MgB2 based nanodispersion that I prepared appears golden yellow in color but its UV-VIS absorption spectra show absorption only in the UV region (< 300 nm). Usually, if we are seeing any color that means it is absorbing in the visible region but why our sample doesn't show any kind of absorption in the wavelength range of 300 nm - 1100 nm (i.e, visible to near infrared regions)?
Mie theory should answer your dilemma. I suspect it's because of the size of the particles - small (1 -2 nm) Au sols are yellow too. See:
February 25th, 2014 The life of Gustav Mie and the development of the Lorenz-Mie solution to Maxwell’s equations http://tinyurl.com/mt97tp3
MgB2 has already as a single crystal some very interesting color properties. You may know already the following paper, otherwise I highly recommend reading it:
Article Anisotropic optical conductivity and two colors of MgB2
Thank you, Thomas Mayerhöfer. I already knew this paper and it is mentioned that when E||c axis polarization occurs then MgB2 single crystals appear golden yellow color and it is due to sharp plasma edge at about 2.5 eV that is same as of gold. But if so then the nanodispersion that I get of golden yellow color should show an absorbance in the visible region but why it is in the UV region?
Did you also measure the reflectance of your sample apart from the transmittance? Could you also provide us your spectra?
Dear Dr. Alan,
The same thought I too had but I was not able to get that from DLS data. In DLS I always end up with no result as the instrument always shows out of range for my sample.
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