奈米銀線的成長及成核

Nucleation and Growth of Silver Nanowires

林忠緯(Chung-Wei Lin)

指導教授 ： 蘇安仲

國立清華大學/工學院/化學工程學系/碩士(2017年)

摘要

本論文重點是透過小角度/廣角度Ｘ光散射儀、掃描式電子顯微鏡及紫外-可見光光譜儀研究銀奈米結構在多元醇反應中的形態變化。在這實驗中，我們控制反應物硝酸銀的加入速率來實驗反應的影響，而加入硝酸銀溶液速率有分為兩種：一種是將全部的硝酸銀溶液一次加入反應器之中反應，另一種是將硝酸銀溶液以滴定方式每分鐘約3.5 毫升滴入反應器之中進行反應。奈米銀線確切出現時間可以藉由紫外-可見光吸收光譜、掃描式電子顯微鏡觀察和產物溶液顏色來分辨。對於一次加入程序之實驗，銀奈米顆粒在反應初期就已經出現；在實驗進行到5 分鐘時，銀奈米棒開始出現在產物溶液中，並在實驗反應到8 分鐘時成為主要產物。在這個階段銀奈米棒呈現不穩定狀態並被稱為「雛形奈米棒」，而這雛形奈米棒當受到電子顯微鏡之電子束照射時會重組且露出奈米顆粒，同時銀面心立方的訊號才開始出現在廣角度散射儀之中，這表示銀奈米棒可能是藉由小的銀奈米顆粒黏合而成。在這階段之後可以見到大量奈米銀線在反應之中。而在滴定條件下進行反應，反應的趨勢和一次加入的結果是類似的，差別就在反應時間延遲了幾分鐘，這表示著銀奈米顆粒需要達到適合的濃度才會形成奈米銀線。綜合所有觀察結果，我們推斷需要足夠的奈米顆粒來黏合形成雛形奈米棒，接下來可能藉由奈米銀棒與PVP 高分子鏈相互作用沿著軸向生長形成奈米銀線。

關鍵字

奈米線 ； X光小角度散射 ； 銀

並列摘要

This study is focused on the morphology development of silver nanostructures in the polyol
process by means of simultaneous small/wide-angle X-ray scattering (SAXS/WAXS), scanning
electron microscopy (SEM), and ultraviolet-visible spectroscopy (UV-Vis). In this study, we carried
out the experiment with different conditions by controlling the flow rate of AgNO3 solution as
reactant. One is the once-adding and the other is the dropwise-adding whose flow rate is ca. 3.5
mL/min into the reactor. The exact time of silver nanowires appearance is confidently determined
from UV-Vis absorption, SEM observations and color evolution. For the once-adding condition, silver
nanoparticles appear at the beginning of reaction; after t = 5 min, nanorods begin to show up in the
reaction and become the dominating species after t > 8 min. Silver nanorods are unstable during this
period and called as embryonic nanorods, simultaneously Ag face-centered cubic (FCC) signals
appear in the WAXS profiles. Meanwhile, embryonic nanorod, which is unstable and fragile, would
be damaged by electron beam of SEM. Through irradiation of electron beam on embryonic nanorod
makes the nanograins emerge from the embryonic nanorod. This implies that silver nanorods are
formed by coalescence of silver nanograins. After that, we can see a great amount of silver nanowires
in the reaction. For the dropwise-adding condition, the reaction trend is similar to the once-adding
and but with a few minutes’ delay. It suggests that silver nanoparticles need to reach an adequate
concentration to form nanowires. From all observations, we deduce that sufficient nanoparticles
coalesce to form embryonic nanorods, followed with growing in axial direction by probably
interacting with PVP chains to form silver nanowires.

並列關鍵字

nanowire ； small angle X-ray scattering ； silver

參考文獻

3. Yang, L.; Yu, X.; Hu, W.; Wu, X.; Zhao, Y.; Yang, D., Appl. Mater. Interfaces. 2015, 7, 4135.

2012, 24, 3326.

6. Sun, Y.; Xia, Y., Adv. Matter. 2002, 14, 833.

S.J.L.; Xia, Y., ACS Nano.2016, 10, 7892.

12. Coskun, S.; Aksoy, B.; Unalan, H.E., Cryst. Growth. Des. 2011, 11, 4963.