Telluride Cadmium Quantum Dots Powder Preparation And Evidence Detection Applications

Born in the 1980s, Nano science and technology has achieved a breakthrough, especially in semiconductor nanocrystals. Semiconductor nanocrystals, also called quantum dots(QDs). Because of its unique structure, it shows exceptional physical and chemical properties and excellent optical properties. Compared with traditional organic dyes, quantum dots has so many advantages such as high quantum yield, broad excitation spectra, narrow emission spectra, strong resistance to photobleaching capacity, good stability and biological compatibility and so on. Therefore, more and more scientists from various countries are interested in this field.Two parts are included in this thesis, the first part is review, including concept, basic characters, structure and luminescence mechanism, synthesis and application of quantum dots. The second part is the research report, in this part, we mainly introduced synthesis of quantum dots by glutathione (GSH) and thiol chitosan as stabilizer respectively. Besides, we applied quantuam dots solution and powder in latent fingerprint derection on different objects. At the same time, we discussed the mechanism between quantum dots and latent fingerprint. Main content of research report is as follows:1.Application of GSH-capped CdS QDs solution in latent fingerprints detectionGlutathione (GSH) capped CdS QDs was prepared in aqueous solution, the synthesized CdS QDs characterized by spectrofluorometry, ultraviolet-visible spectrometry and transmission electron microscopy respectively. The results showed that the synthesized quantum dots held excellent optical properties, good distribution and considerable stabilities, we also discussed the light-emitting of quantum dots is influenced by reaction time. Application of GSH-CdS QDs solution on the glass with a-cyanoacrylate fumed potential Fingerprints obtained good results. We also discussed the possible mechanism between quantum and fingerprints.2.Preparation of GSH-capped CdTe QDs powder and application in latent FingerprintsThe changes emission color of GSH-capped CdTe QDs is not obvious, however, GSH-capped CdTe QDs experienced from green-yellow-orange-red-deep changes with the increasing time and for complex object on the background of latent fingerprints appear. Therefore, GSH-capped CdTe QDs powder was prepared by centrifugation and dryness. Then we can get different colors of quantum dots powder. Application of QDs powder for latent fingerprints detection on glass, aluminum, paper money and paper, which fumed by a-cyanoacrylate or not, revealing less background and better contrast.3.Application of CTS-TGA-capped CdTe QDs powder in latent Fingerprints detectionWater-soluble low molecular weight chitosan can be obtained by hydrolyzing chitosan, which molecular weight is 100,000. Thioglycolic acid modified low molecular weight chitosan as stabilizer for CdTe QDs synthesis, Fluorescence emission spectra show that the maximum emission wavelength is 546 nm,peak shape is symmetrical.CdTe QDs powder with thioglycolic acid modified chitosan as stabilizer can be obtaind by centrifugation and dryness. Application of it for latent fingerprints detection on glass, aluminum, copper and paper fumed by a-cyanoacrylate or not, the results indicated that it produced significantly less background and better contrast successfully.