在酸性及鹼性下製備高產率且可調控徑長比的金奈米棒和針對超長金奈米棒的改善合成方法

High-Yield Synthesis of Tunable Aspect Ratio Gold Nanorods in Basic and Acidic Solutions and An Improved Strategy for The Synthesis of Ultralong Gold Nanorods

魏文卿(Wen-Tsing Wei)

指導教授 ： 黃暄益

國立清華大學/理學院/化學系/碩士(2010年)

https://doi.org/10.6843/NTHU.2010.00199

摘要

In this study, we have used a simple seed-mediated synthesis method for the preparation of gold nanorods with average lengths from 412 to 234 nm by tuning the pH of the growth solution from 3.00 to 9.09. The gold nanorods have high aspect ratios of 13.2–20.8. Because of their long lengths, they nicely settled to the bottom of the conical flask, and can easily be separated from the suspended faceted particles. As the pH increased, the length of nanorods became shorter and the yield was raised from 85% at pH 3 to 98% at pH 9.09. TEM and UV−vis absorption characterization of the different products synthesized have been performed. TEM images showed that the gold nanorods possess a penta-twinned structure. The UV–vis absorption band at around 800–900 nm is attributed to gold nanoplates, and we observed that the percentage of nanoplates also decreases as the pH increases by comparing relative strength of the absorption band of nanoplates to that of the transverse SPR band of nanorods. As the amount of sodium hydroxide is increased, gold source changes from AuBr4－ to Au(OH)4－, as confirmed by UV–vis spectra. We try to elongate the lengths of gold nanorods to a limit by raising the amount of nitric acid used. However, when the pH of the growth solution is very low, the product usually accompanies a lot of nanoplates. We have developed a modified method to solve this problem and fabricate gold nanorods at low pH with high yield and few nanoplates. We decreased the amount of CTAB and tetrachloroauric acid in the low pH growth solution to form nanorods with longer lengths. Gold nanorods can increase their lengths from 458 to 952 nm.

關鍵字

金奈米棒 ； 酸鹼值

並列摘要

本篇論文藉由改變金奈米棒成長溶液之酸鹼值從3.00到9.09，並利用三步驟植晶法合成長度為412到234 nm的金奈米棒。這些長金奈米棒會在反應瓶中形成沉澱，故可直接將奈米棒和奈米粒子作簡單地分離，進而達到純化的效果。隨著成長溶液的酸鹼值持續增加，金奈米棒的長度會變得越來越短，而金奈米棒的產率也會隨著酸鹼值的提高從85%增加到98%。本篇論文利用穿透式電子顯微鏡及分光光譜儀來鑑定我們所合成出的金奈米棒，從穿透式電子顯微鏡的分析中我們得知在鹼性下合成出來的金奈米棒亦具有five-fold twinned的結構。在紫外–可見光吸收圖譜中，金奈米片狀的吸收大概在800到900 nm，藉由比較片狀吸收和金奈米棒短軸吸收的相對強度，發現隨著酸鹼值的提升其吸收有著下降的趨勢，這也符合我們在掃描式電子顯微鏡中觀察到的結果。當成長溶液中氫氧根離子的增加，金的起始物會從AuBr4－變成Au(OH)4－，這也可從紫外–可見光吸收圖譜中得到驗證。在較低的酸鹼值下合成金奈米棒，產物往往會伴隨許多的奈米片狀，而我們也提出了一個在低酸鹼值下合成金奈米棒的改良方法。藉由降低溴化十六烷基三甲基銨鹽及四氯金酸的濃度，我們可以得到高產率及片狀較少的金奈米棒，我們甚至可以將奈米棒的長度從458增長到952 nm。

並列關鍵字

gold nanorods ； pH

參考文獻

(19) Wang, C.; Wang, T.; Ma, Z.; Su, Z. Nanotechnology

(24) Chang, S. S.; Shih, C. W.; Chen, C. D.; Lai, W. C.;

(13) Chang, S. S.; Shih, C. W.; Chen, C. D.; Lai, W. C.;

(10) Sudeep, P. K.; Joseph, S. T. S.; Thomas, K. G. J. Am.

(24) Park, W. M.; Huh, Y. S.; Hong, W. H. Current Applied