Enhanced photocatalytic and antimicrobial properties of titanium doped tin dioxide quantum dots for industrial wastewater treatment

Abstract

Pure SnO₂ quantum dots (SnQ) and Ti-doped SnO₂ quantum dots (SnQT) were synthesized via a facile one-step hydrothermal method (ESOSH) and characterized their structures and properties (XRD, FTIR, HRTEM, UV-DRS). The SnQ samples (thermally treated at 290 °C and 490 °C as SnQ1 and SnQ2, respectively) had crystalline sizes of ∼ 4 nm and ∼ 9 nm, serving as baseline materials, while titanium incorporation (Sn_0.97Ti_0.03O₂ and Sn_0.93Ti_0.07O₂ for SnQT1 and SnQT2) modulated the SnO₂ lattice without introducing secondary phases. Ti doping substantially enhanced the optical and catalytic performance: SnQT1 exhibited a narrowed band gap (∼3.3 eV) and achieved the highest photocatalytic activity, degrading a model organic dye under simulated sunlight at a rate significantly faster than both the undoped SnQ and the higher-doped SnQT2 catalysts. SnQT1′s dye degradation rate constant was roughly three times that of SnQT2, highlighting the improved charge-carrier separation and extended light absorption due to Ti doping​file-dhfkdtnsslcarpbj5mucvs. SnQT1 was also the most cost-efficient catalyst, with an estimated treatment cost of $25.67 per 1000 m3 of dye solution, outperforming the other compositions in economic analysis. Moreover, Ti-doped samples demonstrated superior antimicrobial efficacy: all catalysts inhibited Bacillus subtilis (Gram-positive) and Candida albicans (yeast), with SnQT1 showing the strongest antibacterial activity. This study underscores that titanium doping in SnO₂ quantum dots yields doped quantum-dot photocatalysts with superior performance, providing valuable insights for designing high-efficiency, sustainable nanomaterials for wastewater treatment and disinfection applications.