以電化學法控制銅和銅銀複合奈米結構之形貌、大小及其在生化感測之應用

Abstract

This study focuses on the shape and size control of Cu nanoparticles by tailoring the surface morphologies of TiN thin film electrode. These Cu nanoparticles were further used to fabricate Cu/Ag composite nanostructures. TiN thin films exhibiting superior electrical and thermal conductivity, high chemical stability and hardness are of technologically important materials. The surface morphologies of TiN thin films can be varied by changing the deposition parameters during sputtering. The novelty of this research is using the surface morphologies of TiN thin films to control shape and size of Cu nanoparticles. This model system can be extended to other conductivity nitride thin films. In contrast, conventional shape and size control of metallic nanoparticles, such as variation of electrolytes and power mode was also used. The sputtering deposition parameters including the power and working pressure were varied to prepare TiN films. In this study, we obtained granular TiN films at a higher sputtering power and a lower working pressure while pyramidal TiN films at a lower sputtering power and a higher working pressure. Under the same electrodeposition conditions, smaller irregular Cu nanoparticles formed on a pyramidal TiN film and larger, octahedral Cu nanoparticles grew on a granular TiN film. In comparision, the species and concentrations of the surfactant, salts as the stabilizer, and the power mode were also varied in synthesizing Cu nanoparticles. The significant effect of the concentration of surfactant was confirmed. It contributed to the growth of the smaller, irregular Cu nanoparticles when the concentration of surfactant was higher than their critical micelle concentration (CMC). As the concentration of surfactant was lower than the CMC, cubic Cu nanoparticles were formed. Another objective for this study is to investigate the electrocatalytic abilities of Cu nanoparticles with various shapes and sizes for nonenzymatic glucose sensing. This has not been reported before. The sensitivity of the smaller, irregular Cu nanoparticles in the detection of glucose was better than that of the larger, octahedral Cu nanoparticles because of the former’s greater increase in the Cu2+-to-Cu0 ratio. We also used various sizes of Cu nanoparticles as starting materials to prepare the Cu/Ag composite nanostructures via galvanic displacement reaction. Cu/Ag core-shell structures were formed by using smaller Cu nanoparticles as the starting materials, while Cu nanoparticles/Ag nanobelts structres were made by using larger Cu nanoparticles as the starting materials. Both structures revealed the surface-enhanced Raman scattering phenomenon with Rhodamine 6G (R6G) as the probe molecule. Tailoring simply the surface morphologies of TiN thin films can control shape and size of Cu nanoparticles during electrodeposition. Different Cu/Ag composite nanostructures can be formed with various sizes of Cu nanoparticles by galvanic displacement reactions. Various shapes and sizes of Cu nanoparticles and those of Cu/Ag composite nanostructues revealed pretty good biosensing ability. This technique may be extended to other nitride thin film systems, which has great industrial applications.

本研究主要是在電沉積法中，以導電氮化鈦(TiN)薄膜為電極，利用TiN的表面形貌不同，進行銅奈米粒子的形貌與顆粒大小的控制；再利用此不同形貌與大小的銅奈米粒子進行銅銀複合材料之合成，並將兩者應用於生化感測的範疇上。TiN薄膜是相當重要的工業材料，具有優異的導電及導熱性、化學穩定性佳及硬度高等性質，且可藉由濺鍍鍍著參數的改變而調控TiN薄膜的表面結構。以TiN薄膜的形貌進行金屬奈米粒子形貌與大小的控制，是一新穎的控制方法，我們希望以此控制方式為探討模組並冀望能應用至其他導電氮化物基材，甚至拓展至不同的材質。同時，我們亦採用傳統上控制金屬奈米粒子形貌與顆粒大小的方式，藉由改變電解液的條件以及改變電壓供應方式，以作對照。 實驗上，我們利用改變濺鍍鍍著功率以及工作壓力進行TiN薄膜的鍍著，結果發現，在高鍍著功率、低工作壓力的條件下，會鍍著出顆粒狀、表面平坦的TiN薄膜；而低鍍著功率及高工作壓力的條件下，則會形成角錐狀、表面粗糙的TiN薄膜。將兩種不同形貌的TiN薄膜當成工作電極，在相同電沉積條件下，角錐狀、較粗糙的TiN薄膜，可沉積出小顆粒、不規則形狀的銅奈米粒子；而顆粒狀、較平坦的TiN薄膜，則會沉積出顆粒較大且形貌為八面體結構的銅奈米粒子。 在對照組的實驗中，我們改變界面活性劑的種類、界面活性劑的濃度、採用鹽類當成穩定劑以及改變電壓供應方式等條件。結果發現，在本系統中界面活性劑的濃度對於銅奈米粒子形貌與顆粒大小的影響較大，當界面活性劑濃度高於臨界微胞濃度(CMC)時，會產生小顆粒、不規則形狀的銅奈米粒子；但當濃度低於CMC值時，則會產生立方體的銅奈米粒子。至於界面活性劑的種類以及以鹽類當成穩定劑，其影響則不顯著。 同時，我們並研究銅奈米粒子的形貌與大小對葡萄糖分子的感測效果，這在文獻上也未有過報導。我們研究發現，小顆粒且不規則形貌的銅奈米粒子具有較高的感測效果，其靈敏度與穩定度均比大顆粒、八面體形貌的銅奈米粒子還好。這是由於小顆粒且不規則形貌的銅奈米粒子具有較高的感測效果，這是因為小顆粒且不規則形貌的銅奈米粒子在葡萄糖感測過程中，可以產生較多的Cu2+，且同時亦發現對葡萄糖的感測靈敏度與反應中產生的Cu2+/Cu0比值有關，比值越高其靈敏度相對也越高。 我們亦以不同顆粒大小的銅奈米粒子，利用伽凡尼置換反應製備銅銀複合材料。結果發現，以小顆粒的銅奈米粒子為反應物，隨著反應時間的增加會形成銅核/銀殼的複合結構；而大顆粒的銅奈米粒子，則會形成銅奈米粒子/銀奈米帶的複合結構。而我們發現，此兩種不同形貌的銅銀複合結構，包括銅核/銀殼的複合結構以及銅奈米粒子/銀奈米帶的複合結構，對於玫瑰紅6G (Rhodamine 6G, R6G)染料分子都具有表面增強拉曼訊號的現象。 本研究利用導電氮化物薄膜為電極，在電化學法中，單純地以電極的表面形貌便可控制銅奈米粒子的形貌與大小；同時我們亦證明不同大小的銅奈米粒子可藉由伽凡尼置換反應產生不同結構的銅銀複合材料，而這些不同形貌的銅奈米粒子以及銅銀複合結構，均證明能應用在生化感測上。在未來，我們希望能將此方法拓展至其他導電性金屬氮化物薄膜，亦即此法極具產業應用潛力。