SERRS and visible extinction spectroscopy of copper chlorophyllin on silver colloids as a function of pH

被引:10
作者
House, Paul G. [2 ]
Schnitzer, Cheryl S. [1 ]
机构
[1] Stonehill Coll, Dept Chem, Easton, PA USA
[2] Univ Wisconsin, Dept Chem, Whitewater, WI 53190 USA
关键词
copper chlorophyllin; SERRS; Raman spectroscopy; visible extinction spectroscopy; pH; titration curve; adsorption; silver colloid; colloidal aggregation;
D O I
10.1016/j.jcis.2007.10.011
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
A study of sodium copper chlorophyllin adsorbed on silver colloids (CuChl/Ag) is conducted using surface-enhanced resonance Raman scattering (SERRS) and visible extinction spectroscopy to examine how the system changes as a function of pH. Initially at basic pH, SERRS signal is not detected even though CuChl is adsorbed onto the silver surface and deprotonated. Upon decreasing the solution pH slightly, colloidal aggregation is induced, evidenced by the broadening of the visible extinction spectra. The larger aggregates possess a surface plasmon that is in resonance with the laser excitation frequency (633-nm) and SERRS signal is detected. As the acid protonates CuChl, the overall negatively-charged surface approaches neutrality which induces more aggregation. Complete protonation of CuChl by pH 4.6 results in colloidal precipitation. However, when aggregation is halted about pH 5, adding NaOH(aq) to the system maintains the extent of aggregation and an intense SERRS signal is detected at basic pH. (c) 2007 Elsevier Inc. All rights reserved.
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页码:145 / 151
页数:7
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