Electrochemical Properties of Sn/C Nanoparticles Fabricated by Pulse Wire Evaporation for Lithium Secondary Batteries.

In this work, bare Sn and carbon-coated Sn nanoparticles were prepared by a pulsed wire evaporation process. The effect of binder and pressing ratio on electrochemical properties of Sn/C composite electrodes was investigated to enhance the structural stability of Sn anode. The electrode containing the polyamide-imide (PAI) binder with high tensile strength (52 MPa) exhibited higher coulombic efficiency and better cycle performance compared to the electrode with the conventional polyvinylidene fluoride (PVdF) binder. The 5%-pressed Sn/C electrode with the proper porosity in the electrode demonstrated the best cycle performance corresponding to 45% of capacity retention ratio until 100 cycles.

Influence of Oxidized Graphene Quantum Dots as Photosensitizers.

In this study, we successfully prepared oxidatively functionalized graphene quantum dots (GQDs) to engineer the absorption band of a photoanode. By employing a facile hydrothermal process, we demonstrate the degree of intrinsic oxidation at the polar carbene edges of the GQDs, using Raman spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The cyclic voltammetry results show that oxygen functional groups on the GQDs can change the highest occupied molecular orbital and lowest unoccupied molecular orbital levels. Dye-sensitized solar cells, with the GQDs dissolved in the dye, were evaluated in terms of their I-V characteristics and conversion efficiencies. The GQDs dissolved in the dye were easily attachable to TiO2 porous particles, and also contributed to the photoelectric conversion efficiency.

Fabrication and Characterization of Graphene-Based Electrochemical Sensors for Glucose Measurement.

Glucose in the blood is generally measured by electrochemical method using glucose oxidase (GOx) which acts as enzymes and reduced graphene oxide (rGO) composite. The rGO, which has low dispersibility, reduces the sensing capability of sensors. In order to solve this problem, the rGO electrodes with the addition of polyvinylpyrrolidone (PVP) have been reported. However, rGO with low electrical conductivity and mobility is not compatible to the electrochemical system. In this study, graphene with excellent electrical properties was added to PVP protected rGO. The rGO was synthesized using a Hummer and Offeman's method. Graphene was synthesized using chemical vapor deposition (CVD) with a Cu catalyst. Platinum (Pt) electrodes, Ag/AgCl, and PVP protected rGO were used as working electrode, reference electrode, and counter electrode, respectively. Surface morphology and structural properties of graphene were analyzed using atomic force microscopy (AFM), Raman spectroscopy, and Fourier transform infrared spectroscopy (FT-IR). Cyclic voltametry (CV) and I-V probe station were used to analyze the performance of the electrodes. Glucose concentration was systematically varied and the reduction current was monitored using I-V probe station.

Microstructural and Electrochemical Properties of LiCoO2 Thin Films Prepared by Metal-Induced Crystallization.

LiCoO2 thin films were fabricated using the metal-induced crystallization (MIC) method. The effect of MIC on the microstructural and electrochemical properties of the films was investigated. The crystal structures and surface morphologies of the deposited films were investigated by X-ray diffraction (XRD), Raman spectroscopy, and field emission electron microscopy (FE-SEM). Charge-discharge tests were carried out in order to examine the electrochemical properties of the films. The LiCoO2 thin film fabricated using MIC exhibited better microstructural and electrochemical properties at a lower annealing temperature.

Influence of Sn doping on structural and optical properties of zinc oxide nanorods prepared via hydrothermal process.

Hydrothermally grown ZnO nanorods were doped with various concentrations of Sn, ranging from 0 to 2.5 at%. Scanning electron microscopy (SEM), X-ray diffractometer (XRD), ultraviolet (UV)-visible spectroscopy, and Photoluminescence (PL) measurements were used to determine the effect of Sn doping on the structural and optical properties. In the SEM images, the nanorods have hexagonal wurtzite structure and the diameter of the nanorods increases with an increase in the Sn content. The optical parameters of the Sn-doped ZnO (SZO) nanorods such as the absorption coefficients, optical bandgaps, Urbach energies, refractive indices, dispersion parameters, dielectric constants, and optical conductivities were determined from the transmittance and reflectance results. In the PL spectra, the intensity of the NBE peak in the UV region decreases and is blue-shifted with an increase in the Sn content, while the DLE peaks of the nanorods in the visible region shift toward the low-energy region with the introduction of Sn.

Effects of the electrical conductivity and orientation of silicon substrate on the synthesis of multi-walled carbon nanotubes by thermal chemical vapor deposition.

We studied the effects of the electrical conductivity and orientation of silicon substrate on both catalytic Fe thin film and the structure and morphology of multi-walled carbon nanotube (MWNT) grown by low-pressure chemical vapor deposition. Both p-type Si(100) and Si(111) substrates with three different doping concentrations (high, low, undoped) were used to evaluate the formation of catalytic nanoparticles and the growth of MWNTs. The morphology of catalytic nanoparticles such as size and density was characterized by field-emission scanning electron microscopy, Cs-corrected energy-filtered transmission electron microscopy, and X-ray photoelectron spectroscopy. Structural characteristics of MWNTs grown on different combinations of silicon substrate orientation and electrical conductivities (σ) were also systematically analyzed. Based on the experimental results, growth modes of MWNTs could be controlled by choosing an appropriate combination of σ and orientation of Si substrates.

Fabrication and characterization of carbon-based counter electrodes prepared by electrophoretic deposition for dye-sensitized solar cells.

Three different carbon-based counter electrodes are investigated in light of catalytic activities such as electrochemical frequencies and interface impedances. We fabricated carbon-based counter electrodes of dye-sensitized solar cells [DSSCs] using graphene, single-walled carbon nanotubes [SWNTs], and graphene-SWNT composites by electrophoretic deposition method. We observed the optical and electrochemical properties of the carbon-based counter electrodes. The DSSC with the graphene-deposited counter electrode demonstrated the best conversion efficiency of 5.87% under AM 1.5 and 1 sun condition. It could be utilized for a low-cost and high-throughput process for DSSCs.