Effective disinfection of airborne microbial contamination in hospital wards using a zero‐valent nano‐silver/TiO2‐chitosan composite

A novel antimicrobial composite of zero‐valent silver nanoparticles (AgNPs), titania (TiO2), and chitosan (CS) was prepared via photochemical deposition of AgNPs on a CS‐TiO2 matrix (AgNPs@CS‐TiO2). Electron microscopy showed that the AgNPs were well dispersed on the CS‐TiO2, with diameters of 6.69‐8.84 nm. X‐ray photoelectron spectra indicated that most of the AgNPs were reduced to metallic Ag. Fourier‐transform infrared spectroscopy indicated that some AgNPs formed a chelate with CS through coordination of Ag+ with the CS amide II groups. The zones of inhibition of AgNPs@CS‐TiO2 for bacteria (Escherichia coli and Staphylococcus epidermidis) and fungi (Aspergillus niger and Penicillium spinulosum) were 6.72‐11.08 and 5.45‐5.77 mm, respectively, and the minimum (critical) concentrations of AgNPs required to inhibit the growth of bacteria and fungi were 7.57 and 16.51 µg‐Ag/mm2, respectively. The removal efficiency of a AgNPs@TiO2‐CS bed filter for bioaerosols (η) increased with the packing depth, and the optimal filter quality (qF) occurred for packing depths of 2‐4 cm (qF = 0.0285‐0.103 Pa−1; η = 57.6%‐98.2%). When AgNPs@TiO2‐CS bed filters were installed in the ventilation systems of hospital wards, up to 88% of bacteria and 97% of fungi were removed within 30 minutes. Consequently, AgNPs@TiO2‐CS has promising potentials in bioaerosol purification.