Alkylammonium Groups Research Articles

All‐Aromatic Polymer‐Based Anion Conductive Ionomers with Different Ion Exchange Capacities for Water Electrolysis

Anion exchange membrane water electrolysis (AEMWE) is vital for efficient, environmentally friendly, and cost‐effective hydrogen production. Herein, fluorene‐based polymers containing alkyl ammonium groups with different ion exchange capacities (IECs) for use in anion exchange membranes (AEMs) and anion exchange ionomers (AEIs) are investigated. Among the AEMs tested, the AEM with an IEC of 2.2 meq g−1 shows the highest anion conductivity because of its efficient water uptake characteristics. The anode catalyst layers utilize AEIs and iridium oxide catalyst particles. It is essential to select AEIs with appropriate IEC and suitable solvents for high‐performance anodes in water electrolyzers. Morphological and physical property evaluations reveal that moderate hydrophilicity and suppression of water swelling of AEIs improve water electrolysis performance. The optimized catalyst layer achieves better water electrolysis performance (2.64 V, 1.8 A cm−2 at 30 °C) than the conventional catalyst layer (3.83 V, 1.8 A cm−2 at 30 °C). Although the water electrolysis performance in this study falls short of the final targets, further research on anion conductive polymers and catalyst layers, based on this study's findings, is expected to promote practical applications of AEMWEs.

Theory of Turing pattern formation and its experimental realization in the CIMA reaction system in the presence of materials lowering the diffusivity of activators

In 1952, Alan Turing accomplished a pioneering theoretical study to show that the coupling of nonlinear chemical reactions and diffusion leads to the instability of spatially homogeneous states. The activator and inhibitor are synthesized as intermediates of the reaction system in the Turing model. Turing found that spatially periodic stationary concentration patterns are spontaneously generated when the diffusion coefficient of the activator is lower than that of the inhibitor. The first experimental realization of the Turing pattern was achieved in 1990 in a chlorite–iodide–malonic acid (CIMA) reaction system. Iodide and chlorite anions act as the activator and inhibitor of this reaction system, respectively. Although there is no significant difference in the diffusion coefficient of iodide and chlorite anions, the Turing pattern was generated because starch was added to the gel reactor to enhance the color tone. This formed a complex with iodide to inhibit its diffusion to satisfy the condition for the Turing instability. Several examples were found after this finding. We focused on the high affinity of quaternary alkyl ammonium cations to iodide. The CIMA reaction was performed in an open gel reactor by adding a quaternary alkyl ammonium cationic surfactant. In addition, the polymer gel consists of the quaternary alkyl ammonium group as the side chain was utilized for the open gel reactor. The micelles of the surfactants and the polymer gels trapped iodide in their vicinity as a counter anion to lower the effective diffusivity to satisfy the condition for the Turing instability.

Monolayer Modification of Spherical Amorphous Silica by Clay Nanosheets.

Clay-silica nanocomposite materials (CSiN) were prepared by an electrostatic interaction between negatively charged clay nanosheets and positively charged spherical silica, which was modified with an alkyl ammonium group by silane coupling. By optimization of the preparation conditions, 84% coverage of the silica surface by the clay nanosheets was achieved. Adsorption experiments using cationic porphyrin dyes on the CSiN revealed that the clay nanosheet covers the spherical silica as a single layer and does not detach from the silica surface under aqueous conditions. In addition, it turned out that the cationic porphyrin dye did not penetrate the space between the silica surface and the clay nanosheet. Porphyrin molecules were adsorbed only at the outer surface of the clay nanosheet without molecular aggregation even under the high-density adsorption conditions. By combining spherical silica and clay nanosheets, it is possible to prepare novel hybrid materials where the surface can act as a unique adsorption field for dyes.

Poly(carbazole)-Based Anion Exchange Membranes Developed by Grafting Alkyl Ammonium Group

AEM water electrolysis offers several advantages over proton exchange membrane water electrolysis such as the potential use of non-precious metal catalysts and less expensive bipolar plates. Therefore, there is a great demand for reliable, high-performing, durable, and low-cost AEMs for the technologies.1 In this presentation, we report polycarbazole-based AEMs by acid-catalyzed Friedel Craft’s polycondensation reaction followed by grafting with an alkyl ammonium group.2 Two AEMs, PDPC-3QA (IEC=1.25 meq./g) and PDPC-6QA (IEC=1.74 meq./g), were synthesized by grafting 3-bromo-N,N,N-trimethylpropan-1-aminium bromide (3-BrQA) and 6-bromo-N,N,N-trimethylhexan-1-aminium bromide (6-BrQA), respectively on the precursor polymer. While 100% grafting was achieved with 6-BrQA, only 60% of grafting was achieved with 3-BrQA due to the competition between the elimination and substitution reaction on 3-BrQA because of the higher acidity of β-hydrogen resulted from the proximity of the bromide and ammonium groups. With high OH- conductivity (103 mS/cm at 80 °C) and excellent alkaline stability (< 3% conductivity loss after 500 hours in 1 M NaOH at 80 °C), PDPC-6QA exhibits promising water electrolyzer performance.

Ion-Specific Antipolyelectrolyte Effect on the Swelling Behavior of Polyzwitterionic Layers

In this study, we systematically investigate the interactions between mobile ions generated from added salts and immobile charges within a sulfobetaine-based polyzwitterionic film in the presence of five salts (KCl, KBr, KSCN, LiCl, and CsCl). The sulfobetaine groups contain quaternary alkylammonium and sulfonate groups, giving the positive and negative charges. The swelling of the zwitterionic film in the presence of different salts is compared with the swelling behavior of a polycationic or polyanionic film containing the same charged groups. For such a comparative study, we design cross-linked terpolymer films with similar thicknesses, cross-link densities, and charge fractions, but with varying charged moieties. While the addition of salt in general leads to a collapse of both cationic and anionic films, the presence of specific types of mobile anions (Cl-, Br-, and SCN-) considerably influences the swelling behavior of polycationic films. We attribute this observation to a different degree of ion-pair formations between the different types of anionic counterions and the immobile cationic quaternary alkylammonium groups in the films where highly polarizable counterions such as SCN- lead to a high degree of ion pairing and less polarizable counterions, such as Cl-, cause a low degree of ion pairing. Conversely, we do not observe any substantial effect of varying the type of cationic counterions (K+, Li+, and Cs+), which we assign to the lack of ion pairing between the weakly polarizable cations and the immobile anionic sulfonate groups in the films. In addition, we observe that the zwitterionic films swell with increasing ionic strength and the degree of swelling is anion dependent, which is in agreement with previous reports on the "antipolyelectrolyte effect". Herein, we explain this ion-specific swelling behavior with the different cation and anion abilities to form ion pairs with quaternary alkylammonium and sulfonate in the sulfobetaine groups.

(Digital Presentation) Fabrication of Monolayer-Protected Gold Cluster Thin Films: Electrochemical and Optical Properties

Quantum-sized monolayer-protected gold clusters have captivated the imagination of scientists over the last two decades and show exciting optical, electrochemical and catalytic properties when compared to larger-sized plasmonic gold nanoparticles, making them useful for myriad new applications in photonics, catalysis and sensors. One interesting property is the photoluminescence (PL) of gold clusters making them suitable as biological imaging labels. However, the low PL Quantum Yields (QY) are a concern for these clusters and research is focused on improving the PL QYs. One strategy, our research group has worked on is the shell-gold rigidification via the use of surfactants and proteins. Shell ligand rigidification was achieved by ion pairing with bulky tertiary alkyl ammonium groups and aromatic chromophores. Another strategy to reduce the non-radiative deactivation pathways is by making the gold cluster thin films. In a recent study, it was shown that solid state films of clusters not only have manifold increase in PL quantum yield but also their luminescent lifetimes and two photon absorption cross-sections are greatly enhanced in comparison to their solution analogues. Researchers have worked on various strategies to make gold cluster thin films for device applications. One problem with thin films of gold clusters is that the clusters lose their interesting optical and electrochemical properties that were observed in solution phase. For making the clusters useful by enhancing PL for photonic device applications, it is important for the clusters to retain their properties in solid state, which is the main objective of the study carried out here. One problem is that drying intrinsic gold clusters results in crystallization whose optical properties are difficult to characterize. In this study, we have used Nafion and polyvinylpyrrolidone (PVP) to make thin films of water-soluble glutathione-protected gold clusters. Water soluble cluster Au22(SG)18 with reported PLQY of 8% were synthesized and characterized by UV-VIS absorption and PL measurements and thin films of these clusters were made using water soluble PVP and Nafion polymers via drop casting. Enhanced PL and electrochemical properties were observed for clusters in solid state. Similarly, non-polar gold cluster films are fabricated with Polystyrene and optical absorption and PL properties were retained in the solid state.Although drop casting with polymers was found to retain the optical properties, the uniformity of films is a problem. The uniformity of the film is dependent on solvent’s surface tension thus diminishing the quality of the film. Therefore, there is a need of depositing films of gold clusters in a controlled manner which governs their thickness and uniformity. Electropolymerization technique is known to make films during the polymerization of monomers possessing functional groups whose oxidation or reduction via anti-bonding or non-boding electrons on a heteroatom. In this study, we have used electropolymerization strategy to fabricate thin films of gold clusters on conducting substrates. The film is deposited at the working electrode during cyclic voltammetric (CV) sweep when passed through the required reduction or oxidation potential of the monomer under suitable conditions. This technique makes a uniform film throughout the exposed area of the working electrode active surface and the thickness of the film is often proportional to the number of sweep cycles employed. Therefore, introduction of gold clusters in this process with monomers which are previously known to bond with each other will incorporate clusters in the film during the polymerization process and will ease their film formation with uniform thickness. Amongst various size gold clusters, the one which shows good stability as a result of following the magic number series is Au25(SR)18 - . The stability of clustersis one of the important parameter required for practical applications. Aniline and other amine based monomers are used as precursors to make thin films of Au25 on conducting substrate such as Indium tin oxide. By solubilizing the gold clusters with the monomers they are deposited along with the polymers.

Pumping between phases with a pulsed-fuel molecular ratchet.

The sorption of species from a solution into and onto solids underpins the sequestering of waste and pollutants, precious metal recovery, heterogeneous catalysis, analysis and separation science, and other technologies1,2. The transfer between phases tends to proceed spontaneously in the direction of equilibrium. For example, alkyl ammonium groups mounted on silica nanoparticles are used to chemisorb cucurbituril macrocycles from solution through host-guest binding3,4. Molecular ratchet mechanisms5-7, in which kinetic gating8-12 inhibits or accelerates particular steps, makes it possible to progressively drive dynamic systems13-16 away from equilibrium17-21. Here we report on molecular pumps22 immobilized on polymer beads23-25 that use an energy ratchet mechanism5,9,19-21,26-30 to directionally transport substrates from solution onto the beads. On the addition of trichloroacetic acid (CCl3CO2H)19,31-33 fuel19,34-37, micrometre-diameter polystyrene beads functionalized38 with solvent-accessible molecular pumps sequester from the solution crown ethers appended with fluorescent tags. After fuel consumption, the rings are mechanically trapped in a higher-energy, out-of-equilibrium state on the beads and cannot be removed by dilution or exhaustive washing. This differs from dissipative assembled materials11,13-16, which require a continuous supply of energy to persist, and from conventional host-guest complexes. The addition of a second fuel pulse causes the uptake of more macrocycles, which drives the system further away from equilibrium. The second macrocycle can be labelled with a different fluorescent tag, which confers sequence information39 on the absorbed structure. The polymer-bound substrates can be released back to the bulk either one compartment at a time or all at once. Non-equilibrium40 sorption by immobilized artificial molecular machines41-45 enables the transduction of energy from chemical fuels for the use, storage and release of energy and information.

A hydrophobic cationic polyphenol coating for versatile antibacterial and hemostatic devices

Flexible coating materials have attracted much attention for the surface functionalization of biomedical devices. In this work, one cationic coating material (AQTA) is constructed with the co-substitution of tannic acid with alkyl and quaternary ammonium groups, and then employed to functionalize versatile medical devices for antibacterial and hemostatic applications. Stable AQTA coatings with tunable contents are realized by facile one-step soaking process, owing to the well-designed molecular structure of AQTA (elaborate combination of long-chain alkyl, phenolic hydroxyl and quaternary ammonium groups). The high content of AQTA is coated on polyurethane (as the model substrate of medical catheters), which achieves high blood compatibility and in vitro/in vivo antibacterial ability. The feasibility of AQTA for hemostatic uses is confirmed by the improved properties of functionalized alginate dressing and gauze with one moderate content of AQTA. Together with the negative role of AQTA on the hemostatic performance of chitosan dressing, the underlying hemostatic mechanism of AQTA for negatively charged dressings was revealed as the optimized surface-activated platelet adhesion. Two typical rat-hemorrhage models further confirm the high hemostatic performance of AQTA-coated dressing. This work sheds light on the design and flexible management of cationic coating materials for biomedical applications.

The Role of Alkyl Chain Length and Halide Counter Ion in Layered Dion-Jacobson Perovskites with Aromatic Spacers.

Layered hybrid perovskites based on Dion-Jacobson phases are of interest to various optoelectronic applications. However, the understanding of their structure-property relationships remains limited. Here, we present a systematic study of Dion-Jacobson perovskites based on (S)PbX4 (n = 1) compositions incorporating phenylene-derived aromatic spacers (S) with different anchoring alkylammonium groups and halides (X = I, Br). We focus our study on 1,4-phenylenediammonium (PDA), 1,4-phenylenedimethylammonium (PDMA), and 1,4-phenylenediethylammonium (PDEA) spacers. Systems based on PDA did not form a well-defined layered structure, showing the formation of a 1D structure instead, whereas the extension of the alkyl chains to PDMA and PDEA rendered them compatible with the formation of a layered structure, as shown by X-ray diffraction and solid-state NMR spectroscopy. In addition, the control of the spacer length affects optical properties and environmental stability, which is enhanced for longer alkyl chains and bromide compositions. This provides insights into their design for optoelectronic applications.

An Imidazolium-Based Lipid Analogue as a Gene Transfer Agent.

A dicationic imidazolium salt is described and investigated towards its application for gene transfer. The polar head group and the long alkyl chains in the backbone contribute to a lipid-like behavior, while an alkyl ammonium group provides the ability for crucial electrostatic interaction for the transfection process. Detailed biophysical studies regarding its impact on biological membrane models and the propensity of vesicle fusion are presented. Fluorescence spectroscopy, atomic force microscopy and confocal fluorescence microscopy show that the imidazolium salt leads to negligible changes in lipid packing, while displaying distinct vesicle fusion properties. Cell culture experiments reveal that mixed liposomes containing the novel imidazolium salt can serve as plasmid DNA delivery vehicles. In contrast, a structurally similar imidazolium salt without a second positive charge showed no ability to support DNA transfection into cultured cells. Thus, we introduce a novel and variable structural motif for cationic lipids, expanding the field of lipofection agents.

Fabrication of meso- and microporous MFI zeolites by amphiphilic molecules with biphenol group

Abstract We reported a strategy to synthesize MFI zeolites with tunable properties by tailoring organic structure-directing agents (OSDAs) under the hydrothermal conditions. The tailored surfactants were obtained by tuning the structure of Gemini-type Cph-10-6-6 and Bola-type BCph-10-6-6, including alkyl tail chains, ammonium groups and alkyl middle chains. The textural property, morphology and acidity of resulting MFI zeolites were characterized by a complementary combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption isotherms and FTIR spectra of pyridine adsorption. Moreover, the correlation between the OSDAs’ composition and the inorganic precursor in the fabrication of zeolite framework was investigated by DFT calculations in this study. The catalytic performance of the resulting MFI samples was investigated by the alkylation of mesitylene with benzyl alcohol. The results revealed that the OSDAs without ammonium groups only leaded to form the micro-structure of zeolites, but the OSDAs with ammonium groups can induce the formation of micro- and meso-structure simultaneously, regardless the OSDAs ended with or without alkyl tail chains. In addition, the resulting MFI zeolites showed an improved catalytic activity in alkylation of mesitylene with benzyl alcohol due to the enhanced pore accessibility, the acidity (Bronsted/Lewis) controlled the activation of benzyl alcohol, and the ratio of external surface area (Sext/SBET) governed the selectivity of alkylation reaction. As a result, tailoring the structure of OSDAs can pick another strategy to synthesize MFI zeolites with tunable zeolite structure and catalytic performance.

In search of an optimal acid-base indicator for examining surfactant micelles: Spectrophotometric studies and molecular dynamics simulations

We report on combined experimental and theoretical investigations of the water/micelle interface of cationic, anionic, zwitterionic, and non-ionic surfactants using a new hydrophobic acid-base indicator 2,6-dinitro-4-n-dodecylphenol. The indices of the so-called apparent ionization constant, pKaapp, of the indicator fixed in the micellar pseudophase are determined by the spectrophotometric method. The data allows estimating the Stern layer’s electrostatic potential of the ionic micelles Ψ. Molecular Dynamics modeling was used to locate the dye molecule and, in particular, its ionizing group OH→O– within the micelles of the studied surfactants. The comparison of the Ψ values estimated using 2,6-dinitro-4-n-dodecylphenol with both our computer simulation and literature experimental results reveals obstacles in monitoring electrical interfacial potentials. In particular, the Ψ values of the surfactant micelles with alkylammonium groups determined via 2,6-dinitro-4-n-dodecylphenol are overestimated. The reason is specific interactions of the indicator anion with the surfactant head groups. For anionic surfactants, however, this indicator is quite suitable, which is confirmed by the location of HA and A– equilibrium forms in the pseudophase.

Physically-crosslinked anion exchange membranes by blending ionic additive into alkyl-substituted quaternized PPO

An additive-induced physically crosslinked system for use as anion exchange membranes was developed by blending an additive (DHBQA) containing both long alkyl (C12, dodecyl) and quaternary ammonium groups into a dodecyl-substituted and quaternary ammonium-functionalized PPO (poly(2,6-dimethyl-1,4-phenylene oxide)) (C12-PPO-QA). The additive, whose diammonium groups act as ion conductors, and whose long alkyl chains bind to the alkyl chains of the C12-PPO-QA polymer through van der Waals interactions, induced the formation of ion clusters as well as physical crosslinking of the C12-PPO-QA polymer. Controlling the amount of additive to maximize its intermolecular interactions with the polymer resulted in a PPO-10.8 membrane (10.8 wt% of additive relative to polymer) with very high ion conductivities of 49.2 mS cm−1 at 20 °C and 107.6 mS cm−1 at 80 °C and low swelling ratios of 18.2% at 20 °C and 33.3% at 80 °C, as well as excellent mechanical and alkaline stability. The H2/O2 single cell performance using PPO-10.8 reached a maximum power density about 60 mW cm−2, higher than that of the PPO-0 sample.

Anion exchange membranes with clusters of alkyl ammonium group for mitigating water swelling but not ionic conductivity

Crosslinked ionomers containing clusters of alkyl ammonium group at side chain was synthesized by attaching an unique amine (tris[2-(dimethylamino)ethyl]amine) on poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) polymer backbone. These molecular structures show a dramatic enhancement in water resistance (low water uptake (9–13%) and dimensional swelling (4–6%) in water at room temperature) compared with non-cluster-shaped PPOs. Moreover, the temperature had less of an influence on the water uptake and swelling ratio of the membranes. The resulting anion exchange membranes exhibit good ionic (OH-) conductivities in water (up to 25.4mScm−1 at 25°C) and represent a new class of anion exchange membranes. A test of the alkaline stability of membranes (in 1M KOH at 60°C for 480h) showed hydroxide conductivity about 51% of the original conductivity and indicated that these membranes are good candidates for application in alkaline fuel cells (AFCs). Membrane electrode assembly made from the as-fabricated membrane showed moderate fuel cell performance reaching peak power density 77mWcm−2 at 60°C in a H2/O2 alkaline fuel cell. This simplistic synthetic tactic enables the preparation of densely functionalized materials with the potential to meet the demands of AFCs.

Dissipative Particle Dynamics Simulations of Anion Exchange Membranes

Anion exchange membranes (AEM) are currently under investigation for their application in energy and conversion devices.1,2 The main challenges of the AEMs are the low stability and ionic conductivity. Rather than increasing the ion exchange capacity, a realistic strategy to enhance the conductivity is to use phase segregated AEMs.3 Hence, the morphology of the AEM polymer is very important to achieve high performance. However, there is still a lack of fundamental understanding of stability and transport in AEMs.4 Recently, researchers have reported elastomeric AEMs exhibiting satisfactory chemical stability.5 These AEMs are based on the triblock copolymer, polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS), and functionalized with various cationic groups. In this research, dissipative particle dynamics (DPD) simulations were chosen to model the morphology of SEBS systems functionalized with tetra alkyl ammonium groups. DPD, a meso-scale simulation technique, enables relatively large time and length scales to be examined,6,7 and therefore permits the morphology of the polymer system in acceptable time and computational expenses. The SEBS polymer was coarse-grained in to DPD beads, balancing both chemical distinction and fine structural variants. The optimized structure and the interaction parameters of these beads were calculated by using a recently developed methodology employing DFT based electronic structure calculations.8 ,9 The morphology of the aforementioned AEMs were simulated at different hydration levels. The result shows that the morphology changes with the hydration levels. The effects of the alkyl chain tethered to the cation group, the ion exchange capacity, and the copolymer composition were also investigated.

Novel solid-state luminous composites from a layered inorganic–organic monolith containing neutral porphyrins

We have succeeded in loading a neutral zinc porphyrin derivative (ZnTPPder) into a layered inorganic–organic compound, despite the well-known difficulties associated with incorporation of neutral pigments into the interlayer spaces of layered materials. We have utilized a synthetic alkylammonium–smectite monolith (A-Sm) as the host layered inorganic–organic compounds to facilitate porphyrin loading. Alkylammonium groups are located between the layers of the phyllosilicate-analogue moieties (the inorganic moiety) bonding covalently with the inorganic moiety to form the monolith. The interlayer space of A-Sm is organophilic and swells in organic solvents. ZnTPPder was loaded into A-Sm by mixing A-Sm and solutions of ZnTPPder in organic solvents under different conditions yielding ZnTPPder/A-Sm composite films. UV–VIS measurements revealed several absorption peaks assigned to the characteristic Soret (432 nm) and Q (500–650 nm) bands of ZnTPPder for all the prepared ZnTPPder/A-Sm composite films. Fluorescence emission due to ZnTPPder was observed from all the ZnTPPder/A-Sm composite films, while a reference ZnTPPder/Sm cast film prepared from ZnTPPder and a smectite (Sm) rather than A-Sm was only weakly fluorescent. This emission behaviour suggests that ZnTPPder is intercalated in the interlayer space of A-Sm with suppression of aggregation of ZnTPPder. In contrast, ZnTPPder was hardly intercalated into the interlayer space of Sm. Thus, we have demonstrated a novel and relatively easy route for loading of neutral (uncharged) pigments into a solid-state two-dimensional nanospace, a method which might be applied to prepare novel light-harvesting systems.

Electrosynthesis Using a Recyclable Mediator-Electrolyte System Based on Ionically Tagged Phenyl Iodide and 1,1,1,3,3,3-Hexafluoroisopropanol.

A new type of redox mediator for electrosynthesis based on the iodine(I)/iodine(III) redox couple is reported. It is demonstrated that the use of 1,1,1,3,3,3-hexafluoroisopropanol as solvent plays a crucial role for both the selective anodic generation of the active iodine(III) species and the subsequent chemical transformation. Furthermore, the supporting electrolyte is merged with the mediator by tethering the redox-active iodophenyl moiety to an alkylammonium group, allowing for straightforward recovery and reuse of both components.

AMINE MODIFIED MESOSTRUCTURED SILICA NANO PARTICLES ENHANCED ADSORPTION OF PHENOL

Mesoporous silica nanoparticles (MSN) were synthesized and modified with (3-aminopropyl) triethoxysilane (APTES) using co-condensation (co-MSN) and post-grafting (post-MSN) methods. Both modification methods seem to alter the crystallinity, surface area, and pore volume as compared to the unmodified MSN. The activity of all MSNs was tested for the adsorptive removal of phenol. Co-MSN showed significantly good adsorptivity towards 10 mg L-1 of phenols, followed by post-MSN and MSN. It was found that the highest activity of co-MSN was resulted from the additional higher adsorption energy from the quaternary alkylammonium groups (Si–C–C–C–[N+–(CH3)3]) of cationic template and also from the amine group of the APTES functionalization, which showed more advantages as compared to post-MSN and MSN.

Light-Emitting Electrochemical Cells Based on Hybrid Lead Halide Perovskite Nanoparticles

Methylammonium lead bromide (MAPbBr3) perovskite nanoparticles (NPs) have been recently proposed as a new material for light-emitting diodes, as well as a new paradigm to elucidate the operational mechanism in perovskite solar cells. Here, we have expanded the synthesis concept to fabricate NPs based on formamidinium lead bromide (FAPbBr3). Importantly, we have demonstrated that the photophysical features of this novel material can be easily tuned by exchanging the organic cation, achieving lower radiative bimolecular recombination rate for FAPbBr3 NPs. Additionally, we report for the first time light-emitting electrochemical cells (LECs) based on perovskite NPs by an easily up-scalable spray-coating technique. Stable luminance of 1–2 cd/m2 at low driving currents was achieved for both types of materials. Overall, this work opens a new avenue of research into the field of organic–inorganic metal halide nanoparticles bearing different alkyl ammonium groups and their application in the developing field of t...

Immobilization of phosphomolybdic acid on the surface of mesoporous silica functionalized with alkylammonium groups

Silica containing protonated 3-aminopropyl groups has been synthesized by a template method using Pluronic 123 as a surfactant in an acidic medium at a hydrochloric acid concentration of 1.72 M. The X-ray diffraction data have indicated that the obtained sample has a highly ordered hexagonal structure, which agrees with the large specific surface area and sorption pore volume (Ssp = 880 m2/g, Vs = 1.28 cm3/g) typical of SBA-15 materials. However, transmission electron microscopy data show that this material contains two phases, with one of them being similar to SBA-15 mesoporous silica and the other belonging to socalled “honeycomb foams.” An ion-exchange reaction has been employed to immobilize phosphomolybdic acid H3[P(Mo3O10)4] on the pore surface, and the fact of immobilization has been confirmed by IR and TGA data. This functionalization significantly reduces the Ssp and Vs values of the sample but has no effect on isotherm pattern, thereby attesting to retaining the silica structure after the modification.