Effect of Glutathione on the Destruction Kinetics of Silver Nanoparticles in Aqueous Solutions: An Optical Study under Neutral and Alkaline Conditions

The interaction of nanostructured metal particles with the molecular components of biosystems differs significantly from the processes that take place in the presence of ions of the same metals. This unequivocally indicates the need to take into account not only the course of chemical processes but also implies to discuss certain physical effects that are usually neglected when considering such interactions. In this work, we studied the interaction of silver nanoparticle dispersion (Ag-NP) in ethylene glycol with a particle size less than 100 nm (Sigma-Aldrich 658804) with glutathione in a water and carbonate buffer (pH 10). The choice of glutathione (GSH) is due to the fact that it plays a significant role in intracellular processes, participating in the protection of intracellular components from the toxic effects of heavy metal ions; at the same time, differences in its interaction with silver ions and nanoparticles were experimentally demonstrated. A series of optical studies of the absorption and emission spectra of solutions of silver nanoparticles with GSH was carried out in order to establish the dominant processes in the system. It was shown that the above-mentioned silver nanoparticles in aqueous solutions spontaneously decompose over time, while glutathione differently affects these processes in water and carbonate buffer. It was shown that not only the local surface plasmon resonance bands but also the emission spectra of Ag-NP~GSH solutions in the region of 350–550 nm change with time. The sources of such radiation can be carbon quantum dots (CQD), which, according to published data, can be formed during the synthesis of silver nanoparticles and effectively luminesce in this region of the spectrum. Raman spectroscopy data confirm the presence of CQD in the Ag-NPs solution. The presence of quantum dots in the system makes it possible to indirectly track the presence of silver nanoparticles, which are booster centers, enhancing the emission of CQDs. The studies allow us to state that the interaction of glutathione with silver nanoparticles is a complex topochemical process in which, in addition to chemical reactions, the processes of transformation of silver nanoparticles and changes in the distribution of their sizes and chemical/physical functionality take place.