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Advances in Fingerprint Technology.pdf

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step 1<br />

step 2<br />

step 3<br />

f<strong>in</strong>gerpr<strong>in</strong>t<br />

conjugat<strong>in</strong>g<br />

ligand<br />

Figure 6.8 Basic scheme for lanthanide-based chemical f<strong>in</strong>gerpr<strong>in</strong>t development.<br />

light and transferr<strong>in</strong>g the excitation energy to the lanthanide ion by an energy<br />

transfer process ak<strong>in</strong> to Forster <strong>in</strong>termolecular energy transfer. 9 For dust<strong>in</strong>g<br />

and sta<strong>in</strong><strong>in</strong>g, the conjugat<strong>in</strong>g ligand is not needed. Figure 6.9 shows the<br />

energy-transfer scheme for europium complexes. 9 At the time of this writ<strong>in</strong>g,<br />

problems associated with chemical process<strong>in</strong>g of f<strong>in</strong>gerpr<strong>in</strong>ts older than about<br />

1 week still persist. Furthermore, the excitation of lanthanide complexes<br />

demands ultraviolet (UV) light and thus is not compatible with many laser<br />

systems currently <strong>in</strong> use <strong>in</strong> f<strong>in</strong>gerpr<strong>in</strong>t laboratories. An ultraviolet-capable<br />

argon-ion laser is a suitable excitation source. When time-resolved imag<strong>in</strong>g<br />

is not mandatory — namely, when background fluorescence is not a<br />

problem — the f<strong>in</strong>gerpr<strong>in</strong>t work can utilize an ord<strong>in</strong>ary UV lamp. Exploration<br />

of f<strong>in</strong>gerpr<strong>in</strong>t process<strong>in</strong>g with photolum<strong>in</strong>escent semiconductor nanoparticles<br />

as well as dendrimer application to f<strong>in</strong>gerpr<strong>in</strong>t development were<br />

<strong>in</strong>itiated about a year ago to remedy the above problems. These nanoparticle<br />

approaches are promis<strong>in</strong>g, especially <strong>in</strong> the time-resolved context, and are<br />

taken up <strong>in</strong> the rema<strong>in</strong>der of this chapter. It is anticipated that they will form<br />

the next milestone <strong>in</strong> f<strong>in</strong>gerpr<strong>in</strong>t detection methodology.<br />

Photolum<strong>in</strong>escent Semiconductor Nanocomposites<br />

lanthanide<br />

sensitiz<strong>in</strong>g<br />

ligand<br />

Semiconductor materials such as CdS, CdSe, CdTe, InP, and InAs, which normally<br />

are not lum<strong>in</strong>escent, can become <strong>in</strong>tensely lum<strong>in</strong>escent when particles,

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