Fabrication and electrical characterization of p-Cu2O/n-ZnO heterojunction

The conducting metal oxide (ZnO, Cu2O) films were used for fabrication of p-n heterojunction by rf sputtering and electrodeposition techniques respectively. The as synthesized films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV spectroscopy and electrical techniques. The electrical properties of the p-Cu2O/n-ZnO heterojunction were examined using the current-voltage measurements. The current-voltage (I-V) result showed that potential barrier was higher than the turn-on voltage, which was attributed to the presence of the interface defect states. The PN junction parameters such as ideality factor, barrier height, and series resistance were determined using conventional forward bias current-voltage characteristics. The annealing of Cu2O increase the crystallinity size and which enhance the photo current from 1.6 mA/cm2 to 3.7 mA/cm2. The annealing of respective film resulted in a decrease of these parameters with an increase in efficiency of solar cell from 0.14% to 0.3% at 350 degrees C.     

Densities,ultrasonic speeds,refractive indices,and COSMO analysis for binary mixtures of dichloromethane with acetone and dimethylsulfoxide at T = (298.15, 303.15, and 308.15) K

Experimental densities (ρ), ultrasonic speeds (u), and refractive indices (n_D) of binary mixtures of dichloromethane (DCM) with acetone (ACT) and dimethylsulfoxide (DMSO) were measured over the whole composition range at T?=?298.15, 303.15, and 308.15?K. From the experimental data, excess molar volume (V^E), deviations in isentropic compressibility (Δk_s), deviations in intermolecular free length (ΔL_f), deviations in refractive index (Δn_D), and deviations in ultrasonic speed (Δu) were calculated. Moreover, the Benson–Kiyohara theory was applied to the binary mixtures to obtain the theoretical Δk_s values. The COSMO calculations depending on density functional theory were utilized to estimate the σ-profiles for the DCM, ACT, and DMSO. The interpreted σ-profile trends were found supportive with the experimental findings. Applicability of different empirical and semi-empirical relations of refractive index data were tested against the measured results, and good agreement has been obtained. The possible results of intermolecular molecular interactions among mixture components were interpreted.     

The effects of thioacetamide/copper molar ratio and reaction time on the phase evolution,morphology, optical,and photocatalytic properties of the nanosheets-based flower-like copper sulfide

In this paper, various morphologies including spherical and flower-like nanosheets-based CuS were synthesized by the green hydrothermal synthesis method. Copper (II) nitrate trihydrate and thioacetamide (TAM) were selected as a Cu²⁺ and sulfur source, respectively. The effects of TAM/Cu molar ratio and reaction time on the phase and morphological evolution of the samples were studied. For this purpose, the samples were distinguished by FT-IR, FE-SEM, XRD, and ultraviolet-visible spectroscopy. The photocatalytic and optical properties of the products were evaluated. It was found that self-organized nanoflower(SONF) structures exhibit very good photocatalyst efficiency to degrade organic dye due to a significant increase in their surface area because of decorated nanosheets on the sample. Therefore, the SONF structures exhibited a very suitable potential as the photocatalyst agents.     

The role of graphene and europium on TiO2 performance for photocatalytic hydrogen evolution

Highly efficient Eu-TiO₂/graphene composites were synthesized by a two-step method such as sol-gel and hydrothermal process. The synthesized photocatalysts were characterized by XRD, TEM, XPS, UV–vis diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy. The results confirmed that anatase Eu-TiO₂ nanoparticles with average 10 nm sizes were successfully deposited on two-dimensional graphene sheets. The UV–visible spectroscopy showed a red shift in the absorption edge of TiO₂ due to Eu doping and graphene incorporation. Moreover, effective charge separation in Eu-TiO₂/graphene composites was confirmed by PL emission spectroscopy compared to TiO₂/graphene, Eu-TiO₂ and pure TiO₂. The photocatalytic activity for H₂ evolution over prepared composites was studied under visible light irradiation (λ ≥ 400 nm). The results demonstrate that photocatalytic performance of the photocatalysts for hydrogen production increases with increasing doping concentration of Eu upto 2 at%. However, further increase in doping content above this optimum level has decreased the performance of photocatalyst. The enhanced photocatalytic performance for H₂ evolution is attributed to extended visible light absorption, suppressed recombination of electron-hole pairs due to synergistic effects of Eu and graphene.     

Enhancement of Al-N co-dopant solubility in ZnO by high temperature thermal annealing

In this paper, we have developed a method to enhance the Al-N co-dopant solubility in bulk ZnO prepared by solid state reaction method. Reactive donor Al and acceptor N were mobilized by annealing the samples at various temperatures from 650 to 850?°C with a step of 50?°C in a programmable furnace. The solubility enhancement argument was verified by the conductivity measurements which showed that the conductivity of annealed films increases as the annealing temperature increases. The activation energy was calculated by the Arrhenius plot and was found to be (0.08?eV) very close to activation energy of shallow acceptor (nitrogen). To further strengthened our argument, we have also performed XRD, FTIR, Raman Spectroscopy and SEM measurements. XRD data suggested that only ZnO phases were present and no evidence for the presence of AlN, Al₂O₃ or Zn₃N₂ phases. We have also observed weakening and peak shifting of (002) with annealing temperature that suggested the incorporation of more acceptor defects in the crystal of ZnO. FTIR results verified the presence of Zn-O bond (437?cm^?1) along with week vibration of Al-N bond at 917?cm^?1. Raman spectroscopy data consists of 2E₂, A₁ (LO) and E_2(high) modes of ZnO but sample annealed at 800?°C has additional nitrogen related mode at 507?cm^?1. SEM images demonstrated the crystalline nature of samples having smooth surface but sample annealed at 800?°C has rough surface which indicated the enhancement of acceptor defects density.     

Boron nitride-based electrocatalysts for HER,OER, and ORR: A mini-review

A reliable and efficient solution to the current energy crisis and its associated environmental issues is provided by fuel cells, metal–air batteries and overall water splitting. The heart reactions for these technologies are oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Different supporters such as graphene, carbon nanotube, and graphitic carbon nitride have been used to avoid agglomeration of active materials and provide maximum active surface for these reactions. Among all the supporters, boron nitride (BN) gains extensive research attention due to its analogue with graphene and excellent stability with good oxidation and chemical inertness. In this mini-review, the well-known strategies (exfoliation, annealing, and CVD) used in the synthesis of BN with different morphologies for HER, OER and ORR applications have been briefly debated and summarized. The comparative analysis determines that the performance and stability of state-of-the-art electrocatalysts can be further boosted if they are deposited on BN. It is revealed that BN-based catalysts for HER, OER and ORR are rarely studied yet especially with non-noble transition metals, and this research direction should be studied deeply in future for practical applications.     

Interaction of Glycylglycine with Cationic Surfactants—Cetylpyridinium Chloride and Cetylpyridinium Bromide: A Volumetric,Ultrasonic and Conductometric Study

The interactions of glycylglycine (di-peptide of glycine) also known as 2-[(2-aminoacetyl)amino] acetic acid with cationic surfactants cetylpyridinium chloride (CPC) and cetylpyridinium bromide (CPB) as a function of temperature in aqueous medium has been studied by well-know permutation of volumetric, ultrasonic and conductometric techniques. These measurements have been used to evaluate some useful thermodynamic parameters viz. apparent molar volumes, \( \phi_{v} \), partial molar volumes, \( \phi_{v}^{o} \), transfer volumes, \( \phi_{\text{v}}^{0} (tr) \), partial molar expansibility, \( \phi_{E}^{0} \), hydration number, n_H, apparent molal compressibility, \( \phi_{K} \), limiting partial molal adiabatic compressibility, \( \phi_{K}^{0} \). The specific conductivity (κ) was used to calculate the critical micellar concentration (cmc) and other physicochemical parameters of micellization of CPC/CPB with glycylglycine. The critical micelle concentration, cmc and limiting molar conductivity, \( \varLambda_{m}^{o} \) of the two surfactant systems were determined by using the conductivity data at 298.15 K, 303.15 K, 308.15 K and 313.15 K. The acquired data have been discussed as per various interactions taking place in the ternary system of CPC/CPB, glycylglycine and water.     

Static stress analysis of composite spur gears using 3D-finite element and cyclic symmetric approach

It is more realistic to include the effect of adjacent teeth stiffness while evaluating the root stresses of a gear which is a rotationally periodic structure. This requires very large core and computational time. In the present analysis an attempt has been made to compare the root stresses with and without considering the effects of adjacent gear teeth stiffnesses using the concept of cyclic symmetry. Further, an attempt has been made to study the performance of a composite spur gear using the above approach. It is found that the root structure predicted by the method of cyclic symmetry is less for both isotropic and orthotropic spur gears.     

Thermal evaporation and condensation synthesis of metallic Zn layered polyhedral microparticles

Metallic zinc layered polyhedral microparticles have been fabricated by thermal evaporation and condensation technique using zinc as precursor at 750 °C for 120 min and NH₃ as a carrier gas. The zinc polyhedral microparticles with oblate spherical shape are observed to be 2-9 μm in diameter along major axes and 1-7 μm in thickness along minor axes. The structural, compositional and morphological characterizations were performed by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). A vapour-solid (VS) mechanism based growth model has been proposed for the formation of Zn microparticles. Room temperature photoluminescence (PL) emission spectrum of the product exhibited a strong emission band at 369 nm attributed to the radiative recombination of electrons in the s, p conduction band near Fermi surface and the holes in the d bands generated by the optical excitation.