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.

Optical properties of antimony-borate glass rods co-doped with Eu3+/Ag+ ions

This paper presents the results of research on the luminescent properties of antimony-borate glass rods doped with europium and silver ions. The reduction of silver ions to the form of nanoparticles was carried out and the occurrence of localized plasmon resonance was demonstrated, which caused changes in the Eu3+ luminescence signal at a wavelength of 613 nm. The effect of the concentration of silver ions dopant at a constant content of europium ions on the luminescence and absorption characteristics of the produced samples was investigated. In the examined doping range, no large dependencies of spectral changes as a function of the concentration of silver ions were found. A clear quenching of the luminescence was observed due to the heating time of the doped glass matrices for the energy transition (5D0 → 7F2). Full Text: PDF ReferencesS. Kuzman, J. Perisa, V. Dordevic, I. Zekovic, I. Vukoje, Z. Antic and M. D. Dramicanin, "Surface Plasmon Enhancement of Eu3+ Emission Intensity in LaPO4/Ag Nanoparticles", Materials 13, 3071 (2020). CrossRef V.P. Prakashan, M.S. Sajna, G. Gejo, M.S. Sanu, A.C. Saritha, P.R. Biju, J. Cyriac and N.V. Unnikrishan, "Surface Plasmon Assisted Luminescence Enhancement of Ag NP/NWs-Doped SiO2-TiO2-ZrO2:Eu3+ Ternary System", Plasmonics 14, 673 (2019). CrossRef O. Malta, P. Santa-Cruz, G. Sa and F. Auzel, "Fluorescence enhancement induced by the presence of small silver particles in Eu3+ doped materials", J. Lumin., 33, 261 (1985). CrossRef O. Malta, P. Santa-Cruz, G. Sa and F. Auzel, "Time evolution of the decay of the 5Do level of Eu3+ in glass materials doped with small silver particles", Chem. Phys. Lett, 116, 396 (1985). CrossRef J. Zmojda, M. Kochanowicz, P. Miluski et al., "The influence of Ag content and annealing time on structural and optical properties of SGS antimony-germanate glass doped with Er3+ ions", Journal of Molecular Structure 1160, 428 (2018). CrossRef Ki Young Kim, Plasmonics: Principles and Applications (Croatia, InTechOpen 2012) CrossRef M.R. Dousti, M.R. Sahar, S.K. Ghoshal et al., "Up-conversion enhancement in Er3 +-Ag co-doped zinc tellurite glass: Effect of heat treatment", Journal of Non-Crystalline Solids 358, 2939 (2012). CrossRef I. Soltani, S. Hraiech, K. Horchani-Naifer et al., "Effect of silver nanoparticles on spectroscopic properties of Er3+ doped phosphate glass", Optical Materials 46, 454 (2015). CrossRef R. Schneider, E.A. de Campos, J.B.S. Mendes, J.F. Felix, P.A. Santa-Cruz, "Lead–germanate glasses: an easy growth process for silver nanoparticles and their promising applications in photonics and catalysis", RSC Advances 7 (66), 41479 (2017). CrossRef

Supercritical hydrothermal synthesis of silver nanoparticles, composites, and their characterizations

Silver nanoparticles (AgNPs) and silver nanoparticles doped activated carbon (AC-Ag) composite materials were synthesized by hydrothermal processes in supercritical water conditions (29 MPa and 400 °C) using batch reactor. We studied the influence of the precursor solution concentration, reaction temperature under the hydrothermal conditions, and synthesis time on the properties of synthesized materials. The properties of plain AgNPs and AC-Ag composite materials synthesized in supercritical water, including crystallinity, particle size, and molecular interactions between AC and Ag were investigated, comprehensively. Compared to the plain AgNPs, the activated carbon-supported Ag nanocomposite was synthesized faster due to the active functional groups of activated carbon. Furthermore, the FTIR results reveal that the silver nanoparticles are attached to the activated carbon surface in the presence of oxygen bonded carbonyl and carboxyl groups. The nano-sized metal silver particles were observed on the AC surface when analyzed by TEM and XRD. All results imply that the supercritical water condition allows the formation of silver particles less than 100 nm either in the form of plain particles or deposited on the activated carbon surface using the silver acetate precursor solution. This environmentally benign supercritical hydrothermal process can replace the conventional method and become a novel synthesis method for preparing various new materials.

Synthesis of Colloidal Silver Using Lignosulfonates

Colloidal silver solutions can be used as catalysts for carrying out various chemical transformations of organic substances and solving the problems of disposal of toxic compounds, as well as antibacterial agents for combating pathogenic microflora, in the manufacture of lubricants and light-absorbing materials, coatings, sensors, conductive pastes, and high-performance electrode materials. The research purpose is to study the synthesis of colloidal silver using a solution of technical lignosulfonates (LST) as a stabilizer. Colloidal silver was synthesized as a result of the reduction-oxidation (redox) reaction of Ag(I) cations with glucose at 100 °C in the presence of lignosulfonates. The reaction was carried out in an alkaline medium, which is provided by the addition of ammonia water. Electronic spectroscopy was used to control the synthesis of colloidal silver. After the reaction, the solution turned dark brown and an intense absorption band with a maximum at 400 nm appeared on the electron spectra. The effects of reagent consumption and synthesis duration were studied. It was found that the optimal reagent consumption in the colloidal silver synthesis is as follows: 2.5–5 g glucose / g Ag, 0.3–1 g LST / g Ag, and 3–5 g NH3 / g Ag. The synthesis duration is 2–5 min. The resulting colloidal silver solution is stable for several months. Partial stratification without precipitation is observed during the solution storage. It is shown experimentally that the stratification is followed by a redistribution of colloidal silver particles. Electron spectroscopy confirmed the absence of colloidal silver particles in the upper layer. The reaction kinetics has been studied in experiments carried out under thermostatically controlled conditions at temperatures from 50 to 100 °C. The kinetic dependence is described by a first-order equation at the initial stage of the reaction, the duration of which depends on the temperature. The duration of the active part of the kinetic curves is 15–90 % of the total reaction time. The logarithm of the rate constant on the active section was proved to depend linearly on the reverse thermodynamic temperature (pair correlation coefficient is 0.9887). The activation energy was 47 kJ/mol. For citation: Plakhin V.A., Khabarov Yu.G., Veshnyakov V.A. Synthesis of Colloidal Silver Using Lignosulfonates. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 6, pp. 184–195. DOI: 10.37482/0536-1036-2021-6-184-195

The Application of Nanomaterials in Cell Autophagy

Autophagy is defined as separation and degradation of cytoplasmic components through autophagosomes, which plays an essential part in physiological and pathological events. Hence it is also essential for cellular homeostasis. Autophagy disorder may bring about the failure of stem cells to maintain the fundamental transformation and metabolism of cell components. However, for cancer cells, the disorder of autophagy is a feasible antitumor idea. Nanoparticles, referring to particles of the size range 1-100 nanometers, are appearing as a category of autophagy regulators. These nanoparticles may revolutionize and broaden the therapeutic strategies of many diseases, including neurodegenerative diseases, tumors, muscle disease, and so on. Researches of autophagy-induced nanomaterials mainly focus on silver particles, gold particles, silicon particles, and rare earth oxides. But in recent years, more and more materials have been found to regulate autophagy, such as nano-nucleic acid materials, nanofiber scaffolds, quantum dots, and so on. The review highlights that various kinds of nanoparticles have the power to regulate autophagy intensity in stem cells of interest and further control biological behaviors, which may become a reliable treatment choice for disease therapy.

The Inhibition of wine microorganisms by silver nanoparticles

The presented work aimed to study the inhibition using nanoparticles produced by the green synthesis in selected acetic acid and lactic acid bacteria, which are related to viticulture. The degree of ability to eliminate silver particles produced by green syntheses was determined using the plate method on Petri dishes. This is done using two different approaches - the method of direct application of the solution to the surface of the inoculated medium (determination of inhibition zones) and the method of application using nanoparticles to the inoculated medium. Gluconobacter oxydans (CCM 3618) and Acetobacter aceti (CCM 3620T) were studied from acet acetic bacteria. The lactic acid bacteria were Lactobacillus brevis (CCM 1815) and Pediococcus damnosus (CCM 2465). The application of silver nanoparticles was always in concentrations of 0, 0.0625, 0.125, 0.25, 0.5, and 1 g.L-1. All applied concentrations of silver nanoparticles showed an inhibitory effect on the monitored microorganisms. Silver particles could be used in wine technology for their antibacterial effects, mainly to inhibit microorganisms during vinification, as a substitute for sulfur dioxide.