化學與電化學法製備銀奈米粒子及其催化應用

Chemical and Electrochemical Preparation of Silver Nanoparticles and their Catalytic Applications

何昆政(Kun-Cheng Ho)

指導教授 ： 陳生明

國立臺北科技大學/工程學院/化學工程研究所/碩士(2009年)

摘要

首先是將硝酸銀 ( AgNO3 ) 加入含有 3,4-二氧乙烯塞吩 ( EDOT ) 和聚對苯乙烯磺酸鈉 ( PSS ) 的酸性水溶液中來合成高穩定性 Ag-PEDOT 複合奈米粒子。反應物中 EDOT 當作還原劑及 PSS 為掺雜物及穩定劑。用紫外光-可見光光譜 ( UV-vis ) 來記錄不同反應時間下，銀奈米粒子生成及 EDOT 氧化，顯示波長在 380 及 700 nm 有吸收峰，分別是銀奈米粒子及聚 3,4-二氧乙烯塞吩 ( PEDOT ) 所產生的。並用傅立葉紅外線光譜 ( FT-IR ) 、穿透式電子顯微鏡 ( TEM ) 及 X光繞射分析儀 ( XRD ) 研究其特性，而 TEM 顯示高穩定性銀奈米粒子的表面形貌、粒徑大小及分佈情形，銀粒子約為 6 nm 。在應用方面，把此複合奈米粒子應用於催化對-硝基苯酚還原為對-胺基苯酚。另外，為了比較其穩定性，我們還製備不含 PSS的酸性水溶液中所合成出的 Ag-PEDOT 複合奈米粒子來做比較，並用 UV-vis 記錄不同反應時間的光譜，顯示銀奈米粒子吸收峰為 400 nm ，但隨著反應時間的增加，其吸收峰發生紅移，表示此銀奈米粒子是不穩定的。
由於上述合成須額外加入 PSS 當作粒子穩定劑，因此我們進一步選用反應物本身扮演還原劑及穩定劑的角色，接著在酸性水溶液中使用 5-胺基-2-萘磺酸 ( ANS ) 來製備 Ag-PANS 複合奈米粒子。在 PANS 結構中的磺酸基視為自身摻雜物，並用 UV-vis 、 FT-IR 及 AFM 研究其性質，顯示銀奈米粒子吸收峰為 450 nm ，粒徑大小約為 10 nm ，並用循環伏安法 ( CV ) 証實是由 Ag-PANS 複合奈米粒子所組成。
最後用電化學法來製備銀奈米粒子並比較與化學法的差異及其複合薄膜電極的應用。先用電化學沉積來製備 PEDOTSDS 及銀奈米粒子 ( PEDOTSDS-Agnano ) 修飾電極，上述十二烷基硫酸鈉 ( SDS ) 為一乳化劑， UV-vis 光譜顯示在 375 nm 處有一吸收峰，証實銀奈米粒子生成。並用 AFM 研究其電極表面型態、薄膜厚度及粗糙度。進一步用 PEDOTSDS-Agnano 當作模板來固定電催化物質麥爾多拉藍 ( MDB ) ，以 PEDOTSDS-Agnano-MDB 來表示此複合薄膜電極。由 MDB 的電化學可逆性及覆蓋率來決定最適化銀奈米粒子沉積時間為 750 秒，接著研究 PEDOTSDS-Agnano-MDB 修飾電極電化學特性，包括對菸鹼醯胺腺嘌呤二核苷酸 ( NADH ) 電催化，可有效降低約 650 mV 過電壓，並用計時安培法求出 2 ~ 60 μM 為偵測線性區域、偵測極限為 2 μM 及靈敏度為 0.02 μA / μM ，並有效降低尿酸 ( UA ) 、多巴胺 ( DA ) 及過氧化氫 ( H2O2 ) 干擾物的訊號。

關鍵字

高穩定性 Ag-PEDOT複合奈米粒子 ； 酸性水溶液 ； 還原對-硝基苯酚 ； Ag-PANS複合奈米粒子 ； 粒子穩定劑 ； 循環伏安法 ； 銀奈米粒子 ； 菸鹼醯胺腺嘌呤二核酸

並列摘要

Herein, we have reported preparation of highly stable Agnano-PEDOT nanocomposite by reaction in acidic condition using 3,4-ethylenedioxythiophene ( EDOT ) as a reductant and polystyrene sulfonate ( PSS ) as a dopant for PEDOT and particle stabilizer. Highly stable Ag nanoparticles have been obtained by reduction of AgNO3 using EDOT in the presence of PSS in acidic aqueous medium and show its absorption band at 380 nm. The formation of silver nanoparticles ( AgNPs ) with concomitant EDOT oxidation is followed by UV-vis spectroscopy at various time intervals. Highly stable Agnano-PEDOT nanocomposite shows absorption band at 380 and above 700 nm corresponding to absorption band of AgNPs and oxidized PEDOT, respectively. Highly stable Agnano-PEDOT nanocomposite was characterized by using IR spectroscopy, Transmission Electron microscopy ( TEM ) , and X-ray Diffraction ( XRD ) . The surface morphology, size and distribution of particle have been analyzed using TEM. It revealed that AgNPs are distributed uniformly around polymer with an average size of 6 nm. In addition, highly stable Agnano-PEDOT nanocomposite have employed for the catalytic reduction of 4-nitrophenol. For comparing stability, we have also prepared AgNPs in absence of PSS using EDOT as reductant in acidic condition and followed UV-vis spectroscopy at various time intervals. It shows absorption band at 400 nm and various time measurement of UV-vis spectroscopy results revealed that AgNPs prepared in absence of PSS is not stable.
Herein, we have reported preparation of poly ( amino naphthalene sulfonic acid ) , PANS- silver nanoparticle nanocomposite, Agnano-PANS nanocomposite in acidic aqueous condition using monomer, amino naphthalene sulfonic acid ( ANS ) as a reductant and a particle stabilizer. Reduction of silver ions and polymerization of ANS occurred simultaneously in the absence of a commonly used reducing agent and initiator. Sulfonate group present in the PANS polymer acts as self dopant for polymer and a stabilizing agent. The produced Agnano-PANS nanocomposite was characterized by using UV–vis spectroscopy and Fourier transform infrared spectroscopy. AgNPs were shown its absorption band at 450 nm. AFM image revealed that AgNPs were formed along with the PANS with an average particle diameter 10 nm. The presence of Agnano-PANS nanocomposite was analyzed by using cyclic voltammetry.
Silver nanoparticles incorporated PEDOTSDS modified electrode was prepared by electrochemical deposition method. Hereafter, the above modified electrode denoted as PEDOTSDS-Agnano electrode. The formation of silver nanoparticles was confirmed by UV-vis spectroscopy and its shows SPR peak at around 375 nm. The PEDOTSDS- Agnano electrode surface morphology, film thickness, and surface roughness was analyzed by using Atomic Force microscopy ( AFM ) . The PEDOTSDS-Agnano electrode was utilized as an platform to immobilize electrochemically active mediator, Meldola Blue ( MDB ) , denoted as PEDOTSDS-Agnano-MDB electrode. The optimization of silver nanoparticles was fixed by using the electrochemical reversibility and surface coverage of MDB on PEDOTSDS-Agnano electrode and it revealed that optimum silver deposition time was 750s to obtain reversible peak of MDB. The PEDOTSDS-Agnano-MDB electrode electrochemical properties was characterized by using cyclic voltammetry ( CV ) . The CV revealed that PEDOTSDS-Agnano-MDB electrode was has surface confined process. The PEDOTSDS-Agnano-MDB electrode was tested for electrocatalytic application and it exhibited catalytic activity towards oxidation of dihydronicotinamide adenine dinucleotide ( NADH ) with an activation overpotential, which was around ca 650mV lower than bare electrode ( 600 mV ) . PEDOTSDS-Agnano-MDB electrode amperometric response was tested for NADH. The electrode exhibited linear range from 2 to 60 μM, detection limit 2 μM and sensitivity 0.02 μA / μM for NADH. The PEDOTSDS-Agnano-MDB electrode exhibited diminished response for its interference uric acid ( UA ) , dopamine ( DA ) and hydrogen peroxide ( H2O2 ) .

並列關鍵字

Highly stable Agnano-PEDOT nanocomposite ； acidic aqueous medium ； reduction of 4-nitrophenol ； one-pot synthesis ； PANS-AgNPs nanocomposite ； particle stabilizer ； cyclic voltammetry ； dihydronicotinamide adenine dinucleotide

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