Singh Himanshi, Ray Debes, Kumar Sugam, Takata Shin-Ichi, Aswal Vinod K, Seto Hideki
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.
Homi Bhabha National Institute, Mumbai 400 094, India.
Phys Rev E. 2020 Dec;102(6-1):062601. doi: 10.1103/PhysRevE.102.062601.
The interaction of nanoparticles with surfactants is extensively used in a wide range of applications from enhancing colloidal stability to phase separation processes as well as in the synthesis of noble functional materials. The interaction is highly specific depending on the charged nature of the surfactant. In the case of nonionic surfactants, the micelles adsorb on the surface of nanoparticles. The adsorption of nonionic surfactant C12E10 as a function of surfactant concentration for two different sizes of anionic silica nanoparticles (16 and 27 nm) has been examined using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). SANS measurements have been carried out under different contrast-matched conditions, where nanoparticles, as well as surfactant micelles, have been contrast-matched to the solvent. The adsorption of micelles is determined from the contrast-matched condition of silica nanoparticles with the solvent. SANS data under surfactant contrast-matched condition suggest that there is no modification in the structure and/or interaction of the silica nanoparticles in presence of nonionic micelles. The adsorption of micelles on nanoparticles is found to follow an exponential behavior with respect to the surfactant concentration. These results are consistent with the variation of hydrodynamic size of nanoparticle-surfactant system in DLS. The study on different-sized nanoparticles shows that the lower curvature enhances the packing fraction whereas the loss of surface-to-volume ratio suppresses the fraction of adsorbed micelles with the increase in the nanoparticle size. The adsorption coefficient has higher value for the larger size of the nanoparticles. In the mixed system of two sizes of nanoparticles, no preferential selectivity of micelle adsorption is observed.
纳米颗粒与表面活性剂的相互作用在广泛的应用中被大量使用，从增强胶体稳定性到相分离过程，以及在贵金属功能材料的合成中。这种相互作用具有高度特异性，取决于表面活性剂的带电性质。对于非离子表面活性剂，胶束吸附在纳米颗粒表面。使用动态光散射（DLS）和小角中子散射（SANS）研究了非离子表面活性剂C12E10在两种不同尺寸的阴离子二氧化硅纳米颗粒（16和27纳米）上的吸附与表面活性剂浓度的关系。SANS测量是在不同的对比度匹配条件下进行的，其中纳米颗粒以及表面活性剂胶束都与溶剂进行了对比度匹配。胶束的吸附是根据二氧化硅纳米颗粒与溶剂的对比度匹配条件来确定的。表面活性剂对比度匹配条件下的SANS数据表明，在存在非离子胶束的情况下，二氧化硅纳米颗粒的结构和/或相互作用没有改变。发现胶束在纳米颗粒上的吸附相对于表面活性剂浓度呈指数行为。这些结果与DLS中纳米颗粒-表面活性剂体系的流体动力学尺寸变化一致。对不同尺寸纳米颗粒的研究表明，较低的曲率提高了堆积分数，而表面积与体积比的损失随着纳米颗粒尺寸的增加抑制了吸附胶束的分数。较大尺寸的纳米颗粒的吸附系数值更高。在两种尺寸纳米颗粒的混合体系中，未观察到胶束吸附的优先选择性。
