Latent fingerprint enhancement via conducting electrochromic copolymer films of pyrrole and 3,4-ethylenedioxythiophene on stainless steel

Electrochromic visualization of latent fingermarks deposited on nonconductive surfaces

Electrochromic visualization of latent fingermarks has already been achieved on conducting surfaces such as stainless steel. However, their enhancement on non-conducting surfaces such as glass via electrochromism has not been reported. Considering the non-conductive nature of substrates, a layer of gold was introduced to the fingermark-bearing surfaces, in which gold was used as the cathodes to assemble electrochromic devices for visualization. The contact between gold nanoparticles of the as-obtained conducting layer in the fingermark region should be affected by the height difference within the fingermark, leading to conductivity differences, which give rise to coloration differences in electrochromic devices. It is demonstrated that 1,1'-dibenzyl-4,4'-bipyridinium dichloride can be used as the electrochromic chromophore for the visualization of latent fingermarks deposited on nonconducting surfaces, and the primary and secondary characteristic information can be obtained. The electrochromic visualization herein solves the problem of electrochromically enhancing latent fingermarks on non-conducting surfaces.

Non-destructive and simultaneous development and enhancement of latent fingerprints on stainless steel based on the electrochromic effect of electrodeposited manganese oxides

Latent fingerprints, as one of the most frequently encountered traces in crime scene investigation and also one of the largest sources of forensic evidence, can play a critical role in determining the identity of a person who may be involved in a crime. Due to the invisible characteristic of latent fingerprints, exploring efficient techniques to visualize them (especially the ones resided on metallic surfaces) while retain the biological and chemical information (e.g., touch DNA) has become a multidisciplinary research focus. Herein we reported a new and highly sensitive electrochemical interfacial strategy of simultaneously developing and enhancing latent fingerprints on stainless steel based on synchronous electrodeposition and electrochromism of manganese oxides in a neutral aqueous electrolyte. By utilizing a specially designed device for electrochemical testing and image capture, a series of electrochemical measurements, physical characterization and image analysis have been applied to evaluate the feasibility, development accuracy and enhancement efficacy of the proposed electrochemical system. The qualitative and quantitative analysis on the in situ and ex situ fingerprint images indicates that the three levels of fingerprint features can be precisely developed and effectively enhanced. Forensic DNA typing has also been performed to reveal actual impact of the proposed electrochemical system on subsequent analysis of touch DNA in fingerprint residues. The ratio of detected loci after electrochemical treatment reaches up to 98.5 %, showing non-destructive nature of this fingerprint development and enhancement technique.

Dansyl fluorophore functionalized hierarchically structured mesoporous silica nanoparticles as novel latent fingerprint development agents

A nanostructured hybrid material based on mesoporous silica nanoparticles (MCM-41) functionalized with chitosan and a fluorescent dye (dansylglycine), designated MCM-41@Ch@DnsGly, was synthesized and characterized with a view to its application for the visualization of latent fingerprints. These nanoparticles were applied as latent fingerprint developers for marks on surfaces of diverse chemical composition, topography, optical characteristics, and spatially variant nature, typical of forensically challenging evidence. For quality assessment of the enhanced fingermarks, the developed images were analyzed holistically using the UK Home Office scale, forensic protocols and, in terms of their constituent features (minutiae), using forensic software. Across a substantive collection of marks deposited on chemically diverse surfaces and subject to complex environmental and temporal histories, 94% of the enhanced images presented sufficient minutiae for comparison with model dactyloscopy images. This novel nanomaterial presents enhanced performance with significant promise for superior exploitation by forensic practitioners in the acquisition and analysis of crime scene evidence.

A novel 3D-printed portable electroplating device enhances latent fingerprints on metal substrates

This work introduces a 3D-printed portable electroplating device for the visualization of latent fingerprints (LFPs) on metallic substrates. An electroplating solution of Ag+-Cu2+ in a deep eutectic solvent (DES) is used. The electroplating is performed by two electrodes equivalent to an anode (+) and a cathode (-). The cathode is connected to the metal surface with the magnetic or alligator clip for carrying the LFP. The anode is connected to cotton dipped in the electroplating solution. The device was optimized in terms of the electroplating solution composition, and electroplating potential, current, and time. The device produced images with good resolution, revealing LFP ridges in minute detail of more than 12 points. The device also exhibited good repeatability and images were assessed against guidelines from the Centre for Applied Science and Technology (CAST) and the International Fingerprint Research Group (IFRG). The developed device could be applied to visualize LFPs in forensic investigations.

Voltammetric Determination of Hg2+, Zn2+, and Pb2+ Ions Using a PEDOT/NTA-Modified Electrode

A novel electrochemical sensor for determining trace levels of Hg²⁺, Pb²⁺, and Zn²⁺ ions in water using square wave voltammetry (SWV) is reported. The sensor is based on a platinum electrode (Pt) modified by poly(3,4-ethylenedioxythiophene) and N _α,N _α-bis-(carboxymethyl)-l-lysine hydrate (NTA lysine) PEDOT/NTA. The modified electrode surface (PEDOT/NTA) was prepared via the introduction of the lysine-NTA group to a PEDOT/N-hydroxyphthalimide NHP electrode. The (PEDOT/NTA) was characterized via cyclic voltammetry (CV), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The effects of scan rates on the electrochemical properties of the polymer electrode were also investigated. The electrochemical results were used to estimate the coverage of the electrode polymer surface and its electrostability in background electrolyte solutions. Several analytical parameters, such as polymer film thickness, metal deposition time, and pH of the electrolyte, were examined. Linear responses to Hg²⁺, Pb²⁺, and Zn²⁺ ions in the concentration range of 5-100 μg L^-1 were obtained. The limits of detection (LODs) for the determination of Hg²⁺, Pb²⁺, and Zn²⁺ ions were 1.73, 2.33, and 1.99 μg L^-1, respectively. These promising results revealed that modified PEDOT/NTA films might well represent an important addition to existing electrochemical sensor technologies.

Optimization of Electrochemical Visualization of Latent Fingerprints with Poly(Neutral Red) on Brass Surfaces

This study is focused on the visualization of latent fingerprints on brass surfaces using the method of electrochemical deposition of a polymer film based on poly(neutral red) (PNR). The experiment included (i) optimization of conditions of electrochemical deposition of PNR on brass surfaces, (ii) ATR-FTIR spectroscopic characterization of PNR-modified substrates, and (iii) identification of characteristic details on visualized fingerprints on fired brass cartridges. For electrochemical visualization, it is necessary to keep in mind both kind and “story” substrates. Experimental findings showed that electrochemical visualization carried out on brass plates is a step forward before known findings described in the literature and gives simultaneously a new approach for criminalists in the fight against crime.

Accuracy and reliability of tooth widths and Bolton ratios measured by ClinCheck Pro

INTRODUCTION

This study aimed to assess the accuracy and reliability of tooth widths and Bolton ratios measured in ClinCheck Pro.

METHODS

Five sets of typodonts were scanned using an iTero scanner, and the digital models were electronically transmitted to Align Technology for treatment planning. The typodont teeth were then segmented and measured using 3-dimensional optical profilometry (3D OP) and a calibrated digital caliper. Tooth widths estimated by ClinCheck Pro were compared with those measurements obtained using 3D OP and digital calipers. To determine the reliability of ClinCheck Pro measured tooth widths and Bolton ratios, the records of 30 consecutive patients treated with the Invisalign appliance without interproximal reduction were obtained. Values at the initial ClinCheck Pro treatment plan were compared with those from additional aligner scans. Accuracy, the agreement between methods, and reliability were investigated using the Bland Altman method.

RESULTS

A systematic under measurement was observed in the tooth widths measured by ClinCheck Pro (mean, 0.36 mm) compared with those obtained using 3D OP and digital caliper (individually segmented teeth). Although the overall reliability of ClinCheck Pro measured tooth widths was good (intraclass correlation coefficient, 0.96), the reliability of Bolton ratios was only moderate with wide confidence intervals.

CONCLUSIONS

ClinCheck Pro systematically underestimates tooth widths compared with 3D OP and digital caliper (individually segmented teeth). In addition, clinicians need to be cautious while relying solely on ClinCheck's Bolton ratios estimation for the treatment plan. These findings may be due to "shape assumptions" in the interproximal areas and could have clinical implications.

Vacuum metal deposition enhancement of friction ridge detail on ballistic materials

The efficacy of Gold/Zinc and Silver/Zinc vacuum metal deposition (VMD) protocols were assessed as stand-alone methods of fingermark enhancement on ballistic brass materials. The results demonstrate the effectiveness of VMD enhancement on a large pool of donors (n = 20), with potentially identifiable marks recovered for the majority of donors, including samples aged up to two months. Of the 20 donors a subset of six donors were selected to assess the capability of VMD enhancement on brass fired cartridge cases, from which some friction ridge detail (FRD) was recovered. Lastly, an attempt to understand which fingermark components are facilitators of VMD enhancement was made. Fingermark residue was extracted from brass tiles and fired cartridge cases before analysing chromatographically (GC-MS). Although some key components were indicated, further evaluation of all fingermark components is needed to draw firm conclusions as to the role each plays in VMD enhancement.

Diagnostics of skin features through 3D skin mapping based on electro-controlled deposition of conducting polymers onto metal-sebum modified surfaces and their possible applications in skin treatment

Analytical diagnostics of skin features was developed through application of portable and fast skin mapping based on electro-controlled deposition of conducting polymers onto metal-sebum modified surfaces. In this analytical diagnostic technique, the development of skin pattern is based on electropolymerization of conducting polymers within insulating barriers in skin stamp provided by natural sebum to monitor the 3D nature of various skin features. The recorded skin maps reach a μm-level resolution and are proved to be capable of recognition, enhancement, and reproduction of surface outlines of various skin topographies, subsequently assisting dermatological diagnosis. The technique can precisely record skin surface morphology and reflect the vertical dimension information within 10 min and is aimed to assist dermatologists working with patients suffering from skin diseases via recording or monitoring the skin surface conditions. Additionally, successful trials of loading and electro-controlled release of Cu²⁺ into/from the developed skin patterns reveals its potential to be also utilized for treatment of pathological skin conditions. Based on the developed analytical diagnostic technique, a well-designed 3D printed portable prototype device based on electrosynthesis of the conducting polymer powered by an ordinary battery (1.5 V) was tested and was found to have excellent performance in onsite 3D skin pattern reproduction from live human skin.

The effect of copolymerization and carbon nanoelements on the performance of poly(2,5-di(thienyl)pyrrole) biosensors

The development of biosensing interfaces based on copolymerization of benzenamine-2,5-di(thienyl)pyrrole (SNS-An) with 3,4-ethylenedioxythiophene (EDOT) is reported. Both homopolymer P(SNS-An) and copolymer P(SNS-An-co-EDOT) films were prepared and evaluated, in terms of biosensing efficiency, upon incorporation of carbon nanoelements (carbon nanotubes and fullerene) and cross-linking of glucose oxidase. The copolymer revealed superior performance as a biosensing interface as compared to the homopolymer structure or previously reported P(SNS) biosensors. The analytical characteristics and stability studies were performed both at cathodic potential, monitoring O₂ consumption, as a result of catalytic reaction of glucose oxidase towards glucose and at anodic potential, following the oxidation of the H₂O₂ produced during the catalytic reaction. Whilst the measurements on the positive side offered an extended linear range (0.01-5.0 mM), the negative side provided sensitivity up to 104.96 μA/mMcm^-1 within a shorter range. Detection limits were as low as 1.9 μM with Km value of 0.49 mM. Lastly, the most performant biosensing platforms, including copolymeric structure and CNTs were employed for analysis in real samples.

Novel Safranin-Tinted Candida rugosa Lipase Nanoconjugates Reagent for Visualizing Latent Fingerprints on Stainless Steel Knives Immersed in a Natural Outdoor Pond

Waterways are popular locations for the disposition of criminal evidence because the recovery of latent fingerprints from such evidence is difficult. Currently, small particle reagent is a method often used to visualize latent fingerprints containing carcinogenic and hazardous compounds. This study proposes an eco-friendly, safranin-tinted Candida rugosa lipase (triacylglycerol ester hydrolysis EC 3.1.1.3) with functionalized carbon nanotubes (CRL-MWCNTS/GA/SAF) as an alternative reagent to the small particle reagent. The CRL-MWCNTS/GA/SAF reagent was compared with the small particle reagent to visualize groomed, full fingerprints deposited on stainless steel knives which were immersed in a natural outdoor pond for 30 days. The quality of visualized fingerprints using the new reagent was similar (modified-Centre for Applied Science and Technology grade: 4; p > 0.05) to small particle reagent, even after 15 days of immersion. Despite the slight decrease in quality of visualized fingerprints using the CRL-MWCNTS/GA/SAF on the last three immersion periods, the fingerprints remained forensically identifiable (modified-Centre for Applied Science and Technology grade: 3). The possible chemical interactions that enabled successful visualization is also discussed. Thus, this novel reagent may provide a relatively greener alternative for the visualization of latent fingerprints on immersed non-porous objects.

Detection of Fingermarks-Applicability to Metallic Surfaces: A Literature Review

There are many different fingermark visualization techniques available, and the choice of methodology employed may be dependent on the surface type. This comprehensive review of the scientific literature evaluates the methodologies of fingermark enhancement methods that are applicable to metallic surfaces; optical, physical, chemical, and physicochemical methods are critically discussed. Methods that are currently used and those that have the potential to reduce the cost and time required to process evidence and increase the recovery rates are considered and are assessed against the Centre for Applied Science and Technology (CAST) and the International Fingerprint Research Group (IFRG) guidelines. The use of chemical imaging techniques in particular has increased the potential to recover fingermarks of sufficient quality for identification purposes. Presently, there appears to be a lack of detailed research pertaining to validation and thorough casework studies for fingermark enhancement techniques. Further studies incorporating these guidelines are recommended.

3-D and electrically conducting functional skin mapping for biomedical applications

Ex situ and in situ 3-D and electrically conducting mapping of the skin topography via electropolymerization of a conducting polymer on a previously sampled skin stamp or directly on the skin of a live human subject were performed here with the intention to be further used in biomedical applications.

Multichromic Polymers Containing Alternating Bi(3-Methoxythiophene) and Triphenylamine Based Units with Para-Protective Substituents

Two novel triphenylamine-based thiophene derivative monomers, 4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine and 4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine, were successfully synthesized. The corresponding polymers including poly (4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) and poly (4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) were electrochemically synthesized and characterized by multiple test method. The electrochemical measurements and spectroelectrochemical analyses revealed that both of the two polymers had quasi-reversible redox behavior and multi-electrochromic properties. The two polymer films showed reversible electrochemical oxidation, excellent optical contrasts in NIR region (62% at 1070 nm for the first polymer, and 86% at 1255 nm for the second polymer), satisfactory coloration efficiencies and fast switching times. The research on the application of the as prepared polymer in the fabrication of electrochromic device was also conducted, employing PCMTPA or PMMTPA as the anodically coloring materials.

Electrochemical synthesis, optical, electrochemical and electrochromic characterizations of indene and 1,2,5-thiadiazole-based poly(2,5-dithienylpyrrole) derivatives

PBDTA/PProDOT-Et₂ ECD showed high ΔT_max (43.8%) and satisfactory cyclic voltammetry stability, whereas P(BDTA-co-DTP)/PProDOT-Et₂ ECD showed high ΔT_max (44.0%) and coloration efficiency (504.6 cm² C⁻¹).

Comparative investigation of spectroelectrochemical and biosensor application of two isomeric thienylpyrrole derivatives

In the present work, we performed a comparative investigation of spectroelectrochemical and biosensor application of two isomeric thienylpyrrole derivatives.