Room Temperature Syntheses of ZnO and Their Structures (original) (raw)

Room Temperature Syntheses of ZnO and Its Structure

2021

ZnO has many technological applications which largely depend on its properties that can be tuned by controlled synthesis. Ideally, the most convenient ZnO synthesis is carried out at room temperature in aqueous solvent. However, the correct temperature values are often loosely defined. In the current paper we performed synthesis of ZnO in aqueous solvent, by varying reaction and drying temperature by 10°C steps and monitored the synthesis products primarily by XRD. We found out that a simple direct synthesis of ZnO, without additional surfactant, pumping of freezing, required both a reaction (TP) and a drying (TD) temperature of 40°C. Higher temperatures also afford ZnO, but lowering any of the TP or TD below the threshold value results either in the achievement of Zn(OH)2 or in a mixture of Zn(OH)2/ZnO. A more detailed Rietveld analysis of the ZnO samples reveals a density variation with the synthesis temperature and an increase of the nanoparticles average size also verified by SE...

A Review: ZnO -From Synthesis to Application

Many efforts are taken on oxide nanostructures over the last twenty years thanks for large number of applications. ZnO thin film is one among the II-VI compound semiconductors and it is composed of hexagonal wurtzite crystal structure. ZnO based nanostructures have gained remarkable attention worldwide for the sensing, photo sensing, behaviour as a semiconductor metal oxide in several industries. The main motivation of this thematic review is to research the various deposition techniques of pure and doped oxide nanostructures, and their application in sensing field. This review summarizes the various deposition techniques and main chemical route utilized in the solgel synthesis of ZnO thin film and highlights the study of various characterizations. Finally, a large range of uses of ZnO nanostructures in various applications in photo sensing, gas sensing, humidity sensing, and glucose sensor are highlighted during this article.

Temperature Dependence on Structural Properties of Liquid Phase Synthesized ZnO

Advanced Nano Research

Transparent conducting oxide material, ZnO nanoparticles has been synthesized using inexpensive and eco-friendly synthesis procedures with less or environmental pollutants and no liquid waste products. The effect of the temperatures on the structural properties for the synthesized ZnO nanocrystals has been investigated. In this study, we report an easy, low-cost, re-producible method for synthesizing ZnO nanoparticles by means of the liquid phase method. The ZnO nanocrystals were synthesized using the wet chemical route and the effect of temperature variation on the structural properties of investigated synthesized using powder x-ray diffractogram (XRD). The temperatures for the synthesis were varied from 120 °C to 200 °C in steps of 20 °C. The results show that, during the first stage of the synthesis of ZnO (at 120 °C), the XRD diffraction pattern confirms the cubic structure of zinc peroxide and the XRD pattern of the samples obtained at temperatures of 140 °C, 160 °C, 180 °C and...

Water-based wet chemical synthesis of (doped) ZnO nanostructures

Journal of Sol-Gel Science and Technology, 2006

Looking at its vast range of applications, nanostructured ZnO can be considered as a key technological material. Simple and ecological production techniques for this and other nanostructured materials can boost the detection of their unusual properties. In this context water-based wet chemical synthesis routes for nanostructured ZnO are explored in this study. The advantages and disadvantages of controlled double-jet precipitation, microemulsion preparation, hydrothermal synthesis and an aqueous solution-gel route are described for the formation of (doped) ZnO nanoparticles. The influence of the synthesis parameters on the particle size, size distribution and degree of agglomeration of the particles is reported. Thin films are prepared by chemical solution deposition from aqueous solution. The heat treatment profile and the precursor composition are seen to largely control the density, the grain size and the degree of preferential c-axis orientation.

The influence of methanol and NH4Cl on solvothermal ZnO synthesis and properties

Applied Physics A, 2020

Powders composed of ZnO sub-microspheres were obtained in two stages: solvothermal synthesis and thermal annealing at 125, 300, 450 or 600ºC in atmospheric conditions. The synthesis was carried out with methanol as solvent, zinc acetate dihydrate as Zn 2+ source and ammonia chloride as complexing agent. The as-grown and annealed samples were studied through photoluminescence, microRaman and reflectance spectroscopies, scanning electron microscopy and X-ray diffraction (XRD). After the solvothermal synthesis stage, a white precipitate was obtained composed of a flower-like multiphase assembly of layers identified mainly as a layered basic zinc salts (LBZS) and Zn(NH 3) 2 Cl 2. After the annealing treatments, the LBZS and Zn(NH 3) 2 Cl 2 transformed into ZnO, while the powder morphology changed from the layered flower-like to polycrystalline ZnO spherical particles with sub-micrometer diameters. With increasing annealing temperature, the ZnO spheres size remained unchanged, while the mean crystallite size and wurtzite lattice parameters decreased as a result of tensile stress relaxation. Concomitantly, a blueshift of the defect-related ZnO emission was observed. The combined analysis of emission, vibrational and reflectance spectra and XRD suggests that the annealing treatments result in the formation of ZnO crystallites with oxygen vacancies and oxygen vacancy-zinc interstitial complexes whose densities increase as the annealing temperature increases. The results and analysis reported in this work contribute to the understanding of growth mechanisms relevant for the tailoring of ZnO powder properties through solvothermal synthesis in non-aqueous media.

Morphology-controlled synthesis of ZnO structures by a simple wet chemical method

Zinc oxide particles were synthesized by a simple wet chemical method. Using zinc nitrate and various precipitating agents, like KOH, NaOH and (CH 2) 6 N 4 , particles with different morphologies were obtained. Also, the addition of a structure-directing agent, like gum arabic-a highly branched biopolymer, leads to a decrease in the ZnO particles size (for KOH and NaOH) and to a dramatical change of the ZnO particle shape in the case of (CH 2) 6 N 4. The X-ray diffraction analysis showed that all obtained samples are of wurtzite structure. The reflectance and photoluminescence spectra have been used to investigate the optical properties of the ZnO structures. The morphologies observed by scanning electron microscopy reveal snowflake-like, flower-like, star-like and double-raspberry-like structures. A possible formation mechanism for ZnO micro/nanostructures with different morphologies was proposed. The biopolymer-assisted crystallization method could provide a facile approach to synthesize other desired compounds with controllable morphology.

Simple chemical synthesis of novel ZnO nanostructures: Role of counter ions

Solid State Sciences, 2014

This article reports the synthesis, characterisation and photocatalytic activity of novel ZnO nanostructures prepared via the thermal decomposition of hydrozincite. Hydrozincites were obtained by the conventional precipitation route using different zinc salts such as acetate, nitrate, chloride and sulphate. The effect of counter ions (CH 3 COO À , Cl À , NO 3 À , and SO 4 2À) on the structural, textural, morphological and optical properties was investigated. Various characterisations depicted the active role of counter ions in the properties of ZnO. Hexagonal wurtzite structure of ZnO with fine crystalline size was obvious from the XRD results, irrespective of the counter ions. Electron microscopic images indicated the role of counter ions in the surface and internal morphology of ZnO nanomaterials. Special coral like agglomerated morphology of elongated particles with high porosity was observed for the ZnO prepared from acetate precursor. Spherical, elongated and irregular shaped bigger lumps of ZnO nanoparticles with various novel morphologies were resulted for the sulphate, nitrate and chloride precursors respectively. Highly ordered porous micro disc like morphology was noted for the ZnO samples prepared from the sulphate and nitrate salts. Photoluminescence spectra showed the characteristic blue and green emission bands, depicting the presence of large crystal defects and high oxygen vacancies in the samples. Photocatalytic activity of the as-prepared ZnO catalysts was examined by the degradation of methylene blue under UV light irradiation. Degradation results indicated their substantial activity with respect to the counter ions. ZnO prepared from the acetate precursor showed highest photoactivity due to its high surface area, special morphology and high oxygen vacancies.

CHEMI-THERMAL METHOD OF SYNTHESIS OF ZnO NANOMATERIAL AND ITS CHARACTERIZATION

Indian J.Sci.Res., 2017

Present study reports of synthesis of better yield ZnO nanomaterial by chemi-thermal route and its characterization. Characterization of zinc oxide powder was analyzed by using UV-Visible Spectroscopy, SEM and EDX. The absorption spectrum was found to be at 369nm and its band energy about 3.9 eV. SEM results showed aggregated pebble like morphology with average size about 100 nm at high magnification. EDX results showed the presence of major amount of Zn 2+ and O 2-elements with respect to ZnO molecule by both weight and atomic percentage. Therefore, this method can be used as an alternative for other chemical synthesis method aimed at various applications. KEYWORDS: Chemi-thermal, Sodium lauryl sulphate, Simple and robust method, ZnO nanomaterial. The unique properties of nanomaterials such as quantum size effect, surface to volume ratio, modifications in surface morphology etc., attracted researchers to work on nanomaterial fabrication for applications in different areas [1,2]. Although there are numerous types of nanomaterials available, nanomaterial of metal oxides continuously made good progress in the field of nanotechnology because metal element has high compatibility with oxygen and develop stable compound which shows several geometrical forms leads to change in band gap and binding energy of particular structure [3]. Due to energy change and nanodimensional metal oxide materials acquire superior electronic properties and high density on edge surface sites respectively [4] compare to their bulk counterparts. Amongst all other metal oxides, zinc oxide nanomaterial attracts a greater attention because of its physical, chemical and biological properties. Fundamentally, Zinc oxide is a heterogeneous semiconductor n-type compound found in two main stable forms viz. wurtizite with hexagonal crystalline structure and zinc-blende with cubic crystalline structure where, anionic zinc atoms covalently bonded (Sp3 Hybridization) with four cationic oxygen atoms (tetrahedron) and eventually formed tetrahedral structure (Figure 1.) [5]. Further research showed ionic bonding in ZnO added an extra energy to increase the band gap up to 3.37eV at room temperature with quite large exciton binding energy of 60 meV [4,6]. Depending on requirements and applications, ZnO nanomaterial can be synthesized by physical and/or chemical methods. Physical methods are usually top down approach of synthesis includes thermal reduction [7-8] thermal evaporation [9] laser ablation [10] UV irradiation [11] etc., gives high yield of pure material since, no other chemical additives involved in it. Compared to physical method, chemical synthesis includes hydrothermal [12-15] sol-gel method [16-18] microwave irradiation [19-21] solvothermal method [22-24] Electro-chemical method [25] etc., are cost effective, simple and robust, but gives material with some impurities. Figure 1: Crystal structure of ZnO wurtizite [Left] ZnO-zinc blende [Right] [5] Generally, ZnO nanostructures shows improved chemical, physical, mechanical, electrical properties, biological activity [11,26-32] and hence in present study proposed the chemi-thermal method of synthesis of ZnO nanomaterials for better yield. MATERIALS AND METHODS Chemicals All the bulk chemicals, solvents used in this study were analytical grade and purchased from suppliers including SRL chemicals and Qualigenes India. Synthesis of ZnO nanomaterial 100 mM of Zn(CH 3 COO) 2 were dissolved in 50mL of DI water by continuous steering on magnetic stirrer at 210 0 C for 30 minutes. Drop wise addition of

Preparation of various morphologies of ZnO nanostructure through wet chemical methods

Advanced Material Science, 2019

Hydrothermal route and solution reaction method are adopted for the synthesis of zinc oxide (ZnO) nanopowders having four different morphologies such as nanoparticle, mirorod, nanoplate and nanotubule. Zinc nitrate hexahydrate Zn(NO 3) 2 .6H 2 O was used as precursor for ZnO nanostructures. ZnO nanorods and nanoplates were synthesized by a hydrothermal approach using KOH as reaction chemical. ZnO nanotubes were obtained by a chemical reaction of Zn(NO 3) 2 and NH 4 OH. And ZnO nanoparticles were prepared by precipitation method from zinc nitrate and ammonium carbonate (NH 4) 2 CO 3 in aqueous solution. The structures, morphology, and element components of these ZnO products fabricated by the above-mentioned methods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These experimental results demonstrated that the as-prepared ZnO nanoparticles have average diameter of 30-60 nm; rod-like ZnO has average diameter of about 350 nm and the length of 3.5 µm; plate-like ZnO has average thickness of about 40 nm and lateral size of 200 × 400 nm; ZnO nanotubules have outer diameter of about 400 nm and inner diameter of about 300 nm, the length of about 4 µm. The XRD results indicated that four morphologies of ZnO are all wurtzite structure. It is found that the wet chemical technique is very promising for fabricating ZnO nanocrystallines with various morphologies.

ZnO Nanocrystals by a Non-hydrolytic Route: Synthesis and Characterization

The Journal of Physical Chemistry B, 2003

We report a novel, non-hydrolytic route to ZnO nanocrystals by means of thermal decomposition of zinc acetate (ZnAc 2 ) in alkylamines, in the presence of tert-butylphosphonic acid (TBPA). The slow heating of an alkylamine/TBPA/ZnAc 2 mixture is a simple, safe, and scalable approach to synthesize ZnO nanocrystals from handy chemicals. The obtained ZnO nanocrystals were characterized by UV-vis absorption, photoluminescence (PL) and infrared (FT-IR) spectroscopies, and by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The growth of ZnO particles in the nanoscopic regime and their final size were governed by the TBPA/ZnAc 2 molar ratio in the reaction mixtures. The various roles played by TBPA in the conditions of the synthesis are discussed on the basis of the experimental evidence. The presented synthetic approach provides a unique tool for designing the synthesis of ZnO crystals of a desired size in the nanoscale regime and can be potentially extended to other nanoscale materials.