Fig. 1. Image of latent fingerprint deposited on white tile and developed by magnetic powders (a); and gray curves corresponding to developed fingerprint and its substrate characterized by Image J software (b)^[20]

Fig. 2. Scheme for quantifying the contrast of fingerprints developed with fluorescent nanomaterials by means of spectral analysis^[15]

Fig. 3. Images of latent fingerprints deposited on various substrates and developed by different powders
(a): Bronze powders^[20]; (b), (e): Magnetic powders^[20]; (c), (f), (g): YVO₄:Eu downconversion luminescent nanopowders^[15]; (d): LaPO₄:Ce, Tb downconversion luminescent nanopowders^[15]; (h): Green fluorescent powders^[21]; (i): NaYF₄:Yb, Er upconversion luminescent nanopowders^[21]

Fig. 4. Images of latent fingerprint deposited on marble and developed by rare earth nanocomplex suspensions (a), and corresponding magnified images (b)—(d): scar (b1), wrinkle (b2), spur (c1), termination (c2), bifurcation (c3, c4), and sweat pore (d)^[22]

Fig. 5. Images of latent fingerprints deposited on glass and developed by various powders
(a): Bronze powders; (b): NaYF₄:Yb, Er upconversion luminescent powders with particle size of nanoscale; (c): Microscale^[28];(a')—(c') are scanning electron microscope images of the developing powders corresponding to (a)—(c)^{[4, 28]}

Fig. 6. (a) Image of latent fingerprint deposited on black tile and developed by super glue fuming method; (b) gray analysis corresponding to papillate ridges and furrows characterized by Image J software^[75]

Fig. 7. Images of latent fingerprints deposited on glass and developed by different powders
(a): LaPO₄:Ce, Tb downconversion luminescent nanopowders; (b): Green fluorescent powders^[9]

Fig. 8. Strategies for enhancing the selectivity of latent fingerprint development and images of corresponding fingerprints
(a): Antibody combination^[77]; (a'): Aptamer recognition^[79]; (b): Electrostatic adsorption^[78];(c): Chemical bonding^[22]; (d): Hydrophobic effect^[29]

Fig. 9. Images of latent fingerprint deposited on glass and developed by LaPO₄:Ce, Tb downconversion luminescent nanopowders in bright field (a), and dark filed excited with 254 nm ultraviolet light (b); and corresponding STR fluorescent spectrum for touch DNA detection in developed fingerprint residuals (c)

Fig. 10. Scheme for fingerprint development and enhancement via electrodeposition of electrochromic Co₃O₄ films and subsequent touch DNA detection^[84]

Table 1. Summary of sensitivity research in latent fingerprint development

Table 2. Summary of selectivity research in latent fingerprint development