Rapid And Green Synthesis Of Nanomaterials And Applications In Latent Fingermarks Imaging

Fingermark is one of the most common and most important evidences in criminal scene investigation.Nanomaterials have shown good prospects for use in the development of latent fingermarks?LFM?,but most of them are solution regents,which may cause damage to fingerprint residues and fingerprint surfaces;at the same time,semiconductor quantum dots and rare earth doping nanomaterials are toxic,and their preparing procedures are time consuming.In this paper,rapid?within 1min?and green synthesis of non-toxic nanomaterials,including Fe₃O₄,C-dots,AuNCs were developed by microwave-assisted synthesis.In order to reduce the damage to fingermark residues and deposited surfaces,C-dots and AuNCs were immobilized into montmorillonite?MMT?clay matrix via electrostatic interaction,and they may be used as ponders.As-prepared nanomaterials have been successfully applied to develope LFM on glass,ceramics,paper,plastics,metals,paints and other surfaces.All of the nanomaterials prepared in this paper owning the characteristics of rapid preparation,non-toxicity,strong magnetism or fluorescence,and non-destructive to fingermark residues and deposited surfaces.Furthermore,it was proved that as-prepared nanomaterials showed no significant effect on subsequent touch DNA extraction and STR typing in LFM.The main achievements of this research are summarized as following:First,magnetic Fe₃O₄ nanoparticles were synthesized and successfully used in LFM imaging.Due to its ultra fine size,magnetic,low cost,Fe₃O₄ nanoparticles are promising in LFM detection.In this section,novel Fe₃O₄ nanoparticles were synthesized by microwave irradiation,and well characterized.The process of synthesis was fast,simple,effective and environment friendly.The prepared magnetic Fe₃O₄nanopowder was applied in LFM imaging on various surfaces,and sharp and clear fingermarks with good contrast were visualized.Especially for the rough surface,the small,fine nano-sized magnetic powder demonstrated great advantages.Gold doped Fe₃O₄ magnetic nanoparticles were also prepared,which might be used to enhance the appearance of LFM imaging by the strong affinity between amino acids and proteins in fingermarks and Au in the material.As prepared Fe₃O₄ nanoparticles were also used in the enhancement of fingermarks fumed by super glue,and better enhancement effect than that of ordinary powder and magnetic powder was achieved.Second,non-toxic C-dots,AuNCs with strong luminescence were prepared by microwave assisted synthesis,and immobilized into MMT clay for LFM imaging.Aqueous C-dots and AuNCs have been used in LFM development,but aqueous reagents might bring some irreversible damages to fingermark risidues and objects.In addition,some of the studies were time-consuming.As-prepared C-dots@MMT nanocomposites powders owns good emission(300⁴00 nm,?_em,max=447 nm)and AuNCs@MMT nanocomposites powders owns strong red emission(?_em,max=655 nm).Due to their environmentally friendly preparation,time-saving procedure,user-friendly operation,low cost,efficient photoluminescence,as-synthesized nanocomposite powders were employed as an alternative florescent developing reagent for enhancing LFM deposited on various object surfaces.Especially for LFM on multicolor surfaces,as-prepared nanocomposite owned great advantages.Furthermore,AuNCs-BSA/MMT nanocomposites were synthesized in situ with microwave-assisted for better performance in LFM imaging.Compared with immobilization by electrostatic interaction,in situ synthesis has the advantages of good compatibility between the substrate and the nanoparticles,and high interfacial bonding strength.AuNCs were“grown”both inside and on the surface of BSA/MMT clay using one-step reduction of HAuCl₄ by BSA within 8s.The as-prepared AuNC-BSA/MMT nanocomposites emit intensive red and near infrared fluorescence and were successfully used in LPM imaging deposited on various object surfaces.Both of fingerprint and DNA are very valuable in crime scene investigation,and touch DNA profiling in fingermarks is more and more popular.Moreover,the influence of dusting by as-prepared pondowers on subsequent touch DNA typing in LFM were studied.It was found that for all of the three obtained powder,including Fe₃O₄nanoparticle,AuNCs@MMT and C-dots@MMT nanocomposites,no significant difference on DNA typing results for the same fingerprint donor.The result showed that as-prepared pondowers caused no damage to fingerprint residues...