Paper Substrate of Ti <sub>3</sub>C <sub>2</sub>T <sub>x</sub>-Au NPS for SERS Detection of Bacteria and Multi-Therapeutic Antibacterial

Bacterial infections have become a serious global health problem due to the misuse of antibiotics which cause the emergence of antibiotic-resistant strains. Photothermal therapy (PTT) has been widely studied in recent years as a method to combat the development of bacterial resistance. However, PTT may cause damage to the human body due to excessive laser power. Therefore, it is important and urgent to develop a multifunctional platform that can sensitively detect bacteria and effectively inhibit or kill bacteria at low laser power. Herein, a novel multifunctional paper substrate of Ti3C2Tx-Au NPs was successfully synthesized by self-assembly and freeze-dring method for bacterial detection and photothermal sterilization at low laser power. The typical gram-negative Escherichia coli (E. coli) and the gram-positive Methicillin-resistant Staphylococcus aureus (MRSA) were used as models to perform label-free, rapid and sensitive detection of bacteria based on the surface-enhanced Raman spectroscopy (SERS) method. Paper substrate of Ti3C2Tx-Au NPs exhibits significant antibacterial effects when irradiated with 808 nm light at a low laser power of only 300 mW/cm2 and a short irradiation time of 5 minutes, and the germicidal rates for E. coli and MRSA were 99.94% and 92.71%, respectively. At the same time, paper substrate of Ti3C2Tx-Au NPs also produces a variety of reactive oxygen species under 808 nm laser irradiation, resulting in photodynamic therapy (PDT). Accordingly, this paper substrate of Ti3C2Tx-Au NPs not only can sensitively detect bacteria, but also has photothermal and photodynamic sterilization, providing a promising countermeasure for the clinical treatment of diseases caused by multidrug-resistant bacteria.