Strong Electron Affinity Research Articles

Physicochemical Properties of Water in Contact with Nanobubbles Generated by CO2‐Hydrate Dissociation: An Investigation from Experiment and Molecular‐Dynamics Simulation

AbstractThe study investigates CO2‐nanobubbles (NBs) generated from gas‐hydrate dissociation, exploring their impact on the physicochemical properties of liquid water. Raman spectroscopy evidenced a slight increase in the Raman‐band intensity, suggesting enhanced total hydration‐layer water‐dipole moment and polarity without affecting water molecule structuring. Furthermore, an overall decreasing trend for the zeta potential of NB solution can be observed due to the strong electron affinity on the surface of CO2 bulk NBs, probably caused by a negative charge accumulation. These findings are in good qualitative accord with molecular‐dynamics (MD) simulation results, wherein water can induce a small dipole moment of about 0.16 D for CO2 NBs, thereby increasing the polarity of the system. Due to the interaction between water molecules, the Coulombic or electrostatic forces increase in the presence of NBs compared to pure water, which can reflect the increase in the dipole moment of water molecules in the presence of NBs. The presence of NBs strengthens the local hydrogen‐bond network, leading to higher‐frequency vibrations. Additionally, NBs amplify the intrinsic electric field of the aqueous solution, causing the gas‐water interface to exhibit negatively charged characteristics, dependent on NB size. Molecular simulations agree qualitatively with experiments, emphasizing their utility in studying NB evolution in water.

High-throughput phase field simulation and machine learning for predicting the breakdown performance of all-organic composites

All-organic dielectric polymers are materials of choice for modern power electronics and high-density energy storage, and their performance can be significantly improved by doping trace amounts of organic molecular semiconductors with strong electron-affinity energy to suppress charge conduction losses. Insight into the breakdown mechanism of polymers/organic molecular semiconductor composites is essential for the design of high-performance dielectric polymers. This study investigates the impact of the doping concentration of organic molecular semiconductors, dielectric constants, and trap depths on the breakdown performance of dielectric polymers under high temperature and electric fields. A modified phase-field model, incorporating deep traps and carriers’ coulomb capture radius, has been developed to facilitate high-throughput simulations of electrical breakdown in polymer/organic molecular semiconductor composites. This work accurately predicted the breakdown strength of all-organic composites using high-throughput phase-field simulation data as input for machine learning, which provides crucial theoretical support for designing all-organic composite dielectric polymers for energy storage capacitors under extreme conditions.

Chain conformation and aggregation structure regulation of an efficient acceptor–acceptor type photovoltaic polymer

Two novel acceptor1–acceptor2 (A1–A2) typed polymer donors with strong electron affinity were finely designed and tuned through the alkyl side chains. Their different H/J-aggregation behaviors and conformations obviously affected the corresponding nano morphology device performance.

A planar electronic acceptor motif contributing to NIR-II AIEgen with combined imaging and therapeutic applications.

Designing molecules with donor-acceptor-donor (D-A-D) architecture plays an important role in obtaining second near-infrared region (NIR-II, 1000-1700 nm) fluorescent dyes for biomedical applications; however, this always comes with a challenge due to very limited electronic acceptors. On the other hand, to endow NIR-II fluorescent dyes with combined therapeutic applications, trivial molecular design is indispensable. Herein, we propose a pyrazine-based planar electronic acceptor with a strong electron affinity, which can be used to develop NIR-II fluorescent dyes. By structurally attaching two classical triphenylamine electronic donors to it, a basic D-A-D module, namely Py-NIR, can be generated. The planarity of the electronic acceptor is crucial to induce a distinct NIR-II emission peaking at ∼1100 nm. The unique construction of the electronic acceptor can cause a twisted and flexible molecular conformation by the repulsive effect between the donors, which is essential to the aggregation-induced emission (AIE) property. The tuned intramolecular motions and twisted D-A pair brought by the electronic acceptor can lead to a remarkable photothermal conversion with an efficiency of 56.1% and induce a type I photosensitization with a favorable hydroxyl radical (OH˙) formation. Note that no additional measures are adopted in the molecular design, providing an ideal platform to realize NIR-II fluorescent probes with synergetic functions based on such an acceptor. Besides, the nanoparticles of Py-NIR can exhibit excellent NIR-II fluorescence imaging towards orthotopic 4T1 breast tumors in living mice with a high sensitivity and contrast. Combined with photothermal imaging and photoacoustic imaging caused by the thermal effect, the imaging-guided photoablation of tumors can be well performed. Our work has created a new opportunity to develop NIR-II fluorescent probes for accelerating biomedical applications.

Design of donor-acceptor conjugated polymers based on diketopyrrolopyrrole for NIR-II multifunctional imaging.

Diketopyrrolopyrrole (DPP) is an excellent photosensitizer and photothermal agent with the advantages of good planarity, strong electron affinity, high electron mobility, easy purification, easy structural modification and high molar absorption coefficient. It is regarded as one of the ideal choices for the design and synthesis of efficient organic photovoltaic materials. Therefore, two kinds of donor-acceptor (D-A) conjugated polymers were designed and synthesized with DPP as the acceptor, and their optical properties and applications in the near-infrared region were studied. The quantum yield (QY) of PBDT-DPP is 0.46%, and the highest temperature reached within 10 minutes after irradiation with a 660 nm laser is 60 °C. Another polymer, EDOT-DPP, has a QY of 0.48%, and its semiconductor polymer nanoparticle aqueous solution can reach 60 °C within 12 minutes under laser irradiation, achieving photothermal treatment of nude mice tumors. Both polymer NPs have good biocompatibility and promising applications in bioimaging and photothermal therapy.

Alpha-Terthiophene and its functionalized derivatives from roots of Echinops grijisii to produce potential organic semiconductor materials: A theoretical study

DFT calculations were done to explore the optical and electronic properties of α-Terthiophene (α-TTP) and its functionalized derivates from Echinops grijisii, as potential organic semiconductors (OSCs). The properties estimated by the B3LYP-GD3/6–31 +G(d,p) technique include reorganization energy(λe and λh), ionization potential(IP), electron affinity(EA), and bandgap(Eg). The TD-DFT/CAM-B3LYP approach was also used to explore the λmax at the first excited states in vacuum. α-TTP is considered an n-type material, its functionalization resulted in a decrease in Eg and LUMO energy levels, indicating their potential use as n-type OSCs. All the molecules exhibit lower λe, which is in line with the IP and EA values. Compared to others, 5-Acetyl-α-TTP has stronger EA, lowest Eg, lower λe and LUMO confirming its better performance as n-type OSCs. The visualization of TDM maps, explains local excitation in all molecules. Moreover, the ESP map identifies variance in electron density in the skeletal backbone of studied molecules.

Effects of charge rearrangement on interfacial contact resistance of TiO2/graphite from first-principles calculations

Titanium bipolar plates have been widely employed in fuel cells, due to the high resistance achieved by the oxide film (TiO2). However, that also results in high interfacial contact resistance between the titanium and the gas diffusion layer of graphite, reducing the cells’ efficiency significantly. To improve the conductivity properties, the effects of thirty-five metallic dopants on the contact resistance and electrical conductivity were studied based on the first-principles merged with the Schottky-Mott theory and Boltzmann transport equation. The results show that the contact resistance depends on the charge distribution induced by graphite. The contact resistance depends on the conductivity when the charge depletion and accumulation layer are distributed in the space-charge region. If the charge rearrangement occurs in the heterojunction as a whole, the contact resistance is determined by the electronic injection. In addition, the single conduction path between titanium, oxygen and graphite atoms disappears in the TiO2 doped with Zn, Cd, etc., because those dopants have stronger electron affinity in the heterojunction. While a stronger built-in electric field is formed that can further enhance the electronic conductivity.

Design of novel organoboron small-molecule dyes based on dipolar nitrogen-boron-nitrogen unit for solution-processed photovoltaic devices

The nitrogen-boron-nitrogen (N–B–N) structure combined with strong polar B–N and B←N bonds simultaneously, opens a new window for the development of organoboron photovoltaic materials with narrow band gap and low highest occupied molecular orbital (HOMO) energy level. In this paper, two N–B–N-embedded blocks including boron dipyrromethane (BODIPY) and double B–N bridged bipyridyl (BNBP), are exploited to rationally regulate the band gap and energy level of the resulting material by virtue of their strong electron affinities. Thus, the thiophene as a weak electron-donating part is directly attached to strong electron-withdrawing BODIPY and BNBP respectively, giving much improved photoelectric properties for such simple push-pull architectures. To further improve photoelectric and thermal properties of the material, two novel extended D-π-A-π-D-type organoboron molecules namely BDPTPA and BNBPTPA, in which BODIPY and BNBP as strong electron-deficient core (A) connect strong electron-rich triphenylamine (D) via thiophene π-spacer, are synthesized by Stille reaction between BODIPY/BNBP and “π-D” segment. Therefore, BDPTPA exhibits a preferable electrochemical band gap as small as 1.36 eV close to near-infrared (NIR) region, which is one of the lowest values among the BODIPY-based small-molecule donors (SMDs). Furthermore, BNBPTPA shows stronger light absorption of up to 1.16 × 105 M−1 cm−1, deeper HOMO energy level of −5.28 eV and very excellent thermal stability (Td = 428 °C). It is mentioning that, BNBPTPA is first used as SMD material, blending with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) for solution-processed organic solar cell. Consequently, a reasonable power conversion efficiency (PCE) of 6.78% has been achieved with a satisfactory short-circuit density (Jsc) of 17.27 mA cm−2 and open-circuit voltage (Voc) of 0.87 V, which is the highest efficiency for BNBP-based SMDs so far. Our work demonstrates that a proposed molecular design and synthesis with dipolar N–B–N-containing unit and “π-D” fragment, can greatly broaden the types of new photovoltaic donor materials.

Effect of charge transport on electrical degradation in polypropylene/organic molecular semiconductor composites for HVDC cable insulation

Polypropylene is considered to be the material of choice for environmentally friendly high voltage direct current cable insulation. The high power transmission of electrical energy exposes insulating materials to high temperatures and electric fields, resulting in the degradation of material properties. This paper reports that organic molecular semiconductors with strong electron affinity can effectively modulate electrical properties of polypropylene. The charge injection and transport process are analyzed by considering a combination of relations describing various conduction models in dielectrics, including the Richardson–Schottky (RS) emission and the hopping conduction. Based on the performed experiments, a modified Wiesmann–Zeller (WZ) model is proposed to simulate the electrical treeing process of polypropylene. The electrical treeing results are well verified with the simulation results, which offer a valuable tool for further analysis of the effect of intrinsic barrier height, hopping distance, and activation energy on the electrical degradation in the material. This work provides an insightful analysis of multiple charge transport mechanisms affecting the electrical degradation of the polymer, which is crucially essential for the rational design of high-performance insulation materials.

Gate‐Tunable Potential Barrier on Dual‐Gate Graphene Transistor with Fluorocarbon Thin Film

AbstractThis article reports on the charge transport characteristics across the potential barrier generated by a local dual‐gate modulation at the surface of p‐doped graphene via surface contact on a fluorocarbon (CF) thin film. Owing to simple physical contact, the strong electron affinity of the fluorine atoms in CF stably increases the hole density of graphene, which leads to a massive p‐doping effect in graphene. Then, potential barrier height can be generated and modulated across the channel by forming a local dual‐gate device structure. Different gate biases in dual‐gate operation can split electrical characteristics of a single graphene into highly conductive region and region of sparse charge density, creating large chemical potential difference at the boundary between the two which determines the value of barrier height. Moreover, the device characteristics follow a simple model of the metal–semiconductor junction well in addition to the effect of charge concentration discrepancy in graphene. These results reveal that it is possible to create an ideal and controllable potential barrier composed of a single material using the highly doped graphene with the local dual‐gate structure.

Front Cover: Fluorinated Dihydropentalene‐1,4‐Dione: A Strong Electron‐Accepting Unit with Organic Semiconductor Characteristics (Chem. Eur. J. 17/2023)

A schematic diagram reflects the strong electron affinity of the fluorinated dihydropentalene-1,4-dione (FPD) structure, in which the electron-rich nitrogen-containing amino group in the diketopyrrolopyrrole (DPP) skeleton is replaced by a very strongly electronegative CF2 unit. Moreover, the FPD molecule, which exhibits stronger accepting characteristics, has stronger affinity against electrons than the DPP molecule. More information can be found in the Research Article by S. Yokoyama and Y. Ie (DOI: 10.1002/chem.202203873).

Fluorinated Dihydropentalene-1,4-Dione: A Strong Electron-Accepting Unit with Organic Semiconductor Characteristics.

Invited for the cover of this issue are Soichi Yokoyama and Yutaka Ie at Osaka University, Japan. The image depicts the strong electron affinity of the fluorinated dihydropentalene-1,4-dione (FPD) structure, in which the electron-rich amino groups in the diketopyrrolopyrrole (DPP) skeleton are replaced with a strongly electronegative difluoromethylene unit. Read the full text of the article at 10.1002/chem.202203873.

NH4F modified β zeolite for aniline condensation to diphenylamine and its catalytic mechanism

The main factors affecting the performance of solid acid catalyzed liquid-phase condensation of aniline to diphenylamine are acidity and pore structure. Fluorine has strong electron affinity due to its special electronic structure, which can adjust the acidity and pore structure of zeolite. β zeolite was modified with different concentrations of NH4F solution. The aluminum in the framework of aluminosilicate zeolite was removed to a certain extent, and the acidity and pore size of β zeolite were controlled. Combined with XRD, Py-IR, Al MAS NMR and DRIFTS the active center and reaction mechanism of the catalytic reaction were discussed.

Molecular Simulation of Electron Traps in Epoxy Resin/Graphene Oxide Nanocomposites.

Trapped space charges in epoxy composite distort the electric field, which will induce the failure of the insulation system, and nano graphene oxide may inhibit the curing behavior of epoxy resin matrix. This paper analyzes how the two interfaces affect the electron traps of epoxy resin/graphene oxide systems with different nanofiller contents. The electron affinity energy of epoxy resin matrix and nano filler molecules in the epoxy resin/graphene oxide system is calculated based on quantum chemistry. It is found that nano graphene oxide has a strong electron affinity energy and is easier to capture electrons. Then the influence of the interface formed by the epoxy resin matrix and the nano graphene oxide on the electron transfer ability is calculated. The epoxy resin matrix contains the electron transfer ability of interfaces formed by nano graphene oxide and the molecular chain is different from that of unreacted molecules. The results can provide a reference for the modification of epoxy resin/graphene oxide nanocomposites.

A new type of mixed vegetable insulating oil with better kinematic viscosity and oxidation stability

• The molecular dynamics model of mixed vegetable insulating oil with different proportion was established. • The effects of different mixing ratios on the kinematic viscosity of mixed oil were studied by molecular dynamics. • The difference of oxidation stability between palm fatty acid ester and rapeseed oil was studied by First-Principle. • A mixing ratio with good kinematic viscosity and oxidation stability was obtained. Natural ester is a new type of environment-friendly energy, and the research on its performance is crucial in order to be widely popularized and applied in electrical equipment. The mixing of different natural esters can ameliorate the performance handicap of natural esters. Therefore, two widely applied natural esters, rapeseed oil and palm fatty acid ester (PFAE) were selected in this paper. The kinematic viscosity and oxidation stability of mixed oil were analyzed on the basis of the establishment of the mixture of two oils with different mixing proportion by simulation. Results indicate that the kinematic viscosity of the mixed oil decreased with the addition of PFAE. The kinematic viscosity of the mixed oil decreased by 51.3% when the mixing ratio was 80% rapeseed oil and 20% PFAE. The addition of short chain oil molecules increases the mean square displacement, mean-square radius of gyration and free volume of the mixed oil. The oil molecules in the mixed system have fewer tangles and reduced internal friction between them. DFT calculation shows that numerous electron traps in PFAE provide a channel for the transition of valence electrons. The methyl group in PFAE has strong positive electrostatic potential and strong electron affinity, which makes the oxidation stability of PFAE lower than that of rapeseed oil. Therefore, 80% rapeseed oil and 20% PFAE are the best mixing ratio in this study. This ratio has the best improvement on the kinematic viscosity of the mixed oil and the least influence on the oxidation stability.

Donor‐Node‐Acceptor Type Hole‐Transporting Materials Based on Conjugated Polymers with Perylene Diimide Pendants for High‐Performance Vertical‐Structure Perovskite Photodetectors

AbstractA series of donor‐node‐acceptor (D‐n‐A) type polymers containing linear conjugated backbone as donor and various contents of tetrachloronated perylene diimide (4Cl‐PDI) pendant as acceptor are synthesized for the application as hole‐transporting layers (HTLs) in n‐i‐p structured perovskite photodetectors (PDs). The strong aggregation behaviors of the linear conjugated backbone endow the polymers excellent hole transporting properties, and the strong electron affinity of 4Cl‐PDI pendant enables easily trapping of free electrons. Besides, the 4Cl‐PDI pendants in polymers suppress the intrinsic face‐on orientation of conjugated backbone. Both of the electron‐trapping property of 4Cl‐PDI pendant and the favorable edge‐on orientation of the conjugated backbone are benefits for restraining the dark current in perovskite PDs. Based on such D‐n‐A type hole‐transporting materials, durable vertical‐structure perovskite PDs are successfully demonstrated with superior performance of high responsivity of 0.32 A W−1, high detectivity of 2.2 × 1012 Jones, and fast response speed in microsecond scales.

A comparative DFT+U study of CO oxidation on Pd- and Zr-doped ceria

Metal-doped ceria catalysts have been applied in many important catalytic processes. In this work, we performed density functional theory calculations corrected by on-site Coulomb interactions to study the Pd- and Zr-doped CeO2(111) surfaces with the dopant at different locations. The formation of oxygen vacancies and CO oxidation were systematically calculated on the various doped surfaces. We find that both Pd and Zr doping can activate the surface lattice O and reduce the energy barriers of CO oxidation. However, the promotion effect of the Zr dopant is limited to its existence in the first surface layer, while for the Pd dopant, the surface activity can be greatly enhanced even it occurs far below the surface. Besides, CO2 can be generated directly on the Pd-doped surfaces through reaction between CO and surface O, while the surface intermediate CO2δ– may readily form and restrict the releasing of CO2 by further oxidation to carbonates on the Zr-doped surfaces. Electronic analyses show that the doped Pd exists as Pd4+ and it has stronger electron affinity than other surface species during CO oxidation, contributing to the easy Pd4+ to Pd2+ transformation accompanied by direct CO2 formation at Pd-doped ceria.

Photochemical production of hydrogen peroxide by digging pro-superoxide radical carbon vacancies in porous carbon nitride

Artificial photosynthesis of H 2 O 2 , an environmentally friendly oxidant and a clean fuel, holds great promise. However, improving its efficiency and stability for industrial implementation remains highly challenging. Here, we report the visible-light H 2 O 2 artificial photosynthesis by digging pro-superoxide radical carbon vacancies in three-dimensional hierarchical porous g-C 3 N 4 through a simple hydrolysis-freeze-drying-thermal treatment. A significant electronic structure change is revealed upon the implantation of carbon vacancies, broadening visible-light absorption and facilitating the photogenerated charge separation. The strong electron affinity of the carbon vacancies promotes superoxide radical ( ⋅ O 2 − ) formation, significantly boosting the H 2 O 2 photocatalytic production. The developed photocatalyst shows an H 2 O 2 evolution rate of 6287.5 μM g −1 h −1 under visible-light irradiation with a long cycling stability being the best-performing photocatalyst among all reported g-C 3 N 4 -based systems. Our work provides fundamental insight into highly active and stable photocatalysts with great potential for safe industrial H 2 O 2 production. • Innovative hydrolysis-freeze-drying-thermal treatment (HFDT) method • 3D hierarchical porous carbon nitride (g-C 3 N 4 ) with carbon vacancies • H 2 O 2 evolution rate of 6287.5 μM g −1 h −1 with an outstanding long cycling stability • Modulating electronic structure and promoting H 2 O 2 evolution through carbon vacancies Ding et al. report an innovative hydrolysis-freeze-drying-thermal treatment method for fabricating a 3D hierarchical porous carbon nitride with carbon vacancies. Owing to the synergistic effects between the carbon vacancies and the unique 3D hierarchical porous structure, the highly efficient photocatalytic H 2 O 2 production is achieved.

Charge‐Transfer Cocrystal via a Persistent Radical Cation Acceptor for Efficient Solar‐Thermal Conversion

AbstractDesigning organic charge‐transfer (CT) cocrystals for efficient solar‐thermal conversion is a long‐sought goal but remains challenging. Here we construct a unique CT cocrystal by using a persistent 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radical cation (ABTS+.) as the electron acceptor. The strong persistency and electron affinity of ABTS+.endow a high degree of electron delocalization between ABTS+.and the 3,3′,5,5′‐tetramethylbenzidine donor. Together with the intrinsic long‐wavelength absorption of ABTS+., the synthesized cocrystal can effectively capture the full solar spectrum and show distinguished photothermal efficiency. Such a cocrystal is further used for solar‐driven interfacial evaporation, and a high evaporation rate of 1.407 kg m−2 h−1and a remarkable solar‐to‐vapor efficiency of 97.0 % have been achieved upon 1 sun irradiation. This work indicates the enormous prospects for charge transfer‐based functional materials through rational radical cation engineering.

Charge-Transfer Cocrystal via a Persistent Radical Cation Acceptor for Efficient Solar-Thermal Conversion.

Designing organic charge-transfer (CT) cocrystals for efficient solar-thermal conversion is a long-sought goal but remains challenging. Here we construct a unique CT cocrystal by using a persistent 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS+. ) as the electron acceptor. The strong persistency and electron affinity of ABTS+. endow a high degree of electron delocalization between ABTS+. and the 3,3',5,5'-tetramethylbenzidine donor. Together with the intrinsic long-wavelength absorption of ABTS+. , the synthesized cocrystal can effectively capture the full solar spectrum and show distinguished photothermal efficiency. Such a cocrystal is further used for solar-driven interfacial evaporation, and a high evaporation rate of 1.407 kg m-2 h-1 and a remarkable solar-to-vapor efficiency of 97.0 % have been achieved upon 1 sun irradiation. This work indicates the enormous prospects for charge transfer-based functional materials through rational radical cation engineering.