School of Chemistry - Research Publications

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    Nanoscale magnetometry through quantum control of nitrogen-vacancy centres in rotationally diffusing nanodiamonds
    MACLAURIN, D ; Hall, LT ; Martin, AM ; Hollenberg, LC (IOP Publishing, 2013)
    The confluence of quantum physics and biology is driving a new generation of quantum-based sensing and imaging technology capable of harnessing the power of quantum effects to provide tools to understand the fundamental processes of life. One of the most promising systems in this area is the nitrogen–vacancy centre in diamond—a natural spin qubit which remarkably has all the right attributes for nanoscale sensing in ambient biological conditions. Typically the nitrogen–vacancy qubits are fixed in tightly controlled/isolated experimental conditions. In this work quantum control principles of nitrogen–vacancy magnetometry are developed for a randomly diffusing diamond nanocrystal. We find that the accumulation of geometric phases, due to the rotation of the nanodiamond plays a crucial role in the application of a diffusing nanodiamond as a bio-label and magnetometer. Specifically, we show that a freely diffusing nanodiamond can offer real-time information about local magnetic fields and its own rotational behaviour, beyond continuous optically detected magnetic resonance monitoring, in parallel with operation as a fluorescent biomarker.
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    Understanding the Biological Interactions of pH-Swellable Nanoparticles
    Kermaniyan, SS ; Chen, M ; Zhang, C ; Smith, SA ; Johnston, APR ; Such, C ; Such, GK (WILEY-V C H VERLAG GMBH, 2022-03-04)
    pH-responsive nanoparticles have generated significant interest for use as drug delivery systems due to their potential for inducible release at low pH. The pH variation from the bloodstream (pH 7.4) to intracellular compartments of cells called endosomes/lysosomes (pH < 5.0) has been of particular interest. However, one of the limitations with nanoparticle delivery systems is the inability to migrate out of these compartments to the cytosol or other organelles, via a process termed endosomal escape. Previous studies have postulated that pH-responsive nanoparticles can facilitate endosomal escape through a range of mechanisms including membrane interaction, pH-induced swelling, and the proton-sponge effect. In this study, a series of pH-swellable nanoparticles (85-100 nm) are designed and their impact on biological interactions, particularly endosomal escape, are investigated. The particles exhibit tunable pH-induced swelling (from 120% to 200%) and have good buffering capacity. The cellular association is studied using flow cytometry and endosomal escape is determined using a calcein leakage assay. Interestingly, no endosomal escape with all nanoparticle formulations is found, which suggests there are limitations with both the proton-sponge effect and pH-induced swelling mechanism as the primary methods for inducing endosomal escape.
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    Site Specific Preparation of N-Glycosylated Peptides: Thioamide-Directed Activation of Aspartate
    Taresh, AB ; Hutton, CA (WILEY-V C H VERLAG GMBH, 2022-09-21)
    A site-specific method for the preparation of N-glycosylated peptides is described. Incorporation of a peptide backbone thioamide linkage adjacent to an Asp residue facilitates a AgI -promoted, site-specific conversion to N-glycosylated Asn residues in peptides.
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    Intensity Modulated Photocurrent Microspectrosopy for Next Generation Photovoltaics
    Laird, JS ; Ravishankar, S ; Rietwyk, KJ ; Mao, W ; Bach, U ; Smith, TA (WILEY-V C H VERLAG GMBH, 2022-08-16)
    In this report, a large-area laser beam induced current microscope that has been adapted to perform intensity modulated photocurrent spectroscopy (IMPS) in an imaging mode is described. Microscopy-based IMPS method provides a spatial resolution of the frequency domain response of the solar cell, allowing correlation of the optoelectronic response with a particular interface, bulk material, specific transport layer, or transport parameter. The system is applied to study degradation effects in back-contact perovskite cells where it is found to readily differentiate areas based on their markedly different frequency response. Using the diffusion-recombination model, the IMPS response is modeled for a sandwich structure and extended for the special case of lateral diffusion in a back-contact cell. In the low-frequency limit, the model is used to calculate spatial maps of the carrier ambipolar diffusion length. The observed frequency response of IMPS images is then discussed.
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    Pretty Cool Beetles: Can Manipulation of Visible and Near-Infrared Sunlight Prevent Overheating?
    Ospina-Rozo, L ; Subbiah, J ; Seago, A ; Stuart-Fox, D (OXFORD UNIV PRESS, 2022-09-13)
    Passive thermoregulation is an important strategy to prevent overheating in thermally challenging environments. Can the diversity of optical properties found in Christmas beetles (Rutelinae) be an advantage to keep cool? We measured changes in temperature of the elytra of 26 species of Christmas beetles, exclusively due to direct radiation from a solar simulator in visible (VIS: 400-700 nm) and near infrared (NIR: 700-1700 nm) wavebands. Then, we evaluated if the optical properties of elytra could predict their steady state temperature and heating rates, while controlling for size. We found that higher absorptivity increases the heating rate and final steady state of the beetle elytra in a biologically significant range (3 to 5°C). There was substantial variation in the absorptivity of Christmas beetle elytra; and this variation was achieved by different combinations of reflectivity and transmissivity in both VIS and NIR. Size was an important factor predicting the change in temperature of the elytra after 5 min (steady state) but not maximum heating rate. Lastly, we show that the presence of the elytra covering the body of the beetle can reduce heating of the body itself. We propose that beetle elytra can act as a semi-insulating layer to enable passive thermoregulation through high reflectivity of elytra, resulting in low absorptivity of solar radiation. Alternatively, if beetle elytra absorb a high proportion of solar radiation, they may reduce heat transfer from the elytra to the body through behavioral or physiological mechanisms.
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    Recent Development of Atmospheric Water Harvesting Materials: A Review
    Feng, A ; Akther, N ; Duan, X ; Peng, S ; Onggowarsito, C ; Mao, S ; Fu, Q ; Kolev, SD (American Chemical Society (ACS), 2022-09-14)
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    Lewis Base Catalyzed Synthesis of Sulfur Heterocycles via the C1‐Pyridinium Enolate
    Cromwell, S ; Sutio, R ; Zhang, C ; Such, GK ; Lupton, DW (Wiley, 2022-08-15)
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    Hans Charles Freeman 1929-2008
    Hambley, TW ; Rae, ID (CSIRO Publishing, 2022-07-01)
    Hans Freeman was born in Germany and arrived in Australia with his parents in 1938. A brilliant student at the University of Sydney, he spent a seminal year at the California Institute of Technology before joining the staff at Sydney and initiating research on bioinorganic chemistry, studying metal ion complexes of compounds of biological significance such as amino acids, peptides and proteins. In his use of X-ray crystallography he was a pioneer in Australia, constructing his first crystallographic apparatus and mastering the necessary computing, at first by hand but soon with electronic computers. The culmination of his work with a series of collaborators was the structure of the blue, copper-containing metalloprotein, plastocyanin. Freeman also employed another advanced technique—X-ray spectroscopy and the study of X-ray absorption fine structure. He was a leading figure in Australia and internationally, and played an important role in gaining access for Australian scientists to international facilities such as synchrotron radiation sources at the dawning of the era of ‘Big Science’.
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    Lewis Base Catalyzed Synthesis of Sulfur Heterocycles via the C1-Pyridinium Enolate
    Cromwell, S ; Sutio, R ; Zhang, C ; Such, GK ; Lupton, DW (WILEY-V C H VERLAG GMBH, 2022-07-11)
    While the addition of C1-Lewis base enolates to carbonyls and related structures are well established, the related addition to thiocarbonyls compounds are unknown. Herein, we report a reaction cascade in which a C1-pyridinium enolate undergos addition to dithioesters, trithiocarbonates and xanthates. The reaction provides access to a range of dihydrothiophenes and dihydrothiopyrans (28-examples). Mechanistic investigations, including isolation of intermediates, electronic correlation, and kinetic isotope effect studies support the viability of an activated acid intermediate giving rise to the C1-pyridinium enolate which undergoes turnover limiting cyclization. Subsequent formation of a β-thiolactone regenerates the catalyst with loss of carbon oxysulfide providing the observed products.