奈米銀/奈米黏土複合膜之製備及銀之形態控制

Abstract

本研究設計一新型奈米複合材料膜－奈米銀/奈米黏土複合膜，使用澆鑄成膜的方式將奈米矽片銀水溶液製備成膜，並進一步能有效操控膜表面奈米銀之密度、大小和形態。奈米矽片銀水溶液是使用奈米矽片作為分散劑及酒精作為還原劑，利用原位進行氧化還原反應將銀離子還原成金屬銀粒子而得到奈米矽片銀之奈米複合材料。藉由操控奈米矽片自組裝之特性，可以澆鑄成膜之簡易方式，製備出帶有奈米銀粒子之矽土複合膜，並且可進一步以控制銀/奈米黏土之相對濃度、退火時間及溫度等條件控制複合膜材表面銀形成多種形態。在控制退火過程中，奈米銀進行了階段性的形態變化，由球狀奈米粒子(直徑約50奈米以下)轉變為奈米方狀粒子(邊長約100奈米)、奈米棒狀粒子(長約1.5微米、直徑300奈米)最後形成奈米銀線(長約10微米)。本研究以SEM隨時間追蹤，觀察到在奈米銀/奈米黏土複合膜中之銀粒子向膜表面移動並合併成較大尺寸之奈米銀結構之機制，且藉由EDS和XRD進一步驗證此銀之動力學現象和元素成份及晶體結構。

Silver nanoparticles (AgNPs) in silicate clay matrix films were fabricated from solution casting method. The Ag/clay dispersion was first prepared from in situ reduction of silver nitrate in the presence of silicate clay platelets and ethanol as the reducing agent. The Ag/clay film was then prepared by controlling the self assembly of Ag/clay nanohybrid units by casting process. Hierarchical morphologies of silver on clay films have been observed under the conditions of annealing up to 200 °C. Hierarchical transformations from silver nanoparticles (diameter ~ 50 nm) to cubes (length ~100 nm) to rods (length ~ 1.6 μm and width ~300 nm) and lengthy wires (length ~10μm) were obtained by simply adjusting the silver to clay ratio and annealing conditions. The originally homogeneous AgNPs distribution in the clay matrix underwent the transformation of AgNPs in moving to the film surface and coalescing to larger sizes. The kinetic mobility of AgNPs to surface and the characterization of Ag composition were confirmed through energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD).