Application Of Nanoparticles In Latent Fingermark Detection

The fingerprints vary with each individual and are immutable as they are formeddeep under the skin. Moreover fingerprints leave marks on objects touched with barehands. Because of these characteristics, fingerprints are used for personal identification,verification, exposure and as proof of a crime on the trace and material evidence, and ithas been acclaimed as “the first material evidence” by global justice. Latent fingerprintscould be used for key qualitative case, although related researches have been conductedfor more than100years and this technology is becoming more and more mature, butthere are still a series of problems need to be solved. Nanoparticles, owning to nano size,have some special physical and chemical properties which bulk materials do not have.Combined with fingerprint residues like amino acid, grease and sweat, nanoparticles canemit photoluminescence after excitation. Through detection of photoluminescence ofnanoparticles, fingerprint image can be obtained clearly. With the help of this technology,we can effectively get the difficult, complex fingerprints that are left on various objects atthe crime scene by the high-tech armed criminals and we can overcome the problemsbrought by expensive cost of pure reagent and equipment and the hidden safety problems.At present, some domestic and foreign institutes and universities have organized researchon nanotechnology and achieved certain results in latent fingerprint detection, whichprovides us with new opportunities for the use of nanoparticles in forensic science.Relying on the literature analysis, inductive analysis, experimental analysis andcomparative analysis, this paper summarizes both common development method andnano materials development method for latent fingerprints, and tries to explore some newtechnologies and methods to develop latent fingerprints. We found that the nanoparticleshave some advantages compared with commercial powders, which is verified byexperiments. Finally, experimental results show that the application of nanotechnology inthe development of latent fingerprint has advantages such as feasibility and superiority.This paper is divided into five parts to explain these.In the first part, it mainly introduces the latent fingerprint status and discusses the advantages and disadvantages of common development methods, and the superiority ofnew nanoparticles development methods.In the second part, it gives an introduction of the types, methods steps of commonmethods and shows some difficult problems for practical use.In the third part, it introduces the application of nanoparticles, which are inwell-dispersed liquid or powder form, on latent fingerprints development in the forensicscience, focusing on introducing the metal, metal oxide, semiconductor nanoparticles andnanometer magnetic materials as dusting agents for a variety of latent fingerprint ondifferent material objects.In the fourth part, we have studied the magnetic properties of the experimental groupand its synthesis method. Relying on the present experimental conditions and equipments,we have changed the traditional silane with beads to explore a new method usingmercaptosilane combined with magnetic particles. We use the composite magneticnanoparticles in suspension form as small particle reagents and in an agglomerated formas dusting agents for latent finger prints. UV, TEM, document examination instrumentcharacterization show that the as-prepared Fe3O4@Ag core-shell nanoeggs (Fe3O4@Agnanoeggs)which can be fabricated easily possess good dispersion, stablility againstaggregation,optical properties as well as uniform size. In addition,they can providesignificant magnetic moment due to the Fe3O4core. The developed fingerprint is coarse,clear, smooth and detailed features are obvious, which has the best effect at PH7. At thesame time, Fe3O4@Ag nanoeggs can be used for fresh, old fingerprint development.In the last part, we have summarized the superiority of the application ofnanoparticles which still have some shortcomings in developing latent fingerprint. AndWe hope that by modifying the magnetic nanoparticles with the fluorescent reagent oralgal protein biological fluorescene, it can improve fluorescent substances, expanding therange of the using of Fe3O4@Ag nanoeggs in the complicated and difficult situation forlatent fingerprint development.