The on-site Coulomb potential, $U$, and the covalent state of electronic orbitals play key roles for the Cooper pair symmetry and exotic electromagnetic properties of high-$T_{\mathrm{c}}$ superconducting cuprates. In this paper, we demonstrate a way to determine the value of $U$ and present the whole picture of the covalent state of Cu spins in the mother system of the La-based high-$T_{\mathrm{c}}$ superconducting cuprate, ${\mathrm{La}}_2{\mathrm{CuO}}_4$, by combining the muon spin rotation $\left(\mu \mathrm{SR}\right)$ and the density functional theory (DFT) calculation. We reveal local deformations of the ${\mathrm{CuO}}_6$ octahedron followed by changes in Cu-spin distributions caused by the injected muon. Adjusting the DFT and $\mu \mathrm{SR}$ results, $U$ and the minimum charge-transfer energy between the upper Hubbard band and the O $2p$ band were optimized to be 4.87(4) and 1.24(1) eV, respectively.

The magnetic hysteresis curve can provide information about magnetic properties, particle size, and its distribution. For superparamagnetic materials, the characteristics of the hysteresis curve are very typical, that is, Hc is equal to zero with a certain Ms value related to particle size in the order of nanometers. Here, we report the analysis of the magnetization hysteresis curve by applying a modified Langevin equation with and without a log-normal distribution for nearly superparamagnetic Fe3O4 and Fe3O4 encapsulated by SiO2 (Fe3O4–SiO2). To study the reliability of the modified Langevin equation, we compared the particle size values obtained from fittings analysis of the modified Langevin equation with those obtained from the TEM measurement. It was found that particle size from TEM measurement for Fe3O4 and Fe3O4–SiO2 is 11 and 14 nm, respectively. These values had a very high match with the particle size obtained from fitting analysis of the modified Langevin equation with or without a log-normal distribution, which is 12.6 and 12.9 nm for Fe3O4 and 13.8 and 14.5 nm for Fe3O4–SiO2, respectively. The fitting results of the modified Langevin equation with a log-normal distribution showed a value closer to the measurement results. By using the modified Langevin equation with a log-normal distribution, it was also obtained that the probability density function for Fe3O4 was 20.69% and that for Fe3O4–SiO2 was 0.55%. It was concluded that the modified Langevin equation with and without log-normal distribution was able to be used to obtain the particle size and its distribution for nearly superparamagnetic samples.

Corncobs are a waste product from corn farming that are abundant in Indonesia. Corncobs have a high cellulose content, more than 40%, which made it useful for synthesizing CMC. CMC is a cellulose derivative that is widely used in many industries such as food, pharmaceutical, detergent, textile, cosmetic product and binder. In this paper, we use CMC that are synthesized from corncobs as binder in the electrodes of lithium ion battery. The steps of synthesizing CMC from corncobs started with the isolation of the cellulose, then followed by the processes of alkalization, carboxymethylation and finally the purification. FTIR spectrum shows that CMC are successfully synthesized. The presence of strong absorption band at 1613 cm^-1 is related to the stretching vibration of the carboxyl group (COO-). The absorption in the 1300–1450 cm^-1 region is due to symmetrical deformations of CH₂ groups. While the broad absorption around 3427 cm^-1 is due to the stretching of the hydroxyl groups (-OH). Test on three samples of different sizes, (mesh-100, mesh-60 and mesh-40) gives CMC purity values of 98.69%, 98.56% and 97.77%, respectively. In the application of CMC as anode binder, the best composition is 4% CMC, where it gives the highest conductivity of 0.587 S/cm. Voltammogram measurement with a scan rate of 50 mV/s in the voltage range of -1 to 1 Volt gives the capacitance value of 2237 μF.

In this study, TiO₂ nanofibers was synthesized using electrospinning method with varying applied voltage (10 kV–20 kV) to obtain high surface-volume ratio and porous material. As the applied voltage increased, diameter of TiO₂ nanofibers decreased and the presence of beads disappeared resulting in homogeneous nanofibers. At applied voltage higher than 16 kV, TiO₂ nanofibers have diameter less than 100 nm. TiO₂ nanofibers are deposited on top of TiO₂ nanoparticles which act as a light-scattering layer. Based on the I–V characteristic, TiO₂ nanofibers produced by applied voltage of 18 kV gives the highest efficiency of 2.38% with J_SC 6.37 mA cm⁻², V_OC of 0.74 V and fill factor of 50.54%. Adding the TiO₂ nanofibers as light-scattering layer improve and extend the path of light, thereby increasing the power conversion efficiency of dye-sensitized solar cells.

Metal oxide semiconductor has attracted so much attention due to its high carrier mobility. Herein, thermoelectric study of nanocrystalline SnO2 through a simple co-precipitation method is conducted to enhance the Seebeck coefficient (S). X-ray diffraction, thermogravimetric analysis (TGA), resistivity (r), Seebeck coefficient (S), and power factor (PF) measurements are conducted to analyze the thermoelectric properties of the material. The measurements show that there are two interesting results, which are the unusual resistivity behavior and the high value of the S. Resistivity behavior shows a non-reflective intermediate semiconductor-metals behavior where the turning point occurs at 250 o C. This behavior is strongly correlated to the surface oxide reaction due to annealing temperature. The maximum S likely occurs at 250 ºC, since the curve shows a slight thermopower peak at 250 ºC. The value of the S is quite high with around twenty times higher than other publications about SnO2 thermoelectric material, this happens due to the bandgap broadening. The energy gap of SnO2 calculated using density functional theory (DFT), which was performed by Quantum Espresso 6.6. The result shows that there is a broadening energy gap at different momentum or wave factor. Nanocrystalline semiconductors material is giving an impact to increase the width of bandgap due to quantum confinement and could enhance the thermopower especially in SnO2 nanocrystalline

The hopping mechanism in the regio-random poly (3-hexylthiophene-2,5-diyl) was investigated through study on the diffusion rate of the charge carrier transport from the data of Longitudinal Field (LF) muon-spin-relaxation measurements. Values of the parallel and perpendicular diffusion rate were calculated following the methods applied in NMR. It is found that diffusion rate along the polymer chain slowly decreases from low to high temperatures, while diffusion rate perpendicular to the polymer chain rises significantly from low to high temperatures.