Photoluminescence and antibacterial performance of sol–gel synthesized ZnO nanoparticles

Abstract

The antibacterial performance and photoluminescence emission properties of ZnO nanoparticles have been investigated. The ZnO nanoparticles were synthesized using the sol–gel method, and subsequently, the sample was dried overnight at 100 °C and further annealed in air atmosphere at 350 °C for crystallization. The crystalline hexagonal phase of ZnO NPs was formed, as confirmed by X-ray diffraction results, and the obtained crystallite size was around 21 nm. The vibrational band of the prepared sample was examined using Fourier transform infrared spectroscopy. The crystalline ZnO nanoparticles exhibit an optical band gap of around 3.01 eV. The surface morphology of the sample was examined from SEM images and the phase purity was studied with EDS measurement. A strong band of PL emission was exhibited from the as-prepared sample in the visible region (512 nm). In contrast, after annealing, a PL emission band around 468.9 nm in the blue region was observed. Structural defects from the ZnO NPs may enhance PL emission properties. The antibacterial activity of synthesized sample was studied with the disc-diffusion method against Bacillus subtilis, Escherichia coli and Pseudonomas bacteria. Inhibition zones against bacteria were observed to be around 20 mm, 30 mm and 10 mm against E. coli, B. subtilis and Pseudonomas bacteria, respectively. Pure crystalline ZnO NPs were observed to be a more effective antibacterial agent against B. subtilis (gram-positive) bacteria compared to E. coli and Pseudonomas bacteria (gram-negative). The characteristic properties of PL emission in the visible region along with the effective antibacterial performance of the ZnO nanoparticles under an ambient light atmosphere are discussed, which have existing practical applications as a biomaterial and luminescent material.