We discuss the results of experimental studies of the processes of gelation in aqueous solutions of silver nitrate with l-cysteine and its derivatives. We focus on understanding what determines if these small molecules will self-assemble in water at their extremely low concentration to form a gel. A mechanism of gel formation in a cysteine-silver solution (CSS) is proposed. The analysis of the results indicates that filamentary aggregates of a gel network are formed via interaction of NH and C(O)O groups that belong to neighboring silver mercaptide (SM) aggregates. In turn, formation of sulphur-silver bonds between silver mercaptide molecules is responsible for self-assembling these molecules into SM aggregates which can be considered as supramonomers. Free polar groups located on the surfaces of the aggregates can form hydrogen bonds with water molecules, which explains the unique ability of CSS hydrogels to trap water at low concentrations of low-molecular-weight hydrogelators.

The present article reports the in situ preparation of silver nanoparticles (AgNPs) homogeneously distributed in the formig gel matrix using only L-cysteine (CYS) as a bio-reducing agent. The complex of...

We report a new supramolecular hydrogel based on the simplest low molecular weight compounds – amino acid and silver salt. In situ formation of silver nanoparticles during self-assembly process shows...

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Several physicochemical analytical methods were used to study aqueous solutions and hydrogels based on L-cysteine and silver nitrate. It was found that anions played a decisive role in forming the threedimensional gel-network in dilute silver-cysteine solutions. The ability to use silver-cysteine solutions and hydrogels to prepare bactericidal fi bers and fabrics was examined.Self-assembly of supramolecular structures in solutions has recently attracted increased worldwide interest. This timely problem comprises studies of the formation of very important physicochemical and biological entities such as micelles, liposomes, lipoproteides, membranes, clusters, immune complexes, physical gels, etc.[1]. A common feature of the aforementioned entities is the absence of strong chemical bonds between the interacting components. The driving forces for forming the respective structures are electrostatic and van-der-Waals interactions, hydrophobic effects, H-bonds, and weak donor-acceptor bonds. Dilute gels occupy a special place among these entities. Only a few such molecular systems are known. In particular, they include the polysaccharide agar-agar, mixtures of muscle proteins, and calcium germinate [2].Gel formation in an aqueous solution with a low concentration of domestically produced L-cysteine and silver nitrate was fi rst established several years ago [3,4].The heightened interest in this system is completely understandable. First, the hydrogel is a unique model system for studying self-assembly processes in dilute aqueous solution (concentration 0.1% and lower). Second, the system can be used in medical practice as an independent medical preparation or as a matrix for formulating other preparations because of the presence of silver in it.The fact that silver in its various forms (ions, salts, colloidal solutions, nanoparticles) has been used for a long time in medical practice argues in favor of the second factor. The antibacterial properties of this element are well known. Interest in the use of silver to treat infectious diseases decreased with the emergence of antibiotics. However, many antibiotics have recently become obsolete because of the appearance of resistance to them in constantly evolving new strains of bacteria. This opens broad possibilities for the use of silver as an alternative to antibiotics that have become ineffective [5].A problematic issue for the use of silver nanoparticles and ions is the choice of the matrix for their practical application. Solutions of silver nanoparticles and ions, most often aqueous but other solvents are also employed, are used most commonly. Silver in such a form is used to prepare infusions, preservatives for various media, and disinfectants for medical instruments.Furthermore, materials consisting of either a solid compound (inorganic matrices, in particular silica gel) or condensed substances (gels, polymers) are often used as the matrix [6][7][8]. The practical application of silver is broadest for matrices of block polymers and gels such as suturing materials, w...

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The crystalline phase in gels and solid gel-derived samples of ultrahigh molecular weight polyethylene was studied using the infrared spectroscopy, low-frequency Raman spectroscopy and wideangle X-ray scattering methods. The spectroscopic data evidence the presence in gels of tiny crystallites whose thickness (3-5 nm) depends on the sort of the solvent used and it is insensitive neither to the concentration of the diluted solution, nor to the molecular weight of the polymer. After removal of the solvent, there appear crystalline clusters composed of closely attached folded platelets. The total thickness of these stacked entities is about 10-20 nm while their transverse size reaches ∼50 nm. In addition, the crystalline domains in the gelled material exhibit a kind of mosaic structure which is much more pronounced in solid xerogels than in wet gels.

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