Fluorescent Nanocomposites For Latent Fingerprint Detection

Latent fingerprint identification, which is one of the most valuable physical evidence, is of great importance in the application of criminal science, accident survey, information identification and safety inspection. However, due to the diversity of its object and the timeliness of its remaining, latent fingerprint cannot always be satisfactory, especially when visualizing and extracting in traditional ways, so it is urgent to develop a new type of latent fingerprint visualize reagent and extract technology with high sensitivity and visualization. Therefore, in the recent years, researchers are trying to use nano-phosphors as the visualize reagent, and pursuing a nano-phosphor based fingerprint visualization and inspection technology, which is cheap, simple, efficient and with low interference and multiple signals.In this thesis, CdTe@SiO2/Ag nanocomposites as antibacterial fluorescent markers for enhanced latent fingerprint detection. Silver power-CdTe@SiO2 nanocomposites as a dual-purpose system for latent fingerprint detection and Fe3O4-CdTe@SiO2 nanocomposites as magnetism fluorescent markers for latent fingerprint detection are all compounded through simple chemistry preparation methods. Besides, the visualization and extraction of these functional nanocomposites used in latent fingerprint are also systematically investigated.The first chapter is introduction section, which mainly talks about the feature of latent fingerprint, the research development of traditional fingerprint visualization and the summary of nanocomposites. Then it introduces the research design and content of the thesis.The second chapter discusses the designed synthesis of CdTe@SiO2/Ag nanocomposites as antibacterial fluorescent markers for enhanced latent fingerprint detection. With the use of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission election microscopy (TEM), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), fluorescence spectra (FL) and antibacterial property tests, the structure and antibacterial and luminescence properties of CdTe@SiO2/Ag nanocomposites as antibacterial fluorescent markers for enhanced latent fingerprint detection is studied. The different visualization and extraction results of latent fingerprint remained in different objects are investigated. The results prove that CdTe@SiO2/Ag nanocomposites as antibacterial fluorescent markers for enhanced latent fingerprint detection have better bacterial resistence property and can visualize perfectly of remained fingerprint on various kinds of objects, therefore, it has certain application prospects in the visualization and extraction of latent fingerprint.The third chapter discusses the designed synthesis of Silver powder-CdTe@SiO2 nanocomposites as a dual-purpose system nanocomposite for latent fingerprint detection. With the use of XRD, SEM, TEM and FL, the structure, fluorescence, and fingerprint visualization of Silver powder-CdTe@SiO2 nanocomposites as a dual-purpose with different ratios of silver powder nanoparticles are carefully studied. The results provethat the additive amounts of silver powder nanoparticles can influence the feature and fluorescence of Silver powder-CdTe@SiO2 nanocomposites for latent fingerprint detection. Compared with traditional commercial visualization and extraction reagents, such material has strong adhesive ability and better visualized and extracted capability. Therefore, it can realize dual function identification via fingerprint fluorescence visualization under UV-light and nano-powder hint under visible light.The fourth chapter discusses the designed synthesis of Fe3O4-CdTe@SiO2 nanocomposites as magnetism fluorescent markers for latent fingerprint detection. With the use of XRD, SEM, TEM and FL, the structure, magnetism and luminescent property of Fe3O4-CdTe@SiO2 nanocomposites is carefully studied, and the visualization and extraction results of remained latent fingerprint on different kinds of objects are studied. The results show that the additive amounts of Fe3O4nanoparticles can affect the feature and luminescent property of Fe3O4-CdTe@SiO2 nanocomposites. Compared with traditional commercial fingerprint visualization and extraction reagents, Fe3O4-CdTe@SiO2 nanocomposites as magnetism fluorescent markers have strong adhesive ability and better visualized and extracted capability, and moreover, it possesses the magnetic separation and recycling functionality, thus having a better prospect for practical applications for latent fingerprint detection.The fifth charpter is the summary and prospect of the thesis.