Graphitic Carbon Nitride as a Platform for the Synthesis of Silver Nanoclusters

Graphitic carbon nitride (CN) synthetized by the thermal polycondensation of melamine at 550 °C for 4 h was further exfoliated by heating at 500 °C for 3 h. Silver cations were adsorbed on the exfoliated graphitic carbon nitride (CNE) and then reduced by sodium borohydride forming silver nanoclusters (NCs) with a size of less than 1 nm. The NCs were located on the CNE surface and did not change the CNE properties except for its pore size distribution and thereby specific surface area (SSA). The Ag NCs were able to collect the photoinduced electrons of CNE and thus reduce their recombination with the holes. It was also documented by the increase in the CNE photocatalytic activity in terms of the degradation of antibiotic Ofloxacin. This study demonstrates the ability of CNE to serve as a platform for a simple and fast synthesis of Ag NCs without any stabilizing compounds. Graphic Abstract

Solid State Photoreduction of Silver on Mesoporous Silica to Enhance Antifungal Activity

A solid-state Ultraviolet-photoreduction process of silver cations to produce Ag0 nanostructures on a mesoporous silica is presented as an innovative method for the preparation of efficient environmental anti-fouling agents. Mesoporous silica powder, contacted with AgNO3, is irradiated at 366 nm, where silica surface defects absorb. The detailed characterization of the materials enables us to document the silica assisted photo-reduction. The appearance of a Visible (Vis) band centered at 470 nm in the extinction spectra, due to the surface plasmon resonance of Ag0 nanostructures, and the morphology changes observed in transmission electron microscopy (TEM) images, associated with the increase of Ag/O ratio in energy dispersive X-ray (EDX) analysis, indicate the photo-induced formation of Ag0. The data demonstrate that the photo-induced reduction of silver cation occurs in the solid state and takes place through the activation of silica defects. The activation of the materials after UV-processing is then tested, evaluating their antimicrobial activity using an environmental filamentous fungus, Aspergillus niger. The treatment doubled inhibitory capacity in terms of minimal inhibitory concentration (MIC) and biofilm growth. The antimicrobial properties of silver–silica nanocomposites are investigated when dispersed in a commercial sealant; the nanocomposites show excellent dispersion in the silicon and improve its anti-fouling capacity.

Silver quasi-nanoparticles: bridging the gap between clusters molecular-like and plasmonic nanoparticles

Herein, we report a new strategy for preparing connected silver sub-nanoparticles with unique optical behavior via a selective photo-assisted electrochemical reduction of silver cations in FAU-type zeolite X (FAUX) cages....

Synthetic preparations and atomic scale engineering of silver nanoparticles for biomedical applications

Owning peculiar oxidative effect, silver cations (Ag+) are well-known for antimicrobial properties and explored as therapeutic agents for biomedical applications. Size control with improved dispersion and stability are the key factors...

Silver nanoparticles doped with silver cations, stabilized with maleic acid copolymers: specific structure, antimicrobial properties

The combined composites containing silver nanoparticles and silver cations were proposed. Water-soluble complexes of silver nanoparticles (AgNPs) stabilized by copolymers of maleic acid with ethylene or N-vinylpyrrolidone were doped with...

THE PROCESS OF SELF-ORGANIZATION IN LOW-CONCENTRATED AQUEOUS SYSTEMS BASED ON N-ACETYL-L-CYSTEINE, L-CYSTEINE AND SILVER ACETATE

Проведено комплексное исследование процесса самоорганизации при сливании низкоконцентрированных водных растворов N-ацетил-L-цистеина и ацетата серебра. Все стадии самоорганизации изучены c помощью измерения величины рН, методов вискозиметрии, УФ спектроскопии и динамического светорассеяния (ДСР). Установлено, что началом самосборки является замена водорода в меркаптогруппе аминокислоты на катион серебра с образованием молекулы меркаптида серебра (МС). Далее происходит образование цепочек вида (-Ag-S(NCys)-Ag-S(NCys)-), при этом происходит протонирование аминокислотных остатков N-ацетил-L-цистеина. Предложен механизм самоорганизации в водном растворе N-ацетил-L-цистеина и ацетата серебра (N-ацетилцистеин-серебряный раствор - НАЦ), заключающийся в образовании агрегатов типа «ядро-оболочка». «Ядро» агрегатов состоит из цепочек вида (-Ag-S(NCys)-Ag-S(NCys)-), «оболочка» агрегатов состоит из протонированных аминокислотных остатков. Связывание таких агрегатов происходит посредством образования связей с ацетат-анионами. A comprehensive study of the self-organization process during the draining of low-concentration aqueous solutions of N-acetyl-L-cysteine and silver acetate was carried out. All stages of self-organization have been studied using pH measurements, viscometry, UV spectroscopy, and dynamic light scattering (DLS). It was found that the first stage of self-assembly is the replacement of hydrogen in the mercapto group of an amino acid with a silver cation with the formation of a silver mercaptide (MS) molecule. Further, the formation of chains of the form (-Ag-S(NCys)-Ag-S(NCys)-) occurs, while excess electron density is retained in amino acid residues, leading to the interaction of chains with both silver cations and undissociated silver acetate molecules , with the formation of clusters. The mechanism of self-organization of the system as the formation of the aggregates of the «core-shell» type is proposed. The «core» consists of chains of the form (-Ag-S(NCys)-Ag-S(NCys)-), the «shell» consists of protonated N-acetyl-L-cysteine resides. Further bonding of aggregates into clusters occurs through free acetic acid anions.