通过电导滴定法测量十二烷基硫酸钠在功能化石墨烯上的吸附。

Adsorption of sodium dodecyl sulfate on functionalized graphene measured by conductometric titration.

机构信息

Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA.

出版信息

J Phys Chem B. 2013 Jul 3;117(26):7950-8. doi: 10.1021/jp403876t. Epub 2013 Jun 24.

Abstract

We report on the adsorption of sodium dodecyl sulfate (SDS) onto functionalized graphene sheets (FGSs) in an aqueous system, measured at broad SDS and FGS concentration ranges by conductometric surfactant titration. At dilute SDS concentrations (<12 μM in bulk solution), there is evidence of a counterion exchange between hydronium ions (from the dissociation of acidic chemical functionalities on FGS) and sodium ions coadsorbing with dodecyl sulfate monomers onto FGSs. We find that, for FGS with a carbon-to-oxygen ratio of ~18, monolayer adsorption of SDS on FGS reaches full surface coverage by ~12 μM SDS. Additionally, the critical surface aggregation concentration (csac) for surface micelle formation on FGS is measured to be ~1.5 mM SDS. The transition from monolayer adsorption to surface micelle formation appears to occur at a similar SDS concentration on FGSs as on graphite, suggesting there is little difference in the surfactant adsorption behavior on both materials. We estimate that the FGS surface area available for SDS adsorption is ~600 m(2)/g, which is significantly less than expected for FGSs in suspension and indicates the presence of regions on FGS on which SDS adsorption does not occur.

摘要

我们报告了在水溶液中十二烷基硫酸钠（SDS）在功能化石墨烯片（FGS）上的吸附，通过电导法表面活性剂滴定在宽 SDS 和 FGS 浓度范围内进行了测量。在 SDS 浓度较低的情况下（在本体溶液中<12 μM），存在质子（来自 FGS 上酸性化学官能团的解离）与与十二烷基硫酸盐单体共吸附到 FGS 上的钠离子之间的抗衡离子交换的证据。我们发现，对于碳氧比约为 18 的 FGS，通过~~12 μM SDS 达到 FGS 上 SDS 的单层吸附的完全表面覆盖。此外，测量到 FGS 上表面胶束形成的临界表面聚集浓度（csac）为~~1.5 mM SDS。从单层吸附到表面胶束形成的转变似乎在 FGS 上与在石墨上的表面胶束形成的 SDS 浓度相似，这表明两种材料上的表面活性剂吸附行为几乎没有差异。我们估计可用于 SDS 吸附的 FGS 表面积约为 600 m(2)/g，这显著小于悬浮 FGS 中的预期值，并表明 FGS 上存在 SDS 吸附不发生的区域。