3.3.5   Morphological studies

3.3.5   Morphological studies

The
morphology of the as-prepared samples was studied using FESEM and TEM. The
FESEM image for AuNPs is shown in Figure 3.6(a), which appears to be spherical
with a uniform size. The elemental analysis of the sample performed by EDS, as
shown in Figure 3.6(b), indicates that the primary component of the sample is
Au. Moreover, presence of carbon (C) and oxygen (O) are also detected. Although
the C peak mostly arises from the copper tape, in this case it particularly
would have come from the sample synthesized through green route (Mendoza-Resendez
et al., 2013). The bright
particles observed in the FESEM image for Au:TiO2 nanocomposite
film, as shown in  Figure 3.6(c),
indicating the distribution of gold nanoparticles in the TiO2nanoparticles
matrix.From this figure it is also observed that no significant change in the
morphology of the TiO2 film was noticed upon the addition of Au. The
EDX results for Au:TiO2 film, shown in Figure 3.6(d), confirms the
presence of Ti, O, C and Au. The Figures 3.6(e and f) show the cross sectional
views of pure TiO2 film and Au:TiO2 nanocomposite film,
which confirm the thickness of both the films are of the order of  7 mm.TEM
and STEM-EDX mapping were also recorded to confirm the morphology of the Au:TiO2
nanocomposite slurry. Figure 3.7 (a) shows that the TEM image of the Au:TiO2
nanocomposite, which are almost in spherical shape and uniformed size. Figure
3.7 (b) shows an STEM mapping of Au:TiO2 nanocomposite in which Au
shows in blue, Ti and O shows red and green color. This results shows that
AuNPS are homogeneously distributed in the matrix of TiO2
nanoparticles. Figure 3.7(b) shows the HRTEM image of the Au:TiO2
nanocomposite slurry. A Fast Fourier Transform (FET) pattern generated from the
region highlighted by the square panel, shown in Figure 3.7(b), was inserted in
it. The inverse FET image obtained from the green marked spot indicated in the
FET pattern, given in Figure 3.7(b), is shown in Figure 3.7(c) and the
corresponding lattice spacing is presented in Figure 3.7(d). The observed
d-value of 0.204 nm clearly identified as the Au (200) plane, completely
distinguished from the TiO2 lattice fringes (Naphade et al., 2014).The same procedure was followed to calculate
the d-spacing values of the adjacent grains of the Au nanopartice, which are
corresponding to the different planes of TiO2, and are shown in Figure
3.7(e). The lattice fringes with d spacing of 0.35 nm and 0.23 nm are
correspond to the (101) and (004) planes of anatase TiO2
respectively, whereas the interplanar spacing of 0.16 nm is assigned to
the (211) plane of rutile TiO2.  Figure 3.7(f) depicts the selected
area electron diffraction (SAED) pattern of the nanocrystalline Au:TiO2
composite. The bright concentric rings pattern observed in this figure clearly
reveals the formation of (105), (200), (004) and (101) planes of anatase TiO2.