Chemical and Biomolecular Engineering - Research Publications
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ItemAdvancing Catalysts by Stacking Fault Defects for Enhanced Hydrogen Production: A Review(WILEY-V C H VERLAG GMBH, 2024-05)Green hydrogen, derived from water splitting powered by renewable energy such as solar and wind energy, provides a zero-emission solution crucial for revolutionizing hydrogen production and decarbonizing industries. Catalysts, particularly those utilizing defect engineering involving the strategical introduction of atomic-level imperfections, play a vital role in reducing energy requirements and enabling a more sustainable transition toward a hydrogen-based economy. Stacking fault (SF) defects play an important role in enhancing the electrocatalytic processes by reshaping surface reactivity, increasing active sites, improving reactants/product diffusion, and regulating electronic structure due to their dense generation ability and profound impact on catalyst properties. This review explores SF in metal-based materials, covering synthetic methods for the intentional introduction of SF and their applications in hydrogen production, including oxygen evolution reaction, photo- and electrocatalytic hydrogen evolution reaction, overall water splitting, and various other electrocatalytic processes such as oxygen reduction reaction, nitrate reduction reaction, and carbon dioxide reduction reaction. Finally, this review addresses the challenges associated with SF-based catalysts, emphasizing the importance of a detailed understanding of the properties of SF-based catalysts to optimize their electrocatalytic performance. It provides a comprehensive overview of their various applications in electrocatalytic processes, providing valuable insights for advancing sustainable energy technologies.
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ItemOrganic carbon utilisation by the filamentous alga Tribonema(SPRINGER, 2024-01-01)Abstract Filamentous algae have potential application to wastewater treatment, in particular for efficient recovery of nutrients into biomass. However, supplying inorganic carbon is a major limiting factor. The utilisation of organic carbon present in wastewater may reduce the constraints in carbon supply, however there is little knowledge of mixotrophic growth amongst filamentous algae. This study investigated the utilisation of organic carbon sources relevant to wastewater by the filamentous xanthophyte alga Tribonema. Algae growth was compared in the absence of organic carbon (autotrophic) and in presence of 0.2 g-C L-1 glucose, ethanol or acetate under mixotrophic (presence of organic carbon and light) or heterotrophic (presence of organic carbon and absence of light) conditions. To investigate direct utilisation of organic carbon and indirect utilisation via bacterial CO2-genesis, cultivation was performed under both axenic and non-axenic conditions. Tribonema was found to directly utilise glucose, which increased mixotrophic productivity and maintained growth under heterotrophic conditions. In contrast, acetate was only indirectly utilised mixotrophically in the presence of bacteria, whereas ethanol was not utilised under any conditions. The underlying mechanisms of glucose utilisation by Tribonema were also investigated by analysing its photosynthetic rate and respiration rate under glucose concentrations ranging from 0 – 100 g L-1. Based on the results, enhancements to metabolic pathways and reduced CO2 requirements provided by glucose utilisation were proposed. Despite the positive results with respect to glucose utilisation, out competition for this resource by bacteria suggest that Tribonema is more suitable for treatment of wastewater with low organic carbon concentrations, such as secondary-treated wastewater effluent.
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ItemNo Preview AvailableOptimised start-up strategy for bioelectrochemical systems operating on hydrolysed human urine(ELSEVIER SCIENCE SA, 2024-08)Key nutrients, such as nitrogen measured as total ammonium nitrogen (TAN), could be recycled from hydrolysed human urine back to fertiliser use. Bioelectrochemical systems (BESs) are an interesting, low-energy option for realising this. However, the high TAN concentration (> 5 g L-1) and pH (> 9) of hydrolysed urine can inhibit microbial growth and hinder the enrichment of an electroactive biofilm at the anode. This study investigated a new strategy for bioanode inoculation by mixing real hydrolysed urine with thickened waste activated sludge (TWAS) from a municipal wastewater treatment plant at different volumetric ratios. The addition of TWAS diluted the high TAN concentration of hydrolysed urine (5.2 ± 0.3 g L-1) to 2.6-5.1 g L-1, while the pH of the inoculation mixtures remained > 9 and soluble chemical oxygen demand (sCOD) at 5.6-6.7 g L-1. Despite the high pH, current generation started within 24 h for all reactors, and robust bioanodes tolerant of continuous feeding with undiluted hydrolysed urine were enriched within 11 days of start-up. Current output and Coulombic efficiency decreased with increasing initial hydrolysed urine fraction. The anodes inoculated with the highest sCOD-to-TAN ratio (2.1) performed the best, which suggests that high organics levels can protect microbes from inhibition even at elevated TAN concentrations.
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ItemNo Preview AvailableEffect of storage conditions on the characteristics of cryogenic hydrogen jet dispersion(Elsevier BV, 2024-05-20)
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ItemNo Preview AvailableBiofouling control in reverse osmosis membranes by concentrated free ammonia in hydrolysed urine(Elsevier BV, 2024-07-01)
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ItemThe Impact of Activating Agents on Non-Enzymatic Nucleic Acid Extension Reactions(Wiley, 2024-04-02)Non-enzymatic template-directed primer extension is increasingly being studied for the production of RNA and DNA. These reactions benefit from producing RNA or DNA in an aqueous, protecting group free system, without the need for expensive enzymes. However, these primer extension reactions suffer from a lack of fidelity, low reaction rates, low overall yields, and short primer extension lengths. This review outlines a detailed mechanistic pathway for non-enzymatic template-directed primer extension and presents a review of the thermodynamic driving forces involved in entropic templating. Through the lens of entropic templating, the rate and fidelity of a reaction are shown to be intrinsically linked to the reactivity of the activating agent used. Thus, a strategy is discussed for the optimization of non-enzymatic template-directed primer extension, providing a path towards cost-effective in vitro synthesis of RNA and DNA.
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ItemVacuum-Free Liquid-Metal-Printed 2D Semiconducting Tin Dioxide: The Effect of Annealing(American Chemical Society, 2024)Thin film transistors (TFTs) offer unparalleled opportunities for the fabrication of multifunctional electronic and optoelectronic devices. In this work, we report a vacuum-free liquid metal exfoliation technique for rapidly printing ∼2 nm-thick layer of oxide from molten tin. We explore the effect of rapid thermal annealing at 450 °C on the stoichiometry, morphology, and crystal structure of the resulting tin oxide nanosheets. The annealed samples exhibit a dominant SnO2 phase and a high degree of transparency (>99%) in the visible spectra. Field-effect transistors based on the two-dimensional (2D) SnO2 films show typical n-channel conduction with a field-effect mobility of ∼7.5 cm2 V–1 s–1. Photodetectors utilizing annealed tin dioxide demonstrate significant improvement in photoresponsivity reaching a value of 5.2 × 103 A W–1 compared to that found in an unannealed sample at an ultraviolet wavelength of 285 nm. We demonstrate that the improvement in device performance is due to nanocrystalline changes within the oxide layers during the annealing process. This work offers a straightforward and ambient air-compatible method for depositing ultrathin, large-area semiconducting oxides as potential candidates for enabling emerging applications in transparent nanoelectronics and optoelectronics.
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ItemPhotophysical and Fluorescence Anisotropic Behavior of Polyfluorene β-Conformation Films(AMER CHEMICAL SOC, 2018-01-18)We demonstrate a systematic visualization of the unique photophysical and fluorescence anisotropic properties of polyfluorene coplanar conformation (β-conformation) using time-resolved scanning confocal fluorescence imaging (FLIM) and fluorescence anisotropy imaging microscopy (FAIM) measurements. We observe inhomogeneous morphologies and fluorescence decay profiles at various micrometer-sized regions within all types of polyfluorene β-conformational spin-coated films. Poly(9,9-dioctylfluorene-2,7-diyl) (PFO) and poly[4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]-co-[5-(octyloxy)-9,9-diphenylfluoren-2,7-diyl] (PODPF) β-domains both have shorter lifetime than those of the glassy conformation for the longer effective conjugated length and rigid chain structures. Besides, β-conformational regions have larger fluorescence anisotropy for the low molecular rotational motion and high chain orientation, while the low anisotropy in glassy conformational regions shows more rotational freedom of the chain and efficient energy migration from amorphous regions to β-conformation as a whole. Finally, ultrastable ASE threshold in the PODPF β-conformational films also confirms its potential application in organic lasers. In this regard, FLIM and FAIM measurements provide an effective platform to explore the fundamental photophysical process of conformational transitions in conjugated polymer.