製備奈米銀之保護劑及操作模式效應

Effects of Protecting Agent and Operation Mode on the Preparation of Silver Nanoparticles

郭昱緯(Yu-Wei Kuo)

指導教授 ： 戴怡德

國立臺灣大學/工學院/化學工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.00388

摘要

奈米銀在導電、光學、熱性質、催化反應等方面都有極佳的效果，而應用的方向則取決於本身的尺寸與表面形態。常見的製備方法主要分為化學法與物理法，合成技術首推化學還原法。化學還原法常在攪拌反應槽中進行，不但耗時且常需要加熱來加速反應，產物也往往面臨粒徑過大或是粒徑分布不均的情形。
近年來本實驗室發展出一結合綠色化學與製程強化(process intensification)之製備奈米銀的綠色製程，即以天然物質之澱粉做為保護劑，葡萄糖為還原劑，並將之與超重力技術結合。然而產率最高僅能達到約70%，且易得大於10nm之粒子。之後又將保護劑改為Polyvinyl pyrrolidone (PVP)則能有效控制銀粒子在10nm以內，顯見保護劑的選擇對奈米銀的性質有重要的影響。該程序採循環式操作，產能較低。
本實驗為提高產能，將硝酸銀濃度提高，改變保護劑，並改採連續式操作。首先以Hydroxypropyl methyl cellulose (HPMC)為保護劑進行循環式操作，發現容易有聚集現象發生，但在調高葡萄糖濃度後不僅聚集消失，銀粒子之體積平均粒徑亦降至10nm以內，且產率最高可達92%。PVP系統在循環式操作時亦能將銀粒子粒徑控制在10nm以內，且在降低保護劑用量後產率最高可達92%。然而以starch作為保護劑時，產率最高僅達73.3%且無法讓粒徑降至10nm內，因此選擇以PVP和HPMC做為保護劑來進行連續式操作之產能放大實驗。
在PVP系統下每日最高產能可達約35kg，粒徑亦能控制在10nm左右，然而缺點為產率僅有45~50%，原料損失較大；HPMC系統下之每日最高產能可達34kg，產率亦有近90%的水準，但所得銀粒子尺寸較大，約在15~30nm。與循環式操作提高硝酸銀濃度的結果做比較，即使硝酸銀濃度提升到0.05M日產能仍不及200g，與連續式操作之產能有明顯的差距。綜觀研究結果，超重力裝置不僅設備小不佔空間，同時亦能獲得高產能，且PVP和HPMC皆不危害人體和環境，符合綠色化學製程。

關鍵字

超重力技術 ； 奈米銀 ； 旋轉盤反應器 ； 綠色製程 ； 連續式操作 ； 保護劑

並列摘要

Ultrafine silver powders have been attracted much attention in recent years because of their excellent electrical, thermal, biological, catalytic and optical properties. The size and morphology of silver particles are important in their applications. Although nanoparticles can be prepared either by physical or chemical method, the wet chemical method is probably more popular. The disadvantage of the conventional chemical method is that the reaction usually takes hours under a high temperature. In addition, the size distribution of particles are difficult to control.
A new green chemical process for preparing silver nanoparticles, using starch as the protecting agent and glucose as the reduction agent, have been developed form in our laboratory recently, by carrying out the reducing reaction in a spinning disk reactor, i.e., the process combined green chemistry and process intensification. However, the application was restricted by low yield and large size of silver product. Using PVP as the protecting agent, it was possible to produce the silver particles less than 10nm. Obviously, the choice of protecting agent was important to influence the property of silver nanoparticles. This process was operated in a recycle mode with a low production rate.
In this study, we select a different protecting agent, increased the concentration of silver nitrate, and adopted the continuous operation for increasing production rate. First of all, a third protecting agent, HPMC, was tested and compared with others in the recycle operation. The particle size of silver product could be controlled within 10nm and had the highest yield of 92% by using PVP or HPMC as the protecting agent. However, the highest yield was 73.3% and the particle size of silver product was larger than 10nm, using starch as the protecting agent. Thus PVP and HPMC was chosen as the protecting agents in the continuous operation for increasing production rate.
In the PVP system, the highest production rate of one day was about 35kg and the particle size was still smaller than 10nm, but the yield was only between 45 to 50%, thus caused a large waste of materials. In the HPMC system, the highest production rate of one day was about 34kg and the yield was about 90%, but the particle size was larger in the range of 15 to 30nm. As to the recycle operation, the production rate was lower than 200g/day, even though the concentration of silver nitrate was increased to 0.05M. Viewing in this light, a high-gravity process that combined economic benefit with environmental benignancy was successfully developed using a small spinning-disk reactor with less space required.

並列關鍵字

high-gravity (Higee) technique ； nano-silver ； spinning disk reactor (SDR) ； green process ； continuous operation ； protecting agent

參考文獻

王耀萱，「利用超重力系統開發奈米銀的綠色製程」，碩士學位論文，台大化工所 (2006)

李佳鴻，「以超重力沉澱法進行SMZ藥品微粒化之研究」，碩士學位論文，台大化工所 (2007)

陳昱劭，「旋轉填充床中黏度對質傳影響之研究」，博士學位論文，台大化工所 (2004)

Alt V., Bechert T., Steinrucke P., Wagener M., Seidel P., Dingeldein E., Domann E., Schnettler R., “An in vitro assessment of the antibacterial properties and cytotoxicity of nanoparticulate silver bone cement”, Biomaterials, 25, 4383-4391 (2004)

Bhargava S. K., Booth J. M., Agrawal S, “Gold nanoparticle formation during bromoaurate reduction by amino acids”, Langmuir, 21, 5949-5956 (2005)