Semi-quantitative determination of cationic surfactants in aqueous solutions using gold nanoparticles as reporter probes |
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Authors: | Chi-Lap Kuong Wei-Yu Chen Yu-Chie Chen |
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Institution: | (1) Department of Applied Chemistry, National Chiao Tung University, Hsinchu, 300, Taiwan;(2) Institute of Molecular Science, National Chiao Tung University, Hsinchu, 300, Taiwan |
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Abstract: | Concentrations of cationic surfactants in aqueous solutions have been estimated on the basis of changes in the color of gold
nanoparticles, used as reporter probes. We have shown that the colors of gold nanoparticles with anionic protective groups
on their surfaces shift from red to indigo/purple and then back to red in a range of cationic surfactant solutions in which
concentrations vary from very low to above the theoretical CMCs. The color changes occur near the theoretical CMCs, presumably
because the presence of surfactant micelles in the solution prevents the gold nanoparticles from aggregating. We have used
gold nanoparticles as reporter probes to determine the concentrations of cationic surfactants in products such as hair conditioners,
which often contain large amounts of alkyltrimethylammonium halides. Although this approach can only provide an estimate,
it can be performed simply by addition of a given amount of gold nanoparticles to a series of diluted solutions, without the
need for instruments or labor-intensive procedures.
Figure Photographs of a series of diluted hair conditioner solutions with added gold nanoparticles
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Keywords: | Gold nanoparticles Cationic surfactants Iron oxide particles Chemical sensor SALDI MS |
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