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Nanocrystals have numerous applications in thin films. A key one is as gas sensors. The small nanocrystals can respond to gases by redox reactions that cause conductivity changes or by changing colour in some cases.
In the first image above we show gold nanocrystals dispersed into titania thin films using sol-gel processing. The annealing temperature controls the colour because the colour depends on the matrix refractive index. Annealing causes condensation of the alkoxide groups and densification of the titania leading to a red-shift in the spectrum [1].
The spectra in the second image show lasing from QDs dispersed in zirconia waveguides. Pumping with an 800nm Ti:Sa laser leads to gain and to lasing when more than one exciton is created by the pump laser within the nanocrystals.
D.Buso et al. AFM 17, 347-54 (2007)
J.Jasieniak et al. Adv Mat. (in press)
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