Luminescence detection of latent fingermarks on non-porous surfaces with heavy-metal-free quantum dots

Strongly Fluorescent Conjugated Polymer Nanoparticles in Aqueous Colloidal Solution for Universal, Efficient and Effective Development of Sebaceous and Blood Fingerprints

Taking the same developing strategy for different types of latent fingerprints is helpful in improving the efficiency of criminal investigation. Here we advanced a new strategy based on amino-functionalized poly(p-phenylenevinylene) nanoparticles (PPV-brPEI NPs) in aqueous colloidal solution as the developing reagent. The desirable amino functionality and strong emission of NPs were simultaneously realized by adding branched polyethyleneimine (brPEI) during the process of thermal elimination of the PPV polymer precursor. The NPs were demonstrated to have negligible effects on the extraction of biological information from DNA. Using the PPV-brPEI NPs-soaked cotton pad, both latent sebaceous fingerprints (LSFPs) and latent blood fingerprints (LBFPs) can be effectively developed on different nonporous substrates. This strategy was highly sensitive and effective for aged, contaminated and moldy fingerprints. Additionally, the developed fingerprints could tolerate humidity environment and the alcohol atmosphere. The mechanism investigation suggests that interaction between PPV-brPEI NPs and sebum ingredients contributes to the development of LSFPs and interaction between PPV-brPEI NPs and proteins in blood contributes to the development of LBFPs, but the former is not as stable as the latter. This work provides a simple, environment/operator-friendly strategy for efficient fingerprint development, which is very promising for practical criminal investigations.

Mind the gap: The challenges of sustainable forensic science service provision

Recent worldwide humanitarian and security efforts reflect the growth of forensic science as a global practice supporting peace, prosperity, and justice. While the dominance of the Global North in published research and public attention may suggest that this practice is universally well-developed, many Global South jurisdictions are at a stark disadvantage in resourcing and technological capabilities. Continued development of forensic science as an international endeavour requires a narrowing of inequalities between jurisdictions, in line with the United Nations Sustainable Development Goals. Here we propose a framework of principles for the sustainable provision of transparent, high-quality forensic services meeting jurisdictional needs and limitations. We illustrate how this concept of 'frugal forensics' can be applied in the context of latent fingermark detection in two Global South jurisdictions, and how quality assurance frameworks can be developed to support this service.

Eu-Doped Pyrochlore Crystal Nano-Powders as Fluorescent Solid for Fingerprint Visualization and for Anti-Counterfeiting Applications

Undoped Y₂Sn₂O₇ and Eu³⁺ doped Y₂Sn₂O₇ samples with doping concentrations 7%, 8%, 9%, and 10% are successfully synthesized by the co-precipitation method. A complete structural, morphological, and spectroscopic characterization is carried out. XRD measurements reveal that samples crystallize in the pure single pyrochlore phase and Eu³⁺ ions occupy sites with D_3d symmetry. After mechanical grinding, the average crystallite size is less than 100 nm for all compositions. Optical characterization shows emission from the ⁵D₀ level towards the lower lying ⁷F_0,1,2,3,4 levels. The CIE color coordinates of all the pyrochlore phosphors are very close to those of the ideal red light. For the visualization of latent fingerprints, different surfaces are tested, including difficult ones (wood and ceramic), with excellent results. All three levels of fingerprint ridge patterns are visualized: core (Level 1), bifurcation and termination (Level 2), and sweat pores (Level 3). Moreover, our nano-powders are used to prepare a stable fluorescent ink.

Preliminary studies into fluorescent semiconductor nanorods for the detection of latent fingermarks: Size matters, shape matters

The effect of the shape of semiconductor nanocrystals on their performance for visualising latent fingermarks was investigated for the first time. Highly luminescent CdSe/CdS core/shell nanocrystals in rod and spherical shapes were synthesised in organic solvent and transferred to aqueous solution using ligand exchange. The 3-mercaptopropionic acid coated nanorods and nanospheres were characterised using electron microscopy and UV-visible absorbance and luminescence spectrophotometry. A simple and rapid development of fresh to less than a week-old natural fingermarks from 4 donors (male and female) on non-porous surfaces including glass slides, aluminium foil and germanium disks using both CdSe/CdS core/shell nanorods and spherical dots was achieved, wherein nanorods demonstrated an enhanced development of ridge details in comparison to the spherical dots.