Fingerprint Reagents with Dual Action: Color and Fluorescence

Explosive vapour/particles detection using SERS substrates and a hand-held Raman detector

We developed and optimized surface-enhanced Raman spectrometry (SERS) methods for trace analysis of explosive vapour and particles using a hand-held Raman spectrometer in the field. At first, limits of detection (LODs) using SERS methods based on a colloidal suspension of gold nanoparticles were measured under alkaline conditions and are as follows: pentaerythritol tetranitrate (PETN) (1.5 × 10⁻⁶ M, 6.9 ng), 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX), 8.1 × 10⁻⁶ M, 35 ng; urea nitrate (UN), 9.2 × 10⁻⁴ M, 165 ng; 2,4,6-trinitrotoluene (TNT), 1.1 × 10⁻⁷ M, 0.35 ng. We developed SERS substrates that demonstrate the wide applicability of this technique for use in the field for explosive vapour and particles adsorbed on a surface based on Au nanoparticles that were optimal for the detection of the target materials in solution. Au nanoparticles were modified onto quartz fibres or a polyurethane sponge for vapour/particles detection. SERS detection of vapours of 2,4-dinitrotoluene (2,4-DNT) and 1,3-dinitrobenzene (1,3-DNB) was shown by sampling vapours onto Au-modified quartz fibres followed by hand-held Raman analysis with estimated minimum detection levels of 3.6 ng and 54 ng, respectively. The detection of 2,4-DNT using sponge-based SERS decorated with Au nanoparticles was also demonstrated; however, the sensitivity was lower than that observed using quartz fibres. The detection of TNT on a surface was performed by utilizing quartz-fibres precoated with alumina and modified with Au nanoparticles, and the detection of 10 μg (0.53 μg cm⁻²) of TNT was demonstrated.

We developed and optimized surface-enhanced Raman spectrometry (SERS) methods for trace analysis of explosive vapour and particles using a hand-held Raman spectrometer in the field.

Enhancing the visualization of latent fingerprints by aggregation induced emission of siloles

Aggregation-induced emission was explored for the visual enhancement of latent fingerprints deposited on wet non-porous surfaces.

Microwave selective thermal development of latent fingerprints on porous surfaces: potentialities of the method and preliminary experimental results

The thermal development of latent fingerprints on paper surfaces is a simple, safe, and chemicals-free method, based on the faster heating of the substrate underlying the print residue. Microwave heating is proposed for the first time for the development of latent fingerprints on cellulose-based substrate, in order to add to the thermal development mechanism the further characteristic of being able to heat the fingerprint residues to a different extent with respect to the substrate, due to the intrinsic difference in their dielectric properties. Numerical simulation was performed to confirm and highlight the selectivity of microwaves, and preliminary experimental results point out the great potentialities of this technique, which allowed developing both latent sebaceous-rich and latent eccrine-rich fingerprints on different porous surfaces, in less than 30 sec time with an applied output power of 500 W. Microwaves demonstrated more effectiveness in the development of eccrine-rich residues, aged up to 12 weeks.

2-(2-Hydroxy-5-nitrobenzylidene)-1,3-indanedione versus Fluorescein Isothiocyanate in Interaction with Anti-hFABP Immunoglobulin G1: Fluorescence Quenching, Secondary Structure Alteration and Binding Sites Localization

The first step in determining whether a fluorescent dye can be used for antibody labeling consists in collecting data on its physical interaction with the latter. In the present study, the interaction between the 2-(2-hydroxy-5-nitrobenzylidene)-1,3-indanedione (HNBID) dye and the IgG1 monoclonal mouse antibody anti-human heart fatty acid binding protein (anti-hFABP) has been investigated by fluorescence and circular dichroism spectroscopies and complementary structural results were obtained by molecular modeling. We have determined the parameters characterizing this interaction, namely the quenching and binding constants, classes of binding sites, and excited state lifetimes, and we have predicted the localization of HNBID within the Fc region of anti-hFABP. The key glycosidic and amino acid residues in anti-hFABP interacting with HNBID have also been identified. A similar systematic study was undertaken for the well-known fluorescein isothiocyanate fluorophore, for comparison purposes. Our results recommend HNBID as a valuable alternative to fluorescein isothiocyanate for use as a fluorescent probe for IgG1 antibodies.

An assessment of the effectiveness of 5-methylthioninhydrin within dual action reagents for latent fingerprint development on paper substrates

A critical investigation of 5-methylthioninhydrin (5MTN) is presented as a 'dual action' formulation component for the development of latent finger marks on paper substrates. Preparation of a dual action reagent was performed by combining proportions of 5MTN and zinc chloride (ZnCl(2)) in a pre-mixed solution. Developed prints (deposited on filter paper substrates) could be subsequently visualised in both colour and fluorescence modes. Finger mark quality was graded using a quartered print approach for a number of reagent compositions to deliver an optimised formulation recipe. To fully appraise 5MTN in comparison to currently employed chemistries, this reagent was evaluated against three alternative amino acid selective reagents, ninhydrin, 1,8-diazafluorenone (DFO) and 1,2-indandione/ZnCl(2). Six common paper types were used for this purpose and split depletion finger marks from six donors were collected. Finger mark sets were also left for two days or two weeks to show the effect of ageing on development quality. For the first time, it was shown that 5MTN/ZnCl(2) is effective as a 'dual action' reagent under the United Kingdom climate conditions. However, results presented herein show that the existing recommended chemistries and the 1,2 indandione/ZnCl(2) process are all more effective than this new latent finger mark enhancement reagent. In a preliminary sequencing study, we show the effectiveness of the existing DFO-ninhydrin sequence over dual action reagents.

Forensic chemistry

Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence.