Deprotonation Process Research Articles

Study on pH dependent ON/OFF fluorescent switching behaviour of hydrothermally synthesised vanadium disulphide quantum dots (VS2-QDs)

It is fascinating to design and develop an inorganic quantum dot (QDs) which exhibit luminescence features with ion concentration, temperature, and pH sensitivity dependence. Vanadium disulphide (VS2) belongs to the family of transition metal dichalcogenides (TMDs), and is extensively studied owing to its layered characteristics features in sensing and filtrations technology, however, its fluorescence features have not been well studied so far. The current work describes a widely adopted eco-friendly hydrothermal approach for the synthesis of VS2-QDs. The average size of particles was determined to be ∼10 nm by transmission electron microscopy (TEM) and Zetasizer analysis. The synthetic approach adopted here facilitates in situ functionalization of QDs, which results in their high stability in aqueous medium and enhanced sensitivity towards their surroundings. As most of the QDs show the sensitivity towards pH, a thorough investigation of VS2 QDs for their pH dependent photoluminescence has been carried out. The VS2-QDs were discovered to exhibit a remarkable luminescence intensity that was found to be about 11 times higher in basic conditions (pH ∼ 13, QY = ∼4.80 %) as compared to that in acidic conditions (pH ∼ 1, QY = ∼1.10 %). The root cause of this ON/OFF florescence flipping may be related to the functional groups (such as −SO42−, −NH2, OH−, etc.) attached over the surface of QDs, acid etching, and protonation–deprotonation process. This paper highlights the pH dependent switching behaviour of VS2-QDs that could offer valuable information for designing a futuristic pH-based device for biomedical applications.

Efficient Tin-Lead Perovskite Solar Cells with a Ultrawide Usage Windows of Precursor Solution Opened by SnF2.

High quality tin-lead perovskite solar cells (Sn─Pb PSCs) can be fabricated via simple solution processing methods. However, the instability of precursor solutions and their narrow usage windows still pose challenges in manufacturing efficient and reproducible Sn─Pb PSCs, hindering the commercialization of PSCs. Fluorine tin (SnF2) is widely used as an antioxidant to improve the crystallinity of perovskite. In this study, another role of SnF2 as a stabilizer is found to restrain the deprotonation of methylammonium iodide (MAI)in the precursor solution, which improves their stability and expands their usage windows. Due to the inhibition of SnF2 on oxidation and deprotonation, stable large-sized colloidal clusters form gradually in perovskite precursor solution during aging, leading to uniform nucleation/crystallization during film growth, significantly reducing the roughness and defect density in the films. Because of the competitive deprotonation and oxidation process of Sn2+, the benefit of larger cluster maximizes after about ten days storage of precursor solution. The champion efficiency of Sn─Pb PSCs prepared with 10days aged precursor solution is 22.00%. High performance of devices fabricated with precursor solution stored for even ≈40days discloses the wide usage windows of precursor solution with SnF2 additive.

Pd-Catalyzed Oxidative C-H Arylation of (Poly)fluoroarenes with Aryl Pinacol Boronates and Experimental and Theoretical Studies of its Reaction Mechanism.

We report the synergistic combination of Pd(OAc)2 and Ag2O for the oxidative C-H arylation of (poly)fluoroarenes with aryl pinacol boronates (Ar-Bpin) in DMF as the solvent. This procedure can be conducted easily in air, and without using additional ligands, to afford the fluorinated unsymmetrical biaryl products in up to 98 % yield. Experimental studies suggest that the formation of [PdL2(C6F5)2] in DMF as coordinating solvent does not take place under the reaction conditions as it is stable to reductive elimination and thus would deactivate the catalyst. Thus, the intermediate [Pd(DMF)2(ArF)(Ar)] must be formed selectively to give desired arylation products. DFT calculations predict a low barrier (5.87 kcal/mol) for the concerted metalation deprotonation (CMD) process between C6F5H and the Pd(II) species formed after transmetalation between the Pd(II)X2 complex and aryl-Bpin which forms a Pd-Arrich species. Thus a Pd(Arrich)(Arpoor) complex is generated selectively which undergoes reductive elimination to generate the unsymmetrical biaryl product.

Enhanced reduction of graphene oxide via laser-dispersion coupling: Towards large-scale, low-defect graphene for crease-free heat-dissipating membranes in advanced flexible electronics

The advancement of flexible electronics demands improved components, necessitating heat dissipation membranes (HDMs) to exhibit high thermal conductivity while maintaining structural integrity and performance stability even after extensive deformation. Herein, we have devised a laser-modulated reduction technique for graphene oxide (GO), enabling the fabrication of high-quality, large-scale, low-defect graphene, which yields high-performance HDMs after orderly deposition. The work underscores the crucial role of the laser wavelength and dispersion liquid’s coupling intensity in influencing the morphology and properties of graphene. Optimal coupling effect and energy conversion are realized when a laser of 1064 nm wavelength irradiates a triethylene glycol (TEG)/N,N-Dimethylformamide (DMF) dispersion. This unique synergy generates high transient energy, which facilitates the deprotonation process and ensures a swift, comprehensive GO reduction. In contrast to conventional water-based laser reduction methods, the accelerated reaction magnifies the size of the graphene sheets by mitigating the ablation effect. After membrane construction with an ordered structure, the corresponding membrane exhibits a high thermal conductivity of 1632 W m−1 K−1, requiring only ∼1/10 of the total preparation time required by other reported methods. Remarkably, the resulting HDM demonstrates superior resilience against creasing and folding, maintaining excellent smoothness and negligible reduction in thermal conductivity after violent rubbing. The combination of exceptional flexibility and thermal conductivity in HDMs paves the way for long-term practical use in the flexible electronics industry.

Spatially and Temporally Resolved Dynamic Response of Co-Based Composite Interface during the Oxygen Evolution Reaction.

Interfacial interaction dictates the overall catalytic performance and catalytic behavior rules of the composite catalyst. However, understanding of interfacial active sites at the microscopic scale is still limited. Importantly, identifying the dynamic action mechanism of the "real" active site at the interface necessitates nanoscale, high spatial-time-resolved complementary-operando techniques. In this work, a Co3O4 homojunction with a well-defined interface effect is developed as a model system to explore the spatial-correlation dynamic response of the interface toward oxygen evolution reaction. Quasi in situ scanning transmission electron microscopy-electron energy-loss spectroscopy with high spatial resolution visually confirms the size characteristics of the interface effect in the spatial dimension, showing that the activation of active sites originates from strong interfacial electron interactions at a scale of 3 nm. Multiple time-resolved operando spectroscopy techniques explicitly capture dynamic changes in the adsorption behavior for key reaction intermediates. Combined with density functional theory calculations, we reveal that the dynamic adjustment of multiple adsorption configurations of intermediates by highly activated active sites at the interface facilitates the O-O coupling and *OOH deprotonation processes. The dual dynamic regulation mechanism accelerates the kinetics of oxygen evolution and serves as a pivotal factor in promoting the oxygen evolution activity of the composite structure. The resulting composite catalyst (Co-B@Co3O4/Co3O4 NSs) exhibits an approximately 70-fold turnover frequency and 20-fold mass activity than the monomer structure (Co3O4 NSs) and leads to significant activity (η10 ∼257 mV). The visual complementary analysis of multimodal operando/in situ techniques provides us with a powerful platform to advance our fundamental understanding of interfacial structure-activity relationships in composite structured catalysts.

How is Membrane Permeation of Small Ionizable Molecules Affected by Protonation Kinetics?

According to the pH-partition hypothesis, the aqueous solution adjacent to a membrane is a mixture of the ionization states of the permeating molecule at fixed Henderson-Hasselbalch concentrations, such that each state passes through the membrane in parallel with its own specific permeability. An alternative view, based on the assumption that the rate of switching ionization states is instantaneous, represents the permeation of ionizable molecules via an effective Boltzmann-weighted average potential (BWAP). Such an assumption is used in constant-pH molecular dynamics simulations. The inhomogeneous solubility-diffusion framework can be used to compute the pH-dependent membrane permeability for each of these two limiting treatments. With biased WTM-eABF molecular dynamics simulations, we computed the potential of mean force and diffusivity of each ionization state of two weakly basic small molecules: nicotine, an addictive drug, and varenicline, a therapeutic for treating nicotine addiction. At pH = 7, the BWAP effective permeability is greater than that determined by pH-partitioning by a factor of 2.5 for nicotine and 5 for varenicline. To assess the importance of ionization kinetics, we present a Smoluchowski master equation that includes explicitly the protonation and deprotonation processes coupled with the diffusive motion across the membrane. At pH = 7, the increase in permeability due to the explicit ionization kinetics is negligible for both nicotine and varenicline. This finding is reaffirmed by combined Brownian dynamics and Markov state model simulations for estimating the permeability of nicotine while allowing changes in its ionization state. We conclude that for these molecules the pH-partition hypothesis correctly captures the physics of the permeation process. The small free energy barriers for the permeation of nicotine and varenicline in their deprotonated neutral forms play a crucial role in establishing the validity of the pH-partitioning mechanism. Essentially, BWAP fails because ionization kinetics are too slow on the time scale of membrane crossing to affect the permeation of small ionizable molecules such as nicotine and varenicline. For the singly protonated state of nicotine, the computational results agree well with experimental measurements (P1 = 1.29 × 10-7 cm/s), but the agreement for neutral (P0 = 6.12 cm/s) and doubly protonated nicotine (P2 = 3.70 × 10-13 cm/s) is slightly worse, likely due to factors associated with the aqueous boundary layer (neutral form) or leaks through paracellular pathways (doubly protonated form).

Composite waste-based aramid aerogel separators

Lithium ion batteries are one of the most promising electrochemical energy storage systems. They generally consist of four components: anode, cathode, electrolyte, and separator. The separators are crucial for batteries since they prevent physical contact of electrodes and thus short circuit. In this study, reutilization of aramid fabric was highlighted by transforming it into a high value product: battery separator. A waste aramid fabric was used to synthesize aramid aerogels by deprotonation, sol-gel, and freeze-drying processes and then investigated as lithium ion battery separators. Aramid fabric was collected from a scrap plant of an industrial automotive company. Nanoclay or TiO2 nanoparticles were added into this waste-based aramid aerogel matrix in the sol-gel stage to further enhance the performance of the separators. The samples were characterized by scanning electron microscope (SEM), linear sweep voltammetry, electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge tests. A uniform and bead-free morphology was observed for all samples with over 60% porosity. Electrolyte uptake and ionic conductivity test results showed that addition of TiO2 nanoparticles increased electrolyte uptake and ionic conductivity up to 365% and 2.2 mS/cm, respectively. The cells prepared by using nanocomposite aramid aerogels with TiO2 exhibited excellent cycling performance with a capacity of around 160 mAh/g in 200 cycles.

Copper dopants facilitated generation of high-valent cobalt sites for improved oxygen evolution

We report a strategy for adjusting surface reconstruction of Co4N, in which inert Co3O4 on the reconstruction surface is activated via Cu introduction (Cu-Co4N), facilitating the deprotonation process to generate CoO2.

SYNTHESIS, CHARACTERIZATION OF NEW ASYMMETRICALLY IMIDAZOLIUM SALTS WITH THEIR Ag(I) AND Pd(II)-N-HETEROCYCLIC CARBENE COMPLEXES

New substituted asymmetrically imidazolium salts with Ag(I) and Pd(II) N-heterocyclic carbene complexes were synthesized and characterized. In order to produce asymmetrically substituted salts, imidazolium salts have been produced using a variety of substituents, including aliphatic chain and phenyl acetamide chloride (5,6,7). Using the carbene site deprotonation process, silver(I)-NHC complexes (8,9,10) were produced from the reaction of asymmetrically substituted imidazolium salts with Ag2O. The appropriate Pd(II)-NHC (11,12,13) were then synthesized using the transmetallation process using Ag(I)-complexes. NHC as transfer reagents. The complexes were identified using spectroscopy methods such as 1H-, 13C-NMR and FT-IR spectroscopy. The recorded spectra of the prepared complexes and their salts agree with theoretical ones.

Designing of Hexagonal Nanosheets with Edge‐Sharing [IrO6] Octahedral Crystals for Efficient and Stable Acidic Water Splitting

AbstractThe oxygen evolution reaction (OER) is a critical factor for advancing the industrial application of proton exchange membrane (PEM) electrolyzers. However, the low mass activity of iridium‐based catalysts has become a critical obstacle in improving the efficiency of the OER. To address this problem, a hexagonal system nanosheet structure with lattice distortion and edge‐connected [IrO6] octahedron is designed to enhance both mass activity and durability. This material exhibits a high mass activity of 217 mA mgIr−1 at 1.55 V relative to the reversible hydrogen electrode (RHE), which is 13 times greater than that of Rutile IrO2. Furthermore, the voltage of T‐CsIr exhibits no significant increase after 400 h of continuous operation at a current density of 10 mA cm−2. Integrating X‐ray experimental analysis with theoretical calculations reveals that the shortening of the Ir─Ir bond and the reduction of Ir3+ proportion effectively modulate the adsorption energy of the rate‐determining step, thereby significantly promoting the kinetics of the OOH* deprotonation process. These results demonstrate that regulation of lattice distortion is a feasible approach to effectively improve the OER catalytic performance.

Photocatalytic Reduction of CO2 to HCOOH and CO by a Phosphine‐Bipyridine‐Phosphine Ir(III) Catalyst: Photophysics, Nonadiabatic Effects, Mechanism, and Selectivity

AbstractPhotocatalytic CO2 reduction is one of the best solutions to solve the global energy crisis and to realize carbon neutralization. The tetradentate phosphine‐bipyridine (bpy)‐phosphine (PNNP)‐type Ir(III) photocatalyst, Mes‐IrPCY2, was reported with a high HCOOH selectivity but the photocatalytic mechanism remains elusive. Herein, we employ electronic structure methods in combination with radiative, nonradiative, and electron transfer rate calculations, to explore the entire photocatalytic cycle to either HCOOH or CO, based on which a new mechanistic scenario is proposed. The catalytic reduction reaction starts from the generation of the precursor metal‐to‐ligand charge transfer (3MLCT) state. Subsequently, the divergence happens from the 3MLCT state, the single electron transfer (SET) and deprotonation process lead to the formation of one‐electron‐reduced species and Ir(I) species, which initiate the reduction reaction to HCOOH and CO, respectively. Interestingly, the efficient occurrence of proton or electron transfer reduces barriers of critical steps. In addition, nonadiabatic transitions play a nonnegligible role in the cycle. We suggest a lower free‐energy barrier in the reaction‐limiting step and the very efficient SET in 3MLCT are cooperatively responsible for a high HCOOH selectivity. The gained mechanistic insights could help chemists to understand, regulate, and design photocatalytic CO2 reduction reaction of similar function‐integrated molecular photocatalyst.

Photocatalytic Reduction of CO2 to HCOOH and CO by a Phosphine-Bipyridine-Phosphine Ir(III) Catalyst: Photophysics, Nonadiabatic Effects, Mechanism, and Selectivity.

Photocatalytic CO2 reduction is one of the best solutions to solve the global energy crisis and to realize carbon neutralization. The tetradentate phosphine-bipyridine (bpy)-phosphine (PNNP)-type Ir(III) photocatalyst, Mes-IrPCY2, was reported with a high HCOOH selectivity but the photocatalytic mechanism remains elusive. Herein, we employ electronic structure methods in combination with radiative, nonradiative, and electron transfer rate calculations, to explore the entire photocatalytic cycle to either HCOOH or CO, based on which a new mechanistic scenario is proposed. The catalytic reduction reaction starts from the generation of the precursor metal-to-ligand charge transfer (3 MLCT) state. Subsequently, the divergence happens from the 3 MLCT state, the single electron transfer (SET) and deprotonation process lead to the formation of one-electron-reduced species and Ir(I) species, which initiate the reduction reaction to HCOOH and CO, respectively. Interestingly, the efficient occurrence of proton or electron transfer reduces barriers of critical steps. In addition, nonadiabatic transitions play a nonnegligible role in the cycle. We suggest a lower free-energy barrier in the reaction-limiting step and the very efficient SET in 3 MLCT are cooperatively responsible for a high HCOOH selectivity. The gained mechanistic insights could help chemists to understand, regulate, and design photocatalytic CO2 reduction reaction of similar function-integrated molecular photocatalyst.

Aramid nanofiber‐reinforced poly(lactic acid) nanocomposites with enhanced thermal stability, melt‐crystallization rates, and mechanical toughness

AbstractThe main goal of this study is to investigate the impact of aramid nanofiber (ANF) on enhancing various properties of poly(lactic acid) (PLA), including thermal stability, crystallization rates, melt‐rheological behavior, and mechanical properties. To achieve this, ANF fillers were produced using a modified deprotonation process from commercial aramid fibers, and a masterbatch (PLA/ANF = 90/10 by wt%) was prepared through solution blending and drying. The masterbatch was then combined with neat PLA through melt‐blending to create a range of PLA nanocomposites containing 1–10 wt% ANF loadings. Microscopic and spectroscopic analyses confirmed the uniform dispersion and intermolecular interaction of ANFs within the PLA matrix, respectively. As a result, the nanocomposites exhibited a slight increase in glass transition temperature with higher ANF loading, while the cold‐crystallization temperature decreased due to ANFs acting as nucleating agents during PLA crystallization. Isothermal crystallization analysis confirmed accelerated melt‐crystallization rates in nanocomposites with greater ANF content. The introduction of ANFs enhanced the thermal degradation temperature of the PLA matrix and the 700°C residue of the nanocomposites, attributed to ANFs' barrier and flame retardant effects on PLA. Moreover, the nanocomposites with higher ANF loading demonstrated superior tensile strength, strain at break, toughness, and impact strength owing to the effective bonding interactions at the interfaces between the PLA matrix and the ANF fillers.Highlights ANF‐reinforced PLA nanocomposites are prepared by masterbatch melt‐compounding. Uniform dispersion of ANFs in PLA is attained via effective interfacial bonding. ANFs boost the melt‐crystallization of the PLA matrix. ANFs enhance the thermal stability of the PLA matrix. Tensile strength and toughness of PLA are improved with higher ANF content.

Ultrathin heteroatom-doped CeO2 nanosheet assemblies for durable oxygen evolution: Oxygen vacancy engineering to trigger deprotonation

The manipulation of oxygen vacancies (OVs) in metal oxides has progressively emerged as a versatile strategy for improving their catalytic performance. In this study, we aim to enhance the oxygen evolution reaction (OER) performance of cerium oxide (CeO2) by doping heteroatoms (Fe, Co, Ni) to generate additional OVs. We systematically analyzed both the morphology and electronic structure of the obtained CeO2 catalysts. The experimental results revealed the self-assembly of two-dimensional (2D) CeO2 nanosheets, with an approximate thickness of ∼1.7 nm, into 2D nanosheet assemblies (NSAs). Moreover, the incorporation of heteroatoms into the CeO2 matrix promoted the formation of OVs, resulting in a significant enhancement of the OER performance of CeO2. Among them, the Co-doped CeO2 NSAs sample displayed the highest activity and durability, with almost negligible activity loss during extended operating periods. The roles of heteroatom doping in improving OER activity were explored by DFT calculations. The produced OVs improve the adsorption of hydroxyl groups (OH−), promote the deprotonation process, and increase more active sites. These findings suggest that doping CeO2 with heteroatoms is a promising strategy for improving electrocatalytic OER activity, with great potential for the development of clean energy technologies, including but not limited to water splitting and fuel cells.

Concerted proton-coupled electron transfer promotes NiCoP nanowire arrays for efficient overall water splitting at industrial-level current density

Inspired by the oxygen-evolving complex (OEC) in photosystem II (PS-II), self-supported Fe-doped NiCoP nanowire arrays modified with carboxylate (NCFCP@NF) is constructed to boost industrial-level overall water splitting by the concerted proton-coupled electron transfer (c-PET) mechanism. NCFCP@NF exhibits 283 mV at the current density of 3000 mA cm−2 for HER, which is attributed to the H2O adsorption sites provided by Fe and Ni, as well as the electrons provided by carboxyl ligand. Also, NCFCP@NF shows remarkable OER catalytic activity with overpotential of 329 mV to afford 3000 mA cm−2. Herein, the introduction of Fe promotes the formation of *OOH, and carboxyl ligand accelerate the deprotonation process of OER. Furthermore, NCFCP@NF displays the ultralong durability (200 h) at 1000 mA cm−2 for overall water splitting. This study offers a new perspective on designing efficient overall water splitting catalyst at the industrial-level current density by the concerted proton-coupled electron transfer mechanism.

Zn-Leaching Induced Rapid Self-Reconstruction of NiFe-Layered Double Hydroxides for Boosted Oxygen Evolution Reaction.

Optimizing the active centers through reconstruction is recognized as the key to construct high-performance oxygen evolution reaction (OER) catalysts. Herein, a simple and rapid in situ leaching strategy to promote the self-reconstruction of NiFe-layered double hydroxides (LDHs) catalysts is reported. The trace Zn dopants are introduced in advance by a facile and one-step hydrothermal method, followed by leaching over the electrochemical activation process, which can remarkably reduce the formation potential of NiFeOOH active centers to enable the deeper self-reconstruction for the formation of abundant highly active centers. Moreover, the self-restructured NiFeOOH-VZn cannot only significantly lower the dehydrogenation energy barrier for the transformation from Ni(OH)2 to NiOOH, but also decrease the free energy barrier of rate determining step for the *OH converted to *O through a deprotonation process, thus significantly boosting the OER behaviors. As a proof of concept, the obtained NiFeOOH-VZn catalyst just requires a low overpotential of 240mV at 10mAcm-2, and delivers robust stability at 50mA cm-2 over 120h, which outperforms the benchmark of noble metal RuO2 and those of most non-noble metal catalysts ever reported.

Electrochemical enabled desaturated β-C(sp3)-H sulfonylation and phosphonylation of cyclic amines

Herein, we reported an efficient and straightforward method to realize desaturated β-C(sp3)-H sulfonylation and phosphonylation of cyclic amines driven by electrochemistry using catalytic amounts of CP2Fe as the redox mediator. This protocol which had good functional group compatibility, provided the desired enaminyl sulfone and enaminyl phosphine oxide products with high chemo- and regio-selectivity under mild conditions. Several mechanistic studies have suggested that cyclic amines underwent multiple single-electron oxidation and deprotonation processes, followed by a capture step involving either a sulfonyl radical or a phosphonyl radical, ultimately leading to the desired products.

One-atom-thick hexagonal boron nitride co-catalyst for enhanced oxygen evolution reactions

Developing efficient (co-)catalysts with optimized interfacial mass and charge transport properties is essential for enhanced oxygen evolution reaction (OER) via electrochemical water splitting. Here we report one-atom-thick hexagonal boron nitride (hBN) as an attractive co-catalyst with enhanced OER efficiency. Various electrocatalytic electrodes are encapsulated with centimeter-sized hBN films which are dense and impermeable so that only the hBN surfaces are directly exposed to reactive species. For example, hBN covered Ni-Fe (oxy)hydroxide anodes show an ultralow Tafel slope of ~30 mV dec−1 with improved reaction current by about 10 times, reaching ~2000 mA cm−2 (at an overpotential of ~490 mV) for over 150 h. The mass activity of hBN co-catalyst is found exceeding that of commercialized catalysts by up to five orders of magnitude. Using isotope experiments and simulations, we attribute the results to the adsorption of oxygen-containing intermediates at the insulating co-catalyst, where localized electrons facilitate the deprotonation processes at electrodes. Little impedance to electron transfer is observed from hBN film encapsulation due to its ultimate thickness. Therefore, our work also offers insights into mechanisms of interfacial reactions at the very first atomic layer of electrodes.

Outstanding proton conductivity over wide temperature and humidity ranges and enhanced mechanical, thermal stabilities for surface-modified MIL-101-Cr-NH2/Nafion composite membranes

High-performance proton exchange membranes are of great importance for fuel cells. Here, we have synthesized polycarboxylate plasticizer modified MIL-101-Cr-NH2 (PCP-MCN), a kind of hybrid metal−organic framework, which exhibits a superior proton conductivity. PCP-MCN nanoparticles are used as additives to fabricate PCP-MCN/Nafion composite membranes. Microstructures and characteristics of PCP-MCN and these membranes have been extensively investigated. Significant enhancement in proton conduction for PCP-MCN around 55 °C is interestingly found due to the thermal motion of the PCP molecular chains. Robust mechanical properties and higher thermal decomposition temperature of the composite membranes are directly ascribed to strong intermolecular interactions between PCP-MCN and Nafion side chains, i.e. the formation of substantial acid–base pairs (-SO3-⋅⋅⋅+H–NH-), which further improves compatibility between additive and Nafion matrix. At the same humidity and temperature condition, the water uptake of composite membranes significantly increases due to the incorporation of porous additives with abundant functional groups and thus less crystallinity degree in comparison to pristine Nafion. Proton conductivity (σ) over wide ranges of humidities (30 − 100 % RH at 25 °C) and temperatures (30 − 98 °C at 100 % RH) for prepared membranes is measured. The σ in PCP-MCN/Nafion composite membranes is remarkably enhanced, i.e. 0.245 S/cm for PCP-MCN-3wt.%/Nafion is twice that of Nafion membrane at 98 °C and 100 % RH, because of the establishment of well-interconnected proton transport ionic water channels and perhaps faster protonation–deprotonation processes. The composite membranes possess weak humidity-dependence of proton transport and higher water uptake due to excellent water retention ability of PCP-MCN. In particular, when 3 wt.% PCP-MCN was added to Nafion, the power density of a single-cell fabricated with this composite membrane reaches impressively 0.480, 1.098 W/cm2 under 40 % RH, 100 % RH at 60 °C, respectively, guaranteeing it to be a promising proton exchange membrane.

Colorimetric and fluorimetric detection of CN– ion using a highly selective and sensitive chemosensor derived from coumarin-hydrazone

Novel chemosensors, including coumarin hydrazide, were designed and synthesized by a three-step synthesis sequence starting from 7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide. General spectroscopic methods (FT-IR, 1H/13C NMR, and HRMS) were used to characterize all produced chemosensors. These chemosensors demonstrate the ability to detect cyanide (CN–) anion by shifting absorption and fluorescence turn-off response in DMSO. The reaction mechanism between the synthesized chemosensors and the CN– anion involves deprotonation and addition processes; as determined by dipole-dipole interactions, reversibility, 1H NMR experiments, and theoretical studies. With limit of detection (LOD) values of 0.25 μM and 0.15 μM for 3a and 3b, respectively, these chemosensors exhibit exceptional detection ability and demonstrate the high effectiveness of their use for CN– anion determination.