Understanding the Role of Poly(vinylpyrrolidone) in Stabilizing and Capping Colloidal Silver Nanocrystals
Understanding the Role of Poly(vinylpyrrolidone) in Stabilizing and Capping Colloidal Silver Nanocrystals
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了解聚（乙烯基吡咯烷酮）在稳定和封端胶体银纳米晶体中的作用
DOI：
10.1021/acsnano.1c01668
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发表时间：
2021
期刊：
影响因子：
17.1
通讯作者：
Qin, D.
中科院分区：
文献类型：
--
作者：
Yang, T.-H.;Ahn, J.;Shi, S.;Qin, D.
锚定在金属纳米晶体表面的配体在控制其胶体合成方面发挥着重要作用，具有广泛的应用，但在分子水平上研究配体-表面和配体-溶剂相互作用仍然是一个艰巨的挑战。在这里，我们报告的使用表面增强拉曼散射（Sers）提取的结构信息的结合聚（乙烯吡咯烷酮）（PVP）银纳米立方体以及其构象变化响应于溶剂质量。当PVP链通过其一些羰基结合到Ag纳米立方体的表面时，相邻结合位点之间的片段作为环被排出到溶剂中。因此，在Sers光谱中分辨的羰基峰（νC O）包括来自锚定到表面的那些和驻留在环上的那些的贡献，其频率分别位于νC O（Ag）和νC O（free）。虽然由于羰基与Ag表面之间的配位，νC O（Ag）保持在固定的频率，但νC O（游离）的光谱位置取决于溶剂。随着PVP与溶剂间氢键强度的增加，vC O（free）的峰位向低频方向移动。当以交替的方式暴露于不良溶剂和良好溶剂时，PVP环在塌陷状态和延伸状态之间经历构象变化，从而改变游离羰基与Ag表面之间的分离，从而改变VCMO峰的强度。
The ligands anchored to the surface of metal nanocrystals play an important role in controlling their colloidal synthesis for a broad spectrum of applications, but it remains a daunting challenge to investigate the ligand–surface and ligand–solvent interactions at the molecular level. Here, we report the use of surface-enhanced Raman scattering (SERS) to extract structural information about the binding of poly(vinylpyrrolidone) (PVP) to Ag nanocubes as well as its conformational changes in response to solvent quality. When a PVP chain binds to the surface of a Ag nanocube through some of its carbonyl groups, the segments between adjacent binding sites are expelled into the solvent as loops. As a result, the carbonyl peak (νC═O) resolved in the SERS spectrum includes the contributions from those anchored to the surface and those residing on the loops, with their frequencies located at νC═O(Ag)and νC═O(free), respectively. While νC═O(Ag)remains at a fixed frequency due to the coordination between the carbonyl groups with Ag surface, the spectral position of νC═O(free)is dependent on the solvent. As the strength of hydrogen bonding between PVP and solvent increases, the peak position of νC═O(free)shifts toward lower frequencies. When exposed to bad and good solvents in an alternating manner, the PVP loops undergo conformational changes between collapsed and extended states, altering the separation between the free carbonyl groups and the Ag surface and thereby the intensity of the νC═Opeak.