Photoluminescence Properties of ZnS : Mn2+ Nanoparticles in Aqueous Solutions and Sol-Gel Glasses
Yoshikuni UCHIDA, Tomo KOIZUMI and Kazunori MATSUI*
Department of Industrial Chemistry, College of Engineering, Kanto Gakuin University; Mutsuura-cho 4834, Kanazawa-ku, Yokohama-shi 236-8501 Japan
ZnS : Mn2+ nanoparticles were synthesized from aqueous solutions of Zn(NO3)2, Mn(NO3)2 and Na2S under pH 3.0, 6.8 and examined by using absorption and luminescence spectra. The absorption spectra changed as functions of pH and time (Fig. 1). Orange luminescence due to Mn2+ substituting for Zn2+ in the ZnS lattice was strongly observed in addition to both weak ultraviolet luminescence due to Mn2+ attaching to the surface of ZnS nanoparticles and blue luminescence due to vacancies in the lattice, which are shown in Fig. 2. These luminescence spectra changed by pH and time. These properties were most possibly related to the stability of the nanoparticles. Based on these findings, sol-gel glasses doped with ZnS : Mn2+ nanoparticles were synthesized from the above starting materials and tetramethoxysilane. The absorption spectra were shown in Fig. 3. Orange luminescence was considerably observed in the sol-gel glass as shown in Fig. 4. The particle diameter in sol-gel glasses was estimated to be 3.1-3.8 nm from the excitation spectra shown in Fig. 4. These results suggest that sol-gel glasses doped with ZnS : Mn2+ nanoparticles can be prepared by the method employed in this experiment, although further studies are required to obtain more luminous sol-gel silica.
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