Room Temperature Syntheses of ZnO and Their Structures

Abstract

ZnO has many technological applications which largely depend on its properties, which can be tuned by controlled synthesis. Ideally, the most convenient ZnO synthesis is carried out at room temperature in an aqueous solvent. However, the correct temperature values are often loosely defined. In the current paper, we performed the synthesis of ZnO in an aqueous solvent by varying the reaction and drying temperatures by 10 °C steps, and we monitored the synthesis products primarily by XRD). We found out that a simple direct synthesis of ZnO, without additional surfactant, pumping, or freezing, required both a reaction (TP) and a drying (TD) temperature of 40 °C. Higher temperatures also afforded ZnO, but lowering any of the TP or TD below the threshold value resulted either in the achievement of Zn(OH)2 or a mixture of Zn(OH)2/ZnO. A more detailed Rietveld analysis of the ZnO samples revealed a density variation of about 4% (5.44 to 5.68 gcm−3) with the synthesis temperature, and an increase of the nanoparticles’ average size, which was also verified by SEM images. The average size of the ZnO synthesized at TP = TD = 40 °C was 42 nm, as estimated by XRD, and 53 ± 10 nm, as estimated by SEM. For higher synthesis temperatures, they vary between 76 nm and 71 nm (XRD estimate) or 65 ± 12 nm and 69 ± 11 nm (SEM estimate) for TP =50 °C, TD = 40 °C, or TP = TD = 60 °C, respectively. At TP = TD = 30 °C, micrometric structures aggregated in foils are obtained, which segregate nanoparticles of ZnO if TD is raised to 40 °C. The optical properties of ZnO obtained by UV-Vis reflectance spectroscopy indicate a red shift of the band gap by ~0.1 eV.

Metal Organic Framework-Derived ZnO@GC Nanoarchitecture as an Effective Hydrogen Gas Sensor with Improved Selectivity and Gas Response

“…For further illustration, their corresponding unit cell of the cubic ZnO structure (m3m) is provided in the inset of Figure b. These observations are in concordance with an earlier report …”

“…As the temperature increases (550–750 °C), the crystallite size and crystallinity of the samples improve considerably. Additionally, the peaks broadening with temperature increment might be ascribed to the lattice deformation, crystalline domain size, extended defects, and so forth. , In particularly, the d -spacing values of the (0 0 2) and (1 0 1) planes are significantly enhanced with an increase in temperature. For further illustration, their corresponding unit cell of the cubic ZnO structure (m3m) is provided in the inset of Figure b.…”

Preparation of Novel Triangular Prism e -Zn(OH)2 by the Facile Precipitation Route for the Photocatalysis Under Visible Light

“…The ε-Zn(OH) 2 material was single phase with orthorhombic structure in accordance with reported data JCPDS card No. 38-0385 (10) . Furthermore, diffraction peaks were sharp, and no impurity peaks demonstrated high crystallinity.…”

NiO-Based Electronic Flexible Devices

“…Transition metal oxides and particularly NiO have the advantage of high storage capacitance [52], optical and electrical properties [53], transport properties on surfaces [54] as well as in perovskite solar cells [55]. Their nanoparticles synthesis may be achieved in several, environmentally friendly ways [56][57][58][59][60][61][62][63], with several shapes, arrangements, and super-structures [64]. Depending on the specific size and morphological characteristics, they can be employed in the construction of several types of devices for different purposes, which include chemosensing [65][66][67][68], supercapacitive devices [69][70][71], solar cells [72,73], and resistive memories [74][75][76].…”