高產量高長寬比金奈米棒的製備與多分支金奈米粒子的直接合成

High Yield Synthesis of High Aspect Ratio Gold Nanorods and Direct Synthesis of Branched Gold Nanocrystals

吳向陽(Hsiang-Yang Wu)

指導教授 ： 黃暄益

國立清華大學/理學院/化學系/碩士(2006年)

https://doi.org/10.6843/NTHU.2006.00099

摘要

本文發展出一項嶄新的高徑長比金奈米棒合成方法。 藉由改進傳統植晶法的合成方式，在合成過程中加入硝酸配合界面活性劑的作用，促使高長度且高產量高分散性的金奈米棒大量生成。
在傳統合成金奈米棒的實驗中，奈米金三角形片狀物是無法避免的副產物；為了降低金奈米三角片狀物的生成，在合成催化金核的實驗過程中修飾出新的奈米晶核粒子，並成功地取代了傳統的金核保護劑 (檸檬酸鈉)，有效並成功地抑制了片狀物的產生。
利用紫外線光譜儀、掃描式和穿透式電子顯微鏡對於產物做定性分析和測定，結果都顯示出高徑長比與高產量的金奈米棒的合成非常地成功。
本文對於氫氧化鈉和左旋維他性C對於多分支金奈米粒子生成的影響作研究。 具有高表面積型態的多分支金奈米粒子是較為不穩定的活性奈米材料， 在室溫之下約1小時即會轉換成較為等向穩定性的球狀金奈米粒子。
實驗中利用紫外線光譜儀和穿透式電子顯微鏡，對於金奈米粒子的形態轉換在不同的時間下做即時監控與實驗對照，有效地對於多分支金奈米粒子的成長過程變化作定性分析研究。 並成功地在於低溫下阻止多分支奈米粒子的形態轉換，有效控制多分支金奈米粒子的穩定存在，使其多分支型態穩定存在達一個月以上。

關鍵字

金奈米棒 ； 金奈米粒子 ； 植晶 ； 分支

並列摘要

We report a new development for the direct high-yield synthesis of high aspect ratio gold nanorods. By using a modified seed-mediated synthesis approach for the preparation of high aspect ratio gold nanorods with the addition of an appropriate amount of nitric acid during nanorod growth, uniform and monodisperse gold nanorods were synthesized in large quantity.
The formation of triangular nanoplate by-products was substantially reduced by replacing trisodium citrate with CTAB surfactant as the capping agent in the preparation of gold seeds. The nanorods have an average length of 355.3 ± 31.3 nm and an average diameter of 18.7 nm, giving them an average aspect ratio of 19. The ultra-small gold seeds used for nanorod growth are ~1–2 nm in diameter and show a weak absorption band centered at ~480 nm. The nanorods show a transverse surface plasmon resonance (SPR) absorption band at 497 nm and a longitudinal SPR band in the near-infrared (NIR) region.
We report a synthesis of branched gold nanocrystals by the addition of a suitable amount of NaOH to an aqueous solution of cetyltrimethylammonium bromide, HAuCl4, and ascorbic acid. NaOH serves as an effective reducing agent to induce the formation of branched gold nanocrystals. The branched nanocrystals were formed within minutes of reaction and showed monopod, bipod, tripod, and tetrapod structures. The branched nanocrytals quickly transformed into spherical nanoparticles within 1 h of reaction, and the process was essentially complete after 2 days of reaction.
The morphological transformation has been monitored by both UV–vis absorption spectroscopy and electron microscopy. The appearance of two major absorbance bands for the branched gold nanocrystals eventually became only a single band at 529 nm for the spherical nanoparticles. The resulting nanoparticles are single crystalline with diameters of 20–50 nm and without the presence of twinned boundaries. By keeping the freshly prepared branched nanocrystals in a refrigerator at 4 °C, their multipod structure can be preserved for over a month without significant spectral shifts.

並列關鍵字

gold nanorod ； gold nanoparticle ； seeding growth ； brchah

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