Elucidation of pH impacts on monosubstituted benzene derivatives using normal Raman and surface-enhanced Raman scattering.
Elucidation of pH impacts on monosubstituted benzene derivatives using normal Raman and surface-enhanced Raman scattering.
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DOI：
10.1063/5.0029445
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发表时间：
2020-11
期刊：
影响因子：
--
通讯作者：
Wenjing Xi;A. Haes
中科院分区：
文献类型：
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作者：
Wenjing Xi;A. Haes
拉曼光谱振动频率用于探测溶液中分子周围的局部化学环境，并吸附到金纳米星上。在此，官能团质子化的影响，单取代的苯衍生物与胺，羧酸，或氢氧化物进行了评估。通过评价振动频率的系统变化，结合亲和力和取向的变化是明显的。值得注意的是，这些官能团的给电子能力影响环呼吸模式的振动频率，从而导致改进的光谱解释。此外，金纳米星被用来研究分子质子化的苯甲酸/苯甲酸对金的吸附的影响。使用zeta电位和表面敏感技术，表面增强拉曼散射测量分子质子化的变化。这些方法表明，pH值的变化诱导羧酸盐质子化和电子再分布，削弱分子的亲和力，从而导致分子采取相对于nanostar表面的垂直到平行的取向。官能团的身份影响的环呼吸模式频率的功能的电子捐赠的变化，从官能团的环在溶液中，以及分子的亲和力和方向上的金。这种对振动频率的利用有助于阐明复杂系统中的分子行为。
Raman spectral vibrational frequencies are used to probe the local chemical environment surrounding molecules in solution and adsorbed to gold nanostars. Herein, the impacts of functional group protonation on monosubstituted benzene derivatives with amine, carboxylic acid, or hydroxide are evaluated. Changes in binding affinity and orientation are apparent by evaluating systematic variations in vibrational frequencies. Notably, the electron donating abilities of these functional groups influence the vibrational frequency of the ring breathing mode, thus leading to improved spectral interpretation. Furthermore, gold nanostars are used to investigate the impact of molecular protonation on the adsorption of benzoic acid/benzoate to gold. The changes in molecular protonation are measured using zeta potential and the surface-sensitive technique, surface-enhanced Raman scattering. These methods reveal that pH variations induce carboxylate protonation and electron redistribution that weaken molecular affinity, thereby causing the molecule to adopt a perpendicular to parallel orientation with respect to the nanostar surface. Functional group identity influences the ring breathing mode frequency as a function of changes in electron donation from the functional group to the ring in solution as well as molecular affinity to and orientation on gold. This exploitation of vibrational frequencies facilitates the elucidation of molecule behavior in complex systems.