3.1.3. Raman analysis
Fig. 3 shows the Raman spectra of (i) TiO2 and (ii) Ag–TiO2
particles. For pure TiO2 sample, the appearance of sharp and
intense peak at 144 cm1 and a very weak peak at around
196 cm1 assigning to Eg mode of vibration was the characteristic
of anatase TiO2 [24]. In the higher frequency region,
the other peaks at around 400, 516 and 639 cm1 corresponding
to B1g, A1g and Eg modes also confirmed the presence of
anatase TiO2 [25]. In the presence of Ag in TiO2, the intensity
of the corresponding Raman peaks due to anatase TiO2 was
significantly decreased. However, two broad peaks at around
1348 and 1568 cm1 were due to COO stretching mode [26]
of adsorbed biomolecules containing ascorbic acid present in
Ag nanoparticles. It is worth mentioning that Ag nanoparticles
were obtained from green carambola fruit extract. Thus, the
cause of decrease in intensity of anatase TiO2 in the presence
of Ag was due to the presence of adsorbed biomolecules.
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