Uncovering the Shuttle Effect in Organic Batteries and Counter-Strategies Thereof: A Case Study of the N,N′-Dimethylphenazine Cathode

The main drawback of organic electrode materials is their solubility in the electrolyte, leading to the shuttle effect. Using N,N′-dimethylphenazine (DMPZ) as a highly soluble cathode material, and its PF₆⁻ and triflimide salts as models for its first oxidation state, a poor correlation was found between solubility and battery operability. Extensive electrochemical experiments suggest that the shuttle effect is unlikely to be mediated by molecular diffusion as commonly understood, but rather by electron-hopping via the electron self-exchange reaction based on spectroscopic results. These findings led to two counter-strategies to prevent the hopping process: the pre-treatment of the anode to form a solid–electrolyte interface and using DMPZ salt rather than neutral DMPZ as the active material. These strategies improved coulombic efficiency and capacity retention, demonstrating that solubility of organic materials does not necessarily exclude their applications in batteries.     

Solid‐State Electrolyte Anchored with a Carboxylated Azo Compound for All‐Solid‐State Lithium Batteries

Organic electrode materials are promising for green and sustainable lithium‐ion batteries. However, the high solubility of organic materials in the liquid electrolyte results in the shuttle reaction and fast capacity decay. Herein, azo compounds are firstly applied in all‐solid‐state lithium batteries (ASSLB) to suppress the dissolution challenge. Due to the high compatibility of azobenzene (AB) based compounds to Li₃PS₄ (LPS) solid electrolyte, the LPS solid electrolyte is used to prevent the dissolution and shuttle reaction of AB. To maintain the low interface resistance during the large volume change upon cycling, a carboxylate group is added into AB to provide 4‐(phenylazo) benzoic acid lithium salt (PBALS), which could bond with LPS solid electrolyte via the ionic bonding between oxygen in PBALS and lithium ion in LPS. The ionic bonding between the active material and solid electrolyte stabilizes the contact interface and enables the stable cycle life of PBALS in ASSLB.     

Structural Polymorphism and Thin Film Transistor Behavior in the Fullerene Framework Molecule 5,6;11,12‐di‐o‐Phenylenetetracene

The molecular structure of the hydrocarbon 5,6;11,12‐di‐o‐phenylenetetracene (DOPT), its material characterization and evaluation of electronic properties is reported for the first time. A single‐crystal X‐ray study reveals two different motifs of intramolecular overlap with herringbone‐type arrangement displaying either face‐to‐edge or co‐facial face‐to‐face packing depicting intensive π–π interactions. Density functional theory (DFT) calculations underpin that a favorable electronic transport mechanism occurs by a charge hopping process due to a π‐bond overlap in the DOPT polymorph with co‐facial arene orientation. The performance of polycrystalline DOPT films as active organic semiconducting layer in a state‐of‐the‐art organic field effect transistor (OFET) device was evaluated and proves to be film thickness dependent. For 40 nm layer thickness it displays a saturation hole mobility (μ_hole) of up to 0.01 cm² V^?1 s^?1 and an on/off‐ratio (I_on/I_off) of 1.5×10³.     

Theoretical Study of the Substituent Effects on the Nonlinear Optical Properties of a Room‐Temperature‐Stable Organic Electride

Excess‐electron compounds can be considered as novel candidates for nonlinear optical (NLO) materials because of their large static first hyperpolarizabilities (β₀). A room‐temperature‐stable, excess‐electron compound, that is, the organic electride Na@(TriPip222), was successfully synthesized by the Dye group (J. Am. Chem. Soc. 2005 , 127, 12416). In this work, the β₀ of this electride was first evaluated to be 1.13×10⁶ au, which revealed its potential as a high‐performance NLO material. In particular, the substituent effects of different substituents on the structure, electride character, and NLO response of this electride were systemically studied for the first time by density functional theory calculations. The results revealed that the β₀ of Na@(TriPip222) could be further increased to 8.30×10⁶ au by introducing a fluoro substituent, whereas its NLO response completely disappeared if one nitryl group was introduced because the nitro‐group substitution deprived the material of its electride identity. Moreover, herein the dependence of the NLO properties on the number of substituents and their relative positions was also detected in multifluoro‐substituted Na@(TriPip222) compounds.     

Alcohol‐Processable Organic Amorphous Electrolytes as an Effective Electron‐Injection Layer for Organic Light‐Emitting Diodes

A new series of monoammonium‐based organic electrolytes with the tetrafluoroborate (BF₄^?) counteranion have been synthesized. Replacing the pendant ethyl groups in the fluorenyl unit with 4‐ethoxyphenyl groups dramatically improves both solubility and morphological stability. The characterization of the alcohol‐processable amorphous ionic compounds as an electron‐injection layer in organic light‐emitting diodes (OLEDs) reveals that the organic electrolyte that comprises a rigid linear‐conjugated unit provides better device performance, with respect to its counterpart containing a branched bulky moiety. The capability of these compounds to facilitate electron injection from air‐stable aluminum metal is preliminarily discussed on the basis of the investigations of the electron‐only devices and photovoltaic experiments.     

In Situ Small‐Angle X‐ray Scattering Investigation of the Formation of Dual‐Mesoporous Materials

The formation of a 2D‐hexagonal (p6m) silica‐based hybrid dual‐mesoporous material is investigated in situ by using synchrotron time‐resolved small‐angle X‐ray scattering (SAXS). The material is synthesized from a mixed micellar solution of a nonionic fluorinated surfactant, R^F₈(EO)₉ (EO=ethylene oxide) and a nonionic triblock copolymer, P123. Both mesoporous networks, with pore dimensions of 3.3 and 8.5 nm respectively, are observed by nitrogen sorption, transmission electron microscopy (TEM), and SAXS. The in situ SAXS experiments reveal that mesophase formation occurs in two steps. First the nucleation and growth of a primary 2D‐hexagonal network (N1), associated with mixed micelles containing P123, then subsequent formation of a second network (N2), associated with micelles of pure R^F₈(EO)₉. The data obtained from SAXS and TEM suggest that the N1 network is used as a nucleation center for the formation of the N2 network, which would result in the formation of a grain with two mesopore sizes. Understanding the mechanism of the formation of such materials is an important step towards the synthesis of more‐complex materials by fine tuning the porosity.     

A Highly Energetic N‐Rich Metal–Organic Framework as a New High‐Energy‐Density Material

Metal–organic framework (MOF)‐based energetic material [Cu₃(MA)₂(N₃)₃] ( 1 ; MA=melamine) was synthesized and structurally characterized (47.55 % N). The structural analysis revealed the existence of unusual multiwalled tubular channels and interweaving of single and double helical units in 1 . The standard molar enthalpy of formation was found to be 1788.73 kJ mol^?1, which is the highest value among previously reported MOF‐based energetic materials. The calculated detonation properties showed that 1 can be used as a potential explosive. Sensitivity tests revealed that 1 is insensitive and thus can function as a high‐energy‐density material with a favorable level of safety.     

Wintersweet‐Flower‐Like CoFe2O4/MWCNTs Hybrid Material for High‐Capacity Reversible Lithium Storage

CoFe₂O₄/multiwalled carbon nanotubes (MWCNTs) hybrid materials were synthesized by a hydrothermal method. Field emission scanning electron microscopy and transmission electron microscopy analysis confirmed the morphology of the as‐prepared hybrid material resembling wintersweet flower “buds on branches”, in which CoFe₂O₄ nanoclusters, consisting of nanocrystals with a size of 5–10 nm, are anchored along carbon nanotubes. When applied as an anode material in lithium ion batteries, the CoFe₂O₄/MWCNTs hybrid material exhibited a high performance for reversible lithium storage. In particular, the hybrid anode material delivered reversible lithium storage capacities of 809, 765, 539, and 359 mA h g^?1 at current densities of 180, 450, 900, and 1800 mA g^?1, respectively. The superior performance of CoFe₂O₄/MWCNTs hybrid materials could be ascribed to the synergistic pinning effect of the wintersweet‐flower‐like nanoarchitecture. This strategy could also be applied to synthesize other metal oxide/CNTs hybrid materials as high‐capacity anode materials for lithium ion batteries.     

Non‐covalent Immobilization of Iron‐triazole (Fe(Htrz)3) Molecular Mediator in Mesoporous Silica Films for the Electrochemical Detection of Hydrogen Peroxide

Mesoporous silica thin films encapsulating a molecular iron‐triazole complex, Fe(Htrz)₃ (Htrz=1,2,4,‐1H‐triazole), have been generated by electrochemically assisted self‐assembly (EASA) on indium‐tin oxide (ITO) electrode. The obtained modified electrodes are characterized by well‐defined voltammetric signals corresponding to the Fe^II/III centers of the Fe(Htrz)₃ species immobilized into the films, indicating fast electron transfer processes and stable operational stability. This is due to the presence of a high density of redox probes in the material (1.6×10^?4 mol g^?1 Fe(Htrz)₃ in the mesoporous silica film) enabling efficient charge transport by electron hopping. The mesoporous films are uniformly deposited over the whole electrode surface and they are characterized by a thickness of 110 nm and a wormlike mesostructure directed by the template role played by Fe(Htrz)₃ species in the EASA process. These species are durably immobilized in the material (they are not removed by solvent extraction). The composite mesoporous material (denoted Fe(Htrz)₃@SiO₂) is then used for the electrocatalytic detection of hydrogen peroxide, which can be performed by amperometry at an applied potential of ?0.4 V versus Ag/AgCl and by flow injection analysis. The organic‐inorganic hybrid film electrode displays good sensitivity for H₂O₂ sensing over a dynamic range from 5 to 300 μM, with a detection limit estimated at 2 μM.     

Boron‐Functionalized Graphene Oxide‐Organic Frameworks for Highly Efficient CO2 Capture

The capture and storage of CO₂ have been suggested as an effective strategy to reduce the global emissions of greenhouse gases. Hence, in recent years, many studies have been carried out to develop highly efficient materials for capturing CO₂. Until today, different types of porous materials, such as zeolites, porous carbons, N/B‐doped porous carbons or metal‐organic frameworks (MOFs), have been studied for CO₂ capture. Herein, the CO₂ capture performance of new hybrid materials, graphene‐organic frameworks (GOFs) is described. The GOFs were synthesized under mild conditions through a solvothermal process using graphene oxide (GO) as a starting material and benzene 1,4‐diboronic acid as an organic linker. Interestingly, the obtained GOF shows a high surface area (506 m² g⁻¹) which is around 11 times higher than that of GO (46 m² g⁻¹), indicating that the organic modification on the GO surface is an effective way of preparing a porous structure using GO. Our synthetic approach is quite simple, facile, and fast, compared with many other approaches reported previously. The synthesized GOF exhibits a very large CO₂ capacity of 4.95 mmol g⁻¹ at 298 K (1 bar), which is higher those of other porous materials or carbon‐based materials, along with an excellent CO₂/N₂ selectivity of 48.8.     

An ATR‐FTIR Study on the Effect of Molecular Structural Variations on the CO2 Absorption Characteristics of Heterocyclic Amines,Part II

This paper reports on an ATR‐FTIR spectroscopic investigation of the CO₂ absorption characteristics of a series of heterocyclic diamines: hexahydropyrimidine (HHPY), 2‐methyl and 2,2‐dimethylhexahydropyrimidine (MHHPY and DMHHPY), hexahydropyridazine (HHPZ), piperazine (PZ) and 2,5‐ and 2,6‐dimethylpiperazine (2,6‐DMPZ and 2,5‐DMPZ). By using in situ ATR‐FTIR the structure–activity relationship of the reaction between heterocyclic diamines and CO₂ is probed. PZ forms a hydrolysis‐resistant carbamate derivative, while HHPY forms a more labile carbamate species with increased susceptibility to hydrolysis, particularly at higher CO₂ loadings (>0.5 mol CO₂/mol amine). HHPY exhibits similar reactivity toward CO₂ to PZ, but with improved aqueous solubility. The α‐methyl‐substituted MHHPY favours HCO₃^? formation, but MHHPY exhibits comparable CO₂ absorption capacity to conventional amines MEA and DEA. MHHPY show improved reactivity compared to the conventional α‐methyl‐ substituted primary amine 2‐amino‐2‐methyl‐1‐propanol. DMHHPY is representative of blended amine systems, and its reactivity highlights the advantages of such systems. HHPZ is relatively unreactive towards CO₂. The CO₂ absorption capacity C_A (mol CO₂/mol amine) and initial rates of absorption R_IA (mol CO₂/mol amine min^?1) for each reactive diamine are determined: PZ: C_A=0.92, R_IA=0.045; 2,6‐DMPZ: C_A=0.86, R_IA=0.025; 2,5‐DMPZ: C_A=0.88, R_IA=0.018; HHPY: C_A=0.85, R_IA=0.032; MHHPY: C_A=0.86, R_IA=0.018; DMHHPY: C_A=1.1, R_IA=0.032; and HHPZ: no reaction. Calculations at the B3LYP/6‐31+G** and MP2/6‐31+G** calculations show that the substitution patterns of the heterocyclic diamines affect carbamate stability, which influences hydrolysis rates.     

Nicotine,acetanilide and urea multi‐level 2H‐, 13C‐ and 15N‐abundance reference materials for continuous‐flow isotope ratio mass spectrometry

Accurate determinations of stable isotope ratios require a calibration using at least two reference materials with different isotopic compositions to anchor the isotopic scale and compensate for differences in machine slope. Ideally, the δ values of these reference materials should bracket the isotopic range of samples with unknown δ values. While the practice of analyzing two isotopically distinct reference materials is common for water (VSMOW‐SLAP) and carbonates (NBS 19 and L‐SVEC), the lack of widely available organic reference materials with distinct isotopic composition has hindered the practice when analyzing organic materials by elemental analysis/isotope ratio mass spectrometry (EA‐IRMS). At present only L‐glutamic acids USGS40 and USGS41 satisfy these requirements for δ¹³C and δ¹⁵N, with the limitation that L‐glutamic acid is not suitable for analysis by gas chromatography (GC). We describe the development and quality testing of (i) four nicotine laboratory reference materials for on‐line (i.e. continuous flow) hydrogen reductive gas chromatography‐isotope ratio mass‐spectrometry (GC‐IRMS), (ii) five nicotines for oxidative C, N gas chromatography‐combustion‐isotope ratio mass‐spectrometry (GC‐C‐IRMS, or GC‐IRMS), and (iii) also three acetanilide and three urea reference materials for on‐line oxidative EA‐IRMS for C and N. Isotopic off‐line calibration against international stable isotope measurement standards at Indiana University adhered to the ‘principle of identical treatment’. The new reference materials cover the following isotopic ranges: δ²H_nicotine ?162 to ?45‰, δ¹³C_nicotine ?30.05 to +7.72‰, δ¹⁵N_nicotine ?6.03 to +33.62‰; δ¹⁵N_acetanilide +1.18 to +40.57‰; δ¹³C_urea ?34.13 to +11.71‰, δ¹⁵N_urea +0.26 to +40.61‰ (recommended δ values refer to calibration with NBS 19, L‐SVEC, IAEA‐N‐1, and IAEA‐N‐2). Nicotines fill a gap as the first organic nitrogen stable isotope reference materials for GC‐IRMS that are available with different δ¹⁵N values. Comparative δ¹³C and δ¹⁵N on‐line EA‐IRMS data from 14 volunteering laboratories document the usefulness and reliability of acetanilides and ureas as EA‐IRMS reference materials. Published in 2009 by John Wiley & Sons, Ltd.     

Carbon‐Dot‐Sensitized,Nitrogen‐Doped TiO2 in Mesoporous Silica for Water Decontamination through Nonhydrophobic Enrichment–Degradation Mode

Mesoporous silica synthesized from the cocondensation of tetraethoxysilane and silylated carbon dots containing an amide group has been adopted as the carrier for the in situ growth of TiO₂ through an impregnation–hydrothermal crystallization process. Benefitting from initial complexation between the titania precursor and carbon dot, highly dispersed anatase TiO₂ nanoparticles can be formed inside the mesoporous channel. The hybrid material possesses an ordered hexagonal mesostructure with p6mm symmetry, a high specific surface area (446.27 m² g^?1), large pore volume (0.57 cm³ g^?1), uniform pore size (5.11 nm), and a wide absorption band between λ=300 and 550 nm. TiO₂ nanocrystals are anchored to the carbon dot through Ti?O?N and Ti?O?C bonds, as revealed by X‐ray photoelectron spectroscopy. Moreover, the nitrogen doping of TiO₂ is also verified by the formation of the Ti?N bond. This composite shows excellent adsorption capabilities for 2,4‐dichlorophenol and acid orange 7, with an electron‐deficient aromatic ring, through electron donor–acceptor interactions between the carbon dot and organic compounds instead of the hydrophobic effect, as analyzed by the contact angle analysis. The composite can be photocatalytically recycled through visible‐light irradiation after adsorption. The narrowed band gap, as a result of nitrogen doping, and the photosensitization effect of carbon dots are revealed to be coresponsible for the visible‐light activity of TiO₂. The adsorption capacity does not suffer any clear losses after being recycled three times.     

Graphene‐Based Composite with γ‐Fe2O3 Nanoparticle for the High‐Performance Removal of Endocrine‐Disrupting Compounds from Water

Graphene is a 2D sp²‐hybridized carbon sheet and an ideal material for the adsorption‐based separation of organic pollutants. However, such potential applications of graphene are largely limited, owing to their poor solubility and extensive aggregation properties through graphene? graphene interactions. Herein, we report the synthesis of graphene‐based composites with γ‐Fe₂O₃ nanoparticle for the high‐performance removal of endocrine‐disrupting compounds (EDC) from water. The γ‐Fe₂O₃ nanoparticles partially inhibit these graphene? graphene interactions and offer water dispersibility of the composite without compromising much of the high surface area of graphene. In their dispersed form, the graphene component offers the efficient adsorption of EDC, whilst the magnetic iron‐oxide component offers easier magnetic separation of adsorbed EDC.     

Solution‐Processable n‐Type Semiconductors Based on Unsymmetrical Naphthalene Imides: Synthesis,Characterization, and Applications in Field‐Effect Transistors

A series of unsymmetrical naphthalene imide derivatives ( 1a , 1b , 2 , 3 , 4 , 5 ) with high electron affinity was synthesized and used in n‐channel organic field‐effect transistors (OFETs). They have very good solubility in common organic solvents and good thermal stability up to 320 °C. Their photophysical, electrochemical, and thermal properties were investigated in detail. They showed low‐lying LUMO energy levels from ?3.90 to ?4.15 eV owing to a strong electron‐withdrawing character. Solution‐processed thin‐film OFETs based on 1a , 1b , 2 , 3 , 4 were measured in both N₂ and air. They all showed n‐type FET behavior. The liquid‐crystalline compounds 1a , 1b , and 3 showed good performance owing to the self‐healing properties of the film in the liquid‐crystal phase. Compound 3 has an electron mobility of up to 0.016 cm² V^?1 s^?1 and current on/off ratios of 10⁴–10⁵.     

Gem‐dinitromethyl‐substituted Energetic Metal–Organic Framework based on 1,2,3‐Triazole from in situ Controllable Synthesis

Synthesizing energetic metal–organic frameworks at ambient temperature and pressure has been always a challenge in the research area of energetic materials. In this work, through in situ controllable synthesis, energetic metal–organic framework gem‐dinitromethyl‐substituted dipotassium 4,5‐bis(dinitromethyl)‐1,2,3‐triazole with a “cage‐like” crystal packing was obtained and characterized. Most importantly, for the first time, we found that it could be successfully afforded with a catalytic effect of trifluoroacetic acid. This new compound exhibited its high density (2.04 g cm^?3) at ambient temperature, superior detonation velocity (8715 m s^?1) to that of lead azide (5877 m s^?1) and comparable to that of RDX (8748 m s^?1). Its detonation products are mainly N₂ (48.1 %), suggesting it is also a green energetic material. The above‐mentioned performance indicates its potential applications in detonator devices as lead‐free primary explosive.     

Two‐Dimensional Perovskite Oxynitride K2LaTa2O6N with an H+/K+ Exchangeability in Aqueous Solution Forming a Stable Photocatalyst for Visible‐Light H2 Evolution

Undoped layered oxynitrides have not been considered as promising H₂‐evolution photocatalysts because of the low chemical stability of oxynitrides in aqueous solution. Here, we demonstrate the synthesis of a new layered perovskite oxynitride, K₂LaTa₂O₆N, as an exceptional example of a water‐tolerant photocatalyst for H₂ evolution under visible light. The material underwent in‐situ H⁺/K⁺ exchange in aqueous solution while keeping its visible‐light‐absorption capability. Protonated K₂LaTa₂O₆N, modified with an Ir cocatalyst, exhibited excellent catalytic activity toward H₂ evolution in the presence of I^? as an electron donor and under visible light; the activity was six times higher than Pt/ZrO₂/TaON, one of the best‐performing oxynitride photocatalysts for H₂ evolution. Overall water splitting was also achieved using the Ir‐loaded, protonated K₂LaTa₂O₆N in combination with Cs‐modified Pt/WO₃ as an O₂ evolution photocatalyst in the presence of an I₃^?/I^? shuttle redox couple.     

Non‐Conjugated Dicarboxylate Anode Materials for Electrochemical Cells

Classical organic anode materials for Na‐ion batteries are mostly based on conjugated carboxylate compounds, which can stabilize added electrons by the double‐bond reformation mechanism. Now, 1,4‐cyclohexanedicarboxylic acid (C₈H₁₂O₄, CHDA) with a non‐conjugated ring (?C₆H₁₀?) connected with carboxylates is shown to undergo electrochemical reactions with two Na ions, delivering a high charge specific capacity of 284 mA h g^?1 (249 mA h g^?1 after 100 cycles), and good rate performance. First‐principles calculations indicate that hydrogen‐transfer‐mediated orbital conversion from antibonding π* to bonding σ stabilize two added electrons, and reactive intermediate with unpaired electron is suppressed by localization of σ‐bonds and steric hindrance. An advantage of CHDA as an anode material is good reversibility and relatively constant voltage. A large variety of organic non‐conjugated compounds are predicted to be promising anode materials for sodium‐ion batteries.     

Room‐Temperature Ferroelectric Material Composed of a Two‐Dimensional Metal Halide Double Perovskite for X‐ray Detection

Although two‐dimensional (2D) metal–halide double perovskites display versatile physical properties due to their huge structural compatibility, room‐temperature ferroelectric behavior has not yet been reported for this fascinating family. Here, we designed a room‐temperature ferroelectric material composed of 2D halide double perovskites, (chloropropylammonium)₄AgBiBr₈, using an organic asymmetric dipolar ligand. It exhibits concrete ferroelectricity, including a Curie temperature of 305 K and a notable spontaneous polarization of ≈3.2 μC cm^?2, triggered by dynamic ordering of the organic cation and the tilting motion of heterometallic AgBr₆/BiBr₆ octahedra. Besides, the alternating array of inorganic perovskite sheets and organic cations endows large mobility‐lifetime product (μτ=1.0×10^?3 cm² V^?1) for detecting X‐ray photons, which is almost tenfold higher than that of CH₃NH₃PbI₃ wafers. As far as we know, this is the first study on an X‐ray‐sensitive ferroelectric material composed of 2D halide double perovskites. Our findings afford a promising platform for exploring new ferroelectric materials toward further device applications.     

Versatile Room‐Temperature‐Phosphorescent Materials Prepared from N‐Substituted Naphthalimides: Emission Enhancement and Chemical Conjugation

Purely organic materials with room‐temperature phosphorescence (RTP) are currently under intense investigation because of their potential applications in sensing, imaging, and displaying. Inspired by certain organometallic systems, where ligand‐localized phosphorescence (³π‐π*) is mediated by ligand‐to‐metal or metal‐to‐ligand charge transfer (CT) states, we now show that donor‐to‐acceptor CT states from the same organic molecule can also mediate π‐localized RTP. In the model system of N‐substituted naphthalimides (NNIs), the relatively large energy gap between the NNI‐localized ¹π‐π* and ³π‐π* states of the aromatic ring can be bridged by intramolecular CT states when the NNI is chemically modified with an electron donor. These NNI‐based RTP materials can be easily conjugated to both synthetic and natural macromolecules, which can be used for RTP microscopy.