聚苯乙烯/聚苯胺核殼顆粒還原銀金屬之形貌與成長機制探討

Abstract

本研究以核殼型態聚苯乙烯/聚苯胺乳膠粒子製備薄膜與靜電紡絲，利用聚苯胺的氧化還原性質與導電特性可從硝酸銀水溶液中還原出一維方向延長之奈米銀帶。本論文旨在探討此系統中奈米銀結構的成長機制。 以乳化聚合方式合成的聚苯乙烯顆粒表面包覆上聚苯胺殼層後可形成懸浮在水相中的導電粒子，不須透過有機溶劑的參與即可沉積形成導電薄膜或進行水相靜電紡絲。導電薄膜依酸的摻雜、聚苯胺殼層的包覆程度及乳膠顆粒的堆疊狀況而有不同尺度規模的導電能力。中間鹽式態的聚苯胺可作為還原劑，能從硝酸銀水溶液中將銀離子還原成銀金屬，而在初期成核容易、且電子能夠傳遞補充的情況下，銀金屬能以透過奧斯瓦爾德熟化的方式成長成一維方向延長之銀帶。同條銀帶上的面心立方堆疊方向均相同，且以最密堆疊面{111}面族為成長嗜好面、銀帶沿最密堆疊方向族<110>方向族延長。本研究進一步透過不同的操縱變因，如摻雜酸、硝酸銀共溶劑比例、成核劑有無等，以驗證此成長模型與調控奈米銀金屬形貌。

In this study, polystyrene(PS)/polyaniline(PANI) core/shell latex particles were formed into conducting films and electrospun fibers. The redox and conductive properties of polyaniline enabled it to gain one-dimensional elongating silver bands from silver nitrate aqueous solution by reduction. This thesis aimed to investigate the growth mechanisms of the nano-silver structures in the cases. The polystyrene latexes were first synthesized as the cores, then polyaniline was polymerized onto the latex particles to form core/shell structures. The core/shell latex particles were suspended in water, which made it possible to fabricate cast films and electrospun fibers without organic solvents. The conductance depends on the acid doping level, the degree of coverage, and the assembly of particles, which differs from small to large scales. With the emeraldine salt form polyaniline as the reducing agent, the silver ions in silver nitrate aqueous solution could be reduced to silver (solid). Under the conditions that nucleation and transfer of electrons were facilitated at the beginning of the reactions, the nano-silver could stretch out by ripening with other nuclei. Every site on the same silver band is in the same zone axis and with the same diffraction pattern in the same orientation. The most preferred growth planes are {111} and the preferred growth directions are <110>, which are exactly the closed-packed planes and closed-packed directions of the face-centered cubic (FCC) structure. Also, experiments with independent variables such as kinds of doping acids, ratios of cosolvents for silver nitrate, the addition of the nucleating agent, were carried out to examine the growth mechanism and regulate the morphology of nano-silver structures.