- 學位論文
電場協助膠體奈米金粒子吸附於基板行為之研究
Electric field assisted adsorption of gold nanoparticles on silanized silicon substrates
摘要
我們利用電場協助膠體奈米金粒子吸附於表面接有矽烷的矽基板上，研究不同電場強度下對奈米金粒子在基板上覆蓋率比值的影響。 我們利用浸泡法使奈米金粒子(直徑約20 nm)沉積在 APTMS-矽基板上形成次單層薄膜，當浸泡的時間逐漸增加時，APTMS-矽基板表面所沉積的奈米金粒子也隨之增加，當時間足夠長時，基板上沉積的顆數趨近於穩定值，稱之為飽和顆數，而時間與奈米金粒子的覆蓋率比值呈現出指數衰減關係。 APTMS-矽基板沉積奈米金粒子飽和顆數有限，為了增加其奈米金粒子的飽和顆數，我們利用Dielectric Barrier Electrophoretic Deposition (DBEPD) 方法，以電場協助奈米金粒子沉積，隨著電場增加，矽基板上的飽和顆數也隨之增加，因為奈米金粒子表面被檸檬酸根所包覆住，而檸檬酸根帶負電荷，所以金粒子整體電量是負電的，當膠體金粒子在一電場下，金粒子將往正電極方向移動，高電場抵抗金粒子之間的排斥力，導致金粒子間的距離縮短，而增加基板上奈米金粒子的飽和顆數。 我們從SEM圖上取得奈米金粒子的分佈座標與單位面積內覆蓋的面積，覆蓋率可從19%增加至33%，接著用Radial Distribution Function和Shortest Distance方法估算實驗中不同電場下奈米金粒子之排斥距離。 我們再將次單層薄膜浸泡至不同碳數的硫醇中，金和硫醇有很強的鍵結力，可以取代奈米金粒子表面的檸檬酸根。鍵結碳數較少的硫醇時，金粒子具有較高的移動率，原因是因為碳數少的硫醇碳鏈較短，接在金粒子表面的量較多，表面電荷降低的比較多，故排斥力變小，容易移動，相反的，浸泡碳數較多硫醇時，金粒子的移動率較低，實驗結果顯示出，當浸泡在六碳單硫醇時，金粒子容易形成網路連結的現象。
關鍵字
膠體金粒子並列摘要
We used electric field to assist adsorption of gold nanoparticles on organosilanized silicon substrates and studied the coverage of gold nanoparticles for different electric field intensities. The gold nanoparticle submonolayer films were formed by deposition of gold nanoparticles (diameter =18) 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 an exponential decay behavior. To increase the saturated number of adsorbed gold nanoparticles, we used the method of Dielectric Barrier Electrophoretic Deposition (DBEPD) for assisted deposition of gold nanoparticles. When the electric field intensity increases, the coverage of gold nanoparticles on silicon substrates increased. Because the citrate bonding around the surface of gold nanoparticle caused nanoparticle to become negative charged, the nanoparticles were attracted by the positive electrode and transported to silicon substrates. High intensity of electric field resisted the electrostatic repulsion force between gold nanoparticles, leading to that nanoparticles become closed. Therefore the number of adsorbed gold nanoparticles on substrates increased. We obtained the positions of nanoparticles from SEM images and realized that the coverage increased from 19% to 33%, and used the Radial Distribution Function and the Shortest Distance methods to estimate the repulsive distance of nanoparticles. 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 short carbon chain thiols have higher mobility, because the short carbon chain thiols can replace the more amount of citrate on the surface of nanoparticles. It causes that the surface charges has more decrease and the nanoparticles have higher mobility. The experimental results show that for the films which were immersed in six-carbon thiol, the gold nanoparticles easily formed a network pattern.