the concentration of graphene oxide in starting solution played an important role in
photoelectronic and photocatalytic activity of composites. Li et al. [51] reported a
sol–gel method to synthesis the ultradispersed TiO 2 nanoparticles which were grown
on graphene sheets. The preparation process was schematically illustrated in
Fig. 5.3. The amorphous TiO 2 nanoparticles were deposited on GO sheets via the
hydrolysis and condensation of TBOT in pure ethanol with a low content of
concentrated ammonia, which would lead to the selective formation of amorphous
TiO 2 /GO sheets. After a thermal treatment process, amorphous TiO 2 nanoparticles
are crystallized into uniform anatase nanoparticles accompanied by the reduction of
GO sheets, leading to the formation of TiO 2 nanocrystals/RGO sheets.
In addition to the methods mentioned above, there are also some other methods
which could be used in the preparation of 2D TiO 2 /graphene composites, such as UV
light irradiation, microwave-assisted method, chemical vapor deposition [52], and
vacuum activation methods [53]. Mohamed et al. [54] prepared the TiO 2 -reduced
RGO composite by UV-assisted photocatalytic reduction of graphite oxide mixed
with TiO 2 nanoparticles in the ethanol. The mixture was illuminated under a 250 W
high-voltage Hg lamp with the main wave crest at 254 nm for 24 h under ambient
conditions and magnetic stirring. After UV irradiation, it was obvious that the color
of suspension changed into grayish black, which indicated the successful reduction
of graphene oxide sheets. Pu et al. [55] synthesized the GO–TiO 2 hybrids (GTHs) by
a one-pot microwave-assisted combustion method. The precursor solution was
heated on a hot plate at 100
C to remove the solvent until a gel-like precursor
Mesoporous silica
(TiO 2 /MCM-41)
Graphene partially
covered on TiO 2
acetone, RT
OH
OH
OH
OH
OH
OH
Hydroxyl groups
mechanical mixing
with graphene
TiO 2
nanosheets
a
b
Surface
complexes
N 2 , 1073 K
(DN-TiO 2 /MCM-41)
Ti
Ti
OH
OH
O
O
O
O
O
O
O
O
Ti Ti
Ti
(G n -TiO 2 /MCM-41)
Ti
Ti
TiO 2
TiO 2 surface
Fig. 5.2 (a) Illustration of the formation of TiO 2 nanosheet mechanical mixing with graphene.
Reprinted with permission from Ref. [49]. Copyright 2016, John Wiley and Sons. (b) Schematic
diagram of the procedures for the preparation of Gn–TiO 2 /MCM-41. (Reprinted with permission
from Ref. [50]. Copyright 2010, American Chemical Society)
5.2 TiO 2 /Graphene Composite
111
photoelectronic and photocatalytic activity of composites. Li et al. [51] reported a
sol–gel method to synthesis the ultradispersed TiO 2 nanoparticles which were grown
on graphene sheets. The preparation process was schematically illustrated in
Fig. 5.3. The amorphous TiO 2 nanoparticles were deposited on GO sheets via the
hydrolysis and condensation of TBOT in pure ethanol with a low content of
concentrated ammonia, which would lead to the selective formation of amorphous
TiO 2 /GO sheets. After a thermal treatment process, amorphous TiO 2 nanoparticles
are crystallized into uniform anatase nanoparticles accompanied by the reduction of
GO sheets, leading to the formation of TiO 2 nanocrystals/RGO sheets.
In addition to the methods mentioned above, there are also some other methods
which could be used in the preparation of 2D TiO 2 /graphene composites, such as UV
light irradiation, microwave-assisted method, chemical vapor deposition [52], and
vacuum activation methods [53]. Mohamed et al. [54] prepared the TiO 2 -reduced
RGO composite by UV-assisted photocatalytic reduction of graphite oxide mixed
with TiO 2 nanoparticles in the ethanol. The mixture was illuminated under a 250 W
high-voltage Hg lamp with the main wave crest at 254 nm for 24 h under ambient
conditions and magnetic stirring. After UV irradiation, it was obvious that the color
of suspension changed into grayish black, which indicated the successful reduction
of graphene oxide sheets. Pu et al. [55] synthesized the GO–TiO 2 hybrids (GTHs) by
a one-pot microwave-assisted combustion method. The precursor solution was
heated on a hot plate at 100
C to remove the solvent until a gel-like precursor
Mesoporous silica
(TiO 2 /MCM-41)
Graphene partially
covered on TiO 2
acetone, RT
OH
OH
OH
OH
OH
OH
Hydroxyl groups
mechanical mixing
with graphene
TiO 2
nanosheets
a
b
Surface
complexes
N 2 , 1073 K
(DN-TiO 2 /MCM-41)
Ti
Ti
OH
OH
O
O
O
O
O
O
O
O
Ti Ti
Ti
(G n -TiO 2 /MCM-41)
Ti
Ti
TiO 2
TiO 2 surface
Fig. 5.2 (a) Illustration of the formation of TiO 2 nanosheet mechanical mixing with graphene.
Reprinted with permission from Ref. [49]. Copyright 2016, John Wiley and Sons. (b) Schematic
diagram of the procedures for the preparation of Gn–TiO 2 /MCM-41. (Reprinted with permission
from Ref. [50]. Copyright 2010, American Chemical Society)
5.2 TiO 2 /Graphene Composite
111