SnO2 Nanoparticles for Sensing and Bone Regeneration Application: Wet-Chemical and Plant-Based Green Synthesis, Spectroscopic Characterization, Photocatalytic, and SERS Activities

This study presents the synthesis and comprehensive characterization of tin dioxide nanoparticles (SnO2NPs). SnO2NPs were obtained using a conventional wet-chemistry route and an environmentally friendly green-chemistry approach employing plant extracts from rooibos leaves (Aspalathus linearis), pomegranate seeds (Punica granatum), and kiwifruit peels (family Actinidiaceae). The thermal stability and decomposition profiles were analyzed by thermogravimetric analysis (TGA), while their structural and physicochemical properties were investigated using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS), Raman spectroscopy, and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Transmission electron microscopy (TEM) confirmed the nanoscale morphology and uniformity of the obtained particles. The photocatalytic activity of SnO2NPs was evaluated via the degradation of methyl orange (MeO) under UV irradiation, revealing that nanoparticles synthesized using rooibos extract exhibited the highest efficiency (68% degradation within 180 min). Furthermore, surface-enhanced Raman scattering (SERS) spectroscopy was employed to study the adsorption behavior of L-phenylalanine (L-Phe) on the SnO2NP surface. To the best of our knowledge, this is the first report demonstrating the use of pure SnO2 nanoparticles as SERS substrates for biologically active, low-symmetry molecules. The calculated enhancement factor (EF) reached up to two orders of magnitude (102), comparable to other transition metal-based nanostructures. These findings highlight the potential of SnO2NPs as multifunctional materials for biomedical and sensing applications, bridging nanotechnology and regenerative medicine.