Near infrared light activatable PEI-wrapped bismuth selenide nanocomposites for photothermal/photodynamic therapy induced bacterial inactivation and dye degradation.

The inactivation of bacteria and the degradation of organic pollutants by engineered nanomaterials (NMs) are very effective approaches for producing safe and clean drinking water. The development of new NMs which can act as NIR light mediated antimicrobial agents as well as photocatalytic agents is highly desired. In this study, a novel BiSe nanoplates (NPs) NM was prepared by a high-temperature reaction (colloidal synthesis) followed by wrapping of the surface with polyethyleneimine (PEI) through electrostatic interactions. The developed BiSe NPs/PEI exhibited excellent NIR light activated antimicrobial properties for bacterial eradication and efficient photocatalytic properties for organic dye degradation. The results showed that upon 808 nm laser irradiation the engineered BiSe NPs/PEI eradicated ∼99% of and ∼97% of bacteria within 10 minutes of irradiation through combined dual-modal photothermal therapy (PTT) and photodynamic therapy (PDT) the generation of heat and reactive oxygen species, respectively. The contributions of PTT and PDT were found to be in a ratio of nearly 4 : 1 in the killing of both species of bacteria. In addition, BiSe NPs/PEI also acted as an excellent photocatalyst under illumination by a halogen lamp equipped with a 700-1100 nm band pass filter to achieve degradation efficiencies of ∼95% for methylene blue and ∼93% for Rhodamine B within 3 and 4 h, respectively. To the best of our knowledge, this is the first demonstration of these NIR light activated antimicrobial properties, photodynamic properties and photocatalytic properties mediated by BiSe NPs.