I have successfully synthesized my nanocomposites with different concentrations. For optical properties i have done Diffuse Reflectance Spectroscopy(UV-Visible). I observe reduction in the Reflectance as well as the band gap of the material as I increase the concentration of second material. So tell me the possible reasons why the band gap and reflectance changed?
Dear Muhammad Waqar
After adding impurities band gap of the host material remains the same only when impurity concentration is very small, i.e, at ppm level. If impurity concentration is high, a new alloy or compound may be formed which will have entirely different optical properties and different band gap. The same may be happening in your case. In case of nano materials, band gap also depends on particle size. If particle size is also changing with impurity concentration then also band gap may change. Measure particle size if you are in 10 nm range.
Dear Waquar
As Dr kumar has stated that optical properties of materials are highly size dependent in case of nano materials. You should go for TEM analysis of your samples to confirm the particle size.
Dear Waquar,
It is quite straight forward that by introducing the second material whose band positions might lie in between the parent material, there there is a possibility of reduction DRS and band gap.
when you are adding some impurity into any material then it has its own energy states which you can call virtual states below or above the conduction band of host material
if the doping material has virtual states below the conduction band of host material then reduction in bandgap occurs
and vice versa.
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