Advances in Fingerprint Technology.pdf

5 D0
7 F2
7 F1
7 F0
3 +
Eu
sensitizing
ligand
Figure 6.9 Ligand-to-europium energy transfer and europium luminescence
energy-level diagram (waved arrows denote radiationless transitions and straight
arrows radiative ones).
typically in crystalline form, become very small (i.e., of nanometer order in
size). Such nanoparticles can be quite robust. They are typically encapsulated
with ZnS, silica, or organic material. This capping is sometimes referred to
also as derivatization or functionalization, especially when an organic compound
is involved, which is sometimes also referred to as a surfactant. The
encapsulation amounts to covering the nanocrystal with a layer of material
that may serve a variety of functions, for example, passivation to optimize
luminescence efficiency, serving as a site for attachment of conjugating
ligands designed for specificity of chemical binding, serving this labeling function
itself, serving to solubilize the nanocrystal, and preventing aggregation of