Rational development of Pt-decorated Se-TiO₂@CNT nanocomposite for light-driven antibacterial activity and growth-promoting effects against tomato

This study presents the synthesis of a novel nanocomposite, denoted as Pt/Se-TiO₂@CNTs, which comprises platinum (Pt)-decorated selenium-doped titanium dioxide (Se-TiO₂) supported on functionalized carbon nanotubes (FCNTs). The synthesis was performed using a sol-gel method, facilitating the in-situ decoration of platinum nanoparticles (NPs) for uniform dispersion and robust interfacial connections. Characterization techniques, including X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy equipped with Energy Dispersive Spectroscopy (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, UV–visible spectroscopy, and X-Ray Photoelectron Spectroscopy (XPS), confirmed the incorporation of Se into the TiO₂ and the successful decoration of Pt, along with enhanced optical absorption in the visible spectrum. The nanocomposite functioned as an effective photocatalyst, achieving a 95.4% degradation of indigo carmine dye within 120 min. In vitro experiments showed that the nanocomposite at a concentration of 300 µg/L demonstrated 85% colony growth inhibition of Ralstonia solanacearum at various time intervals (20, 40, 60, 80, 100, 120, and 140 h) under visible light, indicating significant photocatalytic antibacterial activity. The nanocomposite was then applied to tomato plants via foliar spray at concentrations of 100, 200, and 300 mg/L, with the 300 mg/L concentration proving most effective in mitigating bacterial wilt disease, thus enhancing physiological and morphological parameters including fresh weight (19.70 g), dry weight (3.36 g), shoot length (30.40 cm), root surface area (25.26 cm), and plant length (33.90 cm). Furthermore, it improved total chlorophyll (2.10 mg/g) and carotenoid contents (1.85 mg/g) at this concentration. The biochemical application also significantly elevated antioxidant enzyme activities like superoxide dismutase (SOD) (74 mg/g), peroxidase (POD) (22.6 mg/g), catalase (CAT) (26.9 mg/g), and ascorbate peroxidase (APX) (21.7 mg/g), along with increased phenolic and flavonoid contents. This research highlights the potential of Pt-decorated Se-TiO₂@CNTs nanocomposites for effective antibacterial applications against plant pathogens and their environmental degradations.