Application Research Of Rare Earth Upconversion Fluorescent Nanorods In Blood Fingerprints Detection

Fingerprints are one of the most useful types of physical evidence since they represent the unique ridge skin pattern of an individual's finger.The most commonly found fingermarks at crime scenes are typically latent.Until now,various techniques have been developed for fingerprint imaging.Photoluminescence is one of the most sensitive techniques for fingerprint detection.Upconversion nanoparticles are believed to be the key to the next generation of imaging which can emit strong visible fluorescence,suggesting that they can reach a high contrast in fingerprints detection.The excitation of upconversion nanoparticles often requires near-infrared radiation(NIR),this low energy radiation cannot cause autofluorescence from the substrates,thus decreasing the background interference in the detection of blood fingerprints.In this thesis,NaYF4:Yb,Er,Gd upconversion nanorods(UCNRs)induced by 980 nm NIR light were successfully used as a fluorescent label for the enhancement of blood fingerprints on various substrates,including non-infiltrating materials(glass,ceramic tile,aluminium foil,stainless steel sheet,coin and marble),and infiltrating materials(magazine cover and train ticket).Furthermore,Acid Yellow 7(AY7)was utilized to detect the blood fingerprints left on above-mentioned eight substrates for comparison.The results reveal that UCNRs are superior to AY7 on all test substrates.To further improve the sensitivity of the latent blood fingerprint detection,UCNRs functionalized with antibody-human hemoglobin(UCNRs/anti-hHb)were used to detect fingerprints through recognizing the corresponding antigens in the fingerprint residue.This approach can be successfully applied to detect latent blood fingerprints on non-infiltrating materials(stainless steel sheet,disc,glass and aluminium foil)and infiltrating materials(magazine cover,leather and wood).Moreover,to evaluate the actual efficiency of the blood fingerprint detection with UCNRs in criminal case,we get in touch with criminal science engineering office of local public security bureau.The results indicate that UCNRs possess the great practicality in forensic investigations.