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Texas Technical University (2002) has developed a method for photoluminiscent
detection of latent fingerprints. This is achieved by binding quantum dots to fingerprint
residues, illuminating them with the appropriate spectrum of light and detecting the
fluorescence. Quantum dots of cadmium sulphide, cadmium selenide or indium phosphide
of less than 10 nm diameter have been attached to latent fingerprint using encapsulating
agents such as fatty acids or amino acid components. The excitation of the quantum dot
is carried out using a laser of near ultra-violet wavelength or filtered lamp (see Figure
4.6).
Figure 4.6 Fingerprint detected on a soft drink can
The University of Sunderland has developed fluorescent nanoparticles for identifying
latent fingerprints. These are produced as sol-gel particles in the presence of fluorescent
dye derivatives. Nanoparticles with intrinsic fluorescence such as cadmium sulphide and
cadmium selenide may also be used. Spherical nanoparticles with diameters between 30-
500 nm have been produced. A variety of fluorescent dyes such as Texas red-labelled
gelatin can be used in the process of developing the nanoparticles. These nanoparticles
are coated with hydrophobic molecules such as phosphatidylcholine and
phosphatidylethanolamine. Sol-gel derived nanoparticles with an embedded Texas Redporcine
thyroglobulin conjugate have been shown to bind latent fingerprints (University
of Sunderland, 2004).
In comparison with metal particles used in “traditional” fingerprint analysis, the small
size of nanoparticles makes it possible to discern the substructure of the print with
greater detail and accuracy. The advantage of this technique is a better definition of
fingerprints recorded from crime scenes. The technique not only enhances the sensitivity,
but also makes the identification easier by allowing even a small part of the print to
result in identification (see Figure 4.7).
Figure 4.7 Image of partial latent fingerprint
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