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We report QDπ-v1.0 for modeling the internal energy of drug molecules containing H, C, N, and O atoms. The QDπ model is in the form of a quantum mechanical/machine learning potential correction (QM/Δ-MLP) that uses a fast third order self-consistent density-functional tight-binding (DFTB3/ 3OB) model that is corrected to a quantitatively high-level of accuracy through a deep-learning potential (DeepPot-SE). The model has the advantage that it is able to properly treat electrostatic interactions and handle changes in charge/protonation states. The model is trained against reference data computed at the ωB97X/6-31G* level (as in the ANI-1x data set) and compared to several other approximate semiempirical and machine learning potentials (ANI-1x, ANI-2x, DFTB3, MNDO/d, AM1, PM6, GFN1-xTB, and GFN2-xTB). The QDπ model is demonstrated to be accurate for a wide range of intra-and intermolecular interactions (despite its intended use as an internal energy model) and has shown to perform exceptionally well for relative protonation/deprotonation energies and tautomers. An example application to model reactions involved in RNA strand cleavage catalyzed by protein and nucleic acid enzymes illustrates QDπ has average errors less than 0.5 kcal/mol, whereas the other models compared have errors over an order of magnitude greater. Taken together, this makes QDπ highly attractive as a potential force field model for drug discovery., This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Chemical Theory and Computation, copyright © 2023 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jctc.2c01172

ispartof: Chemistry Of Materials vol:35 issue:13 pages:5049-5058 status: Published online

A theoretical study of an electrode mechanism where the electrode reaction (E) is preceded by a chemical reaction that takes place solely at the electrode surface (Chet) is presented under conditions of square-wave voltammetry (SWV). Rigorous mathematical solutions in the form of integral equations derived by means of Laplace transforms are presented for the surface concentration of all species involved in the electrode mechanism, yielding explicit recurrent formulas for the simulation of the voltammetric response. The theory approximately predicts that the chemical reaction starts at the beginning of the voltammetric experiment, disregarding its occurrence in the short time period between inserting the electrode in the solution until starting the voltammetric experiment. It is demonstrated that SWV can differentiate between the common CE mechanism, where C is a homogeneous chemical reaction taking place in the vicinity of the electrode, and the current ChetE mechanism, which is relevant for plethora of electrocatalytic processes at electrodes modified with catalytically active enzymes and/or noble-metal nanoparticles, as well as for electrocatalytic processes of fundamental importance such as CO2, N2, O2, and H+ reductions

We describe the generalized weighted thermodynamic perturbation (gwTP) method for estimating the free energy surface of an expensive "high-level" potential energy function from the umbrella sampling performed with multiple inexpensive "low-level" reference potentials. The gwTP method is a generalization of the weighted thermodynamic perturbation (wTP) method developed by Li and co-workers [J. Chem. Theory Comput. 2018, 14, 5583-5596] that uses a single "low-level" reference potential. The gwTP method offers new possibilities in model design whereby the sampling generated from several low-level potentials may be combined (e.g., specific reaction parameter models that might have variable accuracy at different stages of a multistep reaction). The gwTP method is especially well suited for use with machine learning potentials (MLPs) that are trained against computationally expensive ab initio quantum mechanical/molecular mechanical (QM/MM) energies and forces using active learning procedures that naturally produce multiple distinct neural network potentials. Simulations can be performed with greater sampling using the fast MLPs and then corrected to the ab initio level using gwTP. The capabilities of the gwTP method are demonstrated by creating reference potentials based on the MNDO/d and DFTB2/MIO semiempirical models supplemented with the "range-corrected deep potential" (DPRc). The DPRc parameters are trained to ab initio QM/MM data, and the potentials are used to calculate the free energy surface of stepwise mechanisms for nonenzymatic RNA 2'-O-transesterification model reactions. The extended sampling made possible by the reference potentials allows one to identify unequilibrated portions of the simulations that are not always evident from the short time scale commonly used with ab initio QM/MM potentials. We show that the reference potential approach can yield more accurate ab initio free energy predictions than the wTP method or what can be reasonably afforded from explicit ab initio QM/MM sampling., This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Chemical Theory and Computation, copyright © 2022 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpca.2c06201

We present a fast, accurate, and robust approach for determination of free energy profiles and kinetic isotope effects for RNA 2'-O-transphosphorylation reactions with inclusion of nuclear quantum effects. We apply a deep potential range correction (DPRc) for combined quantum mechanical/molecular mechanical (QM/MM) simulations of reactions in the condensed phase. The method uses the second-order density-functional tight-binding method (DFTB2) as a fast, approximate base QM model. The DPRc model modifies the DFTB2 QM interactions and applies short-range corrections to the QM/MM interactions to reproduce ab initio DFT (PBE0/6-31G*) QM/MM energies and forces. The DPRc thus enables both QM and QM/MM interactions to be tuned to high accuracy, and the QM/MM corrections are designed to smoothly vanish at a specified cutoff boundary (6 Å in the present work). The computational speed-up afforded by the QM/MM+DPRc model enables free energy profiles to be calculated that include rigorous long-range QM/MM interactions under periodic boundary conditions and nuclear quantum effects through a path integral approach using a new interface between the AMBER and i-PI software. The approach is demonstrated through the calculation of free energy profiles of a native RNA cleavage model reaction and reactions involving thio-substitutions, which are important experimental probes of the mechanism. The DFTB2+DPRc QM/MM free energy surfaces agree very closely with the PBE0/6-31G* QM/MM results, and it is vastly superior to the DFTB2 QM/MM surfaces with and without weighted thermodynamic perturbation corrections. ¹⁸O and ³⁴S primary kinetic isotope effects are compared, and the influence of nuclear quantum effects on the free energy profiles is examined., This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Chemical Theory and Computation, copyright © 2022 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jctc.2c00151

Following the initial cation formation, the synthesis of ionic liquids (ILs) often involves an anion-exchange or metathesis reaction. For hydrophobic ILs, this is generally performed through several cross-current contacts of the IL with a fresh salt solution of the desired anion. However, if a large number of contacts is required to attain an adequate conversion, this procedure is not economical because of the large excess of the reagent that is consumed. In this study, the metathesis of an IL, Aliquat 336 or [A336][Cl], to ILs with other anions ([A336][X] with X = HSO4–, Br–, NO3–, I–, and SCN–) was studied in a continuous counter-current mixer-settler setup. McCabe–Thiele diagrams were constructed to estimate the required number of stages for quantitative conversion. Significantly higher IL conversions were achieved, combined with reduced reagent consumption and waste production. This improvement in efficiency was most pronounced for anions placed low in the Hofmeister series, for example, HSO4–, Br–, and NO3–, which are difficult to exchange. The performance of the counter-current experiments was compared with the conventional multistep cross-current batch process by calculating the reaction mass efficiency (RME) and the environmental factor (E-factor). The RMEs of the cross-current experiments were notably smaller, that is, 38–78% of the values observed for the counter-current experiments. The E-factors of the counter-current experiments were a factor of 2.0–6.8 smaller than those of the cross-current experiments. These sustainability metrics indicate a highly efficient reagent use and a considerable, simultaneous decrease in waste production for the counter-current IL metathesis reactions., A counter-current flow diagram facilitates the efficient metathesis of ionic liquids and allows for a high conversion with minimal reagent consumption.

Selective hydrogenation plays an important role in the chemical industry and has a wide range of applications, including the production of fine chemicals and petrochemicals, pharmaceutical synthesis, healthcare product development, and the synthesis of agrochemicals. Pd-based catalysts have been widely applied for selective hydrogenation due to their unique electronic structure and ability to adsorb and activate hydrogen and unsaturated substrates. However, the exclusive and comprehensive summarization of the size, composition, and surface and interface effect of metal Pd on the performance for selective hydrogenation is still lacking. In this perspective, the research progress on selective hydrogenation using Pd-based catalysts is summarized. The strategies for improving the catalytic hydrogenation performance over Pd-based catalysts are investigated. Specifically, the effects of the size, composition, and surface and interfacial structure of Pd-based catalysts, which could influence the dissociation mode of hydrogen, the adsorption, and the reaction mode of the catalytic substrate, on the performance have been systemically reviewed. Then, the progress on Pd-based catalysts for selective hydrogenation of unsaturated alkynes, aldehydes, ketones, and nitroaromatic hydrocarbons is revealed based on the fundamental principles of selective hydrogenation. Finally, perspectives on the further development of strategies for chemical selective hydrogenation are provided. It is hoped that this perspective would provide an instructive guideline for constructing efficient heterogeneous Pd-based catalysts for various selective hydrogenation reactions. ispartof: ACS OMEGA vol:7 issue:1 pages:17-31 ispartof: location:United States status: published

Glial fibrillary acidic protein (GFAP) is a discriminative blood biomarker for many neurological diseases, such as traumatic brain injury. Detection of GFAP in buffer solutions using biosensors has been demonstrated, but accurate quantification of GFAP in patient samples has not been reported, yet in urgent need. Herein, we demonstrate a robust on-chip graphene field-effect transistor (GFET) biosensing method for sensitive and ultrafast detection of GFAP in patient plasma. Patients with moderate–severe traumatic brain injuries, defined by the Mayo classification, are recruited to provide plasma samples. The binding of target GFAP with the specific antibodies that are conjugated on a monolayer GFET device triggers the shift of its Dirac point, and this signal change is correlated with the GFAP concentration in the patient plasma. The limit of detection (LOD) values of 20 fg/mL (400 aM) in buffer solution and 231 fg/mL (4 fM) in patient plasma have been achieved using this approach. In parallel, for the first time, we compare our results to the state-of-the-art single-molecule array (Simoa) technology and the classic enzyme-linked immunosorbent assay (ELISA) for reference. The GFET biosensor shows competitive LOD to Simoa (1.18 pg/mL) and faster sample-to-result time (

Boron oxide/hydroxide supported on oxidized activated carbon (B/OAC) was shown to be an inexpensive catalyst for the oxidative dehydrogenation (ODH) of propane that offers activity and selectivity comparable to boron nitride. Here, we obtain an atomistic picture of the boron oxide/hydroxide layer in B/OAC by using 35.2 T 11B and 17O solid-state NMR experiments. NMR spectra measured at 35.2 T resolve the boron and oxygen sites due to narrowing of the central-transition powder patterns. A 35.2 T 2D 11B{17O} dipolar heteronuclear correlation NMR spectrum revealed the structural connectivity between boron and oxygen atoms. The approach outlined here should be generally applicable to determine atomistic structures of heterogeneous catalysts containing quadrupolar nuclei. ispartof: Journal Of The American Chemical Society vol:144 issue:41 pages:18766-18771 ispartof: location:United States status: published

There is an environmental concern regarding the use of petroleum-based lubricants, which are generally toxic and nonbiodegradable. Biobased lubricants, such as vegetable oils, are the alternative: they show excellent lubricity, are readily biodegradable and nontoxic. However, a major disadvantage of using vegetable oils in lubricant applications is their lack of thermo-oxidative stability, which can be improved by antioxidant additives. Here, we propose the use of lignin-based additives in biolubricant formulations to improve this feature, based on lignin’s known antioxidant properties. To ensure a stable dispersion in vegetable oil, lignin was partially esterified. Antioxidant properties of lignin before and after palmitoylation were demonstrated in a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Four different lignin-based fractions, commercial Protobind P1000 soda lignin from straw, solvolytically fractionated Protobind P1000 lignin and two lignin fractions from reductively catalyzed fractionation (RCF) of native birch wood, were tested in biolubricant formulations with castor oil as base oil. Those lignin fractions exhibited excellent performance compared to butylated hydroxytoluene (BHT), a commonly used petroleum-based antioxidant. Formulations of modified lignin in castor oil possess improved thermo-oxidative stability, as illustrated by their increased oxidation induction time. Additionally, rheological and tribological tests demonstrate similar, or in some cases improved, lubricating properties compared to castor oil. This study showcases the successful incorporation of lignin-based antioxidants in biolubricant formulations, tackling the major disadvantage of vegetable oils as environment-friendly lubricants.

Life detection missions to the outer solar system are concentrating on the icy moons of Jupiter and Saturn and their inferred subsurface oceans. Access to evidence of habitability, and possibly even life, is facilitated by the ejection of subsurface material in plumes and outgassing fissures. Orbiting spacecraft can intersect the plume material or detect past sputtered remnants of outgassed products and analyze the contents using instruments such as mass spectrometers. Hydrothermalism has been proposed for the subsurface environments of icy moons, and the organic remains of any associated life would be expected to suffer some degradation through hydrothermalism, radiolysis, or spacecraft flyby impact fragmentation. Hydrothermalism is treated here for the first time in the context of the Europa Clipper mission. To assess the influence of hydrothermalism on the ability of orbiting mass spectrometers to detect degrading signals of life, we have subjected Earth microorganisms to laboratory hydrothermal processing. The processed microorganism samples were then analyzed using gas chromatography-mass spectrometry (GC-MS), and mass spectra were generated. Certain compound classes, such as carbohydrates and proteins, are significantly altered by hydrothermal processing, resulting in small one-ring and two-ring aromatic compounds such as indoles and phenols. However, lipid fragments, such as fatty acids, retain their fidelity, and their provenance is easily recognized as biological in origin. Our data indicate that mass spectrometry measurements in the plumes of icy moons, using instruments such as the MAss Spectrometer for Planetary Exploration (MASPEX) onboard the upcoming Europa Clipper mission, can reveal the presence of life even after significant degradation by hydrothermal processing has taken place.

Orbital angular momentum (OAM) of light represents an independent degree of freedom using orthogonal helical modes for optical and quantum multiplexing, offering great potential to transform future ultrahigh-bandwidth information systems. Practical OAM communication systems suffer from turbulence-induced phase distortions to the propagating beams, decreasing the orthogonality of OAM modes through introduced modal crosstalk. To date, optical systems used for measuring OAM orthogonality breakdown in different turbulence conditions are too bulky and slow (e.g., one OAM mode at a time) for any practical use. Here, we demonstrate the use of an ultrathin OAM mode-sorting metasurface for characterizing the OAM orthogonality breakdown under different turbulence conditions. Our approach allows the measurement of the whole OAM spectrum at the same time. This metasurface exhibits strong OAM selectivity with an average modal crosstalk below −42.4 dB for OAM modes with topological charges ranging from −15 to +15. Our results suggest that higher-order OAM modes are as robust as lower-order modes in particular turbulence environments, paving the way for future practical free-space OAM communications harnessing high-dimensional OAM multiplexing. We demonstrated that a flat optical device with a small form factor can be integrated with practical communication systems for compact, fast, and efficient generation and detection of twisted light.

Photocatalytic platforms based on ultrathin reactive materials facilitate carrier transport and extraction but are typically restricted to a narrow set of materials and spectral operating ranges due to limited absorption and poor energy-tuning possibilities. Metasurfaces, a class of 2D artificial materials based on the electromagnetic design of nanophotonic resonators, allow optical absorption engineering for a wide range of materials. Moreover, tailored resonances in nanostructured materials enable strong absorption enhancement and thus carrier multiplication. Here, we develop an ultrathin catalytic metasurface platform that leverages the combination of loss-engineered substoichiometric titanium oxide (TiO2-x) and the emerging physical concept of optical bound states in the continuum (BICs) to boost photocatalytic activity and provide broad spectral tunability. We demonstrate that our platform reaches the condition of critical light coupling in a TiO2-x BIC metasurface, thus providing a general framework for maximizing light-matter interactions in diverse photocatalytic materials. This approach can avoid the long-standing drawbacks of many naturally occurring semiconductor-based ultrathin films applied in photocatalysis, such as poor spectral tunability and limited absorption manipulation. Our results are broadly applicable to fields beyond photocatalysis, including photovoltaics and photodetectors.

We study the effect of size on the vibrational modes and frequencies of nanoparticles, by applying a newly developed, robust, and efficient first-principles-based method that we present in outline. We focus on rutile TiO2, a technologically important material whose bulk exhibits a softening of a transverse acoustic mode close to , which becomes unstable with the application of negative pressure. We demonstrate that, under these conditions, nanoparticles above a critical size exhibit unstable localized modes and we calculate their characteristic localization length and decomposition with respect to bulk phonons. We propose that such localized soft modes could initiate coherent structural phase transformations in small nanoparticles above a critical size.

Solar energy is one of the most actively pursued renewable energy sources, but like many other sustainable energy sources, its intermittent character means solar cells have to be connected to an energy storage system to balance production and demand. To improve the efficiency of this energy conversion and storage process, photobatteries have recently been proposed where one of the battery electrodes is made from a photoactive material that can directly be charged by light without using solar cells. Here, we present photorechargeable lithium-ion batteries (Photo-LIBs) using photocathodes based on vanadium pentoxide nanofibers mixed with P3HT and rGO additives. These photocathodes support the photocharge separation and transportation process needed to recharge. The proposed Photo-LIBs show capacity enhancements of more than 57% under illumination and can be charged to ∼2.82 V using light and achieve conversion efficiencies of ∼2.6% for 455 nm illumination and ∼0.22% for 1 sun illumination. ispartof: NANO LETTERS vol:21 issue:8 pages:3527-3532 ispartof: location:United States status: published

Metal oxides and oxyhydroxides exhibit state-of-the-art activity for the oxygen evolution reaction (OER); however, their reaction mechanism, particularly the relationship between charging of the oxide and OER kinetics, remains elusive. Here, we investigate a series of Mn-, Co-, Fe-, and Zn-doped nickel oxides using operando UV-vis spectroscopy coupled with time-resolved stepped potential spectroelectrochemistry. The Ni2+/Ni3+redox peak potential is found to shift anodically from Mn- < Co- < Fe- < Zn-doped samples, suggesting a decrease in oxygen binding energetics from Mn- to Zn-doped samples. At OER-relevant potentials, using optical absorption spectroscopy, we quantitatively detect the subsequent oxidation of these redox centers. The OER kinetics was found to have a second-order dependence on the density of these oxidized species, suggesting a chemical rate-determining step involving coupling of two oxo species. The intrinsic turnover frequency per oxidized species exhibits a volcano trend with the binding energy of oxygen on the Ni site, having a maximum activity of ∼0.05 s-1at 300 mV overpotential for the Fe-doped sample. Consequently, we propose that for Ni centers that bind oxygen too strongly (Mn- and Co-doped oxides), OER kinetics is limited by O-O coupling and oxygen desorption, while for Ni centers that bind oxygen too weakly (Zn-doped oxides), OER kinetics is limited by the formation of oxo groups. This study not only experimentally demonstrates the relation between electroadsorption free energy and intrinsic kinetics for OER on this class of materials but also highlights the critical role of oxidized species in facilitating OER kinetics.

Recent experimental efforts have investigated nanoparticle solution as glues for hydrogels, focusing on the role of nanoparticle size and shape in influencing adhesion. Here, we use molecular dynamics simulations together with a coarse-grained model and consider a variety of different nanoparticle morphologies to expand on these experiments. Our main result is to show that while nanoparticles’ shape and size can play an important role, whether and how much these two factors affect adhesion strongly depend on the amount of nanoparticles loaded at the interface, as well as on the mutual interaction between the nanoparticles. Furthermore, we suggest that the nanoparticle gluing performance can be qualitatively understood in terms of the relationship between the shape and surface curvature, with lower curvature shapes providing, for different reasons, stronger adhesion in a wider range of nanoparticle loading.

Cyclopentane-1,3-diol (4b) has gained renewed attention as a potential building block for polymers and fuels because its synthesis from hemicellulose-derived 4-hydroxycyclopent-2-enone (3) was recently disclosed. However, cyclopentane1,3-dione (4), which is a constitutional isomer of 3, possesses a higher chemical stability and can therefore afford higher carbon mass balances and higher yields of 4b in the hydrogenation reaction under more concentrated conditions. In this work, the hydrogenation of 4 into 4b over a commercial Ru/C catalyst was systematically investigated on a bench scale through kinetic studies and variation of reaction conditions. Herein, the temperature, H2-pressure, and the solvent choice were found to have significant effects on the reaction rate and suppression of undesired dehydration of 4. The cis−trans ratio of 4b is naturally generated as 7:3 in these reactions. However, at elevated reaction temperatures, 4b epimerizes, yielding more trans products. This effect was also studied and rationalized from a thermodynamic perspective using DFT. The combined optimized reaction conditions provided 78% yield for 4b, and successful applications to 8-fold scaled up reactions (40 g) and a substrate scope of several 1,3-diones demonstrate the general applicability of this catalytic approach. ispartof: Acs Omega vol:6 issue:6 pages:4313-4328 ispartof: location:United States status: published

There is an overwhelming amount of evidence demonstrating that people from marginalized groups, including women, racialized and Indigenous peoples, people with disabilities, immigrants, and LGBTQ+ individuals, continue to face substantial discrimination in STEM, manifested as both overt bias and unconscious bias. These biases result in discrimination against individuals in marginalized groups, and independent biases collectively contribute to a culture that systematically discriminates against people from marginalized groups. Representation from marginalized groups in postsecondary degrees in natural science and engineering has not substantially improved in over a decade. A set of 10 concrete principles are presented that trainees, principle investigators, departments, and faculties can use to enhance the participation and lived experiences of people in marginalized groups in STEM., Steps to reduce bias toward and promote retention of marginalized peoples need to be active and purposeful in order to increase diversity at all stages in STEM fields.

Thin, flexible, and invisible solar cells will be a ubiquitous technology in the near future. Ultrathin crystalline silicon (c-Si) cells capitalize on the success of bulk silicon cells while being lightweight and mechanically flexible, but suffer from poor absorption and efficiency. Here we present a new family of surface texturing, based on correlated disordered hyperuniform patterns, capable of efficiently coupling the incident spectrum into the silicon slab optical modes. We experimentally demonstrate 66.5% solar light absorption in free-standing 1 μm c-Si layers by hyperuniform nanostructuring for the spectral range of 400 to 1050 nm. The absorption equivalent photocurrent derived from our measurements is 26.3 mA/cm2, which is far above the highest found in literature for Si of similar thickness. Considering state-of-the-art Si PV technologies, we estimate that the enhanced light trapping can result in a cell efficiency above 15%. The light absorption can potentially be increased up to 33.8 mA/cm2 by incorporating a back-reflector and improved antireflection, for which we estimate a photovoltaic efficiency above 21% for 1 μm thick Si cells.

The formation of a thin layer, the so-called Joint Oxyde-Gaine (JOG), between the (U,Pu)O2 fuel pellets and the cladding has been observed in fast neutron reactors, due to the accumulation of volatile fission products. Cs2MoO4 is known to be one of the major components of the JOG, but other elements are also present, in particular tellurium and palladium. In this work, an investigation of the structural and thermodynamic properties of Cs2TeO4 and Cs2Mo1–xTexO4 solid solution is reported. The existence of a complete solubility between Cs2MoO4 and Cs2TeO4 is demonstrated, combining X-ray diffraction (XRD), neutron diffraction (ND), and X-ray absorption spectroscopy (XAS) results. High-temperature XRD measurements were moreover performed on Cs2TeO4, which revealed the existence of a α–β phase transition around 712 K. Thermal expansion coefficients were also obtained from these data. Finally, phase equilibra points in the Cs2MoO4–Cs2TeO4 pseudobinary phase diagram were collected using differential scanning calorimetry and used to develop a thermodynamic model for this system using a regular solution formalism., The existence of a complete solid solution between Cs2MoO4 and Cs2TeO4 is demonstrated combining XRD, ND, and EXAFS data. The hexavalent states of Mo and Te in the Cs2Mo1−xTexO4 solid solution have been confirmed by XANES. The existence of a phase transition at (712 ± 5 K) in Cs2TeO4 (from an orthorhomic to an hexagonal structure) is revealed. Phase equilibria measurements in the Cs2MoO4−Cs2TeO4 phase diagram are reported, and a regular solution model has been developed.

Despite having great value across a wide variety of scientific fields, two-photon polymerizations currently suffer from two significant problems: the need for photoinitiators, which generate toxic side products, and the irreversibility of the process. Hence, the design of a versatile approach that circumvents these issues represents a major scientific challenge. Herein, we report a two-photon absorption strategy where reversible [2 + 2] cycloaddition of bis-thymines was achieved without the need for any photoinitiator. The cycloaddition and cycloreversion reactions could be induced by simply changing the irradiation wavelength, and repeated writing and erasing cycles were performed. The simplicity, reversibility, and biocompatibility of this strategy open up a whole new toolbox for applications across a wide variety of scientific fields. ispartof: ACS OMEGA vol:5 issue:20 pages:11547-11552 ispartof: location:United States status: published

Tissue engineering is currently one the fastest growing engineering fields, requiring fabrication of advanced and multifunctional materials to be used as scaffolds or dressing for tissue regeneration. In this work, a bilayer matrix was fabricated by electrospinning of a hybrid cellulose acetate nanofibers (CA) containing bioactive latex or Ciprofloxacin over highly interconnected collagen (CSPG) 3D matrix previously obtained by a freeze-drying process. The bilayer matrix was fabricated with a nanofibrous part as the primary (top) layer and a spongy porous part as the secondary (bottom) layer by combining electrospinning and freeze-drying techniques to enhance the synergistic effect of both materials corresponding to physical and biological properties. The final material was physicochemically characterized using Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The bilayer matrix exhibited nanofibrous and 3D porous structure with properties such as high porosity, swelling, and stability required for soft-tissue-engineering applications. Furthermore, the in vitro biological and fluorescence properties of the matrix were tested against NIH 3T3 fibroblast and human keratinocyte (HaCaT) cell lines and showed good cell adhesion and proliferation over the bilayer matrix. Thus, the synergistic combination of nanofibrous material deposition onto to the collagenous porous material has proved efficient in the fabrication of a bilayer matrix for skin-tissue-engineering applications. ispartof: BIOMACROMOLECULES vol:21 issue:6 pages:2512-2524 ispartof: location:United States status: published

On-chip micro-supercapacitors (MSCs), integrated with energy harvesters, hold substantial promise for developing self-powered wireless sensor systems. However, MSCs have conventionally been manufactured through techniques incompatible with semiconductor fabrication technology, the most significant bottleneck being the electrode deposition technique. Utilization of spin-coating for electrode deposition has shown potential to deliver several complementary metal-oxide-semiconductor (CMOS)-compatible MSCs on a silicon substrate. Yet, their limited electrochemical performance and yield over the substrate have remained challenges obstructing their subsequent integration. We report a facile surface roughening technique for improving the wafer yield and the electrochemical performance of CMOS-compatible MSCs, specifically for reduced graphene oxide as an electrode material. A 4 nm iron layer is deposited and annealed on the wafer substrate to increase the roughness of the surface. In comparison to standard nonroughened MSCs, the increase in surface roughness leads to a 78% increased electrode thickness, 21% improvement in mass retention, 57% improvement in the uniformity of the spin-coated electrodes, and a high yield of 87% working devices on a 2″ silicon substrate. Furthermore, these improvements directly translate to higher capacitive performance with enhanced rate capability, energy, and power density. This technique brings us one step closer to fully integrable CMOS-compatible MSCs in self-powered systems for on-chip wireless sensor electronics. ispartof: ACS OMEGA vol:5 issue:10 pages:5219-5228 ispartof: location:United States status: published

Aβ4–42 is the major subspecies of Aβ peptides characterized by avid Cu(II) binding via the ATCUN/NTS motif. It is thought to be produced in vivo proteolytically by neprilysin, but in vitro experiments in the presence of Cu(II) ions indicated preferable formation of C-terminally truncated ATCUN/NTS species including CuIIAβ4–16, CuIIAβ4–9, and also CuIIAβ12–16, all with nearly femtomolar affinities at neutral pH. Such small complexes may serve as shuttles for copper clearance from extracellular brain spaces, on condition they could survive intracellular conditions upon crossing biological barriers. In order to ascertain such possibility, we studied the reactions of CuIIAβ4–16, CuIIAβ4–9, CuIIAβ12–16, and CuIIAβ1–16 with reduced glutathione (GSH) under aerobic and anaerobic conditions using absorption spectroscopy and mass spectrometry. We found CuIIAβ4–16 and CuIIAβ4–9 to be strongly resistant to reduction and concomitant formation of Cu(I)–GSH complexes, with reaction times ∼10 h, while CuIIAβ12–16 was reduced within minutes and CuIIAβ1–16 within seconds of incubation. Upon GSH exhaustion by molecular oxygen, the CuIIAβ complexes were reformed with no concomitant oxidative damage to peptides. These finding reinforce the concept of Aβ4–x peptides as physiological trafficking partners of brain copper., Aβ4−16, Aβ4−9, and Aβ12−16, oligopeptide products of β-amyloid degradation by neprilysin, bind CuII ions very tightly and are considered as possible CuII carriers in the brain. We demonstrated that CuII(Aβ4−x) complexes, but not CuII(Aβ12−16), are kinetically resistant to reduction by glutathione. No covalent Aβ peptide modifications were observed during the copper reduction and reoxidation by ambient oxygen, yielding the original complexes. These features suggest that CuII(Aβ4−x) complexes might be able to cross the blood−brain barrier.

Organic–inorganic hybrid materials are a promising class of materials for tissue engineering and other biomedical applications. In this systematic study, the effect of the polymer molecular mass (MM) with a linear architecture on hybrid mechanical properties is reported. Well-defined linear poly(methyl methacrylate-co-(3-(trimethoxysilyl)propyl methacrylate)) polymers with a range of MMs of 9 to 90 kDa and one 90 kDa star-shaped polymer were synthesized and then used to form glass–polymer hybrids. It was demonstrated that increasing linear polymer MM decreases the resultant hybrid mechanical strength. Furthermore, a star-polymer hybrid was synthesized as a comparison and demonstrated significantly different mechanical properties relative to its linear-polymer counterpart.

ispartof: Acs Sustainable Chemistry & Engineering vol:9 issue:49 pages:16528-16530 status: published

There is currently a disconnect between the high electrocatalyst oxygen reduction reaction (ORR) performance measured ex situ, using the rotating disc electrode (RDE), and the in situ membrane electrode assembly (MEA) performance. The disconnect in the electrocatalyst performance raises questions both about the pitfalls of the RDE technique at extrapolating the performance to higher overpotentials and how to improve the in situ catalyst layer performance to meet ambitious fuel cell targets. This work aims to bridge the gap by measuring the ORR ex situ performance under high mass transport conditions, at high overpotentials, using the floating electrode (FE) technique. Here, we determine the performance of three Pt/C electrocatalysts using the FE in 1 M HClO4 and 1 M H2SO4 to show that the MEA activities measured at 80 °C, 150 kPag were substantially lower than the room temperature and pressure performance of the same catalyst in 1 M HClO4 using the RDE and FE methods and also lower than the FE in 1 M H2SO4, implying MEA limitations are not purely due to sulfonate adsorption from the Nafion. Finally, FE and MEA data was modeled which obtained jo values on the FE (oxide free conditions) which were 4–6× larger, at 11–26 μA cm–2, than those measured on the MEA. The difference is interpreted as due to better water removal in the FE system. This work shows that MEA catalyst layers are vastly underutilized, due to poor water transport, and current densities equivalent to 10–16 A cm–2 at 0.65 V for 400 μgPt cm–2 (25–40 A mg–1) are achievable, whereas the current mass activity of MEAs is

This work reports saturated-phase densities for the CO2 + methylcyclohexane system at temperatures between 298 and 448 K and at pressures up to the critical pressure. The densities were measured with a standard uncertainty of

ispartof: Acs Catalysis vol:11 issue:21 pages:13603-13648 status: published

Integrated CO2 capture and hydrogenation to methanol may replace fossil resources for production of clean fuels, chemicals, and materials. As opposed to the classic concept of lowering the transiti...

Oligonucleotides (ONs) comprise a rapidly growing class of therapeutics. In recent years, the list of FDA-approved ON therapies has rapidly expanded. ONs are small (15–30 bp) nucleotide-based therapeutics which are capable of targeting DNA and RNA as well as other biomolecules. ONs can be subdivided into several classes based on their chemical modifications and on the mechanisms of their target interactions. Historically, the largest hindrance to the widespread usage of ON therapeutics has been their inability to effectively internalize into cells and escape from endosomes to reach their molecular targets in the cytosol or nucleus. While cell uptake has been improved, “endosomal escape” remains a significant problem. There are a range of approaches to overcome this, and in this review, we focus on three: altering the chemical structure of the ONs, formulating synthetic, lipid-based nanoparticles to encapsulate the ONs, or biologically loading the ONs into extracellular vesicles. This review provides a background to the design and mode of action of existing FDA-approved ONs. It presents the most common ON classifications and chemical modifications from a fundamental scientific perspective and provides a roadmap of the cellular uptake pathways by which ONs are trafficked. Finally, this review delves into each of the above-mentioned approaches to ON delivery, highlighting the scientific principles behind each and covering recent advances.

Hypersound waves can be efficient mediators between optical signals at the nanoscale. Having phase velocities several orders of magnitude lower than the speed of light, they propagate with much shorter wavelengths and can be controlled, directed, and even focused in a very small region of space. This work shows how two optical nanoantennas can be coupled through an acoustic wave that propagates with a certain directionality. An “emitter” antenna is first optically excited to generate acoustic coherent phonons that launch surface acoustic waves through the underlying substrate. These waves travel until they are mechanically detected by a “receiver” nanoantenna whose oscillation produces a detectable optical signal. Generation and detection are studied in detail, and new designs are proposed to improve the directionality of the hypersonic surface acoustic wave.

Three-dimensional (3D) printing is gaining importance as a sustainable route for the fabrication of high-performance energy storage devices. It enables the streamlined manufacture of devices with programmable geometry at different length scales down to micron-sized dimensions. Miniaturized energy storage devices are fundamental components for on-chip technologies to enable energy autonomy. In this work, we demonstrate 3D printed microsupercapacitor electrodes from aqueous inks of pristine graphene without the need of high temperature processing and functional additives. With an intrinsic electrical conductivity of ∼1370 S m-1 and rationally designed architectures, the symmetric microsupercapacitors exhibit an exceptional areal capacitance of 1.57 F cm-2 at 2 mA cm-2 which is retained over 72% after repeated voltage holding tests. The areal power density (0.968 mW cm-2) and areal energy density (51.2 μWh cm-2) outperform the ones of previously reported carbon-based supercapacitors which have been either 3D or inkjet printed. Moreover, a current collector-free interdigitated microsupercapacitor combined with a gel electrolyte provides electrochemical performance approaching the one of devices with liquid-like ion transport properties. Our studies provide a sustainable and low-cost approach to fabricate efficient energy storage devices with programmable geometry.

Polyproline II (pPII) is a left-handed 31-helix conformation, which has been observed to be the most abundant secondary structure in unfolded peptides and proteins compared to α-helix and β-sheet. Although pPII has been reported as the most stable conformation for several unfolded short chain peptides in aqueous solution, it is rarely observed in their solid state. Here, we show for the first time a glycine homopeptide (gly-gly-gly) adopting the pPII conformation in its crystalline dihydrate structure. The single crystal X-ray structure with molecular dynamic simulation suggests that a network of water and the charged carboxylate group is critical in stabilizing the pPII conformation in solid state, offering an insight into the structures of unfolded regions of proteins and the role of water in peptide crystallization.

Computation is increasingly being used to try to accelerate the discovery of new materials. One specific example of this is porous molecular materials, specifically porous organic cages, where the porosity of the materials predominantly comes from the internal cavities of the molecules themselves. The computational discovery of novel structures with useful properties is currently hindered by the difficulty in transitioning from a computational prediction to synthetic realisation. Attempts at experimental validation are often time-consuming, expensive and, frequently, the key bottleneck of material discovery. In this work, we developed a computational screening workflow for porous molecules that includes consideration of the synthetic difficulty of material precursors, aimed at easing the transition between computational prediction and experimental realisation. We trained a machine learning model by first collecting data on 12,553 molecules categorised either as `easy-to-synthesise' or `difficult-to-synthesise' by expert chemists with years of experience in organic synthesis. We used an approach to address the class imbalance present in our dataset, producing a binary classifier able to categorise easy-to-synthesise molecules with few false positives. We then used our model during computational screening for porous organic molecules to bias towards precursors whose easier synthesis requirements would make them promising candidates for experimental realisation and material development. We found that even by limiting precursors to those that are easier-to-synthesise, we are still able to identify cages with favourable, and even some rare, properties.

ispartof: Acs Catalysis vol:11 issue:15 pages:9204-9209 status: published

In UHPLC, frictional heating from the eluent flowing through the column at pressures of ca. 10-15 Kpsi causes radial diffusion via temperature differences between the center of the column and its walls. Longitudinal dispersion also occurs due to temperature gradients between the inlet and outlet. These effects cause band broadening but can be mitigated via a combination of vacuum jacketed stainless steel tubing, reduced column end nut mass, and a constant temperature in the column from heating the inlet fitting. Here, vacuum jacketed column (VJC) technology, employing a novel column housing located on the source of the mass spectrometer and minimized tubing from the column outlet to the electrospray probe, was applied to profiling metabolites in urine. For a 75 s reversed-phase gradient separation, the average peak widths for endogenous compounds in urine were 1.2 and 0.6 s for conventional LC/MS and VJC systems, respectively. The peak tailing factor was reduced from 1.25 to 1.13 when using the VJC system compared to conventional UHPLC, and the peak capacity increased from 65 to 120, with a 25% increase in features detected in urine. The increased resolving power of the VJC system reduced co-elution, simplifying MS and MS/MS spectra, providing a more confident metabolite identification. The increased LC performance also gave more intense MS peaks, with a 10-120% increase in response, improving the quality of the MS data and detection limits. Reducing the LC gradient duration to 37 s gave peak widths of ca. 0.4 s and a peak capacity of 84.