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. 2021 Sep 23;13(19):3220.
doi: 10.3390/polym13193220.

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

Gabriela Broncová  1 , Tereza Slaninová  1 , Miroslava Trchová  2 , Vadim Prokopec  1 , Pavel Matějka  3 , Tatiana V Shishkanova  1
Affiliations

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

Gabriela Broncová et al. Polymers (Basel). .

Abstract

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.

Keywords: brass cartridge; electrochemical deposition; latent fingerprints; poly(neutral red); visualization.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Scheme of visualization of fingerprint on brass cartridge using poly(neutral red) film.
Figure 2
Figure 2
Cyclic voltammogram of the deposition of a PNR layer on the applied fingerprint on (a) a brass plate and on (b) a brass cartridge. Black curve, supporting electrolyte (0.1 mol∙L−1 NaNO3); red curve, polymerization of 0.002 mol∙L−1 of NR. The potential range of polymerization was from −300 to 600 mV (SR 50 mV∙s−1, 6 cycles).
Figure 3
Figure 3
Optimization of the number of PNR deposition cycles for brass fingerprint visualization: (a) 10 cycles, (b) 8 cycles, (c) 9 cycles, and (d) 6 cycles.
Figure 4
Figure 4
Visualized fingerprint on brass plates. Images were taken with a binocular magnifier: (a) 10× magnification and (b) 30× magnification.
Figure 5
Figure 5
Image of details of the visualized fingerprint on the brass plate (a) obtained with a Leica microscope. Marked details: second level (markers): bifurcation (marked in white), eyelet (marked in red), and cross (marked in blue); third level: pores (marked in green). Image of details of the visualized fingerprint on the brass plate (b) taken with a Nikon eclipse light microscope. Characterization: top right, eyelet (marker) dimensions; bottom right, distance between papillary lines.
Figure 6
Figure 6
Infrared spectra of neutral red (NR) and the fingerprint and PNR film on the brass plate (B) in the wavelength range from (a) 2500 to 4000 cm−1 and (b) 1800 to 700 cm−1. B-FP, brass-fingerprint; B-PNR, brass-PNR film; B-FP-PNR, brass-fingerprint-PNR film.
Figure 7
Figure 7
Visualized fingerprints on fired brass cartridges. Images were taken with a binocular magnifier: (a,c) 10× magnification and (b,d) 30× magnification. Comparison of two different fingerprints: (a,b) relatively quality fingerprint with marked details (cross (marked in blue) and fork (marked in white)) and (c,d) partial (poor-quality) print; both prints applied before firing (unknown shooters).
See this image and copyright information in PMC

References

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