The properties of Cu-doped TiO2
nanoparticles (NPs) were independently controlled in a flame aerosol reactor
by varying the molar feed ratios of the precursors, and by optimizing
temperature and time history in the flame. The effect of the physico-chemical
properties (dopant concentration, crystal phase and particle size) of Cu-doped
TiO2
nanoparticles on inactivation of Mycobacterium smegmatis (a model pathogenic bacterium)
was investigated under three light conditions (complete dark, fluorescent light and UV
light). The survival rate of M. smegmatis (in a minimal salt medium for 2 h) exposed to the
NPs varied depending on the light irradiation conditions as well as the dopant
concentrations.
In dark conditions, pristine TiO2
showed insignificant microbial inactivation, but inactivation increased with increasing dopant
concentration. Under fluorescent light illumination, no significant effect was observed for
TiO2. However,
when TiO2
was doped with copper, inactivation increased with dopant concentration, reaching more than 90%
(>3 wt% dopant). Enhanced microbial inactivation by
TiO2
NPs was observed only under UV light. When
TiO2
NPs were doped with copper, their inactivation potential was promoted and the
UV-resistant cells were reduced by over 99%. In addition, the microbial inactivation
potential of NPs was also crystal-phase-and size-dependent under all three
light conditions. A lower ratio of anatase phase and smaller sizes of Cu-doped
TiO2
NPs resulted in decreased bacterial survival. The increased inactivation potential of doped
TiO2
NPs is possibly due to both enhanced photocatalytic reactions and leached copper ions.