Ammonium Iodine Research Articles

Differentially Accelerated Electron and Hole Diffusion in MAPbI3 Film Surface Treated by a Quaternary Ammonium Halide for High‐Efficiency Solar Cells

Surface treatment with moisture‐tolerant molecules is an effective approach for improving the long‐term stability of perovskite solar cells (PSCs), but may bring drawbacks to carrier dynamics and power conversion efficiency (PCE). Although PSCs with both high stability and PCE have been realized by specially designed molecules recently, the underlying mechanism boosting the superior PCE is still not clear, limiting the further optimization of the photovoltaic performances. Herein, by monitoring carrier dynamics in tetra‐ethyl ammonium iodine (TEAI)‐treated MAPbI3 using femtosecond transient reflectivity technique with the rationally selected pump‐probe wavelengths, the electron and hole diffusivities are found being 7 and 3 times faster than those in the pristine MAPbI3, respectively. The differentially enhanced electron and hole diffusivity and the associated charge separation might originate from TEAI, which can effectively passivate both the negatively and positively charged defects. This study indicates that quaternary ammonium halide might be an efficient tool for improving both moisture stability and PCE of perovskites due to its hydrophobic organic cations ready to anchor along the surface and anions with a deeper penetration.

Synthesis, characterization, and evaluation of quaternary ammonium-based polymerizable antimicrobial monomers for prosthodontic applications

The present study aims to synthesize and characterize two quaternary ammonium (QAM) based monomers such as - dimethyl-hexadecyl-methacryloxyethyl-ammonium iodide (DHMAI) and 2-dimethyl-2-dodecyl-1-methacryloxyethyl ammonium iodine (DDMAI) and assess their cytotoxicity and antimicrobial properties. The study also aims to incorporate the optimized concentration of these monomers as copolymerizing monomers into conventional Polymethyl methacrylate (PMMA) denture base resin and evaluate their suitability for prosthetic applications. DHMAI and DDMAI monomers were synthesized through a Menschutkin reaction and their chemical structure was characterized using FT-IR and 1H-NMR spectroscopy. Cytotoxicity was determined using Methyl Thiazolyl Tetrazolium (MTT) assay whereas antimicrobial activity was assessed using the agar-disc diffusion method. Subsequently, optimized concentrations of DHMAI or DDMAI, based on the cytotoxicity results, were added to conventional PMMA resin. Antimicrobial activity, cytotoxicity, surface hardness, and water sorption of PMMA denture base rein incorporated with DHMAI or DDMAI were evaluated. FT-IR and 1H-NMR results confirmed the structure of monomers and copolymerization of DHMAI and DDMAI with PMMA resin. DHMAI and DDMAI monomers were found to be cytocompatible with mouse fibroblast cells up to a concentration of 5 μg/mL and 20 μg/mL respectively. In addition, incorporation of DHMAI or DDMAI at 5 μg/mL and 20 μg/mL respectively into PMMA denture base material did not affect their cytocompatibility. PMMA denture base resin incorporated with DHMAI or DDMAI significantly reduced the adhesion of microbes. Further, an increase in the surface hardness and a reduction in the water sorption was observed. Hence DHMAI and DDMAI can be considered as potential candidates for imparting antimicrobial activity to polymeric denture base materials.

Regioselective Approach to β-Peroxyl Alcohols and Ethers from Alkenes.

A different regioselective three-component reaction of alkenes, oxygen sources, and hydroperoxides mediated by ammonium iodine to α-oxyperoxidates has been developed. Mechanistic studies demonstrated that regioselective radical addition and subsequent SN2 nucleophilic substitution were possible for the formation of products. In addition to the traditional pathway of SN2 reaction, that is, where nucleophiles attack the α-C atoms at the back side, an additional unusual transition configuration with the H2O molecule attacking the α-C atom at the front side was obtained.

The Effect of Lead Halide on Characterization of Methyl Ammonium Iodine MAI2 Perovskite

A hybrid method is proposed to synthesize methylammonium lead iodine, bromine and chlorine MAPbI3, MAPbBr2I and MAPbCl2I Perovskite by mixing two-step methods. The descriptions of perovskite samples included structural, morphological and optical properties. The intensity and orientation in X-ray diffraction (XRD) patterns appear clearly and squeaky. FESEM images of the perovskite films appeared as a rough surface due to iodine and more crystalline size using bromine and chlorine. Optical properties shifted towards low wavelengths (blue shift) and the value changed from 830 nm to 420 nm when the lead halide is changed from iodine to bromine and then to chlorine.

Enhanced performance of poly(olefin)-based anion exchange membranes cross-linked by triallylmethyl ammonium iodine and divinylbenzene

Anion exchange membrane fuel cell (AEMFC) can be a viable technology to help combat global warming as they are clean energy conversion devices. Herein, a novel series of poly(olefin)-based anion exchange membranes (AEMs) comprising quaternary ammonium (QA) cations are designed and prepared successfully through ultraviolet cross-linking of olefin monomers, followed by an anion exchange reaction. Triallylmethyl ammonium iodine ([TAMA][I]) is synthesized and used both as a conductive group and a flexible cross-linker. Divinylbenzene (DVB) is used as a rigid cross-linker in the preparation of poly(olefin)-based membranes, and the poly(olefin)-based membranes exhibit robust alkaline stability because of their ether-free backbone. The content of rigid non-conductive DVB in poly(olefin)-based AEMs can be reduced by introducing [TAMA][I], leading to the improved conductivity and cell performance of the AEMs. The [PSAN]60-[TAMA][OH]40-1 membrane possesses a high conductivity of 51.30 mS cm−1 at 80 °C, which is higher than that of [PSAN]60-[TAMA][OH]40–4 (30.11 mS cm−1). The H2/O2 fuel cell assembled with [PSAN]60-[TAMA][OH]40–1 exhibit higher peak power density (266 mW cm−2, 60 °C) than the one assembled with [PSAN]60-[TAMA][OH]40–4 (83 mW cm−2). The results show that it is a facile, inexpensive, and commercially viable approach to the preparation of poly(olefin)-based AEMs.

Critical role of additive-induced molecular interaction on the operational stability of perovskite light-emitting diodes

Summary Despite rapid improvements in efficiency and brightness of perovskite light-emitting diodes (PeLEDs), the poor operational stability remains a critical challenge hindering their practical applications. Here, we demonstrate greatly improved operational stability of high-efficiency PeLEDs, enabled by incorporating dicarboxylic acids into the precursor for perovskite depositions. We reveal that the dicarboxylic acids efficiently eliminate reactive organic ingredients in perovskite emissive layers through an in situ amidation process, which is catalyzed by the alkaline zinc oxide substrate. The formed stable amides prohibit detrimental reactions between the perovskites and the charge injection layer underneath, stabilizing the perovskites and the interfacial contacts and ensuring the excellent operational stability of the resulting PeLEDs. Through rationally optimizing the amidation reaction in the perovskite emissive layers, we achieve efficient PeLEDs with a peak external quantum efficiency of 18.6% and a long half-life time of 682 h at 20 mA cm−2, presenting an important breakthrough in PeLEDs.

Ab initio studies on ammonium iodine under high pressure**Project supported by the National Natural Science Foundation of China (Grant Nos. 11574109, 51632002, 51572108, 91745203, and 11574112), the National Key Research and Development Program of China (Grant Nos. 2016YFB0201204 and 2018YFA0305900), the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT 15R23), and the National Fund

Ammonium iodine (NH4I) as an important member of hydrogen-rich compounds has attracted a great deal of attention owing to its interesting structural changes triggered by the relative orientations of adjacent ammonium ions. Previous studies of ammonium iodide have remained in the low pressure range experimentally, which we first extended to so high pressure (250 GPa). We have investigated the structures of ammonium iodine under high pressure through ab initio evolutionary algorithm and total energy calculations based on density functional theory. The static enthalpy calculations show that phase V is stable until 85 GPa where a new phase Ibam is identified. Calculations of phonon spectra show that the Ibam phase is stable between 85 GPa and 101 GPa and the Cm phase is stable up to 130 GPa. In addition, ammonium iodine dissociates into NH3, H2, and I2 at 74 GPa. Subsequently, we analyzed phonon spectra and electronic band structures, finding that phonon softening is not the reason of dissociation and NH4I is always a semiconductor within the pressure range.

Preparation and Properties of Nanocomposites in the Systems S-AgI and S-Ag2S-AgI in Dimethyl Sulfoxide

In this research work described synthesis of nanocomposites in the systems S–AgI and S–Ag2S–AgI in dimethyl sulfoxide (DMSO, (CH3)2SO) medium, and its some properties. Nanocomposites were obtained through the solvothermal synthesis at temperature range (T) 25÷160°C. The initial solutions were prepared by dissolution of sulfur (S), silver nitrate (AgNO3) and ammonium iodine (NH4I) in DMSO. The final products were obtained through the simple exchange reactions between initial solutions. Using the X-ray phase analysis (XRD), energy dispersive X-ray analysis (EDAX) and scanning electron microscopy (SEM) the samples were tested on phase and elemental composition, particle size and morphology, respectively. The results of XRD revealed that nanocomposites represented by S and AgI for system S–AgI, and by S, AgI and Ag2S for S–Ag2S–AgI system. The EDAX analysis showed the presence in composition of the investigated samples such elements like S, Ag and I for both systems. The SEM images demonstrated that both systems have a heterogeneus structure, the particles represented by flat and irregular shape. The size of the particles for S–AgI is fluctuated from 100 to 50000 nm and for S–Ag2S–AgI – from 90 to 4000 nm.

Anion-exchange red perovskite quantum dots with ammonium iodine salts for highly efficient light-emitting devices

Perovskite quantum dots have significant potential for light-emitting devices because of their high colour purity and colour tunability in the visible spectrum. Here, we report highly efficient red perovskite quantum dot-based light-emitting devices. The quantum dots were fabricated by anion exchange from pristine CsPbBr3 using halide-anion-containing alkyl ammonium and aryl ammonium salts. Anion-exchange quantum dots based on ammonium iodine salts exhibited a strong redshift from green emission to a deep-red emission at 649 nm as well as higher photoluminescence quantum yields. Furthermore, the quantum dot-based light-emitting device with the alkyl ammonium iodine salt exhibited an external quantum efficiency of 21.3% and high colour purity, with Commission Internationale de l’Eclairage coordinates of (0.72, 0.28), while the light-emitting device with the aryl ammonium iodine salt showed an external quantum efficiency of 14.1%. Finally, the operational stability of the latter was 36 times higher because the surface ligand density of the corresponding quantum dots was lower. Perovskite quantum dots (QDs) are synthesized via an anion-exchange process where CsPbBr3 is used to realize a highly efficient red light-emitting diode (LED). The perovskite QD-based LED exhibits the highest external quantum efficiency of more than 20% compared with perovskite LEDs.

Conversion of metal-organic halide perovskite from PbI2 precursor films grown by hot-wall method

We report on metal-organic halide perovskite CH3NH3PbI3 films converted from PbI2 precursors for planar heterojunction perovskite solar cells. PbI2 films as a precursor were deposited by hot-wall method and conventional vacuum evaporation. The conversion to perovskite phase from the PbI2 films were performed by annealing in methyl ammonium iodine (MAI) vapour at 120-150 °C. We confirmed that no residual PbI2 phase can be detected in the converted perovskite films by x-ray diffraction measurements. The surface morphology of the perovskite films was measured by AFM. Roughness Ra of the films is 17.8 nm, which is comparable value to the reported ones. Using the converted perovskite films we fabricated tentative perovskite solar cells with a device architecture of ITO/PEDOT:PSS/Perovskite/C60/Ag. The power conversion efficiencies of the fabricated solar cells from a conventional evaporation and the hot-wall method exhibited 2.22 and 2.33%, respectively.

Preparation and evaluation of dental resin with antibacterial and radio-opaque functions.

In order to prepare antibacterial and radio-opaque dental resin, a methacrylate monomer named 2-Dimethyl-2-dodecyl-1-methacryloxyethyl ammonium iodine (DDMAI) with both antibacterial and radio-opaque activities was added into a 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropyl)-phenyl]propane (Bis-GMA)/methyl methacrylate (MMA) dental resin system. Degree of conversion (DC), flexural strength (FS) and modulus (FM), water sorption (WS) and solubility (WSL), antibacterial activity, and radio-opacity (ROX) of the obtained dental resin system were investigated. Bis-GMA/MMA resin system without DDMAI was used as a control. The results showed that DDMAI could endow BIS-GMA/MMA resin system with good antibacterial (p < 0.05) and radio-opaque function without influencing the DC (p > 0.05). However, incorporating DDMAI into Bis-GMA/MMA resin could reduce mechanical properties (p < 0.05) and increase WS and WSL (p < 0.05), thus further work is needed in order to optimize the resin formulation.

Incorporation of an antibacterial and radiopaque monomer in to dental resin system

ObjectivesThe purpose of this study was to prepare antibacterial and radiopaque dental resin through adding one polymerizable quaternary ammonium compound with iodine as counter anion into Bis-GMA/TEGDMA (50/50, wt/wt) dental resin system, and evaluate the degree of monomer conversion, mechanical properties, radiopacity, and antibacterial effectiveness of the polymer. Methods2-Dimethyl-2-dodecyl-1-methacryloxyethyl ammonium iodine (DDMAI) (3wt.% and 5wt.%) was added into a Bis-GMA/TEGDMA (50/50, wt/wt) resin system with CQ (0.7wt.%) and DMAEMA (0.7wt.%) as photoinitiation system. Degree of monomer conversion (DC) was determined by FT-IR analysis. The flexural strength (FS) and flexural modulus (FM) of the polymer were measured using a three-point bending set up. Radiographs were taken to determine the radiopacity of the polymer, and aluminum step-wedge (0.5–4mm) was used as calibration standard. A single-species biofilm model with Streptococcus mutans as the tests organism was used to evaluate the antibacterial property of the polymer. Bis-GMA/TEGDMA without DDMAI was used as control material in all of the tests. ResultsANOVA analysis revealed that there was no significant difference in DC between polymer with and without DDMAI (p>0.05). Polymer with 3wt.% DDMAI had higher FS than the control material (p<0.05), while polymer with 5wt.% DDMAI had comparable FS with the control material (p>0.05). Though average FM of control material was lower than that of 3wt.% DDMAI containing polymer and higher than 5wt.% DDMAI containing polymer, but the differences were statistically insignificant. By increasing the quantity of DDMAI, the radiopacity of the polymer increased. Of the three formulations, the polymer with 5wt.% DDMAI inhibited biofilm the formation of the clinically relevant young biofilm. SignificanceIncorporation of DDMAI into resin system could endow it with radiopacity and antibacterial effectiveness, and these two properties seem to be improved with increasing the quantities of DDMAI.

Molecular orbital calculations for iodine complexes 2. Ammonium iodine and pyridine iodine

Calculations of H3N·I2 and PY·I2 using the INDO method with single and double-zeta Slater atomic orbital basis are reported. It is found that polarization and charge transfer play a fundamental role in stabilizing the complex. Interaction between donor and acceptor molecules involves the highest occupied as well as the inner molecular orbitals of the constituent molecules. A detailed description of the complex molecular orbitals is presented.