ACS Nano http://doi.org/9ps (2015)

Credit: AMERICAN CHEMICAL SOCIETY

Studies suggest that functionalized gold nanoparticles could prove useful for the visualization of fingerprints that are invisible to the naked eye (so-called latent fingerprints). Kai Song and co-workers from the US and China tested an approach that makes use of gold nanoparticles functionalized with an amphiphilic block copolymer called PSMA-b. The fingerprint sample is first immersed in an aqueous solution containing the nanoparticles for 30–45 minutes. During this immersion period the treated gold nanoparticles interact with secretions in the fingerprint residue and electrostatic forces mean that the nanoparticles are preferentially deposited on the ridges of the fingerprint. The resulting nanoparticle pattern (which follows the fingerprint pattern) is then imaged used either colorimetric imaging or photoacoustic imaging. The former allows easy visualization of the fingerprint while the latter provides better contrast and allows the study of fine features such as pores and ridges with high resolution. The use of photoacoustic imaging also offers the possibility for detecting the presence of trace samples of drugs or explosives in the fingerprint residue if gold nanoparticles functionalized with a suitable material are employed. The researchers trialled the scheme with a variety of porous and non-porous samples including paper, plastic tape, paper money, glass and a silicon wafer.