Zinc oxide quantum dots embedded in hydrophobic silica particles for latent fingermarks visualization based on time-gated luminescence measurements

Abstract

In this work we demonstrate a composite material based on silica particles. The particles have been doped with zinc oxide quantum dots which possess long living luminescence. The surface of the particles has been functionalized with phenyl groups using sol-gel process. The new material has been successfully applied for visualization of natural latent fingermarks on several surfaces, in particular, those showing their own luminescence and intensive background staining while using powder dusting, what is of the vital interest of forensic science. The time-gated imaging allows to overcome the background luminescence problem and surface functionalization increases the affinity of the particles to the fingermarks, what improves the selectivity of a new developing agent. The main novelty of the presented approach is the use of composite material that combines two main features—long lifetime luminescence and the ability to preferentially attach to the fingermark, due to hydrophobic interactions. Moreover,the utilization of deposition from the suspension instead of simple powder dusting allows for development of latent fingermarks on the surfaces that are difficult to work with powders (e.g. sticky side of the adhesive tape).

In Situ Interactions of Eu(TTA)3(H2O)2 with Latent Fingermark Components—A Time-Gated Visualization of Latent Fingermarks on Paper

“…Luminescence lifetime measurements and time-gated imaging have been performed using the previously described home-made system. 19 The system is composed of the computer-controlled, water-cooled charge-coupled device (CCD) camera (HARDsoft Microprocessor Systems, Poland) and a 365 UV light source. The system allows for precise control over the excitation pulse length, delay to shutter, shutter time, and time lag (Figure 1).…”

“…14−18 Although photoluminescence-based methods are sensitive and reliable, simple luminescence measurements may not be sufficient when dealing with samples showing strong background luminescence. 14,17,19,20 The background luminescence can decrease the image contrast or even make LFM development impossible. The background luminescence can be separated from the developed LFM luminescence using frequency filtration or time-gated measurements.…”

“…These kinds of fingermarks need to be developed with an appropriate technique before they can be used for comparison purposes . Even though many different LFM development methods have been described, the newer, more straightforward, reliable, more efficient, and user-friendly techniques are still highly demanded and successively investigated. − An important group of LFM development methods is based on photoluminescence. − Although photoluminescence-based methods are sensitive and reliable, simple luminescence measurements may not be sufficient when dealing with samples showing strong background luminescence. ,,, The background luminescence can decrease the image contrast or even make LFM development impossible. The background luminescence can be separated from the developed LFM luminescence using frequency filtration or time-gated measurements. ,,, …”

“…Aptamers, dendrimers, and antibodies have been used for selective tagging of the fingermark. Additionally, electrostatic, hydrophobic, , and lectin–glycoprotein interactions have been utilized. In many papers, a chemical reaction between developing agents and amine groups present in the fingermark material has been described. ,, All of the strategies mentioned above work best for the LFM deposited on non-porous substrates.…”

Hydrophobic‐Binding‐Driven and Fluoresence‐Free Development of Aged Fingerprints Based on Zinc Oxide Nanoparticles

“…[44] Zinc oxide nanoparticle (ZnO NP) is famous for its cheaper cost, versatile utilization, and ease of surface processing for decades. [45][46] However, recent concerns about ZnO NPs in forensics were concentrating on the optical modification as fluorescent probes for fresh fingerprints, [47][48][49][50][51][52][53] and little attention was paid on their hydrophobization for aged fingerprint development. On the one hand, ZnO NP has large SSA and strong chemical activity, making it has more active sites with fingerprint residues theoretically.…”