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jected to three cycles of centrifugation (8000 rpm, 10 min) and
washed (40ꢂ3 mL ultrapure water) to obtain Te-titanate nano-
tubes. To prepare Te-TiO2 NRs, the Te-titanate nanotubes were dis-
persed in deionized water (40 mL) and then transferred to a stain-
less-steel autoclave (50 mL) lined with Teflon. The sealed autoclave
was heated in an oven at 2008C for 24 hours, and then cooled in
air.
under irradiation with visible light or in the dark. The concen-
2À
2À
trations of TeO3 and SeO3 ions in the media decreased
gradually over 0–60 minutes. The decreasing order of the re-
2À
leased SeO3 ions from the Sen/Te-TiO2 NRs was Se0.07/Te-TiO2 >
Se0.05/Te-TiO2 >Se0.02/Te-TiO2. This order is consistent with the
result of the antibacterial activity in the dark. Thus, the antibac-
terial activities of Sen/Te-TiO2 NRs were also analogous to the
2À
2À
released TeO3 and SeO3 ions, which are toxic to most mi-
croorganisms mainly because of their strong oxidative
Synthesis of anatase Sen/Te-TiO2 NRs
nature.[45] The results reveal that the formation of TeO3 and
2À
The selenite (SeO32À) solution (100 mm) was prepared by dissolving
2À
SeO3 ions is mainly responsible for the antibacterial activity
SeO2 powder (0.44 g) in ultrapure water (40 mL). The as-prepared
2À
of the Sen/Te-TiO2 NRs in the dark. Because the concentrations
Te-TiO2 NMs were dispersed in water (40 mL). Aliquots of SeO3
2À
2À
of the released TeO3 and SeO3 ions were almost the same
with/without irradiation with visible light, greater antibacterial
activity of the tested NRs under irradiation conditions is due to
their catalytic production of ROS.
solution were added to the as-prepared Te-TiO2 solutions (each
2À
40 mL), with final SeO3 concentrations of 2, 5, and 10 mm. After
30 minutes, the mixtures were subjected to three cycles of centri-
fugation (8000 rpm, 10 min) and washed (40ꢂ3 mL ultrapure
water) to obtain selenite ions adsorbed Te-TiO2 NRs. The pellets
were separately dispersed in ultrapure water (40 mL). Then aliquots
(10 mm, 5 mL) of NaBH4 solution were separately added into the
solutions under magnetic stirring. After 10 minutes, the mixtures
were subjected to three cycles of centrifugation (8000 rpm,
10 min) and washed (40ꢂ3 mL ultrapure water) to obtain brown
Sen/Te-TiO2 NRs.
Conclusion
Te-TiO2 NRs and Sen/Te-TiO2 NRs with exposed {100} facets were
prepared and tested as efficient photocatalysts and antibacteri-
al agents against E. coli and S. aureus. By doping Se and Te
onto the TiO2 NRs, the photocatalytic activity towards the pro-
duction of ·OH increased as a result of an increase in the UV/
Vis absorption. In addition to the generation of ROS, the re-
Photocatalytic activity measurement
2À
2À
The photocatalytic activities of the as-prepared Te-TiO2 NRs, Sen/Te-
TiO2 NRs, and commercial TiO2 NPs were evaluated by determining
the production of ·OH in aqueous solutions at ambient tempera-
ture. The NMs (5 mg) were separately suspended in NaOH solution
(10 mm, 10 mL) containing terephthalic acid (3.0 mm). The mixtures
were stirred in the dark for 30 minutes, allowing the mixtures to
reach equilibrium before irradiation with visible light using a 450-
W xenon arc lamp equipped with a 420 nm cutoff filter. The light
source was positioned 30 cm above the mixtures. During the pho-
toreactions, no oxygen was bubbled into the suspensions. Aliquots
(1.0 mL) of the solutions were taken out every 20 minutes. After
being subjected to centrifugation (8000 rpm, 10 min), the fluores-
cence spectra (excitation wavelength 320 nm) of the supernatants
were recorded.
leased TeO3 and SeO3 ions were responsible for enhancing
the antibacterial activity of the Sen/Te-TiO2 NRs. Relative to
commercial TiO2 NPs, the Te-TiO2 NRs and Se0.07/Te-TiO2 NRs
provide 2.5- and 4.5-fold higher photocatalytic activities. The
low cost and high efficiency Se0.07/Te-TiO2 NRs are quite stable
and biocompatible, thus showing great practical potential as
new and efficient antibacterial agents.
Experimental Section
Preparation of Na-titanate nanotubes
P25 powder (1 g) was added to an aqueous solution of NaOH
(10m, 40 mL), and then transferred to a stainless-steel autoclave
(50 mL) lined with Teflon. The sealed autoclave was heated in an
oven at 2008C for 24 hours, and then cooled in air. The obtained
solution of Na-titanate nanotubes was subjected to three cycles of
centrifugation and washing; centrifugation was conducted at
8000 rpm (Hettich Universal 32R, Tuttlingen, Germany) for 10 mi-
nutes and ultrapure water (40ꢂ3 mL) was used to wash the pel-
lets.
Antibacterial test
E. coli DH5a and S. aureus were grown in sterile LB media. The
media were prepared by dissolving bacto-tryptone (2.5 g), bacto-
yeast extract (1.25 g), and NaCl (2.5 g) in H2O (250 mL), which was
then adjusted to pH 7.0 by adding NaOH (5.0m). A single colony of
each strain was lifted from an LB agar plate and inoculated in LB
media (10 mL). The cultures were then grown overnight until the
absorbance at the wavelength 600 nm (A600) reached 1.0. A portion
of each of the cell mixtures (1 mL) was centrifuged (4000 rpm,
10 min) and washed three times with 0.85% sodium chloride (3ꢂ
1 mL) to remove the matrix. Cells diluted to 4.0ꢂ108 CFUmLÀ1
were treated in LB media with/without one of the NMs (Te-
TiO2 NRs, Sen/Te-TiO2 NRs, and TiO2 NPs; 100 mgmLÀ1), which were
either irradiated using visible light (60 min) or not. The viability
assay was conducted using SYTO 9 (6 mm) and propidium iodide
(PI; 30 mm) stains. Each of the cell samples was then subjected to
three cycles of centrifugation/washing to remove the matrix; cen-
trifugation at 4000 rpm for 10 minutes; wash with 0.85% sodium
chloride (3ꢂ1 mL). Each of the bacterial suspension (100 mL) was
Synthesis of anatase Te-TiO2 NRs
The tellurite (TeO32À; 10 mm) ions were prepared by dissolving
TeO2 powder (0.064 g) in an aqueous solution of NaOH (20 mm,
40 mL). The as-prepared Na-titanate nanotubes were dispersed
2À
into a solution of TeO3 (40 mL). After 30 minutes, the mixture was
subjected to three cycles of centrifugation (8000 rpm, 10 min) and
washed (40ꢂ3 mL ultrapure water) to obtain tellurite ions ad-
sorbed on Na-titanate nanotubes. The pellet was dispersed in ultra-
pure water (40 mL) and then NaBH4 solution (10 mm, 5 mL) was
2À
added to the solution of TeO3 adsorbed Na-titanate nanotubes
during magnetic stirring. After 10 minutes, the mixture was sub-
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemPlusChem 2013, 78, 302 – 309 308
Lin, Zong-Hong
