Mechanisms of Anisotropic Particle Deposition: Prolate Spheroid Layers on Mica

Abstract

Anisotropic particle deposition was investigated using the streaming potential method complemented with the atomic force microscopy (AFM) determination of the absolute particle coverage. The polymer particles were synthesized using the stretching procedure with consecutive oxidation of surface hydroxyl groups and coupling of polyethyleneimine. The bulk particle physicochemical properties were characterized by scanning electron microscopy (SEM), dynamic light scattering, and laser Doppler velocimetry. The particles were positively charged in the pH range of 3−10, exhibiting a prolate spheroid shape with an axis ratio of five. Thorough AFM and in situ optical microscopy measurements yielded the adsorption kinetics of particles under the diffusioncontrolled regime. The experimental data were adequately interpreted in terms of the random sequential adsorption model with the surface blocking function derived from the scaled particle theory. The root-mean-square (rms) parameter of the layers for a broad range of particle coverage was also determined and interpreted using the topographical model developed in this work. The experiments were complemented by the measurements of the streaming potential of particle layers under various ionic strengths and pHs. The ζ (zeta)-potential data acquired in this way enabled to determine the universal hydrodynamic function describing the dependence of the streaming potential on the particle coverage. The function was used to express the ζ-potential of surfaces covered by particles in terms of substrate rms. It was argued that the acquired results, in addition to being significanct to basic science, can be exploited as useful reference systems for quantitative interpretation of bioparticle deposition on abiotic surfaces.

Quantifying Nanoparticle Layer Topography: Theoretical Modeling and Atomic Force Microscopy Investigations

“…It is also worth mentioning that the normalized rms / d p abruptly increases for low particle coverage but never exceeds the value of 0.5. This is described in the case of spheroids and spheres by the explicit expression italicrms / d p = 0.8416 false[ normalΘ ( 1 − 0.980 Θ ) false] 1 / 2 …”

“…In this respect, the most versatile is atomic force microscopy (AFM) 63,67−69 comprising its highspeed version, 70−72 particularly suited for bioparticles, which directly furnishes the three-dimensional information about the particle layer topography. Such an analysis, comprising the calculation of the rms factor characterizing the magnitude of the surface roughness, was carried out for gold 69 and polymer nanoparticle 73 considered that the AFM method itself has some limitations, mainly stemming from the finite size of the tip leading to the convolution effects 74 and from the discretization of the scanning area. 75 Although the significance of these effects can be decreased by selecting high-quality tips and properly adjusting the scan area to the particle size, the lack of reference theoretical data prohibits a quantitative estimation of the precision of the AFM measurements.…”

“…In this respect, the most versatile is atomic force microscopy (AFM) ,− comprising its high-speed version, − particularly suited for bioparticles, which directly furnishes the three-dimensional information about the particle layer topography. Such an analysis, comprising the calculation of the rms factor characterizing the magnitude of the surface roughness, was carried out for gold and polymer nanoparticle layers on silica. However, it should be considered that the AFM method itself has some limitations, mainly stemming from the finite size of the tip leading to the convolution effects and from the discretization of the scanning area .…”

Competitive random sequential adsorption of binary mixtures of disks and discorectangles

“…The basic variant of RSA assumes the irreversible addition of non-overlapping particles and absence of desorption and diffusion effects. For simple one-component systems, the saturation (jamming) coverages were estimated for disks φ ≈ 0.5471 [5][6][7], and many other shapes, like ellipses, rectangles, squares, discorectangles, needles and fibers, regular polygons and more complex shapes [8][9][10][11][12][13][14][15][16].…”

Two-stage random sequential adsorption of discorectangles and disks on a two-dimensional surface

“…The effects particle shape on structure of packing's have attracted great interest [4]. Continuous RSA problems for particles of various shapes, e.g., for disks [5,6], squares [6,7], cubic particles [8], rectangles [5,[9][10][11][12][13], oriented rectangles [14] discorectangles [4,5,11,15], rounded rectangles, isosceles and right triangles [16], ellipses [5,11,12,15,17,18], hard polygons [19], spheroids [20], and needles [11,12,18,21] were analyzed. For elongated particles, the non-monotonic dependencies of surface coverage φ J versus the aspect ratio ε (width to length ratio) have been typically observed [4].…”