Highly efficient Ti3+ self-doped TiO2 co-modified with carbon dots and palladium nanocomposites for disinfection of bacterial and fungi

High efficiency photocatalysts capable of disinfecting a broad-spectrum microorganisms are needed for the practical application of photodisinfection technology. Herein, we synthesized a highly efficient photodisinfection catalyst composed of Ti3+ self-doped TiO2 decorated with carbon dots (CDs) and palladium nano-photocatalyst, designated as Pd/CDs/Ti3+-TiO2, via a facile hydrothermal-calcination approach. XPS and ESR analyses were performed to verify that the composite contained Ti3+, while TEM imaging and FTIR confirmed that the samples contained CDs. The as synthesized photocatalysts, particularly the 1% Pd/CDs/Ti3+-TiO2 sample, exhibited superior photocatalyzed antibacterial activity to pure TiO2 against E. coli (～6.5 orders of magnitude increase at 30 min). The 1% Pd/CDs/Ti3+-TiO2 photocatalyst also exhibited efficient photodisinfection of five pathogenic agricultural fungi. The dark cytotoxicity of the 1% Pd/CDs/Ti3+-TiO2 nanocomposites was evaluated on HepG2 and Chinese hamster lung (V79) cells via Cell Counting Kit-8 (CCK-8) and found to be minimal. Lastly, the recycling capacity for the photodisinfective activity of the nanocomposites was evaluated and found to be unchanged after five cycles. Four active species were identified as contributing to the photoinduced antimicrobial activity of the catalyst: h+, •O2−, •OH, and e−. Together, our results indicate that Pd/CDs/Ti3+-TiO2 nanocomposites have great potential in agricultural plant pathogen disinfection.