No abstract

A simple and low-cost and highly calibrated probe sonication method was used to prepare bismuth oxide nanoparticles (Bi2O3 NPs). The formation of a well-crystalline sample at the end of the product has been further calcined at 600°C for 2 hrs. The powder X-ray diffraction (PXRD) patterns of the NPs substantiated the monoclinic structure (space group P21/c), and the average crystallite size was found to be 60 nm, which was also confirmed by transmission electron microscopic (TEM) studies. Scanning electron microscopic (SEM) images depicted highly porous Bi2O3 NPs with little agglomeration. Utilizing diffused reflectance spectra (DRS) data, the energy bandgap ( E g ) value of 3.3 eV was deduced for Bi2O3 NPs, and their semiconductor behavior has been confirmed. Two dyes, methylene blue (MB) and acid green (AG) were utilized for degradation studies using Bi2O3 NPs under UV light irradiation (from 0 to 120 min). The photocatalytic degradation was found to be maximum for MB (93.45%) and AR (97.80%) dyes. Cyclic voltammetric (CV) and sensor studies using the electrochemical impedance spectroscopy (EIS) were performed. The specific capacitance value of 25.5 Fg-1 was deduced from the cyclic voltammograms of the Bi2O3 electrode in 0.1 N HCl with a scan rate of 10 to 50 mV/s. From the obtained EIS data, the Bi2O3 electrode showed pseudocapacitive characteristics. The prepared electrodes also exhibited high sensitivity towards the detection of ascorbic acid and lead. Hence, sonochemically synthesized Bi2O3 NPs are possibly hopeful for excellent photocatalytic and electrochemical sensing of biomolecules.

Green synthesis of metal oxide nanoparticles (NPs) is a viable alternative methodology because of cost-effective and availability of environmentally friendly templates for desired application, which has attracted the attention of researchers in recent years. In the present study, Co3O4 NPs were synthesized in various volume ratios in the presence of Solanum tuberosum leaf extract as a template. The synthesized Co3O4 NPs were characterized by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), surface area electron diffraction (SAED), UV-Vis diffuse reflectance spectroscopy (UV-DRS), and Fourier transform infrared (FTIR) spectroscopy. XRD analysis found that the average crystalline sizes for the 1 : 2, 1 : 1, and 2 : 1 volume ratios was 25.83, 21.05, and 27.98 nm, respectively. SEM-EDX and TEM analyses suggest that the green-synthesized Co3O4 NPs are spherical in shape without the presence of impurities. The band gap E g values of the 1 : 2, 1 : 1, and 2 : 1 volume ratios of Co3O4 NPs were found to be 1.83, 1.77, and 2.19 eV, respectively. FTIR analysis confirmed the presence of various bioactive ingredients within the leaf extract of Solanum tuberosum. Co3O4 NPs-modified electrodes showed better sensing capability towards ascorbic acid and citric acid due to enhanced electron transfer kinetics. Among three volume ratios (1 : 2, 1 : 1, and 2 : 1) of Co3O4 nanoelectrodes, 1 : 1 and 2 : 1 were identified as the best performing nanoelectrodes. This is possibly due to the high catalytic behavior and the more homogenized surface structure. Co3O4 (1 : 2) nanodrug showed the enhanced antibacterial activity (16 mm) towards S. aureus which is attributed to the formation of enhanced reactive oxygen species (ROS).

The synthesis of optoelectrically enhanced nanomaterials should be continuously improved by employing timeand energy-saving techniques. The porous zinc oxide (ZnO) and copper-doped ZnO nanocomposites (NCs) were synthesized by the time-and energy-efficient solution combustion synthesis (SCS) approach. In this SCS approach, once the precursor− surfactant complex ignition point is reached, the reaction starts and ends within a short time without the need for any external energy. The TGA−DTA analysis confirmed that 500 °C was the point at which stable metal oxide was obtained. The doping and heterojunction strategy improved the optoelectric properties of the NCs more than the individual constituents, which then enhanced the materials' charge transfer and optical absorption capabilities. The porosity, nanoscale crystallite size (15−50 nm), and formation of Cu/CuO-ZnO NCs materials were confirmed from the XRD, SEM, and TEM/HRTEM analyses. The obtained d-spacing values of 0.275 and 0.234 nm confirm the formation of ZnO and CuO crystals, respectively. The decrease in photoluminescence intensity for the doped NCs corroborates a reduction in electron−hole recombination. On the Mott−Schottky analysis, the positive slope for ZnO confirms the n-type character, while the negative and positive slopes of the NCs confirm the p-and n-type characters, respectively. A diffusion-controlled type of charge transfer process on the electrode surface was confirmed from the cyclic voltammetric analysis. Thus, the overall analysis shows the applicability of the less expensive and more efficient SCS for several applications, such as catalysis and sensors. To confirm this, an organic catalytic reduction reaction of 4-nitrophenol to 4-aminophenol was tested. Within three and a half minutes, the catalytic reduction result showed the great potential of NCs over ZnO NPs. Thus, the energy-and time-saving SCS approach has a great future outlook as an industrial pollutant catalytic reduction application.

Solution combustion was employed to create a series of ZrO2:Dy3+ (1-11 mol percent) nanoparticles (NPs) using oxalyl dihydrazide (ODH) as the fuel. ZrO2:Dy3+ NPs were subjected to calcination at about 700°C. ZrO2:Dy3+ NPs comprised of 1 to 11 mol% of Dy3+ were characterized by employing the X-ray diffraction (XRD), transmission electron microscopic (TEM), UV-visible, and X-ray photoelectron spectroscopic (XPS) techniques. The crystallite diameters of 1 to 11 mol% ZrO2:Dy3+ NPs were observed to range from 8.1 nm to 16.3 nm, exhibiting spherical shape. According to BET tests, the pore volume of ZrO2:Dy3+ NPs was determined to be 100.129 cm3/g. The mean pore diameter of ZrO2:Dy3+ NPs was determined to be 4.803 nm from the Barrett-Joyner-Halenda (BJH) plot. The photoluminescence and photocatalytic dye degradation properties of ZrO2:Dy3+ NPs were investigated. The acid red 88 (AR88) dye was applied to appraise the photocatalytic activities of the NPs under UV irradiation. ZrO2:Dy3+ NPs with 3 mol% Dy3+ exhibited improvised photocatalytic activity due to the operative departure of charge carriers. The electrochemical examination of ZrO2:Dy3+ NP modified carbon paste electrode in 0.1 N HCl demonstrated considerable redox potential output, as evidenced by cyclic voltammetric and amperometric measurements. The electrochemical sensor studies on ZrO2:Dy3+ NPs exhibited potentiality towards sensing of highly toxic metals like mercury and lead.