Adsorption of dodecyltrimethylammonium bromide and sodium bromide on gold studied by liquid chromatography and flow adsorption microcalorimetry.
Adsorption of dodecyltrimethylammonium bromide and sodium bromide on gold studied by liquid chromatography and flow adsorption microcalorimetry.
复制标题
液相色谱和流动吸附微量热法研究了十二烷基三甲基溴化铵和溴化钠在金上的吸附。
作者：
Z. Kiraly;G. Findenegg;Á. Mastalir
在这里，我们报道了溴-在金表面吸附的一个新方面。用连续流动前沿分析、固/液色谱和流动吸附微量热法研究了水溶液中十二烷基三甲基溴化铵(C12TABr)在大孔金颗粒上的吸附。同时测定了吸附的物质平衡和热焓平衡以及溶液pH的变化。最初，Br-不可逆地结合到高亲和力的表面位置，通过从水相中吸附H+来平衡。表面物种的形成伴随着C12TAOH的形成，这反过来又导致本体溶液中pH的显著增加。净过程为强放热过程(-280kJ.mol(-1))，表明发生了化学吸附。在BR-的特定吸附之后，C12TABr的可逆吸附产生了以头到面排列的牢固结合的单分子膜(-53kJ.mol(-1))。在相对较窄的表面覆盖范围内，各种复合结构可在顶层发展，最终转变为全圆柱形的表面集合体。表面聚集是可逆的，其热变为-11kJ.mol(-1)。通过测量NaBr在微粒上的初始吸附，证实了BR-与金表面特异结合的重要性。初始吸附是不可逆的，其热变约为-240kJ.mol(-1)。这一过程包括在金/水界面形成AuBr-/H+双电层，同时由于大量的OH-在体液相中的释放，溶液的pH急剧升高。
Here, we report on a new aspect of the adsorption of Br- on the surface of gold. The adsorption of dodecyltrimethylammonium bromide (C12TABr) from aqueous solutions onto macroporous gold particles was studied by continuous flow frontal analysis solid/liquid chromatography and flow adsorption microcalorimetry. The material balance and enthalpy balance of adsorption and the change in the solution pH were measured simultaneously. Initially, Br- is irreversibly bound to high-affinity surface sites counterbalanced by the adsorption of H+ from the aqueous phase. The surface speciation is accompanied by the formation of C12TAOH, which in turn results in a significant pH increase in the bulk solution. The net process was found to be strongly exothermic (-280 kJ.mol(-1)), which is indicative of the occurrence of chemisorption. The specific adsorption of Br- is followed by the reversible adsorption of C12TABr to produce a firmly bound monolayer in a head-to-surface arrangement (-53 kJ.mol(-1)). In a relatively narrow range of the surface coverage, various composite structures may develop on the top layer and eventually transform to full-cylindrical surface aggregates. The surface aggregation was found to be reversible, with an enthalpy change of -11 kJ.mol(-1). The importance of the specific binding of Br- to the surface of gold was confirmed by measurement of the initial adsorption of NaBr on the microparticles. The initial adsorption was found to be irreversible, with an enthalpy change of approximately -240 kJ.mol(-1). This process involved the formation of an AuBr-/H+ electric double layer at the gold/water interface, accompanied by a dramatic increase in the solution pH due to the release of a copious amount of OH- in the bulk liquid phase.