Influence of Ag Photodeposition Conditions over SERS Intensity of Ag/ZnO Microspheres for Nanomolar Detection of Methylene Blue

Surface enhanced Raman spectroscopy (SERS) is considered a versatile and multifunctional technique with the ability to detect molecules of different species at very low molar concentration. In this work, hierarchical ZnO microspheres (ZnO MSs) and Ag/ZnO MSs were fabricated and decorated by hydrothermal and photodeposition methods, respectively. For Ag deposition, precursor molar concentration (1.9 and 9.8 mM) and UV irradiation time (5, 15, and 30 min) were evaluated by SEM, TEM, X-ray diffraction and Raman spectroscopy. X-ray diffraction showed a peak at 37.9° corresponding to the (111) plane of Ag, whose intensity increases as precursor concentration and UV irradiation time increases. SEM images confirmed the formation of ZnO MSs (from 2.5 to 4.5 µm) building by radially aligned two-dimensional ZnO nanosheets with thicknesses below 30 nm. The Raman spectra of Ag/ZnO MSs exhibited a vibration mode at 486 cm−1 which can be directly associated to Ag deposition on ZnO MSs surface. The performance of SERS substrate was evaluated using rhodamine 6G. The SERS substrate grown at 9.8 mM during 30 min showed the best SERS activity and the ability to detect methylene blue at 10−9 M.

Influence of molar ratio of MAI and PbI2 on synthesis of perovskite film

This study explores the influence of molar ratio of the synthetic solution of methylammonium iodide (MAI) and PbI2 on perovskite solar cells. The complete perovskite crystals must be produced in a low-humidity environment. The substrate is spin-coated in the adjusted MAPbI3 synthesis solution and annealed by using a nitrogen furnace tube to form perovskite crystals. During the crystallization of MAPbI3, some of the PbI2 remains, which improves the efficiency of the perovskite solar cell. Therefore, we adjust the molar concentration of MAI to find the appropriate amount of the PbI2 residual. We fix the MAI molar concentration at 1 M and adjust the PbI2 molar concentration from 0.8 M to 1.4 M. The molar ratios of MAI and PbI2 are, then, 1:0.8, 1:1, 1:1.2, and 1:1.4, respectively. Then, we use UV–vis, FE-SEM, and photoelectric conversion efficiency (PCE) measurements for comparing the growth of perovskite crystals and their photoelectric characteristics. The results show that 1.2 M of PbI2 is the most appropriate concentration for perovskite solar cells among the adjusted concentrations.

Effects of Drying Temperature and Molar Concentration on Structural, Optical, and Electrical Properties of β-Ga2O3 Thin Films Fabricated by Sol–Gel Method

In this study, β-Ga2O3 films were fabricated on a quartz substrate by the sol–gel method using different drying temperatures and solutions of different molar concentrations, and their structural, optical, and electrical properties were evaluated. The as-fabricated films exhibited a monoclinic β-Ga2O3 crystal structure, whose crystallinity and crystallite size increased with increasing molar concentration of the solutions used and increasing drying temperature. Scanning electron microscopy of the as-prepared samples revealed dense surface morphologies and that the thickness of the films also depended on the deposition conditions. The average transmittance of all the samples was above 8% in visible light, and the calculated optical bandgap energy was 4.9 eV. The resistivity measured using a 4-point probe system was 3.7 × 103 Ω cm.

Design Optimization of Deep Eutectic Solvent Composition and Separation Performance of Cyclohexane and Benzene Mixtures with Extractive Distillation

Deep eutectic solvents (DESs) have properties that make them suitable candidates to be used as entrainers for extractive distillation. In the previous work, it was proven that DES(1:2) (tetrabutylammonium bromide: levulinic acid, 1:2, molar ratio) can break the cyclohexane-benzene azeotrope. In the present work, the HBA and HBD ratio and molar concentration of DES were optimized to obtain a better constitute and condition of DES to be utilized in cyclohexane and benzene extractive distillation. The physical properties and structure of the prepared DESs were characterized. Vapor–liquid equilibrium data of the ternary system (benzene + cyclohexane + DESs) were also measured at atmospheric pressure. All experimental equilibrium data were correlated with Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) activity coefficient models, from which the coefficient of determination (R2) of the three pseudo-ternary systems fitting was calculated. From the obtained results, the best HBA and HBD ratio in the DESs is elucidated as 1:2, the best molar concentration of DES is 0.1, and the NRTL model predicts the experimental data more accurately than the Wilson and UNIQUAC models. From the derived mechanism, the formation of stronger hydrogen bond and π–π bond interactions between DES and benzene is obtained when HBA and HBD ratio in DES is 1:2. In other conditions, the azeotrope cannot be broken, or the efficiency is low. The present work provides an environmentally friendly method to separate aromatic/aliphatic mixtures and act as a guide for further study of DESs in extractive distillation.

Fabrication of vibration sensors using precursor molar concentration varied ZnO nanostructures grown by refresh hydrothermal method

Purpose Various approaches have been made to alter the vibration sensing properties of zinc oxide (ZnO) films to achieve high sensitivity. This paper aims to report the experimental study of the fabrication of precursor molar ratio concentration varied ZnO nanostructures grown on rigid substrates using the refresh hydrothermal method. The effect of these fabricated ZnO nanostructures-based vibration sensors was experimentally investigated using a vibration sensing setup. Design/methodology/approach ZnO nanostructures have been grown using low temperature assisted refresh hydrothermal method with different precursor molar concentrations 0.025 M (R1), 0.075 M (R2) and 0.125 M (R3). Poly 3,4-ethylenedioxythiophene polystyrene sulfonate, a p-type material is spun coated on the grown ZnO nanostructures. Structural analysis reveals the increased intensity of the (002) plane and better c-axis orientation of the R2 and R3 sample comparatively. Morphological examination shows the changes in the grown nanostructures upon increasing the precursor molar concentration. The optical band gap value decreases from 3.11 eV to 3.08 eV as the precursor molar concentration is increased. Photoconductivity study confirms the formation of a p-n junction with less turn-on voltage for all the fabricated devices. A less internal resistance of 0.37 kΩ was obtained from Nyquist analysis for R2 compared with the other two fabricated samples. Vibration testing experimentation showed an improved output voltage of the R2 sample (2.61 V at 9 Hz resonant frequency and 2.90 V for 1 g acceleration) comparatively. This also gave an increased sensitivity of 4.68 V/g confirming its better performance when compared to the other fabricated two samples. Findings Photoconductivity study confirms the formation of a p-n junction with less turn-on voltage for all the fabricated devices. A less internal resistance of 0.37 kΩ was calculated from the Nyquist plot. Vibration testing experimentation proves an increased sensitivity of 4.68 V/g confirming its better performance when compared to the other fabricated two samples. Originality/value Vibration testing experimentation proves an increased sensitivity of 4.68 V/g for R2 confirming its better performance when compared to the other fabricated two samples.

EFFECT OF MOLARCONCENTRATION OF PRECURSORSON THE STRUCTURAL, OPTICALAND ELECTRICAL PROPERTIES OF CUALS2 THIN FILMS PREPARED BY CHEMICAL BATH DEPOSITION TECHNIQUE

CuAlS2 thin films have been prepared on glass substrates by Chemical bath deposition (CBD) technique at a substrate temperature (Ts) 75C, pH value 10.5.The Effect of three different molar concentration (0.05, 0.025, 0.1), (0.075, 0.0375, 0.15), and (0.1, 0.05, 0.2) M of precursors of (CuSO4.5H2O, Al2(SO4)3.16H2O, and (NH2)2CS), respectively on the structural, optical and electrical properties of deposit thin films was studied. The X-ray diffraction (XRD) patterns showed that the films have an amorphous structure with simple enhancement in the structure of the films with the higher molar concentration. Field emission scanning electron microscopy (FESEM) analysis of thin films showed that the deposited films were a good surface morphology, homogenous and uniform spherical nanoparticles over the substrate surface with very little agglomerated particles with average grain size in the range (45 to 72 nm) increase with increasing molar concentration of precursors. Atomic force microscopy (AFM) showed the topography of deposited films has nanoparticles with structures like conical and lobes shape, with the average grain sizes, root mean square (rms) roughness, and surface roughness increase with increasing molar concentration of precursors. The optical analysis by UV-Vis Spectrophotometer showed high absorption in the ultraviolet region, with absorption edge and direct energy gaps (3.5 to 4eV) variedat different molar concentrations of precursors. The electrical results from Hall effect measurements showed that the values of resistivity, conductivity, mobility, and carrier concentration were varied in range (0.046 to 0.594ohm.cm), (1.86 to 21.7(ohm.cm)-1), (301to 1510 cm2/V.S), and (3.29×1016 to 1.46×1017 cm-3), respectively .Also,n-type conductivity was investigated for all prepared film sat different molar concentration of precursors. The obtained results of the prepared CuAlS2 thin films can be suitable in many optoelectronics applications.