Mesoporous silica nanosheets with well-dispersed small Ag nanoparticles for the construction of robust transparent antibacterial nanocoatings

The fabrication of robust transparent antibacterial nanocoatings on the surface of device and equipment has significant implication for protecting human from bacterial infections in daily life. However, it still faces some challenges such as low antibacterial efficiency and poor mechanical stability, which hinder their wide applications. Therefore, it is urgent to explore the design and fabrication of superior antibacterial nanocoatings with high-robustness. In this work, robust transparent antibacterial nanocoatings were successfully fabricated by employing two-dimensional mesoporous nanosheets as a novel building block. Aminopropyl-modified mesoporous silica nanosheets (MSNSs-NH2) with uniform pore sizes of ca. 5-8 nm were first fabricated by one-pot liquid-liquid interface growth method, and were employed as a carrier to achieve well-dispersed loading of many small Ag nanoparticles (NPs) of ca. 2-4 nm to form MSNSs-NH2@Ag as antibacterial agent. Next, robust transparent antibacterial nanocoatings were prepared by simple dip-coating method without any postprocessing. It is worth noting that the use of two-dimensional MSNSs-NH2 with large spreading area not only facilitates the uniform loading of small Ag NPs for high antibacterial capacity of nanocoatings, but also is beneficial to enhance the mechanical robustness of nanocoatings due to the firm spreadability of single layer mesoporous nanosheets on the flat substrates. The optimal coated glass slide exhibits the enhanced transmittance (94.2% at 535 nm), high-mechanical robustness (pencil hardness test: >3H, tape adhesion test: >4B) and excellent antibacterial activity (at least killing 80% bacteria) toward Gram-negative Escherichia coli. This work may provide an exploration strategy to construct multifunctional nanocoatings by using the novel mesoporous nanosheets as a building block