羧基修饰纳米SiO2荧光指印试剂的制备与应用

指印是一种重要的证据形式，它百年以来持续成为法庭科学领域的研究重点。在实践中，已经得到广泛推广的粉末法和熏显法对环境和工作人员的身体健康构成了重大威胁。近年来发展的纳米悬浮液显现指印的方法能够有效减少纳米粉尘在空气中的悬浮，降低对使用者健康和环境的侵害，并且规避了悬浮液制备过程中分散剂的使用以及有机染料溶液的处理等瓶颈。因此，关注纳米二氧化硅荧光指印显现试剂的制备与应用：首先，利用反相微乳液法制备了掺杂氯化三（2,2’-联吡啶）钌（Ⅱ）·六水化合物的荧光型纳米二氧化硅颗粒；随后，通过氨基硅烷偶联剂的氨基改性以及与丁二酸酐的氨解反应，使用两步法实现了表面羧基化阴离子修饰的荧光二氧化硅纳米材料的合成；此外，利用红外吸收光谱对纳米二氧化硅，以及目标产物的表面氨基、羧基等化学修饰基团进行表征，并测定了不同修饰产物在水相中的表面电性能以其水合半径；通过紫外可见光吸收光谱和分子荧光光谱仪对材料的荧光性能做了检测，测试了不同染料浓度产物的荧光强度；对新型纳米材料在指印显现中的应用条件进行了系统考察，通过正交试验设计法，全面探究了pH值、母液稀释倍数和显现时间等重要因素对于指印显现效果的综合影响，并最终确定了此种显现试剂的最佳显现条件；论文最后依据上述优化实验条件对捺印在玻璃非渗透性光滑客体表面的指印样品的显现效果进行了系统评价。实验结果表明：产物悬浮液与染料溶液的紫外可见吸收光谱之间并未发生明显的红移或蓝移，这意味着二氧化硅包覆对于荧光染料分子结构没有显著影响；根据染料浓度与产物荧光强度之间的变化关系可知，最佳染料掺杂浓度为15 mmol·L-1；纳米材料的表面氨基化和羧基化修饰已经成功，其最佳激发光源波长为375 nm；Zeta电位-DLS测试结果印证了氨基质子化带正电、羧基电离带负电的纳米材料电学性能，此外羧基化前后纳米二氧化硅颗粒负电荷密度的显著改变也为基于静电吸附作用的指印显现方法灵敏度的提升奠定了基础；使用悬浮液法对前述优化后的合成产物进行指印显现方面的应用，其最佳显现条件为溶液pH值为2.8、母液稀释倍数为2倍且显现时间5 min，其对非渗透性客体表面的新鲜指印及陈旧指印均具有良好的显现效果，部分情况下甚至可以实现三级指印特征的理想显现效果。

Synthesis of Carboxyl Functionalized Photoluminescent Nano-SiO2 Fingermark Reagent

Fingermark detecting is very important for individual identification over the past decades. However, the health of forensic technicians and our environment had been damaged seriously by these methods. The new method of Nano Particles Reagent for fingermark detection can effectively reduce the nano-dust suspending in the air, andrecover the technicians’ health and environment as well. It also resolved the problem of the disposal of dispersant and organic dye. The research focuses on the synthesis of fluorescent nanosilica functionalized by carboxyl and the migrating of latent fingermarks. In this study, nanoscale silicon dioxide doped with fluorescent dyes was prepared by reverse microemulsion method, and the Tris(2,2’-bipyridine)ruthenium(Ⅱ) chloride hexahydrate was used to make the nano silica luminescent. Amino modification was accomplished by aminosyl-silane coupling agent. Carboxyl modified fluorescent fingermark developing reagent based on silica nanoparticles was prepared by ammonolysis of butyl two anhydride. The surface chemical groups, fluorescence properties, dispersibility in aqueous phase, surface electrical properties and particle size of the target objectives were characterized by infrared spectroscopy, ultraviolet-visible absorption spectroscopy, Zeta potential-DLS tester and micro-spectrophotometer, respectively. The influence of dye concentration on the fluorescence intensity of products was studied. It was found that the electrical ionization efficiency, the concentration of nano-particles and the migrating time can directly impact the development. As a result, the three-factor orthogonal experiment was designed to explore the effects of pH value, dilution multiple and display time on the display effect in this study. The developing conditions of the fingermarks deposited on aluminum foil surface were preliminarily explored. Some conclusion was presented that the molecular structure of fluorescent dye remained comparing to the maximum absorption before reacting with silica, and 15 mmol·L-1 was the best concentration. The surface modifications of amino and carboxyl were accomplished, and the 375 nm was the exciting wavelength. The nanostructure of the objective in suspension was confirmed. According to the charge characteristic in the suspension, it was proved that the modified silica was positively and negatively charged by amino and carboxyl groups respectively. The product could migrate the fresh and aged fingermarks on non-porous surface in the condition: pH 2.8, double dilution, and 5 minutes. The carboxylic nano-SiO₂ suspension is an effective method of fingermarks detecting, and according to the smoothness degree, the more detailed features could be obtained.