微束X射线荧光光谱分析技术在一种黑色纸张物证检验中的应用研究

Study on Application of Micro-XRF Mapping Analysis in Identification of a New Kind of Black Paper Evidence

对7种真假纸币样本和2003年～2008年的32宗诈骗案件中共计225件被染黑的真假纸币物证，采用微束x射线荧光光谱仪（micro-XRF）分析其二维元素分布。结果表明：纸币元素分布特征都具有特定性，相同面额相同年版的纸币元素分布特征相同，相同面额不同年版的纸币元素分布特征有差异；真假纸币元素分布特征存在显著差异；被染黑的纸币元素分布特征与原纸币相同；因而可根据被染黑真假纸币的元素分布特征，鉴定其真伪并判断纸币种类。微束XRF分析在实际案件中黑色纸张物证的检验准确率为100％。因此，微束XRF技术能有效检验被染料染黑的真假纸币，具有灵敏度高，分析过程中不破坏样品，结果准确的特点，在该类物证的检验中具有较高的应用价值。

Dyed-in-black banknote or fake banknote, also called ＂black banknote＂ in casework, is critical physical evidence for a new type of fraud crime taking place in recent years. The paper for the first time studied the application of micro-XRF（X-ray microfluorescence spectrometer） in identification of the kind of evidence. Seven types of true and false banknotes together with 225 pieces of the kind of evidence in 32 fraud cases received for identification by the authors＇ laboratory from 2003 to 2008 were investigated on their 2D elemental distributions by micro-XRF mapping analysis. The result of the analysis of the seven types of samples indicated： firstly, there existed speciality on elemental distribution for each kind of banknote, i.e. the banknotes with uniform both denominations and versions had the same elemental distribution characteristics while the banknotes with uniform denominations and different versions differed each other at this aspect; secondly, true and fake banknotes showed much difference on elemental distribution characteristics; thirdly, elemental distribu- tions of the dyed banknotes were the same as those of their originals; therefore, ＂black banknote＂ evidence could be identified according to their elemental distributions obtained through micro-XRF mapping analysis. Furthermore, the result of the analysis of the 225 pieces of the kind of evidence in the real cases by micro-XRF suggested that the accuracy rate was 100% . In conclusion, micro-XRF with the advantages of no destruction, high sensitivity and high accuracy is a useful tool and of great application value in identification of the kind of evidence of dyed-in-black banknote or fake banknote.