Ammonium Moiety Research Articles

Amino Acid Complexes of Zirconium in a Carbon Composite for the Efficient Removal of Fluoride Ions from Water.

Amino acid complexes of zirconia represent an entirely new class of materials that were synthesized and studied for the first time for the decontamination of fluoride ion containing aqueous solutions. Glutamic and aspartic acid complexes of zirconia assembled with thin carbon (stacked graphene oxide) platelets deriving from graphite oxide (GO) were synthesized by a two-step method to prepare adsorbents. The characterization of the complexes was carried out using infrared spectroscopy to determine the functional groups and the types of interaction between the composites and fluoride ions. To reveal the mechanisms and extent of adsorption, two types of batch adsorption measurements were performed: (i) varying equilibrium fluoride ion concentrations to construct adsorption isotherms at pH = 7 in the absence of added electrolytes and (ii) using fixed initial fluoride ion concentrations (10 mg/L) with a variation of either the pH or the concentration of a series of salts that potentially interfere with adsorption. The experimental adsorption isotherms were fitted by three different theoretical isotherm equations, and they are described most appropriately by the two-site Langmuir model for both adsorbents. The adsorption capacities of Zr-glutamic acid-graphite oxide and Zr-aspartic acid-graphite oxide are 105.3 and 101.0 mg/g, respectively. We found that two distinct binding modes are combined in the Zr-amino acid complexes: at low solution concentrations, F− ions are preferentially adsorbed by coordinating to the surface Zr species up to a capacity of ca. 10 mg/g. At higher concentrations, however, large amounts of fluoride ions may undergo anion exchange processes and physisorption may occur on the positively charged ammonium moieties of the interfacially bound amino acid molecules. The high adsorption capacity and affinity of the studied dicarboxylate-type amino acids demonstrate that amino acid complexes of zirconia are highly variable materials for the safe and efficient capture of strong Lewis base-type ions such as fluoride.

Amphiphilic Chitosan Bearing Double Palmitoyl Chains and Quaternary Ammonium Moieties as a Nanocarrier for Plasmid DNA.

Amphiphilic chitosan, bPalm-CS-HTAP, having N-(2-((2,3-bis(palmitoyloxy)propyl)amino)-2-oxoethyl) (bPalm) groups as double hydrophobic tails and O-[(2-hydroxyl-3-trimethylammonium)] propyl (HTAP) groups as hydrophilic heads was synthesized and evaluated for its self-assembly properties and potential as a gene carrier. The degree of bis-palmitoyl group substitution (DSbPalm) and the degree of quaternization (DQ) were approximately 2 and 56%, respectively. bPalm-CS-HTAP was found to assemble into nanosized spherical particles with a hydrodynamic diameter (DH) of 265.5 ± 7.40 nm (PDI = 0.5) and a surface charge potential of 40.1 ± 0.04 mV. bPalm-CS-HTAP condensed the plasmid pVAX1.CoV2RBDme completely at a bPalm-CS-HTAP:pDNA ratio of 2:1. The self-assembled bPalm-CS-HTAP/pDNA complexes could enter HEK 293A and CHO cells and enabled gene expression at negligible cytotoxicity compared to commercial PEI (20 kDa). These results suggested that bPalm-CS-HTAP can be used as a promising nonviral gene carrier.

Integration of catalyst and nucleophile in oxometal aminobis(phenolate) complexes with ammonium iodide pendant arm groups

An amine bisphenol ligand with an ammonium iodide group in the pendant arm (H2L) reacts with V, Mo and U oxometal precursors to form oxovanadium(V), dioxomolybdenum(VI) and dioxouranium(VI) species, respectively. In methanol solutions, vanadium(V) and molybdenum(VI) form 1:1 complexes [VO(OMe)(L)]I·2MeOH and [MoO2(L)(H2O)]I·2MeOH, where the cationic charge in the pendant arm is counterbalanced by an iodide anion. Uranium(VI) forms a complex in which the anionic charge of uranate complex unit is compensated by the cationic pendant arm. The complex crystallises as a co-crystal containing a neutral ligand precursor, namely [UO2(L)(OAc)]·[H2L]I·4MeOH. The oxovanadium(V) complex combines a Lewis acid, i.e. a pentacoordinated metal centre with a Lewis basic iodide moiety, which makes it a suitable catalyst for the coupling of CO2 with styrene oxide. The role of the ammonium moiety of the ligand is to carry the iodide nucleophile in the reaction.

Cationization of Eucalyptus Kraft LignoBoost Lignin: Preparation, Properties, and Potential Applications.

Current changes toward a more biobased economy have recently created tremendous renewed interest in using lignin as a valuable source for chemicals and materials. Here, we present a facile cationization approach aiming to impart kraft lignin water-solubility, with similar good features as lignosulfonates. Eucalyptus globulus kraft lignin obtained from a paper mill black liquor by applying the LignoBoost process was used as the substrate. Its reaction with 3-chloro-2-hydroxypropyl-trimethylammonium chloride (CHPTAC) in an aqueous alkaline medium was studied to assess the impact of different reaction conditions (temperature, time, educt concentration, molar CHPTAC-to-lignin ratio) on the degree of cationization. It has been shown that at pH 13, 10 wt % lignin content, 70 °C, and 3 h reaction time, a CHPTAC-to-lignin minimum molar ratio of 1.3 is required to obtain fully water-soluble products. Elemental analysis (4.2% N), size-exclusion chromatography (Mw 2180 Da), and quantitative 13C NMR spectroscopy of the product obtained at this limit reactant concentration suggest introduction of 1.2 quaternary ammonium groups per C9 unit and substitution of 75% of the initially available phenolic OH groups. The possible contribution of benzylic hydroxyls to the introduction of quaternary ammonium moieties through a quinone methide mechanism has been proposed. Since both molecular characteristics and degree of substitution, and hence solubility or count of surface charge, of colloidal particles can be adjusted within a wide range, cationic kraft lignins are promising materials for a wide range of applications, as exemplarily demonstrated for flocculation of anionic dyes.

Gravity-driven electrospun membranes for effective removal of perfluoro-organics from synthetic groundwater.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are emerging contaminants in water and soil. Electrospun membranes with open structure could treat PFAS in a gravity-driven mode with ultralow pressure needs. The electrospun ultrathin fibers (67 ± 27 nm) was prepared for the enhanced specific surface area; where polyvinylidene fluoride (PVDF) backbones and the grafted quaternary ammonium moieties (QA; PVDF-g-QA membranes) provided both hydrophobicity and anion-exchange ability (electrostatic interaction). High affinity towards the perfluorooctanoic acid (PFOA)/perfluorooctanesulfonic acid (PFOS) molecules (denoted as PFOX collectively) was observed, and >95% PFOX was removed from synthetic groundwater with a flux of 32.3 Lm-2h-1 at ΔPo = 313 Pa. With a higher octanol/water partitioning coefficient (Log Kow = 6.3) and close dispersion interaction parameter to the membrane backbones (16.6% difference in δd), the effective PFOS removal remained under alkaline and high conductivity conditions due to the intensive hydrophobic interaction compared to that of PFOA. Long-term studies exhibited >90% PFOX removal in an 8 h test with a capacity of 258 L/m2. Under mild regeneration conditions, PFOA and PFOS were concentrated by 35-fold and 39-fold, respectively. Overall, the gravity-driven electrospun PVDF-g-QA membranes, with adsorptive effectiveness and ease of regeneration, showed great potential in PFAS remediation.

Inclusion complexes of the macrocycle nonactin with benchmark protonated amines: aniline and serine.

The biological activity of the macrocycle nonactin is intimately related to its ionophore properties and ability to act as a selective cation carrier. While the focus of most investigations on nonactin has been on the binding of metal cations and small molecular ions, this study pursues the characterization of its inclusion complexes with primary amines with bulky structured side groups of different polarity. To this end, the complexes of nonactin with aniline and with the amino acid L-serine, both in protonated form, are considered as case studies and their relevant coordination arrangements are assessed by means of infrared action spectroscopy, quantum chemical density functional theory and Born-Oppenheimer molecular dynamics. The study suggests that the oxygen atoms from the oxolane (tetrahydrofuran) groups of nonactin constitute the preferential docking sites of the ammonium moiety of the guest cation, although conformational constraints promote interactions with the ester carbonyl backbone groups. In the aniline complex, the benzyl side ring is oriented outwards from the cavity, whereas in the case of L-serine, the side carboxylic acid and alcohol groups participate actively in the coordination process. Interestingly, the accommodation of L-serine is favoured when nonactin adopts an enantiomeric-selective folding, that promotes the tripodal coordination of the protonated amine group with oxolane rings from three nonactinic acid blocks with enantiomeric sequence (+)-(-)-(+), which allows for a facile coordination of the serine side groups. This is recognized as a general feature associated with the alternation of chiral domains in globally achiral natural nonactin, yielding mirror-symmetric complexes with the enantiomers of chiral amines.

Biocidal organic-inorganic urethane-siloxane coating by facile polymerization of single component soy-based prepolymer

The present work has considered designing bioactive and biocidal coatings to address the unsatisfactory performance of implanted medical devices due to microbial contamination. The non-leaching biocidal polyurethane-siloxane coating was fabricated through the sol-gel reaction of monocomponent soybean oil prepolymer containing the reactive alkoxysilane, quaternary ammonium, and urethane moieties (Si-PPU) on a model metallic substrate. The Si-PPU prepolymer was prepared by three-step synthesis, including the carbonation of ESBO with CO 2 , urethane formation through the non-isocyanate approach, and simultaneous quaternization, and alkoxysilane functionalization. The adhesion strength of about 2.75 MPa to an aluminum plate, high pendulum hardness (254 s −1 ), superior flexibility, and high impact resistance could meet biomedical coating applications' requirements. The superior contact-active biocidal activity towards Gram-negative and Gram-positive bacteria was provided by prepared coating. Meanwhile, no evidence for cytotoxicity was observed, and the coating presented favorable cell adhesion and proliferation. The high cell viability (>90%) and low hemolysis rate (HR < 1%) confirmed the cytocompatibility of coatings. • Alkoxysilane, quaternary, and urethane functionalized soybean oil was synthesized. • Urethane-siloxane bio-based antibacterial coating was prepared by sol-gel process. • Promising bactericidal along with excellent biocompatibility was attained.

Cu(II), Mn(II) and Zn(II) complexes of hydrazones with a quaternary ammonium moiety: synthesis, experimental and theoretical characterization and cytotoxic activity.

In this paper, Cu(II), Mn(II) and Zn(II) complexes with N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride (HL1Cl) were synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and DFT calculations. In all three complexes, a ligand (L1) is coordinated in a deprotonated formally neutral zwitterionic form via NNO donor set atoms. Cu(II) and Zn(II) form mononuclear penta-coordinated complexes [CuL1(N3)(CH3OH)]BF4 and [ZnL1(N3)2], respectively, while Mn(II) forms a binuclear [Mn2L12(μ-1,1-N3)2(N3)2]·2CH3OH complex, with unusual distorted trigonal-prismatic geometry around the metal centers. The antimicrobial activity of these complexes was tested against a panel of Gram-negative and Gram-positive bacteria, two yeasts and one fungal strain. The binuclear Mn(II) complex showed antifungal activity of similar intensity to amphotericin B. Based on the results of the brine shrimp test and DPPH radical scavenging activity, the most active Cu(II) and Mn(II) complexes were selected for evaluation of cytotoxic activity against five malignant cancer cell lines (HeLa, A375, MCF7, PC-3 and A549) and one normal cell line HaCaT. Both complexes showed significant activity. It should be pointed out that the activity of the Mn(II) complex against the MCF7 breast cancer cell line is only slightly weaker than that of cisplatin, but with selectivity to the tumor cell line in comparison to normal HaCaT cells, which is non-existent in the case of cisplatin.

Hollow-Fiber RO Membranes Fabricated via Adsorption of Low-Charge Poly(vinyl alcohol) Copolymers

We report a new type of alkaline-stable hollow-fiber reverse osmosis (RO) membrane with an outside-in configuration that was established via adsorption of positively charged poly(vinyl alcohol) copolymers containing a small amount of quaternary ammonium moieties. Anionic sulfonated poly(arylene ether sulfone nitrile) hollow-fiber membranes were utilized as a substrate upon which the cationic copolymer layer was self-organized via electrostatic interaction. While the adsorption of the low-charge copolymer on the membrane support proceeded in a Layer-by-Layer (LbL) fashion, it was found that the adsorbed amount by one immersion step was enough to form a defect-free separation layer with a thickness of around 20 nm after cross-linking of vinyl alcohol units with glutaraldehyde. The resultant hollow-fiber membrane showed excellent desalination performances (NaCl rejection of 98.3% at 5 bar and 1500 mg/L), which is comparable with commercial low-pressure polyamide RO membranes, as well as good alkaline resistance. The separation performance could be restored by repeating the LbL treatment after alkaline degradation. Such features of LbL membranes may contribute to extending RO membrane lifetimes.

Photobase-Driven Excited-State Intramolecular Proton Transfer (ESIPT) in a Strapped π-Electron System.

We report a new design strategy for an excited-state intramolecular proton transfer (ESIPT) fluorophore that can be used in acidic media. A photobasic pyridine-centered donor-acceptor-donor-type fluorophore is combined with a basic trialkylamine "strap". In the presence of an acid, protonation occurs predominantly at the amine moiety in the ground state. A single-crystal X-ray diffraction analysis confirmed the formation of a pre-organized intramolecular hydrogen-bonded structure between the resulting ammonium moiety and the pyridine ring. Upon excitation, the intramolecular charge-transfer transition increases the basicity of the pyridine moiety in the excited state, resulting in proton transfer from the amine to the pyridine moiety. Consequently, the fluorophore takes on a polymethine-dye character in the ESIPT state, which gives rise to significantly red-shifted emission with an increased fluorescence quantum yield.

Artificial neural network and response surface methodology modeling for diclofenac removal by quaternized mesoporous silica SBA-15 in aqueous solutions

Diclofenac (DCF) is a non-steroidal, anti-inflammatory drug commonly prescribed for humans and animals. DCF has been widely detected in aquatic environments and wastewater, and so various adsorbents have been applied for DCF removal from aqueous solutions. Here, we explored DCF removal by quaternary ammonium-functionalized mesoporous silica SBA-15 (q-SBA-15) in aqueous solutions using artificial neural network (ANN) and response surface methodology (RSM) modeling. For this purpose, SBA-15 was synthesized and quaternized with dimethyloctyl[3-(trimethoxysilyl)propyl] ammonium chloride to obtain q-SBA-15. The physicochemical characteristics of q-SBA-15 were examined using various instruments including field emission scanning electron microscopy, transmission electron microscopy, elemental analysis, nitrogen gas adsorption-desorption analysis, nuclear magnetic resonance spectroscopy, X-ray diffractometry, Fourier-transform infrared spectrometry (FTIR), and X-ray photoelectron spectrometry (XPS). N2 adsorption-desorption analysis indicated that q-SBA-15 had a BET surface area of 125.1 m2/g, an average pore diameter of 3.86 nm, and a mesopore volume of 0.121 cm3/g. In the FTIR spectra, several new peaks appeared after DCF removal, confirming DCF adsorption onto the surface of q-SBA-15. The XPS spectra illustrated that DCF was adsorbed onto N+ surface sites on the quaternary ammonium moiety of q-SBA-15 through anion exchange between anionic DCF− and chloride ion. Single-parameter experiments were conducted in terms of initial pH, adsorbent dosage, reaction time, and initial DCF concentration. DCF removal rate decreased gradually in the initial pH of 6.0–10.0. DCF removal reached equilibrium at 12 h with the maximum removal capacity of 593 mg/g. Multi-parameter experiments were designed using the central composite design method with four input parameters and two output parameters (DCF removal rate and final pH). Fifty-six experiments (28 experimental conditions in duplicate) were conducted to examine the simultaneous effects of the input parameters on the output parameters. Based on the experimental data, RSM and ANN models were developed to predict the DCF removal rate and final pH. The additional experimental data (4 experimental conditions in duplicate) demonstrated that the developed ANN model had better predictability than the RSM model for the output parameters.

Quaternized Polydopamine Coatings for Anchoring Molecularly Dispersed Broad-Spectrum Antimicrobial Silver Salts.

Because of the broad-spectrum antimicrobial efficacy, silver-based coatings have emerged as the popular choice to apply over frequently touched surfaces for mitigating the spread of nosocomial infections. Despite the advancements through various coating strategies, clustering of the active component remains a bottleneck in achieving the molecular-scale dispersion of silver. To circumvent this, the current study takes advantage of the recent findings of quaternary ammonium moieties forming molecular complexes with silver salts that differ from the simple adduct between the individual components. Here we demonstrate the quaternization of oxidatively cross-linked polydopamine coatings over magnetite nanoparticles to anchor ionic silver at a molecular-scale dispersion. The silver-derivatized materials exhibit remarkable broad-spectrum antimicrobial properties against representative microbes like E. coli, S. aureus, and A. niger. Also, the study reveals the materials' antibiofilm efficacy (∼80-90%) against both bacteria. Further recyclability studies have proven the sustained bactericidal properties up to five cycles. The surface derivatization strategy has then been extended to cover glass slips that have also shown the retention of the bactericidal properties even after wiping 20 times with artificial sweat. The biocompatibility of the materials has been ascertained with treated water against the mouse fibroblast and human embryonic kidney cell lines. The current study offers insights in developing coatings with molecular-scale dispersion of ionic silver to achieve broad-spectrum antimicrobial properties in an atom-economical and sustainable manner.

A water soluble hydrazone probe for subsequent fluorescent detection of Zn2+ and S2− in neat aqueous solution and imaging in mitochondria of living cells

A simple water soluble hydrazone sensor (1·Cl) has been developed to selectively chelate with Zn2+ via an O2N donor set, leading to specific fluorescence enhancements. The highly emissive 1-Zn2+ complex can serve as a reversible on-off sensor for S2−. The detection limits of 1·Cl for Zn2+ and S2− are 66.0 and 32.6 nM, respectively. The recognition mechanism was carefully investigated through FL, UV-vis, 1H NMR, ESI-MS, time-resolved fluorescence, and density functional theory (DFT) calculations. Owing to the mitochondria-targeting ability of the terminal quaternary ammonium moiety, 1·Cl was successfully applied to image mitochondrial Zn2+ and S2−.

Whole-blood metabolomics of dementia patients reveal classes of disease-linked metabolites

Dementia is caused by factors that damage neurons. We quantified small molecular markers in whole blood of dementia patients, using nontargeted liquid chromatography-mass spectroscopy (LC-MS). Thirty-three metabolites, classified into five groups (A to E), differed significantly in dementia patients, compared with healthy elderly subjects. Seven A metabolites present in plasma, including quinolinic acid, kynurenine, and indoxyl-sulfate, increased. Possibly they act as neurotoxins in the central nervous system (CNS). The remaining 26 compounds (B to E) decreased, possibly causing a loss of support or protection of the brain in dementia. Six B metabolites, normally enriched in red blood cells (RBCs), all contain trimethylated ammonium moieties. These metabolites include ergothioneine and structurally related compounds that have scarcely been investigated as dementia markers, validating the examination of RBC metabolites. Ergothioneine, a potent antioxidant, is significantly decreased in various cognition-related disorders, such as mild cognitive impairment and frailty. C compounds also include some oxidoreductants and are normally abundant in RBCs (NADP+, glutathione, adenosine triphosphate, pantothenate, S-adenosyl-methionine, and gluconate). Their decreased levels in dementia patients may also contribute to depressed brain function. Twelve D metabolites contains plasma compounds, such as amino acids, glycerophosphocholine, dodecanoyl-carnitine, and 2-hydroxybutyrate, which normally protect the brain, but their diminution in dementia may reduce that protection. Seven D compounds have been identified previously as dementia markers. B to E compounds may be critical to maintain the CNS by acting directly or indirectly. How RBC metabolites act in the CNS and why they diminish significantly in dementia remain to be determined.

Structure-property relationship of poly(2,6-dimethyl-1,4-phenylene oxide) anion exchange membranes with pendant sterically crowded quaternary ammoniums

Steric hindrance engineering is of great significance to the preparation of new stable organic cations and durable polymeric anion exchange membrane materials. In this work, we presented a study of the structure-property relationship in quaternized poly (2,6-dimethyl-1,4-phenylene oxide) containing bulky n-propyl, isopropyl, or cyclohexyl-functionalized quaternary ammonium moieties. To our surprise, PPO-iP membranes possessing isopropyl-based QA cations showed higher water uptake than n-propyl- and cyclohexyl-containing analogues (PPO-nP and PPO-CH), in which obvious microphase-separated morphology was found. Thus, PPO-iP membranes displayed the highest hydroxide conductivity at 20 °C in water (37.3 mS/cm, IEC = 1.90 mmol/g). A standard protocol (1 M or 2 M NaOH at 60 °C) was used to determine the chemical stability of model cations and membranes both having sterically crowded QAs. Minor loss (<2%) in conductivity was observed for PPO-CH membranes after the treatment in 2 M NaOH at 60 °C for 216 h, highlighting the excellent alkaline stability, while significant degradation of PPO-iP and PPO-nP was confirmed by NMR characterization of the aged samples. In addition, the prepared PPO-based AEMs having sterically crowded QA cations were compared in alkaline H2/O2 fuel cells, demonstrating that the highly conductive PPO-iP membrane exhibited a peak power density of 182 mW/cm2 under optimized testing conditions.

Influence of lipid bilayer composition on the activity of antimicrobial quaternary ammonium ionenes, the interplay of intrinsic lipid curvature and polymer hydrophobicity, the role of cardiolipin

Incorporation of hydrophobic component into amphiphilic polycations structure is frequently accompanied by an increase of antimicrobial activity. There is, however, a group of relatively hydrophilic polycations containing quaternary ammonium moieties along mainchain, ionenes, which also display strong antimicrobial and limited hemolytic properties. In this work, an influence of a hydrophobic side group length on antimicrobial mechanism of action is investigated in a series of novel amphiphilic ionenes. High antimicrobial activity was found by determination of minimum inhibitory concentration (MIC) and minimum bactericidal, and fungicidal concentration (MBC and MFC) in both growth media and a buffer. Biocompatibility was estimated by hemolytic and mammalian cells viability assays. Mechanistic studies were performed using large unilamellar vesicles (LUVs) with different lipid composition, as simplified models of cell membranes. The investigated ionenes are potent and selective antimicrobial molecules displaying a decrease of antimicrobial activity correlated with increase of hydrophobicity. Studies using LUVs revealed that the cardiolipin is an essential component responsible for the lipid bilayer permeabilization by investigated ionens. In contrast to relatively hydrophilic ionenes, more hydrophobic polymers showed an ability to stabilize membranes composed of lipids with negative spontaneous curvature in a certain range of polymer to lipid ratio. The results substantially contribute to the understanding of antimicrobial activity of the investigated class of polymers.

An Activatable Host-Guest Conjugate as a Nanocarrier for Effective Drug Release through Self-Inclusion.

There is a challenge in supramolecular chemotherapy for constructing a system equipped with both sufficient protection and high-efficiency release of drugs. To this end, a new strategy of an activatable host-guest conjugate with self-inclusion property is proposed. Based on the binding affinity gain of intramolecular host-guest self-inclusion, an activatable host-guest conjugate was designed, bearing cucurbit[7]uril as the host, an alkyl ammonium moiety as the guest, and the redox-responsive disulfide linkage. Oxaliplatin, a clinical antitumor drug, could be firmly encapsulated by the activatable host-guest conjugate to form the supramolecular drug with high stability. Moreover, oxaliplatin loaded in the activatable host-guest conjugate could be almost completely released by self-inclusion triggered by glutathione in a tumor microenvironment, thus exhibiting comparable antitumor bioactivity with naked oxaliplatin through in vitro cell experiments. It is highly anticipated that this line of research may open new horizons for programmable and on-demand supramolecular chemotherapy with high antitumor efficiency.

Star-shaped quaternary ammonium compounds with terminal amino groups for rapidly breaking oil-in-water emulsions

Two star-shaped quaternary ammonium compounds, named as T-P-EDA and T-P-DETA, were synthesized with the melamine as the hydrophobic core and the quaternary ammonium moieties as the hydrophilic sub-core. Moreover, they were fully characterized by the FT-IR, 1H NMR, TGA and their demulsification properties were systemically investigated. It was found that both of the compounds showed higher demulsification efficiency than traditional linear cationic demulsifier (CW-01) in breaking the polymer flooding oil-in-water (O/W) emulsions. Notably, for a 1500 mg/L oil containing emulsion, it achieved ~99.5% oil removal ratio in 10 min at 30℃ by adding 80 mg/L T-P-EDA or T-P-DETA, while the oil removal rate of CW-01 was 93.5% at the same conditions. Furthermore, the interfacial tension, turbidity, and zeta potential measurements were performed, which indicated that the electrostatic interaction and hydrogen bonding between the demulsifiers and the surfactants were the driving forces for the enhancement of demulsification efficiency. T-P-EDA and T-P-DETA may potentially serve as the faster, more efficient and inexpensive demulsifiers.

Incorporation of one or dual Brønsted acidic sites within the mesopores of MCM-41: Synthesis and catalytic activity in acetalization reaction

In recent years, various kinds of heterogeneous acid catalysts have been prepared and utilized for different catalytic applications. Among them, designing the easily recoverable catalysts containing two distinct Brønsted acidic sites with enhanced catalytic properties is promising. In this work, modification of the mesopores of MCM-41 as a siliceous solid support with two suitable nitrogen-containing amino- and piperazine-propylsilyl groups followed by covalent interaction with 1,4-butane sultone introduced sulfonic acid groups to this mesoporous material. The additional electrostatic interaction with phosphotungstic acid groups generated the second acidic sites on ammonium and piperazinium moieties. The successful synthesis of these solid acid catalysts was confirmed by FT-IR, energy dispersive X-ray (EDX), and inductively coupled plasma optical emission (ICP-OES) spectroscopies; CHN elemental analysis; nitrogen sorption; and XRD techniques. The catalytic experiments in benzaldehyde acetalization with ethylene glycol resulted in moderate to high activity from 76% to 97% within 2 h. Moreover, the higher catalytic activity was related to the one possessing two kinds of acidic sites due to the synergistic effect between these acidic sites.

Tailoring the refractive index and surface defects of CsPbBr3 quantum dots via alkyl cation-engineering for efficient perovskite light-emitting diodes

All inorganic CsPbBr3 perovskite quantum dots (PeQDs) have emerged as great candidates for next-generation perovskite quantum dots light-emitting diodes (PeQLEDs) applications due to their excellent optoelectronic and light-emitting properties. However, the performance of CsPbBr3 based PeQLEDs is hindered by (i) the long-chain, synthetic insulating ligands on PeQDs surfaces and (ii) the inherently high refractive index (n) of the PeQDs that often leads to internal light confinement loss. These major shortcomings are addressed by introducing a short-chain ammonium moiety, namely phenethylammonium bromide (PEABr), via spin-coating to passivate the surface of the PeQDs films. PEABr passivation can effectively annihilate the intrinsic bromide vacancies of PeQDs and simultaneously tune the refractive index of the PeQDs films. The reduced n-mismatch between the emitter and the charge transporting layers suppresses the waveguide loss after PEABr passivation and significantly elevates the external quantum efficiency (EQE) and maximum luminance of the PeQLEDs from ~ 1.0% to ~ 6.85% and ~ 1300 cd m−2 to ~ 13000 cd m−2, respectively. More importantly, the environmental stability of the PeQDs also improves remarkably following PEABr passivation. The alky cation engineering demonstrated herein is a facile yet efficient approach to simultaneously boost the performance and stability of CsPbBr3 PeQDs.