Wang Meng, Zhu Ye, Mao Chuanbin
†Department of Trace Examination, National Police University of China, Shenyang 110035, People's Republic of China.
‡Key Laboratory of Impression Evidence Examination and Identification Technology, Ministry of Public Security, Shenyang 110035, People's Republic of China.
Langmuir. 2015 Jun 30;31(25):7084-90. doi: 10.1021/acs.langmuir.5b01151. Epub 2015 Jun 19.
Fingerprints at crime scenes are usually latent. The powder-dusting method is the most commonly used procedure for developing latent fingerprints in forensic science. However, the traditional powder-dusting method has characteristics of low sensitivity, low contrast, high background noise, and high autofluorescence interference. To overcome the drawbacks faced by the traditional method, we first optimized an oleic acid-based solvothermal approach for the synthesis of NaYF4:Yb,Er fluorescent upconversion nanoparticles (UCNPs) with the highest possible fluorescence intensity under near-infrared (NIR) irradiation. To optimize the synthesis, we studied the effects of the reaction time, reaction temperature, and volume of oleic acid on the size, phase composition, and UC fluorescence intensity of the UCNPs. We then used the resultant UCNPs to fluorescently label the fingerprints on various smooth substrates to improve the development of latent fingerprints because the UCNPs could undergo excitation under 980 nm NIR light to emit visible light. Latent fingerprints on three major types of smooth substrates were studied, including those with a single background color (transparent glass, white ceramic tiles, and black marbles), with multiple background colors (marbles with different complex surface patterns) and with strong background autofluorescence (note papers, Chinese paper money, and plastic plates). Compared with fingerprint development using traditional powders such as bronze powder, magnetic powder, and green fluorescent powder, our development procedure using UCNPs is facile and exhibits very high sensitivity, high contrast, low background interference, and low autofluorescence interference. This work shows that UCNPs synthesized under optimized conditions are a versatile fluorescent label for the facile development of fingerprints and can find their practical applications in forensic sciences.
犯罪现场的指纹通常是潜在的。粉末刷显法是法医学中用于显现潜在指纹最常用的方法。然而，传统的粉末刷显法具有灵敏度低、对比度低、背景噪声高和自发荧光干扰高的特点。为了克服传统方法面临的缺点，我们首先优化了一种基于油酸的溶剂热法，用于合成在近红外（NIR）照射下具有尽可能高荧光强度的NaYF4:Yb,Er荧光上转换纳米颗粒（UCNPs）。为了优化合成过程，我们研究了反应时间、反应温度和油酸体积对UCNPs的尺寸、相组成和上转换荧光强度的影响。然后，我们使用所得的UCNPs对各种光滑基材上的指纹进行荧光标记，以改善潜在指纹的显现效果，因为UCNPs可以在980 nm近红外光下被激发发出可见光。我们研究了三种主要类型光滑基材上的潜在指纹，包括单一背景颜色的（透明玻璃、白色瓷砖和黑色大理石）、多种背景颜色的（具有不同复杂表面图案的大理石）以及具有强烈背景自发荧光的（便签纸、中国纸币和塑料板）。与使用青铜粉、磁性粉和绿色荧光粉等传统粉末进行指纹显现相比，我们使用UCNPs的显现方法简便，并且具有非常高的灵敏度、高对比度、低背景干扰和低自发荧光干扰。这项工作表明，在优化条件下合成的UCNPs是一种通用的荧光标记物，可用于简便地显现指纹，并能在法医学中找到实际应用。
