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Fig. 3 Promotion effects of Au particles on the photocatalytic activity of TiO2
under UV-visible light irradiation.
photo-excited electrons from the conduction band of TiO2. Under
UV-visible light irradiation, triple synergetic promotion effect on the
separation of photo-generated electron–hole pairs over TiO2 by gold
deposition with both large and small particles can be achieved.
In summary, we report the synergetic promotion of the
photocatalytic activity of TiO2 by gold deposition under UV-visible
light irradiation. Theoretically, the synergetic promotion of photo-
catalysts with different intrinsic light absorbance by localized SPR
is possible, which should lead towards the design of highly
efficient photocatalysts under sunlight irradiation.
Fig. 2 Fluorescence intensity caused by trapped OH radicals at time-on-stream
of 30 min with/without Fe3+ under irradiation with different wavelengths.
This work is supported by the Synergetic Innovation Center
of Chemical Science and Engineering (Tianjin), the Ministry of
Education of China (NCET-11-0251) and 111 Project (B12015).
reductive pathway. While significant fluorescence signals corre-
sponding to trapped OH radicals are observed on Au colloid in the
presence of ferric ions (Fig. S12, ESI†). The ferric ions present can
react with photo-generated electrons on Au colloid and the remain-
ing photo-generated holes can subsequently oxidize the hydroxyls
into radicals. Here the ferric ions act as sacrificial agents to promote
the separation of photo-generated electron–hole pairs on Au colloid.
Comparing the formation of OH radicals on Au and Au/TiO2 under
visible light irradiation in the absence of ferric ions (Fig. 2), we come
to the conclusion that the TiO2 support greatly promotes the
separation of photo-generated electron–hole pairs from SPR of Au.
That is, the photo-generated electrons excited by SPR of large Au
particles can transfer to the conduction band of the neighbouring
TiO2,3 which might further transfer to small Au particles driven by
the Fermi level equilibration.13 TiO2 is a favourable support for Au
particles due to its high electron injection ability. Under UV-visible
light irradiation, more OH radicals are formed through the oxidative
pathway than those under UV or visible light irradiation (Fig. 2).
According to the fluorescence intensity corresponding to the for-
mation of OH radicals from the reductive and oxidative pathways,
the synergetic promotion effect on the separation of photo-generated
electron–hole pairs over the Au/TiO2 photocatalyst under UV-visible
light irradiation is clearly confirmed, which is responsible for its
enhanced photocatalytic activity.
Notes and references
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126, 4943.
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun., 2013, 49, 11767--11769 11769