Microwave assisted tuning of optical and magnetic properties of zinc oxide nanorods—efficient antibacterial and photocatalytic agent

Abstract

Microwave radiations play an important role in chemical reactions for reducing overall time and cost. The method has many advantages over conventional heating methods like phase purity, high crystallinity, enhanced reaction selectivity, narrow size distribution, energy saving, and high product yield. Microwave-assisted sol–gel route is used to prepare zinc oxide (ZnO) nanorods. X-ray diffraction results show peaks corresponding to Zn (OH)2 and ZnO at low microwave (MW) powers, i.e., at 136, 264, and 440 W. Whereas, increase in MW powers to 616 and 800 W results in dissociation of Zn (OH)2 to ZnO thus forming single-phase ZnO with wurtzite structure. The presence of absorption bands at 461 and 496 cm−1, in FTIR analysis, match to stretching modes of ZnO. Nanorods with diameter ~90 nm and with length of ~210 nm are observed in SEM micrographs at MW power of 800 W. Increased values of transmission (i.e., from 80.98 to 87.49%) are observed with the increase of MW powers from 136 to 800 W. Direct energy band gap of ZnO nanorods is observed in the range of 3.109–3.274 eV. Ferromagnetic behavior instead of diamagnetic nature of ZnO nanorods arises due to bound magnetic polarons (BMP) effect. At 800 W ZnO nanorods show high saturation magnetization (i.e., 0.104 emu/g). Antimicrobial activity is tested against B. Subtilis and E. Coli with 19 mm and 17 mm zone of inhibition, respectively. ZnO nanorods are found efficient photocatalyst for degradation of methylene blue (MB). It is worth to describe that combined optical and magnetic properties’ tuning is studied in this research work.