Photochemical Synthesis of Silver Hydrosol Stabilized by Carbonate Ions and Study of Its Bactericidal Impact on Escherichia coli: Direct and Indirect Effects

The great attention paid to silver nanoparticles is largely related to their antibacterial and antiviral effects and their possible use as efficient biocidal agents. Silver nanoparticles are being widely introduced into various areas of life, including industry, medicine, and agriculture. This leads to their spreading and entering the environment, which generates the potential risk of toxic effect on humans and other biological organisms. Proposed paper describes the preparation of silver hydrosols containing spherical metal nanoparticles by photochemical reduction of Ag+ ions with oxalate ions. In deaerated solutions, this gives ~10 nm particles, while in aerated solutions, ~20 nm particles with inclusion of the oxide Ag2O are obtained. Nanoparticles inhibit the bacterium Escherichia coli and suppress the cell growth at concentrations of ~1 × 10−6–1 × 10−4 mol L−1. Silver particles cause the loss of pili and deformation and destruction of cell membranes. A mechanism of antibacterial action was proposed, taking into account indirect suppressing action of Ag+ ions released upon the oxidative metal dissolution and direct (contact) action of nanoparticles on bacterial cells, resulting in a change in the shape and destruction of the bacteria.

Understanding the effects of shape, material and location of incorporation of metal nanoparticles on the performance of plasmonic organic solar cells

Enhanced performance in organic solar cells by incorporating non-spherical metal nanoparticles.

Silver and Gold Ions Recovery from Batch Systems Using Spirulina platensis Biomass

In order to assess ability of Spirulina platensis to recover silver and gold ions from the environment the bioaccumulation of silver and gold ions and their effect on growth, proteins and carbohydrates content of Spirulina platensis biomass was studied. Silver nitrate (AgNO3) in concentration range 0.01-1 mg/dm3 and tetrachloroaurate Na[AuCl4] in concentration range 18.5-370 mg/dm3 were added as component of the Spirulina platensis cultivation medium. In case of silver two cultivation media were studied: standard and Cl-free. The process of silver and gold uptake was traced using neutron activation analysis. Presence of silver ions in standard cultivation medium reduced biomass productivity by 66 %, while in Cl-free biomass productivity was reduced by 11.8 % only. The reduction of proteins content by 30 % in Cl-free medium and by 19 % in standard medium was also observed. The experiments showed that in case of gold ions loading, the biomass productivity and protein content were reduced only at high Na[AuCl4] concentration in the medium. The behaviour of carbohydrates content change was similar under silver and gold loadings: decrease at low metal concentration followed by increase at high metal concentrations. Scanning electron microscopy allowed observation of spherical metal nanoparticles, which were formed extracellularly during silver and gold bioaccumulation. Spirulina platensis can be used for recovery of precious metals as well as metal nanoparticles production.

Формирование наночастиц натрия и калия при локальном электронном облучении щелочно-галоидных кристаллов

It is shown experimentally that during local electron irradiation of NaCl, KCl and KBr crystals by electrons with energy 50 keV spherical metal nanoparticles of sodium and potassium with plasmon resonances in visible spectral region are formed. Optical density spectra of crystals after electron irradiation are presented. By computer simulation the possibility of solid or liquid state of nanoparticles is studied, as well as interference effects, which appear in the irradiated zone of crystals.

The Mixed-Electrode Concept for Understanding Growth and Aggregation Behavior of Metal Nanoparticles in Colloidal Solution

The growth and aggregation behavior of metal nanoparticles can be modulated by surfactants and different other additives. Here the concept of how open-circuit mixed electrodes helps to understand the electrical aspects of nanoparticle growth and the consequences for the particle geometries is discussed. A key issue is the self-polarization effect of non-spherical metal nanoparticles, which causes a local decoupling of anodic and partial processes and asymmetry in the local rates of metal deposition. These asymmetries can contribute to deciding to the growth of particles with high aspect ratios. The interpretation of electrochemical reasons for particle growth and behavior is supported by experimental results of nanoparticle syntheses supported by microfluidics which can supply high yields of non-spherical nanoparticles and colloidal product solutions of high homogeneity.