Abstract
Controlled deposition of nanoparticles and bioparticles is necessary for their separation and purification by chromatography, filtration, food emulsion and foam stabilization, etc. Compared to numerous experimental techniques used to quantify bioparticle deposition kinetics, the quartz crystal microbalance (QCM) method is advantageous because it enables real time measurements under different transport conditions with high precision. Because of its versatility and the deceptive simplicity of measurements, this technique is used in a plethora of investigations involving nanoparticles, macroions, proteins, viruses, bacteria and cells. However, in contrast to the robustness of the measurements, theoretical interpretations of QCM measurements for a particle-like load is complicated because the primary signals (the oscillation frequency and the band width shifts) depend on the force exerted on the sensor rather than on the particle mass. Therefore, it is postulated that a proper interpretation of the QCM data requires a reliable theoretical framework furnishing reference results for well-defined systems. Providing such results is a primary motivation of this work where the kinetics of particle deposition under diffusion and flow conditions is discussed. Expressions for calculating the deposition rates and the maximum coverage are presented. Theoretical results describing the QCM response to a heterogeneous load are discussed, which enables a quantitative interpretation of experimental data obtained for nanoparticles and bioparticles comprising viruses and protein molecules.
Highlights
Effective deposition of particles on various surfaces is important for many practical processes, such as water and wastewater filtration, flotation, separation of toner and ink particles, coating formation, paper making, catalysis, colloid lithography, food emulsion and foam stabilization, etc
To experimentally determine the significance of these effects, one should acquire information about adsorption kinetics for the same solute/interface system using complementary experimental techniques. This was realized in several investigations applying ex situ experimental methods such as ellipsometry [26], surface plasmon resonance (SPR) [31], OWLS [26,27,28], atomic force microscopy (AFM) and XPS [49,50,62]
In Refs. [56,57,59], more direct methods were developed to monitor the dry mass of adsorbed proteins in situ using reflectometry, ellipsometry and SPR measurements
Summary
Effective deposition of particles on various surfaces is important for many practical processes, such as water and wastewater filtration, flotation, separation of toner and ink particles, coating formation, paper making, catalysis, colloid lithography, food emulsion and foam stabilization, etc. Considering these facts, one can postulate that a proper interpretation of QCM data requires a careful analysis of the influence of all the above-mentioned parameters and a reliable theoretical framework furnishing reference results for some well-controlled systems such as spherical particles under the rigid contact regime Providing such results is a primary motivation of this work, which is organized as follows: in Section 2, the kinetics of particle deposition on planar interfaces under diffusion and flow conditions are discussed, and the limiting solutions for the initial deposition rates and the maximum coverage are presented.
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