| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 94 === In this century, nano-size materials have been attracted by attentions in many sciences and technologies due to their special chemical and physical properties, such as, specific surface area and quantum effect, which are very important for advanced function of information and biological technology in the future.
In this thesis, silver nitrate is used as precursor; ethylene glycol is both employed as reduction agent and solvent; and poly vinylpyrrolidone (PVP) is used as capping agent, for ultraviolet (UV, wavelengths of 250-450nm) irradiation assisted synthesizing the silver nano-particles in the batch and recycle processes, respectively. Furthermore, the effects of the flow rate, molar ratio of silver nitrate to PVP, irradiation time (or recycle time), irradiation dose, and temperature in reaction on the size and the yield of as-synthesized silver nano-particles are studied in this work. As shown in the results, the significant conclusions are summarized as two respects below：
(1) In this study, the silver nano-particles have been successfully prepared in the sizes ranging from 10 to 40nm. It is worth mentioned that, for example, as the silver nitrate is 0.05M in solution; the molar ration of silver nitrate to PVP is 2, the dose of ultraviolet irradiation is 11mW/cm², the yield of as-synthesized silver nano-particles is increased with increasing time and over 50% in the cyclic process, which is much better than that in the batch process, as illustrated in UV-vis spectrum and ICP-AES. In addition, as measured from TEM, AFM and FESEM, the size distribution and stability of silver nano-particles in solution fabricated by UV assisted synthesis in the cyclic process are more narrow, small size and excellent than that by convectional heating method and UV assisted synthesis in the batch process; while, as analyzed by XRD, the crystal phase of silver nano-particle is all the same for the convectional heating method and UV assisted synthesis in the cyclic and batch processes.
(2) Through UV-vis, ICP-AES and TEM analyses, the process parameters are systemically studied for the synthesis of silver nano-particles by the cyclic photolysis for the fixed time. Some important results are listed as follows：
(a) The size of as-synthesized silver particles is decreased from 19nm to 16nm, which yield is increased from 9% to 14%, when the flow rate is increased from 22.5ml/min to 73.8ml/min.
(b) As the reaction temperature is increased from 30℃ to 42℃, the size of as-synthesized silver particle is increased from 16nm to 21nm, which yield is increased from 14% to 28% and implies that the yield of as-synthesized Ag nano-particles is significantly dominated by the temperature in the photolysis process.
(c) As the molar ratio of silver nitrate to PVP is increased from 1 to 4, the particle size of as-synthesized silver is increased from 8nm to 29nm, which expresses that the molar ratio of silver nitrate to PVP is a key factor to control the size of as-synthesized particles.
(d) As the dose of ultraviolet irradiation is increased from 11mW/cm² to 72mW/cm², the particle size of as-synthesized silver is not only enlarged from 16nm to 24nm, but also the yield of as-synthesized silver is increased from 14% to 22%.
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