金奈米棒表面修飾對銀殼成長的影響

改良晶種成長法合成長寬比為5的金奈米棒(50 nm × 10 nm)，利用二次成長法將金離子還原於金奈米棒上製備長寬比為5.7的啞鈴形奈米棒(57 nm × 10 nm)。以左旋半胱胺酸(L-cysteine)分別對金奈米棒與啞鈴形奈米棒進行表面修飾，在不同界面活性劑以及不同反應溫度條件下使用化學還原法將銀離子還原於其表面形成金銀核殼型奈米粒子，藉此比較有無表面修飾與不同反應條件下對銀殼成長的效應。陽離子型界面活性劑中，銀殼可一步成長。在陰離子型界面活性劑中，室溫環境下銀殼為多步成長，高溫環境下銀殼則是一步成長。在室溫及高溫條件中分別添加螯合劑與金屬鹽類可輔助銀殼生長，透過競爭反應去改善銀離子的還原速率。表面修飾L-cysteine的金奈米棒有助於提高在陰離子界面活性劑環境下銀殼生長的均勻度；然而，金奈米棒兩端銀殼生長卻會因此被抑制。

關鍵字

金銀核殼型奈米粒子；半胱胺酸；表面修飾

並列摘要

Gold Nanorods (AuNRs) with aspect ratio 5 (50 nm × 10 nm) are synthesized with an improved seed-mediated growth method, and gold nanodumbbells (AuDBs) with aspect ratio 5.7 (57 nm × 10 nm) are prepared via the second reduction of gold ions on the AuNRs. Further, the surfaces of AuNRs and AuDBs are modified by L-cysteine, and they are subsequently employed in the synthesis of gold-silver core-shell nanoparticles through the reduction of silver ion onto their surfaces. Effect of surface modification with different reaction conditions such as surfactants and temperatures are studied. In the cationic surfactants, silver shells grow on the surfaces of AuNRs and AuDBs in a one‐step process. For the anionic surfactants system, silver shells grow on AuNRs and AuDBs in a multi‐step processes at room temperature. At high temperature (75 oC), chelating agent and metal salts such as NaCl and NaBr as additives can assist the silver shells grow because the reduction rate of silver ions can be modulated via the competitive reaction. Surface modification of AuNRs and AuDBs is contributed to better monodispersity of the silver shells in anionic surfactants system; however, L-cysteine modified AuNRs and AuDBs would inhibit the silver shell grow on the surfaces at the ends of them.