The fluorescent properties of semiconductor nanocrystals have drawn wide attention because of their potential use as labels in fluorescence bio-assays [25, 26,
84, 168–170]. When compared to dyes currently in use, the emission from fluorescent nanocrystals is brighter and sharper. Further, the emission can be brought
about by excitation over a broad range of wavelengths. It is therefore possible to
excite nanocrystals of several different sizes simultaneously with a single source
and obtain well resolved emission at different colours. In order that the nanoVolume /nm
3
Au
Pd
Cd
Ag
Local DOS
Fig. 4.24. (a) Variation of the nonmetallic band gap with
nanocrystal size in metal nancrystals. The bandgaps were
obtained based on scanning tunneling spectroscopic
measurements (reproduced with permission from [162]).
/
/
n
Fig. 4.25. Photoelectron spectra of Hg clusters of varying
nuclearity. The 6p feature moves gradually towards the Fermi
level, emphasizing that the band gap shrinks with increase in
cluster size (reproduced with permission from [165]).
4.4 Emerging Applications 79
84, 168–170]. When compared to dyes currently in use, the emission from fluorescent nanocrystals is brighter and sharper. Further, the emission can be brought
about by excitation over a broad range of wavelengths. It is therefore possible to
excite nanocrystals of several different sizes simultaneously with a single source
and obtain well resolved emission at different colours. In order that the nanoVolume /nm
3
Au
Pd
Cd
Ag
Local DOS
Fig. 4.24. (a) Variation of the nonmetallic band gap with
nanocrystal size in metal nancrystals. The bandgaps were
obtained based on scanning tunneling spectroscopic
measurements (reproduced with permission from [162]).
/
/
n
Fig. 4.25. Photoelectron spectra of Hg clusters of varying
nuclearity. The 6p feature moves gradually towards the Fermi
level, emphasizing that the band gap shrinks with increase in
cluster size (reproduced with permission from [165]).
4.4 Emerging Applications 79