Athukorale Sumudu, Leng Xue, Xu Joanna Xiuzhu, Perera Y Randika, Fitzkee Nicholas C, Zhang Dongmao
Department of Chemistry, Mississippi State University, Starkville, MS, United States.
Department of Chemistry, Chengdu University of Technology, Chengdu, China.
Front Chem. 2019 Feb 14;7:27. doi: 10.3389/fchem.2019.00027. eCollection 2019.
A series of recent works have demonstrated the spontaneous Ag adsorption onto gold surfaces. However, a mechanistic understanding of the Ag interactions with gold has been controversial. Reported herein is a systematic study of the Ag binding to AuNPs using several and measurement techniques. The time-resolved UV-vis measurements of the AuNP surface plasmonic resonance revealed that the silver adsorption proceeds through two parallel pseudo-first order processes with a time constant of 16(±2) and 1,000(±35) s, respectively. About 95% of the Ag adsorption proceeds through the fast adsorption process. The zeta potential data indicated that this fast Ag adsorption is driven primarily by the long-range electrostatic forces that lead to AuNP charge neutralization, while the time-dependent pH data shows that the slow Ag binding process involves proton-releasing reactions that must be driven by near-range interactions. These experimental data, together with the XPS measurement indicates that adsorbed silver remains cationic, but not as a charged-neutral silver atom proposed by the anti-galvanic reaction mechanism. The surface-enhanced Raman activities of the Ag-stained AuNPs are slightly higher than that for AuNPs, but significantly lower than that for the silver nanoparticles (AgNPs). The SERS feature of the ligands on the Ag-stained AuNPs can differ from that on both AuNPs and AgNPs. Besides the new insights to formation mechanism, properties, and applications of the Ag-stained AuNPs, the experimental methodology presented in this work can also be important for studying nanoparticle interfacial interactions.
最近的一系列研究表明，银会自发吸附在金表面。然而，对于银与金相互作用的机理理解一直存在争议。本文报道了一项使用多种测量技术对银与金纳米颗粒结合的系统研究。对金纳米颗粒表面等离子体共振的时间分辨紫外可见测量表明，银的吸附通过两个平行的准一级过程进行，时间常数分别为16（±2）秒和1000（±35）秒。约95%的银吸附通过快速吸附过程进行。ζ电位数据表明，这种快速的银吸附主要由导致金纳米颗粒电荷中和的长程静电力驱动，而随时间变化的pH数据表明，缓慢的银结合过程涉及质子释放反应，这一定是由近程相互作用驱动的。这些实验数据，连同X射线光电子能谱测量结果表明，吸附的银保持阳离子状态，但并非如反电偶反应机制所提出的带电中性银原子。银染色的金纳米颗粒的表面增强拉曼活性略高于金纳米颗粒，但远低于银纳米颗粒（AgNPs）。银染色的金纳米颗粒上配体的表面增强拉曼光谱特征可能与金纳米颗粒和银纳米颗粒上的不同。除了对银染色的金纳米颗粒的形成机制、性质和应用有新的见解外，本文提出的实验方法对于研究纳米颗粒界面相互作用也可能很重要。
