Study On Fluorescent Nano-Silica Fingermark Reagent Functionalized By Carboxyl And Sulfonic Group

Fingermark is one of the most common forensic mark evidences,and it is widely used in individual identification as well.Since the evolution of criminal activities,it is more and more difficult to detect fingermarks in crime scene,and the more efficient fingermark developing methods are needed.Nano materials has been getting more attention because of their excellent properties,the high absorption ability,the unique fluorescence,and the surface-functionalized ability.The Nano-Fingermark methods have become one of the advanced trends of fingermark technologies.With the extension of nanoparticle technique,the Nano dust is threating the technicians'health,and causing the environment pollution.For developing an efficient and safe method,it is meaningful to establish the new method,Anionic Nanosuspension Reagent.In this research,the advances in fingermark detection were summarized,especially Nano fingermark techniques and Nano-silica.According to surface functionalization reaction,the carboxyl and sulfonic Nano SiO2 were synthesized as the fluorescent anionic nanoparticles,and each of them was used for fingermark detection to reduce the Nano-dust suspending in the air.Both of them showed strong affinity with the fingermark residue.The structure and properties were characterized.The method of the two kinds of Nano Particles Reagent for fingermark detection was optimized,and a simple apparatus for“on-site”fingermark detection was designed.The main research contents are listed as follows:1.Nano silicon dioxide,Amino Nano SiO₂ and thiol Nano SiO₂ were synthesized by tetraethoxysilane,3-Aminopropyl triethoxysilane and 3-Mercaptopropyl triethoxysilane.In this dissertation,the reaction was initiated in inverse microemulsion system by ammonia,and the Rubpy was used to make the product photoluminescent.The Anionic Nano-silica fluorescent fingermark reagent,the carboxylic SiO₂ and sulfonic SiO₂,were prepared by Succinic Anhydride and Hydrogen Peroxide,respectively.2.The physical parameters of all the nanoparticles,including the morphology,the particle size distribution,the fluorescence and electrical property,were characterized by TEM,FTIR,fluorescence spectrum and Zeta-DLS tester respectively.The diameters of these two nanoparticles are 44 nm and 42 nm.The DLS diameters of them are 122.42 nm and 110.1 nm respectively.It was turned out that the nanoparticles could produce highest fluorescence when the concentration of Rubpy was set as 15 mmol/L.Under the 365 nm UV lump,the fingermarks pictures were caught and recorded by digital camera with 550 nm filter.Because of the negative charge density,the dispersibility and stability of the sulfonic SiO₂ are better than the carboxylic suspension,and both of them are better than traditional Small Particle Reagent.3.Considering pH value,detecting time and suspension concentration,the best formula of the Nano Particles Reagent was determined by orthogonal test to study the detecting process.The fingermarks on three different surfaces were detected by the carboxylic nanosuspension for5 min in the condition of pH 2.9 and double dilution.The optimum conditions of sulfonic nanosuspension system are pH 2.5,4 times dilution and 5 min soaking.4.Comparing the difference of fingermarks developing results between the carboxyl and sulfonic system,the detecting mechanism was analyzed.And then,the aged fingermarks kept for a month on the HDPE and the aluminum foil could be developed well by these two Nano Particle Reagents.It showed better resolution than traditional SPR for the minutiae display.The correlation between electrical properties and pH was analyzed.At last,to apply this method to crime scene“on site”detection,a simple apparatus was designed to detect fresh fingermarks.