ORCID Profile
0000-0003-3428-1501
Current Organisations
Aarhus Universitet
,
University of Wollongong
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Publisher: Wiley
Date: 19-01-2012
Publisher: IOP Publishing
Date: 03-04-2019
Abstract: Reliable and scalable sterilisation of hydrogels is critical to the clinical translation of many biofabrication approaches, such as extrusion-based 3D bioprinting of cell-laden bio-inks. However sterilisation methods can be destructive, and may have detrimental effects on the naturally-derived hydrogels that constitute much of the bio-ink palette. Determining effective sterilisation methods requires detailed analysis of the effects of sterilisation on relevant properties such as viscosity, printability and cytocompatibility. Yet there have been no studies specifically exploring the effects of sterilisation on bio-inks to date. In this work, we explored the effects of various sterilisation techniques on four of the most widely used bio-ink components: gelatin, gelatin methacryloyl, hyaluronic acid, and hyaluronic acid methacrylate. Autoclaving was the most destructive sterilisation method, producing large reductions in viscosity and in mechanical properties following crosslinking. Filter sterilisation caused some reduction in rheological properties of GelMA due to removal of higher molecular weight components, but did not affect photocrosslinking. Ethylene oxide (EtO) was the least destructive sterilisation method in terms of rheological properties for all materials, had no detrimental effect on the photocrosslinkable methacrylate/methacrylamide groups, and so was chosen for more detailed examination. In biological analyses, we found that EtO treatment successfully eradicated a bacterial challenge of E. coli, caused no decrease in viability of human mesenchyman stem cells (hMSCs), and had no effect on their rate of proliferation. Finally, we found that EtO-treated hydrogels supported encapsulated hMSCs to differentiate towards the chondrogenic lineage, and to produce new cartilage matrix. Our results bring to light various effects that sterilisation can have on bio-inks, as well as highlighting EtO sterilisation as a method which minimises degradation of properties, while still promoting biological function.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6NR07516A
Publisher: Elsevier BV
Date: 11-2010
DOI: 10.1016/J.CHROMA.2010.09.069
Abstract: The preparation of processable graphene oxide colloids called chemically converted graphene (CCG) involves the following steps: oxidation of graphite to form graphite oxide exfoliation of graphite oxide to form graphene oxide (GO) and reduction of GO to form CCG. In this work, the exfoliation and reduction steps were monitored by capillary zone electrophoresis (CZE). CZE was performed in fused silica capillaries with UV absorbance at 230 nm (GO) and 270 nm (CCG) using 250 μM tetrapropylammonium hydroxide (pH 10.4). The results indicate that almost complete exfoliation of graphite oxide (0.05 wt%) and higher recovery of CCG were obtained by sonication at 50% power for more than 15 h. CZE is considered a valuable tool for the fractionation and analysis of GO nanoparticles and, hence, for the control of different steps in preparation of CCG.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8SM01227J
Abstract: Using ultrasound, we provide a simple and rapid contactless approach for the mechanical characterization of photocrosslinked hydrogels with swelling properties.
Publisher: American Chemical Society (ACS)
Date: 20-08-2012
DOI: 10.1021/JZ3008479
Abstract: Graphene oxide (GO) flakes dissolved in water can spontaneously form liquid crystals. Liquid crystallinity presents an opportunity to process graphene materials into macroscopic assemblies with long-range ordering, but most graphene electronic functionalities are lost in oxidation treatments. Reduction of GO allows recovering functionalities and makes reduced graphene oxide (RGO) of greater interest. Unfortunately, chemical reduction of GO generally results in the aggregation of the flakes, with no liquid crystallinity observed. We report in the present work liquid crystals made of RGO. The addition of surfactants in appropriate conditions is used to stabilize the RGO flakes against aggregation maintaining their ability to form water-based liquid crystals. Structural and thermodynamical studies allow the dimensions of the flakes to be deduced. It is found that the thickness and diameter of RGO flakes are close to that of neat GO flakes.
Publisher: Springer Science and Business Media LLC
Date: 06-2015
DOI: 10.1038/AM.2015.47
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4TB01636J
Abstract: Electrically conductive, mechanically improved graphene/chitosan/lactic acid composites were synthesised and could be easily processed into multi-layer scaffolds using additive fabrication techniques.
Publisher: IOP Publishing
Date: 23-03-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6RA15190F
Abstract: A hybrid electrically conductive polyester–graphene textile was fabricated as a high-performance smart textile for geotextile and/or heating element applications.
Publisher: Elsevier BV
Date: 10-2011
Publisher: Wiley
Date: 29-08-2013
Abstract: Different nanocarbons, that is, single-wall carbon nanotubes, graphene, single-wall carbon nanohorns (SWCNHs), and their respective oxidized analogs have been used to fabricate novel doped TiO2 electrodes for DSSCs. Our results indicate that all of the nanocarbons significantly enhance the device characteristics when compared to standard TiO2 electrodes. Overall, our most outstanding finding is that SWCNH derivatives are also a plausible material for developing highly-efficient DSSCs.
Publisher: Elsevier BV
Date: 09-2013
Publisher: CRC Press
Date: 27-03-2017
Publisher: Inderscience Publishers
Date: 2008
Publisher: Elsevier BV
Date: 12-2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8EE03403F
Abstract: A 3D iron porphyrin/graphene hydrogel electrocatalyst affords highly efficient, durable and selective CO 2 reduction to CO at a low overpotential.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7SM02187A
Abstract: Strategies for controlling the properties of gelatin methacryloyl hydrogels are elucidated, with applications for biofabrication and tissue engineering.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8RA01384E
Abstract: Yarn type asymmetric supercapacitor with high weight ratio of rGO in anode for wearable electronics.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3TB00463E
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4TA04367G
Abstract: Simultaneously oxidizing and ultrasonicating graphite for 60 min can create high-structural integrity yet solution-processable graphene for a great many applications.
Publisher: Elsevier BV
Date: 04-2020
Publisher: American Chemical Society (ACS)
Date: 02-2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B900988D
Abstract: A combination of density functional theory calculations, electronic absorption and resonance Raman spectroscopy has been applied to a series of beta-substituted zinc porphyrins to elucidate how the substituent affects the electronic structure of the metalloporphyrin and assign the nature of electronic transitions in the visible region. The use of conjugated beta substituents invokes a large perturbation to both the nature and energy of the frontier molecular orbitals and results in the generation of additional molecular orbitals from the parent metalloporphyrin species. A complicated electronic absorption spectra is observed which can be rationalised by an extension of Goutermans' four-orbital model. The excitations involved in the visible transitions have been determined using resonance Raman spectroscopy. This has revealed that the B band retains much of its original nature and is centred largely on the porphyrin core. Additional electronic transitions invoke population of orbitals localised on the substituent chain. The nature of the electronic transitions depends heavily on the type of beta substituent. The results of this investigation question some previously held beliefs for the rational design of metalloporphyrins for dye-sensitized solar cell applications.
Publisher: Elsevier BV
Date: 08-2015
Publisher: American Chemical Society (ACS)
Date: 10-11-2009
DOI: 10.1021/LA903507M
Abstract: A porous, flexible electrode based on a PTFE (Teflon) membrane (Goretex) coated with a metallic current collector and a conducting polymer (poly(3,4-ethylenedioxythiophene), PEDOT) has been developed for applications in solid-state dye-sensitized solar cells. Its low sheet resistance and compressibility make it an ideal electrode on uneven TiO(2) surfaces with high efficiency and reproducibility. The porous nature of the electrode enables the feed-through of reactants and treatment agents, which opens up exciting opportunities to interface these photoelectrochemical devices with electrocatalytic, energy conversion, and storage systems. Postfabrication bonding of the photoanode and the Goretex-Au-PEDOT electrode is demonstrated.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2JM30323J
Publisher: Wiley
Date: 23-07-2012
Publisher: American Chemical Society (ACS)
Date: 26-03-2010
DOI: 10.1021/MA902782X
Publisher: American Chemical Society (ACS)
Date: 18-03-2011
DOI: 10.1021/JA1114634
Abstract: An electroactive nitrospiropyran-substituted polyterthiophene, poly(2-(3,3''-dimethylindoline-6'-nitrobenzospiropyranyl)ethyl 4,4''-didecyloxy-2,2':5',2''-terthiophene-3'-acetate), has been synthesized for the first time. The spiropyran, incorporated into the polymer backbone by covalent attachment to the alkoxyterthiophene monomer units, leads to multiple colored states as a result of both photochemical and electrochemical isomerization of the spiropyran moiety to merocyanine forms as well as electrochemical oxidation of the polyterthiophene backbone and the merocyanine substituents. While electrochemical polymerization of the terthiophene monomer can take place without oxidation of the spiropyran, increasing the oxidation potential leads to complex electrochemistry that clearly involves this substituent. To understand this complex behavior, the first detailed electrochemical study of the oxidation of the precursor spiropyran, 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran, was undertaken, showing that, in solution, an irreversible electrochemical oxidation of the spiropyran occurs leading to reversible redox behavior of at least two merocyanine isomers. With these insights, an extensive electrochemical and spectroelectrochemical study of the nitrospiropyran-substituted polyterthiophene films reveals an initial irreversible electrochemical oxidative ring-opening of the spiropyran to oxidized merocyanine. Subsequent reduction and cyclic voltammetry of the resulting nitromerocyanine-substituted polyterthiophene film gives rise to the formation of both merocyanine π-dimers or oligomers and π-radical cation dimers, between polymer chains. Although merocyanine formation is not electrochemically reversible, the spiropyran can be photochemically regenerated, through irradiation with visible light. Subsequent electrochemical oxidation of the nitrospiropyran-substituted polymer reduces the efficiency of the spiropyran to merocyanine isomerization, providing electrochemical control over the polymer properties. SEM and AFM images support the conclusion that the bulky spiropyran substituent is electrochemically isomerized to the planar merocyanine moiety, affording a smoother polymer film. The conductivity of the freestanding polymer film was found to be 0.4 S cm(-1).
Publisher: Wiley
Date: 16-09-2019
Publisher: Springer Science and Business Media LLC
Date: 31-01-2012
DOI: 10.1038/NCOMMS1661
Publisher: Elsevier BV
Date: 09-2005
Publisher: American Chemical Society (ACS)
Date: 08-06-2018
Abstract: The surfactant-assisted liquid-phase exfoliation of expanded graphite can produce graphene sheets in large quantities with minimal defects. However, it is difficult to completely remove the surfactant from the final product, thus affecting the electrochemical properties of the produced graphene. In this article, a novel approach to fabricate flexible graphene olypyrrole film was developed: using surfactant cetyltrimethylammonium bromide as a template for growth of polypyrrole nanofibers (PPyNFs) instead of removal after the exfoliation process followed by a simple filtration method. The introduction of PPyNF not only increases the electrochemical performance, but also ensures flexibility. This composite film electrode offers a capacitance up to 161 F g
Publisher: Elsevier BV
Date: 09-2014
Publisher: Springer Science and Business Media LLC
Date: 04-08-2015
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7SM00335H
Abstract: Electrical stimulation of hydrogels has been performed to enable micro-actuation or controlled movement of ions and biomolecules such as in drug release applications.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP41137G
Abstract: The photochemistry and thermodynamics of two terthiophene (TTh) derivatives bearing benzospiropyran (BSP) moieties, 1-(3,3″-dimethylindoline-6'-nitrobenzospiropyranyl)-2-ethyl 4,4″-didecyloxy-2,2':5',2″-terthiophene-3'-acetate (BSP-2) and 1-(3,3″-dimethylindoline-6'-nitrobenzospiropyranyl)-2-ethyl 4,4″-didecyloxy-2,2':5',2″-terthiophene-3'-carboxylate (BSP-3), differing only by a single methylene spacer unit, have been studied. The kinetics of photogeneration of the equivalent merocyanine (MC) isomers (MC-2 and MC-3, respectively), the isomerisation properties of MC-2 and MC-3, and the thermodynamic parameters have been studied in acetonitrile, and compared to the parent, non-TTh-functionalised, benzospiropyran derivative, BSP-1. Despite the close structural similarity of BSP-2 and BSP-3, their physicochemical properties were found to differ significantly ex les include activation energies (E(a(MC-2)) = 75.05 kJ mol(-1), E(a(MC-3)) = 100.39 kJ mol(-1)) and entropies of activation (ΔS = 43.38 J K(-1) mol(-1), ΔS = 37.78 J K(-1) mol(-1)) for the thermal relaxation from MC to BSP, with the MC-3 value much closer to the unmodified MC-1 value (46.48 J K(-1) mol(-1)) for this latter quantity. The thermal relaxation kinetics and solvatochromic behaviour of the derivatives in a range of solvents of differing polarity (ethanol, dichloromethane, acetone, toluene and diethyl ether) are also presented. Differences in the estimated values of these thermodynamic and kinetic parameters are discussed with reference to the molecular structure of the derivatives.
Publisher: Elsevier BV
Date: 02-2013
Publisher: American Chemical Society (ACS)
Date: 29-07-2019
Abstract: Spider silks represent stretchable and contractible fibers with high toughness. Those tough fibers with stretchability and contractibility are attractive as energy absorption materials, and they are needed for wearable applications, artificial muscles, and soft robotics. Although carbon-based materials and poly(vinyl alcohol) (PVA) composite fibers exhibit high toughness, they are still limited in low extensibility and an inability to operate in the wet-state condition. Herein, we report stretchable and contractible fiber with toughness that is inspired by the structure of spider silk. The bioinspired tough fiber provides 495 J/g of gravimetric toughness, which exceeds 165 J/g of spider silk. Besides, the tough fiber was reversibly stretched to ∼80% strain without damage. This toughness and stretchability are realized by hybridization of aligned graphene oxide/multiwalled carbon nanotubes in a polyurethane matrix as elastic amorphous regions and β-sheet segments of spider silk. Interestingly, the bioinspired tough fiber contracted up to 60% in response to water and humidity similar to supercontraction of the spider silk. It exhibited 610 kJ/m
Publisher: Springer Science and Business Media LLC
Date: 18-03-2012
Publisher: American Chemical Society (ACS)
Date: 28-10-2019
Abstract: A self-healing electrode is an electrical conductor that can repair internal damage by itself, similar to human skin. Since self-healing electrodes are based on polymers and hydrogels, these components are still limited by low electrical conductivity and mechanical strength. In this study, we designed an electrically conductive, mechanically strong, and printable self-healing electrode using liquid crystal graphene oxide (LCGO) and silver nanowires (AgNWs). The conductive ink was easily prepared by simply mixing LCGO and AgNWs solutions. The ultrathin (3 μm thick) electrode can be printed in various shapes, such as a butterfly, in a freestanding state. The maximum conductivity and strength of the LCGO/AgNW composite were 17 800 S/cm and 4.2 MPa, respectively these values are 24 and 4 times higher, respectively, than those of a previously developed self-healing electrode. The LCGO/AgNW composite self-healed internal damage in ambient conditions with moisture and consequently recovered 96.8% electrical conductivity and 95% mechanical toughness compared with the undamaged state. The electrical properties of the composite exhibited metallic tendencies. Therefore, these results suggest that the composite can be used as an artificial electronic skin that detects environmental conditions, such as compression and temperature. This self-healing artificial electronic skin could be applied to human condition monitoring and robotic sensing systems.
Publisher: American Chemical Society (ACS)
Date: 29-06-2010
DOI: 10.1021/JA1026453
Abstract: Microsecond dye-regeneration kinetics was observed in efficient solid state dye-sensitized solar cells using photoelectrochemically deposited poly(3,4-ethylenedioxythiophene (PEDOT) hole conductors using transient absorption spectroscopy. The dye-regeneration rate is orders of magnitude slower than the case using the I(-)/I(3)(-) redox couple or commonly used small molecule hole conductor and is attributed to the low dye to PEDOT ratio within the films.
Publisher: Elsevier BV
Date: 2010
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5RA21100J
Abstract: Mechanically strong and flexible graphene olypyrrole composite films with hierarchical structures are fabricated. They demonstrate very high areal capacitances.
No related grants have been discovered for Sanjeev Gambhir.