Problems of detecting sweat and grease deposits on porous surfaces are common for forensic practice, and usually, they are successfully resolved with the help of chemical methods. Meanwhile, the interaction process in the system “porous surface – deposit – chemical agent" concerning clarification and identification of the trends within chemical reaction is not reviewed in literature sufficiently. For more comprehensive research of this process, the authors of the article have conducted multiple experiments on the ninhydrin reaction with the sweat and grease of the deposits, analyzed the interaction of the chemical agent with the sweat and grease, with the properties of porous (paper) materials using electron microscopy, and also looked into the display features of pore and edgeoscopic signs in the deposits under different storage conditions.As a result of the research, it is shown that such parameters of deposits carriers (paper) as porosity and hydrophilic properties and ambient humidity as well as the time of storage have a significant influence on the process of detecting the sweat and grease deposits on porous surfaces and their quality.
The article reviews the main physical and physicochemical factors influencing the three-component system “fingerprint powder – prints bearing surface – sweat and grease print substance”. The authors propose new model compositions of fingerprint powders considering the reviewed common patterns: non-magnetic and luminescent magnetic. The features of prints bearing surfaces and developed fingerprint powders have been evaluated by applying electronic microscopy methods (scanning and probe microscopy). The authors have proven that the use of nano- and ultra disperse materials in the developed compositions (carbon nanotubes and shungite) enables to vary the sorption and adhesive capacity of fingerprint powders, which allows detecting fingerprints on varying surfaces with high selectivity toward the sweat and grease print substance and contrasting effect.
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