以植晶法製備鈀奈米棒和具分支的鈀奈米晶體與可調控之高徑長比金奈米棒的合成

Synthesis of Pd Nanorods and Branched Particles by a Seeding Growth Approach and Seed-mediated Synthesis of Controllable Ultrahigh Aspect Ratio Gold Nanorods

洪曉惠(Hisao-Hui Hung)

指導教授 ： 黃暄益

國立清華大學/理學院/化學系/碩士(2007年)

摘要

本篇論文包含兩個研究主題，第一個部分為利用植晶法合成鈀金屬奈米材料，包含一維結構及具分支的鈀奈米粒子；而第二個研究主題則是於不同濃度之硝酸中合成金奈米棒，並達到調控其徑長比的目的。
在植晶法合成鈀金屬奈米材料的過程中，由於氧氣對於做為晶種的鈀奈米粒子具侵蝕作用，因此晶種的製備需在隔離氧氣的情況下，經由後續的成長程序，可以得到鈀奈米棒，其產率則能藉由硝酸銅溶液的添加而大幅提升。根據文獻研究，我們認為這是因為銅離子於較低電位沈積在鈀晶種上，因而達到幫助鈀奈米棒成長的效果。此外，由於檸檬酸鈉已被證實可以用來阻絕氧氣侵蝕的作用，我們以檸檬酸鈉取代原先的保護劑四級銨鹽來製備鈀的晶種，經由後續植晶的步驟後，這些晶種成長為具有分支的鈀奈米粒子。
本篇論文的另一個研究主題，則是著重於金奈米棒的合成。目前文獻發表的眾多合成方法，顯然較無法對金奈米棒的長度做大幅度的調整，而藉由在不同濃度之硝酸中進行三步驟植晶的合成，金奈米棒的徑長比可以達到一定程度的控制。而硝酸在成長過程中，除了降低界面活性劑頭端的靜電斥力而使微胞拉長外，也成功的減緩反應，因而對成長中的金奈米材料達到較好的控制。

關鍵字

鈀奈米棒 ； 金奈米棒 ； 高徑長比 ； 具分支的鈀奈米晶體 ； 植晶

並列摘要

Synthesis of Pd Nanorods and Branched Particles by a Seeding Growth Approach

In this thesis work, we observed the effects of oxidative etching on the Pd seeds. Two synthetic methods of Pd seed solution were demonstrated to block the oxidative influence: the CTAB-capped seeds were prepared under nitrogen and the TSC-capped seed solution was generated by substituting the capping agent to trisodium citrate (TSC). Both the approaches can successfully extend the lifetime of Pd seeds from initially fifteen minutes to several days.
Via the following seeding growth in the presence of Cu(OAc)2, we obtained Pd nanorods by using the CTAB-capped seeds. From the TEM characterization, we conclude that the uniform Pd nanorods have an average length of 130 nm and exhibit a penta-twinned structure. The introducing of Cu2+ cations has also been found the key factor for increasing the nanorod yield and this could be referred to the underpotential deposition (UPD). In addition, when the TSC-capped seeds were applied to the seeding growth, a rarely seen Pd branched particles with an average size of 30 nm were obtained. The formation of these unusual Pd nanostructures may be attributed to the strong binding of TSC on the surface of the Pd seeds.

Seed-Mediated Synthesis of Controllable Ultrahigh Aspect Ratio Gold Nanorods

The three-step seed-mediated growth method has been widely used for growing gold nanorods with high aspect ratios, however few reports are available for tailoring the nanorod length to micrometer scale. In this study, gold nanorods can be extended to 1 μm in length by growing the seeds in a growth solution containing nitric acid. By increasing the concentrations of nitric acid, gold nanorods with different aspect ratios of 23, 35, 38, 49 can be generated. The addition of nitric acid could apparently retard the reaction, especially in concentrated ones, and possibly allows a better control in early stage of the growth. In the presence of the worm-like micelle of CTAB created by using nitrate anions as counter ions, the gold seeds grow into long nanorods. Another possible factor for the growth of high aspect ratio nanorods may be contributed by the chloride－enhanced oxidizing strength of nitric acid. Because the particles may serve as primary structure for oxidative etching due to the twinned defects, as a result, they may re-dissolve into the solution. That’s why we observed that main byproducts converted from initially spherical particles to gold nanoplates for the nanorods prepared in concentrated nitric acid.

並列關鍵字

Pd nanorods ； gold nanorods ； ultrahigh aspect ratio ； Pd branched ； seeding

參考文獻

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