Synthesis of Graphitic Carbon Coated ZnPS3 and its Superior Electrochemical Properties for Lithium and Sodium Ion Storage

Graphitic carbon-coated ZnPS3 is prepared via direct phosphosulfurization and high energy mechanical milling (HEMM) with multiwall carbon nanotubes (MWCNTs) and first introduced as an anode for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The HEMM process with MWCNTs reduces the particle size of as-synthesized ZnPS3 bulk to 100-500 nm and yields the ≈5 nm thick graphitic carbon coated ZnPS3 nanoparticles, which are the nanocomposites of 5 nm sized nanocrystallites embedded in the amorphous matrix. The ZnPS3 electrode undergoes the combined conversion and alloying reactions with Li and Na ions and exhibits high initial discharge and charge capacities in both LIBs and SIBs. The graphitic carbon-coated ZnPS3 electrode exhibits excellent high-rate capability and long-term cyclability. The superior electrochemical properties can be attributed to high electrical conductivity, high Li ion mobility, and high reversibility and structural stability derived from the graphitic carbon-coated nanoparticles. This study demonstrates that the novel graphitic carbon-coated ZnPS3 is a promising anode material for both LIBs and SIBs and the graphitic carbon coating methodology by HEMM is expected to apply to the various metal oxides, sulfides, and phosphides.

Evaluation of Piezoresistive and Electrical Properties of Conductive Nanocomposite Based on Castor-Oil Polyurethane Filled with MWCNT and Carbon Black

Flexible films of a conductive polymer nanocomposite-based castor oil polyurethane (PUR), filled with different concentrations of carbon black (CB) nanoparticles or multiwall carbon nanotubes (MWCNTs), were obtained by a casting method. The piezoresistive, electrical, and dielectric properties of the PUR/MWCNT and PUR/CB composites were compared. The dc electrical conductivity of both PUR/MWCNT and PUR/CB nanocomposites exhibited strong dependences on the concentration of conducting nanofillers. Their percolation thresholds were 1.56 and 1.5 mass%, respectively. Above the threshold percolation level, the electrical conductivity value increased from 1.65 × 10^-12 for the matrix PUR to 2.3 × 10^-3 and 1.24 × 10^-5 S/m for PUR/MWCNT and PUR/CB samples, respectively. Due to the better CB dispersion in the PUR matrix, the PUR/CB nanocomposite exhibited a lower percolation threshold value, corroborated by scanning electron microscopy images. The real part of the alternating conductivity of the nanocomposites was in accordance with Jonscher's law, indicating that conduction occurred by hopping between states in the conducting nanofillers. The piezoresistive properties were investigated under tensile cycles. The nanocomposites exhibited piezoresistive responses and, thus, could be used as piezoresistive sensors.

Effects of Annealing Temperature and Time on Properties of Thermoplastic Polyurethane Based on Different Soft Segments/Multi-Walled Carbon Nanotube Nanocomposites

Typically, polymer chains can move under the annealing process, resulting in an ordered structure arrangement. This causes an improvement in nanocomposite properties and in the dispersion of filler. In this research, annealed thermoplastic polyurethane (PU)/multi-walled carbon nanotube (MWCNT) nanocomposites were studied to investigate the effect of annealing on the selective dispersion of MWCNTs. PU matrices were composed of two different soft segments, i.e., polyether (PU-Ether) and polyester (PU-Ester). Nanocomposites were prepared by the melt mixing process and annealed at 80 to 120 °C for 6 to 24 h. The increases in annealing time and temperature resulted in microphase separation in segmented PU and the orientation of crystalline structures in the segregated hard domain. Nanocomposites showed higher electrical conductivity after annealing. This implies that the movement of PU chains during heat treatment encouraged the development of the MWCNT network. However, the increase in ordered structures could obstruct the MWCNT network, resulting in lower electrical conductivity levels. Considering the selective dispersion of MWCNT in PU matrices, it was found that MWCNTs dispersed in soft segments of PU-Ether, leading to a significant decrease in elongation at the break after annealing. On the other hand, a decrease in elasticity of PU-Ester nanocomposites was not observed as a result of MWCNT dispersal in hard segments.

A Molecularly Imprinted Sol-Gel Electrochemical Sensor for Naloxone Determination

A molecularly imprinted sol-gel is reported for selective and sensitive electrochemical determination of the drug naloxone (NLX). The sensor was developed by combining molecular imprinting and sol-gel techniques and electrochemically grafting the sol solution onto a functionalized multiwall carbon nanotube modified indium-tin oxide (ITO) electrode. The sol-gel layer was obtained from acid catalyzed hydrolysis and condensation of a solution composed of triethoxyphenylsilane (TEPS) and tetraethoxysilane (TES). The fabrication, structure and properties of the sensing material were characterized via scanning electron microscopy, spectroscopy and electrochemical techniques. Parameters affecting the sensor's performance were evaluated and optimized. A sensor fabricated under the optimized conditions responded linearly between 0.0 µM and 12 µM NLX, with a detection limit of 0.02 µM. The sensor also showed good run-to-run repeatability and batch-to-batch performance reproducibility with relative standard deviations (RSD) of 2.5-7.8% (n = 3) and 9.2% (n = 4), respectively. The developed sensor displayed excellent selectivity towards NLX compared to structurally similar compounds (codeine, fentanyl, naltrexone and noroxymorphone), and was successfully used to measure NLX in synthetic urine samples yielding recoveries greater than 88%.