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

Solvothermal Synthesis of YF3:Ce3+ Nanophosphors for Medical Applications

In this paper, the time effect of hydrothermal synthesis on YF3 morphology particles is considered. The work was carried out on X-ray-excited YF3:Ce3+ phosphors. The synthesis was carried out by the hydrothermal method, since it avoids high temperatures leading to particle agglomeration. The first stage of research consisted in identifying the most favorable medium for obtaining the required phase and size - water or organic matter (ethylene glycol and ethanol). Research has shown that ethylene glycol has all the advantages: it prevents agglomeration, allows us to get the required phase. Hydrothermal synthesis of YF3 samples to determine the optimal synthesis time was carried out according to the same scheme - in an organic medium of ethylene glycol without using stabilizers for 4, 8, 12, 16, 20 hours. Our study showed that it is possible to obtain a YF3 sample that meets the necessary requirements (including nanoscale) within 16 hours, moreover, without the use of stabilizers. In parallel with the study of the synthesis duration, an experiment was carried out on the effect of various stabilizers on the properties of the YF3:Ce3+ phosphors (5%). The synthesized nanophosphors possessed effective X-ray luminescence with a maximum in the region of 300 nm, which makes it possible to use them in the composition of preparations for PDT.

Synthesis of Y2O3: Eu Nanosized Phosphor Using Hydrothermal Technique and Rapid Thermal Annealing (RTA)

The application of special nanomaterials is promising for the development of new methods for the diagnostics and treatment of cancer. Photodynamic therapy (PDT) is a well-known and recognized method of cancer treatment. This type of therapy is less carcinogenic and mutagenic compared to radiation and chemotherapy, since the applied photosensitizers do not bind to DNA of the cells. However, currently this technique is only applicable to skin cancer, while its extension to the treatment of abdominal tumors requires the creation of pharmacological drugs for PDT, which along with a photosensitizer include a colloidal solution of nanosized luminescent phosphor emitting visible light with the required wavelength under the influence of infrared, X-ray or γ-radiation, which easily penetrates the body tissues. Since photosensitizers are already available as commercial products, the most important goal is the development of nanosized phosphors providing the required radiation convertion. In this study, the effects of hydrothermal synthesis, duration and the conditions of rapid thermal annealing (RTA) on Y2O3:Eu phosphor particle size were studied. The hydrothermal synthesis technique was carried out in two ways: chloride (precipitation from a chloride solution using NaOH and NH4OH precipitators) and acetate (decomposition of mixed acetate either without a dispersant at 230° C for 24 hours, or using PEG-200 and PEG-2000 as dispersants at 230 °C for 12 hours). The rapid thermal annealing was performed either at 600 °C for 20 minutes, or at 800 °C for 5 minutes. The developed synthetic approaches afforded Y2O3:Eu nanosized phosphor samples with the particle size not exceeding 200 nm.

Получение карбида титана в атмосферной электроразрядной плазме

The paper discusses the experimental studies connected with development of scientific and technical foundations for the synthesis method of titanium carbide by electric arc discharge plasma under ambient air condition. According to the X-ray diffraction data, the dependences between the product phase composition and the synthesis duration was determined. According to the scanning electron microscopy and energy dispersive analyses data, a morphological types number of titanium carbide particles, which are formed as a result of uneven distribution of energy in the reaction volume, was identified.

Zeolite RHO Synthesis Accelerated by Ultrasonic Irradiation Treatment

In recent years, there are increasing interest on applying ultrasonic irradiation for the synthesis of zeolite due to its advantages including remarkable shortened synthesis duration. In this project, the potential of ultrasonic irradiation treatment on the synthesis of zeolite RHO was investigated. Ultrasonic irradiation treatment time was varied from 30 to 120 minutes for the synthesis of zeolite RHO. The zeolite RHO solid samples were characterized with X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and nitrogen adsorption-desorption analysis. The application of ultrasonic irradiation treatment in this study has accelerated the synthesis of zeolite RHO where the synthesis duration has been significantly shortened to 2 days compared to 8 days required by conventional hydrothermal heating without ultrasonic irradiation treatment. Highly crystalline zeolite RHO crystals in truncated octahedron morphology were successfully formed.

SYNTHESIS AND OPTICAL PROPERTIES OF NANOCOMPOSITES BASED ON LIQUID CRYSTAL WITH BIMETALLIC Au + Ag NANOPARTICLES OF ALLOY TYPE.

In this work, we have carried out a research which aimed to obtain complex nanoparticles of noble metals Au + Ag in the form of bimetallic alloys. Bimetallic nanoparticles were synthesized directly in a liquid-crystalline cadmium caprylate melt in an argon atmosphere in the temperature range of mesophase existence by the simultaneous chemical reduction of cations of gold (Au3+) and silver (Ag+) from their compounds, tetrachloroaurate acid (H[AuCl4]×3Н2О) and silver nitrate AgNO3, respectively. The effect of synthesis duration (3 and 5 hours) on the spectral behavior of binary nanoparticles have been studied. It has been shown that when the synthesis duration is 3 h, mainly homogeneous bimetallic alloys are obtained, and when it is 5 h, both homogeneous and gradient alloys can be obtained. The absorption spectra of homogeneous alloys are characterized by the presence of one surface plasmon resonance (SPR) peak, which occupies an intermediate position relative to the SPR peaks for monometallic nanoparticles, i.e. between 425 and 560 nm. When forming heterogeneous alloys, which are formed in the molar ratio range where the amount of silver ions predominates, the absorption spectra exhibit two SPR peaks which relate to nanoparticles with different metallic silver content. The formation of metallic nanoparticles containing different metals may be due both to the different mobility of noble metals ions in the liquid crystal matrix and to the different rate of rearrangement of metals in the new formed heteronanoparticle. It has been found by electron spectroscopy and transmission electron microscopy that the nanoparticles in this matrix have mostly a spherical shape with a mean diameter of 15 nm. The possibility of the fine control of the position of SPR peak of bimetallic nanoparticles in a liquid crystal matrix over a wide optical range of 422–580 nm is shown.

Influence of pH and Synthesis Duration on the Composition and Thermal Behavior of Hydrolysis Products of Lanthanum Nitrate

The study investigates the hydrolysis products of lanthanum nitrate, obtained at various pH values and times of the hydrolytic agent addition. It has been found that the structure formation of lanthanum oxyhydroxide is accompanied by capturing the admixture ions, namely, the anions of the reactant salt and carbonate ions. It has been shown that thermal decomposition of the hydrolysis products proceeds in four stages for faster hydrolysis. If hydrolysis is slow, the intervals merge together into three stages of thermal decomposition. The hydrolysis products of lanthanum nitrate, heated up to 500...550 С, actually consist of lanthanum oxide containing nitrate and carbonate, chemically bonded to the oxide matrix, in its inner regions. The composition of the synthesized samples changes if pH varies. The minimal content of admixture ions can be observed at the synthesis pH > 10, if the time of the hydrolytic agent addition equals 24 h. The obtained results suggest that lanthanum nitrate can be used as a precursor for synthesis of structured lanthanum oxide.

MICROWAVE-HYDROTHERMAL HEXAMETHYLENETETRAMINE-MEDIATED SYNTHESIS OF NANOCRYSTALLINE MnO2

The article considers a non-conventional approach to the synthesis of various polymorphic modifications of manganese dioxide. The approach consists in hydrothermal microwave processing of a reaction mixture containing potassium permanganate and hexamethylenetetramine. We emphasize the relevance of the work due to such MnO2 properties as catalytic and photocatalytic activity, its application in accumulators, supercondensers and biochemistry. We report on the first detailed study on the role of temperature, synthesis duration and pH value on the phase composition and morphology of nanocrystalline MnO2. We show that the phase composition of manganese dioxide is largely determined not only by temperature, synthesis duration and pH value, but also by the acid added to the reaction mixture (nitric or sulphuric). In particular, the presence of sulfuric acid apparently results in α-MnO2 stabilization. It is noted that the type of the acid used in the course of the synthesis, as well as other synthesis conditions exercise no significant influence neither on the shape nor on the size of α-, γ- and δ-MnO2 particles. In contrast, the morphology of β-MnO2 turned out to be extremely sensitive to the synthesis conditions. Long (24 h) hydrothermal processing of reaction mixtures at рН 0.5-1 results in the formation of single-phase pyrolusite. The microstructure of the latter is determined by the reaction mixture composition.

Hydrothermal Growth of 1D ZnO Nanorods Thin Films for Hydrogen Gas Production through Water Splitting Reaction

Current study aims to control the growth of vertically aligned zinc oxide (ZnO) nanorods (NRs) arrays on indium tin oxide (ITO) substrate with tuneable diameter and length by using hydrothermal method. FESEM result shows that the diameter of NRs are tuneable from 95 nm to 107 nm and its length can be varied from 2.0 μm to 5.0 μm by prolonging the synthesis duration. According to FESEM images, extent the synthesis duration renders denser NRs occupancy. XRD result reveals that the NRs have prefer orientation along 002 direction, which is distinguishly different from relative peak intensity of standard ZnO. The NRs are employed as photocatalyst thin film to produce hydrogen gas (H2) via photocatalytic water splitting reaction.