No abstract

No 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.

No abstract

Given the deficit of works describing the impact of silver nanoparticles (AgNPs) on the growth of crop plants, these studies were devoted to the determination of the influence of the surface properties of charge-stabilized AgNPs on induced phytotoxic effects. Three types of AgNPs of similar size distribution, but of diverse surface properties, were synthesized using trisodium citrate, sodium hexametaphosphate and tannic acid. The suspensions and solution of silver nitrate were applied in a hydroponic culture in order to assess their influence on the germination of Triticum aestivum seeds. Studies of the damage of the cell membrane and the activity of antioxidant enzymes were carried out on the shoots and roots of the seedlings. The differences in the plant condition were assessed while analyzing photosystem II. The results showed that the AgNPs stabilized with sodium hexametaphosphate exhibited a higher toxicity toward the tested plants than silver ions with the same concentration. It was found that the AgNPs obtained using tannic acid exerted an adverse effect on the crop plants. The citrate-stabilized AgNPs were the least toxic to the seedlings. The obtained results demonstrated that the surface properties of AgNPs strongly influence the phytotoxicity toward T. aestivum seedlings.