Photocatalysis/catalysis by innovative TiN and TiN-Ag surfaces inactivate bacteria under visible light

Abstract

a b s t r a c tThis study presents the design, preparation, testing and characterization of TiN and TiN-Ag nanoparticulate films leading to photocatalytic and catalytic inactivation of Escherichia coli. When Ti was sputtered in N 2 atmosphere, the TiN films unexpectedly revealed semiconductor properties when irradiated under visible light due to the formation of TiO 2 showing absorption in the visible spectral region. In TiN-Ag films, Ag enhances the photocatalytic activity of TiN leading to faster bacterial inactivation. Evidence for the presence of TiO 2 and TiN in the films is presented by XPS. The TiN layers 50 nm thick sputtered by DC for 3 min led to complete inactivation of E. coli within 120 min. But TiN layers with a thickness >50 nm hinder the surface diffusion of charges reducing bacterial inactivation. The rate of TiN deposition was ∼1.4 × 10 15 atoms TiN/cm 2 s. For the TiN-polyester samples under visible light a 3 log 10 bacterial reduction (99.9%) was observed within 30 min while for TiN-Ag samples the same bacterial reduction was attained within ∼15 min. The absorption of the TiN-Ag samples in Kubelka-Munk (KM) units was directly proportional to the E. coli inactivation kinetics. TiN-Ag plasmon nanostructures are concurrently formed under low intensity visible light and accelerated bacterial inactivation. This study shows that TiN films have the potential to replace Ag-based disinfection materials leaching Ag into the environment.

Coupling of narrow and wide band-gap semiconductors on uniform films active in bacterial disinfection under low intensity visible light: Implications of the interfacial charge transfer (IFCT)

“…Direct current (DC) magnetron sputtering of metals and semiconductor oxides on diverse substrates has been recently reported by our laboratory [13,14]. Fig.…”

“…2a, trace 1). This is due probably to: (a) bigger Ag-clusters hindering the diffusion of charges between TaN and the Ag layers, (b) a decrease in the number of surface catalytic sites available for bacterial inactivation [13,14], and (c) an excess of Ag acting as recombination centers for the photo-induced charges on the sample surface. Fig.…”

“…Our laboratory has recently reported oxy-nitrides films [13] and nitrides [14] films inactivating bacteria under visible light irradiation. Ag has been reported not to be miscible with TaN in nanocomposite films [15,16].…”

Evidence for TiON sputtered surfaces showing accelerated antibacterial activity under simulated solar irradiation

“…The 100 lL sample of each dilution was pipetted onto a nutrient agar plate and then spread over the surface of the plate using the standard plate method. Agar plates were incubated lid down, at 37°C for 24 h prior to the counting of the bacterial colonies (Rtimi et al, 2012a(Rtimi et al, , 2012bBaghriche et al, 2012b). The bacterial data reported were replicated three times.…”

“…Kelly et al (2009 and) has recently reported the antibacterial activity of sputtered nitrides films. Rtimi et al have reported TiN/ TiN-Ag and ZrN/ZrN-Ag film bacterial inactivation in the dark and under visible/actinic low intensity light irradiation (Rtimi et al, 2012a(Rtimi et al, , 2012bBaghriche et al, 2012b). The innovative objective of the present study is to report on solar induced bacterial inactivation by sputtered TiON films using laboratory scale solar simulators.…”