Optical absorption of nanoparticles is characterized by broad absorption spectrum with no clear edge for the main absorption band (I. e. Band gap).
What are the main reasons?
There are no such thing, nano silver could show broad band started from ~300 nm but it could show relatively narrow peak at ~420, and CdSe proved the same phenomenon, depending on size and shape absorption beaks do red or blue shift.
However, peaks boarding could be attributed to high difference in particle size distribution.
"The optical absorption spectra of semiconductors give information about optical properties and composition of materials. Three main regions can be distinguished: (1) region of weak absorption, which is arise from defects and impurities, (2) absorption edge region associated with disorder of the system and affecting a real value of the energy gap and (3) the region that determine the optical band-gap energy which value is associated with crystallite size"
You can read about it in my work, in which I determined optical band gap for magnetite nanoparticles modified by organic compunds:
Article Structure and optical properties of Fe 3 O 4 nanoparticles s...
Dear sir the energy gap of nano partical depended on size and method of preparation becuase to determine the energy gap youmust have edx it is important for you
It depends on the size and shape as much as they are identical to each other and small the absorbance will increase.
Hi Ahmed,
It is due to large size distribution, different particles morphologies, and impurities attached to particles surfaces.
This is also happened in my work.
Regards.
since optical properties and other parameter in nanoscale materials depends on size, than the energy gap is a direct dependent on nanosize. It increases with the decrease of particles size. Mostly it will be difficult to obtain a single size particles in a medium for optical examining to obtain single wave absorption instead mult range wavelength absorptiino will occurres
for more information I suggest to read the following power point presentation
"Solid Surface and Nanoscale materials Structure"
M. S. Omar
Presentation · July 2016 with 156 Reads
DOI: 10.13140/RG.2.2.31947.59684
Charmo, University of Charmo, University of Salahaddin, DOI:10.13140/RG.2.2.31947.59684
If you got the homogeneous distribution then only to got the sharp peak.. Otherwise only got broader one.
Simply photon absorption is depend on the size of the nanoparticle.
Best regards
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