Absorption Spectra Of Solutions Research Articles

Influence of symmetry breaking on the absorption spectrum of crystal violet: from isolated cations at 5 K to room temperature solutions.

We report the resolution of a long-standing puzzle in molecular spectroscopy: the origin of the shoulder in the room temperature solution absorption spectrum of crystal violet (CV) - an archetypal cationic triphenylmethane dye. This was achieved by comparing experimental and theoretical results for CV in solution at room temperature and as an isolated cation in gas-phase at 5 K. The two lowest energy electronically excited states involved in the visible region absorption are degenerate and coupled via a Jahn-Teller (JT) mechanism involving phenyl torsions, making CV particularly sensitive to environmental perturbations. The shoulder is absent in the low-temperature isolated cation spectrum, and vibronic simulations based on time dependent density functional theory (TD-DFT) indicate negligible JT effects under these conditions. Combining vibronic simulations with molecular dynamics, demonstrates that in water and toluene solution at room temperature the shoulder arises mainly from an intermolecular, Jahn-Teller-like symmetry-breaking effect induced by the fluctuating electrostatic potential of the disordered solvent environment, rather than from molecular distortions.

Colorimetric detection of pyrophosphate using gold nanorods and Fe3+ based on anti-etching mechanism

Pyrophosphate (PPi), as a derivative of inorganic phosphate, has important applications in the fields of food and environment, it also plays an important role in biological metabolism and serves as a biomarker for clinical diagnosis of certain diseases. Thus, the development of a simple and convenient method to quantify PPi is of great significance for environmental protection, food safety and disease diagnosis. In this study, visual colorimetric detection of PPi was achieved by inhibiting the morphological change of gold nanorods (Au NRs). In the presence of SCN-, Fe3+ with low concentration can oxidatively etch Au NRs due to the potential difference, leading to significant color change of Au NRs solutions and blue shift in longitudinal local surface plasmon resonance (LSPR) absorption peak of Au NRs solutions. Due to the strong complexation between PPi and Fe3+, the etching of Au NRs by Fe3+ was restrained, while the morphology of Au NRs, the color and UV–vis absorption spectrum of Au NRs solution remained uninfluenced. Under optimal conditions, this colorimetric detection method exhibited exceptional selectivity, anti-interference, and sensitivity towards PPi, with a linear detection range of 0.8–24 μM. Moreover, practical application results suggest that this colorimetric method holds significant potential for swiftly detecting PPi in intricate samples.

Reactive Dyes Bearing Bis(Monochlorotriazine) Group: Synthesis, Photophysical Properties and Realization of Salt‐Free Dyeing

AbstractA series of novel reactive dyes D1–D3 based on vinamidinium salt were designed and synthesized. Bis(monochlorotriazine) was introduced as the reactive group and sodium sulfonate was the water‐soluble group. Their photophysical properties were studied systematacially. The strong and sharp ground‐state absorption peak in the 250–320 nm range in the UV‐vis absorption spectrum of the aqueous solution could be attributed to the 1π–π* transition by the parent structure of the dyes, and the relatively broad absorption peak in the range of 300–650 nm could be attributed to the 1π–π* mixed intramolecular charge transfer. By applying this series of reactive dyes to the dyeing of four fabrics (silk, cotton, polyester/cotton blends, and polyester), the dyeing depths were in the range of 5.2–28.6 under salt‐free conditions. The results show that D3 with higher planarity can increase the dyeing depth. At length, fastening tests on dyed cotton fabrics and silk showed that this series of reactive dyes had a color fastness between grades 3 and 5 for abrasion and soap‐washing. In summary, these reactive dyes could be potential dyes for salt‐free dyeing applications.

Saturated Red Electrophosphorescence From Novel Pyridinopyridazine‐Based Iridium Complexes

ABSTRACTTwo isomeric homoleptic Ir(III) complexes with pyridinopyridazine derivative ligands were prepared first. Due to its stronger intramolecular hydrogen bonding and intermolecular interactions, complex IrPPM has a higher decomposition temperature (5% weight loss) of 387°C than IrPPP (354°C). They have similar UV–Vis absorption and photoluminescence spectra in CH2Cl2 solution with photoluminescence peaks around 635–636 nm. However, the emission peak of IrPPM in neat powder obviously red‐shifted to 652 nm, and that of IrPPP blue‐shifted to 626 nm. Simultaneously, complex IrPPM has a lower photoluminescence quantum yield of 0.3 than IrPPP (0.5). Efficient saturated red OLED devices are developed with Commission Internationale de L'Eclairage color coordinates of (0.67, 0.32) and (0.66, 0.32), respectively. The maximum external quantum efficiencies of both devices exceed 11%. These results demonstrate the great potential of pyridinopyridazine derivatives for developing new iridium complexes for OLED applications.

Spectrophotometric-Based Sensor for the Detection of Multiple Fertilizer Solutions

The online detection of fertilizer solution information is a crucial link in the implementation of intelligent and precise variable fertilization techniques. However, achieving simultaneous rapid online detection of multiple fertilizer components is still challenging. Therefore, a rapid detection method based on spectrophotometry for qualitative and quantitative identification of four fertilizers (typical N, P, and K fertilizers: KNO3, (NH4)2SO4, KH2PO4, and K2SO4) was proposed in this work. Full-scan absorption spectra of fertilizer solutions at varying concentrations were obtained using a UV–visible/near-infrared spectrophotometer. By assessing the linear fit between fertilizer concentration and absorbance at each wavelength within the characteristic band, the characteristic wavelengths for KNO3, (NH4)2SO4, KH2PO4, and K2SO4 were identified as 214 nm, 410 nm, 712 nm, and 1708 nm, respectively. The identification method of fertilizer type and the prediction model of concentration were constructed based on characteristic wavelength and the Lambert–Beer law. Based on the above analysis, a four-channel photoelectric sensor was designed with four LEDs emitting wavelengths closely matched to characteristic wavelengths for fertilizer detection. A detection strategy of “qualitative analysis followed by quantitative detection” was proposed to realize the online detection of four fertilizer types and their concentrations. Evaluation of the sensor’s performance showed its high stability, with an accuracy of 81.5% in recognizing fertilizer types. Furthermore, the relative error of the sensor detection was substantially less than ±15% for the fertilizer concentrations not exceeding 80 mg/L. These results confirm the capability of the sensor to meet the practical requirements for online detection of four fertilizer types and concentrations in the field of agricultural engineering.

Coomassie Brilliant Blue G for Smart Colorimetric Determination of the Ionic Surfactants in Triton X-100 Solutions.

The conditions for the smart colorimetric determination of cetylpyridinium chloride and sodium dodecyl sulfate by reaction with Coomassie brilliant blue G (CBBG) have been proposed. The nature of the absorption and fluorescence spectra of aqueous solutions of CBBG as a function of acidity has been investigated. A variety of reagent forms and associations with ionic surfactants have been demonstrated. The composition of the associates formed in the CBBG-cationic surfactant system has been established. The increase in the analytical signal of the cationic surfactant and the stabilization of the colloid-chemical state of the system during reactions in the organized medium of the nonionic surfactant Triton X-100 has been demonstrated. These effects are realized through association in premicellar solutions and as a result of the solubilization of components in Triton X-100 micellar solutions. The addition of long-chain cationic surfactants to the reagent occurs with the replacement of the heteroatom proton. The absorption of CBBG-cationic surfactant associates solutions increases with the length of the cationic surfactant hydrocarbon chain. Ethanol additives decrease the aggregation of CBBG. The technique of cationic surfactant determination has been tested in the analysis of the pharmaceutical. The results show that the simplicity of analytical signal registration with satisfactory correctness and acceptably high sensitivity of determination is an advantage of the developed technique.

Solvent Effect for the Structural Control of Molecular Architectures Consisting of Trinuclear Ruthenium Clusters and Ligands at the HOPG Surface.

The molecular architecture of a triruthenium complex and 1,4-di(4-pyridyl)benzene on highly oriented pyrolytic graphite was investigated by drop-casting mixed tetrahydrofuran and methanol solutions. Atomic force microscopy revealed the formation of one-dimensional molecular wires on highly oriented pyrolytic graphite after heating the mixed tetrahydrofuran solution, whereas large ring structures were formed in the methanolic solution. It was found that the molecular architectures composed of triruthenium complexes and 1,4-di(4-pyridyl)benzene strongly depend not only on the temperature of the solution but also on the organic solvents. The formation of the molecular architecture was supported by the ultraviolet-visible absorption spectra of the mixed solution and the electrochemical responses of the deposited film.

Preparation of copper glycinate and study of its effect on the germination of winter barley seeds

We analyzed the encrustation of winter barley seeds, which includes its preliminary treatment with cuprum glycinate, with the purpose of increasing yield and biochemical indicators of grain, and also improving the ecological condition of the soil. The objective of the research was to select methods for the synthesis of cuprum glycinate, study its chemical composition and the possibility of using this compound as a chelated micro-fertilizer for pre-sowing encrustation of winter barley seed as part of a tank mixture. Two well-known synthesis methods were used to obtain cuprum glycinate. The first method was the interaction between CuO with a solution of glycine during heating, during which pink metallic copper inclusions were noticed in the mixture of reaction products. It was found that it is expedient to synthesize the glycine complex of cuprum by the reaction of a suspension of Cu2CO3(OH)2 with glycine during heating (the yield is 97%), since a complex compound Cu(NH2CH2COO)2•H2O of sufficient purity is formed. The composition of the synthesized substance and the confirmation of the formula of the compound Cu(NH2CH2COO)2•H2O were obtained by determining the infrared and the atomic absorption spectrum of the aqueous solution. Based on the obtained differences in the atomic absorption spectra of the synthesized copper sulfate and copper glycinate the formation of the latter was confirmed. The IR spectrum confirms the formula of the complex compound and the formation of strong covalent bonds between the metal cation and the ligands. The study of the effect of cuprum glycinate on the germination of winter barley Tutankhamun seeds was carried out in comparison with the similar effect of a complex compound of cuprum with ethylenediaminetetraacetate. The study of the influence of cuprum glycinate on the germination of winter barley revealed positive results in which the germination exceeded the control by 9–27%. Winter barley seeds treated with distilled water served as a control. Treatment of winter barley seeds with an aqueous solution of cuprum glycinate in the amount of 20 g of cuprum per 1 ton of grain led to better germination than pre-treatment of seeds with a twice concentrated corresponding solution. Treatment with a complex compound of copper with ethylenediaminetetraacetate had no significant effect on the germination and characteristics of sprouts. The results of laboratory studies confirmed the feasibility of using complex compounds of biometal copper with organic chelating ligands as microfertilizers for pre-sowing seed encrustation, as they have high stability and sufficient solubility in water, are non-toxic, are better absorbed by plants and are considered cost-effective and environmentally safe.

A Single-Shot Technique for Measuring Broadband Two-Photon Absorption Spectra in Solution.

Applications involving two-photon activation, including two-photon fluorescence imaging, photodynamic therapy, and 3D data storage, require precise knowledge of the two-photon absorption (2PA) spectra of target chromophores. Broadband pump-probe spectroscopy using femtosecond laser pulses provides wavelength-dependent 2PA spectra with absolute cross sections, but the measurements are sometimes complicated by cross-phase modulation effects and dispersion of the broadband probe. Here, we introduce a single-shot approach that eliminates artifacts from cross-phase modulation and enables more rapid measurements by avoiding the need to scan the time delay between the pump and the probe pulses. The approach uses counterpropagating beams to automatically integrate over the full interaction between the two pulses as they cross. We demonstrate this single-shot approach for a common 2PA reference, coumarin 153 (C153), in three different solvents using the output from a Yb:KGW laser. This approach provides accurate 2PA cross sections that are more reliable and easier to obtain compared with scanning pump-probe methods using copropagating laser beams. The single-shot method for broadband two-photon absorption (BB-2PA) spectroscopy also has significant advantages compared with single-wavelength measurements, such as z-scan and two-photon fluorescence.

Control under optical, nonlinear optical and kinetic properties of two-dimensional gradient CdSe1-xSx nanocrystals

Peculiarities of photoluminescence (PL) and absorption spectra of gradient nanocrystals CdSe1-xSx colloidal solution were studied by pump and probe technique under stationary excitation of excitons by nanosecond laser pulses. The PL peaks and differential transmission peaks positions changing were revealed with the CdSe1-xSx nanocrystals composition variation. Bleaching of excitons transitions was observed for high pump intensities and explained by excitons space filling effect. The changing of the differential transmission peaks positions was explained by the nanocrystal band gap dependence on the chemical composition. Time-resolved PL measurements from the sub-picoseconds to tens of nanoseconds range demonstrated a strongly different behavior for gradient nanocrystals and pure CdSe nanocrystals. For pure nanocrystals two typical time-scales were resolved contrary to the gradient nanocrystals where (with the growth of sulfur concentration) only a single time scale was revealed. The observed modification of time-resolved PL for gradient nanocrystals is caused by the presence of traps in the gradient samples due to the chemical composition modification.

Determination of N-centered stereochemistry in N22-methylated chlorophyll-a derivatives and their epimer-dependent optical spectra.

An N-centered epimeric mixture of chlorophyll-a derivatives methylated at the inner nitrogen atom was separated by reverse-phase high-performance liquid chromatography. Circular dichroism (CD) spectroscopic analyses of the epimerically pure N22-methyl-chlorins revealed that the minor first-eluted and major second-eluted stereoisomers were (22S)- and (22R)-configurations, respectively. Their visible absorption and CD spectra in solution were dependent on the N22-stereochemistry. The epimer-dependent spectral changes were independent of the substituents at the peripheral 3-position of the core chlorin chromophore.

ABSORPTION AND LUMINESCENCE PROPERTIES OF ACID AND SALT FORMS OF MONONUCLEOTIDES, THEIR COMPONENTS AND COMPLEXES WITH D-MANNITOL AT ROOM TEMPERATURE

Aim. The aim of this work was to analyze and compare spectral properties of aqueous nucleotide solutions in conditions close to biological systems. We studied the absorption and luminescence (Ex and Em fluorescence and Em phosphorescence) of monoribonucleotides, their disodium salts, bases and nucleosides, and mixes with D-mannitol dissolved in water at room temperature. Methods. There were measured absorbance spectra using a Specord 210plus instrument and fluorescence excitation and emission and phosphorescence spectra using Horiba Fluoro Max 4+ instruments. Results. There were obtained the absorption, excitation, and luminescence spectra of aqueous solutions 1 mg/ml of nucleotides, their components, and mixtures with mannitol (in ratio 1:4). We observed a change in the ratio between the peaks of the spectra of acidic and salt forms of nucleotides. Conclusions. The observations confirmed that nucleotides, nucleosides, and nucleic acid bases exhibit luminescence at room temperature, which might be useful information for further research in this area. In addition, a comparative analysis of the spectra showed possible interactions between nucleotide molecules and mannitol.

In English

Changes in the light absorption spectrum when mixing colloids of Ag nanoparticles with a diameter of 7 nm in a quercetin shell with a nutrient medium were studied in the present article. Colloids of silver nanoparticles were prepared by chemical reduction of AgNO3 silver salt with sodium tetrahydroborate (NaBH4) in an aqueous solution. Quercetin is a flavonoid of plant origin. It was chosen to stabilize nanoparticles due to its capability to form complexes with metals. The quercetin shell is capable to preserve the bactericidal effect of silver NPs on bacteria and weaken their toxic effect on healthy cells of the human body. The absorption spectra of solutions from which nanoparticle colloids were synthesized were used to control the synthesis result. The Luria-Bertani nutrient medium was studied in the work. Absorption spectra of the nutrient medium and nanoparticle colloids were again obtained immediately before mixing. Then, the nutrient medium and the nanoparticle colloid were mixed in volume proportion 1:1, and the absorption spectrum of the mixture was mesured. The absorption spectrum of the mixture did not reproduce a simple overlay of the nanoparticle colloid spectrum on the absorption spectrum of the nutrient medium. To describe the experimental spectra, a colloid of stabilized silver nanoparticles, a nutrient medium, and a mixture of a colloid and a nutrient medium were considered by nanocomposites of various organic and inorganic nanoparticles in a liquid. As a result, experimental absorption spectra were theoretically approximated by related to these nanoparticles elementary oscillators. The error of the discrepancy between experimental and simulated spectra did not exceed 3%. Analysis of the complex spectra of the mixture of the nanoparticle colloid and the nutrient medium has shown that the frequency of the localized plasmon resonance in the nanoparticles most likely does not change. It means that for studying the effect of nanoparticles on biological objects (microbes or viruses), the wavelength of external irradiation must be chosen equal to the wavelength of LPR in the colloid.

Excited state dipole moments of two dicyanobenzene isomers from thermochromic shifts and ab initio calculations

The excited state dipole moments of two positional isomers of dicyanobenzene have been determined from thermochromic shifts of the absorption and fluorescence emission spectra in ethyl acetate solution and compared to the results of ab initio calculations. We found that the dipole moments of excited states from thermochromic shifts closely resemble the ab initio values of the isolated molecule, while the results of conductor-like screening model (COSMO) using the same wave function model as for the isolated molecule, shows considerable deviations from the experimental values. It is shown that the dipole moments of the two cyano groups add up vectorially for both the ground and excited states.

New morpholino acetamide ligand's rare earth metal complexes through synthesis, structural, and theoretical studies. Effect of ligand on aluminum alloy corrosion inhibition

A series of new complexes of the general formula [Ln(L)Cl2]Cly·4H2O (Ln = Er and Ta) and [Yb(L)(H2O)2]Cl3, L = N,N'-((ethane-1,2-diylbis(sulfanediyl))bis(2,1-phenylene))bis-(2-morpholino-acetamide) were synthesized and characterized. The physical properties of these complexes were investigated including melting point, color, and percentage yield. Spectral and physico-analytical techniques collectively with elemental analyses were utilized to structurally elucidate the synthesized complexes. At room temperature, complexes exhibited similar solution absorption spectra in the UV–Vis region. As shown by thermal analysis, the complexes lose water molecules first, then anions, and finally ligand molecule, leaving a metal oxide residue. The complexes resulted from monomolar coordination of neutral tetradentate ligand through the two amide nitrogen and the two sulfur, with octahedral geometries. Ligand and its Ta(V) complex were structurally characterized by X-ray powder diffraction. Their optical band gaps demonstrated the ligand and complexes have semiconducting properties. Multiple bonding patterns were discovered in molecular docking simulations of the ligand against SARS-CoV-2 (6Y84) and E. coli DNA gyrase (5MMN). The binding energy of the complexes revealed active compounds capable of inhibiting SARS-CoV-2 and E. coli DNA gyrase. The antioxidant activity of the ligand and its Ln-complexes was investigated, yielding some surprising results. Finally, it is worthy to note that, the biochemical outcomes revealed that these complexes may be promising antibacterial agents. Aluminum alloys (AlSi) corrosion inhibition was investigated in 1 M HCl using potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). The inhibition efficiency was found to be 96.36 % at 500 ppm inhibitor in 1 M HCl.

Charge photogeneration dynamics in non-fullerene polymer solar cells with fluorinated and non-fluorinated acceptors.

In this work, charge photogeneration and recombination processes of PM6:IDIC-4F and PM6:IDIC blend films were investigated by the steady-state and time-resolved spectroscopies, as well as the time-dependent density functional theory calculations. The peaks in absorption and photoluminescence (PL) spectra of IDIC and IDIC-4F solutions were assigned by combining the experiment and the simulation of UV-vis absorption and PL spectra. For neat acceptor films, the exciton diffusion length of neat IDIC and IDIC-4F films was estimated as ∼28.9 and ∼19.9nm, respectively. For PM6-based blend films, we find that the fluorine substitution engineering on the IDIC acceptor material can increase the phase separate size of acceptor material in blend films, resulting in the reduction of dissociation efficiencies of acceptor excitons. In addition, we find that the charge recombination in PM6:IDIC-4F is dominated by bimolecular recombination, in comparison to geminate type carrier recombination in PM6:IDIC blend films. In addition, we find that thermal annealing treatment has a weak influence on carrier recombination but slightly reduces the exciton dissociation efficiency of acceptor in PM6:IDIC blend films, leading to a slightly reduced power conversion efficiency of PM6:IDIC solar cells. These results may shed light on the design of high-performance semiconductor molecules for application in solar cells.

Synthesis, Theoretical and Experimental Investigation of Electronic Properties of New Fluoranthenyl-Based Compounds for OLEDs Applications.

Three novel conjugated molecules have been synthesized: 2-(fluoranthen-3-yliminomethyl)-3,4-ethylenedioxythio-phene (EIF), 2-(fluoranthen-3-yliminomethyl) thiophene (TIF), and 2-(fluoranthen-3-yliminomethyl) fluorene (FIF). Optical properties were obtained from electronic absorption and emission spectra in DMSO solution. The solvatochromic properties of the molecules have been studied in different solvents. Electrochemical properties were studied by cyclic voltammetry in a Bu4NBF4 (0.1 M)/MeCN organic solution. As part of investigations to explain the nature of electronic transition process, we have performed geometry optimization of both the ground and the vertical excitation states, using the DFT B3LYP/6-311G (d, p) and TD-DFT (CPCM)/B3LYP/6-311G (d, p) approaches, respectively. Theoretical calculations closely match the experimental findings. Results show that EIF, TIF and FIF are potential candidates to be used as electron transport layer in Organic Light-Emitting Diodes (OLEDs).

Effective correction of dissolved organic carbon interference in nitrate detection using ultraviolet spectroscopy combined with the equivalent concentration offset method.

Nitrate contamination in water sources poses a substantial environmental and health risk. However, accurate detection of nitrate in water, particularly in the presence of dissolved organic carbon (DOC) interference, remains a significant analytical challenge. This study investigates a novel approach for the reliable detection of nitrate in water samples with varying levels of DOC interference based on the equivalent concentration offset method. The characteristic wavelengths of DOC were determined based on the first-order derivatives, and a nitrate concentration prediction model based on partial least squares (PLS) was established using the absorption spectra of nitrate solutions. Subsequently, the absorption spectra of the nitrate solutions were subtracted from that of the nitrate-DOC mixed solutions to obtain the difference spectra. These difference spectra were introduced into the nitrate prediction model to calculate the equivalent concentration offset values caused by DOC. Finally, a DOC interference correction model was established based on a binary linear regression between the absorbances at the DOC characteristic wavelengths and the DOC-induced equivalent concentration offset values of nitrate. Additionally, a modeling wavelength selection algorithm based on a sliding window was proposed to ensure the accuracy of the nitrate concentration prediction model and the equivalent concentration offset model. The experimental results demonstrated that by correcting the DOC-induced offsets, the relative error of nitrate prediction was reduced from 94.44% to 3.36%, and the root mean square error of prediction was reduced from 1.6108 mg L-1 to 0.1037 mg L-1, which is a significant correction effect. The proposed method applied to predict nitrate concentrations in samples from two different water sources shows a certain degree of comparability with the standard method. It proves that this method can effectively correct the deviations in nitrate measurements caused by DOC and improve the accuracy of nitrate measurement.

SUPEROXIDE–PRODUCING THERMOSTABLE ASSOCIATE FROM FLAXSEEDS, FLAXSEED CAKE AND SUNFLOWER SEEDS: ISOLATION, PURIFICATION, PROPERTIES AND MECHANISM OF SUPEROXIDE PRODUCTION

he isoforms of superoxide (О2 — ) producing thermostable associate from flaxseeds (Linum usitatissimum), flaxseed cake (scale) and sunflower seeds (Helianthus annuus), which are formed between NADPH containing lipoprotein component (NLP) and NADPH oxidase (Nox): NLP-Nox, as prooxidative components, were isolated and purified for the first time. During isolation and purification of these associates its fractionation at pH 9,5, precipitation at pH 4,8 and ion-exchanging chromatography on cellulose DE52 were carried out. The specific amounts of these associates, its optical spectral indices, the immediate mechanism of О2 — production by these associates, stationary concentrations of produced О2 — in solution and gas phase (connected with oxygen) were determined (the arithmetic averages of the obtained values were determined). The specific contents of associates have the following sequence: sunflower seeds (32,6 mg/g), flaxseed cake (21,4 mg/g), flaxseeds (10,6 mg/g). The forms of optical absorption spectra of the water solutions of О2 — -producing associates from sunflower seeds, flaxseeds and flaxseed cake are practically similar. The stationary concentrations of produced О2 — in solution have the following sequence: sunflower seeds (32,5 mkM/mg), flaxseed cake (24,6 mkM/mg), flaxseeds (20,1 mkM/mg). After blowing of the aqueous solutions of above mentioned associates by oxygen monocomponent superoxide radicals (gas phase О2 — ), were produced and transferred with oxygen into glass tubes. The stationary concentrations of produced О2 — in gas phase 2 0 2 3 № 2 70 have the following sequence: sunflower seeds (25,2 mkM/mg), flaxseed cake (18,3 mkM/mg), flaxseeds (14,4 mkM/mg). These gas phase superoxide radicals can be used in experiments on laboratory animals. Inhalation of these radicals in certain concentrations can be a therapeutic method for respiratory diseases (still in experiment).

Enhanced removal of sulfamethoxazole by Mn(II)/bisulfite in presence of nitrilotriacetic acid: Role of Mn(III)

Currently, the research on bisulfite (BS) activation by Mn(II) is very limited probably because of the low catalytic efficiency of Mn(II). Adding ligands to Mn(II)/BS system is likely to improve the BS activation, but the relative information is very rare. Therefore, the effect of nitrilotriacetic acid (NTA) on Mn(II)/BS system was investigated in this work using sulfamethoxazole (SMX) as the target contaminant. The results showed that the addition of NTA enhanced SMX removal in Mn(Ⅱ)/BS system through forming Mn(Ⅱ/III)-NTA complexes driving Mn(III)/Mn(II) cycle and stabilizing Mn(III). Alcohol scavenging experiments and competitive kinetic experiments indicated that sulfate radical (SO4•−) and hydroxyl radical (HO•) were not the main reactive species in Mn(II)/NTA/BS system. Mn(Ⅲ) was the primary oxidant for SMX elimination in this system and its existence was proved by UV-Vis absorption spectrum of reaction solution. Mn(Ⅱ)/NTA/BS system could greatly degrade SMX in near-neutral conditions, while nearly no SMX removal was observed at pH 3.0. The decrease of dissolved oxygen concentration significantly inhibited BS autocatalytic stage, thus suppressing the removal of SMX. Due to the competitive complexation of HCO3− and FA with NTA for Mn(II), their addition in Mn(Ⅱ)/NTA/BS system obviously inhibited SMX degradation. Four intermediates were detected during SMX degradation in Mn(Ⅱ)/NTA/BS system, and the possible SMX transformation pathways were speculated as N-S bond breaking, hydroxylation, amino oxidation and coupling reaction.