Use of conductive Ti2O3 nanoparticles for optical and electrochemical imaging of latent fingerprints on various substrates

The personal identification technology based on fingerprint features has great application value in the fields of public security and consumer electronics due to its extensiveness and reliability. However, current fingerprint development methods do not work efficiently for latent fingerprints (LFPs) deposited on some problematic objects. In this work, conductive Ti2O3 nanoparticles (NPs) with black color were used as a novel optical and electrochemical dual-mode enhancer for the development of LFPs with high sensitivity, resolution and low background interference on various substrates. For the majority of substrates, black Ti2O3 NPs were able to acquire the high-sensitivity optical development of LFPs (levels 1–3 features), which maybe result from spatially selective adhesion between Ti2O3 NPs and fingerprint residues. However, for dark substrates with strong background color interference, the obtained images from Ti2O3-developed fingerprints were severely blurry. Significantly, by virtue of the electroactivity of Ti2O3 powder, the Ti2O3-developed fingerprints could be further electrochemically imaged with high contrast and high resolution by scanning electrochemical microscopy (SECM) to eliminate background color interference. The current changes at the probe of SECM could reflect the pattern information of the fingerprint because the redox mediator could be regenerated at the surface of Ti2O3 powders adhered to the ridge regions. These results demonstrated that Ti2O3 NPs could be considered as a bi-functional developer for enhancing LFPs.