Enhanced Development of Footprints Using YVO4∶Eu Luminescent Nanomaterials
DING Han1, WANG Meng2*
1. Criminal Justice School, Zhongnan University of Economics and Law, Wuhan 430073, China
2. College of Forensic Sciences, Criminal Investigation Police University of China, Shenyang 110035, China
Abstract：Footprint development has long been considered as one of the essential technologies in forensic sciences, which is an important prerequisite for footprint analysis and footprint identification. On the basis of our previous research achievements in nanomaterial based development of latent fingerprints, in this paper, we put forward an enhanced development of footprints using YVO4∶Eu luminescent nanomaterials (NMs) in order to improve the results of footprint development greatly. Firstly, YVO4∶Eu luminescent NMs were synthesized via a typical hydrothermal method, using rare earth nitrate and sodium orthovanadate as the raw materials, and trisodium citrate as the modifier. Then, the micromorphology, crystal structure, ultraviolet absorption property, luminescent performance and surface functional groups of synthesized NMs were characterized by transmission electron microscopy, powder Xray diffractometer, ultravioletvisible spectrophotometer, fluorescence spectrophotometer and Fourier transform infrared spectrometer, respectively. The YVO4∶Eu luminescent NMs were quasispherical in shape with an average diameter of 39.2 nm and had a tetragonal crystal structure. The maximum ultraviolet absorption wavelength of the NMs was 257 nm. Under a 254 nm ultraviolet excitation, they could give strong red emissions at a wavelength of 614 nm. The NMs were modified with citric acid molecules on the surface. Finally, the YVO4∶Eu luminescent NMs were used for enhanced development of barefoot and footwear impressions. The mechanisms for two types of footprint development were also discussed in detail. The barefoot development results showed that the morphological features were sharp, the friction ridge was coherent, and the detailed features were clear, and the folds, exfoliation and coherent substance were obvious. The footwear development results showed that the footwear pattern features were intact and distinct. The developed footprint features could fully meet the main requirements in footprint examination and identification. In addition, the promotion effects of luminescent property, particle size and micromorphology of synthesized NMs on the contrast, sensitivity and selectivity in footprint development were also discussed. Our enhanced development of footprints based on YVO4∶Eu luminescent NMs has a series of advantages including strong contrast, high sensitivity and good selectivity, which will not only expand the applications of rare earth luminescent NMs but also provide innovative ideas for traditional footprint developing methods.
Key words：Rare Earth; Luminescence; Nanomaterials; Footprint; Development
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