Investigation of the chemical origin and evidential value of differences in the SERS spectra of blue gel inks.
Investigation of the chemical origin and evidential value of differences in the SERS spectra of blue gel inks.
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DOI：
10.1039/c6an00972g
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发表时间：
2016-08
期刊：
影响因子：
--
通讯作者：
Y. Ho;Wendy W. Y. Lee;S. Bell
中科院分区：
文献类型：
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作者：
Y. Ho;Wendy W. Y. Lee;S. Bell
在633和785 nm激发下，掺银纳米粒子聚团的高可膨胀聚合物薄膜（poly-SERS薄膜）记录了原位干燥墨线及其组成染料的高信噪比、可重复的表面增强（共振）拉曼（SER(R)S）光谱。这使得不同油墨SERRS光谱差异的化学起源得以确定。对10种最常见的蓝色染料的纯样品的初步调查表明，具有非常相似化学结构的染料，如专利蓝V和专利蓝VF（仅相差一个OH基团）给出的SERRS光谱中，染料结构发生变化的唯一迹象是峰位置或相对强度的微小差异。13种凝胶笔墨水的SERRS研究与这一观察结果一致。在某些情况下，不同类型的钢笔的墨水可以被区分开来，即使它们是由一种单一的染料，如维多利亚蓝B（斑马苏拉利）或维多利亚蓝BO（飞行员Acroball），因为它们的主要染料不会出现在其他墨水中。相反，不同类型的笔（Pilot G7, Zebra Z-grip）也记录了相同的光谱，因为它们都具有相同的显性亮蓝G染料。最后，一些油墨含有染料的混合物，这些染料可以通过薄层色谱分离，并在用相同的聚sers薄膜分析之前从板上去除。例如，Pentel EnerGel墨水笔被发现给出了对应于Erioglaucine和Brilliant Blue g的TLC斑点。总体而言，本研究表明，基于化学相似但不同染料的不同墨水之间的光谱差异非常小，因此需要非常接近的SERRS光谱来进行自信的鉴定。Poly-SERS衬底通常可以提供所需的非常严格的再现性和灵敏度水平。这一点，再加上对相似颜色墨水之间观察到的差异背后的原因的认识，可以对墨水SERS的证据价值进行更有信心的评估，并且应该支持采用这种方法作为墨水法医检查的常规方法。
Highly swellable polymer films doped with Ag nanoparticle aggregates (poly-SERS films) have been used to record very high signal : noise ratio, reproducible surface-enhanced (resonance) Raman (SER(R)S) spectra of in situ dried ink lines and their constituent dyes using both 633 and 785 nm excitation. These allowed the chemical origins of differences in the SERRS spectra of different inks to be determined. Initial investigation of pure samples of the 10 most common blue dyes showed that the dyes which had very similar chemical structures such as Patent Blue V and Patent Blue VF (which differ only by a single OH group) gave SERRS spectra in which the only indications that the dye structure had been changed were small differences in peak positions or relative intensities of the bands. SERRS studies of 13 gel pen inks were consistent with this observation. In some cases inks from different types of pens could be distinguished even though they were dominated by a single dye such as Victoria Blue B (Zebra Surari) or Victoria Blue BO (Pilot Acroball) because their predominant dye did not appear in other inks. Conversely, identical spectra were also recorded from different types of pens (Pilot G7, Zebra Z-grip) because they all had the same dominant Brilliant Blue G dye. Finally, some of the inks contained mixtures of dyes which could be separated by TLC and removed from the plate before being analysed with the same poly-SERS films. For example, the Pentel EnerGel ink pen was found to give TLC spots corresponding to Erioglaucine and Brilliant Blue G. Overall, this study has shown that the spectral differences between different inks which are based on chemically similar, but nonetheless distinct dyes, are extremely small, so very close matches between SERRS spectra are required for confident identification. Poly-SERS substrates can routinely provide the very stringent reproducibility and sensitivity levels required. This, coupled with the awareness of the reasons underlying the observed differences between similarly coloured inks allows a more confident assessment of the evidential value of inks SERS and should underpin adoption of this approach as a routine method for the forensic examination of inks.