methane as the feedstock, and these organisms could be used to produce selenium-containing particles for food and biotechnological applications. Using an extensive suite of techniques, we identified precursors of selenium nanoparticle formation and also found that these nanoparticles are made up of eight-membered mixed selenium and sulfur rings.
Publisher: American Chemical Society (ACS)
Date: 09-05-2011
DOI: 10.1021/CS200145N
Publisher: Springer Science and Business Media LLC
Date: 23-06-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C002594A
Abstract: Direct microwave synthesis between solids is limited by the restricted number of materials that exhibit microwave heating at room temperature. The dielectric properties of most materials dictate that microwave heating can occur at higher temperatures, primarily due to increasing conduction losses. Microwave-induced plasma promoted microwave heating circumvents the requirement for room temperature microwave heating allowing microwave methods to be applied to a greater range of materials. For ex le, MgO heats to >1700 degrees C using an O(2) plasma and 900 W magnetron power. Here we demonstrate that in situ temperature measurements can be used to identify binary oxides that exhibit significant plasma promoted heating. Furthermore, reactions to form ternary oxides can be monitored to determine if reactions are driven by the dielectric properties of the precursor(s) or product.
Publisher: IOP Publishing
Date: 12-10-2015
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.MICRON.2019.02.002
Abstract: Analytical transmission electron microscopy (TEM) is often used to investigate morphologies, crystal structures, chemical compositions and oxidation states of highly reactive mixed-valent mineral phases. Of prime interest, due to its potential role in toxic metal remediation, is green rust sulphate (GR
Publisher: Wiley
Date: 26-07-2011
Publisher: Springer Science and Business Media LLC
Date: 19-02-2018
DOI: 10.1557/ADV.2018.197
Publisher: American Society for Microbiology
Date: 07-2016
DOI: 10.1128/AEM.00508-16
Abstract: Using microorganisms to remove waste and/or neutralize pollutants from contaminated water is attracting much attention due to the environmentally friendly nature of this methodology. However, cell recovery remains a bottleneck and a considerable challenge for the development of this process. Magnetotactic bacteria are a unique group of organisms that can be manipulated by an external magnetic field due to the presence of biogenic magnetite crystals formed within their cells. In this study, we demonstrated an account of accumulation and precipitation of amorphous elemental selenium nanoparticles within magnetotactic bacteria alongside and independent of magnetite crystal biomineralization when grown in a medium containing selenium oxyanion (SeO 3 2− ). Quantitative analysis shows that magnetotactic bacteria accumulate the largest amount of target molecules (Se) per cell compared with any other previously reported nonferrous metal/metalloid. For ex le, 2.4 and 174 times more Se is accumulated than Te taken up into cells and Cd 2+ adsorbed onto the cell surface, respectively. Crucially, the bacteria with high levels of Se accumulation were successfully recovered with an external magnetic field. The biomagnetic recovery and the effective accumulation of target elements demonstrate the potential for application in bioremediation of polluted water. IMPORTANCE The development of a technique for effective environmental water remediation is urgently required across the globe. A biological remediation process of waste removal and/or neutralization of pollutant from contaminated water using microorganisms has great potential, but cell recovery remains a bottleneck. Magnetotactic bacteria synthesize magnetic particles within their cells, which can be recovered by a magnetic field. Herein, we report an ex le of accumulation and precipitation of amorphous elemental selenium nanoparticles within magnetotactic bacteria independent of magnetic particle synthesis. The cells were able to accumulate the largest amount of Se compared to other foreign elements. More importantly, the Se-accumulating bacteria were successfully recovered with an external magnetic field. We believe magnetotactic bacteria confer unique advantages of biomagnetic cell recovery and of Se accumulation, providing a new and effective methodology for bioremediation of polluted water.
Publisher: Springer Science and Business Media LLC
Date: 12-2015
Publisher: American Chemical Society (ACS)
Date: 12-03-2014
DOI: 10.1021/TX4004243
Abstract: ZnO nanoparticles (NPs) are prone to dissolution, and uncertainty remains whether biological/cellular responses to ZnO NPs are solely due to the release of Zn(2+) or whether the NPs themselves have additional toxic effects. We address this by establishing ZnO NP solubility in dispersion media (Dulbecco's modified Eagle's medium, DMEM) held under conditions identical to those employed for cell culture (37 °C, 5% CO2, and pH 7.68) and by systematic comparison of cell-NP interaction for three different ZnO NP preparations. For NPs at concentrations up to 5.5 μg ZnO/mL, dissolution is complete (with the majority of the soluble zinc complexed to dissolved ligands in the medium), taking ca. 1 h for uncoated and ca. 6 h for polymer coated ones. Above 5.5 μg/mL, the results are consistent with the formation of zinc carbonate, keeping the solubilized zinc fixed to 67 μM of which only 0.45 μM is as free Zn(2+), i.e., not complexed to dissolved ligands. At these relatively high concentrations, NPs with an aliphatic polyether-coating show slower dissolution (i.e., slower free Zn(2+) release) and reprecipitation kinetics compared to those of uncoated NPs, requiring more than 48 h to reach thermodynamic equilibrium. Cytotoxicity (MTT) and DNA damage (Comet) assay dose-response curves for three epithelial cell lines suggest that dissolution and reprecipitation dominate for uncoated ZnO NPs. Transmission electron microscopy combined with the monitoring of intracellular Zn(2+) concentrations and ZnO-NP interactions with model lipid membranes indicate that an aliphatic polyether coat on ZnO NPs increases cellular uptake, enhancing toxicity by enabling intracellular dissolution and release of Zn(2+). Similarly, we demonstrate that needle-like NP morphologies enhance toxicity by apparently frustrating cellular uptake. To limit toxicity, ZnO NPs with nonacicular morphologies and coatings that only weakly interact with cellular membranes are recommended.
Publisher: Oxford University Press (OUP)
Date: 14-08-2015
Publisher: IOP Publishing
Date: 10-06-2013
Publisher: IOP Publishing
Date: 02-07-2012
Publisher: IOP Publishing
Date: 02-07-2012
Publisher: Wiley
Date: 06-08-2015
DOI: 10.1111/JMI.12290
Abstract: We present a critical review of the common methods for determining the dispersion state of nanoparticulate s les particularly in liquid media, including the determination of particle size and morphology particle size distributions and polydispersity and equilibrium particle structure and chemistry. We highlight the potential contributions of both scanning probe and electron microscopies in this analysis which is of benefit in understanding nanoparticulate formulations and their behaviour applied across a very wide range of technologies and industry sectors.
Publisher: Elsevier BV
Date: 03-2014
DOI: 10.1016/J.JCIS.2013.11.064
Abstract: Preformed iron oxide nanoparticles have been successfully assembled onto alumina and MCM-41 support materials. The particles are found to disperse evenly over the surface of the silicate however, in the case of the alumina we find that in addition to areas of even distribution there is also some clustering of the particles. The materials are stable under heat treatment, with no signs of further aggregation during calcination. We investigate the reducibility of the materials through H2-TPR studies and we find that the particles are reducible around 500-550°C. The reduction process is complete at temperatures where MCM-41 can undergo degradation, supporting that the alumina based materials are more suited to the multiple base oxidation reduction steps in the catalytic cycle.
Publisher: Elsevier BV
Date: 02-2020
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.MICRON.2019.01.013
Abstract: In situ characterisation of nanoparticle dispersion and surface coatings is required to further our understanding of the behaviour of nanoparticles in aqueous suspension. Using cryogenic transmission electron microscopy (cryo-TEM) it is possible to analyse a nanoparticle suspension in the frozen, hydrated state however, this analysis is often limited to imaging alone. This work demonstrates the first use of analytical scanning TEM (STEM) in the examination of nanoparticles captured in a layer of vitreous ice. Imaging and analysis of frozen hydrated suspensions by both STEM energy dispersive X-ray (EDX) spectroscopy and electron energy loss spectroscopy (EELS) under cryogenic conditions demonstrates the identification and separation of CeO
Publisher: Informa UK Limited
Date: 24-12-2018
Publisher: Springer Science and Business Media LLC
Date: 26-10-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2JM31520C
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.MICRON.2019.01.014
Abstract: In the pharmaceutical industry, it is important to determine the effects of crystallisation and processes, such as milling, on the generation of crystalline defects in formulated products. Conventional transmission electron microscopy and scanning transmission electron microscopy (STEM) can be used to obtain information on length scales unobtainable by other techniques, however, organic crystals are extremely susceptible to electron beam damage. This work demonstrates a bright field (BF) STEM method that can increase the information content per unit specimen damage by the use of scanning moiré fringes (SMFs). SMF imaging essentially provides a magnification of the crystal lattice through the interference between closely aligned lattice fringes and a scanning lattice of similar spacing. The generation of SMFs is shown for three different organic crystals with varying electron beam sensitivity, theophylline, furosemide and felodipine. The electron fluence used to acquire the BF-STEM for the most sensitive material, felodipine was approximately 3.5 e
Publisher: Elsevier BV
Date: 06-2014
Publisher: IOP Publishing
Date: 12-10-2015
Publisher: Springer Science and Business Media LLC
Date: 23-06-2012
Publisher: Informa UK Limited
Date: 20-01-2012
DOI: 10.3109/17435390.2011.647928
Abstract: Single-walled carbon nanotubes (SWCNTs) have recently attracted great attention because of their fibrous structure and high aspect ratio. Here the genotoxic potential of 400-800 nm, 1-3 μm and 5-30 μm SWCNT with respect to their geometry and surface characteristics was studied. Following thorough physico-chemical characterisation, human bronchial epithelial (BEAS-2B) and lymphoblastoid (MCL-5) cells were treated with SWCNT for 24 or 48 h. This showed significant increases in micronucleus frequency in a time- and dose-dependent manner in both cell types in the absence of cytotoxicity. Over the same dose range, only 1-3 μm SWCNT gave rise to significant increases in hprt point mutations at doses ≥25 μg/ml. Cellular 2,7-dichlorodihydrofluoresceindiacetate (DCFH-DA) fluorescence assay and RT-PCR for oxidative pathway gene profiling revealed a possible oxidative mechanism for the genotoxicity observed in the 1-3 μm SWCNT. Consequently, this study has demonstrated that SWCNT genotoxicity is dependent on its secondary structure under experimental conditions and oxidative stress alone cannot account for the observed damage.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2DT12269C
Abstract: Lanthanide zirconate phases Ln(2)Zr(2)O(7) and Ln(4)Zr(3)O(12) (Ln = Y, La, Gd, Dy, Ho, Yb) have been prepared using a microwave induced plasma methodology, which allows rapid synthesis using materials which do not couple directly with microwaves at room temperature. We describe the measurement of heating profiles of the precursor binary metal oxides which can be used to identify conditions conducive to the synthesis of more complex oxides. Uncontrolled heating which can be a feature of microwave synthesis of ceramics is not observed, allowing reproducible synthesis. Conventionally these phases are prepared at >1400 °C over hours or days and are being investigated for applications including the immobilisation of nuclear waste where rapid processing is important. Using the microwave plasma method, phase-pure materials have been prepared in minutes. Furthermore, it is clear that Ln(2)Zr(2)O(7) and Ln(4)Zr(3)O(12) also exhibit significant plasma-promoted dielectric heating (e.g. >2200 °C for Dy(4)Zr(3)O(12)) which is typically greater than either of the respective precursors, thus providing a driving force to rapidly complete the reaction.
Publisher: IOP Publishing
Date: 23-03-2015
DOI: 10.1088/0957-4484/26/15/155101
Abstract: The application of nanoparticles (NPs) within medicine is of great interest their innate physicochemical characteristics provide the potential to enhance current technology, diagnostics and therapeutics. Recently a number of NP-based diagnostic and therapeutic agents have been developed for treatment of various diseases, where judicious surface functionalization is exploited to increase efficacy of administered therapeutic dose. However, quantification of heterogeneity associated with absolute dose of a nanotherapeutic (NP number), how this is trafficked across biological barriers has proven difficult to achieve. The main issue being the quantitative assessment of NP number at the spatial scale of the in idual NP, data which is essential for the continued growth and development of the next generation of nanotherapeutics. Recent advances in s le preparation and the imaging fidelity of transmission electron microscopy (TEM) platforms provide information at the required spatial scale, where in idual NPs can be in idually identified. High spatial resolution however reduces the s le frequency and as a result dynamic biological features or processes become opaque. However, the combination of TEM data with appropriate probabilistic models provide a means to extract biophysical information that imaging alone cannot. Previously, we demonstrated that limited cell s ling via TEM can be statistically coupled to large population flow cytometry measurements to quantify exact NP dose. Here we extended this concept to link TEM measurements of NP agglomerates in cell culture media to that encapsulated within vesicles in human osteosarcoma cells. By construction and validation of a data-driven transfer function, we are able to investigate the dynamic properties of NP agglomeration through endocytosis. In particular, we statistically predict how NP agglomerates may traverse a biological barrier, detailing inter-agglomerate merging events providing the basis for predictive modelling of nanopharmacology.
Publisher: Elsevier
Date: 2013
Publisher: Wiley
Date: 09-04-2012
DOI: 10.1002/APP.36655
Publisher: Elsevier BV
Date: 05-2008
Publisher: American Chemical Society (ACS)
Date: 07-12-2010
DOI: 10.1021/JP108974S
Publisher: Elsevier BV
Date: 2021
Publisher: Springer Science and Business Media LLC
Date: 24-03-2015
DOI: 10.1038/SREP09425
Abstract: Chemoselectivity is a cornerstone of catalysis, permitting the targeted modification of specific functional groups within complex starting materials. Here we elucidate key structural and electronic factors controlling the liquid phase hydrogenation of cinnamaldehyde and related benzylic aldehydes over Pt nanoparticles. Mechanistic insight from kinetic mapping reveals cinnamaldehyde hydrogenation is structure-insensitive over metallic platinum, proceeding with a common Turnover Frequency independent of precursor, particle size or support architecture. In contrast, selectivity to the desired cinnamyl alcohol product is highly structure sensitive, with large nanoparticles and high hydrogen pressures favoring C = O over C = C hydrogenation, attributed to molecular surface crowding and suppression of sterically-demanding adsorption modes. In situ vibrational spectroscopies highlight the role of support polarity in enhancing C = O hydrogenation (through cinnamaldehyde reorientation), a general phenomenon extending to alkyl-substituted benzaldehydes. Tuning nanoparticle size and support polarity affords a flexible means to control the chemoselective hydrogenation of aromatic aldehydes.
Publisher: American Chemical Society (ACS)
Date: 11-2017
Abstract: Understanding the delivered cellular dose of nanoparticles is imperative in nanomedicine and nanosafety, yet is known to be extremely complex because of multiple interactions between nanoparticles, their environment, and the cells. Here, we use 3-D reconstruction of agglomerates preserved by cryogenic snapshot s ling and imaged by electron microscopy to quantify the "bioavailable dose" that is presented at the cell surface and formed by the process of in idual nanoparticle sequestration into agglomerates in the exposure media. Critically, using 20 and 40 nm carboxylated polystyrene-latex and 16 and 85 nm silicon dioxide nanoparticles, we show that abrupt, dose-dependent "tipping points" in agglomeration state can arise, subsequently affecting cellular delivery and increasing toxicity. These changes are triggered by shifts in the ratio of the total nanoparticle surface area to biomolecule abundance, with the switch to a highly agglomerated state effectively changing the test article midassay, challenging the dose-response paradigm for nanosafety experiments. By characterizing nanoparticle numbers per agglomerate, we show these tipping points can lead to the formation of extreme agglomeration states whereby 90% of an administered dose is contained and delivered to the cells by just the top 2% of the largest agglomerates. We thus demonstrate precise definition, description, and comparison of the nanoparticle dose formed in different experimental environments and show that this description is critical to understanding cellular delivery and toxicity. We further empirically "stress-test" the commonly used dynamic light scattering approach, establishing its limitations to present an analysis strategy that significantly improves the usefulness of this popular nanoparticle characterization technique.
Publisher: MDPI AG
Date: 31-08-2020
DOI: 10.3390/CHEMOSENSORS8030080
Abstract: Thiols and selenides bind to the surface of gold nanoparticles (AuNPs) and thus provide suitable platforms for the fabrication of sensors. However, the co-existence of adsorbed citrate on the surface of the nanoparticles can influence their functionalization behavior and potentially their sensing performance measured by the extent of particle aggregation. In this study, the functionalization of purchased (7.3 ± 1.2 nm) and in-house prepared AuNPs (13.8 ± 1.2 nm), under the same experimental conditions with either cysteamine (Cys), 3-mercaptopropionic acid (3-MPA), or l-selenocystine (SeCyst) was investigated. 1H-NMR measurements showed distinct citrate signatures on the in-house synthesized citrate-stabilized AuNPs, while no citrate signals were detected on the purchased AuNPs other than evidence of the presence of α-ketoglutaric acid. Carboxylate-containing species attributed to either citrate or α-ketoglutaric acid were identified in all functionalized AuNPs. ATR-FTIR spectroscopy confirmed the functionalization of AuNPs with Cys and 3-MPA, and energy dispersive X-ray (EDX) spectroscopy measurements suggested the formation of SeCyst functionalized AuNPs. Co-adsorption rather than displacement by the functionalizing agents and carboxylate-containing molecules was indicated, which for Cys and SeCyst functionalized AuNPs was also the aggregation limiting factor. In contrast, the behavior of 3-MPA functionalized AuNPs could be attributed to electrostatic repulsions between the functionalized groups.
Publisher: American Chemical Society (ACS)
Date: 19-08-2013
DOI: 10.1021/CS400371A
Publisher: IOP Publishing
Date: 09-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6NR03269A
Abstract: We report observation of highly-segregated compositional domains within CuInS 2 quantum dots, showing the origin of their emission-mediating In Cu defect.
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.JCIS.2019.04.009
Abstract: This paper investigates the characterisation of alumina-doped titania nanoparticles, milled under high-shear over time, in the presence of sodium hexametaphosphate (SHMP) dispersant. Transmission electron microscopy (TEM) indicated that prolonged milling times led to the formation of 10 nm particle fines which were electrostatically attracted to larger particles, where no change in the crystal structure was observed. Primary particle sizes measured by dynamic light scattering (DLS) and TEM were in agreement and showed no change in primary particle size (∼250 nm) with respect to milling time, however, there was a clear reduction in the magnitude of the slow mode decay associated to aggregates. The TiO
Publisher: American Chemical Society (ACS)
Date: 25-06-2013
DOI: 10.1021/NN4019619
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3NR00184A
Abstract: The selective aerobic oxidation of cinnamyl alcohol over Pt nanoparticles has been tuned via the use of mesoporous silica supports to control their dispersion and oxidation state. High area two-dimensional SBA-15, and three-dimensional, interconnected KIT-6 silica significantly enhance Pt dispersion, and thus surface PtO2 concentration, over that achievable via commercial low surface area silica. Selective oxidation activity scales with Pt dispersion in the order KIT-6 ≥ SBA-15 > SiO2, evidencing surface PtO2 as the active site for cinnamyl alcohol selox to cinnamaldehyde. Kinetic mapping has quantified key reaction pathways, and the importance of high O2 partial pressures for cinnamaldehyde production.
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0CC00003E
Abstract: Metal coordination polymer nanoboxes are reported for the first time. Initially spherical miniemulsion droplet templates were transformed to hollow cubic crystalline nanostructures via a miniemulsion periphery polymerization conducted under benign thermal and chemical conditions.
Publisher: Elsevier BV
Date: 11-2011
Publisher: Informa UK Limited
Date: 19-11-2010
DOI: 10.3109/17435390.2010.535622
Abstract: The addition of a transmitted electron detector to a scanning electron microscope (SEM) allows the recording of bright and dark field scanning transmission electron microscope (STEM) images and the corresponding in-lens secondary electron images from the same region of a thin s le. These combined imaging techniques have been applied here to the analysis of ultrathin sections of cells exposed in vitro to nanomaterials for toxicology investigation. Electron microscopy in general permits the exact nature of the interaction of nanomaterials and cells to be elucidated, and in addition the use of STEM mode in the SEM enables the easy identification and exclusion of artefacts produced by ultramicrotome sectioning. The imaging and analysis obtained by using the STEM mode in the SEM configuration from three different nanomaterial systems of importance (iron oxide nanoparticles, single-walled carbon nanotubes and cadmium selenide quantum dots) indicate that it is a simple, practical and cost-effective tool for nanotoxicological research.
Publisher: American Chemical Society (ACS)
Date: 13-09-2018
DOI: 10.1021/ACS.MOLPHARMACEUT.8B00693
Abstract: During drug development control of polymorphism, particle properties and impurities are critical for ensuring a good quality, reproducible, and safe medicine. A wide variety of analytical techniques are employed in demonstrating the regulators control over the drug substance and product manufacturing, storage, and supply. Transmission electron microscopy (TEM) offers the opportunity to analyze in detail pharmaceutical systems at a length scale and limit of detection not readily achieved by many traditional techniques. However, the use of TEM as a characterization tool for drug development is uncommon due to possible damage caused by the electron beam. This work outlines the development of a model, using molecular descriptors, to predict the electron beam stability of active pharmaceutical ingredients (API). For a given set of conditions and a particular imaging or analytical mode, the total number of electrons per unit area, which causes observable damage to a s le in the TEM, can be defined as the critical fluence ( C
Publisher: Elsevier BV
Date: 05-2021
Publisher: MDPI AG
Date: 22-08-2019
DOI: 10.3390/MIN9090503
Abstract: The controlled crystallisation of struvite (MgNH4PO4∙6H2O) is a viable means for the recovery and recycling of phosphorus (P) from municipal and industrial wastewaters. However, an efficient implementation of this recovery method in water treatment systems requires a fundamental understanding of struvite crystallisation mechanisms, including the behavior and effect of metal contaminants during struvite precipitation. Here, we studied the crystallisation pathways of struvite from aqueous solutions using a combination of ex situ and in situ time-resolved synthesis and characterization techniques, including synchrotron-based small- and wide-angle X-ray scattering (SAXS/WAXS) and cryogenic transmission electron microscopy (cryo-TEM). Struvite syntheses were performed both in the pure Mg-NH4-PO4 system as well as in the presence of cobalt (Co), which, among other metals, is typically present in waste streams targeted for P-recovery. Our results show that in the pure system and at Co concentrations 0.5 mM, struvite crystals nucleate and grow directly from solution, much in accordance with the classical notion of crystal formation. In contrast, at Co concentrations ≥ 1 mM, crystallisation was preceded by the transient formation of an amorphous nanoparticulate phosphate phase. Depending on the aqueous Co/P ratio, this amorphous precursor was found to transform into either (i) Co-bearing struvite (at Co/P 0.3) or (ii) cobalt phosphate octahydrate (at Co/P 0.3). These amorphous-to-crystalline transformations were accompanied by a marked colour change from blue to pink, indicating a change in Co2+ coordination in the formed solid from tetrahedral to octahedral. Our findings have implications for the recovery of nutrients and metals during struvite crystallisation and contribute to the ongoing general discussion about the mechanisms of crystal formation.
Publisher: IEEE
Date: 07-2017
Publisher: IOP Publishing
Date: 12-10-2015
Publisher: Elsevier BV
Date: 03-2012
Publisher: IOP Publishing
Date: 12-10-2015
Publisher: Springer Science and Business Media LLC
Date: 16-09-2023
Publisher: Elsevier BV
Date: 10-2011
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2EE21779A
Publisher: The Royal Society of Chemistry
Date: 24-08-2015
DOI: 10.1039/9781782621867-00108
Abstract: This chapter discusses the use of analytical transmission electron microscopy (TEM) to study the chemistry of materials at the nanoscale. Analytical TEM involves utilising the signals generated when a focused electron beam excites small volumes of material in a thin specimen. The most common analytical signals employed are emitted X-rays and direct energy losses induced in the transmitted primary electrons. These are measured using the spectroscopic techniques of energy dispersive X-ray analysis (EDX) and electron energy loss spectroscopy (EELS). Both EDX and EELS can be performed in a variety of modes, including the collection of in idual spectra from a particular point of interest, or the mapping of the distribution of different elements over a specified area of the s le. Further to this, spectra from both techniques can be used to quantitatively assess concentration values for in idual elements, and in the case of EELS, be used to determine additional information on bonding and the oxidation state of certain elements. The capabilities of both techniques are explained using material ex les, so that the reader can identify and employ the best analysis procedure to extract the most appropriate information from their s le.
Publisher: Wiley
Date: 21-02-2011
Publisher: Springer Science and Business Media LLC
Date: 14-09-2014
DOI: 10.1038/NMETH.3105
Abstract: For phenotypic behavior to be understood in the context of cell lineage and local environment, properties of in idual cells must be measured relative to population-wide traits. However, the inability to accurately identify, track and measure thousands of single cells via high-throughput microscopy has impeded dynamic studies of cell populations. We demonstrate unique labeling of cells, driven by the heterogeneous random uptake of fluorescent nanoparticles of different emission colors. By sequentially exposing a cell population to different particles, we generated a large number of unique digital codes, which corresponded to the cell-specific number of nanoparticle-loaded vesicles and were visible within a given fluorescence channel. When three colors are used, the assay can self-generate over 17,000 in idual codes identifiable using a typical fluorescence microscope. The color-codes provided immediate visualization of cell identity and allowed us to track human cells with a success rate of 78% across image frames separated by 8 h.
Publisher: Wiley
Date: 17-09-2012
Publisher: IOP Publishing
Date: 11-06-2014
Publisher: Springer Science and Business Media LLC
Date: 23-07-2012
Abstract: Mechanisms for cellular uptake of nanoparticles have important implications for nanoparticulate drug delivery and toxicity. We have explored the mechanism of uptake of amorphous silica nanoparticles of 14 nm diameter, which agglomerate in culture medium to hydrodynamic diameters around 500 nm. In HT29, HaCat and A549 cells, cytotoxicity was observed at nanoparticle concentrations ≥ 1 μg/ml, but DNA damage was evident at 0.1 μg/ml and above. Transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy confirmed entry of the silica particles into A549 cells exposed to 10 μg/ml of nanoparticles. The particles were observed in the cytoplasm but not within membrane bound vesicles or in the nucleus. TEM of cells exposed to nanoparticles at 4°C for 30 minutes showed particles enter cells when activity is low, suggesting a passive mode of entry. Plasma lipid membrane models identified physical interactions between the membrane and the silica NPs. Quartz crystal microbalance experiments on tethered bilayer lipid membrane systems show that the nanoparticles strongly bind to lipid membranes, forming an adherent monolayer on the membrane. Leakage assays on large unilamellar vesicles (400 nm diameter) indicate that binding of the silica NPs transiently disrupts the vesicles which rapidly self-seal. We suggest that an adhesive interaction between silica nanoparticles and lipid membranes could cause passive cellular uptake of the particles.
Publisher: Elsevier BV
Date: 06-2023
Publisher: Elsevier BV
Date: 10-2014
Publisher: Elsevier BV
Date: 06-2017
DOI: 10.1016/J.MSEC.2017.02.116
Abstract: Tooth hypersensitivity is a growing problem affecting both the young and ageing population worldwide. Since an effective and permanent solution is not yet available, we propose a new methodology for the restoration of dental enamel using femtosecond lasers and novel calcium phosphate biomaterials. During this procedure the irradiated mineral transforms into a densified layer of acid resistant iron doped β-pyrophosphate, bonded with the surface of eroded enamel. Our aim therefore is to evaluate this densified mineral as a potential replacement material for dental hard tissue. To this end, we have tested the hardness of β-pyrophosphate pellets (sintered at 1000°C) and its mineral precursor (brushite), the wear rate during simulated tooth-brushing trials and the cytocompatibility of these minerals in powder form. It was found that the hardness of the β-pyrophosphate pellets is comparable with that of dental enamel and significantly higher than dentine while, the brushing trials prove that the wear rate of β-pyrophosphate is much slower than that of natural enamel. Finally, cytotoxicity and genotoxicity tests suggest that iron doped β-pyrophosphate is cytocompatible and therefore could be used in dental applications. Taken together and with the previously reported results on laser irradiation of these materials we conclude that iron doped β-pyrophosphate may be a promising material for restoring acid eroded and worn enamel.
Publisher: IOP Publishing
Date: 11-06-2014
Publisher: Elsevier BV
Date: 07-2021
Publisher: Springer Science and Business Media LLC
Date: 13-02-2019
Publisher: Wiley
Date: 11-03-2015
DOI: 10.1111/JMI.12239
Abstract: Semiconductor quantum dot nanoparticles are in demand as optical biomarkers yet the cellular uptake process is not fully understood quantification of numbers and the fate of internalized particles are still to be achieved. We have focussed on the characterization of cellular uptake of quantum dots using a combination of analytical electron microscopies because of the spatial resolution available to examine uptake at the nanoparticle level, using both imaging to locate particles and spectroscopy to confirm identity. In this study, commercially available quantum dots, CdSe/ZnS core/shell particles coated in peptides to target cellular uptake by endocytosis, have been investigated in terms of the agglomeration state in typical cell culture media, the traverse of particle agglomerates across U-2 OS cell membranes during endocytosis, the merging of endosomal vesicles during incubation of cells and in the correlation of imaging flow cytometry and transmission electron microscopy to measure the final nanoparticle dose internalized by the U-2 OS cells. We show that a combination of analytical transmission electron microscopy and serial block face scanning electron microscopy can provide a comprehensive description of the internalization of an initial exposure dose of nanoparticles by an endocytically active cell population and how the internalized, membrane bound nanoparticle load is processed by the cells. We present a stochastic model of an endosome merging process and show that this provides a data-driven modelling framework for the prediction of cellular uptake of engineered nanoparticles in general.
Publisher: Oxford University Press (OUP)
Date: 19-01-2015
Publisher: IOP Publishing
Date: 02-07-2012
Publisher: American Chemical Society (ACS)
Date: 17-08-2017
DOI: 10.1021/JACS.7B05104
Publisher: Elsevier BV
Date: 2014
Publisher: IOP Publishing
Date: 11-06-2014
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2018
End Date: 2021
Funder: Biotechnology and Biological Sciences Research Council
View Funded ActivityStart Date: 2016
End Date: 2020
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2018
End Date: 2020
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2018
End Date: 2020
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2018
End Date: 2020
Funder: Engineering and Physical Sciences Research Council
View Funded Activity