Synthesis of ZnO nanoparticles using a modified polymer complex method and evaluation of their biological effect on Capsicum annuum L

Abstract In this work, zinc oxide nanoparticles (ZnO-NPs) were synthesized using a chemical route. The ZnO obtained was characterized using infrared and Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the synthesized ZnO had a unique crystal structure corresponding to the wurtzite type. The primary particles of the synthesized oxide had a size < 100 nm, a crystallite size of ~ 33.20 nm and spheroidal morphology. These primary particles formed agglomerates with an average size of ~ 460 nm. The bandgap values of the synthesized ZnO were between ~ 2.7 and 2.8 eV, with an Urbach energy of ~ 340 meV. Considering the potential use of synthesized ZnO-NPs and commercial ZnO (ZnO-MPs) in agriculture, seeds of C. annuum were exposed to treatments at concentrations of 0, 10, 20, 50, 100 and 200 mg L −1 of ZnO-NPs or ZnO-MPs to determine their biological effect. A relevant result was the decrease in the dry weight of the plumule, in the proportion indicated in parentheses, of the seedlings obtained from seeds exposed to ZnO-NPs, in concentrations of 10 mg L −1 (15%), 20 mg L −1 (17%) and 200 mg L −1 (13%), or treated with ZnO-MPs, in concentrations of 10 mg L −1 (19%) and 100 mg L −1 (13%). These treatments could cause toxicity in the seedling since the reduction in the recorded dry weight was equal to or greater than 10%, a percentage considered as a benchmark for the critical level of toxicity.