Ammonium Halides Research Articles

Nondestructive and quick differentiation between loupe-clean low-alkali natural and hydrothermal synthetic aquamarines: Constraints of infrared spectroscopy

A considerable increase in the price of natural aquamarine has led to the emergence of hydrothermal synthetic aquamarine as a cheap substitute in the market. In this study, comparative analysis was conducted between natural aquamarine obtained from Altay Prefecture in Xinjiang, China, and hydrothermal synthetic aquamarine in the Chinese market to distinguish them with loupe-clean clarity. Nondestructive tests including microscopic observation, X-ray fluorescence spectroscopy, infrared spectroscopy, ultraviolet–visible–near-infrared spectroscopy, and Raman spectroscopy were conducted. The two samples were low-alkali aquamarine, dominated by type Ⅰ H2O, and the infrared spectra showed similar water-related peaks, exhibiting weak absorption bands related to Cl− at 2736 and 2449 cm−1 and CO2 in the crystal channels at 2358 cm−1. Apart from the strong irregular and distinctive growth patterns, infrared absorption bands at 3313 and 4060 cm−1 due to the N–H bond (derived from ammonium halide used in crystal growth) vibrations were found to be present only in hydrothermal synthetic aquamarine. This study reveals implications for identifying hydrothermal synthetic aquamarine when the internal features of loupe-clean aquamarine are not obvious.

Structural phase transition in NH₄F under extreme pressure conditions.

Ammonium fluoride (NH₄F) exhibits a variety of crystalline phases depending on temperature and pressure. By employing Raman spectroscopy and synchrotron X-ray diffraction beyond megabar pressures (up to 140 GPa), we have here observed a novel dense solid phase of NH₄F, characterised by the tetragonal P4/nmm structure also observed in other ammonium halides under less extreme pressure conditions, typically a few GPa. Using detailed ab-initio calculations and reevaluating earlier theoretical models pertaining to other ammonium halides, we examine the microscopic mechanisms underlying the transition from the low-pressure cubic phase (P-43m) to the newly identified high-pressure tetragonal phase (P4/nmm). Notably, NH₄F exhibits distinctive properties compared to its counterparts, resulting in a significantly broader pressure range over which this transition unfolds, facilitating the identification of its various stages. Our analysis points to a synergistic interplay driving the transition to the P4/nmm phase, which we name phase VIII. At intermediate pressures (around 40 GPa), a displacive transition of fluorine ions initiates a tetragonal distortion of the cubic phase. Subsequently, at higher pressures (around 115 GPa), every second ammonium ion undergoes a rotational shift, adopting an anti-tetrahedral arrangement. This coupled effect orchestrates the transition process, leading to the formation of the tetragonal phase.

Abundances of trace constituents in Jupiter’s atmosphere inferred from Herschel/PACS observations

Context. On October 31, 2009, the Photodetector Array Camera and Spectrometer (PACS) on board the Herschel Space Observatory observed far-infrared spectra of Jupiter in the wavelength range between 50 and 220 µm as part of the program “Water and Related Chemistry in the Solar System”. The spectra have an effective spectral resolution between 900 and 3500, depending on the wavelength and grating order. Aims. We investigate the disk-averaged chemical composition of Jupiter’s atmosphere as a function of height using these observations. Methods. We used the Planetary Spectrum Generator and the least-squares fitting technique to infer the abundances of trace constituents. Results. The PACS data include numerous spectral lines attributable to ammonia (NH3), methane (CH4), phosphine (PH3), water (H2O), and deuterated hydrogen (HD) in the Jovian atmosphere and probe the chemical composition from p ~ 275 mbar to p ~ 900 mbar. From the observations, we infer an ammonia abundance profile that decreases from a mole fraction of (1.7 ± 0.8) × 10−4 at p ~ 900 mbar to (1.7 ± 0.9) × 10−8 at p ~ 275 mbar, following a fractional scale height of about 0.114. For phosphine, we find a mole fraction of (7.2 ± 1.2) × 10−7 at pressures higher than (550 ± 100) mbar and a decrease of its abundance at lower pressures following a fractional scale height of (0.09 ± 0.02). Our analysis delivers a methane mole fraction of (1.49 ± 0.09) × 10−3. Analyzing the HD R(0) line at 112.1 µm yields a new measurement of Jupiter’s D/H ratio, D/H = (1.5 ± 0.6) × 10−5. Finally, the PACS data allow us to put the most stringent 3σ upper limits yet on the mole fractions of hydrogen halides in the Jovian troposphere. These new upper limits are <1.1 × 10−11 for hydrogen fluoride (HF), <6.0 × 10−11 for hydrogen chloride (HCl), <2.3 × 10−10 for hydrogen bromide (HBr) and <1.2 × 10−9 for hydrogen iodide (HI) and support the proposed condensation of hydrogen halides into ammonium halide salts in the Jovian troposphere.

Synthesis and Evaluation of Ph and Temperature Stimuli-Responsive Magnetic Nanohydrogels for Gene Delivery

The offer of gene delivery technologies as a promising approach to treating diverse diseases has revolutionized human medicine during the last two decades. So, the application of suitable vectors, particularly polymers with substrates with unique physicochemical properties for the transfer of targeted genes to logical sites for effective treatment, plays an indispensable role for more personalized medicine and improves the safety profile in response to continuing to use new medical technologies. For this purpose, we synthesized nanocarriers with a two-block cationic hydrogel, magnetic and non-magnetic, based on N-isopropyl acrylamide (NIPAM) and quaternary alkyl ammonium halide salts of DMAEMA (DMAEMAQ) with pH and temperature responsiveness via the free radical polymerization technique. The bulk properties of these co-polymers were characterized by using Fourier transform infrared spectroscopy, 1H NMR spectroscopy, Zeta potential, lower critical solution temperature (LCST), and gel electrophoresis to show the loading of nanoparticles with the gene. In the results, magnetic P[NIPAM-DMAEMAQ] hydrogel showed controllable responsive properties determined by the nature of the cationic charge +24.7 mV incorporated, nanosize around 86.95 and 91.22 nm, and efficiency loaded with the gene more than 95%. As well, the synthesized nanohydrogel exhibited a sharp volume-phase transition in water at a LCST of ∼40 °C. So, the combination of both monomers yielded an interesting system with high transfection efficiency and compliant biocompatibility characteristics, which could effectively achieve gene loading. Also, the magnetic potential of nanohydrogel was determined as a vector to deliver genes to localized sites. Notably, the synthesized combination P[NIPAM-DMAEMAQ] nanohydrogel has been considered a transfection of the biodegradable and biocompatible magnetic nanoparticle sensitive to tunable pH and temperature responsiveness, demonstrating that it will hold a promising approach as a potential carrier to improve gene delivery therapeutic efficacy in cancer and different disease treatments.

Phenylethylammonium iodide induced “in situ healing” behavior for carbon-electrode basing, hole-conductor-free perovskite solar cells

Previous study showed that blending octylammonium iodide (OAI) in a carbon paste induced a kind of in situ healing effect for carbon-electrode basing, hole-conductor-free, planar perovskite solar cells. Here, the strategy is re-examined by considering another kind of ammonium halide molecule or phenethylammonium iodide (PEAI). It is observed that, after moderate PEAI blending, power conversion efficiency of devices rises from 11.56 (±0.82)% to 15.77 (±0.53)% (championed at ∼17.9%), with open-circuit voltage increasing from 969 (±28) to 1033 (±13) mV, and fill factor increasing from 51.17 (±2.68)% to 65.71 (±1.36)%. The improved device efficiency is due to the retarded charge recombination and the improved charge transfer processes. Transient photovoltage/photocurrent decay curve tests show that, after PEAI blending, lifetime of charge carriers in device increases from 3.21 to 5.67 μs, while the charge extraction time decreases from 2.99 to 2.18 μs. Moreover, built-in potential rises according to the Mott–Schottky study. A designated “penetration-reaction” test reveals that PEAI could also induce the in situ healing effect, which accounts for the improved charge transfer/recombination processes. The study could tell the universality of this strategy to certain extent.

Peptide‐Based Ammonium Halide with Inhibited Deprotonation Enabling Effective Interfacial Engineering for Highly Efficient and Stable FAPbI3 Perovskite Solar Cells

AbstractAmmonium iodides are intensively investigated as effective interfacial passivation agents in perovskite solar cells (PSCs) while facing a major challenge of their high reactivity with perovskites that undermines the operational stability of the PSCs. Exemplified by involving rationally designed/selected peptide into the widely adopted phenethylammonium iodide (PEAI), the present work demonstrates that the bespoke peptide‐PEAI can effectively inhibit the deprotonation of ammonium iodides and thus hinder the formation of 2D perovskite, facilitating the stability enhancement in perovskite films by multi hydrogen bonding. The additional lone pair electrons provided by peptide molecules can also enhance the passivation ability of the modified layer. Attributed to the stable co‐modifier peptide‐PEAI, the small‐area FAPbI3‐based PSCs yield a high efficiency of 25.02% with robust light and thermal stabilities. Moreover, the peptide‐PEAI‐based minimodules with an efficiency of 19.06% for a total area of 36 cm2 manifested the great application potential of this co‐modification strategy in the perovskite photovoltaics.

Porous isoreticular non-metal organic frameworks

Metal–organic frameworks (MOFs) are useful synthetic materials that are built by the programmed assembly of metal nodes and organic linkers1. The success of MOFs results from the isoreticular principle2, which allows families of structurally analogous frameworks to be built in a predictable way. This relies on directional coordinate covalent bonding to define the framework geometry. However, isoreticular strategies do not translate to other common crystalline solids, such as organic salts3–5, in which the intermolecular ionic bonding is less directional. Here we show that chemical knowledge can be combined with computational crystal-structure prediction6 (CSP) to design porous organic ammonium halide salts that contain no metals. The nodes in these salt frameworks are tightly packed ionic clusters that direct the materials to crystallize in specific ways, as demonstrated by the presence of well-defined spikes of low-energy, low-density isoreticular structures on the predicted lattice energy landscapes7,8. These energy landscapes allow us to select combinations of cations and anions that will form thermodynamically stable, porous salt frameworks with channel sizes, functionalities and geometries that can be predicted a priori. Some of these porous salts adsorb molecular guests such as iodine in quantities that exceed those of most MOFs, and this could be useful for applications such as radio-iodine capture9–12. More generally, the synthesis of these salts is scalable, involving simple acid–base neutralization, and the strategy makes it possible to create a family of non-metal organic frameworks that combine high ionic charge density with permanent porosity.

Hypersensitive Inhibition of Organocatalysts by Halide Salts: Are Two Catalysts Involved in the Mannich Reaction?

AbstractConformationally flexible tertiary amine – thiourea−urea catalysts 1 and 2 for the Mannich reaction between imines and malonate esters are efficiently inhibited by quaternary ammonium halides. NMR titrations, isothermal titration calorimetry (ITC) and NOE experiments showed that the catalysts bind chloride and bromide ions with relatively high affinities (K=103–105 M−1 in acetonitrile). The halide ions not only block the active site of the catalysts, but they also induce refolding into catalytically inactive conformations upon complexation in an allosteric‐like event. At substoichiometric inhibitor:catalyst ratios, the catalysts displayed hypersensitivity to the inhibitors, with overall rates that were lower than those expected from simple 1st order kinetics and 1 : 1 inhibitor:catalyst stoichiometry. To rationalize the observed hypersensitivity, different kinetic scenarios were examined. For catalyst 2 and the Takemoto catalyst (6), the data is consistent with 2nd order dependency on catalyst concentration, suggesting that a mechanism involving only a single catalyst in the catalytic cycle is not operative. For catalyst 1, an alternative scenario involving 1st order in catalyst and catalyst poisoning at low concentrations of 1 could also rationalize the hypersensitivity. Interestingly, inhibition of catalysts 1 and 2 by halide salts led to significant loss of enantioselectivity, in contrast to the Takemoto catalyst 6 which was inhibited but with essentially no change in enantioselectivity.

Eliminating the Adverse Impact of Composition Modulation in Perovskite Light-Emitting Diodes toward Ultra-High Brightness and Stability.

Excess ammonium halides as composition additives are widely employed in perovskite light-emitting diodes (PeLEDs), aiming to achieve high performance by controlling crystallinity and passivating defects. However, an in-depth understanding of whether excess organoammonium components affect the film physical/electrical properties and the resultant device instability is still lacking. Here, the trade-off between the performance and stability in high-efficiency formamidinium lead iodide (FAPbI3)-based PeLEDs with excess ammonium halides is pointed, and the underlying mechanism is explored. Systematic experimental and theoretical studies reveal that excess halide salt-induced ion-doping largely alters the PeLEDs properties (e.g., carrier injection, field-dependent ion-drifting, defect physics, and phase stability). A surface clean assisted cross-linking strategy is demonstrated to eliminate the adverse impact of composition modulation and boost the operational stability without sacrificing the efficiency, achieving a high efficiency of 23.6%, a high radiance of 964 W sr-1 m-2 (The highest value for FAPbI3 based PeLEDs), and a prolong lifetime of 106.1 h at large direct current density (100mA cm-2), concurrently. The findings uncovered an important link between excess halide salts and the device performance, providing a guideline for rational design of stable, bright, and high efficiency PeLEDs.

Tailoring Perovskite Surface Potential and Chelation Advances Efficient Solar Cells.

Modifying perovskite surface using various organic ammonium halide cations has proven to be an effective approach for enhancing the overall performance of perovskite solar cells. Nevertheless, the impact of the structural symmetry of these ammonium halide cations on perovskite interface termination has remained uncertain. Here, this work investigates the influence of symmetry on the performance of the devices, using molecules based on symmetrical bis(2-chloroethyl)ammonium cation (B(CE)A+) and asymmetrical 2-chloroethylammonium cation (CEA+) as interface layers between the perovskite and hole transport layer. These results reveal that the symmetrical B(CE)A+ cations lead to a more homogeneous surface potential and more comprehensive chelation with uncoordinated Pb2+ compared to the asymmetrical cations, resulting in a more favorable energy band alignment and strengthened defect healing. This strategy, leveraging the spatial geometrical symmetry of the interface cations, promotes hole carrier extraction between functional layers and reduces nonradiative recombination on the perovskite surface. Consequently, perovskite solar cells processed with the symmetrical B(CE)A+ cations achieve a power conversion efficiency (PCE) of 25.60% and retain ≈91% of their initial PCE after 500 h of maximum power point operation. This work highlights the significant benefits of utilizing structurally symmetrical cations in promoting the performance and stability of perovskite solar cells.

A comparative study of surface passivation of p-i-n perovskite solar cells by phenethylammonium iodide and 4-fluorophenethylammonium iodide for efficient and practical perovskite solar cells with long-term reliability

Passivation of the defective surface in perovskite absorber layers effectively stabilizes the photovoltaic performance and electronic properties of perovskite solar cells (PSCs). We herein investigated the passivating effects of phenethylammonium iodide (PEAI) and 4-fluorophenethylammonium iodide (F-PEAI) on perovskite absorber layers comparatively, analyzing their impact on morphological, optical, and electrical properties of perovskite absorbers. Both passivation molecules significantly improved film characteristics, with enlarged domain size, uniform surface morphologies, and prolonged carrier lifetime observed in polycrystalline perovskite absorbers. Notably, non-fluorinated PEAI demonstrated superior effectiveness in reducing tail states and defective Pb2+ sites, resulting in more stable absorbers with fewer defects. The passivated perovskite absorbers exhibited higher champion efficiencies (22.07% for PEAI and 20.56% for F-PEAI) compared to control devices (19.53%), attributed to the suppression of interfacial nonradiative recombination and reduction in recombination energy losses. The devices with passivated perovskite absorbers also demonstrated promising indoor photovoltaic performance, achieving an efficiency of 39.04% and 37.02% under dim-light conditions (LED, 6500 K, 1000 Lux), compared to 29.43% in the control device. Importantly, the passivated absorbers maintained 94% of their initial efficiency even after 1250 hours of humidity aging, indicating enhanced hydrophobicity and reduced trap states, resulting in good ambient stability. Our findings highlight the effectiveness of passivation techniques using organic ammonium halide salts in improving the efficiency and stability of perovskite solar cells.

High‐Performance Perovskite Solar Cells with Zwitterion‐Capped‐ZnO Quantum Dots as Electron Transport Layer and NH4X (X = F, Cl, Br) Assisted Interfacial Engineering

The systematic advances in the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs) have been driven by the developments of perovskite materials, electron transport layer (ETL) materials, and interfacial passivation between the relevant layers. While zinc oxide (ZnO) is a promising ETL in thin film photovoltaics, it is still highly desirable to develop novel synthetic methods that allow both fine‐tuning the versatility of ZnO nanomaterials and improving the ZnO/perovskite interface. Among various inorganic and organic additives, zwitterions have been effectively utilized to passivate the perovskite films. In this vein, we develop novel, well‐characterized betaine‐coated ZnO QDs and use them as an ETL in the planar n‐i‐p PSC architecture, combining the ZnO QDs‐based ETL with the ZnO/perovskite interface passivation by a series of ammonium halides (NH4X, where X = F, Cl, Br). The champion device with the NH4F passivation achieves one of the highest performances reported for ZnO‐based PSCs, exhibiting a maximum PCE of ~22% with a high fill factor of 80.3% and competitive stability, retaining ~78% of its initial PCE under 1 Sun illumination with maximum power tracking for 250 h.

Low pressure reversibly driving colossal barocaloric effect in two-dimensional vdW alkylammonium halides

Plastic crystals as barocaloric materials exhibit the large entropy change rivalling freon, however, the limited pressure-sensitivity and large hysteresis of phase transition hinder the colossal barocaloric effect accomplished reversibly at low pressure. Here we report reversible colossal barocaloric effect at low pressure in two-dimensional van-der-Waals alkylammonium halides. Via introducing long carbon chains in ammonium halide plastic crystals, two-dimensional structure forms in (CH3–(CH2)n-1)2NH2X (X: halogen element) with weak interlayer van-der-Waals force, which dictates interlayer expansion as large as 13% and consequently volume change as much as 12% during phase transition. Such anisotropic expansion provides sufficient space for carbon chains to undergo dramatic conformation disordering, which induces colossal entropy change with large pressure-sensitivity and small hysteresis. The record reversible colossal barocaloric effect with entropy change ΔSr ~ 400 J kg−1 K−1 at 0.08 GPa and adiabatic temperature change ΔTr ~ 11 K at 0.1 GPa highlights the design of novel barocaloric materials by engineering the dimensionality of plastic crystals.

Synthesis of Bifunctional Catalysts for the Cycloaddition of CO2 to Epoxides through an Epoxide‐Driven Strategy

AbstractThe design of molecular scaffolds bearing multiple functional groups for the activation and ring‐opening of epoxides is a crucial challenge for the synthesis of efficient homogeneous and heterogeneous catalysts that are used for the cycloaddition reaction of CO2 to epoxides. Traditional approaches to prepare such multifunctional catalysts often imply multistep synthetic procedures and expensive building blocks. In this work we show that bifunctional catalysts for the cycloaddition of CO2 to epoxides bearing a Lewis acid metal and a quaternary ammonium halide group can be prepared in just two steps starting from an opportunely designed epoxide precursor by using inexpensive substrates. Such a readily accessible catalyst was applied for the cycloaddition of CO2 to a series of epoxides under atmospheric conditions generally leading to quantitative substrate conversion and high carbonate selectivities. Importantly, we also show that the epoxide‐driven concept developed for the preparation of the molecular catalyst, could be applied to prepare recyclable heterogeneous systems for the target cycloaddition reaction.

Direct Dearomatization of Quinoline/Isoquinoline Ammonium Halides to Construct N‐Substituted Tetrahydroquinolines and Tetrahydroisoquinolines

AbstractDearomatization of quinoline/isoquinoline quaternary ammonium salts to synthesize valuable tetrahydroquinolines was firstly reported. Under this method, we used phenylsilane as a reducing agent to prepare a series of tetrahydroquinoline and tetrahydroisoquinoline derivatives conveniently and quickly in moderate to good yields. This method showed good functional group tolerance, wide substrate range, mild reaction conditions and simple operation.

Ammonium halide selective ion pair recognition and extraction with a chalcogen bonding heteroditopic receptor.

The first example of a heteroditopic receptor capable of cooperative recognition and extraction of ammonium salt (NH4X) ion-pairs is described. Consisting of a bidentate 3,5-bis-tellurotriazole chalcogen bond donor binding cleft, the appendage of benzo-15-crown-5 (B15C5) substituents to the tellurium centres facilitates binding of the ammonium cation via a co-facial bis-B15C5 sandwich complex, which serves to switch on chalcogen bonding-mediated anion binding potency. Extensive quantitative ion-pair recognition 1H NMR titration studies in CD3CN/CDCl3 (1 : 1, v/v) solvent media reveal impressive ion-pair binding affinities towards a variety of ammonium halide, nitrate and thiocyanate salts, with the heteroditopic receptor displaying notable ammonium halide salt selectivity. The prodigious solution phase NH4X recognition also translates to efficient solid-liquid and liquid-liquid extraction capabilities.

Photoelectrochemical synthesis of 4-halomethyl benzoxazines with a halogen anion source

A mild and efficient protocol for preparing 4-halomethyl benzoxazines via a photoelectrochemical process with ammonium halide as the halogenating reagent was developed.

Halide-free CO2 cycloaddition onto styrene oxide catalysed by first row transition-metal derivatives of polyoxotungstates.

Quaternary ammonium salts of metal derivatives of polyoxometalates [XW11O39M(H2O)]n- (X = P, Si; M = Cr, Mn, Co, Ni, Zn) were successfully tested instead of quaternary ammonium halides as catalysts in the cycloaddition of CO2 to styrene oxide. Remarkably, they gave very satisfactory yields of styrene carbonate at moderate temperature (80 °C).

Scalable and adaptable two-ligand co-solvent transfer methodology for gold bipyramids to organic solvents.

Large and faceted nanoparticles, such as gold bipyramids, presently require synthesis using alkyl ammonium halide ligands in aqueous conditions to stabilize the structure, which impedes subsequent transfer and suspension of such nanoparticles in low polarity solvents despite success with few nanometer gold nanoparticles of shapes such as spheres. Phase transfer methodologies present a feasible avenue to maintain colloidal stability of suspensions and move high surface energy particles into organic solvent environments. Here, we present a method to yield stable suspensions of gold bipyramids in low-polarity solvents, including methanol, dimethylformamide, chloroform, and toluene, through the requisite combination of two capping agents and the presence of a co-solvent. By utilizing PEG-SH functionalization for stability, dodecanethiol (DDT) as the organic-soluble capping agent, and methanol to aid in the phase transfer, gold bipyramids with a wide-range of aspect ratios and sizes can be transferred between water and chloroform readily and maintain colloidal stability. Subsequent transfer to various organic and low-polarity solvents is then demonstrated for the first time.

Towards metal-free supported quaternary ammonium halide catalysts for an optimized cycloaddition of CO2 onto styrene oxide

Quaternary ammonium salts covalently immobilized on mesoporous silica were found efficient catalysts for CO2 cycloaddition onto styrene oxide under various conditions, including solvent-free conditions and/or in the absence of metal catalysts.