Presence Of Cationic Surfactant Research Articles

Interaction of Vanadium(V) with 4-(2',3',4'-Trihydroxyphenyl)-3-Nitro-5-Sulfoazobenzene in the Presence of Cationic Surfactants

Interaction of Vanadium(V) with 4-(2',3',4'-Trihydroxyphenyl)-3-Nitro-5-Sulfoazobenzene in the Presence of Cationic Surfactants

Photothermal Depth Profiling of Gelatin-Stabilised Gold Nanorods-Trastuzumab Conjugate as a Potential Breast Cancer Photothermal Agent

AbstractGold nanorods (AuNRs) are powerful photothermal agents (PTAs) in cancer treatment due to their near-infrared laser light absorption ability. However, the cytotoxicity of AuNRs caused by the presence of cationic surfactants often used and their lack of specificity affect their application in photothermal therapy. Thus, we herein developed a bioconjugate obtained from the functionalisation of AuNRs to gelatin (Gel@AuNRs), followed by the conjugation of the as-synthesised material to a breast cancer antibody, trastuzumab (Trast-Gel@AuNRs) to address these issues. The optical and structural characterization of the as-synthesized indicated no significant changes in the optical properties of AuNRs after their functionalisation with gelatin and conjugation with the antibody. The photothermal profiling of the as-synthesised materials showed that AuNRs still have an excellent photothermal conversion efficiency (PCE) after their functionalisation (20%) and their conjugation to an antibody (19%). In addition, the In vitro photothermal depth response showed that Trast-Gel@AuNRs is a promising photothermal agent for HER2-positive breast cancer treatment. Graphical Abstract

STUDYING THE COMPLEXATION OF V(V) WITH 3-[2-HYDROXY-3- SULFO-5-NITROPHENYLAZO]-PENTADIONE-2,4 IN THE PRESENCE OF A THIRD COMPONENT

In the present study, we investigated the formation of the complex vanadium c 3-[2-hydroxy-3- sulfo-5-nitrophenylazo]-pentadione-2,4 (R) in the presence of cationic surfactants (CPAS) including cetylpyridinium chloride (CPCl), cetylpyridinium bromide (CPBr), and cetyltrimethylammonium bromide (CTMABr). The study on the pH dependence of complexation revealed that the release of the VR complex occurred at pH=4 with a maximum absorption at λ=425 nm, while the reagent exhibited a maximum absorption at 383 nm. In the presence of the third component, three-component compounds VR-СPBr, VR-CPBr, and VR-CTMABr were formed. The absorption maxima of the mixed-ligand complexes V(V) were bathochromic relative to the absorption maxima of the binary complex, with λmax values of 437 nm, 449 nm, and 454 nm, respectively. The optimal pH for complexation was found to be in the acidic region at pH 4.0, 3.0, and 3.0, respectively. The impact of the third component and reagent concentrations on complex formation was also investigated, with the maximum yield of VR complex was achieved at a concentration of 8·10-5 M R, VR-CPCl at 8·10-5 M R and 8•10-4 M CPCl, VR-CPBr at 8•10-5 M R and 8•10-4 M CPBr, and VR-CTMABr at 8•10-5 M R and 8•10-4 M CTMABr. The optimal ratio of reacting components was determined to be 1:2 and 1:2:2, respectively. The compliance with Beer's law was confirmed, and molar absorption coefficients were calculated from saturation curves. The developed method was applied to the determination of vanadium (V) in the waters of the Akstafa rivers in the Kazakh region of the Azerbaijan Republic. Keywords: complexation of vanadium(V), cationic surfactants, cetylpyridinium chloride, cetylpyridinium bromide, cetyltrimethylammonium bromide.

Experimental investigation of copper oxide nanofluids for enhanced oil recovery in the presence of cationic surfactant using a microfluidic model

Microfluidics is an appealing technique for enhanced oil recovery since it offers numerous advantages over traditional core flooding mechanisms due to their realistic representation of reservoir conditions at the microscale. In this work, we investigated the performance of copper oxide-based nanofluids in the presence of a DCMS-8 cationic surfactant. First, copper oxide nanoparticles of an average particle size of 10 nm were synthesized by the sol–gel method and characterized using various characterization techniques. The results indicated that copper oxide and surfactant-based nanofluids reduced the interfacial tension by 54 %, depending on the concentration of nanoparticles in the suspension. Furthermore, the formation wettability alteration was investigated using contact angle measurements, and the results showed that nanofluid was able to reduce the contact angle from 48o to 20o in 10 min. The shear rheological response indicated that the nanofluids could reduce the viscosity of crude oil from 0.48 (Pa s) to 0.31 (Pa s). Notably, the flooding results showed that copper oxide-based nanofluids were able to recover 61 % of the original oil initially in place, with additional recovery rates of 65 % and 72 % when used with cationic surfactants, polyvinyl alcohol (PVA), and polyvinyl pyrrolidone (PVP), respectively. Finally, the fluorescent images confirmed that surfactant-based nanofluid has a higher sweeping efficiency in porous formation. In this study, the use of copper oxide nanoparticles and cationic surfactant has resulted in the creation of captivating and compelling nanofluids that exhibit reasonable stability of nanoparticles in the base fluid and high recovery rates of residual oil.

Simultaneous determination of four N-lauryl amino acid surfactants in facial cleansers by high performance liquid chromatography-ultraviolet detection

Significant developments have recently been achieved in the field of N-lauryl amino acid (NLAA) surfactants derived from renewable resources. Compared with conventional surfactants, NLAAs exhibit remarkable surfactant properties, exceptional biodegradability, good biocompatibility, and high safety profiles. These attributes have led to the widespread use of NLAAs in personal-care products. The detection methods employed for NLAAs include two-phase titration (TT), spectrophotometric analysis (SA), and high performance liquid chromatography (HPLC). However, because both TT and SA measure the total concentration of anionic active matter, identifying and quantifying individual compounds in a sample containing multiple anionic surfactants is impossible. The presence of cationic surfactants in the sample also introduces interferences, which lead to significant errors. Compared with TT and SA, HPLC offers direct and rapid testing procedures. However, compounds with no or weak UV-visible light absorption exhibit low sensitivity when detected by UV, necessitating the use of detectors such as differential refractive index detectors (RIDs), evaporative light scattering detectors (ELSDs), or charged aerosol detectors (CADs). Most HPLC users consider UV light as the fundamental configuration of the instrument, and other detectors are less commonly employed. Therefore, establishing a new HPLC method suitable for the UV detection of NLAAs is of practical significance. In this study, a novel HPLC-UV method was developed for the simultaneous detection of N-lauryl glutamine (LG), N-lauryl glycine (LC), N-lauryl alanine (LA), and N-lauryl sarcosine (LS) by optimizing the mobile-phase composition and selecting an appropriate chromatographic column and detection wavelength. The samples were mixed with acetonitrile-0.10% H3PO4 aqueous solution (60∶40, v/v) and sonicated for 10 min, then stayed at room temperature for 5 min. Subsequently, the mixture was filtered through a 0.22 μm filter membrane and separated on an Agilent Eclipse Plus C18 column (150 mm×4.6 mm, 5 μm). The mobile phase used for separation consisted of acetonitrile-0.10% H3PO4 aqueous solution at a flow rate of 1.0 mL/min. The detection wavelength was set at 205 nm, and the injection volume was 10 μL. The results demonstrated that the four NLAAs exhibited good linearity in the range of 2.0-800.0 mg/L, with correlation coefficients (r)≥0.9995. The limits of detection (LODs) ranged from 0.17 to 0.49 mg/L, and limits of quantification (LOQs) ranged from 0.57 to 1.63 mg/L. The relative standard deviations (RSDs) for precision, repeatability, and stability over 24 h were all below 2.0%. Using this method, the NLAA contents of five facial-cleanser products were determined. The results demonstrated that all five samples contained one or more NLAAs, and the total NLAA contents ranged from 64.58 to 97.01 mg/g. The five spiked-sample recoveries of the NLAAs at four different spiked levels (0.60, 4.50, 15.00, 24.00 mg/g) ranged from 94.3% to 107.4%, indicating satisfactory accuracy. However, the actual NLAA composition and label for one facial-cleanser product were not consistent with our test results. This finding demonstrates the necessity of strengthening market monitoring through testing. The proposed method has the advantages of simple pretreatment, rapid testing, good precision, high accuracy, and appropriate stability. Thus, it is suitable for the determination of NLAA contents in facial cleansers and provides an effective technical reference for the raw-material purity assessment, synthetic yield detection, and product quality control of this type of surfactant.

Adsorption of anionic dyes onto 1,5-Diphenylcarbazide functionalized magnetic hybrid polymer: Impact of water salinity and surfactants on adsorption isotherms

Herein, an effective hybrid adsorbent based on magnetic chitosan (MC) and magnetic glycidyl methacrylate (Mp(GMA)) was synthesized. The prepared hybrid material was functionalized by 1,5-Diphenylcarbazide (DPC), then employed for the adsorption of two anionic dyes (Coomassie brilliant blue G-250; CBB, and Eosin Y; EO) from their synthetic solutions. The as-fabricated adsorbent (MC-Mp(GMA)/DPC) was specifically investigated via FTIR, SEM-EDX, BET, TGA, and VSM analyses. The influence of several operational key factors; initial solution pH, initial dye concentration, contact time, temperature, and influence of cationic, anionic surfactant, and salinity on adsorption isotherms were investigated. The findings revealed that MC-Mp(GMA)/DPC highest adsorption capacities were recorded in the presence of cationic surfactant (0.795, 0.817 mmol g−1 for CBB and EO, respectively) and salinity hardly affects adsorption isotherms. Moreover, the adsorption process of each dye was reported to fit with the Langmuir model at all conditions, while the PSORE model well-defined their adsorption kinetics. Meanwhile, thermodynamics revealed that the separation of CBB and EO dyes was endothermic. Moreover, MC-Mp(GMA)/DPC possessed a desirable efficacy for the regeneration (e.g., 77.9% and 71.7 for CBB and EO, respectively) up to the 4th cycle, affirming its outstanding renewability. Overall, the produced MC-Mp(GMA)/DPC can potentially be offered as a promising recyclable dye scavenger for wastewater remediation.

Surface modification of PVDF membrane by radiation-induced admicellar polymerization of acrylamide in the presence of cationic surfactant

This article discusses the admicellar polymerization induced by radiation on the poly(vinylidene fluoride) (PVDF) membrane. There are four major stages of admicellar polymerization, which are admicelle formation, adsolubilization, polymerization, and purification. The polymerization stage was realized by using cobalt-60 (Co-60) gamma ray and PVDF as a membrane in water treatment processes, but the use of the latter is restricted due to its inherent hydrophobicity, high fouling tendency, and lack of functional groups. Therefore, this study aims to improve the water flux and permeation efficiency of the PVDF membrane by incorporating complex coordination functional groups, such as amino and carboxyl groups. Acrylamide (AAm) was radiation-grafted onto PVDF membrane in the presence of cationic surfactant, inducing admicellar polymerization. The PAAm-grafted PVDF membrane was obtained by varying the monomer concentration and irradiation dose, while the degree of grafting was found to be proportional to the concentration of monomer and irradiation dose. The changes in properties of PVDF-g-PAAm were investigated by Fourier-transform infrared (FTIR) spectroscopy, thermogravimetry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and contact angle measurement. As the amount of polyacrylamide grafted increased, the hydrophilicity introduced by AAm grafting improved in water flux.

Influence of cationic surfactants on the growth of gypsum crystals

Abstract The effect of cationic surfactants on the growth of gypsum was evaluated under conditions of a simulated production process of gypsum desulfurization. We used a laser particle size analyzer and a microscope to determine the particle size and morphology. The growth rate of gypsum was determined by the equation for the rate of chemical reaction of CaSO4·2H2O. The results showed that the growth rate at a supersaturation ratio of 2.4 increased by 50% with 30 mg/L of a dodecyldimethylbenzylammonium chloride. The gypsum morphology changed from needle-like in the absence of additives to tabular in the presence of cationic surfactants, indicating that relatively thicker and larger crystals were formed. Finally, the investigated cationic surfactants were beneficial to the normal operation of the desulfurization process.

Transport of polystyrene nanoplastics in porous media: Combined effects of two co-existing substances

Both surfactants and natural organic matters (NOMs) are substances commonly found in aqueous environments, and their effects on the transport of nanoplastics that is gradually gaining widespread attention in porous media are currently in their infancy, while their combined effects are absent. We investigated innovatively the combined effect of surfactants and NOMs on the transport of polystyrene nanoplastics (PS-NPs) in saturated porous media. Adsorption tests of surfactants and NOMs onto PS-NPs, adsorption tests of PS-NPs onto quartz sand, and transport tests of PS-NPs in saturated quartz sand were conducted. Hydrophobicity and Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy were measured and calculated. A mathematical model was employed to fit the transport of PS-NPs in porous media. It was found that the effects and action mechanisms of cationic cetyl trimethylammonium bromide (CTAB) and anionic sodium dodecylbenzene sulfonate (SDBS) on the transport of PS-NPs in porous media were distinct. In the presence of CTAB, 1 mg/L humic acid (HA) and 10 mg/L sodium alginate (SA) could promote aggregation of PS-NPs by decreasing the absolute zeta potential of PS-NPs, and reducing the energy barrier between PS-NPs and porous media and increasing the blocking and straining, thus inhibiting the transport of PS-NPs. In the presence of SDBS, SA and HA could improve the adsorption of SDBS onto PS-NPs by bridging and increasing adsorption sites, thus increasing the hydrophilicity of PS-NPs and improving the transport of PS-NPs. Whether or not NOMs were present, the transport of PS-NPs in porous media was mainly governed by the DLVO interaction energy in the presence of cationic surfactants and by hydrophobicity in the presence of anionic surfactants. This innovative observation has led to an understanding on the environmental behaviour of nanoplastics in porous media under complex environments.

Sуnthesis of terpene–methacrylic acid copolymers and their effect on the stability of inorganic dispersions in the presence of cationic surfactants

Copolymers of methacrylic acid and natural terpene monomers (α-pinene; β-pinene; ∆3-karene) with the molecular weight of (0.3–0.5)∙104 and a content of carboxyl groups of 14.5–16.3 % were synthesized. For the synthesized copolymers, hydrodynamic radius and the Kuhn segment, which characterizes flexibility of a polymer chain, were determined, as well as the Huggins constant in aqueous and saline solutions, and concentration regions for formation of supramolecular structures. In the presence of a cationic surfactant (benzetonium chloride, Hyamine), depending on the concentration of copolymers in the system, polymer-surfactant complexes were formed in soluble and insoluble forms. It has been shown that the effectiveness of the stabilizing action of soluble complexes with respect to an aqueous dispersion of calcium carbonate increases with an increase in the content of nonpolar groups in the polymer chain. A cationic surfactant (Hyamine) has been proposed as a precipitant in the method for the quantitative determination of carboxyl-containing polymers in aqueous and saline media.

Determination of trace cobalt (II) in spices samples by ultrasonic assisted cloud point extraction with spectrophotometry

In this study, ultrasonic assisted cloud point extraction (UA-CPE) method was developed for the determination of Cobalt (II) (Co(II)) in spices. After extraction and preconcentration, the Co(II) contents of the samples were determined by UV–VIS. After complexing with Ponceau Xylidine (PX) and EDTA in the presence of cationic surfactant, CTAB at pH 4.0 with Britton–Robinson (BR) buffer, Co(II) ion was withdrawn the surfactant-rich phase of nonionic surfactant, Triton X-114 (TX-114). The concentrated surfactant-rich phase containing the analyte was diluted with ethanol to a volume of 1.0 mL and then analyzed by UV–VIS spectrophotometer. The various analytical parameters affecting the UA-CPE yield were investigated and optimized. Analytical data achieved after optimization: limits of detection (LOD) and: limits of quantification (LOQ) are 0.76 and 2.59 μg L−1, respectively; The calibration curve is rectilinear for Co(II) with changed calibration sensitivity in the range of 1–10 and 10-210 μg L−1. The precision (as RSD%) is 4.8. This optimized method was applied in the analysis of various spice samples.

Rationalizing the Design of Pluronics-Surfactant Mixed Micelles through Molecular Simulations and Experiments.

Aqueous systems comprising polymers and surfactants are technologically important complex fluids with tunable features dependent on the chemical nature of each constituent, overall composition in mixed systems, and solution conditions. The phase behavior and self-assembly of amphiphilic polymers can be changed drastically in the presence of conventional ionic surfactants and need to be clearly understood. Here, the self-aggregation dynamics of a triblock copolymer (Pluronics L81, EO3PO43EO3) in the presence of three cationic surfactants (with a 12C long alkyl chain but with different structural features), viz., dodecyltrimethylammonium bromide (DTAB), didodecyldimethylammonium bromide (DDAB), and ethanediyl-1,2-bis(dimethyldodecylammonium bromide) (12-2-12), were investigated in an aqueous solution environment. The nanoscale micellar size expressed as hydrodynamic diameter (Dh) of copolymer-surfactant mixed aggregates was evaluated using dynamic light scattering, while the presence of a varied micellar geometry of L81-cationic surfactant mixed micelles were probed using small-angle neutron scattering. The obtained findings were further validated from molecular dynamics (MD) simulations, employing a simple and transferable coarse-grained molecular model based on the MARTINI force field. L81 remained molecularly dissolved up to ∼20 °C but phase separated, forming turbid/translucent dispersion, close to its cloud point (CP) and existed as unstable vesicles. However, it exhibited interesting solution behavior expressed in terms of the blue point (BP) and the double CP in the presence of different surfactants, leading to mixed micellar systems with a triggered morphology transition from unstable vesicles to polymer-rich micelles and cationic surfactant-rich micelles. Such an amendment in the morphology of copolymer nanoaggregates in the presence of cationic surfactants has been well observed from scattering data. This is further rationalized employing the MD approach, which validated the effective interactions between Pluronics-cationic surfactant mixed micelles. Thus, our experimental results integrated with MD yield a deep insight into the nanoscale interactions controlling the micellar aggregation (Pluronics-rich micelles and surfactant-rich micelles) in the investigated mixed system.

INTERACTION OF HAFNIUM(IV) WITH 6,7-DIHYDROXY‑4-CARBOXYL‑2- PHENYLBENZOPYRYLLIUM SALTS IN BINARY SYSTEMS AND IN THE PRESENCE OF CATIONIC SURFACTANTS

In the current study, the peculiarities of the complexation of Hafnium(IV) with 6,7-dihyroxy‑4-carboxyl‑2-phenylbenzopyrylium salts (CDC) in binary systems and in the presence of cationic surfactants (Surf) were studied. The CDC was synthesized by condensation of pyrogallol A with benzoylpyruvic acid in an acetic acid medium in the presence of perchloric acid. To obtain KDC bromide and chloride, the synthesis was carried out in the presence of bromide acid or by sparging of dry hydrogen chloride, respectively. Using classical spectrophotometric methods of molar ratios and Bent-French, it was found that at pH 2.5 in binary system one complex with stoichiometry Hf(IV): CDC1:2 was formed. Molar absorptivity coefficient was calculated for Hf(IV) complex with CDC and it was equal 3,9⸱104. It was shown that in the presence of cetylpyridinium chloride or cetyltrimetrylammonium bromide complexes with a molar ratio of Hf(IV): CDC: Surf = 1:2:2 were formed. It is noted that the complexes were formed within 10–15 minutes, and the absorbance of the solutions remains constant for at least 2 hours. It was established that the nature of the anion, which is part of the reagent, does not significantly affect the characteristics of the analytical form. It is shown that in the presence of cationic surfactants, the optimal pH of complex formation shifts to a more acidic region. In addition, the introduction of cationic surfactants leads to a batachromic shift of the absorption band by 10–15 nm and an increase in the molar absorptivity to 5.8⸱104 and 6.4⸱104 when cetylpyridinium chloride or cetyltrimetrylammonium bromide were used respectively. It is noted that the found analytical forms can be used as a basis for the development of combined spectroscopic methods for determining trace amounts of Hafnium(IV).

Micellization pattern of cationic surfactants in presence of azo dye in methanol mixed media

Conductivity measurements at three different temperatures (298.15, 308.15, and 318.15 K) were performed to determine the micellization nature of cationic surfactants, i.e., dodecyl trimethylammonium bromide (DTAB) and cetylpyridinium chloride (CPC), in the absence and presence of the azo dye methyl red (MR) in four mixed solvent systems (0.1 to 0.4) volume fraction of methanol in water. We calculated the critical micelle concentration (CMC) of DTAB and CPC and the degree of ionization (α) for both in the absence and presence of MR using William’s method. The interaction of surfactants DTAB and CPC with MR has been identified separately through the dye-surfactant aggregation process, with reduced CMC values due to the molecular reorientation of methyl red in the systems. Micellization becomes more likely with MR due to the formation of a molecular complex in mixed systems. We calculated different thermodynamic properties both in the absence and presence of methyl red. Such parameters are the standard Gibbs free energy of micellization (ΔGmo), the standard enthalpy of micellization (ΔHmo), the standard entropy of micellization (ΔSmo), the standard free energy of transfer (ΔGtranso) and heat capacity of micellization (ΔmCp0). In accordance with ΔGmo values, the mixtures show the spontaneous nature of micellization of DTAB and CPC with MR as well.

Spectrophotometric and Fluorescent Determination of Hydrophobic Organic Cations in the Surfactant-modified System Mo(VI)– Bromopyrogallol Red

The spectrophotometric and fluorescent characteristics of the surfactant-modified molybdenum (VI) – bromopyrogallol red reagent system were studied. The hydrophobic modification was achieved by adding cationic, nonionic surfactants, or, accordingly, mixtures of surfactant modifiers into the metal reagent system. Modification of the metal reagent system with a nonionic surfactant leads to a decrease in the limit of detection of the hydrophobic organic cation in the molybdenum (VI) – bromopyrogallol red system by the fluorescence method and an increase in the contrast of the spectrophotometric reaction. The colloid-chemical state of molybdenum (VI) – bromopyrogallol red solutions in the presence of cationic surfactant, nonionic surfactant, and their mixture was also investigated. An increase in the turbidity of the investigated solutions is registered under the conditions of a decrease in the scattering factor, which, in turn, increases the limit of detection of the spectrophotometric determination of decamethoxine in the surfactant-modified molybdenum (VI) – bromopyrogallol red system. Based on the obtained results, the conditions for controlled modification of the metal reagent system with surfactants for the determination of hydrophobic organic cations by molecular spectroscopy methods were proposed. Fluorescence and spectrophotometric detection of decamethoxine content in medicines was carried out in optimized surfactant-modified molybdenum (VI) – bromopyrogallol red systems.

Role of particle size on the cohesive strength of non-sintered (green) ceramics

Preparation of particle-loaded foams, followed by drying, sintering and/or cross-linking are widely explored routes for developing lightweight ceramics with high mechanical strength. The non-sintered dry ceramic foams are less studied due to their intricate production and the assumed poor mechanical strength of the obtained "green" materials. Here we produce lightweight ceramics from foamed particle suspensions containing spherical silica particles with radii varied between 4.5 nm and 7 µm. The wet foams are prepared in the presence of cationic surfactant and were dried at ambient conditions to obtain porous materials with mass densities between 100 and 700 kg/m3. The materials containing smaller particles exhibited much higher strength (by up to 2000 times), approaching that of the sintered materials. A new theoretical expression for predicting the mechanical strength of such materials is derived and is used to explain the measured strengths of the produced materials through the van der Waals attraction between the particles in the final dry materials.

SPECTROPHOTOMETRIC DETERMINATION OF STIBIUM (III) WITH 6,7-DIHYDROXY‑4-CARBOXYL‑2- PHENYLBENZOPYRILIUM PERCHLORATE

In the current study, the peculiarities of the complexation of Stibium(III) with 6,7-dihydroxy‑4-carboxyl‑2-phenylbenzopyrylium perchlorate (CDC) in binary systems and in the presence of cationic surfactants (Surf) were studied. Using classical spectrophotometric methods of molar ratios and equilibrium shift, it was found that in two systems two complexes with stoichiometry Sb(III): CDC are formed: 1:2 and 1:3 at pH 2.5 and pH 6.0, respectively. Molar absorptivity coefficients were calculated for Sb(III) complexes with CDC, which are 1.2⋅104 and 1.1⋅104, respectively. It is shown that in the presence of cetylpyridinium chloride or cetyltrimetrylammonium bromide complexes with a molar ratio of Sb(III): CDC: Surf =1:3:3 are formed. In the presence of cationic surfactants there is no shift in the optimal pH of complexation, but there is an increase in the number of coordinated reagent molecules due to the loosening of the hydrate shell of the ion Sb(III) due to hydrophobic hydration of the complex. In addition, the introduction of cationic surfactants leads to a batochromic shift of the absorption band by 10–15 nm and an increase in the molar absorptivity to 2.8⋅104 and 3.4⋅104 when cetylpyridinium chloride or cetyltrimetrylammonium bromide were used respectively. The method of spectrophotometric determination of Stibium(III) was developed using an analytical form based on the ternary complex Sb(III): KDC: Surf = 1:3:3, which was tested during the analysis of samples of polymer materials (polyethylene terephthalate). It is noted that the developed technique is characterized by satisfactory reproducibility and is not inferior in sensitivity to known analogues.

Binder-Free Fabrication of Prussian Blue Analogues Based Electrocatalyst for Enhanced Electrocatalytic Water Oxidation.

Developing a cost-effective, efficient, and stable oxygen evolution reaction (OER) catalyst is of great importance for sustainable energy conversion and storage. In this study, we report a facile one-step fabrication of cationic surfactant-assisted Prussian blue analogues (PBAs) Mx[Fe(CN)5CH3C6H4NH2]∙yC19H34NBr abbreviated as SF[Fe-Tol-M] (where SF = N-tridecyl-3-methylpyridinium bromide and M = Mn, Co and Ni) as efficient heterogeneous OER electrocatalysts. The electrocatalysts have been characterized by Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) analysis, and X-ray photoelectron spectroscopy (XPS). In the presence of cationic surfactant (SF), PBAs-based electrodes showed enhanced redox current, high surface area and robust stability compared to the recently reported PBAs. SF[Fe-Tol-Co] hybrid catalyst shows superior electrochemical OER activity with a much lower over-potential (610 mV) to attain the current density of 10 mA cm−2 with the Tafel slope value of 103 mV·dec−1 than that for SF[Fe-Tol-Ni] and SF[Fe-Tol-Mn]. Moreover, the electrochemical impedance spectroscopy (EIS) unveiled that SF[Fe-Tol-Co] exhibits smaller charge transfer resistance, which results in a faster kinetics towards OER. Furthermore, SF[Fe-Tol-Co] offered excellent stability for continues oxygen production over extended reaction time. This work provides a surface assisted facile electrode fabrication approach for developing binder-free OER electrocatalysts for efficient water oxidation.

Fabrication of Delaminated 2D Metal Carbide MXenes (Nb2CTx) by CTAB‐based NO2 Gas Sensor with Enhanced Stability

AbstractSensitivity is the prime factor in solid‐state gas sensors in terms of explicit noting of the change in signal. For achieving this, two vital prerequisites to be satisfied simultaneously: (i) electrical noise should be null and (ii) significant signal which is not met by the existing sensing materials. This study demonstrates that 2D metal carbide MXenes (Nb2CTx) have strong metal conductivity for noise reduction and abundant functional groups for detecting the signal toward higher sensitivity. This work shows successful exfoliation of Nb2CTx in the presence of cationic surfactants like cetyltrimethylammonium bromide (CTAB), which is significantly stable. The confirmation about the successful stabilization of Nb2CTx in DI water is obtained from material characterization and gas sensing observations. The experiments show that the dynamic sensing response of the Nb2CTx‐CTAB sensor increases by ≈3 times for NO2 gas detection. The sensitivity of the Nb2CTx and Nb2CTx‐CTAB found 0.543 and 1.686 ppm–1, respectively, toward NO2 gas. Over time (up to 30 d), CTAB functionalized Nb2CTx MXene noticed trace‐level detection capability with better environmental stability than pristine MXene. Herein, the obtained results show the gas sensing characteristics of Nb2CTx‐CTAB and witness a selective and ultra‐sensitive response toward NO2 gas detection.

SPECTROPHOTOMETRIC DETERMINATION OF BISMUTH (III) WITH 6,7-DIHYDROXY‑4-CARBOXYL‑2-PHENYLBENZOPYRILIUM PERCHLORATE

In the current study, the peculiarities of the complexation of Bi(III) with 6,7-dihyroxy‑4-carboxyl‑2-phenylbenzopyrylium perchlorate (CDC) in binary systems and in the presence of cationic surfactants (Surf) were studied. Using classical spectrophotometric methods of molar ratios and equilibrium shift, it was found that in two systems two complexes with stoichiometry Bi(III): CDC are formed: 1:2 and 1:3 at pH 2.0 and pH 4.5, respectively. Molar light absorption coefficients were calculated for Bi(III) complexes with CDC, which are 1.4⸱104 and 1.0⸱104, respectively. It is shown that in the presence of cetylpyridinium chloride or cetyltrimetrylammonium bromide complexes with a molar ratio of Bi(III): CDC: Surf =1:3:3 are formed. In the presence of cationic surfactants there is no shift in the optimal pH of complexation, but there is an increase in the number of coordinated reagent molecules due to the loosening of the hydrate shell of the ion Bi(III) due to hydrophobic hydration of the complex. In addition, the introduction of cationic surfactants leads to a batochromic shift of the absorption band by 10–15 nm and an increase in the molar absorption coefficient to 3.1⸱104 and 4.1⸱104 when using cetylpyridinium chloride or cetyltrimetrylammonium bromide, respectively. Methods of spectrophotometric determination of Bi(III) with the use of analytical forms based on complexes of 1:2 and ternary complex 1:3:3 were developed, which were tested in the analysis of pharmaceuticals, alloys and model solutions. It is noted that the proposed methods are characterized by satisfactory reproducibility and are not inferior in sensitivity to known analogues.