膠體奈米金粒子於矽烷改質矽基板上吸附行為之研究

Adsorption of Gold Nanoparticles on Silanized Silicon Substrates

胡書銘(Shu-Ming Hu)

指導教授 ： 許經夌

中原大學/理學院/物理研究所/碩士(2011年)

https://doi.org/10.6840/cycu201100500

摘要

我們觀察膠體奈米金粒子沉積於表面接有矽烷的矽基板上之行為，探討不同的pH值對奈米金粒子在矽基板上覆蓋率比值的影響。
我們利用浸泡法使奈米金粒子(直徑=18 nm)沉積在APTMS-矽基板上形成次單層(submonolayer)薄膜，當浸泡的時間逐漸增加時，APTMS-矽基板表面所吸附的奈米金粒子也隨之增加，當時間足夠長時，基板上吸附的顆數趨近穩定值時，則稱之為飽和顆數，而時間與吸附顆數曲線會呈現出指數衰減函數(exponential decay function)的關係。
我們藉由添加HCl和NaOH溶液來調整pH值，添加HCl溶液時，pH值隨之降低，矽基板上的飽和顆數逐漸增加，因為氫離子減弱了奈米金粒子表面的電荷，而使粒子間的距離變近，所以飽和顆數逐漸增加；當加入NaOH溶液時，pH值逐漸上升，矽基板上的飽和顆數隨之降低，主要是因為APTMS-矽基板表面需要氫離子作用才能轉變為正電荷藉以吸附表面帶負電荷的奈米金粒子，所以pH值越高，膠體金溶液裡的氫離子越少，則APTMS-矽基板上所吸附的奈米金粒子越少。
我們從SEM圖上的取得奈米金粒子的分佈座標，接著用Radial Distribution Function和Shortest Distance方法估算出此實驗中奈米金粒子上靜電荷的有效斥力距離約為6 ～ 8 nm，我們將奈米金粒子的半徑加上靜電荷的有效斥力距離，估算出有效覆蓋面積比值約0.7，此數值低於ordered close packing (0.9069) 和random close packing (0.82 ± 0.02)，此結果顯示了利用靜電力吸附奈米金粒子於矽基板上的行為是random loose packing。
我們將次單層薄膜浸泡在不同碳數的硫醇中，硫醇跟金有強鍵結力，可以取代奈米金粒子表面上的檸檬酸根。而實驗結果顯示鍵結碳數較多的硫醇金粒子有較低的移動率，主要是因為碳數多的硫醇碳鏈比較長，所以接在奈米金粒子表面上的量會比較少，表面電荷降低的量較少，相反的，碳數較少時，粒子移動率較高，且實驗結果顯示出，當浸泡在六碳單硫醇時，粒子容易形成網路連結導通現象。

關鍵字

吸附 ； 自組成 ； 膠體

並列摘要

We studied the coverages of gold colloidal nanoparticles deposited on organosilanized silicon substrates for different pH values of gold colloids. The gold nanoparticle submonolayer films were formed by deposition of gold nanoparticles (diameter=18 nm) on (3-Aminopropyl)-trimethoxysilan (APTMS) covered substrates. When the deposition time increases, the number of adsorbed gold nanoparticles increases. If the time is long enough, the nanoparticle adsorption becomes saturated. The time-adsorption curve shows exponential decay behavior.
We used HCl and NaOH solution to adjust the pH value of gold colloids. When pH value is small, the saturation number of adsorbed nanoparticles increases. It is because the surface charge of nanoparticles reduced and the distance between nanoparticles becomes shorter, On the other hand, when NaOH solution is added, the pH value increases and the concentration of hydrogen ions reduces. Because APTMS-silicon surface needs hydrogen ions providing positive charges to attract negative charges of gold nanoparticles, the number of nanoparticles on silicon surface decreases.
We got the positions of nanoparticles from SEM pictures, and used Radial Distribution Function and Shortest Distance methods to estimate that the effective repulsive distance of the charged gold nanoparticles is 6～8 nm. By adding the radius of nanoparticles to the effective repulsive distance, we estimate that the effective coverage is about 0.7. The value is lower than that of the ordered close packing (0.9069) and the random close packing (0.82 ± 0.02). The results show that the adsorption of nanoparticles on silicon substrate is random loose packing.
The sub-monolayer films were immersed in thiols which have different carbon number. Because gold and thiol have strongth bonding, thiol can replace the citrate on the surface of gold nanoparticles. The experimental results show that the nanoparticles binding with long carbon chain thiols have lower mobility, because the long carbon chain thiols can replace the less amount of citrate on the surface of nanoparticles. It causes that the surface charge has less change and the nanoparticles have lower mobility.
The experimental results show that for the films which were immersed in six-carbon thiol, the particles easily form a network pattern.

並列關鍵字

colloidal ； self-assembly ； adsorption

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