Investigation of Self-Organization Processes in Low-Concentration Aqueous Solutions of L-Cysteine and Silver Citrate

The effect of citric acid on the self-organization processes in aqueous solutions containing L-cysteine and silver citrate has been studied using viscometry, UV-Vis and FTIR spectroscopy, and dynamic light scattering. It has been shown that the introduction of citric acid accelerates self-organization and leads to the formation of nanoparticles and supramolecular complexes of the Ag0/Ag+/Cys type. It has been found that these systems form a silver nanoparticle sol with particle sizes ranging from 15 to 50 nm and a zeta potential of approximately 75 mV. The degree of dissociation of silver citrate and the concentration of citrate anions play a key role in the self-organization mechanism. An increase in the content of citrate anions promotes the growth of the hydrodynamic diameter of particles (up to 80–170 nm) and the formation of micron-sized aggregates, which is confirmed by zeta potential data (5–35 mV). These results are important for understanding the mechanisms of nanostructure formation based on biomolecules and metal ions and can be used in the development of new functional materials.