Steric hindrance in cationic and neutral rhodamine 6 G molecules adsorbed on Au nanoparticles
Steric hindrance in cationic and neutral rhodamine 6 G molecules adsorbed on Au nanoparticles
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DOI：
10.1002/jrs.4204
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发表时间：
2013-03
影响因子：
2.5
通讯作者：
T. Yajima;Yingying Yu;M. Futamata
中科院分区：
文献类型：
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作者：
T. Yajima;Yingying Yu;M. Futamata
利用表面增强拉曼散射（SERS）研究了R6 G分子在Au纳米粒子上的吸附行为。通过观察到R6G+仅以静电力吸附在所制备的金纳米颗粒（AuNPs）上，而R123+与二氢氨基（-NH2）基团在所制备的AuNPs上的静电和化学吸附相反，证明了R6G中的羟乙基氨基（-N（H）Et）基团处的空间位阻。在R6G中的氨基处的大的空间位阻产生对于R6G+的700个分子/AuNP的饱和覆盖率，显著小于对于R123+的1000个分子/AuNP。此外，中性R6 G0在AuNPs上显示出在1200 - 1600 cm-1处的显著增强峰，这在本体溶液中R6 G0的拉曼光谱中以及在AuNPs上R6 G+的SERS中均未观察到。根据分子振动的理论分析，这些谱带归因于外苯环和乙氨基的振动模式，其垂直于氧杂蒽平面。因此，这些频带的拉曼散射增强下的倾斜取向的R6G0分子化学吸附在金纳米颗粒上通过孤对电子在氨基。版权所有© 2013约翰威利父子有限公司.
The adsorption of cationic and neutral R6G molecules on Au nanoparticles was elucidated by surface enhanced Raman scattering (SERS). The steric hindrance at hydroethyl amino (-N(H)Et) groups in R6G was evidenced by the observation that R6G+ adsorb on as-prepared gold nanoparticles (AuNPs) only with electrostatic forces, in contrast to the electrostatic and chemical adsorption of R123+ with dihydro amino (-NH2) groups on as-prepared AuNPs. Large steric hindrance at the amino groups in R6G yielded saturated coverage of 700 molecules/AuNP for R6G+ significantly fewer than 1000 molecules/AuNP for R123+. In addition, neutral R6G0 on AuNPs showed markedly enhanced peaks at 1200–1600 cm−1, which were not observed in Raman spectra of R6G0 in bulk solution, and also in SERS of R6G+ on AuNPs. These bands are attributed to vibrational modes of an outer phenyl ring and ethyl amino groups, which are vertical to a xanthene plane, on the basis of theoretical analysis of molecular vibrations. Thus, Raman scattering of these bands is enhanced under an inclined orientation of R6G0 molecules chemisorbed on AuNPs via lone pair electrons at amino groups. Copyright © 2013 John Wiley & Sons, Ltd.