Novel yellow light-responsive SnO₂/SnS₂ piezo-photocatalysts with excellent performances for tooth whitening and biofilm eradication

Oral problems caused by pathogens and tooth discoloration have posed great threats to public health in recent years. Timely killing of cariogenic bacteria and removing surface pigments are the key points to treat yellow teeth to restore healthy whitening. Piezo-photocatalysis has been proved to be an effective strategy for treating yellow teeth. However, few effective and safe nanomaterials have been developed to address this issue in the oral field. Herein, yellow light-responsive SnO₂/SnS₂ heterostructures are proposed for piezo-photocatalytic biofilm eradication and tooth whitening for the first time. Initially, XRD and HRTEM results experimentally verified the formation of SnO₂/SnS₂ heterostructures. Further, UV-vis DRS spectra indicated that the absorbance in the visible region was effectively improved after the formation of SnO₂/SnS₂ heterostructures. Subsequently, yellow light with excellent biocompatibility was combined with ultrasonic treatment to explore the piezo-photocatalytic performances of SnO₂/SnS₂ for tooth whitening and biofilm removal. Results demonstrated that the SnO₂/SnS₂ heterostructure prepared with a TAA : SnO₂ molar ratio of 1 : 1 for 3 h exhibited the best piezo-photocatalytic performance. The degradation efficiency for the food colorant indigo carmine reached 94.12%, which was much higher than that of single SnS₂ (48.31%), single SnO₂ (near zero) and treating with only irradiation (63.03%) and only ultrasonic (79.41%). Simultaneously, the heterostructures exhibited excellent piezo-photocatalytic tooth whitening effect on stained teeth. Moreover, the SnO₂/SnS₂ heterojunctions exhibited excellent piezo-photocatalytic performances in bacteria killing and biofilm removal, and the antibacterial efficiencies reached 77.3% and 56.5% for planktonic <i>S. mutans</i> and biofilms, respectively. In addition, synergistic treating process of SnO₂/SnS₂ heterostructures resulted in excellent biocompatibility, including much less cytotoxicity and negligible enamel damage. In-depth mechanism investigation indicated that the improved piezo-photocatalytic performances were due to the increased carrier separation efficiency and ROS productivity of SnO₂/SnS₂ heterostructures, demonstrating the great potential of SnO₂/SnS₂ heterostructures for future dental care field.