Light reflection is a problem for lenses and displays and causes, e.g, poor readability and contrast. In addition, surfaces such as phone or tablet touchscreens can host harmful bacteria. A dual-function thin film coating with both antireflective and antibacterial properties would, thus, be very useful for applications in touchscreens, glass surfaces in areas with special hygiene requirements, optical devices in medicine, etc.

Junhui He, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, and Kaikai Wang, Technical Institute of Physics and Chemistry and University of Chinese Academy of Sciences, Beijing, have developed such a dual-purpose thin film based on mesoporous silica with embedded silver nanoparticles (NPs). The team prepared silica sols containing Ag NPs by dissolving poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) in ethanol and then adding silver nitrate and tetraethyl orthosilicate (TEOS). Glass slides were coated by dipping them in the silica sol, followed by calcination at 550–720 °C.

The optical and antibacterial properties of the resulting thin films were tested using transmittance and reflectance spectroscopy and E. coli cultures, respectively. The films show high transmittance of visible light and have excellent antibacterial activity due to the Ag NPs. They also are mechanically robust and can withstand cleaning. According to the researchers, these properties make the films promising for application.

• One-Pot Fabrication of Antireflective/Antibacterial Dual-Function Ag NP-Containing Mesoporous Silica Thin Films,
  Kaikai Wang, Junhui He,
  ACS Appl. Mater. Interfaces 2018.
  https://doi.org/10.1021/acsami.8b00192