| Summary: | 碩士 === 國立高雄科技大學 === 電子工程系 === 107 === The identification of latent fingerprints has been widely used in the field of forensics, this is because that fingerprints of each person and each finger are unique and do not change with age. However, fingerprints are not easy to be detected if they are not stained with colored substances such as blood or pigments. In order to identify these potential fingerprints, the most extensive and simple method is the powder dusting method. Consider the characteristics of phosphor sources. Powders been used traditionally have the disadvantages of low contrast, low sensitivity, and easy interference by the background, as a result, the detected latent fingerprints is ambiguous. Accordingly, to achieve good identification of latent fingerprints phosphors should have the characteristics of high luminance intensity along with small particle size.
Four subjects were studied in this theme:
(1) NaAl11O17:Mn2+ phosphor powder was synthesized by solid-state reaction method, and the effect of activator concentration, sintering temperature on the luminescent properties of phosphor was investigated. (2) Sr2MgSi2O7:Eu2+ phosphor was synthesized by co-precipitation method. The effects of activator concentration, sintering temperature, and sintering time on the luminescent properties of phosphor were investigated. (3) Analysis of luminescence properties of NaAl11O17:Mn2+ and Sr2MgSi2O7:Eu2+ phosphors at different ambient temperatures. (4) Application of NaAl11O17: Mn2+ and Sr2MgSi2O7:Eu2+ phosphors for fingerprint identification.
Furthermore, luminescence properties of NaAl11O17:Mn2+ and Sr2MgSi2O7:Eu2+ phosphor were measured and compared. The potential application of phosphors in latent fingerprint detection was investigated as well. As compared with the NaAl11O17:Mn2+ phosphor, the Sr2MgSi2O7:Eu2+ showed a higher luminescence intensity and is more suitable for latent fingerprint identification. Additionally, both kinds of synthesized phosphors exhibited good thermal stability. This indicates that the as-prepared phosphors are suitable for light-emitting diode illumination, as They do not cause a sharp decrease in luminescence intensity when the temperature is increased.
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