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Despite the great progress in research on molecular carbons containing multiple helicenes around one core, realizing the stereoselectivity of carbons containing multiple helicenes around more cores is still a great challenge. Herein, molecular carbon C204 featuring 12‐fold [5]helicenes around four cores was successfully constructed by using nine perylene diimide (PDI) units, and exhibits good solubility and stability. Despite 256 possible stereoisomers caused by the 12‐fold [5]helicenes, we only obtained one pair of enantiomers with D3 symmetry. There are four possible pairs of enantiomers with D3 symmetry, namely 7A, 7B, 7C and 7D. Theoretical and experimental results verify that the obtained structure belongs to 7C, which has the lowest energy. The enantiomers can also be separated by chiral HPLC. These results suggest that choosing PDIs as building blocks can not only improve the solubility and stability but also realize the stereoselectivity and chirality of molecular carbons. [ABSTRACT FROM AUTHOR]

Recently, a novel two-dimensional (2D) BC3N2 monolayer has gained a lot of attention due to its graphene-like structure, and it was first reported by using the particle swarm optimization algorithm and ab initio calculations. Combining density functional theory with the non-equilibrium Green's function method, a 2D BC3N2-based nanodevice has been theoretically constructed and the gas sensing performance of the BC3N2 monolayer for inorganic and organic molecules has been extensively investigated. The results revealed that the BC3N2 monolayer remains metallic with thermodynamic stability. Meanwhile, the results of sensing performance analysis show that the inorganic molecules CO, NO, and NO2 and organic molecules C2H2 and HCHO have strong chemical interactions with BC3N2 and were chemically adsorbed onto BC3N2. In contrast, the interactions between NH3, SO2, CH4, C2H4 and CH3OH and BC3N2 are very weak and these molecules adopt physical adsorption. In the case of chemisorption, the electronic transport behaviors of the 2D BC3N2 devices are sensitive to molecules, and the gas sensitivity of BC3N2 is strongly anisotropic, especially for organic C2H2 with the gas sensing ratios from 7.30 to 10.43 (from 2.51 to 2.79) under different bias voltages along the zigzag (armchair) direction. For inorganic molecules, the gas sensing device is not particularly sensitive, and the maximum gas sensing ratio is only 1.36 for CO. Meanwhile, the large anisotropic gas sensitivity can reach up to 2.66/6.22 for electron transport along the armchair and zigzag directions for CO/C2H2 in the BC3N2-based sensing devices. Accordingly, the high gas sensitivity can be disclosed by displaying the scattering state around the Fermi level at different bias voltages during the transport process. As a result, BC3N2 could be used in 2D gas sensing devices, especially for sensing organic molecule C2H2. [ABSTRACT FROM AUTHOR]

The reform of power spot market in China provides a new profit mode, determining energy trading strategy based on the power spot prices for distributed energy storages. However, individually accessing every distributed energy storage to the dispatch centre results in a high cost and low efficiency, which needs to be improved by connecting through the aggregator. To this end, this paper proposes a regulation mode and strategy for distributed energy storages participating in energy trading through aggregation. First, the optimal centres of distributed energy storages are searched as the aggregation centres according to the electrical distance distributed by the energy storage, and the model of each distributed energy storage aggregation group is established. On this basis, the conditional value at risk (CVaR) method is introduced to quantify the income risk brought by the fluctuation of power spot prices, following with the optimization model for day‐ahead stage and real‐time stage. Finally, case studies under multiple scenarios of power spot market verify that the regulation mode and strategy can effectively guarantee the economic profits of distributed energy storages by setting aggregation groups and reasonable risk preference coefficients. [ABSTRACT FROM AUTHOR]

Organic phosphorescence, originating from triplet excitons, has potential for the development of new generation of organic optoelectronic materials. Herein, two heavy‐atom‐free room‐temperature phosphorescent (RTP) electron acceptors with inherent long lifetime triplet exctions are first reported. These two 3D‐fully conjugated rigid perylene imide (PDI) multimers, as the best nonfullerene wide‐bandgap electron acceptors, exhibit a significantly elevated T1 of ≈2.1 eV with a room‐temperature phosphorescent emission (τ = 66 µs) and a minimized singlet–triplet splitting as low as ≈0.13 eV. The huge spatial congestion between adjacent PDI skeleton endows them with significantly modified electronic characteristics of S1 and T1. This feature, plus with the fully‐conjugated rigid molecular configuration, balances the intersystem crossing rate and fluorescence/phosphorescence rates, and therefore, elevating ET1 to ≈2.1 from 1.2 eV for PDI monomer. Meanwhile, the highly delocalized feature enables the triplet charge‐transfer excitons at donor–acceptor interface effectively dissociate into free charges, endowing the RTP electron acceptor based organic solar cells (OSCs) with a high internal quantum efficiency of 84% and excellent charge collection capability of 94%. This study introduces an alternative strategy for designing PDI derivatives with high‐triplet state‐energy and provides revelatory insights into the fundamental electronic characteristics, photophysical mechanism, and photo‐to‐current generation pathway. [ABSTRACT FROM AUTHOR]

Summary: With the rapid development of China's social economy, the transportation needs of its residents continue to increase and encourage rapid and continual development of the Chinese high‐speed railway system. The design of China's high‐speed railway station is the integration of a new model that includes the layout of upcoming booking, traffic, waiting, tickets, and other functions to be set in the area known as the waiting hall. As such, the waiting hall has become an extremely important element of the environmental monitoring system. This paper proposes the design of a high‐speed rail station environmental monitoring system based on the LoRa communication technology. This system aims to enable the real‐time monitoring of temperature, humidity, illuminance, and noise decibels in high‐speed railway stations. The wireless communication present in the proposed system adopts the LoRa technology features of low power consumption, low cost, and long‐range communication. In this study, we set up a prototype of a LoRa enabled network in the lab building of Hohai University to transmit the environmental data. Moreover, we analyzed the signal propagation of LoRa in an indoor environment. [ABSTRACT FROM AUTHOR]

1D nonplanar graphene nanoribbons generally have three possible conformers: helical, zigzag, and mixed conformations. Now, a kind of 1D nonplanar graphene nanoribbon, namely dodecatwistarene imides featuring twelve linearly fused benzene rings, was obtained by bottom‐up synthesis of palladium‐catalyzed Stille coupling and C−H activation. Single‐crystal X‐ray diffraction analyses revealed that it displays a zigzag‐twisted conformation caused by steric hindrance between imide groups and neighboring annulated benzene rings with the pendulum angle of 53°. This conformation is very stable and could not convert into other conformations even when heated up to 250 °C for 6 h. Despite of the highly twisted topology, organic field‐effect transistor based on it exhibits electron mobility up to 1.5 cm2 V−1 s−1 after annealing. [ABSTRACT FROM AUTHOR]

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A novel kind of nanographene imide, namely pentaperylene decaimides (PPD) featuring dual‐core sixfold [5]helicenes and ten imide groups, was efficiently obtained. Among the possible 28 stereoisomers, which include 14 pairs of enantiomers, only one pair of enantiomers was obtained selectively which could be separated by chiral HPLC. Single‐crystal X‐ray diffraction analyses revealed that it exhibits a D2‐symmetric "four‐bladed propeller" conformation composed of conjoined double "three‐bladed propeller", which is very stable and could not convert into other conformations even when heated up to 200 °C. Meanwhile, enantiomerically pure PPD also exhibits an excellent resistance to thermally induced racemization, which makes it a promising candidate for various applications in chiral material science. [ABSTRACT FROM AUTHOR]

A molecule is shown in the middle, surrounded by the building blocks of perylene diimides and benzenes. Chirality, Helicene, Molecular Carbon, Stereoisomers, Stereoselectivity Keywords: Chirality; Helicene; Molecular Carbon; Stereoisomers; Stereoselectivity EN Chirality Helicene Molecular Carbon Stereoisomers Stereoselectivity 1 1 1 01/02/23 20230102 NES 230102 B Molecular carbon imides b featuring 12-fold [5]helicenes around four cores are reported by Guogang Liu, Yan Li, Zhaohui Wang et al. in their Research Article (e20224769). [Extracted from the article]

Molecular carbon imides featuring 12‐fold [5]helicenes around four cores are reported by Guogang Liu, Yan Li, Zhaohui Wang et al. in their Research Article (e20224769). A molecule is shown in the middle, surrounded by the building blocks of perylene diimides and benzenes. [ABSTRACT FROM AUTHOR]

The surfaces of semiconductor nanocrystals have been known to be a very important factor in determining their optical properties. The introduction of functionalized ligands can further enhance the interactions between nanocrystals, which is beneficial for the assembly of nanocrystals. In a previous report, we developed a ligand-assisted reprecipitation method to fabricate organometal halide perovskite nanocrystals capped with octylamine and oleic acid. Here, a TPE derivative 3-(4-(1,2,2-triphenylvinyl)phenoxy)propan-1-amine, which shows a typical aggregation induced emission feature, is applied to replace octylamine to fabricate CH3NH3PbBr3 nanocrystals. The obtained CH3NH3PbBr3 nanocrystals were nanocubes (average diameter ∼ 11.1 nm) and are likely to assemble into ordered superstructures. By adjusting the chain length of the TPE derivative, we found that the assembly of the CH3NH3PbBr3 nanocrystals was correlated with the interactions between the TPE groups. This provides a new platform to investigate the ligand effects in nanocrystal solids and may potentially achieve enhanced optical and electrical properties. [ABSTRACT FROM AUTHOR]

The assembly of van der Waals (vdW) heterostructure with easily regulated electronic properties provides a new way for the expansion of two-dimensional materials and promotes the development of optoelectronics, sensors, switching devices and other fields. In this work, a systematic investigation of the electronic properties of MoGe 2 N 4 /SiC heterostructures using density functional theory has been conducted, along with the modulation of electronic properties by vertical strain and the potential application prospects in optoelectronic devices. The results show that MoGe 2 N 4 /SiC heterostructure has excellent dynamic and thermal stability and belongs to type-II band alignment semiconductors. This is extremely beneficial for the separation of photo-generating electron-hole pairs, so it has important significance for the development of photovoltaic materials. In addition, under the control of vertical strain, the semiconductor-metal transition occurs in the MoGe 2 N 4 /SiC heterostructure when the compressive strain reaches 6%. In the case of compressive strain less than 6% and tensile strain, the MoGe 2 N 4 /SiC heterostructure maintains the type-II band alignment semiconductor characteristics. Meanwhile, we find that the MoGe 2 N 4 /SiC heterostructure has optical absorption coefficients of up to 10 5 in the visible and ultraviolet light ranges, which can improve the absorption coefficients of the MoGe 2 N 4 and SiC monolayer in some visible light regions. Finally, the optical conductivity of the MoGe 2 N 4 /SiC heterostructure exhibits significant anisotropy, with the armchair direction displaying higher conductivity within the orange light range. In conclusion, the formation of vdW heterostructure by vertically stacking MoGe 2 N 4 and SiC monolayers can effectively improve their electronic and optical properties, which provides a valuable reference for the future development of electronic devices and photovoltaic materials., (© 2024 IOP Publishing Ltd.)

Two-dimensional atomic layer materials, as an important part of the post-Moore era, have recently become an ideal choice for the preparation of high-efficiency, low-power, and miniaturized gas sensors. In this work, our study utilized density functional theory and the nonequilibrium Green's function method to investigate the electronic properties of the pentagonal BN 2 (P-BN 2 ) monolayer, as well as its gas-sensing properties for organic and inorganic gases. We also investigated how defects affect the quantum transport properties of the P-BN 2 -based device. Our findings demonstrate that the CO, H 2 S, NH 3 , SO 2 , C 2 H 5 OH, C 3 H 6 OH, CH 3 OH, and CH 4 undergo physisorption on the P-BN 2 monolayer, while NO, NO 2 , C 2 H 2 , C 2 H 4 , and HCHO undergo chemisorption. Then, we analyzed the impact of gas molecules chemisorbed on the P-BN 2 monolayer on the electronic transport properties of the P-BN 2 -based gas sensor. When these five gas molecules are adsorbed, the current of the P-BN 2 -based gas sensor is greatly reduced. In addition, the effect of defects on the quantum transport properties of the P-BN 2 -based device is investigated. The results indicate that defects of N, B, and BN atoms lead to a decrease in the current of P-BN 2 -based nanodevices. Moreover, both the adsorption of gas molecules and the formation of vacancy defects leading to a decrease in device current can be revealed by the local device density of states near the zero-bias Fermi level, elucidating their microscopic mechanisms. Finally, gas molecules can also cause a decrease in the current of defect systems. These theoretical studies are of great significance for exploring two-dimensional atomic layer materials as high-efficiency gas sensors.

Nonvolatile electrical control is the core of future magnetoelectric nanodevices. In this work, we systematically explore both the electronic structures and transport properties of multiferroic van der Waals (vdW) heterostructures consisting of a ferromagnetic FeI 2 monolayer and a ferroelectric In 2 S 3 monolayer using density functional theory and the nonequilibrium Green's function method. The results reveal that the FeI 2 monolayer can be reversibly switched between semiconducting and half-metallic properties by nonvolatile control of the In 2 S 3 ferroelectric polarization states. Correspondingly, the proof-of-concept two-probe nanodevice based on the FeI 2 /In 2 S 3 vdW heterostructure exhibits a significant valving effect by modulating the ferroelectric switching. Moreover, it is also found that the preference of nitrogen-containing gases such as NH 3 , NO, and NO 2 for adsorption on the surface of FeI 2 /In 2 S 3 vdW heterostructures strongly depends on the polarization direction of the ferroelectric layer. In particular, the FeI 2 /In 2 S 3 heterostructure shows reversible capture behavior for NH 3 . As a result, the FeI 2 /In 2 S 3 vdW heterostructure-based gas sensor demonstrates high selectivity and sensitivity. These findings may open up a new route for the application of multiferroic heterostructures to spintronics, nonvolatile memories, and gas sensors.

Two-dimensional (2D) magnetic materials are the key to the development of the new generation in spintronics technology and engineering multifunctional devices. Herein, the electronic, spin-resolved transmission, and gas sensing properties of the 2D g-C 4 N 3 /MoS 2 van der Waals (vdW) heterostructure have been investigated by using density functional theory with non-equilibrium Green's function method. First, the g-C 4 N 3 /MoS 2 vdW heterostructure demonstrates ferromagnetic half-metallicity and superior adsorption capacity for gas molecules. The spin-dependent electronic transport of the g-C 4 N 3 /MoS 2 -based nanodevice is obviously regulated by parallel or anti-parallel spin configuration in electrodes, leading to perfect single-spin conduction behavior with a nearly 100% spin filtering efficiency, a negative differential resistance effect, and other interesting electrical transport phenomena. Moreover, g-C 4 N 3 /MoS 2 exhibits directional dependency and strong transport anisotropic behavior under bias windows, indicating that the electric current propagates more easily through the vertical direction than the horizontal direction. The physical mechanisms are revealed and analyzed by presenting the bias-dependent transmission spectra in combination with the projected local device density of states. Finally, the g-C 4 N 3 /MoS 2 -based gas sensor is more sensitive to CO, NO, NO 2 , and NH 3 molecules with the chemisorption type. The strong chemical adsorption leads to the formation of electrons on the local scattering center and ultimately affects the transport properties, resulting in the maximum gas sensitivity reaching 6.45 for NO at the bias of 0.8 V. This work not only reveals that the g-C 4 N 3 /MoS 2 vdW heterostructure with high anisotropy, perfect spin filtering, and outstanding gas sensitivity is a promising 2D material but also provides an insight into the further application in futuristic electronic nanodevices.

Recently, a novel two-dimensional (2D) BC 3 N 2 monolayer has gained a lot of attention due to its graphene-like structure, and it was first reported by using the particle swarm optimization algorithm and ab initio calculations. Combining density functional theory with the non-equilibrium Green's function method, a 2D BC 3 N 2 -based nanodevice has been theoretically constructed and the gas sensing performance of the BC 3 N 2 monolayer for inorganic and organic molecules has been extensively investigated. The results revealed that the BC 3 N 2 monolayer remains metallic with thermodynamic stability. Meanwhile, the results of sensing performance analysis show that the inorganic molecules CO, NO, and NO 2 and organic molecules C 2 H 2 and HCHO have strong chemical interactions with BC 3 N 2 and were chemically adsorbed onto BC 3 N 2 . In contrast, the interactions between NH 3 , SO 2 , CH 4 , C 2 H 4 and CH 3 OH and BC 3 N 2 are very weak and these molecules adopt physical adsorption. In the case of chemisorption, the electronic transport behaviors of the 2D BC 3 N 2 devices are sensitive to molecules, and the gas sensitivity of BC 3 N 2 is strongly anisotropic, especially for organic C 2 H 2 with the gas sensing ratios from 7.30 to 10.43 (from 2.51 to 2.79) under different bias voltages along the zigzag (armchair) direction. For inorganic molecules, the gas sensing device is not particularly sensitive, and the maximum gas sensing ratio is only 1.36 for CO. Meanwhile, the large anisotropic gas sensitivity can reach up to 2.66/6.22 for electron transport along the armchair and zigzag directions for CO/C 2 H 2 in the BC 3 N 2 -based sensing devices. Accordingly, the high gas sensitivity can be disclosed by displaying the scattering state around the Fermi level at different bias voltages during the transport process. As a result, BC 3 N 2 could be used in 2D gas sensing devices, especially for sensing organic molecule C 2 H 2 .

Recently, Dirac material BeN 4 has been synthesized by using laser-heated diamond anvil-groove technology (Bykov et al 2021 Phys. Rev. Lett. 126 175501). BeN 4 layer, i.e. beryllonitrene, represents a qualitatively class of two-dimensional (2D) materials that can be built of a metal atom and polymeric nitrogen chains, and hosts anisotropic Dirac fermions. Enlighten by this discovered material, we study the electronic structure, anisotropic transport properties and gas sensitivity of 2D BeN 4 using the density functional theory combined with non-equilibrium Green's function method. The results manifest that the 2D BeN 4 shows a typical semi-metallic property. The electronic transport properties of the intrinsic BeN 4 devices show a strong anisotropic behavior since electrons transmitting along the armchair direction is much easier than that along the zigzag direction. It directly results in an obvious switching characteristic with the switching ratio up to 10 5 . Then the adsorption characteristics indicate that H 2 S, CO, CO 2 and H 2 molecules are physisorption, while the NH 3 , NO, NO 2 , SO 2 molecules are chemisorption. Among these chemisorption cases, the 2D gas sensor devices show an extremely high response for SO 2 recognition, and the high anisotropy of the original 2D BeN 4 device still maintains after adsorbing gas molecules. Finally, high switching ratio and inorganic gas sensing performance of BeN 4 monolayer could be clearly understood with local density of states, bias-dependent spectra, scattered state distribution. In general, the results indicate that the designed BeN 4 devices have potential practical application in high-ratio switching devices and high gas-sensing molecular devices., (© 2022 IOP Publishing Ltd.)

The surfaces of semiconductor nanocrystals have been known to be a very important factor in determining their optical properties. The introduction of functionalized ligands can further enhance the interactions between nanocrystals, which is beneficial for the assembly of nanocrystals. In a previous report, we developed a ligand-assisted reprecipitation method to fabricate organometal halide perovskite nanocrystals capped with octylamine and oleic acid. Here, a TPE derivative 3-(4-(1,2,2-triphenylvinyl)phenoxy)propan-1-amine, which shows a typical aggregation induced emission feature, is applied to replace octylamine to fabricate CH 3 NH 3 PbBr 3 nanocrystals. The obtained CH 3 NH 3 PbBr 3 nanocrystals were nanocubes (average diameter ∼ 11.1 nm) and are likely to assemble into ordered superstructures. By adjusting the chain length of the TPE derivative, we found that the assembly of the CH 3 NH 3 PbBr 3 nanocrystals was correlated with the interactions between the TPE groups. This provides a new platform to investigate the ligand effects in nanocrystal solids and may potentially achieve enhanced optical and electrical properties.