Organic Dye Solutions Research Articles

Apple leaf-inspired bilayered Janus wood evaporator with decoupled light-vapor interfaces for high-efficiency solar steam generation

Solar-driven interfacial evaporation technology provides a facile and promising strategy for producing clean water from seawater. Wood-based evaporators have recently been extensively explored for solar desalination due to the structural merits and sustainability of natural wood. However, the light absorption and water evaporation functions are commonly integrated at the same surface for a traditional wood-based solar evaporator, which definitely causes mutual interference between the incident sunlight and the generated vapor leading to inevitable energy loss. Herein, inspired by the unidirectional transpiration of hypostomatic apple leaves, a bilayered Janus wood evaporator with decoupled light absorption and water evaporation surfaces was subtly engineered to avoid the sunlight-vapor interference for efficient solar evaporation. The bilayered evaporator consists of a longitudinal wood piece as the water transport layer and a carbonized transverse wood piece infiltrated with polydimethylsiloxane (PDMS) as the photothermal layer. The hydrophilic longitudinal piece with vertically aligned channels can continuously wick water to the evaporation surface, while the hydrophobic transverse piece with horizontal channels enables efficient heat transfer given its high thermal conductivity. Thanks to the unique bilayered configuration, the developed evaporator demonstrates an excellent evaporation rate of 2.12 kg m−2 h−1 with an evaporation efficiency of 92.3 % (1 sun), surpassing most of the traditional wood-based evaporators. Moreover, the bilayered evaporator exhibits good salt resistance and can effectively purify diverse wastewaters including organic dye solutions and oil–water emulsions. This Janus-interface structural design provides a novel strategy for developing high-performance solar evaporator toward clean water production.

PARADONT DISEASES AND MORPHOLOGICAL CHANGES IN TEETH IN HUMANS WORKING WITH CHEMICAL DYES

The article covers the use of various organic and inorganic dye solutions in paint -finishing workshops in the manufacturing industry as well as in all sectors of the textile industry. These chemical dyes and solutions are a factor that calls autoallergenic reactions by denaturing proteins on the mucous membrane of the skin, respiratory tract. Clinical-experimental tests conducted among workers of a manufacturing enterprise, in which organic and inorganic compounds were applied by several scientists, comprehensively substantiated the negative effects of chemical substances, reagents, catalysts and others on the tissues of the oral cavity and in the whole organism.

In-situ lignin regeneration facilitated corn straw-based photothermal evaporator with high cost-effectiveness

Solar evaporators are one of the most efficient and sustainable water purification strategies, but it requires the use of expensive photothermal materials. Herein, the surface of waste corn straw was modified with condensed lignin by means of in-situ lignin regeneration. The resulting material was composited with hydrophilic chitosan and then applied as a sustainable and cost-effective photothermal material to construct a solar evaporator. The non-radiative transport was conferred by π-π stacking between conjugated aromatic rings of lignin, allowing the composites to demonstrate promising photothermal conversion ability. The composites presented a max evaporation rate of ∼1.44 kg m−2 h−1 under 1 sun, plus they consistently produced clean water in aqueous organic dye solutions (100 ppm RhB dye and 100 ppm MB dye) and seawater. Due to the ultra-low cost of raw materials and uncomplicated manufacturing procedure, these composites displayed a cost-effectiveness of ∼475 g h−1 $−1. Thus, this work provides a green and sustainable method for converting agricultural waste into functional photothermal evaporators, which is meaningful for both materials and environmental science.

Photocatalytic destruction of organic dyes by titanium dioxide particles doped with gold

Nanocomposites based on titanium dioxide doped with gold in concentrations of 0.2 and 0.8 wt.% were obtained by the sol-gel method using titanium tetraisopropoxide and chlorauric acid. Thermal treatment of precipitates at T = 600 °C led to the formation of highly dispersed anatase powders and increasing the temperature to 1000-1200 °C contributed to the formation of well-crystallized rutile particles. The gold in the structure of the powders is heterogeneously distributed. The size of the primary particles of anatase did not exceed 10 nm, and that of rutile reached 35-46 nm, gradually increasing with increasing processing temperature. The photocatalytic properties of TiO2&Au structures were studied during the decolorization of solutions of organic dyes (Methylene Blue, Rhodamine B, Methyl Orange, Orange G) with a concentration of 20 mg/dm3. The resulting structures did not show significant sorption activity, and visible light caused a slight desorption of the dyes. At the same time, under the influence of UV irradiation for 60 minutes, the decolorization process took place effectively and was subject to a pseudo-first-order reaction. The biggest photocatalytic activity was shown by the sample of anatase with a gold content of 0.8 wt.%. When it was added into the solution, the degree of decolorization of Rhodamine B reached up to 50%, Methyl Orange - up to 81.5%, Methylene Blue - up to 91%, and Orange G - up to 95.2%. Increasing the efficiency of the destruction of dyes can be achieved by supplementing the photo-catalytic process with a catalytic one.
 
 Аcknowledgements : Olena Lavrynenko is supported by the PAUSE program, a national emergency program for scientists and artists in exile, run by the Collège de France

Fundamental Understanding of Dye Coverage and Performance in Dye-Sensitized Solar Cells Using Copper Electrolyte

Dyes have played a pivotal role in the advancement of modern dye-sensitized solar cells (DSCs), as they not only facilitate light harvesting, but also serve as blocking layers to impede recombination. In this study, we conducted a systematic investigation to elucidate the influence of dye coverage on the photovoltaic parameters of copper-electrolyte-based DSCs by precisely controlling the dye coverage on the TiO2 substrate using D35 organic dye solutions with varying concentrations. The dye loading increased proportionally with the increase in dye concentrations until it reached saturation at a concentration of 0.2 mM. However, an optimal dye concentration of 0.1 mM was determined in terms of achieving the highest photovoltaic performance, under both outdoor and indoor light conditions. Notably, a maximum power conversion efficiency (PCE) of 6.50 ± 0.25% under outdoor illumination (100 mW/cm2) and 10.48 ± 0.30% under indoor light (1000 lux, WW CFL) was attained using a 0.1 mM D35 dye concentration. Additionally, the dark current and ideality factor (m) were found to be minimized at the 0.1 mM dye concentration. Furthermore, the ideality factor (m) exhibited disparities between indoor and outdoor light conditions. The lifetime obtained from electrochemical impedance spectroscopy (EIS) measurements correlated well with the ideality factor (m) and dark current. Notably, electron injection, dye regeneration, charge collection, and ion diffusion were observed to be independent of the dye coverage.

Organic solvent-free fabrication of thin film polyamide/zeolitic imidazolate framework membranes for removal of dyes from water

Thin film composite (TFC) polyamide (PA) membranes in combination with zeolitic imidazolate frameworks (ZIF), such as ZIF-8 and ZIF-93, have been fabricated using a novel approach based on vapor phase interfacial polymerization (VIP). These membranes have been investigated for nanofiltration (NF) of aqueous solutions of organic dyes, such as Rose Bengal (RB, 1017 Da), Sunset Yellow (SY, 452 Da) and Acridine Orange (AO, 265 Da). The preparation of the PA layer by VIP technique avoids the use of any organic solvent that is typically required in the conventional PA synthesis. Both ZIF-8 and ZIF-93 were initially synthesized using conventional procedures (methanol-based route) and incorporated to the PA layer in two different configurations: i) thin film nanocomposite with ZIF embedded within the PA film, and ii) bilayer membranes with a layer of ZIF between the support and the PA layer. The synthesis of ZIF-93 using a water-based route was developed for the bilayer configuration allowing for an organic solvent-free fabrication of PA/ZIF-93 bilayer VIP-TFC. These membranes showed the highest water permeances of 2.6, 3.4 and 2.2 L m-2h−1 bar−1 for RB, SY and AO, respectively. As compared to the control membrane VIP-TFC, this represents permeance increases of 69–117% and maintains high (greater than 99%) rejection of all the organic dyes. Membrane characterization demonstrated that the permeance enhancement for bilayer PA/ZIF-93 VIP-TFCs is related to an improved hydrophilicity, higher surface roughness and thinner selective layers. The prepared membranes demonstrated excellent cycle stability, maintaining their initial water permeance and dye rejection throughout 34 h of long-term operation, and being able to operate across the entire pH range studied (pH 3 to 9) without any detrimental effects on performance.

Sustainable production of clean water: 1 T-MoS2/PDA composite enhanced the photothermal conversion

The scarcity of fresh water resources necessitates us to develop an efficient technique for sustainable production of clean water from seawater and wastewater. Here, we constructed the 1 T-MoS2/PDA (polyaniline) as a photothermal material for purification of seawater and wastewater to produce clean water through interfacial evaporation by virtue of sunlight. 1 T-MoS2 has a higher evaporation capacity of water than 2 H-MoS2, which was selected to prepare 1 T-MoS2/PDA composite for photothermal conversion. As expected, 1 T-MoS2/PDA composite offers a higher evaporation rate of water than both 1 T-MoS2 and PDA, which owes to an excellent light absorbance, low light reflectance and good wettability. Under irradiation of 1 sun, the evaporation rate of water over the 1 T-MoS2/PDA composite in pure water reached 1.51 kg m−2h−1, and the photothermal conversion efficiency reached 92%. Encouragingly, 1 T-MoS2/PDA composite can be well used to treat real seawater and various wastewater such as organic dye solution and heavy metal ion solution, in which the evaporation rate of water is close to pure water, and the quality of water is better than the standard of drinking water established by the World Health Organization (WHO). Besides, 1 T-MoS2/PDA composite still maintain an excellent evaporation performance after treatment of acidic solution and alkaline solution, indicating an excellent durability. This work provides a feasible solution for producing clean water by solar-driven interfacial evaporation from seawater and wastewater.

Solar photoelectro-Fenton: A very effective and cost-efficient electrochemical advanced oxidation process for the removal of organic pollutants from synthetic and real wastewaters

Recalcitrant and toxic organic pollutants from wastewaters are scarcely removed in conventional wastewater treatment plants. To preserve the water quality, organics need to be removed by developing powerful oxidation technologies. Our laboratory proposed in 2007 a potent electrochemical advanced oxidation process (EAOP) for wastewater remediation, so-called solar photoelectro-Fenton (SPEF). This review summarizes the advances of this emerging technology up to 2022, making evident its effectiveness and cost-efficiency for the destruction of usual organic pollutants. The simultaneous action of generated hydroxyl radicals and the photolysis by sunlight explains the high oxidation power of SPEF respect to other EAOPs. The review is initiated by describing the fundamentals of the process to remark the role of the produced oxidants and the benefits of using solar irradiation in its performance. The photoelectrochemical systems used (bench tank reactor and solar pre-pilot flow plant) and the assessment of the operating variables are discussed. The characteristics of the most common homogeneous SPEF for the degradation and mineralization of several synthetic solutions of industrial chemicals, herbicides, pharmaceuticals, and synthetic organic dyes, as well as of some real wastewaters, are further described. The influence of the photoelectrochemical cell, electrodes, solution pH, electrolyte composition, Fe2+ and pollutant concentration, and current density is analyzed. The performance of a homogeneous SPEF-like process with active chlorine and heterogeneous SPEF processes with solid catalysts such as Fe3O4 and sodium vermiculite is also discussed. Finally, the advances of homogeneous SPEF combined with other techniques like solar photocatalysis, solar photoelectrocatalysis, anaerobic digestion, and nanofiltration are reported.

In Situ Growth and UV Photocatalytic Effect of ZnO Nanostructures on a Zn Plate Immersed in Methylene Blue

Nanostructures of zinc oxide (ZnO) are considered promising photocatalysts for the degradation of organic pollutants in water. This work discusses an in situ growth and UV photocatalytic effect of ZnO nanostructures on a Zn plate immersed in methylene blue (MB) at room temperature. First, the Zn surfaces were pretreated via sandblasting to introduce a micro-scale roughness. Then, the Zn plates were immersed in MB and exposed to UV light, to observe ZnO nanostructure growth and photocatalytic degradation of MB. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectroscopy were used to characterize the Zn surfaces. We observed the growth of stoichiometric and crystalline ZnO with a nano-leaf morphology and an estimated bandgap of 3.08 eV. The photocatalytic degradation of MB was also observed in the presence of the ZnO nanostructures and UV light. The average percentage degradation was 76% in 4 h, and the degradation rate constant was 0.3535 h−1. The experimental results suggest that room temperature growth of ZnO nanostructures (on Zn surfaces) in organic dye solutions is possible. Furthermore, the nanostructured surface can be used simultaneously for the photocatalytic degradation of the organic dye.

Efficiency of adding DD3+(Li/Mg) composite to plants and their fibers during the process of filtering solutions of toxic organic dyes

A comparison was made between two types of plants, cauliflower and Anisosciadium, to find out which one is better and to address the main catalyst and the factors that achieve the white color of the solution in the filtering process. Where this process takes place under the sun's rays. We worked on two methods, the first is to use a portion of cauliflower leaves and peas stalks, and the second is to extract the fibers that make up the two aforementioned materials and work on them. To improve the process of filtration and photocatalysis together, we used a new method that gives excellent efficacy in just minutes, by depositing (Li/Mg) materials on one side, and on the other hand depositing (Li/Mg)+kaolinite type DD3 on these plants without heat treatment.This process preserves the shape of the fibers, leaves or leg, according to the types used, without being damaged. The results showed effectiveness in filtering both polluting solutions without discrimination, but the fastest degradation time was by using the fibers of both plants with precipitants (Li/Mg + DD3) in the case of solutions with organic dye MB, where we obtained a percentage of 100 within 60 mn. Compared with the OII, where is the estimated time to get the full liquidation 120 mn. The samples were studied before and after the filtration process by infrared to confirm the presence of impurities belonging to the two highly toxic organic solutions, and also the obtained solution was analyzed after the operation and it was found that it matches the spectrum of distilled water.

In-situ enhanced laser absorption in aqueous transition metal salt solution enables high-quality backside wet etching of optical glass by near-infrared lasers

A laser-induced backside wet etching technique using near-infrared laser sources (N-LIBWE) has been proposed for high-quality micromachining of optical glass. Compared with conventional LIBWE using organic dye solutions with high absorption coefficients (∼104–105 cm−1) as the liquid absorbent, the transition metal salt solution used in N-LIBWE shows the absorption coefficient of only 10-1-101 cm−1. Moreover, as we proved in this study, the etching rate of N-LIBWE is independent of the absorptivity of the liquid absorbent. How the etching occurs during N-LIBWE is still controversial. Herein, interface images with a temporal resolution of 4 ns after the start of laser irradiation are captured by a stroboscopic shadowgraphy system. Afterward, the density, pressure, and temperature distribution in the solution are calculated by a physics-based two-dimensional hydrodynamic model to explain the observed interface images. We prove that the localized laser absorption is enhanced with laser irradiation because of the in-situ formation of solid substances. It is the properties of the formed solid products instead of the normal absorption coefficient of the solution that determines the final interface status. We further prove that the formed solid substances in aqueous CuSO4 solutions are primarily amorphous nanoclusters, which benefit the enhancement of laser absorption and tend to attach to the transparent substrates, resulting in the incubation effect in N-LIBWE. Our results provide systematic mechanisms explaining the N-LIBWE process, which also benefit the deep understanding of other liquid-assisted laser materials processing technologies.

Citric-Acid-Assisted Preparation of Biochar Loaded with Copper/Nickel Bimetallic Nanoparticles for Dye Degradation

Immobilization of nanocatalysts on biochar is receiving unprecedented interest among material and catalysis scientists due to its simplicity, versatility, and high efficiency. Herein, we propose a new direct approach to obtain bimetallic copper/nickel nanoparticles loaded on olive stone biochar. The bimetallic-coated biochar and the reference materials, namely bare biochar, copper rich-loaded biochar, and nickel-loaded biochar, were prepared by pyrolysis from olive pit powder particles impregnated first with citric acid (CA) and then with copper and nickel nitrates at 400 °C under nitrogen flow. We employed citric acid in the process in order to examine its effect on the structural and textural properties of biochar supporting the metallic nanoparticles. Surprisingly, citric acid induced the formation of agglomerated or even raspberry-shaped bimetallic copper/nickel nanoparticles. Large 450–500 nm agglomerates of ~80 nm bimetallic CuNi NPs were noted for B-CA@CuNi. Interestingly, for biochar material prepared with initial Cu/Ni = 10 molar ratio (B-CA@CuNi10/1), the bimetallic NPs formed unusual nanoraspberries (174 ± 8 nm in size), which were agglomerates of individual 10–20 nm CuNi10/1 nanoparticles. The B-CA@CuNi and reference materials were characterized by Raman spectroscopy, scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and magnetometry. The B-CA@CuNi and B-CA@Ni materials could be efficiently attracted with a magnet but not B-CA@CuNi10/1 due to the low nickel loading. B-CA@CuNi was tested as a catalyst for the degradation of methyl orange (MO). Discoloration was noted within 10 min, much faster than a similar material prepared in the absence of CA. B-CA@CuNi could be recycled at least 3 times while still exhibiting the same fast catalytic discoloration performance. This paper stresses the important role of citric acid in shaping bimetallic nanoparticles loaded in situ on biochar during the slow pyrolysis process and in enabling faster catalytic discoloration of organic dye solution.

Investigation of Interaction Mechanisms of High Energy Electrons and Gamma Quantum with Aqueous Solution of Methyl Orange Dye

The level of development of modern nuclear technologies forms a request for the development of new branches of science. At the same time, chemical dosimetry methods are also being improved [1, 2]. The essence of such methods consists in the quantitative determination of the radiation-chemical damages to the molecules of a substance when it is exposed to ionizing radiation [3, 4]. Liquid and solid solutions of organic dyes have intense bands optical absorption and fluorescence in the visible region of the spectrum, which makes it possible to use them in dosimetry systems [5, 6]. The use of organic dyes makes it possible to determine the absorbed dose in the range from 10-6 to 104 M Rad [7, 8]. In this work, we studied the processes of interaction of gamma-ray and high-energy electron fluxes with an aqueous solution of the organic dye methyl orange (C14H14N3О3SNa) [9, 10]. The calculations and experiment were carried out on a resonant electron accelerator with energies up to 30 MeV. The electron beam energy was 15 MeV. A tungsten converter was used to generate gamma quanta. The thickness of the converter varied from 0 to 6 mm. We have developed a computer program in C++ to simulate the irradiation process. This program uses the Geant4 class library based on the Monte Carlo method and runs in multi-threaded mode. For calculations, the model “PhysicsList emstandard_opt3” was chosen as the most suitable one. The value of radiation damage per one incident electron and produced gamma-quantum is determined in the work. The simulation results are compared with experimental data. Based on the results obtained, conclusions were drawn about the main mechanisms leading to the decomposition of organic dye molecules, and methods for optimizing the experiment for further research were proposed.

Direct and Indirect Treatment of Organic Dye (Acid Blue 25) Solutions by Using Cold Atmospheric Plasma Jet

In this work, the direct and indirect removal of Acid Blue 25 (AB25) from water by using cold atmospheric pressure plasma jet (APPJ) has been demonstrated. APPJ with a pin electrode type configuration operating with argon as a working gas was used as a plasma source for treatments. In this configuration, argon plasma was formed in the contact with surrounding air over the liquid surface. The plasma was driven by using a high voltage radio frequency (RF) power supply. The system was characterized by the measurement of electrical characteristics and by employing optical emission spectroscopy (OES). The electrical characterization gave information about the voltages and currents, i.e., working points of the discharge, as well as power deposition to the sample. OES recorded the emission spectra and confirmed several existing reactive species in the gas phase of the plasma system. During the direct treatment, AB25-containing solution was directly exposed to APPJ. The direct treatment was performed by modifying various experimental parameters, such as initial AB25 concentrations, treatment times, and input powers. In the indirect treatment, AB25 was treated by using plasma activated water (PAW). The characterization of PAW was performed and various plasma-induced long-lived species, such as nitrate (NO3−), nitrite (NO2−) and hydrogen peroxide (H2O2) have been quantified using colorimetric techniques. Besides, blank experiments have been conducted with main constituents in PAW, where AB25 was treated individually by NO3−, NO2−, and H2O2 and with a mixture of these three species. As expected, with the direct treatment almost complete removal of AB25 was achieved. The measurements also provided an insight into the kinetics of the degradation of AB25. In the indirect treatment, PAW removed a significant amount of AB25 within 17 days. In the blank experiments, H2O2 containing solutions created a favourable influence on removal of AB25 from liquid.

Separation of textile wastewater using a highly permeable resveratrol-based loose nanofiltration membrane with excellent anti-fouling performance

A precise separation of organic dyes and inorganic salts is a prerequisite for zero liquid discharge of saline textile wastewater. The development of loose nanofiltration (LNF) membranes with customized nanoscale pores and high water permeance is expected to address this challenge. Herein, a new LNF membrane is reported, fabricated via a scalable interfacial polymerization (IP) approach between resveratrol and trimesoyl chloride (TMC) on a Kevlar substrate. The optimal resveratrol/TMC membrane exhibited an ultra-high pure water permeance (121.1 L−1 m−2h−1 bar−1), high dye rejection (99.4% for 200 ppm of Congo Red), and low salt rejection (4.2% for NaCl and 9.8% for Na2SO4). The chemical compositions, surface properties, and morphologies of the LNF membranes were characterized to elucidate their structure–property-performance relationships. The homogeneous diffusion of resveratrol to the water/hexane interface and the appropriate stoichiometry of the two monomers contribute to the formation of an ultra-thin (35–45 nm) and hydrophilic composite membrane, which allows the membrane to attain a high water permeance. The LNF membrane additionally maintains excellent anti-fouling properties during filtration of organic dye solutions, primarily as a result of the high hydrophilicity, negative charge density, and smoothness of the membrane surface. Importantly, the novel LNF membrane also retains stability after washing with ethanol and acetone, owing to the cross-linked polyphenol ester and the rigid phenyl backbone of the membrane surface. These results reveal the huge potential of applying resveratrol-based LNF membranes for the treatment of saline textile wastewater.

GEANT4 Modeling of the Bremsstrahlung Converter Optimal Thickness for Studying the Radiation Damage Processes in Organic Dyes Solutions

The study of the processes occurring in a matter when ionizing radiation passes through is important for solving various problems. Examples of such problems are applied and fundamental problems in the field of radiation physics, chemistry, biology, medicine and dosimetry. This work is dedicated to computer modeling of the parameters of a tungsten converter for studying the processes of radiation damage during the interaction of ionizing radiation with solutions of organic dyes. Simulation was carried out in order to determine the optimal thickness of the converter under predetermined experimental conditions. Experimental conditions include: energies and type of primary particles, radiation intensity, target dimensions, relative position of the radiation source and target. Experimental studies of the processes of radiation damage occurring in solutions of organic dyes are planned to be carried out using the linear electron accelerator "LINAC-300" of the National Scientific Center "Kharkov Institute of Physics and Technology". Electrons with 15 MeV energy are chosen as primary particles. The interaction of electrons with the irradiated target substances is planned to be studied in the first series of experiments. Investigations of the interaction of gamma quanta with the target matter will be carried out in the second series of experiments. The tungsten converter is used to generate a flux of bremsstrahlung gamma rays. One modeling problem is determination of the converter thickness at which the flux of bremsstrahlung gamma will be maximal in front of the target. At the same time, the flow of electrons and positrons in front of the target should be as low as possible. Another important task of the work is to identify the possibility of determining the relative amount of radiation damage in the target material by the Geant4-modeling method. Radiation damage of the target substance can occur due to the effect of bremsstrahlung, as well as electrons and positrons. Computational experiments were carried out for various values of the converter thickness – from 0 mm (no converter) to 8 mm with a step of 1 mm. A detailed analysis of the obtained data has been performed. As a result of the data analysis, the optimal value of the tungsten converter thickness was obtained. The bremsstrahlung flux in front of the target is maximum at a converter thickness of 2 mm. But at the same time, the flux of electrons and positrons crossing the boundaries of the target does not significantly affect the target. The computational experiment was carried out by the Monte Carlo method. A computer program in C++ that uses the Geant4 toolkit was developed to perform calculations. The developed program operates in a multithreaded mode. The multithreaded mode is necessary to reduce the computation time when using a large number of primary electrons. The G4EmStandardPhysics_option3 model of the PhysicsList was used in the calculations. The calculations necessary for solving the problem were carried out using the educational computing cluster of the Department of Physics and Technology of V.N. Karazin Kharkiv National University.

Research of Interaction Processes of Fast and Thermal Neutrons with Solution of Organic Dye Methyl Orange

The emergence of powerful sources of ionizing radiation, the needs of nuclear energy, technology and medicine, as well as the need to develop reliable methods of protection against the harmful effects of penetrating radiation stimulated the development of such branches of science as radiation chemistry, radiation biology, radiation medicine. When an organic dye solution is exposed to ionizing radiation, it irreversibly changes color. As a result, the absorbed dose can be determined. The processes of interaction of neutron fluxes with an aqueous solution of an organic dye methyl orange (МО) – C14H14N3О3SNa, containing and not containing 4% boric acid, have been investigated. The work was carried out on a LINAC LUE-300 at NSC KIPT. A set of tungsten plates was used as a neutron-generating target. The electron energy was 15 MeV, the average current was 20 μA. The samples were located behind the lead shield and without it, with and without a moderator. Using the GEANT4 toolkit code for this experiment, neutron fluxes and their energy spectra were calculated at the location of experimental samples without a moderator and with a moderator of different thickness (1-5 cm). An analysis of the experimental results showed that when objects without lead shielding and without a moderator are irradiated, the dye molecules are completely destroyed. In the presence of lead protection, 10% destruction of the dye molecules was observed. When a five-centimeter polyethylene moderator was installed behind the lead shield, the destruction of dye molecules without boric acid on thermal neutrons was practically not observed. When the fluxes of thermal and epithermal neutrons interacted with a dye solution containing 4% boric acid, 30% destruction of dye molecules was observed due to the exothermic reaction 10B (n, α). The research has shown that solutions of organic dyes are a good material for creating detectors for recording fluxes of thermal and epithermal neutrons. Such detectors can be used for radioecological monitoring of the environment, in nuclear power engineering and nuclear medicine, and in the field of neutron capture therapy research in particular.

Impact of silver nanoparticle two-photon resonance on Kerr effect of organic dye solutions

In this work, we studied the spectral dispersion of two-photon absorption (2PA) and the Kerr effect of core-shell silver nanoparticles (NPs) with thiol-termination ligand cladding in a dichloromethane (DCM) solution and their influence on the nonlinear optical response of 2-[4-(N,N-dimethylamino)-benzylidene]-indane-1,3-dione (DMABI) molecules. To study the spectral dispersion of nonlinear optical properties, we used the Z-scan method with a tunable picosecond (ps) laser with a 27.5 ps pulse duration and 1000 Hz pulse repetition rate. Measurements were carried out in a spectral range between 600 nm and 1100 nm. Four types of samples were studied: pure DCM solvent, NPs dispersed in DCM, a DMABI solution in DCM, and a DMABI/NP mixture in DCM. NP size distribution measurements showed two NP groups with average sizes of 4 and 40 nm. NPs exhibited a strong 2PA in a range of 710–900 nm. Nonlinear optical measurements of DMABI showed that the presence of NPs did not influence the 2PA of DMABI. When comparing the nonlinear refractive index values of DMABI in cases with and without NPs, a difference in signals was observed that correlated with the 2PA of NPs. Polarization-resolved Z-scan measurements showed that the reorientation contribution of the Kerr effect changed due to the presence of NPs.

Facile fabrication of novel Ag2S-ZnO/GO nanocomposite with its enhanced photocatalytic and biological applications

Progression in nanotechnology enormously influence on the synthesis of highly proficient photo materials, which can be used for a number of applications in diverse fields. Herein, a novel heterostructured Ag2S-ZnO/GO nanocomposite was fabricated via a simple sol-gel/ultrasound method and was used to study photocatalytic degradation of organic dye solution under UV/visible light irradiation. The physicochemical characteristics of prepared nanocomposite signify that it exhibits remarkable morphology, high surface area and homogenized particle distribution. The average crystallite size of ZnO, Ag2S-ZnO and Ag2S-ZnO/GO was calculated to be 21.2, 24.5 and 26.4 nm, respectively. Prepared nanocomposite are found to be exceptionally efficient for photocatalytic degradation of methyl orange (MO) as compared to other materials. The photodegradation of MO was achieved up to 98.1% under UV and 66.8% under visible light irradiation within 50 min. However, the characteristic features of graphene including storage and transferring of electrons and establishment of heterojunction between Ag2S and ZnO are responsible for enhanced efficiency towards separation of photoinduced electron/hole pairs as well as increased charge transferring due to lowering of bandgap. More importantly, the Ag2S-ZnO/GO nanocomposite displays superior antibacterial, antifungal and antioxidant activities. The further investigations of antibacterial and antifungal properties of as-synthesized nanocomposite revealed that by adding Ag2S-ZnO/GO to bacterial and fungal media, a clear zone of inhibition for both bacteria and fungi medium was observed. It can be concluded from the results that Ag2S-ZnO/GO nanocomposite having remarkable structure reliability are excellent candidate for both photocatalytic and biomedical applications. Moreover, the possible degradation mechanism of photocatalyst was also predicted.

Photocatalytic Decomposition of Organic Dyes Using a Rotating Cylinder System.

In this study, a rotating cylinder system was used in the photocatalytic decomposition of organic dyes in aqueous medium for water purification. To this end, the titania nanoparticle dispersion was mixed with an organic dye solution under a rotating inner cylinder at controlled speed. The rate constant was adjusted by changing the speed of rotation to determine the optimal circulating velocity. Since nanoparticle dispersion is a secondary contaminant after wastewater treatment, the titania paste was deposited on the inner surface of the stationary outer cylinder to form a photocatalytic film. During repeated batch-mode operation, the deactivation of the deposited film was analyzed by measuring the rate constant as a function of time. Continuous operation was also used to remove organic dye in the water to study factors affecting the removal efficiency of methylene blue. Higher rotating velocity and slow feed rate facilitated the removal of contaminants via desorption of adsorbed dyes with adequate retention time.