ENSEMBLE MEASUREMENT THAT DECOUPLES THE BINDING AFFINITIES OF IONIC COMPONENTS OF CETRIMONIUM HALIDES
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This thesis discusses the binding behaviors of the ionic components of cetrimonium halides, a common family of capping agents, on the surface of pseudospherical gold nanoparticles in aqueous environment. Specifically, the reaction kinetics of the adsorption reaction were studied and the behaviors of cetrimonium halide compounds, as well as their cation and anion components, are decoupled and compared. The binding behaviors of capping agents on gold surfaces were revealed with the assistance of the probe reaction of resazurin reduction. The adsorption reaction kinetics of cetrimonium chloride (CTAC) was proven to be similar to that of isolated CTA+. Meanwhile, the binding affinity of chloride anion (Cl-) towards gold surface is much weaker compared to both CTAC and CTA+. These results indicate the dominant effect of CTA+ in the adsorption behavior of CTAC on amorphous gold surface, and the weak interaction as well as the possible selectivity of Cl- adsorption on gold facets. These results, although specific to CTAC, is also a part of a general observation over the binding behaviors of the entire family of cetrimonium halides. Thus, future research has also been planned to study other species in the family of cetrimonium halides, such as cetrimonium bromide (CTAB), and to make effective comparisons between it and Br-. Such comparisons are worthwhile to discuss, along with the already studied case of CTAC and Cl-, because halide ion is a component of the dissolved cetrimonium halides, but also by itself a family of capping agent, with different affinity towards gold surface and different shape directing preferences compared to cetrimonium halides, according to previous research. With experiments that extend to more halide and cetrimonium halide species, we might be able to make a general conclusion and find the reason for the differences between their properties as capping agents for gold nanoparticles.