Prakash Anand, Bahadur D
Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai - 400 076, India.
Phys Chem Chem Phys. 2014 Oct 21;16(39):21429-37. doi: 10.1039/c4cp03583f. Epub 2014 Sep 3.
This paper reports the influence of surface defects on the photocatalytic degradation of methylene blue (MB) for zinc oxide (ZnO) nanocrystals (NCs) synthesized in different organic solvents. A simple chemical approach has been adopted for the promotion of oxygen vacancies in pristine ZnO using solvents namely dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and dimethylsulfoxide (DMSO). This alters the growth of NCs through the promotion of oxygen vacancies depending on the fact that the solvent with minimum viscosity supports faster nucleation and growth exhibiting maximum surface defects. DMF with minimum viscosity results in largest particle size and superior photocatalytic activity. Further, X-ray diffraction, UV-visible reflectance spectroscopy and transmission electron microscopy confirm that the DMF supports the faster growth of NCs as compared to NMP and DMSO. Electron paramagnetic resonance, Raman, X-ray photoelectron, and photoluminescence spectroscopies confirm different states of oxygen vacancies in the NCs and their dependence on the nature of solvents. The photocatalytic activities of these NCs were investigated against the degradation of MB as a model dye. The results show that the oxygen defects at the surface of NCs are more responsible for higher photocatalytic activity than the specific surface area of NCs. The electrochemical investigations of MB degradation suggest that these defects upon interaction with MB influence the storage capacity and charge-discharge profiles of NCs. During degradation, MB passivates these defects, which has been explained in terms of increased charge-discharge time and storage capacity.
本文报道了表面缺陷对在不同有机溶剂中合成的氧化锌（ZnO）纳米晶体（NCs）光催化降解亚甲基蓝（MB）的影响。采用一种简单的化学方法，利用二甲基甲酰胺（DMF）、N-甲基-2-吡咯烷酮（NMP）和二甲基亚砜（DMSO）等溶剂促进原始ZnO中的氧空位。这根据最低粘度的溶剂支持更快的成核和生长从而表现出最大表面缺陷这一事实，改变了NCs的生长。粘度最低的DMF导致最大的粒径和优异的光催化活性。此外，X射线衍射、紫外-可见反射光谱和透射电子显微镜证实，与NMP和DMSO相比，DMF支持NCs更快地生长。电子顺磁共振、拉曼光谱、X射线光电子能谱和光致发光光谱证实了NCs中氧空位的不同状态及其对溶剂性质的依赖性。以MB作为模型染料研究了这些NCs的光催化活性。结果表明，NCs表面的氧缺陷比NCs的比表面积对更高的光催化活性更具决定性作用。MB降解的电化学研究表明，这些缺陷与MB相互作用时会影响NCs的存储容量和充放电曲线。在降解过程中，MB使这些缺陷钝化，这已根据充放电时间和存储容量的增加进行了解释。
