Seed Extract-mediated Cu-Doped TiO₂ Nanoparticles: Linking Morphological Evolution with Optical and Antibacterial Properties
J. Environ. Nanotechnol., Volume 15, No 3 (September 2026) pp. 83-92
Abstract
Green synthesis of semiconductor nanomaterials offers a sustainable approach for developing functional materials with enhanced physicochemical properties. In this study, Cu-doped(1wt%) TiO2 nanoparticles were synthesized through a modified sol-gel method using extracts of five different plant seeds, namely Papaya, Bitter gourd, Gokshura, Drumstick and Tamarind as natural reducing and capping agents. Each of these garden seeds, found in plenty in Indian households, is rich in different types of phytochemicals. The study here shows the implicit relation between the influence of various phytochemicals on the structural and functional properties of biosynthesized nanoparticles. This comparison shows how each bio compound differently influences the synthesis process, which lies at the novelty of the study. The influence of seed-derived phytochemicals on the morphological, optical and antibacterial properties of the nanoparticles was systematically investigated. X-ray diffraction confirmed the formation of phase-pure anatase TiO2 with crystallite sizes ranging from 8.1 to 10.4 nm. This indicates the different capping capacity of different plant extracts, while SEM revealed extract-dependent variations in particle morphology and porosity. EDX analysis verified Cu presence, and FTIR confirmed the presence of residual phytochemicals acting as surface stabilizers. Diffuse reflectance spectroscopy demonstrated indirect optical band-gap energies between 2.63 and 3.09 eV, indicating enhanced visible-light absorption compared with pristine TiO2, keeping similar doping conditions. The PL spectra exhibited a marked decrease in emission intensity, indicating suppressed electron–hole recombination. The combined observations suggest that Cu doping and phytochemicalassisted green synthesis may have introduced defect or intermediate energy states that facilitate charge separation while simultaneously extending visible-light absorption. The Sd sample exhibited the lowest band gap (2.63 eV), suggesting superior bandgap tuning, whereas the St sample showed the highest band gap (3.09 eV). All synthesized nanoparticles exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus, with Sp showing the highest inhibition against E. coli (12.7 ± 0.14 mm) and Sg against S. aureus (11.0 ± 0.28 mm). The study demonstrates that seed phytochemistry provides an effective route for fabricating Cu-doped TiO₂ nanomaterials with controlled crystallite size and reduced band gap, which thereby foster their antibacterial activity against Gram-negative and Gram- positive bacteria.
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