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Toward Monitoring Electrochemical Reactions with Dual-Wavelength SERS: Characterization of Rhodamine 6G (R6G) Neutral Radical Species and Covalent Tethering of R6G to Silver Nanoparticles
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2016-10-24 00:00:00 , DOI: 10.1021/acs.jpcc.6b09022
Stephanie Zaleski , M. Fernanda Cardinal , Dhabih V. Chulhai 1 , Andrew J. Wilson 2 , Katherine A. Willets 2 , Lasse Jensen 1 , Richard P. Van Duyne
Affiliation  

The combination of electrochemistry (EC) and single molecule surface-enhanced Raman spectroscopy (SMSERS) has recently proven to be a sensitive method to investigate electron transfer (ET) reactions at the single molecule level. SMSERS can both detect single redox-active molecules and potentially monitor both the oxidized (O) and reduced (R) forms of a one-electron ET reaction in a single experiment. Herein, we report progress toward complete monitoring of single ET reactions with EC-SMSERS. We first obtained the solution phase resonance Raman (RR) spectrum of the Rhodamine 6G (R6G) neutral radical (R) with thin-layer resonance Raman spectroelectrochemistry (EC-RRS). The experimental spectrum was then correlated with the spectrum calculated by density functional theory (DFT). We then describe our approach to address the problem of adsorbate (R) loss caused either by desorption or reaction of the neutral radical with trace water or oxygen during the EC-SMSERS experiment. We have investigated a covalent cross-linking reaction which tethers R6G to SERS-active substrates (Ag nanoparticles). Covalently tethered R6G is subsequently characterized by surface cyclic voltammetry (CV) and SERS. Lastly, an optimized cross-linking reaction is devised which enabled the first direct detection of the one-electron reduced form of R6G with SERS. Our findings demonstrate that SERS can simultaneously monitor both O and R of a one-electron ET reaction.

中文翻译:

借助双波长SERS监测电化学反应:若丹明6G(R6G)中性自由基物种的表征以及R6G与银纳米粒子的共价束缚

电化学(EC)和单分子表面增强拉曼光谱(SMSERS)的组合最近被证明是一种研究单分子水平电子转移(ET)反应的灵敏方法。SMSERS既可以检测单个氧化还原活性分子,又可以在单个实验中监测单电子ET反应的氧化(O)和还原(R)形式。在此,我们报告了使用EC-SMSERS全面监测单个ET反应的进展。我们首先通过薄层共振拉曼光谱电化学(EC-RRS)获得了若丹明6G(R6G)中性自由基(R)的溶液相共振拉曼光谱(RR)。然后将实验光谱与通过密度泛函理论(DFT)计算的光谱关联起来。然后,我们描述了解决EC-SMSERS实验过程中中性自由基与微量水或氧气的解吸或反应引起的吸附物(R)损失问题的方法。我们已经研究了将R6G连接到SERS活性底物(Ag纳米粒子)的共价交联反应。随后通过表面循环伏安法(CV)和SERS对共价连接的R6G进行表征。最后,设计了一种优化的交联反应,该反应能够使用SERS首次直接检测R6G的单电子还原形式。我们的发现表明,SERS可以同时监测单电子ET反应的O和R。我们已经研究了将R6G连接到SERS活性底物(Ag纳米粒子)的共价交联反应。随后通过表面循环伏安法(CV)和SERS对共价连接的R6G进行表征。最后,设计了一种优化的交联反应,该反应能够使用SERS首次直接检测R6G的单电子还原形式。我们的发现表明,SERS可以同时监测单电子ET反应的O和R。我们已经研究了将R6G连接到SERS活性底物(Ag纳米粒子)的共价交联反应。随后通过表面循环伏安法(CV)和SERS对共价连接的R6G进行表征。最后,设计了一种优化的交联反应,该反应能够使用SERS首次直接检测R6G的单电子还原形式。我们的发现表明,SERS可以同时监测单电子ET反应的O和R。
更新日期:2016-10-24
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