what is origin of color generation from nanoparticles and nanostructures?
For nanoparticles, it's due to surface plasmon resonance mainly dependant of the dielectric constant of the material of the nanoparticle and its diamater. For instance, see:
http://turroserver.chem.columbia.edu/surfaceplasmons/pdf/20_csr_35_209_plasmonreview.pdf
and
http://photonicswiki.org/index.php?title=Gold_Nanoparticles_%E2%80%93_Surface_Plasmon_Resonance
For nanostructures, it depends of the structure (bumps, grids, 2D, 3D, ...), but for a periodic structures, as photonic crystals ,you have photonic bandgap as electron bandgap for semiconductors but for photons. As instance, take a look at:
http://en.wikipedia.org/wiki/Photonic_crystal
You can see these natural effects of color of photonic crystals on some butterfly wings.
Kind Regards
For nanoparticles, it's due to surface plasmon resonance mainly dependant of the dielectric constant of the material of the nanoparticle and its diamater. For instance, see:
http://turroserver.chem.columbia.edu/surfaceplasmons/pdf/20_csr_35_209_plasmonreview.pdf
and
http://photonicswiki.org/index.php?title=Gold_Nanoparticles_%E2%80%93_Surface_Plasmon_Resonance
For nanostructures, it depends of the structure (bumps, grids, 2D, 3D, ...), but for a periodic structures, as photonic crystals ,you have photonic bandgap as electron bandgap for semiconductors but for photons. As instance, take a look at:
http://en.wikipedia.org/wiki/Photonic_crystal
You can see these natural effects of color of photonic crystals on some butterfly wings.
Kind Regards
Note the difference in scale: if you want surface plasmons in the optical range, you need particles with diameters typically
Agreed. Periodic structures in the order of wavelength such as a quarter or one third of wavelength acts as a grating. However, due to interference as well as scattering the color and its hue varies.
I agree with Jerome regarding nanoparticles when these are made of metal. For semiconducting particles such as CdS or PbS (or many others), the quantum confinement results in a discretization of the electronic states (which are continuous in bulk materials) and a bandgap widening. Usually, these two factors combined together allow the nanoparticles to become strongly fluorescent (flashy color when illuminated with a UV light) and one can select the actual color by simply controlling the size (size => bandgap => radiation frequency).
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