Morga M, Adamczyk Z, Kosior D
Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Cracow, Poland.
Phys Chem Chem Phys. 2017 Aug 30;19(34):22721-22732. doi: 10.1039/c7cp03876c.
Even though silica nanoparticles and their monolayers find a broad field of applications, only a few studies providing a quantitative description of silica nanoparticle deposition at solid/liquid interfaces have been reported in the literature. Given the deficit of reliable experimental data, the goal of this work is to acquire thorough physicochemical characteristics of amorphous silica nanoparticle deposition. Silica nanoparticle monolayers of controlled coverage were formed on macroion (PAH)-modified mica. The size of the particles determined by dynamic light scattering (DLS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) was equal to 28 nm. The electrophoretic mobility and the zeta potential of the particles were also determined as a function of ionic strength and pH. Using a well-defined suspension, systematic studies of particle deposition kinetics were carried out. The coverage of the self-assembled particle monolayers was determined by AFM and SEM imaging. Particle deposition was carried out under diffusion controlled transport conditions. For long deposition times, the saturation coverage was attained, systematically increasing with ionic strength up to 0.48 for I = 0.15 M NaCl. The deposition kinetic runs were adequately interpreted using the random sequential adsorption (RSA) model. This model was also used to determine the specific density of silica particles that confirmed their porous structure. In addition, the particle desorption kinetics was studied using AFM and SEM methods. It was confirmed that silica nanoparticle desorption was negligible within the time period of 60 hours. Our experimental data proved, therefore, that it is feasible to produce uniform and stable silica particle monolayers of desired coverage in the self-assembly processes, controlled by the bulk suspension concentration and the ionic strength. Such monolayers may find practical applications as substrates for selective protein and nanoparticle deposition, or various catalytic applications.
尽管二氧化硅纳米颗粒及其单分子层有广泛的应用领域，但文献中仅报道了少数几项对二氧化硅纳米颗粒在固/液界面沉积进行定量描述的研究。鉴于可靠实验数据的匮乏，本工作的目标是获取非晶态二氧化硅纳米颗粒沉积的全面物理化学特性。在经聚电解质（PAH）修饰的云母上形成了可控覆盖率的二氧化硅纳米颗粒单分子层。通过动态光散射（DLS）、原子力显微镜（AFM）和扫描电子显微镜（SEM）测定的颗粒尺寸为28 nm。还测定了颗粒的电泳迁移率和zeta电位随离子强度和pH的变化。使用定义明确的悬浮液，对颗粒沉积动力学进行了系统研究。通过AFM和SEM成像确定自组装颗粒单分子层的覆盖率。颗粒沉积是在扩散控制传输条件下进行的。对于较长的沉积时间，达到了饱和覆盖率，随着离子强度的增加系统地增加，对于I = 0.15 M NaCl，饱和覆盖率高达0.48。使用随机顺序吸附（RSA）模型对沉积动力学运行进行了充分解释。该模型还用于确定二氧化硅颗粒的比密度，证实了它们的多孔结构。此外，使用AFM和SEM方法研究了颗粒解吸动力学。证实了在60小时的时间段内二氧化硅纳米颗粒的解吸可忽略不计。因此，我们的实验数据证明，在自组装过程中，通过本体悬浮液浓度和离子强度控制，制备具有所需覆盖率的均匀且稳定的二氧化硅颗粒单分子层是可行的。这样的单分子层可作为选择性蛋白质和纳米颗粒沉积的底物或各种催化应用找到实际应用。
