Department of Trace Examination, National Police University of China, Shenyang, Liaoning, 110035, PR China; Research Centre of Crime Governance in the New Era, Criminal Investigation Police University of China, Shenyang, Liaoning, 110035, PR China.
Department of Trace Examination, National Police University of China, Shenyang, Liaoning, 110035, PR China.
Talanta. 2021 Aug 15;231:122138. doi: 10.1016/j.talanta.2021.122138. Epub 2021 Mar 2.
Fluorescent nanoparticles (NPs) have been used to develop latent fingerprints with enhanced contrast. However, a method for quantifying the contrast is still lacking, making it impossible to achieve quantitative comparison in the contrast enhancement between different fingerprint developing agents. Here we proposed a new method to quantify the developed contrast using two indexes when fluorescent NPs were used to develop the latent fingerprint. One is the intensity index (I) defined as the ratio between the integrated fluorescence intensities of the signal and background in the fluorescence spectra of the developed fingerprint. Another is the chroma index (C) determined from the color difference between developed fingerprints and their substrates in the chromaticity graph. We defined the developed contrast as the product of the chroma index and the common logarithm of the intensity index (C·lg I), and validated this method using both down- and up-conversion fluorescent NPs and on a variety of different substrates (glass, marble, red paper and money). We showed that the developed contrast quantified by our method effectively reflected the true contrast but the intensity or chroma index alone was not always effective. This work opens up a new avenue to quantifying and enhancing the developed contrast.
荧光纳米粒子 (NPs) 已被用于开发具有增强对比度的潜在指纹。然而，目前仍然缺乏一种量化对比度的方法，使得无法在不同指纹显影剂之间实现对比度增强的定量比较。在这里，我们提出了一种新的方法，当使用荧光 NPs 开发潜在指纹时，使用两个指标来量化开发的对比度。一个是强度指数 (I)，定义为指纹荧光光谱中信号和背景的积分荧光强度之比。另一个是色度指数 (C)，它是从显影指纹与其衬底在色度图中的色差确定的。我们将开发的对比度定义为色度指数和强度指数的常用对数的乘积 (C·lgl)，并使用下转换和上转换荧光 NPs 以及各种不同的衬底（玻璃、大理石、红纸和钞票）对该方法进行了验证。我们表明，我们的方法量化的开发对比度有效反映了真实对比度，但强度或色度指数本身并不总是有效。这项工作为量化和增强开发对比度开辟了新途径。
