Agglomeration of Nanoparticles Synthesized by Spark Discharge

Abstract Nanoparticle agglomeration presents a major challenge, as it leads to a degradation of their functional characteristics. In this paper, we study the problem of agglomeration of nanoparticles obtained by the spark method in 1% sodium chloride (NaCl) solution and kept for 100 days. Analysis of particle size distribution revealed a significant shift of the main fraction from the nanorange (25–75 nm) to the range of 1–10 μm, which indicates a high degree of agglomeration with an increase in the particle size by an average of 85 times (agglomeration index is ~85). The main causes of agglomeration are the high specific surface area of nanoparticles, which promotes their adhesion, the influence of the ionic environment of the NaCl solution, screening electrostatic repulsion and heterogeneity of the surface properties of the particles due to the synthesis method. To prevent agglomeration, it is proposed to optimize the spark discharge parameters, use less ionic media, reduce the electrolyte concentration and add stabilizers such as citrates. The results highlight the critical importance of controlling storage conditions and time to ensure the stability of colloidal solutions of nanoparticles.

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