Extremely Slow Diffusion of Gold Nanoparticles under Confinement in Mesoporous Silica
Extremely Slow Diffusion of Gold Nanoparticles under Confinement in Mesoporous Silica
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DOI：
10.1021/acs.jpcc.2c00090
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发表时间：
2022-02-24
影响因子：
3.7
通讯作者：
Leheny, Robert L.
中科院分区：
文献类型：
--
作者：
Mhanna, Ramona;Giroux, Michael;Leheny, Robert L.
我们报告了一个X射线光子相关光谱（XPCS）研究的流动性的胶体金纳米粒子的直径约为4 nm的甘油下限制在SBA-15介孔二氧化硅的通道内的孔径约为6和12 nm。XPCS的相关函数的结果从一个有效的外差信号，由于从纳米粒子和介孔二氧化硅的相干散射的混合。在波矢量的范围内，因此探测的长度尺度，纳米粒子的动力学很好地描述了一维扩散。纳米颗粒的扩散率随着温度的变化的方式预期的基础上的温度依赖性的粘度的甘油;然而，扩散系数的大小是几个数量级小于散装甘油中的纳米颗粒。我们认为，可能有助于这种减少扩散性的机制，包括增强流体动力学阻力约束下，纳米颗粒吸附到孔壁的影响，并减缓结构动力学在甘油由于纳米尺度的限制和存在的纳米颗粒的组合。
We report an X-ray photon correlation spectroscopy (XPCS) study of the mobility of colloidal gold nanoparticles with a diameter of approximately 4 nm in glycerol under confinement within the channels of SBA-15 mesoporous silica with pore diameters of approximately 6 and 12 nm. The XPCS correlation functions result from an effective heterodyne signal due to the mixing of the coherent scattering from the nanoparticles and the mesoporous silica. Over the range of wave vectors and hence length scales probed, the nanoparticle dynamics are well described by one-dimensional diffusion. The nanoparticle diffusivity varies with temperature in a manner expected based on the temperature-dependent viscosity of glycerol; however, the magnitudes of the diffusion coefficients are several orders of magnitude smaller than those of the nanoparticles in bulk glycerol. We consider mechanisms that might contribute to this reduction in diffusivity including enhancement in hydrodynamic drag under confinement, effects of nanoparticle adsorption to the pore walls, and slowing structural dynamics in glycerol due to the combination of the nanometer-scale confinement and the presence of the nanoparticles.