Photo-disinfection is one of the most promising nanotechnologies for water disinfection without concern of harmful disinfection byproducts. The absorption light spectrum shifts to the visible region over non-metallic/metallic-TiO2 composites with much enhanced interfacial charge transfer efficiency. We will clarify the kinetics and biophysical properties of visible-light selective non-metallic/metallic-TiO2 composites exemplified by two bio-indicators, i.e., E. coli and S. aureus. The ultrahigh resolution microscope (transmission X-ray microscopy, TXM) and the atomic force microscopy (AFM) reveal the single and group cellular structure and biophysical properties of the bacterial cell during photo-disinfection. Results show that the light intensity is a major parameter affecting microbial inactivation as described by the Hom model, where N, N0, t, I, α, k1, k2, and k3 are residual bacteria concentration (CFU/mL), initial bacteria concentration (CFU/mL), irradiation time (min), light intensity (mW/cm2), and order constant, respectively. The photo-disinfection efficiency increases from 41.7% to 99.3% with increase in light intensity from 0.2 to 7.3 mW/cm2, respectively. The lipid peroxidation increases by 19.8% when exposing E. coli to visible light in the presence of photocatalytic composites. The cellular membrane adhesion is 1.7 and 1.5 nN after 6-h inactivation for E. coli and S. aureus, respectively. In-situ 3D cellular structure shows that the S. aureus shrinks, the cell density decreases, and the inner cellular leakage increases after 2-h. The Hom model describes the photo-disinfection well. Photo-disinfection process renders the cellular structure disordered. The biophysical property and the 3D structure image technologies have the potential to monitor any subtle changes on the microorganism, which can be applied to medical diagnosis.

Photo-disinfection processes over visible-light selective non-metallic/metallic -TiO2 composites

2019 Fall National Meeting

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