Effective disinfection of airborne microbial contamination in hospital wards using a zero-valent nano-silver/TiO_2-chitosan composite

摘要

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 mu g-Ag/mm(2), respectively. The removal efficiency of a AgNPs@TiO2-CS bed filter for bioaerosols (eta) 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; eta = 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.