Electrochemical integration of graphene with light absorbing copper-based thin films

We present an electrochemical route for the integration of graphene with light sensitive copper-based alloys used in optoelectronic applications. Graphene grown using chemical vapor deposition (CVD) transferred to glass is found to be a robust substrate on which photoconductive Cu_{x}S films of 1-2 um thickness can be deposited. The effect of growth parameters on the morphology and photoconductivity of Cu_{x}S films is presented. Current-voltage characterization and photoconductivity decay experiments are performed with graphene as one contact and silver epoxy as the other

Correction: Professor (Dr) Sukh Dev: an iconic scientist with an innate sixth sense who radicalized natural product synthesis & organic chemistry

<jats:p>Correction for ‘Professor (Dr) Sukh Dev: an iconic scientist with an innate sixth sense who radicalized natural product synthesis & organic chemistry’ by Harry Kochat <jats:italic>et al.</jats:italic>, <jats:italic>Org. Biomol. Chem.</jats:italic>, 2024, <jats:bold>22</jats:bold>, 5466–5469, https://doi.org/10.1039/D4OB90071E.</jats:p&gt

Conformational analysis and design of cross-strand disulfides in antiparallel beta-sheets

Cross-strand disulfides bridge two cysteines in a registered pair of antiparallel beta-strands. A nonredundant data set comprising 5025 polypeptides containing 2311 disulfides was used to study cross-strand disulfides. Seventy-six cross-strand disulfides were found of which 75 and 1 occurred at non-hydrogen-bonded (NHB) and hydrogen-bonded (HB) registered pairs, respectively. Conformational analysis and modeling studies demonstrated that disulfide formation at HB pairs necessarily requires an extremely rare and positive chi(1) value for at least one of the cysteine residues. Disulfides at HB positions also have more unfavorable steric repulsion with the main chain. Thirteen pairs of disulfides were introduced in NHB and HB pairs in four model proteins: leucine binding protein (LBP), leucine, isoleucine, valine binding protein (LIVBP), maltose binding protein (MBP), and Top7. All mutants LIVBP T247C V331C showed disulfide formation either on purification, or on treatment with oxidants. Protein stability in both oxidized and reduced states of all mutants was measured. Relative to wild type, LBP and MBP mutants were destabilized with respect to chemical denaturation, although the sole exposed NHB LBP mutant showed an increase of 3.1 degrees C in T-m. All Top7 mutants were characterized for stability through guanidinium thiocyanate chemical denaturation. Both exposed and two of the three buried NHB mutants were appreciably stabilized. All four HB Top7 mutants were destabilized (Delta Delta G(0) = -3.3 to -6.7 kcal/mol). The data demonstrate that introduction of cross-strand disulfides at exposed NHB pairs is a robust method of improving protein stability. All four exposed Top7 disulfide mutants showed mild redox activity. Proteins 2011; 79: 244-260. (C) 2010 Wiley-Liss, Inc

Polytypism in ultrathin tellurium

We report the synthesis of ultrathin tellurium films, including atomically thin tellurium tri-layers, by physical vapor deposition (PVD) as well as larger area films by pulsed laser deposition (PLD). PVD leads to sub-nanometer, tri-layer tellurene flakes with distinct boundaries, whereas PLD yields uniform and contiguous sub-7 nm films over a centimeter square. The PLD films exhibit the characteristic hexagonal crystal structure of semiconducting tellurium, but high resolution transmission electron microscopy (HRTEM) reveals a unique stacking polytype in the thinner PVD-grown material. Density Functional Theory calculations predict the possible existence of three polytypes of ultrathin Te, including the α-type experimentally observed here. The two complementary growth methods afford a route to controllably synthesize ultrathin Te with thicknesses ranging from three atomic layers up to 6 nm with unique polytypism. Lastly, temperature dependent Raman studies suggest the possible coexistence of polymorphs

Consolidation of functionalized graphene at ambient temperature via mechano-chemistry

Graphitic solids are typically produced via high temperature and energy consuming processing (e.g. sintering) of carbon particles. Here, we demonstrate the mechano-chemical assembly of functionalized graphene layers into 3D graphitic solids via room temperature and low energy consuming processing. The chemical functional groups on graphene layers are interconnected at room temperature under pressure leading to porous three-dimensional structures with tunable mechanical and electrical properties. The formation of mechano-chemistry induced atomic scale junctions and their impact on mechanical properties of graphene assembled carbon materials are demonstrated through nano-indentation experiments and confirmed using DFT and molecular dynamics simulations. The results show room temperature consolidation routes of graphene layers into bulk carbon solids.by Chandra Sekhar Tiwary et al

Graphene transistors for interfacing with cells: towards a deeper understanding of liquid gating and sensitivity

This work is focused on the fabrication and analysis of graphene-based, solution-gated field effect transistor arrays (GFETs) on a large scale for bioelectronic measurements. The GFETs fabricated on different substrates, with a variety of gate geometries (width/length) of the graphene channel, reveal a linear relation between the transconductance and the width/length ratio. The area normalised electrolyte-gated transconductance is in the range of 1–2 mS·V−1·□ and does not strongly depend on the substrate. Influence of the ionic strength on the transistor performance is also investigated. Double contacts are found to decrease the effective resistance and the transfer length, but do not improve the transconductance. An electrochemical annealing/cleaning effect is investigated and proposed to originate from the out-of-plane gate leakage current. The devices are used as a proof-of-concept for bioelectronic sensors, recording external potentials from both: ex vivo heart tissue and in vitro cardiomyocyte-like HL-1 cells. The recordings show distinguishable action potentials with a signal to noise ratio over 14 from ex vivo tissue and over 6 from the cardiac-like cell line in vitro. Furthermore, in vitro neuronal signals are recorded by the graphene transistors with distinguishable bursting for the first time