Bhavani P, Manikandan A, Paulraj P, Dinesh A, Durka M, Antony S Arul
PG and Research Department of Chemistry, Presidency College, Chennai 600005, Tamil Nadu, India.
Department of Chemistry, Bharath Institute of Higher Education and Research, Bharath University, Chennai 600073, Tamil Nadu, India.
J Nanosci Nanotechnol. 2018 Jun 1;18(6):4072-4081. doi: 10.1166/jnn.2018.15217.
Spinel ZnAl2O4 nano-catalysts were synthesized by a simple, economical and eco-friendly microwave irradiation (MIM) and conventional heating methods (CHM), using metal nitrates and Okra (Abelmoschus esculentus) plant extract, which play a dual role of both oxidizing and reducing nature. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray (EDX) and selected area electron diffraction (SAED) pattern results were confirmed that the samples have a single-phase cubic spinel structure with high crystalline nature of ZnAl2O4. Surface morphology of the samples was revealed by high resolution scanning electron microscopy (HR-SEM) and high resolution transmission electron microscopy (HR-TEM) techniques and they are confirmed particle-like structure with grain size below 50 nm. The optical band gap (Eg) was measured using Kubelka-Munk model by UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) and the Eg value is higher for MIM product than CHM, due to the smaller particle size of ZnAl2O4-MIM. The magnetic property of the samples was determined by vibrating sample magnetometer (VSM) and showed a superparamagnetic behavior. Spinel ZnAl2O4 nano-catalysts are magnetically recyclable and could be reused with no significant loss in catalytic activity. Both the samples were successfully tested as catalysts for the conversion of alcohols into respective carbonyl compounds using H2O2 (as oxidant) and acetonitrile (as a solvent) system. It was found that the ZnAl2O4-MIM nanocatalysts show best performance of conversion of alcohols into a carbonyl compounds than that of ZnAl2O4-CHM, due to the smaller particle size and higher surface area of ZnAl2O4-MIM samples.
采用简单、经济且环保的微波辐射（MIM）和传统加热方法（CHM），使用金属硝酸盐和秋葵（黄秋葵）植物提取物合成了尖晶石型ZnAl2O4纳米催化剂，该植物提取物具有氧化和还原双重性质。粉末X射线衍射（XRD）、傅里叶变换红外（FT-IR）光谱、能量色散X射线（EDX）和选区电子衍射（SAED）图谱结果证实，样品具有单相立方尖晶石结构，ZnAl2O4具有高结晶性。通过高分辨率扫描电子显微镜（HR-SEM）和高分辨率透射电子显微镜（HR-TEM）技术揭示了样品的表面形态，证实它们为粒径低于50 nm的颗粒状结构。使用Kubelka-Munk模型通过紫外可见漫反射光谱（DRS）和光致发光（PL）测量光学带隙（Eg），由于ZnAl2O4-MIM粒径较小，MIM产物的Eg值高于CHM产物。通过振动样品磁强计（VSM）测定样品的磁性，结果显示出超顺磁性行为。尖晶石型ZnAl2O4纳米催化剂具有磁可回收性，可重复使用且催化活性无明显损失。使用H2O2（作为氧化剂）和乙腈（作为溶剂）体系，对这两种样品作为将醇转化为相应羰基化合物的催化剂进行了成功测试。结果发现，由于ZnAl2O4-MIM样品粒径较小且表面积较大，ZnAl2O4-MIM纳米催化剂在将醇转化为羰基化合物方面表现出比ZnAl2O4-CHM更好的性能。
