Huang, Feng-Hsi and Chen, Ching-Chung and Lin, Dar-Jong and Don, Trong-Ming and Cheng, Liao-Ping (2010) Effect of particle size on the photochromic response of PWA/SiO2 nanocomposite. Journal of Nanoparticle Research, 12 (8). pp. 2941-2950.
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A series of photochromic phosphotungstic acid (PWA)/SiO2 composites were synthesized using the sol-gel method. Depending on the feeding schedule of PWA during synthesis, the size of the formed PWA/SiO2 particles varied considerably from as small as 1.2 nm to ca. 10 nm. With decreasing silica particle size, the total contact area/interaction between SiO2 and PWA increases, as revealed by FT-IR and solid-state Si-29-NMR analyses. Particularly, when the size of PWA/SiO2 is similar to 1 nm, crystallization of PWA is inhibited, and PWA presents as amorphous molecular entities distributing uniformly in the SiO2 host, which is in evidence in the XRD spectroscopy and HR-TEM imaging. In contrast, substantial crystallization of PWA takes place when PWA/SiO2 particles are as large as 10 nm, in which case less amount of surface free Si-OH is available for PWA to make bonds with. Photochromism occurs activated by ultraviolet light irradiation. The rate of coloration/bleaching is found to depend strongly on the particle size of PWA/SiO2; specifically, the rate increases twice when the particle size is reduced from 10 nm to 1.2 nm.
|Subjects:||Material Science > Nanostructured materials|
|Deposited On:||26 Dec 2010 12:57|
|Last Modified:||26 Dec 2010 12:57|
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