Molecular mechanism of cognitive impairment associated with Parkinson's disease: A stroke perspective.

Parkinson's disease (PD) is a common neurological illness that causes several motor and non-motor symptoms, most characteristically limb tremors and bradykinesia. PD is a slowly worsening disease that arises due to progressive neurodegeneration of specific areas of the brain, especially the substantia nigra of the midbrain. Even though PD has continuously been linked to a higher mortality risk in numerous epidemiologic studies, there have been significant discoveries regarding the connection between PD and stroke. The incidence of strokes such as cerebral infarction and hemorrhage is substantially associated with the development of PD. Moreover, cognitive impairments, primarily dementia, have been associated with stroke and PD. However, the underlying molecular mechanism of this phenomenon is still obscure. This concise review focuses on the relationship between stroke and PD, emphasizing the molecular mechanism of cognition deficit and memory loss evident in PD and stroke. Furthermore, we are also highlighting some potential drug molecules that can target both PD and stroke.

Dataset of optical and electronic properties for MoS2-graphene vertical heterostructures and MoS2-graphene-Au heterointerfaces.

The computational and experimental data presented in this paper refer to the research article "First-Principles Calculations Integrated with Experimental Optical and Electronic Properties for MoS2-graphene Heterostructures and MoS2-graphene-Au Heterointerfaces". The computational data includes structural information, electronic and optical properties, and data to calculate the work functions for various molybdenum disulfide and graphene heterostructures and their heterointerfaces with gold. The optical properties calculations include the frequency-dependent dielectric function, the refractive index, the reflectivity, the extinction coefficient, and the energy loss function. These properties were calculated using the independent particle approximation (IPA). As for the experimental optoelectronic properties, we measured photoluminescence spectra (optical), Raman spectra (vibrational), work function (surface electronic property), and local photoconductivity (semiconducting behavior) of graphene-MoS2 heterointerfaces in addition to individual graphene and MoS2 layers on gold. The variation in the exciton bands, the Raman bands, and in the average work function elucidated the semiconducting n-p junction behavior.

Development of Tetrapod Zinc Oxide-Based UV Sensor for Precision Livestock Farming and Productivity.

In order to ensure the health and welfare of livestock, there has been an emphasis on precision farming of ruminant animals. Monitoring the life index of ruminant animals is of importance for intelligent farming. Here, a wearable sensor for monitoring ultraviolet (UV) radiation is demonstrated to understand the effect of primary and secondary photosensitization on dairy animals. Thin films of wide bandgap semiconductor zinc oxide (ZnO) comprising multilevel of nanostructures from microparticles (MP) to nanoparticles (NP), and tetrapod (T-ZnO), were prepared as the UV sensing active materials. The sensitivity was evaluated by exposing the films to various radiation sources, i.e., 365 nm (UV A), 302 nm (UV B), and 254 nm (UV C), and measuring the electrical resistance change. T-ZnO is found to exhibit higher sensitivity and stable response (on/off) upon exposure to UV A and UV B radiation, which is attributed to their higher surface area, aspect ratio, porosity, and interconnective networks inducing a high density of chemical interaction sites and consequently improved photocurrent generation. A wearable sensor using T-ZnO is packaged and attached to a collar for dynamic monitoring of UV response on ruminant animals (e.g., sheep in this study). The excellent performance of T-ZnO wearable sensors for ruminant animals also holds the potential for a wider range of applications such as residential buildings and public spaces.

Computational data of molybdenum disulfide/graphene bilayer heterojunction under strain.

The data presented in this paper refer to the research article "Dry and Hydrated Defective Molybdenum Disulfide/Graphene Bilayer Heterojunction Under Strain for Hydrogen Evolution from Water Splitting: A First-principle Study". Here, we present the Density Functional Theory (DFT) data used to generate optimal geometries and electronic structure for the MoS2/graphene heterostructure under strain, for dry and hydrated pristine and defect configurations. We also report DFT data used to obtain hydrogen Gibbs free energies for adsorption on the MoS2 monolayer and on graphene of the heterostructure. The DFT data were calculated using the periodic DFT code CRYSTAL17, which employs Gaussian basis functions, under the hybrid functionals PBE0 and HSE06. Moreover, we also report the data used for Quantum Theory of Atoms in Molecules (QTAIM) and Non-covalent Interaction (NCI) analysis calculations. These data were obtained using the optimized unit cell configurations from the periodic DFT and inputted to Gamess program, thus generating files that could be read by the Multiwfn program used for QTAIM and NCI calculations.

Electrochemically Desulfurized Molybdenum Disulfide (MoS2) and Reduced Graphene Oxide Aerogel Composites as Efficient Electrocatalysts for Hydrogen Evolution.

Recent developments in graphene related materials including molybdenum disulfide (MoS2) is gaining popularity as efficient and cost-effective nanoscale electrocatalyst essential for hydrogen production. These "clean" energy technologies require delicate control over geometric, morphological, chemical and electronic structure affecting physical and electrochemical catalytic properties. In this work, we prepared three-dimensional hierarchical mesoporous aerogels consisting of two-dimensional functionalized graphene and MoS2 nanosheets of varying ratio of components under hydrothermal-solvothermal conditions (P <20 bar, T <200 °C). We systematically characterized these hybrid aerogels in terms of surface morphology, microstructure, understand heterointerfaces interaction through electron microscopy, X-ray diffraction, optical absorption and emission and Raman spectroscopy, besides electrochemical properties prior to and post electrochemical desulfurization that induces finely controlled sulfur vacancies. They feature enhanced electrical conductivity by means of eliminating contact resistance and meso-/nanoporous structure facilitating faster ion diffusion (mass transport). We demonstrate that controlled defects density, edges plane sites (nanowalls), mesoscale porosity and topological interconnectedness (monolithic aerogel sheets) invoked can accelerate electrocatalytic hydrogen production. For instance, low over potential with Tafel slope ~77 mV·dec-1 for 60 wt.% MoS2, highcurrent density, and good stability was achieved with desulfurization. These results are compared with continuous multilayer MoS2 films highlighting the multiple role of tunable structure and electronic properties. The adjacent S-vacancy defectsinduced increase in density of states, dissociation and confinement of water molecules at the pore edge and planar S-vacancy sites calculated using density functional theory helped in establishing improved heterogeneous electrocatalytic rate. This is supported with combined measurements of diffusion coefficient and heterogeneous electron transfer rate via surface-sensitive scanning electrochemical microscopy (SECM) technique.

Salt-Assisted Ultrasonicated De-Aggregation and Advanced Redox Electrochemistry of Detonation Nanodiamond.

Nanodiamond particles form agglomerates in the dry powder state and this poses limitation to the accessibility of their diamond-like core thus dramatically impacting their technological advancement. In this work, we report de-agglomeration of nanodiamond (ND) by using a facile technique namely, salt-assisted ultrasonic de-agglomeration (SAUD). Utilizing ultrasound energy and ionic salts (sodium chloride and sodium acetate), SAUD is expected to break apart thermally treated nanodiamond aggregates (~50-100 nm) and produce an aqueous slurry of de-aggregated stable colloidal nanodiamond dispersions by virtue of ionic interactions and electrostatic stabilization. Moreover, the SAUD technique neither has toxic chemicals nor is it difficult to remove impurities and therefore the isolated nanodiamonds produced are exceptionally suited for engineered nanocarbon for mechanical (composites, lubricants) and biomedical (bio-labeling, biosensing, bioimaging, theranostic) applications. We characterized the microscopic structure using complementary techniques including transmission electron microscopy combined with selected-area electron diffraction, optical and vibrational spectroscopy. We immobilized SAUD produced NDs on boron-doped diamond electrodes to investigate fundamental electrochemical properties. They included surface potential (or Fermi energy level), carrier density and mapping electrochemical (re)activity using advanced scanning electrochemical microscopy in the presence of a redox-active probe, with the aim of understanding the surface redox chemistry and the interfacial process of isolated nanodiamond particles as opposed to aggregated and untreated nanoparticles. The experimental findings are discussed in terms of stable colloids, quantum confinement and predominantly surface effects, defect sites (sp²-bonded C and unsaturated bonds), inner core (sp³-bonded C)/outer shell (sp²-bonded C) structure, and surface functionality. Moreover, the surface electronic states give rise to midgap states which serve as electron donors (or acceptors) depending upon the bonding (or antibonding). These are important as electroanalytical platforms for various electrocatalytic processes.

Graphene Quantum Dots Electrochemistry and Sensitive Electrocatalytic Glucose Sensor Development.

Graphene quantum dots (GQDs), derived from functionalized graphene precursors are graphene sheets a few nanometers in the lateral dimension having a several-layer thickness. They are zero-dimensional materials with quantum confinement and edge site effects. Intense research interest in GQDs is attributed to their unique physicochemical phenomena arising from the sp²-bonded carbon nanocore surrounded with edged plane functional moieties. In this work, GQDs are synthesized by both solvothermal and hydrothermal techniques, with the optimal size of 5 nm determined using high-resolution transmission electron microscopy, with additional UV-Vis absorption and fluorescence spectroscopy, revealing electronic band signatures in the blue-violet region. Their potential in fundamental (direct electron transfer) and applied (enzyme-based glucose biosensor) electrochemistry has been practically realized. Glucose oxidase (GOx) was immobilized on glassy carbon (GC) electrodes modified with GQDs and functionalized graphene (graphene oxide and reduced form). The cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy are used for characterizing the direct electron transfer kinetics and electrocatalytical biosensing. The well-defined quasi-reversible redox peaks were observed under various electrochemical environment and conditions (pH, concentration, scan rate) to determine the diffusion coefficient (D) and first-order electron transfer rate (kET). The cyclic voltammetry curves showed homogeneous ion transport behavior for GQD and other graphene-based samples with D ranging between 8.45 × 10-9 m² s-1 and 3 × 10-8 m² s-1 following the order of GO < rGO < GQD < GQD (with FcMeOH as redox probe) < GOx/rGO < GOx/GO < HRP/GQDs < GOx/GQDs. The developed GOx-GQDs biosensor responds efficiently and linearly to the presence of glucose over concentrations ranging between 10 µM and 3 mM with a limit of detection of 1.35 µM and sensitivity of 0.00769 µA µM-1·cm-2 as compared with rGO (0.025 µA µM-1 cm-2, 4.16 µM) and GO (0.064 µA µM-1 cm-2, 4.82 µM) nanosheets. The relatively high performance and stability of GQDs is attributed to a sufficiently large surface-to-volume ratio, excellent biocompatibility, abundant hydrophilic edges, and a partially hydrophobic plane that favors GOx adsorption on the electrode surface and versatile architectures to ensure rapid charge transfer and electron/ion conduction (<10 ms). We also carried out similar studies with other enzymatic protein biomolecules on electrode surfaces prepared from GQD precursors for electrochemical comparison, thus opening up potential sensing applications in medicine as well as bio-nanotechnology.

Electrostatic Layer-By-Layer Self-Assembled Graphene/Multi-Walled Carbon Nanotubes Hybrid Multilayers as Efficient 'All Carbon' Supercapacitors.

In this work, covalently bonded graphene/carbon nanotube (Gr/CNT) conjoined materials are fabricated as engineered three-dimensional hybrid multilayer supercapacitors for high-performance integrated electrochemical energy storage. Stable aqueous dispersion of polymer-modified graphene sheets are prepared in the presence of cationic poly(ethyleneimine), PEI (PEI-Gr) for sequential or electrostatic layer-by-layer (E-LBL) self-assembly with negatively charged acid-oxidized or functionalized multi-walled CNT (fMWCNT), forming (PEI-Gr/fMWCNT)n architecture as "all carbon" super-capacitor, where n = 1, 2, 4, 6, 9, 12 and 15. These films possess an interconnected network of mesoporous nanocarbon structure with well-defined interfaces allowing sufficient surface adsorption and faster ion transport due to short diffusion distances. They exhibit nearly rectangular cyclic voltammograms at an exceedingly high scan rate of 1 V/s with an average specific capacitance of -450 F g(-1) and specific energy density of 75.5 Wh kg(-1) based on electrode weight, measured at a current density of 0.3 A g(-1), comparable to that of Ni metal hydride battery and charged/discharged within a few seconds or a minute. This is attributed to the maximized synergistic effect of the highest specific surface areas by preventing re-aggregation of PEI-Gr or PEI-rGO via fMWCNT as spacers. We also determined relative contributions of the interfacial capacitance (C(dl)) and charge transfer (R(ct)) properties of the hybrids and investigated interfacial properties by SECM technique.

Conducting Polymer Nanostructures and Nanocomposites with Carbon Nanotubes: Hierarchical Assembly by Molecular Electrochemistry, Growth Aspects and Property Characterization.

Conducting (or π-conjugated) polymers are promising materials for preparing supramolecular nano-structures and nanocomposites. We report controlled nanostructure syntheses of polypyrrole (PPy) and poylaniline (PANi) via electropolymerization (i.e., in-situ electrochemical anodic oxidation). The density, shape, caliber and thickness of self-assembled PPy micro-containers are regulated by electrochemical potential window for H2 bubbles and number of cyclic voltammetric (potentiodynamic) scans. Likewise, we employed amperometry, chronopotentiometry and potentiodynamic modes using hydrochloric acid as oxidizing agent to prepare PANi nanoparticles and nanotubules. We present our findings from the viewpoint of molecular electrochemistry with growth kinetic aspects yielding mechanistic details (initially forming dimers and oligomers as nucleating agents followed by polymer growth). Also targeted is forming nanocomposites with functionalized single- and multi-walled carbon nanotubes (FSWCNTs and FMWCNTs) as reinforced agent to optimize structural and functional properties. All of these novel nanomaterials are characterized using a range of complementary techniques to establish microscopic structure-property-function relationship.

Vanadium Pentoxide Nanobelt-Reduced Graphene Oxide Nanosheet Composites as High-Performance Pseudocapacitive Electrodes: ac Impedance Spectroscopy Data Modeling and Theoretical Calculations.

Graphene nanosheets and graphene nanoribbons, G combined with vanadium pentoxide (VO) nanobelts (VNBs) and VNBs forming GVNB composites with varying compositions were synthesized via a one-step low temperature facile hydrothermal decomposition method as high-performance electrochemical pseudocapacitive electrodes. VNBs from vanadium pentoxides (VO) are formed in the presence of graphene oxide (GO), a mild oxidant, which transforms into reduced GO (rGOHT), assisting in enhancing the electronic conductivity coupled with the mechanical robustness of VNBs. From electron microscopy, surface sensitive spectroscopy and other complementary structural characterization, hydrothermally-produced rGO nanosheets/nanoribbons are decorated with and inserted within the VNBs' layered crystal structure, which further confirmed the enhanced electronic conductivity of VNBs. Following the electrochemical properties of GVNBs being investigated, the specific capacitance Csp is determined from cyclic voltammetry (CV) with a varying scan rate and galvanostatic charging-discharging (V-t) profiles with varying current density. The rGO-rich composite V1G3 (i.e., VO/GO = 1:3) showed superior specific capacitance followed by VO-rich composite V3G1 (VO/GO = 3:1), as compared to V1G1 (VO/GO = 1:1) composite, besides the constituents, i.e., rGO, rGOHT and VNBs. Composites V1G3 and V3G1 also showed excellent cyclic stability and a capacitance retention of >80% after 500 cycles at the highest specific current density. Furthermore, by performing extensive simulations and modeling of electrochemical impedance spectroscopy data, we determined various circuit parameters, including charge transfer and solution resistance, double layer and low frequency capacitance, Warburg impedance and the constant phase element. The detailed analyses provided greater insights into physical-chemical processes occurring at the electrode-electrolyte interface and highlighted the comparative performance of thin heterogeneous composite electrodes. We attribute the superior performance to the open graphene topological network being beneficial to available ion diffusion sites and the faster transport kinetics having a larger accessible geometric surface area and synergistic integration with optimal nanostructured VO loading. Computational simulations via periodic density functional theory (DFT) with and without V2O5 adatoms on graphene sheets are also performed. These calculations determine the total and partial electronic density of state (DOS) in the vicinity of the Fermi level (i.e., higher electroactive sites), in turn complementing the experimental results toward surface/interfacial charge transfer on heterogeneous electrodes.

High-temperature annealing effects on multiwalled carbon nanotubes: electronic structure, field emission and magnetic behaviors.

This work elucidates the effects of high-temperature annealing on the microscopic and electronic structure of multiwalled carbon nanotubes (MWCNTs) using high-resolution transmission electron microscopy, micro-Raman spectroscopy, X-ray diffraction, X-ray absorption near-edge structure (XANES) and valence-band photoemission spectroscopy (VBPES), respectively. The field emission and magnetization behaviors are also presented. The results of annealing are as follows: (1) MWCNTs tend to align in the form of small fringes along their length, promote graphitization and be stable in air, (2) XANES indicates an enhancement in oxygen content on the sample, implying that it can be adopted for sensing and storing oxygen gas, (3) the electron field emission current density (J) is enhanced and the turn-on electric field (E(TOE)) reduced, suggesting potential use in field emission displays and as electron sources in microwave tube amplifiers and (4) as-grown MWCNTs with embedded iron nanoparticles exhibits significantly higher coercivity approximately 750 Oe than its bulk counterpart (Fe(bulk) approximately 0.9 Oe), suggesting its potential use as low-dimensional high-density magnetic recording media.

Magnetron sputtered diamond-like carbon microelectrodes for on-chip measurement of quantal catecholamine release from cells.

Carbon electrodes are widely used in electrochemistry due to their low cost, wide potential window, and low and stable background noise. Carbon-fiber electrodes (CFE) are commonly used to electrochemically measure "quantal" catecholamine release via exocytosis from individual cells, but it is difficult to integrate CFEs into lab-on-a-chip devices. Here we report the development of nitrogen doped diamond-like carbon (DLC:N) microelectrodes on a chip to monitor quantal release of catecholamines from cells. Advantages of DLC:N microelectrodes are that they are batch producible at low cost, and are harder and more durable than graphite films. The DLC:N microelectrodes were prepared by a magnetron sputtering process with nitrogen doping. The 30 microm by 40 microm DLC:N microelectrodes were patterned onto microscope glass slides by photolithography and lift-off technology. The properties of the DLC:N microelectrodes were characterized by AFM, Raman spectroscopy and cyclic voltammetry. Quantal catecholamine release was recorded amperometrically from bovine adrenal chromaffin cells on the DLC:N microelectrodes. Amperometric spikes due to quantal release of catecholamines were similar in amplitude and area as those recorded using CFEs and the background current and noise levels of microchip DLC:N electrodes were also comparable to CFEs. Therefore, DLC:N microelectrodes are suitable for microchip-based high-throughput measurement of quantal exocytosis with applications in basic research, drug discovery and cell-based biosensors.