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Here we describe an efficient and practical method for the conversion of 2-aryl benzylic alcohols into the corresponding chromenes with the synergistic interactions of 2-bromoanthraquinone, O2, nBu4NBr and K2CO3 under visible-light irradiation.

Nitrated Polycyclic aromatic hydrocarbons (NPAHs) widely exist in atmospheric aerosol particles are important constituents of brown carbon. Naphthalene and other polycyclic aromatic hydrocarbons (PAHs) are vital precursors of NPAHs. The NPAHs components of secondary organic aerosol (SOA) generated by the photooxidation of naphthalene under different concentrations of NO2 in chamber are on-line measured using synchrotron radiation vacuum ultraviolet photoionization aerosol mass spectrometer (VUV-PIMS) and verified off-line with optical spectrometry in this study. The results demonstrate that NO2 can promote the generation of NPAHs and formation of SOA. Using VUV-PIMS on-line detection, and combined with off-line UV-Vis and infrared spectroscopy verification, it is determined that carboxyls and naphthols are main components of naphthalene SOA particles without NO2, and nitro-naphthalene, dinitro-naphthalene, nitro-naphthol and dinitro-naphthol via the nitration of OH-naphthalene adduct and naphthol products of naphthalene are identified as principal constituents of SOA with NO2. The increase of strong chromophore of N = O of nitro group in NPAHs strengthens the absorbing ability of naphthalene SOA particles. The averaged mass absorption coefficient () over 200–600 nm of naphthalene SOA particles is increases gradually with the increasing concentration of NO2. The of naphthalene SOA particles with 1000 ppb NO2 is 688 cm2/g, which is close to to that of biomass burning organic aerosol particles. These results offer the reference for exploring the formation mechanism and optical properties of NPAHs under the background of high concentration of NOx in urban atmosphere.

NO2 can participate in the photochemical reactions of aromatics, change components, and optics of secondary organic aerosol (SOA). Different from the carbonyls measured in p‐xylene SOA without NO2, nitrophenols, nitrocatechols, and their derivatives via the nitration of phenolic products of p‐xylene are detected as the major components of SOA with NO2. The increase of electrophilic nitro groups in the SOA strengthens absorption ability. Aromatic SOA particles with high concentrations of NOx may contribute to the radiative balance in urban atmosphere.

A practical and efficient method is established for the direct oxidative lactonization of the C(sp3)–H bonds relying on visible-light-induced photoredox catalysis. This protocol expediently allows the delivery of diverse phthalides using oxygen as the sole terminal oxidant under metal-free conditions at room temperature. Notably, the choice of an appropriate hydrogen atom transfer (HAT) cocatalyst is revealed to be critical for the success of this process.

Memristor based neuromorphic computing system has recently attracted enormous attention due to its fast and energy-efficient matrix vector multiplication, thus providing a novel approach to implement neural networks for artificial intelligence. However, the widely studied analogue memristors exhibit major flaws in terms of high conductance variation and nonlinear/asymmetric characteristics. In this work, we develop global gate controlled one transistor one digital memristor (1T1DM) architecture as the basic binary electronic synapse. Inspired by the current research highlights about low-bit networks, we further implement low-bit neuromorphic computing onto our 1T1DM systems by simulation. Compared to the classical analogue type of memristor with one transistor one analogue memristor (1T1R) structure, our 1T1DM network is light-weighted, highly robust and can work well on challenging visual tasks. Besides, benefiting from the global gated device structure, the on-state conductance of the digital memristors in the network can be simultaneously modulated by the controlling gate, offering possibility to tune the power consumption and operation speed while will not increase the circuit complexity.

Semiconductor devices that rely on quantum tunnelling could be of use in logic, memory and radiofrequency applications. Tunnel devices that exhibit negative differential resistance typically follow an operating principle in which the tunnelling current contributes directly to the drive current. Here, we report a tunnelling field-effect transistor made from a black phosphorus/Al2O3/black phosphorus van der Waals heterostructure in which the tunnelling current is in the transverse direction with respect to the drive current. Through an electrostatic effect, this tunnelling current can induce a drastic change in the output current, leading to a tunable negative differential resistance with a peak-to-valley ratio of more than 100 at room temperature. Our device also exhibits abrupt switching, with a body factor (the relative change in gate voltage with respect to that of the surface potential) that is one-tenth of the Boltzmann limit for conventional transistors across a wide temperature range. A black phosphorus/Al2O3/black phosphorus heterostructure can be used to create a tunnel field-effect transistor in which the tunnelling current is in the transverse direction with respect to the drive current, leading to abrupt switching and a negative differential resistance with a peak-to-valley ratio of more than 100 at room temperature.

Visible-light-enabled oxidative radical 1,2-alkylarylation of α-aryl allylic alcohols with carbonyl compounds has been established under mild conditions. An efficient and convenient protocol for the construction of a variety of 1,5-dicarbonyl compounds was realized in the presence of organic fluorophore 4CzIPN, hypervalent iodine(III) reagent, and visible light irradiation. An obvious kinetic isotope effect was noticed, which helped in gaining insight into the mechanistic course.

Secondary organic aerosol (SOA) can influence the radiative balance of the atmosphere via its optical properties. The single-scattering albedo (SSA) and complex refractive index (RI) are the basic optical parameters of the aerosol particles. Toluene SOA particles were formation and aging with extreme amounts of OH radicals without NOx in flow reactor chamber in this study, cavity-enhanced aerosol single-scattering albedometer, UV–Vis spectrometer, and liquid chromatography-mass spectrometry (LC-MS) were utilized to measure the optical properties and components of the aged toluene SOA, respectively. Experimental results demonstrated that the retrieved real part of RI for aged toluene SOA was 1.452 ± 0.002, which is consistent with the reported data. The measured SSA of aged toluene SOA was 0.78 ± 0.02, slightly lower than that of organic aerosols associated with biomass burning (BBOA), and the k-value (imaginary part of RI, corresponding to the absorption extent of SOA particles) was 0.024 ± 0.002, larger than that of fresh toluene SOA, indicating that the absorbing ability of SOA increased with increasing oxidation level. The obtained UV absorption and electrospray ionization mass spectrum shown that carboxylic acids are identified as the principal constituents of aged toluene SOA, which are responsible for the decreased SSA and increased k-value measured by the albedometer when compared to the fresh SOA. As the rate of production of SOA is greater than that of BBOA, the aged SOA particles may contribute remarkably to the radiative balance of the atmosphere. These would provide experimental basis for refine the radiative forcing estimates of anthropogenic SOA for certain regions.

Porous nanododecahedron of Co3O4/C has been synthesized by calcination of the ZIF-67 in air at 400 °C and then be used as electrode material for fabricating a highly sensitive and low overpotential sensor of nitrite ion (NO2−). The structure and morphology characterization show that ZIF-67 behaves as an ideal sacrificial template for preparing Co3O4/C with regular shape. The two components of Co3O4 and carbon are uniformly distributed in the composite. Electrochemical analysis shows that the excellent electrocatalysis performance toward the oxidation of NO2− is based on the synergy of Co3O4 and carbon in the nanocomposite. At NO2− concentration from 2 nM to 8 mM, a fast response time within 3 s is revealed and 1.21 nM of detection limit is achieved. The sensor is also reliable to analysis of NO2− existed in the real samples of soil leaching liquid and macrophage supernate.

Oxidative cross-coupling reactions of benzyl alcohols with N,N-dialkylacetamides were developed only employing oxygen as the terminal oxidant, efficiently providing a new, novel protocol for the construction of multifunctionalized cinnamides with the synergistic effects of KOH, organic photocatalyst eosin Y, and visible light irradiation at room temperature. A broad substrate scope and mild reaction conditions are the prominent features of this transformation.

Metal-free oxidative radical 1,2-alkylarylation of unactivated alkenes with the α-C(sp3)–H bond of dimethyl sulfoxide has been developed. This study realizes a new, conceptually novel technology for convenient construction of a variety of α-aryl-γ-methylsulfinyl ketones in good-to-excellent yields with the synergistic interactions of visible light irradiation, organic fluorophores 4CzIPN, and hypervalent iodine(III) reagent under transition-metal free conditions. A remarkable kinetic isotope effect was observed, which helped provide insight into the reaction’s mechanistic course.

Achieving low contact resistance is one of the main challenges for black phosphorus (BP) transistors for both electronic and optoelectronic applications. Here we demonstrate a novel yet feasible lithium doping technique, which greatly reduces the contact resistance from 2 to 0.85 $\text{k}\Omega \cdot \mu \text{m}$ and results in more than 2.5 times improvement in output current and ON/OFF ratio. This can be mainly attributed to the high hole doping density by lithium bis(trifluoromethylsulfonyl)-imide, which results in a narrower carrier injection barrier at the source end. The ON/OFF ratios of BP field-effect transistors with contact doping at 300 and 20 K are 432 and $7.2 \times 10^{5}$ , respectively. A high drain current of $773~\mu \text{A}/\mu \text{m}$ with a $0.56~\mu \text{m}$ channel length at 20 K is also demonstrated. The doping technique provides a valid way to improve the overall performance of BP transistors.

NH 3 has a significant promotional effect on the formation of organonitrogen compounds in aged aromatic secondary organic aerosol (SOA) in the presence of NO. Ammonium carboxylates formed from NH 3 reactions with organic acids and imidazole compounds via the heterogeneous reactions between NH 3 and dialdehydes of SOA are the major particulate organonitrogen products. Our results suggest that some ambient particles containing organonitrogen compounds may be arising out of this mechanism.

Ammonia (NH3) gas-aging of secondary organic aerosol (SOA) results in the formation of organonitrogen compound is an important class of brown carbon. The particulate products of aged 1,3,5-trimethylbenzene (135-TMB) SOA in the presence of NH3 were measured by UV–Vis spectrophotometer, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and aerosol laser time-of-flight mass spectrometer (ALTOFMS) in present study. Experimental results indicated that NH3 has significant promotion effect on 135-TMB SOA formation. Organic ammonium salts, such as ammonium methyl glyoxylate, ammonium 3,5-dimethylbenzoate, which are formed from NH3 reactions with gaseous organic acids were detected as the principal particulate products of NH3-aged 135-TMB SOA. 4-methyl-imidazole-2-acetaldehyde, 4-methyl- 1H-imidazole and other imidazole products via the heterogeneous reactions between NH3 and dialdehydes of 135-TMB SOA were newly measured. The formation of imidazole products suggests that some ambient particles contained organonitrogen compounds may be come from this mechanism. The results of this study may provide valuable information for discussing SOA aging mechanisms and new route for NH3 deposition.

Mild and direct intramolecular oxidative aryltrifluoromethylations of activated alkenes have been established through visible light photocatalysis, affording a range of CF3-containing oxindoles or isoquinolinediones in the presence of an organic fluorophore-type photocatalyst 4CzIPN, oxygen and visible light irradiation under strong oxidant and transition metal free conditions. A variety of frequently encountered functional groups are well tolerated in this transformation.

As an emerging two-dimensional material, few-layer black phosphorus (BP) shows great potential in nanoelectronics and nanophotonics due to its high carrier velocity. However, non-optimized gate dielectrics often degrade the performance of BP devices severely. In this letter, we demonstrate high-performance BP devices using a novel HfLaO as back gate dielectric with improved interface quality. High current exceeding 1.15 mA/ $\mu \text{m}$ has been achieved at 20 K for BP transistors with improved noise spectral density. Moreover, BP photodetectors with a record high photoresponsivity up to $1.5\times 10^{8}$ A/W and fast response time of $10~\mu \text{s}$ at 300 K are demonstrated. Excellent photoresponse in a broadband spectrum range from 514 to 1800 nm at 70 K has also been achieved.

The OH-initiated reaction of ethylbenzene results in major OH addition, and the formed ethylbenzene-OH adducts subsequently react with O2 and NO2, which determine the components of the oxidation products. In this study, nine possible reaction paths of the most stable ethylbenzene-OH adduct, EB-Ortho (2-ethyl-hydroxycyclohexadienyl radical intermediate), with O2 and NO2 were studied using density functional theory and conventional transition state theory. The calculated results showed that ethyl-phenol formed via hydrogen abstraction was the major product of the EB-Ortho reaction with O2 under atmospheric conditions. Peroxy radicals generated from O2 added to EB-Ortho could subsequently react with NO and O2 to produce 5-ethyl-6-oxo-2,4-hexadienal, furan, and ethyl-glyoxal, respectively. However, nitro-ethylbenzene formed from NO2 addition to EB-Ortho was the predominant product of the EB-Ortho reaction with NO2 at room temperature. The total calculated rate constant of the EB-Ortho reaction with O2 and NO2 was 9.57 × 10−16 and 1.78 × 10−11 cm3 molecule−1 s−1, respectively, approximately equivalent to the experimental rate constants of toluene-OH adduct reactions with O2 and NO2. This study might provide a useful theoretical basis for interpreting the oxygen-containing and nitrogen-containing organics in anthropogenic secondary organic aerosol particles.

Nitrogen-containing organic compounds (NOC) formed from secondary organic aerosols (SOA) age via reaction with reduced nitrogen species are a vital class of brown carbon compounds. NOC compounds from ammonia (NH3) gas-aging of benzene SOA were investigated in present study, and the experiments were performed by irradiating benzene/CH3ONO/NO/NH3 air mixtures in a home-made smog chamber. The particulate NOC products of aged benzene SOA in the presence of NH3 were measured by UV-Vis spectrophotometer, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and aerosol laser time-of-flight mass spectrometer (ALTOFMS) coupled with Fuzzy C-Means (FCM) clustering algorithm, respectively. Experimental results demonstrated that NH3 has significant promotion effect on benzene SOA formation. Organic ammonium salts, such as ammonium glyoxylate, ammonium 6-oxo-2,4-hexadienoiclate, which are formed from NH3 reactions with gaseous organic acids were detected as the major particulate NOC products of NH3-aged benzene SOA. 1H–imidazole, 1H–imidazole-2-carbaldehyde and other imidazole products via the heterogeneous reactions between NH3 and dialdehydes of benzene SOA were successfully detected as important brown carbon constituents. The formation of imidazole products suggests that some ambient particles contained organonitrogen compounds may be come from this mechanism. The results of this study may provide valuable information for discussing NH3 deposition and SOA aging mechanisms.

A range of novel two-dimensional materials have been actively explored for More Moore and More-than-Moore device applications because of their ability to form van der Waals heterostructures with unique electronic properties. However, most of the reported electronic devices exhibit insufficient control of multifunctional operations. Here, we leverage the band-structure alignment properties of narrow-bandgap black phosphorus and large-bandgap molybdenum disulfide to realize vertical heterostructures with an ultrahigh rectifying ratio approaching 106 and on–off ratio up to 107. Furthermore, we design and fabricate tunable multivalue inverters, in which the output logic state and window of the mid-logic can be controlled by specific pairs of channel length and, most importantly, by the electric field, which shifts the band-structure alignment across the heterojunction. Finally, high gains over 150 are achieved in the inverters with optimized device geometries, showing great potential for future logic applications. Black phosphorus/molybdenum disulfide heterostructures serve as a building block for logic devices with overall superior performance characteristics.

Inorganic aerosols such as (NH4)2SO4, NaNO3 and CaCl2 are commonly present in the Chinese urban atmosphere. They could significantly affect the formation and aging of ambient secondary organic aerosols (SOA), but the underlying mechanisms remain unknown. In this work we studied SOA formation from the photooxidation reaction of 1,3,5-trimethylbenzene (135-TMB) with 100 μg/m3 of the above three types of inorganic aerosols as seeds in a laboratory chamber. We focused on the aging products of SOA particles by exposing them to high levels of oxidizing hydroxyl radicals (OH). The particulate products of SOA were measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) and Fuzzy C-Means (FCM) were applied to organic mass spectra for clustering. In the presence of (NH4)2SO4 seeds, 4-methyl-1H-imidazole, 4-methyl-imidazole-2-acetaldehyde and other imidazole derivative compounds formed from reactions of NH4+ with methylglyoxal were detected as new aged products. We also observed aromatic nitrogen-containing organic compounds as the major aged products in the presence of NaNO3 seeds as a consequence of reaction with OH and NO2 radicals, which were generated by UV irradiation of acidic aqueous nitrate, inducing nitration reactions with phenolic compounds. As CaCl2 has the strongest hygroscopic properties of the three salt particles tested, the greater water content on the surface of the aerosol may facilitate the condensing of more gas-phase organic acid products to the hygroscopic CaCl2 seeds, forming H+ ions that catalyze the heterogeneous reaction of aldehydes, products of photooxidation of 135-TMB, and forming high-molecular-weight (HMW) compounds. These results provide new insight into the aromatic SOA aging mechanisms.

Theoretical calculations have been carried out to investigate the possible dissociation channels of isoprene. We focus on the major fragment ions of C5H7+, C5H5+, C4H5+, C3H6+, C3H5+, C3H4+, C3H3+ and C2H3+, which were observed experimentally from the isoprene dissociative photoionization. The energy calculations were performed with the CBS-QB3 model. All the geometries and energies of the fragments, intermediates and transition states involved in the dissociations channels were determined. Finally, the mechanisms of the dissociation pathways were discussed on the comparison of theoretical and experimental results.

A practical and direct method for oxidative cross-coupling of alkenes with dialkylformamides is established employing visible-light-enabled photoredox catalysis. This strategy allows efficient access to diverse unsaturated amides under mild reaction conditions. The application of an appropriate diaryliodonium salt was demonstrated to be critical to the success of this process. This catalyst system is well tolerant of a variety of useful functional groups.

Memristors offer great advantages as a new hardware solution for neuromorphic computing due to their fast and energy-efficient matrix vector multiplication. However, the nonlinear weight updating property of memristors makes it difficult to be trained in a neural network learning process. Several compensation schemes have been proposed to mitigate the updating error caused by nonlinearity; nevertheless, they usually involve complex peripheral circuits design. Herein, stochastic and adaptive learning methods for weight updating are developed, in which the inaccuracy caused by the memristor nonlinearity can be effectively suppressed. In addition, compared with the traditional nonlinear stochastic gradient descent (SGD) updating algorithm or the piecewise linear (PL) method, which are most often used in memristor neural network, the design is more hardware friendly and energy efficient without the consideration of pulse numbers, duration, and directions. Effectiveness of the proposed method is investigated on the training of LeNet-5 convolutional neural network. High accuracy, about 93.88%, on the Modified National Institute of Standards and Technology handwriting digits datasets is achieved (with typical memristor nonlinearity as ±1), which is close to the network with complex PL method (94.7%) and is higher than the original nonlinear SGD method (90.14%). Published version This work was supported by Shenzhen Science and Technology Innovation Committee, JCYJ20200109115210307, KQTD20170810160424889, RCYX20200714114733204, and JCYJ20170818155813437; Guangdong Basic and Applied Basic Research Foundation, 2019A1515111142; Guangdong Provincial Key Laboratory Program (2021B1212040001); and the Open Research Fund of Key Laboratory of Polar Materials and Devices, Ministry of Education.

The gas phase hydration of glyoxal (HCOCHO) in the presence of sulfuric acid (H2SO4) were studied by the high-level quantum chemical calculations with M06-2X and CCSD(T) theoretical methods and the conventional transition state theory (CTST). The mechanism and rate constant of the five different reaction paths are considered corresponding to HCOCHO+H2O, HCOCHO+H2O⋯H2O, HCOCHO⋯H2O+H2O, HCOCHO+H2O⋯H2SO4 and HCOCHO⋯H2O+H2SO4. Results show that H2SO4 has a strong catalytic ability, which can significantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD(T)/6-311++G(3df, 3pd)//M06-2X/6-311++G(3df, 3pd) level of theory. The rate constant of the H2SO4 catalyzed hydrolysis of glyoxal is 1.34×10−11 cm3/(molecule·s), about 1013 higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10−11 cm3/(molecule·s) at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H2SO4 catalyst is feasible and could compete with the reaction glyoxal+OH under certain atmospheric conditions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer.