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Nanocrystalline ZnO-Based Microfabricated Chemical Sensor
Published in Sunipa Roy, Chandan Kumar Sarkar, MEMS and Nanotechnology for Gas Sensors, 2017
Sunipa Roy, Chandan Kumar Sarkar
Undoped nanocrystalline n-ZnO thin films are deposited on the active area by a low-cost, low-temperature chemical deposition technique. The sodium zincate can be prepared by mixing zinc sulphate (ZnSO4, 7H2O) and sodium hydroxide (NaOH) in the ratio of (1:3) in aqueous solution and stirring at room temperature. () Zn(SO4)+2NaOH=Zn(OH)2+Na2SO4 () Zn(OH)2+2NaOH=Na2ZnO2+2H2O () ZnSO4+4NaOH=Na2ZnO2+Na2SO4+2H2O
Photosensing effect of indium-doped ZnO thin films and its heterostructure with silicon
Published in Journal of Asian Ceramic Societies, 2022
Kathalingam Adaikalam, S. Valanarasu, Atif Mossad Ali, M. A. Sayed, Woochul Yang, Hyun-Seok Kim
We used analytical grade chemicals to coat In-doped and undoped ZnO thin films on glass and p-type silicon substrates. Before coating, the substrates were cleaned using soap solution well, DI water, and acetone with ultrasonication; thereafter, they were dried with N2 gas blowing. The undoped ZnO thin films were deposited by dipping the substrates alternately in sodium zincate (Na2ZnO2) solution and hot water baths maintained at room temperature and near-boiling temperatures, respectively. For the growth of In-doped ZnO, indium chloride (InCl3) was added with the sodium zincate bath. The cationic precursor – sodium zincate solution – for the deposition was prepared by adding 0.1 M zinc sulfate (ZnSO4) and 1 M NaOH to grow undoped ZnO. Whereas, different concentrations of indium chloride (0, 2.5, 5, and 7.5 wt%) was added with the sodium zincate solution to grow In-doped ZnO. After cleaning and drying, the substrate was immersed first in a sodium zincate bath for 20 s and then transferred to hot water. This immersion process was continued 100 times to build the thickness of the film after drying the substrate at each cycle using a hot air jet. A thin layer of sodium zincate complex was produced when the substrate was dipped into the sodium zincate bath. The sodium zincate complex was then decomposed into ZnO while dipping it in a hot water bath.
Effect of pH values on the solubility of some elements in different soil samples
Published in Chemistry and Ecology, 2019
M. E. Soltan, A. S. Al-ayed, M. A. Ismail
Soil contamination by heavy metals has been an increasingly severe threat to nature environment and human health. Efficient investigation of contamination status is essential to soil protection and remediation. The concentrations of metallic elements (Table 1) extracted under the influence of different pH values from the studied soil samples. The results show high concentrations of metallic elements in the acidic medium at pH 2 (Cd; 8.25–2.23 µg g−1, Pb; 15.9–7.5 µg g−1, Zn; 31.25–19.88 µg g−1, in sewage and agricultural soils, respectively), while the concentrations decrease as the pH rises until to reach the neutral medium (Cd; 0.76–0.47 µg g−1, Pb; 1.53–1.56 µg g−1, Zn; 4.75–3.13 µg g−1, in sewage and agricultural soils, respectively). The decrease of concentrations are very clear in the alkaline medium and reach the lowest values at pH10(Cd; 0.53–0.11 µg g−1, Pb; 0.63–0.54 µg g−1, Zn; 2.88–2.25 µg g−1, in sewage and agricultural soils, respectively)., this is due to the low solubility of the metal hydroxide, while a relative increase in concentrations is observed at pH 11.5. This is due to the formation of dissolved compounds in the high alkali medium (sodium zincate Na2ZnO2 and sodium plumbite Na2PbO2). The decrease in soil pH affects the extractability of metals in soils owing to the decrease in metal adsorption and/or precipitation, and thus the metal solubility of metal minerals increased with decreasing pH values.