Ammonium Halides Research Articles

Quaternary Ammonium-Based Ionosilica Hydrogels as Draw Solutes in Forward Osmosis.

In the last few years, forward osmosis (FO) has attracted increasing interest as a sustainable technique for water desalination and wastewater treatment. However, FO remains as an immature process principally due to the lack of efficient and easily recyclable draw solutes. In this work, we report that ionosilica hydrogels based on quaternary ammonium halide ionosilica are efficient draw solutes in FO. Fluidic ionosilica hydrogels were obtained via hydrolysis-polycondensation reactions of a trisilylated quaternary ammonium precursor in slightly acidic water/ethanol solvent mixtures. The liquid-to-gel transition of the precursor and the kinetics of the formation of hydrogels were monitored by liquid NMR measurements. The formed hydrogels were shown to generate osmotic pressure up to 10.0 atm, indicating the potential of these hydrogels as efficient draw solutes in FO. Our results suggest that iodide anions are the osmotically active species in the system. Regeneration of the hydrogels via ultrafiltration (UF) was successfully achieved, allowing the development of a closed FO-UF process. However, the osmotic performances of the ionosilica hydrogels irreversibly decreased along the successive FO-UF cycles, probably due to anion exchange processes.

Defect Suppression in Oriented 2D Perovskite Solar Cells with Efficiency over 18% via Rerouting Crystallization Pathway

AbstractVertically oriented 2D perovskites exhibit promising optoelectronic properties and intrinsic stability, but their photovoltaic application is still limited by the low power conversion efficiency (PCE) compared to 3D analogs. Here, a new crystallization pathway (RCP) is reported to suppress defects in vertically oriented 2D perovskite caused by its over‐rapid self‐assembly behavior. By controlling the specific adsorption of an ammonium halide additive on different perovskite crystal planes, the dynamic preferred growth of (111) plane is intentionally restrained, and the minority (202) planes emerge as secondary nucleation sites to stimulate the creation of large grains. As the halogen‐regulated deprotonation of ammonium proceeds, the (111) crystal plane gradually recovers its growth dominance, and a vertically oriented 2D perovskite film finally forms with high homogeneity, reduced trap density of states, and desired carrier transport/collection kinetics. Solar cells using RCP‐2D films show a highly reproducible and stable PCE reaching 18.5% with a high fill factor of 83.4%. These findings provide critical missing information on simultaneously achieving highly oriented and less defective 2D perovskite films for excellent device performance.

Quasi-Living Copolymerization of Aryl Isocyanates and Epoxides.

Nontraditional polyurethane (PU) has been successfully synthesized by anionic copolymerization of some typical aryl isocyanates and epoxides with ammonium halide onium salt (Lewis base) as the initiator and triisobutylaluminum (Lewis acid) as the activator and the synergistic coordinator. In contrast to the traditional step-growth approach, this chain-growth copolymerization can maintain the anionic propagation site and exhibit some living features with a high activity, by which the copolymers synthesized have narrow molecular weight distributions and discrete end groups. The copolymer is primarily constituted by a urethane linkage, and the byproducts of isocyanurate trimer and oxazolidinone can be effectively suppressed as the polymerization proceeds. Density functional theory (DFT) calculations were also performed to support the proposed reaction mechanism.

Ring opening of methylenecyclopropanes with halides in liquid sulfur dioxide

Methylenecyclopropanes (MCP) undergo ring opening reactions with group I and II metal halides and ammonium halides in liquid SO2 to afford homoallylic halides, which are versatile reagents in organic synthesis. The developed reaction conditions are compatible with acid-labile substrates such as N-Boc-protected compounds. Liquid SO2 is a polar reaction medium with Lewis acid properties that solubilizes inorganic salts. The unique properties of SO2 were demonstrated by control experiments: 1) upon performing the reactions with the aforementioned salts in conventional solvents, the MCP ring opening was not observed either in the presence of catalytic amounts of H3PO4 (similar pKa to that of H2SO3), or in the absence of H3PO4; 2) a solution of SO2 in THF exhibited similar properties to that of liquid SO2.

Colloidal Bi-Doped Cs2Ag1-x Na x InCl6 Nanocrystals: Undercoordinated Surface Cl Ions Limit their Light Emission Efficiency.

Understanding and tuning the ligand shell composition in colloidal halide perovskite nanocrystals (NCs) has been done systematically only for Pb-based perovskites, while much less is known on the surface of Pb-free perovskite systems. Here, we reveal the ligand shell architecture of Bi-doped Cs2Ag1–xNaxInCl6NCs via nuclear magnetic resonance analysis. This material, in its bulk form, was found to have a photoluminescence quantum yield (PLQY) as high as 86%, a record value for halide double perovskites. Our results show that both amines and carboxylic acids are present and homogeneously distributed over the surface of the NCs. Notably, even for an optimized surface ligand coating, achieved by combining dodecanoic acid and decylamine, a maximum PLQY value of only 37% is reached, with no further improvements observed when exploiting post-synthesis ligand exchange procedures (involving Cs-oleate, different ammonium halides, thiocyanates and sulfonic acids). Our density functional theory calculations indicate that, even with the best ligands combination, a small fraction of unpassivated surface sites, namely undercoordinated Cl ions, is sufficient to create deep trap states, opposite to the case of Pb-based perovskites that exhibit much higher defect tolerance. This was corroborated by our transient absorption measurements, which showed that an ultrafast trapping of holes (most likely mediated by surface Cl-trap states) competes with their localization at the AgCl6 octahedra, from where, instead, they can undergo an optically active recombination yielding the observed PL emission. Our results highlight that alternative surface passivation strategies should be devised to further optimize the PLQY of double perovskite NCs, which might include their incorporation inside inorganic shells.

Surface Passivation of All‐Inorganic CsPbI2Br with a Fluorinated Organic Ammonium Salt for Perovskite Solar Cells with Efficiencies over 16%

Surface modification is demonstrated as an efficient strategy to enhance the efficiency and stability of perovskite solar cells (PVSCs). Fluorinated organic ammonium salts featuring a strong hydrophobic nature are seldom used as passivation agents for the surface modification of CsPbI2Br perovskites. Herein, a fluorinated organic ammonium halide salt, 4‐trifluoromethyl phenethylammonium iodide (CFPEAI), is incorporated into the surface of CsPbI2Br perovskite for the first time. After the CFPEAI modification, the defects of CsPbI2Br perovskite are significantly passivated with reduced trap densities. The best‐performance PVSC with CFPEAI modification shows an excellent power conversion efficiency (PCE) of 16.07% with a high fill factor (FF) of 84.65%, a short‐circuit current density (JSC) of 15.45 mA cm−2, and an open‐circuit voltage (VOC) of 1.23 V. In contrast, the control PVSCs without the surface modification exhibit a lower PCE of 14.50% with a FF of 80.56%, a JSC of 15.05 mA cm−2, and a VOC of 1.20 V. With CFPEAI passivation, the CsPbI2Br perovskite film exhibits enhanced hydrophobicity, thereby leading to improved stability for the corresponding PVSC in comparison with the control PVSC without any surface modification.

Antifungal Activity of β-Pinene-Based Hydronopyl Quaternary Ammonium Salts Against Phytopathogenic Fungi

β-Pinene can be used as a cheap source to synthesize a large number of high value-added derivatives. In this study, a series of β-pinene derivatives was prepared, and the antifungal activities of the compounds were assessed against phytopathogenic fungi. Eight N-alkyl hydronopyl diethyl ammonium halide salts were synthesized by the reaction of hydronopyl diethyl ammonium halide with 8 halogenated alkanes. The structures of the synthesized products were characterized by Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy and mass spectrometry. The antifungal activities of these derivatives were tested against 11 plant pathogens, and the preliminary structure-activity relationship is discussed. Some derivatives exhibited moderate to significant antifungal activity due to the fusion of the hydronopyl, a long-chain alkyl, bromine, and iodine anionic groups. In contrast to the structure-activity relationship of compounds 2a, 2b, and 2c, iodine ions in 2f, 2g, and 2f had a significant effect on enhancing the antifungal activity against Colletotrichum gloeosporioides, S clerotinia sclerotiorum, Phytophthora capsici, Phomopsis, Sphaeropsis sapinea, Glomerella cingulata, and Fusicoccum aesculi. A higher molecular weight could increase the antifungal activity against Fusarium proliferatum, Alternaria kikuchiana, Sclerotinia sclerotiorum, P. capsici, Phomopsis, and S. sapinea. Compounds 2d and 2e exhibited broad-spectrum antifungal activity against the tested strains. These derivatives are expected to be used as precursor molecules for novel pesticide development in further research.

High-Activity Organocatalysts for Polyether Synthesis via Intramolecular Ammonium Cation Assisted SN 2 Ring-Opening Polymerization.

This manuscript describes a kind of bifunctional organocatalyst with unprecedented reactivity for the synthesis of polyethers via ring-opening polymerization (ROP) of epoxides under mild conditions. The bifunctional catalyst incorporates two 9-borabicyclo[3.3.1]nonane centers on the two ends as Lewis acidic sites for epoxide activation and a quaternary ammonium halide in the middle as the initiating site. The catalyst could be easily prepared in two steps from commercially available stocks on up to kilogram scale with ≈100 % yield. The organoboron catalyst mediated ROP of epoxides displays living behavior with low catalyst loading (5 ppm) and enables the synthesis of polyethers with molecular weights of over a million grams per mole (>106 g mol-1 ). Based on the investigations on crystal structure of catalyst, MALDI-TOF, and 11 B NMR spectroscopy, an intramolecular ammonium cation assisted SN 2 mechanism is proposed and verified by DFT calculations.

High‐Activity Organocatalysts for Polyether Synthesis via Intramolecular Ammonium Cation Assisted SN2 Ring‐Opening Polymerization

AbstractThis manuscript describes a kind of bifunctional organocatalyst with unprecedented reactivity for the synthesis of polyethers via ring‐opening polymerization (ROP) of epoxides under mild conditions. The bifunctional catalyst incorporates two 9‐borabicyclo[3.3.1]nonane centers on the two ends as Lewis acidic sites for epoxide activation and a quaternary ammonium halide in the middle as the initiating site. The catalyst could be easily prepared in two steps from commercially available stocks on up to kilogram scale with ≈100 % yield. The organoboron catalyst mediated ROP of epoxides displays living behavior with low catalyst loading (5 ppm) and enables the synthesis of polyethers with molecular weights of over a million grams per mole (>106 g mol−1). Based on the investigations on crystal structure of catalyst, MALDI‐TOF, and 11B NMR spectroscopy, an intramolecular ammonium cation assisted SN2 mechanism is proposed and verified by DFT calculations.

Scalable Bifunctional Organoboron Catalysts for Copolymerization of CO2 and Epoxides with Unprecedented Efficiency.

The metallic catalyst-dominated alternating copolymerization of CO2 and epoxides has flourished for 50 years; however, the involved multistep preparation of the catalysts and the necessity to remove the colored metal residue in the final product present significant challenges in scalability. Herein, we report a series of highly active metal-free catalysts featured with an electrophilic boron center and a nucleophilic quaternary ammonium halide in one molecule for copolymerization of epoxides and CO2. The organocatalysts are easily scaled up to kilogram scale with nearly quantitative yield via two steps using commercially available stocks. The organocatalyst-mediated copolymerization of cyclohexane oxide and CO2 displays high activity (turnover frequency up to 4900 h-1) and >99% polycarbonate selectivity in a broad temperature range (25-150 °C) at mild CO2 pressure (15 bar). At a feed ratio of cyclohexane oxide/catalyst = 20 000/1, an efficiency of 5.0 kg of product/g of catalyst was achieved, which is the highest record achieved to date. The unprecedented activity toward CO2/epoxide copolymerization for our catalyst is a consequence of an intramolecular synergistic effect between the electrophilic boron center and the quaternary ammonium salt, which was experimentally ascertained by reaction kinetics studies, multiple control experiments, 11B NMR investigation, and the crystal structure of the catalyst. Density functional theory calculations further corroborated experimental conclusions and provided a deeper understanding of the catalysis process. The metal-free characteristic, scalable preparation, outstanding catalytic performances along with long-term thermostability demonstrate that the catalyst could be a promising candidate for large-scale production of CO2-based polymer.

Sulfur dioxide removal: An overview of regenerative flue gas desulfurization and factors affecting desulfurization capacity and sorbent regeneration.

Numerous mitigation techniques have been incorporated to capture or remove SO2 with flue gas desulfurization (FGD) being the most common method. Regenerative FGD method is advantageous over other methods due to high desulfurization efficiency, sorbent regenerability, and reduction in waste handling. The capital costs of regenerative methods are higher than those of commonly used once-through methods simply due to the inclusion of sorbent regeneration while operational and management costs depend on the operating hours and fuel composition. Regenerable sorbents like ionic liquids, deep eutectic solvents, ammonium halide solutions, alkyl-aniline solutions, amino acid solutions, activated carbons, mesoporous silica, zeolite, and metal-organic frameworks have been reported to successfully achieve high SO2 removal. The presence of other gases in flue gas, e.g., O2, CO2, NOx, and water vapor, and the reaction temperature critically affect the sorption capacity and sorbent regenerability. To obtain optimal SO2 removal performance, other parameters such as pH, inlet SO2 concentration, and additives need to be adequately governed. Due to its high removal capacity, easy preparation, non-toxicity, and low regeneration temperature, the use of deep eutectic solvents is highly feasible for upscale utilization. Metal-organic frameworks demonstrated highest reported SO2 removal capacity; however, it is not yet applicable at industrial level due to its high price, weak stability, and robust formulation.

Approaching Dissolved Species in Ammonoacidic GaN Crystal Growth: A Combined Solution NMR and Computational Study.

Solutions of gallium trihalides GaX 3 (X=F, Cl, Br, I) and their ammoniates in liquid ammonia were studied at ambient temperature under autogenous pressure by multinuclear (71Ga, 35Cl, 81Br) NMR spectroscopy. To unravel the role of pH, the analyses were done both in absence and in presence of ammonium halides, which are employed as mineralizers during ammonoacidic gallium nitride crystal growth. While gallium trifluoride and its ammoniate were found to be too sparingly soluble to give rise to a NMR signal, the spectra of solutions of the heavier halides reveal the presence of a single gallium‐containing species in all cases. DFT calculations and molecular dynamics simulations suggest the identification of this species as consisting of a [Ga(NH3)6]3+ cation and up to six surrounding halide anions, resulting in an overall trend towards negative complex charge. Quantitative 71Ga NMR studies on saturated solutions of GaCl3 containing various amounts of additional NH4Cl revealed a near linear increase of GaCl3 solubility with mineralizer concentration of about 0.023 mol GaCl3 per mol NH4Cl at room temperature. These findings reflect the importance of Coulombic shielding for the inhibition of oligomerization and precipitation processes and help to rationalize both the low solubility of gallium halides in neutral ammonia solution and, in turn, the proliferating effect of the mineralizer during ammonoacidic gallium nitride formation.

Surface Regulation of CsPbBr3 Quantum Dots for Standard Blue‐Emission with Boosted PLQY

AbstractIt is demonstrated that, via surface treatment of CsPbBr3 perovskite quantum dots (PeQDs) by introducing small amount of organic ammonium chlorides possessing short alkyl chain (C ≤ 4) in methyl acetate in the typical purification process, the emission can be tuned from green to blue region with boosted photoluminescence quantum yield (PLQY). The Cl− mainly works on the surface of PeQDs to fill bromide vacancy, which generates a passivated mixed‐halide surface and avoids formation of defects deep within bandgap. Meanwhile, the replacement of initial long‐chain ligands with short chain ammonium moiety benefits the film PLQY. Accordingly, a standard blue emission of 461 nm with a high film PLQY of 52% is accessed and the corresponding colloidal shows a PLQY of 80% at 456 nm. This method is also proved to be a versatile tool to boost the PLQY of PeQDs by using short chain ammonium halides bearing the same X with the initial CsPbX3. A near‐unity colloidal PLQY of 97% and 98% is achieved for CsPbBr3 and CsPbI3 respectively. Quantum dots light‐emitting diode (QLED) with treated CsPbBr3 affords a standard blue electroluminescence of 459 nm and a maximum external quantum efficiency of 0.3%.

Nanowire crystals of tantalum nitride grown in ammonium halide fluxes at high pressures

Nanowire crystals of a tantalum nitride phase have been grown from epsilon-tantalum nitride and ammonium halide precursors at high pressures exceeding several gigapascals. Synchrotron x-ray diffraction and Transmission Electron Microscopy (TEM) observations revealed that they had crystallized in an unreported hexagonal structure with lattice parameters of a = 3.050(1) Å and c = 2.909(2) Å. The one-dimensional growth orientation was along the crystallographic [001] direction. Scanning TEM–EDX elemental analyses showed that the nanowire crystals were composed of tantalum and nitrogen with small amounts of oxygen. The presence of the melted ammonium halides combined with supercritical ammonia acting as a reactive flux at high pressure and temperature played a significant role in the nanowire crystal growth. Raman spectroscopy performed on several single crystal nanowires pointed toward metallic properties, and the temperature dependence of the magnetization measured by Superconducting Quantum Interference Device magnetometry suggested a superconducting transition about 6.2 K. The analysis of the compression behavior revealed an incompressible nature, and the bulk modulus was determined to be 363(6) GPa.

Structural changes and band gap tunability with incorporation of n-butylammonium iodide in perovskite thin film

The current work presents structural change and band gap tunability using hybrid organic-inorganic perovskite with the incorporation of long chain ammonium halide. Thin films of MAPbI3 with different ratio of n-butylammonium iodide (BAI) have been successfully deposited on the substrate using a single step coating technique. X-ray diffraction scans revealed the transition of the 3D structure of MAPbI3 to quasi-2D perovskite structure when BAI loading increase with a crystallite size range approximately 16 nm. This structural changeis reflected in the band gap as it increased from 1.59 eV for bulk crystal MAPbI3 to 2.13 eV for BAI and MAPbI3 ratio of 1:1. Correspondingly, photoluminescence measurement showed a blue shift in perovskite emission due to the transition of 3D to 2D layered structure perovskite. Raman spectra confirm that all fabricated films are of pristine quality and no corresponding degradation peaks of PbI2 is observed. These characteristics are important to address the single step deposition method of hybrid perovskite for perovskite solar cells application.

Templated growth of oriented layered hybrid perovskites on 3D-like perovskites

The manipulation of crystal orientation from the thermodynamic equilibrium states is desired in layered hybrid perovskite films to direct charge transport and enhance the perovskite devices performance. Here we report a templated growth mechanism of layered perovskites from 3D-like perovskites which can be a general design rule to align layered perovskites along the out-of-plane direction in films made by both spin-coating and scalable blading process. The method involves suppressing the nucleation of both layered and 3D perovskites inside the perovskite solution using additional ammonium halide salts, which forces the film formation starts from solution surface. The fast drying of solvent at liquid surface leaves 3D-like perovskites which surprisingly templates the growth of layered perovskites, enabled by the periodic corner-sharing octahedra networks on the surface of 3D-like perovskites. This discovery provides deep insights into the nucleation behavior of octahedra-array-based perovskite materials, representing a general strategy to manipulate the orientation of layered perovskites.

Host–Guest Interactions of Sodiumsulfonatomethyleneresorcinarene and Quaternary Ammonium Halides: An Experimental–Computational Analysis of the Guest Inclusion Properties

The molecular recognition of nine quaternary alkyl- and aryl-ammonium halides (Bn) by two different receptors, Calkyl-tetrasodiumsulfonatomethyleneresorcinarene (An), were studied in solution using...

Quasi-2D organic cation-doped formamidinium lead bromide (FAPbBr3) perovskite light-emitting diodes by long alkyl chain

Abstract Organic-inorganic hybrid perovskites (OIHP) are promising materials for high efficiency light emitting diode (LEDs) due to their high color purity, their high photo-luminescence quantum yield and their bandgap tuneability. Introducing long chain ammonium halide in a perovskite films can result in energy funneling from a distribution of two-dimensional perovskite nanosheets to three-dimensional nanocrystals through energy cascade from high bandgap energy states (nanosheets) to lower bandgap energy states (nanocrystals), or enhance the passivation of the 3D nanocrystals. Thus, the electrical charge injection in the emitter site is enhanced or the non-radiative recombination rate is reduced. Here we report on the doping of a FAPbBr3 green-emitter with n-BABr (butyl ammonium bromide). Upon addition of a small amount of n-BABr (0.2 wt%) in a non-stoichiometric perovskite solution, the photoluminescence intensity of thin films and current efficiency of PeLEDs increase by about an order of magnitude, from 1.2 Cd/A without to 13.5 Cd/A with n-BABr doping.

Effect of Annealing Time and Heat Flux on Solvothermal Synthesis of CIGS Nanoparticles

Abstract CuInxGa(1-x)Se2 (CIGS) is a renowned absorbing material in solar cell application due to its wide and tunable direct bandgap with high absorption coefficient. The highest efficiency achieved on lab scale device is 22.6% which is competitive to Si based solar cells. CIGS nanoparticles are prominent materials for solar photovoltaic applications due to its high surface to volume ratio and for its use in relatively low processing temperature. In the study, CIGS nanoparticles are synthesized using modified solvothermal method in which the size and agglomeration of CIGS nanoparticles are controlled by introducing ammonium halides. The formation mechanism of CIGS nanoparticles while heating at 230 °C in hot air oven and in muffle furnace for various time durations are studied and analysed in detailed. The crystal phase and crystallite size are evaluated using X-ray diffraction and the phase is confirmed by Raman spectroscopy. The synthesized CIGS nanoparticles from 5 hours and 7 hours of reaction time exhibited tetragonal chalcopyrite crystal structure with an average crystallite size of 41 nm in hot air oven and 125 nm in furnace. The optical band gap of the CIGS nanoparticles measured by UV-Vis-NIR spectroscopy is found to be 1.52 eV for 5 hours and 1.56 eV for 7 hours of reaction time in both oven and furnace prepared samples, that indicates the quality of material is high and could be used for photovoltaic device fabrication.

Aluminum porphyrins with quaternary ammonium halides as catalysts for copolymerization of cyclohexene oxide and CO2: metal-ligand cooperative catalysis.

Bifunctional AlIII porphyrins with quaternary ammonium halides, 2-Cl and 2-Br, worked as excellent catalysts for the copolymerization of cyclohexene oxide (CHO) and CO2 at 120 °C. Turnover frequency (TOF) and turnover number (TON) reached 10 000 h-1 and 55 000, respectively, and poly(cyclohexene carbonate) (PCHC) with molecular weight of up to 281 000 was obtained with a catalyst loading of 0.001 mol%. In contrast, bifunctional MgII and ZnII counterparts, 3-Cl and 4-Cl, as well as a binary catalyst system, 1-Cl with bis(triphenylphosphine)iminium chloride (PPNCl), showed poor catalytic performances. Kinetic studies revealed that the reaction rate was first-order in [CHO] and [2-Br] and zero-order in [CO2], and the activation parameters were determined: ΔH ‡ = 12.4 kcal mol-1, ΔS ‡ = -26.1 cal mol-1 K-1, and ΔG ‡ = 21.6 kcal mol-1 at 80 °C. Comparative DFT calculations on two model catalysts, AlIII complex 2' and MgII complex 3', allowed us to extract key factors in the catalytic behavior of the bifunctional AlIII catalyst. The high polymerization activity and carbonate-linkage selectivity originate from the cooperative actions of the metal center and the quaternary ammonium cation, both of which facilitate the epoxide-ring opening by the carbonate anion to form the carbonate linkage in the key transition state such as TS3b (ΔH ‡ = 13.3 kcal mol-1, ΔS ‡ = -3.1 cal mol-1 K-1, and ΔG ‡ = 14.4 kcal mol-1 at 80 °C).