the metal particle also influences the shift in the Fermi level of the composite. For
example, the Fermi level shift observed with 5 nm Au nanoparticles was À40 mV
as compared to À22 mV for 8 nm Au nanoparticles in the AuaTiO 2 nanocomposite
system. The shift of Fermi level to more negative potentials is indicative of increased charge storage and improved charge separation in semiconductor–metal
composite systems. These results, in turn, elucidate the indirect role of noble
metals towards improving the charge separation as well as promoting interfacial
charge transfer kinetics in semiconductor assisted photocatalysis.
Photoelectrochemical studies [185, 186], carried out by depositing gold nanoparticles on nanostructured TiO 2 films exhibit enhanced photocurrent generation.
Improved interfacial charge transfer at the semiconductor/electrolyte interface
resulted in nearly 5 times enhancement of photocurrent generation and a shift in
the apparent flat band potential. Although the TiO 2 aAu interface may offer many
complex scenarios, the photoelectrochemical and photocatalytic measurements
support the argument that the metal nanoparticle deposition facilitates charge
(electron) stabilization in nanostructured semiconductor films and promotes interfacial redox processes.
19.7
Concluding Remarks
The photochemical properties of various nanoassemblies discussed in this chapter
highlight the ways in which the metal and semiconductor nanoparticles interact
with light. Furthermore, one can fine tune these responses by subjecting nanostructures to an externally applied electrochemical bias. The ability to functionalize
these nanoparticles with photoactive molecules has opened new avenues to utilize
these nanoassemblies in light energy conversion and catalytic applications. By
suitably modulating the fluorescence of the surface bound fluorophore these
Equilibration of
Redox couple
e
TiO 2
VB
CB
EF
h
hν
C 60 /C 60 -
(a)
Equilibration of
Redox couple
e
Metal
TiO 2
VB
CB
EF
E F (metal)
h
e
e
e
e
hν
C 60 /C 60 -
22 mV
EF’
(b)
Fig. 19.14. Charge distribution between TiO 2 and gold
nanoparticles leading to equilibration with a C 60 /C 60
À redox
couple: (a) In the absence and (b) in the presence of metal
nanoparticles. E F and E F
0 refer to the Fermi level of TiO 2 before
and after attaining the equilibration.
19.7 Concluding Remarks 635
example, the Fermi level shift observed with 5 nm Au nanoparticles was À40 mV
as compared to À22 mV for 8 nm Au nanoparticles in the AuaTiO 2 nanocomposite
system. The shift of Fermi level to more negative potentials is indicative of increased charge storage and improved charge separation in semiconductor–metal
composite systems. These results, in turn, elucidate the indirect role of noble
metals towards improving the charge separation as well as promoting interfacial
charge transfer kinetics in semiconductor assisted photocatalysis.
Photoelectrochemical studies [185, 186], carried out by depositing gold nanoparticles on nanostructured TiO 2 films exhibit enhanced photocurrent generation.
Improved interfacial charge transfer at the semiconductor/electrolyte interface
resulted in nearly 5 times enhancement of photocurrent generation and a shift in
the apparent flat band potential. Although the TiO 2 aAu interface may offer many
complex scenarios, the photoelectrochemical and photocatalytic measurements
support the argument that the metal nanoparticle deposition facilitates charge
(electron) stabilization in nanostructured semiconductor films and promotes interfacial redox processes.
19.7
Concluding Remarks
The photochemical properties of various nanoassemblies discussed in this chapter
highlight the ways in which the metal and semiconductor nanoparticles interact
with light. Furthermore, one can fine tune these responses by subjecting nanostructures to an externally applied electrochemical bias. The ability to functionalize
these nanoparticles with photoactive molecules has opened new avenues to utilize
these nanoassemblies in light energy conversion and catalytic applications. By
suitably modulating the fluorescence of the surface bound fluorophore these
Equilibration of
Redox couple
e
TiO 2
VB
CB
EF
h
hν
C 60 /C 60 -
(a)
Equilibration of
Redox couple
e
Metal
TiO 2
VB
CB
EF
E F (metal)
h
e
e
e
e
hν
C 60 /C 60 -
22 mV
EF’
(b)
Fig. 19.14. Charge distribution between TiO 2 and gold
nanoparticles leading to equilibration with a C 60 /C 60
À redox
couple: (a) In the absence and (b) in the presence of metal
nanoparticles. E F and E F
0 refer to the Fermi level of TiO 2 before
and after attaining the equilibration.
19.7 Concluding Remarks 635