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NUCLEAR TECHNOLOGIES AND METHODS 123
References
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(1992).
TITANIUM DIOXIDE AND OTHER MATERIALS
COATED WITH SILICA-QATS COMPOUNDS AND METALLIC SILVER
AS POTENTIAL BIOCIDES AND PHOTOCATALYTIC BIOCIDES
Andrzej Łukasiewicz, Dagmara K. Chmielewska, Jacek Michalik
The photochemical and photocatalytic properties
of TiO 2
have been the subject of intensive investigations
in recent years [1-3]. One of the methods
applied in order to enhance the efficiency of photocatalytic
properties is coating or dopping the material
with noble and transition metals [4,5].
Silica materials elaborated by coating of TiO 2
or other carriers (e.g. dolomite) with salt of water
glass (WG) and quaternary N-alkylammonium
a) b)
c)
Fig. SEM photomicrograph of: TiO 2 -WG·QAC material (a), TiO 2 -WG·QAC material with silver coating after UV irradiation
(b), TiO 2 -WG·QAC material with silver coating after UV irradiation and HNO 3 treatment (c).
compound (QAC) were described previously [6].
In course of this research it was found out that
TiO 2 -WG·QAC materials bind Ag + from aqueous
solutions and after UV irradiation reduction of
silver takes place. Photochemical reduction of Ag +
in these materials is much faster than for pure TiO 2 ,
what suggests strong photochemical properties of
TiO 2 -WG·QAC. Silver is also an antibacterial agent
with an exceptionally broad spectrum of bacteria,
so due to additional binding of silver in the material
a synergic effect occurs and a higher antibacterial
activity of the materials can be obtained.
Preliminary electron paramagnetic resonance
(EPR) spectroscopy and scanning electron microscopy
(SEM) investigation of the materials were
carried out. SEM investigations suggest that metallic
silver creates 30-50 nm particles on the biocidal
materials grains. Three SEM images for non-modified
TiO 2
-WG·QAC material, the material with
silver coating and UV irradiation and the same material
after HNO 3 treatment that caused silver coating
dissolution, are presented in Fig.
The combined system TiO 2 photocatalyst–WG-
-QAC photocatalyst demonstrates particularly interesting
effects. TiO 2
-WG·QAC in comparison to
pure TiO 2 significantly accelerates the reduction
of Cr 6+ to Cr 3+ , it suggests photochemical syner-