Hydrogels Based on Ag+ -Modulated Assembly of 5'-Adenosine Monophosphate for Enriching Biomolecules

Supramolecular hydrogels obtained by combining 5'-adenosine monophosphate (AMP) with Ag⁺ were fabricated in this work. Their gelation capability was enhanced by increasing the concentration of Ag⁺ or decreasing the pH. The gels are very sensitive to light, which endows them with potential applications as visible-light photosensitive materials. Coordination between the nucleobase of AMP and Ag⁺ , as well as π-π stacking of nucleobases, are considered to be the main driving forces for self-assembly. The hydrogels successfully achieved the encapsulation and enrichment of biomolecules. Hydrogen bonding between the amino group of guest molecules and silver nanoparticles along the nanofibers drives the enrichment and is considered to be a crucial interaction.

Gas-phase self-assembly of uniform silica nanostructures decorated and doped with silver nanoparticles

We report a systematic study of the controlled gas-phase synthesis of silver-silica hybrid nanostructures (Ag-SiO₂ NP) using the concept of evaporation-induced self-assembly. The approach includes the use of a direct gas-phase electrophoresis for size classification and in situ characterization of mobility size. Transmission electron microscopy and ultraviolet-visible light spectroscopy were employed complementarily to determine the morphology and surface plasmon resonance of Ag-SiO₂ NP. Results show that two types of Ag-SiO₂ NPs were successfully synthesized: (1) AgNPs decorated on a SiO₂-NP (Ag-T-SiO₂ NP), and (2) AgNPs doped in a cluster of SiO₂-NPs (Ag-C-SiO₂ NP). The physical size, morphology, and compositions of Ag-SiO₂ NPs were tunable through the adjustments of precursor concentrations and the selected mobility sizes. The results also show that SPR performance, colloidal stability, and dispersibility of AgNPs enhanced significantly in an aqueous environment after the hybridization with SiO₂-NP (especially for Ag-C-SiO₂ NP). The results and corresponding methodology summarized here provide the proof of concept to fabricate high-purity AgNP-based hybrid nanostructures through gas-phase evaporation-induced self-assembly for future biomedical applications (e.g., hyperthermal therapy, targeted drug delivery, and antibacterial applications).

Ultrafine Au and Ag Nanoparticles Synthesized from Self-Assembled Peptide Fibers and Their Excellent Catalytic Activity

The self-assembly of an amphiphilic peptide molecule to form nanofibers facilitated by Ag(+) ions was investigated. Ultrafine AgNPs (NPs=nanoparticles) with an average size of 1.67 nm were synthesized in situ along the fibers due to the weak reducibility of the -SH group on the peptide molecule. By adding NaBH4 to the peptide solution, ultrafine AgNPs and AuNPs were synthesized with an average size of 1.35 and 1.18 nm, respectively. The AuNPs, AgNPs, and AgNPs/nanofibers all exhibited excellent catalytic activity toward the reduction of 4-nitrophenol, with turnover frequency (TOF) values of 720, 188, and 96 h(-1) , respectively. Three dyes were selected for catalytic degradation by the prepared nanoparticles and the nanoparticles showed selective catalysis activity toward the different dyes. It was a surprising discovery that the ultrafine AuNPs in this work had an extremely high catalytic activity toward methylene blue, with a reaction rate constant of 0.21 s(-1) and a TOF value of 1899 h(-1) .

Thermosensitive antibacterial Ag nanocomposite hydrogels made by a one-step green synthesis strategy

Clay nanosheets act as a catalyst and stabilizing agent for rapid in situ synthesis of silver nanoparticles in a hydrogel matrix.

Self-Assembled Peptide Nanofibers Encapsulated with Superfine Silver Nanoparticles via Ag⁺ Coordination

We demonstrate that a glutanthione-based oligopeptide, Fmoc-GCE, could self-assemble into nanofibers induced by Ag(+) ions in NaOH solution. During the self-assembly process, the superfine silver nanoparticles were in situ produced on the nanofibers. On the basis of a series of characterizations, we proposed the possible mechanism of the self-assembly, for which the coordination interaction between Fmoc-GCE and Ag(+) ions as well as the π-π stacking of fluorenyl groups were the main driving forces of the self-assembled nanofibers. At appropriate compositions, the 3D networks of Fmoc-GCE/NaOH/Ag(+) nanofibers could further form metallogel, which was responsive to pyridine and melamine, which could coordination with Ag(+) ions. Moreover, the nanofibers encapsulated with superfine silver nanoparticles exhibited catalytic ability in degradation of the azo dye and the antibacterial properties to both Gram negative (E. coli) and Gram positive (S. aureus) bacteria.

High-speed water sterilization using silver-containing cellulose membranes

The removal of bacteria and other pathogenic micro-organisms from drinking water is usually carried out by boiling; however, when this is not a feasible option, a combination of treatment based on filtration and disinfection is recommended. In this work, we produced cellulose filters grafted with silver nanoparticles (AgNPs) and silver nanowires (AgNWs) by covalent attachment of separately prepared Ag nanostructures on thiol- and amine-modified commercially available cellulosic filters. Results obtained from scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectroscopy (EDS) all revealed that such modified cellulose membranes contained large amounts of homogeneously dispersed AgNPs, whereas X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the aforementioned nanostructures were immobilized on the membrane with a strong and stable covalent bond between the thiol or amine groups and the surface of the Ag nanofillers. This durable and robust covalent attachment facilitated outstanding suppression of the uncontrolled release of the nanostructures from the membranes, even under strong ultrasonication. Those membranes also demonstrated high permeance and antimicrobial activity in excess of 99.9% growth inhibition against Escherichia coli, which was used as a model of gram-negative coliform bacteria. Bacteria percolated throughout the tortuous silver-loaded filters, thus increasing the chances of contact between the Ag nanostructures (wires or nanoparticles) and the passing bacteria. Thus, we anticipate that these filters, with their high antibacterial activity and robustness, can be produced in a cost-effective manner and that they would be capable of producing affordable, clean, and safe drinking water in a short period of time without producing an uncontrolled silver release into the percolated water.