Synthesis of low-band gap porous zirconia nanoparticles via greener-route: Mechanistic investigation and their applications

Zirconia nanoparticles are one of the significant metal oxide nanoparticles, due to their diverse applications in biomedical science such as dentistry, drug delivery, and catalytic science. Among the various synthetic methods employed for the preparation of nanoparticles (NPs), the greener plant-mediated route is anticipated to be the simplest and most economically viable pathway. In the present work, spherical zirconia nanoparticles were successfully synthesized by mixing a solution of zirconium oxychloride octahydrate and extract of green tea leaves followed by heating at 90 °C, drying at 120 °C, and finally calcining at 550 °C for 4 h. The prepared material was characterized by both spectroscopic and microscopic techniques and was found to be crystalline in nature and exhibited both monoclinic and tetragonal phases. The obtained XRD data were further verified through the Rietveld refinement method. The refinement confirmed that the prepared sample has tetragonal and monoclinic phases in 62.66 and 37.34% with space groups P 42/nmc and P121/c1, respectively. Furthermore, microscopic studies reveal the formation of polygonal nanoparticles having size of ∼7 nm. Interestingly, the values of crystallite and particle sizes were found to be in contrast to each other. In order to gain a mechanistic understanding of the pathway followed in the preparation and stabilization of the zirconia nanoparticles via the organic components of tea extracts, theoretical studies were performed. The prepared zirconia nanoparticles were evaluated for their photocatalytic and antimicrobial activity against five different pathogenic bacteria. These studies would find applications in pharmacy, the biomedical field, and photocatalysis.