Trujillo Michael J, Camden Jon P
Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States.
ACS Omega. 2018 Jun 20;3(6):6660-6664. doi: 10.1021/acsomega.8b01147. eCollection 2018 Jun 30.
Surface-enhanced hyper-Raman scattering (SEHRS), the nonlinear analog of surface-enhanced Raman scattering (SERS), provides unique spectral signatures arising from the molecular hyperpolarizability. In this work, we explore the differences between SERS and SEHRS spectra obtained from surface-bound uranyl ion. Exploiting the distinctive SEHRS bands for trace detection of the uranyl ion, we obtain excellent sensitivity (limit of detection = 90 ppb) despite the extreme weakness of the hyper-Raman effect. We observe that binding the uranyl ion to the carboxylate group of 4-mercaptobenzoic acid (4-MBA) leads to significant changes in the SEHRS spectrum, whereas the surface-enhanced Raman scattering (SERS) spectrum of the same complex is little changed. The SERS and SEHRS spectra are also examined as a function of both substituent position, using 2-MBA, 3-MBA, and 4-MBA, and the carbon chain length, using 4-mercaptophenylacetic acid and 4-mercaptophenylpropionic acid. These results illustrate that the unique features of SEHRS can yield more information than SERS in certain cases and represent the first application of SEHRS for trace analysis of nonresonant molecules.
表面增强超拉曼散射（SEHRS）是表面增强拉曼散射（SERS）的非线性类似物，它提供了由分子超极化率产生的独特光谱特征。在这项工作中，我们探究了从表面结合的铀酰离子获得的SERS和SEHRS光谱之间的差异。利用独特的SEHRS谱带对铀酰离子进行痕量检测，尽管超拉曼效应极其微弱，我们仍获得了出色的灵敏度（检测限 = 90 ppb）。我们观察到，将铀酰离子与4-巯基苯甲酸（4-MBA）的羧酸基团结合会导致SEHRS光谱发生显著变化，而同一配合物的表面增强拉曼散射（SERS）光谱变化很小。还使用2-MBA、3-MBA和4-MBA研究了SERS和SEHRS光谱随取代基位置的变化，并使用4-巯基苯乙酸和4-巯基苯丙酸研究了碳链长度对光谱的影响。这些结果表明，在某些情况下，SEHRS的独特特征能比SERS产生更多信息，并且代表了SEHRS在非共振分子痕量分析中的首次应用。
