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Security Crystals: NIR-To-NIR Upconverting Nanoparticles for Fingerprint Identification and DNA Extraction

NCJ Number
William M. Cross
Date Published
May 2022
99 pages

This document reports on a research project that had the overall goal of developing a safe, cost-effective system for sensitive and interference-free latent fingerprint identification, which will be based on near infrared (NIR)-to-NIR upconversion luminescence from optimized upconverting nanoparticles and be capable of capturing highly resolved fingerprint images under full ambient lighting, even on highly fluorescent surfaces; the system will also use nanoparticles to extract DNA from fingerprints.


This research report details a project aimed at developing a safe, cost-effective system for sensitive, interference-free latent fingerprint identification, which was achieved by meeting four objectives: optimize the synthesis, scale-up, and particle surface-modification of upconverting nanoparticles (UCNP) for near infrared (NIR)-to-NIR fingerprint imaging and DNA extraction; develop UCNP transfer procedures to minimize the airborne transport of nanoparticles; use statistical methods to evaluate UCNP fingerprints against standard procedures; and develop an optical-capture/image-processing device for implementation of a complete field system. The outcomes of the project include the researchers’ development of two complete systems, the first system utilized a laser to excite the UCNPs and a modified cellular phone as a camera to read the upconversion. The UCNPs in this system were tested and worked well on a wide variety of substrates, including fluorescent surfaces and under room lighting, and a platform for interpreting the fingerprint minutiae and matching fingerprints was also developed. The second system used a light emitting diode (LED)-based system to read the upconversion from the UCNPs on fingerprints; utilizing a 100 Watt, 980 nm emitting LED and a modified camera to collect the upconversion light. The LED-based system also included a water-cooling setup to keep the LED emitting light for longer. The researchers also used acetic acid to modify the surface of the UCNPs to make them more attractive to DNA molecules at a low pH and shed the DNA when the pH was raised sufficiently. As a result, the author reports a recovery of 15-20% of the DNA.