Solanum torvum Derived Zirconium Oxide Nanoparticles as Fluorescent Sensors and Photocatalysts

ZrO₂ nanoparticles were biosynthesized using Solanum torvum fruit extract. Their structural and morphological properties were investigated through UV–visible studies, photoluminescence, Fourier transform infra-red spectroscopy, energy-dispersive X-ray analysis, X-Ray diffraction, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. O²⁻→Zr⁴⁺ transition was confirmed by the peak observed at 222 nm in UV–visible spectrum and the band gap was estimated as 4.46 eV, indicating dielectric nature. Zr─O─Zr bond was confirmed by the bands observed at 738 and 613 cm⁻¹ in FTIR spectroscopy. EDX spectra showed characteristic peaks of oxygen and zirconium. XPS showed binding energies of 182.7 and 184.9 eV, which correspond to spin-orbit splitting of Zr 3d_5/2 and Zr 3d_3/2, respectively. The absence of metallic zirconium was confirmed by the absence of peaks at 178.7 and 181.1 eV, which also confirmed that Zr is present in +4 state. The particle size was determined to be 13 and 17 nm using XRD and TEM, respectively. Effective fluorescence sensing of L-glycine was observed with a detection limit 1.27 × 10⁻⁸ M. Photocatalytic reduction of 2,4-dinitrophenylhydrazine showed 87.6% conversion and reusability of the catalyst up to five consecutive cycles. Cytotoxicity studies using A549 human lung cancer cell line showed IC₅₀ value of 225 µg/mL.