Examination of Firearms Review: 2007 to 2010 - Interpol

interactions. According to the authors, this nanopowder detects fingermarks on a
wide range of surfaces (i.e., porous and non-porous, as well as white and
multicoloured). It is particularly suitable for detecting fingermarks on glossy items, or
on moist and sticky surfaces.
Choi et al considered the use of ZnO nano-sized particles to be dusted or applied as
small particle reagents (SPR) (269). Processed fingermarks were characterized by a
visible fluorescence when illuminated with a long-range UV light source. ZnO-based
SPR gave good results for all the tested surfaces (i.e., glass, polyethylene,
aluminium), while dry dusting led to some background staining on polyethylene
surface. When compared with conventional commercial powders, ZnO particles were
less luminescent but showed excellent ridge detail, with minimum background
staining. The authors also tried to dope the powder using lithium ions, to enhance the
visible luminescence, but this did not significantly improve the results.
Cheng et al. considered the use of two phosphorescent, surface-functionalized
nanoparticles (i.e., doped LaF3 and ZnS) to detect trace biomaterials, such as the
ones contained in fingermarks (270). The functionalization was such that the
nanoparticles were water-soluble and functionalized with carboxylic groups (i.e. –
COOH) to target amine groups from the latent secretions. Positive results were
obtained for fresh fingermarks left on four tested substrates (i.e., aluminium, plastic,
glass, and quartz). The detection procedure consisted in putting the substrates in
contact with the nanoparticle solution for two hours.
Finally, a new trend consists in functionalizing nanoparticles with biomolecules to
take benefit of the highly selective antibody / antigen recognition process within the
fingermark detection mechanism (271, 272). This strategy is further detailed in the
next point.
As described in the previous section, Jones et al. compared four brands of nanosized
titanium dioxide to be used as powder suspensions on black insulating tapes
(244).
2.2.7 Antibody / Antigen recognition
The use of antibodies constitutes a new and efficient approach to
specifically target the secretion residue. We can distinguish methods using
a direct antibody / antigen labelling procedure to target naturally secreted
proteins (276, 277), from those using biofunctionalized nanoparticles to
target drug metabolites present in the secretion (271, 272, 278).
Hazarika et al. functionalized magnetic nanoparticles with a variety of antibodies to
detect a range of drugs (i.e., THC from marijuana and methadone) or drug
metabolites (of methadone and cocaine) in fingermarks left on glass slides (271, 272,
278). The procedure requires the substrate to be in contact with the nanoparticles for
15 to 30 minutes. One advantage of their method is that a magnet can be used to
remove the excess of (magnetic) nanoparticles (the unbound ones). The remaining
nanoparticles were fluorescently tagged before observation. Positive results were
obtained for the four drugs and metabolites tested, with visible third-level details such
as pores.
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