Water Solvent Mixtures Research Articles

Preparation of amorphous Nd/Dy-based metal organic framework@MXene for solar driven selective photocatalytic and serving as sensor for fluorescence quenching detection, and biological activity

The development of a new Neodymium/Dysprosium metal–organic framework, referred to as Nd/Dy-BTC MOF, based on benzene-1,2,4-tricarboxylic acid, has been achieved through an in situ growth process on 2D transition metal carbides (MXene) surfaces. This synthesis was conducted via a solvothermal method utilizing a solvent mixture of water, ethanol, and dimethylformamide. The primary objective of this research is to investigate the framework’s efficacy as a photocatalyst for the degradation of anionic dye, as well as its potential for sensing certain explosives. The Nd/Dy-MOF@MXene has been characterized by various analysis techniques. The prepared Nd/Dy-MOF@MXene was utilized as catalyst in selective degradation of methyl orange dye. The study examined the influence of pH and catalyst concentration, revealing that the catalyst achieves peak efficiency of 93.55% when exposed to sunlight in an acidic medium. The reusability of the catalyst shows the highest efficient photocatalyst after four cycles of reusability. The detection of explosives, specifically 2,4,6-trinitrophenol, through photoluminescence techniques has been conducted, utilizing the Stern-Volmer equation to evaluate the quenching efficiency. The findings indicated remarkable efficiency and selectivity of Nd/Dy-MOF@MXene for 2,4,6-trinitrophenol, achieving a quenching efficiency of 91%. Furthermore, the reusability tests demonstrated that Nd/Dy-MOF@MXene exhibits outstanding recyclability, maintaining performance over five cycles. The antibacterial activity of Nd/Dy-MOF@MXene was investigated against Gram-positive and Gram-negative strains due to indication of medicine properties of Nd/Dy-MOF@MXene.

Solvatochromism, preferential solvation and excited state dipole moments of flufenamic acid in different solvent polarities

The influence of pure solvent and binary solvent mixtures on the optical properties of non-steroidal anti-inflammatory drug (NSAID) molecule, specifically flufenamic acid (FLA), has been studied using absorption and fluorescence spectroscopic techniques. A bathochromic shift is observed in the emission wavelength of FLA with an increase in the solvent polarity of pure solvents, attributed to the highest stability of the excited state. The spectral properties are correlated with Lippert–Mataga, solvent polarity parameter, Kamlet, and Catalan solvent polarity parameters, suggesting that both general and specific solvent effects influence the spectral properties, with general solvent effects dominating over specific solvent effects. Preferential solvation studies have been carried out in tetrahydrofuran (THF) and water solvent mixture, revealing variations in the preference for solvation of FLA as a function of the mole fraction of water. Solvatochromic data are utilized to estimate the excited state dipole moment in pure solvents using different solvatochromic methods, revealing that the excited state dipole moment of FLA is higher than its ground state counterpart. The increase in dipole moment in the excited state compared to the ground state is explained based on intramolecular charge transfer (ICT), with elaboration and discussion on the possible resonance structure corresponding to ICT, inferring the more polar nature of the excited state compared to the ground state. The effect of solute polarizability on the excited state dipole moment and change in dipole moment is also discussed.

Simultaneous determination of picroside I and picroside II in dietary supplements by high performance liquid chromatography with PDA detector

Picroside I and picroside II are two compounds found in the Picrorhiza Kurroa plant, which have anti-cirrhosis, antioxidant, anti-inflammatory, fever, and asthma effects, etc. They are included in the ingredients of many dietary supplement products that help protect the liver and bile, prevent oxidation, etc. Therefore, determining the content of these two active ingredients in dietary supplements is necessary to evaluate product quality. In this study, highperformance liquid chromatography (HPLC-PDA) was used to simultaneously determine picroside I and picroside II in dietary supplements. The analytes in the samples were extracted with methanol for 60 min using a horizontal shaking technique. The extract was then filtered and determined by the HPLC–PDA method with the following conditions: C18 Column (250 mm x 4.6 mm; 5 µm) and a corresponding pre-column (3.9 mm x 5 mm; 5 µm), the mobile phase consists of a solvent mixture of acetonitrile and water according to the gradient program, detection wavelength 265 nm. The method has good specificity, the calibration curve of picroside I and picroside II has a linear coefficient R2 > 0.9999 and the repeatability and recovery meet the AOAC requirements. The method limits of detection (MDL) for these two substances were 4.3 mg/kg and 3.2 mg/kg, respectively. The method was applied to simultaneously determine picroside I and picroside II in 30 different dietary supplement products. The results detected analytes in 3 samples positive with picroside I and picroside II concentrations ranging from 98.8 to 148 mg/kg.

Ionic surfactants critical micelle concentration prediction in water/organic solvent mixtures by artificial neural network

Abstract Critical micellar concentration (CMC) is a key physicochemical property of surfactants used to study their behaviour. This property is affected by factors such as temperature, pressure, pH, the type of organic solvent/water mixture, the chemical structure of the surfactants and the presence of electrolytes. Most of the existing studies in the literature have predicted the CMC under fixed conditions based on the chemical parameters of the surfactant. In this study, a machine learning approach using artificial neural network (ANN) models was used to estimate the CMC of some ionic surfactants. These models considered variables defining both the organic solvent-water mixture (T, molecular weight, molar fraction and log P) and the chemical structure of the surfactant (number of atoms of each element). A database consisting of a total of 258 CMC values for 10 ionic surfactants was collected from the literature. The ANN architecture consisting of an input layer with 12 neurons, an intermediate layer with 25 neurons and one neuron in the output layer is proposed. According to the results, the normalized ANN models provided the best statistical adjustments for the CMC prediction. These ANN models could be a promising method for CMC estimation.

Exploring Cyclopentannulation as an Effective Synthetic Tool to Design Polycyclic Aromatic Hydrocarbon AIEgens for Bioimaging.

Synthesis of various polycyclic aromatic hydrocarbons (PAHs) from a palladium-catalyzed [3 + 2] cyclocondensation reaction is reported herein. The design strategy consisted of reacting the sterically hindered 1,2-bis(3,5-ditert-butylphenyl)acetylene 2 with myriad brominated anthracene and pyrene surrogates, resulting in the formation of target molecules MCP1-2 and DCP1-3, which exhibited excellent solubility in commonly used organic solvents and unveiled prominent aggregation-induced emission (AIE) characteristics in tetrahydrofuran and water solvent mixtures. Calculations using density functional theory (DFT) were utilized to validate both the contorted structures of the target molecules and their electronic conjugation featuring HOMO-LUMO band gaps (ΔE) in the range of ∼2.88 to 2.97 eV for the monocylopentannulated PAHs MCP1-2, and between ∼2.23 to 2.41 eV for the dicyclopentannulated PAHs DCP1-3. Furthermore, the biomedical features of DCP2 were investigated in cell-imaging experiments employing the RAW 264.7 macrophage cell line as a model system showing a high biocompatibility for DCP2, thus paving the way for its potential application in bioimaging. These findings underscore the significance of the target compounds as prominent AIEgens with exceptional photophysical properties and biocompatibility, therefore promoting them as valuable tools for bioimaging applications.

Raman Microscopic Investigation of Organic Solvent Concentration Profiles in Proton Exchange Membranes and Their Permeability

Direct alcohol fuel cells (DAFCs) suffer from severe problems related to the employed polymer electrolyte membranes, such as fuel crossover, resulting in low faradaic efficiency and performance of the fuel cell.1,2,3 We introduce a 3D-printed diffusion cell setup, which is capable of determining the interaction of membranes and organic solvents via confocal Raman microscopy.4 Thus, the suitability of proton exchange membranes (PEMs) for usage in DAFCs can be evaluated. In this setup, the membrane is clamped between two flow channels, similar to the flow field plates of a fuel cell. The donor channel is filled with an organic solvent-water mixture, and the receptor channel is filled with water. Depth scans through the membrane and the two flow channels provide concentration profiles of the organic solvent within the membrane, which are used to calculate membrane properties such as permeability and sorption coefficient (see Fig. 1).In this study, the membrane-solvent interactions between standard unreinforced and composite PEMs and various organic solvent solutions, such as 2-propanol, acetone, and ethanol, are investigated. All membranes analyzed show a preference for organic solvent absorption from 1 M solutions, with sorption coefficients ranging from 2.5 to 3.0. In addition to the absorption, the organic solvents permeate through the membrane. The corresponding permeabilities range from 10-5 to 10-4 cm² s-1. However, the permeabilities of the membranes for different solvents do not scale with their sorption coefficients, in contrast to the membrane swelling.This diffusion cell setup is an accessible and fast pre-screening method, which can enhance the development and evaluation of new ion exchange membranes for use in DAFCs and related applications.

Photo-responsive anticounterfeiting inks switching between colorless and cyan/magenta/yellow for flexible, full-color, and large-area printing

Inkjet printing of photo-responsive patterns capable of switching between colorless and full-color is regarded as an innovative anticounterfeiting technique with a higher security level. Therefore, colorless inks which can be changed to cyan (C), magenta (M), and yellow (Y) upon photochromism are highly required. Herein, three photochromic (PC) inks C, M, and Y switching between colorless and cyan/magenta/yellow, respectively, have been successfully prepared by dissolving viologen derivatives AV, AEV, and NOV in solvent mixtures of water, ethanol, and ethylene glycol, with sodium dodecyl sulfate (SDS) as surfactant. With a mass fraction of 0.5 wt% for SDS, an optimal rheological property with a viscosity of 3.48 mPa·s, a contact angle of 29.4° on poly (ethylene terephthalate) (PET) substrate, a surface tension of 23.16 mN m−1, and a Z value of 3.85, is realized for ink C. Under the same conditions, inks M and Y are prepared and display suitable rheological properties for inkjet printing. The films are invisible initially and become colorful upon UV irradiation with no significant decay after 20 repetitive PC switching. Subsequently, various colorful patterns with high resolutions were printed on conventional A4 paper and become visible only after irradiation by a UV lamp. Therefore, these photo-responsive tricolor inks can be used in anticounterfeiting field and two practical examples of a stamp and a personal check with cryptical texts and color information have been demonstrated. Overall, the developed photo-responsive C/M/Y inks can be utilized in flexible, full-color, and large-area printing, providing a novel approach towards innovative anticounterfeiting technology.

Synthesis and Characterization of New Azo Dye Derived from Sulfamethaxolevia Diazonium Reaction and Study its Abilityas an Acid-base Indicator

Background: Most azo dyes are synthesized by diazotization of a primary amine, followed by conjugation with one or more electron-rich nucleophiles. Objective: This study presents the synthesis of a new azocompound by converting sulfamethoxazole to a diazonium salt. Methods: via reaction with hydrochloric acid and sodium nitrite at temperatures between 0 and 5 °C, the resulting salt is then coupled with a 4-methoxyphenol reagent in alkaline medium at the above temperatures to produce an azodye given the IUPAC name of (4-((2-hydroxy-5-methoxyphenyl)diazenyl)-N-(5-methylisoxazol-3yl)benzenesulfonamide). The azo dye precipitate was purified by crystallization methods using a solvent mixture of ethanol water. Characterization was done using different analytical methods such as IR, UV-Vis and H1-NMR in addition to measurements of physical properties. Results: The reddish-pink azo compound gave a maximum absorbance of 495 nm. Acid-base titrimetric analysis was conducted to examine the chemical indicator properties of the azo dye. Clear color differences were obtained between two spaces in the pH range 2-12, where a reddishpink color was obtained in the basic medium and a yellow color in the acidic medium. Conclusions: A new azo dye successfully presented its properties as an indicator.

Agro-waste derived sulfonated biochar material as a sustainable heterogeneous catalyst for conversion of fructose to 5-hydroxymethylfurfural

BackgroundDevelopment of biomass derived solid acid catalysts has the advantage to conform the green chemistry protocol for production of 5-hydroxymethylfurfural (HMF) by dehydration of fructose. MethodWe have reported waste cashew nut shell produced char as a biochar to prepare sulfonated biochar (SBC) catalyst by incorporating –SO3H group through treatment of concentrated sulfuric acid. Significant findingsDifferent methods of characterization including XRD, FT-IR, XPS, FESEM-EDS, TEM, TPD and BET analysis, were used to study the structure, morphology, chemical compositions, acidity and porosity of the produced SBC catalysts. The mesoporous nature of the material was confirmed by the powder X-ray diffraction patterns (PXRD), type IV isotherm (BET), and flakes-like structure was observed in TEM analysis. The catalyst showed high yield of HMF (92%) under optimum conditions of 120 °C in 60 min under biphasic solvent mixture of water and toluene (1:2). High yield could be explained by high acid strength of catalyst as observed by NH3-TPD analysis. Leaching test by Sheldon's method and recyclability experiment proved the need and heterogeneity of the present catalyst.

Terahertz Sensing of L-Valine and L-Phenylalanine Solutions.

To detect and differentiate two essential amino acids (L-Valine and L-Phenylalanine) in the human body, a novel asymmetrically folded dual-aperture metal ring terahertz metasurface sensor was designed. A solvent mixture of water and glycerol with a volume ratio of 2:8 was proposed to reduce the absorption of terahertz waves by reducing the water content. A sample chamber with a controlled liquid thickness of 15 μm was fabricated. And a terahertz time-domain spectroscopy (THz-TDS) system, which is capable of horizontally positioning the samples, was assembled. The results of the sensing test revealed that as the concentration of valine solution varied from 0 to 20 mmol/L, the sensing resonance peak shifted from 1.39 THz to 1.58 THz with a concentration sensitivity of 9.98 GHz/mmol∗L-1. The resonance peak shift phenomenon in phenylalanine solution was less apparent. It is assumed that the coupling enhancement between the absorption peak position of solutes in the solution and the sensing peak position amplified the terahertz localized electric field resonance, which resulted in the increase in frequency shift. Therefore, it could be shown that the sensor has capabilities in performing the marker sensing detection of L-Valine.

Pathway Selection in Temporal Evolution of Supramolecular Polymers of Ionic π-Systems: Amphiphilic Organic Solvent Dictates the Fate of Water.

Understanding solvent-solute interactions is essential to designing and synthesising soft materials with tailor-made functions. Although the interaction of the solute with the solvent mixture is more complex than the single solvent medium, solvent mixtures are exciting to unfold several unforeseen phenomena in supramolecular chemistry. Here, we report two unforeseen pathways observed during the hierarchical assembly of cationic perylene diimides (cPDIs) in water and amphiphilic organic solvent (AOS) mixtures. When the aqueous supramolecular polymers (SPs) of cPDIs are injected into AOS, initially kinetically trapped short SPs are formed, which gradually transform into thermodynamically stable high aspect ratio SP networks. Using various experimental and theoretical investigations, we found that this temporal evolution follows two distinct pathways depending on the nature of the water-AOS interactions. If the AOS is isopropanol (IPA), water is released from cPDIs into bulk IPA due to strong hydrogen bonding interactions, which further decreases the monomer concentration of cPDIs (Pathway-1). In the case of dioxane AOS, cPDI monomer concentration further increases as water is retained among cPDIs (Pathway-2) due to relatively weak interactions between dioxane and water. Interestingly, these two pathways are accelerated by external stimuli such as heat and mechanical agitation.

Asymmetric Aldol Reactions Catalyzed by Polymeric Self-Assembly with Side-Chain Dipeptide Pendants.

To explore the role of proline amide moieties in polymer-supported organocatalysts, side-chain l-proline-l-alanine (Pro-Ala) dipeptide-containing block copolymers were synthesized, and their catalytic potential for the aldol reaction was explored. The dipeptide monomer (Boc-Pro-Ala-HEMA) was polymerized to prepare block copolymers in the presence of hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA) and hydrophobic poly(methyl methacrylate) (PMMA) macro-chain transfer agents. Boc group expulsion from the block copolymers produced double hydrophilic PPEGMA-b-P(Pro-Ala-HEMA) (1b) and amphiphilic PMMA-b-P(Pro-Ala-HEMA) (1c) polymers. The solution behaviors of the polymers were studied by various physical techniques, which showed the formation of self-assembled aggregates of 1c in water and N,N-dimethylformamide (DMF)/water solvent mixtures. These polymers are used as organocatalysts during the aldol reaction of cyclohexanone and 4-nitrobenzaldehyde in different solvent polarities, catalyst loadings, temperatures, and reaction times. This work emphasizes superior catalytic activity of 1c at lower catalyst loadings (5%) while maintaining high conversion (95%) and enantioselectivity (94%) across multiple recycling cycles in DMF/water at a 3:1 ratio (v/v).

Solvatochromism and preferential solvation of 2,6-dichloro-4-nitroaniline in pure and binary aqueous mixtures

In this study, the solvatochromic behavior of 2,6-dichloro para-nitroaniline (DCPNA) was investigated in a wide range of pure solvents, and binary solvent mixtures of water with ethanol, dimethyl sulfoxide, and dimethyl formamide at 298.15 K. The absorption spectrum of DCPNA in the ultraviolet–visible range exhibits a characteristic peak that shifts with changes in the solvent along the absorption wavelength. The influential factors and their roles in solvatochromism were determined through KAT-LSER analysis in pure solvents. Solvatochromism in binary solvent mixtures showed a completely non-linear trend with respect to the composition of the solution. The recently introduced preferential solvation model was utilized to model the absorbed light wavenumber in aqueous solvent mixtures. This model elucidates the separate effects of preferential solvation of DCPNA and the non-ideal behavior of aqueous solvent mixtures in the non-linearity of solvatochromism.

Synthesis, characterization, crystal structures and photophysical properties of pillar-layer nickel metal-organic frameworks based on 2-aminoterepthalic acid and 5-aminoisopthalic acid

Five new compounds, [Ni2(2-NH2BDC)2(bipy)2(H2O)4](1), [Ni(5-aip)(phen)(H2O)3].2H2O (2), [Ni4(5-aip)3(bipy)3(H2O)7]. 19H2O (3), [Ni(5-aip)(bipy)(H2O)]n·2H2ODMF (4), and [Ni2(2-NH2BDC)2(phen)2(H2O)4](5) based on 5-aminoisophthalic acid and 2-aminoterepthalic acid, have been synthesized at room temperature using methanol and water solvent mixture and structurally determined using single crystal X-ray diffraction.Compounds 1–3 are discret complex while compound 4 shows two-dimensional (2D) pillar-layer architecture. In all these compounds, channels are observed through CH···O interactions between adjacent molecules. Compounds 1–5 displayed one broad emission band with a center at 384 nm when excited 294 nm in their solid state at room temperature, attributed to ligand-to-metal charge transfer. In comparison with emission peaks of 5-aminoisophthalic acid and 2-aminoterepthalic acid, the luminescent emissions of these compounds are blue-shifted due to a decrease of the energy gap between the ground and excited states in the ligand upon complexation with Ni(II).

Synthesis and Characterization of Co(II) Substituted Keggin‐Type Polyoxometalates as Novel Catalysts for the Hydroformylation of 1‐Hexene in a Thermomorphic Solvent System

AbstractPolyoxometalates (POMs) are a unique class of metal oxides, being of huge interest for the catalysis society. CoII‐substituted phosphomolybdate POMs (namely H7[PCoMo11O40], H11[PCo2Mo10O40] and H15[PCo3Mo9O40]) have been successfully synthesized for the first time. The structure of the new CoII substituted POMs was solved by single‐crystal X‐ray diffraction as well as vibrational (FT‐IR and Raman) and nuclear magnetic/electron paramagnetic resonance (NMR and EPR) spectroscopy and found to be of the Keggin‐type. The Co‐POMs were then applied as molecular catalysts for the hydroformylation of 1‐hexene in a thermomorphic solvent mixture of water and 1‐butanol. This is the very first example of a 1st row transition metal POM acting as a hydroformylation catalyst achieving 46 % heptanal yield. The best results were obtained using H11[PCo2Mo10O40] as a catalyst at 140 °C, 150 bar CO/H2 1 : 2, and a reaction time of 4 h, paving the way for new POM‐based catalysts in hydroformylation reactions.

Preparation of pyridinium-based ionic liquid and application as a green catalyst for the synthetic route of 4H-1-benzopyran-5(6H)-ones

1-(4-sulfobutyl)pyridinium chlorozincate ionic liquid was synthesised in high yield (89%) through a simple route and characterised using FT-IR, NMR, and HRMS spectroscopy. The one-pot reaction was employed for the condensation reaction of benzaldehydes, 5,5-dimethyl-1,3-cyclohexanedione, and dicyanomethane, utilising the prepared ionic liquid catalyst. The optimal conditions for the reaction were achieved with a catalyst loading of 10 mol%, a solvent mixture of water and ethanol (1:1, v/v), maintained at 100°C for 180 minutes. A broad spectrum of benzopyran-5(6H)-one derivatives was prepared, yielding moderate to good results. The notable features of this procedure include readily available substrates, short reaction times, the use of environmentally friendly solvents, and the elimination of the need for chromatography in the isolation of products. Anew acidic pyridinium-based ionic liquid was successfully synthesised and used as a catalyst in the synthetic process of 2-amino-3-cyano-4-phenyl-7,7-dimethyl-7,8-dihydro-4H-1-benzopyran-5(6H)-ones. These reactions involved a condensation reaction of aromatic benzaldehydes, 5,5-dimethyl-1,3-cyclohexanedione, and dicyanomethane in a solvent mixture of ethanol and water, resulting in the desired products in moderate to good yields. The procedure is efficient and eco-friendly, and the products can be easily obtained by recrystallisation. Thus, this protocol offers an alternative to existing methods.

Comparative lipid composition and GC–MS fatty acid profiling of tropical African freshwater fishes

In dietary contexts, fish are renowned for the diverse array of unsaturated fatty acids they provide to the body. While data regarding the fatty acid composition of freshwater fish are readily available in most developed countries, research on African freshwater fish remains notably limited. In this study, we investigated the fatty acid composition of fifteen freshwater fish species from Africa, primarily Afrotropical regions. Lipids were extracted using a solvent mixture of methanol, water, and chloroform. Subsequently, total fatty acids were determined by saponification, and the fatty acid profile was analyzed via GC–MS following methylation in the presence of BF3 and methanol. The results revealed lipid levels in fish fillets ranging from 1.99 % for T. guineensis to 6.41 % for M. bananensis. Total fatty acid percentages of lipids were found to be 81.40 ± 9.15 % for S. nigripinnis, 83.75 ± 6.12 % for L. niloticus, and 92.99 ± 11.30 % for C. dageti. The fatty acid profiles of 15 properly identified fish species have been determined, with the majority being identified for the first time. The composition of health-important omega-3 fatty acids EPA and total DHA ranged from 4.82 ± 0.2 % for Cyprinus lepidotus to 17.43 ± 2.50 % for Mugil bananensis. Unsupervised multivariate data analysis of fatty acid profiles of the different fish species showed significant differences. When the fish were grouped into 4 categories based on their similarities, 12 discriminant fatty acids characteristic of each group were identified. Among these fatty acids are omega-6 acids such as γ-linolenic acid and arachidonic acid, and omega-3 7,10,13,16,19-docosapentaenoic acid (DPA). This research opens avenues for consumers to make informed dietary choices aligned with their specific fatty acid needs and preferences regarding fish consumption.

Solvent-Modulated Specific Ion Effects: Poly(N-isopropylacrylamide) Brushes in Nonaqueous Electrolytes.

Pertinent to cryopreservation as well as energy storage and batteries, nonaqueous electrolytes and their mixtures with water were investigated. In particular, specific ion-induced effects on the modulation of a poly(N-isopropylacrylamide) (PNIPAM) brush were investigated in various dimethyl sulfoxide (DMSO)-water solvent mixtures. Spectroscopic ellipsometry and neutron reflectometry were employed to probe changes in brush swelling and structure, respectively. In water-rich solvents (i.e., pure water and 6 mol % DMSO), PNIPAM undergoes a swollen to collapsed thermotransition with increasing temperature, whereby a forward Hofmeister series was noted; K+ and Li+ electrolytes composed of SCN- and I- salted-in (stabilized) PNIPAM chains, and electrolytes of Cl- and Br- salted-out (destabilized) the polymer. The cation was seen to play a lesser role than that of the anion, merely modulating the magnitude of the anion effect. In 70 mol % DMSO, a collapsed to swollen thermotransition was noted for PNIPAM. Here, concentration-dependent specific ion effects were observed; a forward series was observed in 0.2 mol % electrolytes, whereas increasing the electrolyte concentration to 0.9 mol % led to a series reversal. While no thermotransition was observed in pure DMSO, a solvent-induced specific ion series reversal was noted; SCN- destabilized the brush and Cl- stabilized the brush. Both series reversals are attributed to the delicate balance of interactions between the solvent, solute (ion), and substrate (brush). Namely, the stability of the solvent clusters was hypothesized to drive polymer solvation.

Development of tuneable polyamine top layer for nanofiltration with high stability in bleach and at extreme pHs

State-of-the-art membranes for nanofiltration are thin film composite membranes, comprising of a thin top layer on top of a porous support. Many separation processes in organic chemistry involve extreme conditions, e.g. aggressive solvents, solvent-water mixtures or extreme pH, e.g. in acid mine drainage or in Cleaning-in-Place cycles. However, the most commonly used thin film composite membranes are polyamides, typically prepared by reaction of a tri(acyl chloride) and a diamine, often trimesoyl chloride and m-phenylenediamine, respectively, which cannot withstand these extreme conditions. This study aims at preparing chemically much more robust membrane based on polyamine. As diamine, 1,2-Diaminocyclohexane is used, due to its high reactivity and in order to mimic PIMs, following its rigidity and twisted structure. Analogous to trimesoyl chloride, 1,3,5-tri(bromomethyl)benzene was used. Unfortunately, no reproducible membranes could be achieved. This was solved by increasing the number of functional groups of the bromomethyl benzene from three to four, resulting in a membrane with both very good separation performance (e.g. 99.6 % Rose Bengal rejection at a permeance of 1.03 L m−2 h−1.bar−1) and excellent stability in extreme conditions (i.e. bleach and pH <1, >13). Additionally, the formed polyamine membrane is pH-responsive and can be adjusted to the application by post-treatment, i.e. further crosslinking or quaternization.

Aminobenzothiazole fused tetraphenylethene AIEgen: Ag+, Hg2+ and Fe3+ sensing applications in aqueous medium

6-(1,2,2-triphenylvinyl)benzo[d]thiazol-2-amine (TPE-BTA) was synthesized using a multistep reaction strategy. The aggregation-induced emission (AIE) characteristics of TPE-BTA have been established in DMSO–water solvent mixtures. The color of the TPE-BTA solution changed from dark blue in DMSO to fluorescent blue in DMSO: water (70–95 %, v/v ratio). The receptor TPE-BTA showed sensitive sensing towards Ag+, Hg2+, and Fe3+ ions in the presence of the tested metal cations. TPE-BTA exhibited a limit of detection (LOD) towards Ag+, Hg2+, and Fe3+ ions as low as 4.96 × 10−7M, 2.00 × 10−7M, and 1.74 × 10−7M, respectively. The stoichiometry of complex formation between TPE-BTA and Ag+, Hg2+, and Fe3+ was 1:1 (TPE-BTA: Ag+, TPE-BTA: Hg2+, and TPE-BTA: Fe3+) based on fluorescence studies.