Visible-Light-Enabled Catalytic Approach to N,O-Spirocycles through Amidyl Radical Addition/Cyclization.

A rational combination of photoredox catalyst anthraquinone and hydrogen atom transfer (HAT) catalyst methyl thioglycolate allows for the rapid and straightforward conversion of a range of 2-amidated acetylenic alcohols to multifunctional N,O-spirocycles under visible light irradiation. With oxygen as the sole terminal oxidant, these reactions can be carried out efficiently at room temperature without the involvement of transition metals or strong oxidants. The successful application of this mild catalytic strategy in the late-stage functionalization of bioactive skeletons further highlights its practical value.

Visible-Light-Enabled Lanthanum-Mediated Intramolecular Epoxy-Ring Opening/Dehydrogenative Lactonization.

Catalytic C(sp3)-H functionalization has afforded great opportunities to prepare organic substances, facilitating the derivatization of complex drugs and natural molecules. This letter describes an efficient and practical protocol for lanthanum-catalyzed continuous epoxy-ring opening and oxidative dehydrogenative lactonization under visible-light irradiation. Notably, the lanthanum catalyst also acts as a photocatalyst while acting as a Lewis acid in this reaction; therefore, no additional photocatalyst is required. We can conveniently prepare a series of diverse isochromanones with oxygen-containing spirocyclic structural units under a balloon-oxygen atmosphere at room temperature. Mechanistic studies and control experiments reveal that the in situ-generated lanthanum bromide should be crucial in the reaction.

Experimental and theoretical study on the photoionization of styrene.

This study employed a vacuum ultraviolet synchrotron radiation source and reflectron time-of-flight mass spectrometry (TOF-MS) to investigate the photoionization and dissociation of styrene. By analyzing the photoionization mass spectrum and efficiency curve alongside G3B3 theoretical calculations, we determined the ionization energy of the molecular ion, appearance energy of fragment ions, and relevant dissociation pathways. The major ion peaks observed in the photoionization mass spectra of styrene correspond to C8 H8 + , C8 H7 + and C6 H6 + . The ionization energy of styrene is measured as 8.46 ± 0.03 eV, whereas the appearance energies of C8 H7 + and C6 H6 + are found to be 12.42 ± 0.03 and 12.22 ± 0.03 eV, respectively, in agreement with theoretical values. The main channel for the photodissociation of styrene molecular ions is the formation of benzene ions, whereas the dissociation channel that loses hydrogen atoms is the secondary channel. Based on the experimental results and empirical formulas, the required dissociation energies (Ed ) of C8 H7 + , C8 H6 + and C6 H6 + are calculated to be (3.96 ± 0.06), (4.00 ± 0.06) and (3.76 ± 0.06) eV, respectively. Combined with related thermochemical parameters, the standard enthalpies of formations of C8 H8 + , C8 H7 + , C8 H6 + and C6 H6 + are determined to be 964.2, 1346.3, 1350.2 and 1327.0 kJ/mol, respectively. Based on the theoretical study, the kinetic factors controlling the styrene dissociation reaction process are determined by using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. This provides a reference for further research on the atmospheric photooxidation reaction mechanism of styrene in atmospheric and interstellar environments.

The effect of nitrous acid (HONO) on ozone formation during pollution episodes in southeastern China: Results from model improvement and mechanism insights.

Two ozone (O3) processes, summer episode dominated by local production and autumn episode dominated by regional transport, were chosen to investigate the role of HONO in different pollution processes. Meteorological conditions, diurnal variation of O3, potential source contribution factor (PSCF) analysis, concentration weighted trajectory (CWT) models, and the distribution of the eight-hour maximum values of O3 on mainland China all prove that summer O3 was mainly locally generated while autumn O3 episode was more susceptible to regional transport. The gaps between observations and simulation results with the default HONO chemistry in Master Chemical Mechanism (MCM) of Observation Based Model (OBM) were higher in summer episode (0.58 ppb) than autumn episode (0.37 ppb). Although we implemented nine additional sources in the model to revise the HONO chemistry, the simulated values were still lower than the observed values. HONO promoted O3 production by accelerating the reaction of HO2 + NO and RO2 + NO, and promoted loss of O3 by the reaction of OH + NO2 and RO2 + NO2. The net production rate of O3 with HONO constraint increased by 28.50 % in summer and 22.43 % in autumn, which also indicated that HONO played more important role in the O3 production in summer. The difference of NOx of daily RIR between the cases with and without HONO constraint was higher in summer O3 episode (0.15 %/%) than that in autumn O3 episode (0.09 %/%), the same as to VOCs with -0.20 %/% in summer O3 episode and - 0.14 %/% in autumn O3 episode, which indicated that the presence or absence of the HONO constraint has a greater impact on the RIR value in the case of dominant local generation. In brief, the O3 sensitivity would be more favorable for VOCs without HONO constrained in the model, which would inevitably mislead policy makers to develop efficient policies to control O3 pollution.

Reconfigurable Artificial Synapse Based on Ambipolar Floating Gate Memory.

Artificial synapse networks capable of massively parallel computing and mimicking biological neural networks can potentially improve the processing efficiency of existing information technologies. Semiconductor devices functioning as excitatory and inhibitory synapses are crucial for developing intelligence systems, such as traffic control systems. However, achieving reconfigurability between two working modes (inhibitory and excitatory) and bilingual synaptic behavior in a single transistor remains challenging. This study successfully mimics a bilingual synaptic response using an artificial synapse based on an ambipolar floating gate memory comprising tungsten selenide (WSe2)/hexagonal boron nitride (h-BN)/ molybdenum telluride (MoTe2). In this WSe2/h-BN/MoTe2 structure, ambipolar semiconductors WSe2 and MoTe2 are inserted as channel and floating gates, respectively, and h-BN serves as the tunneling barrier layer. Using either positive or negative pulse amplitude modulations at the control gate, this device with bipolar channel conduction produced eight distinct resistance states. Based on this, we experimentally projected that we could achieve 490 memory states (210 hole-resistance states + 280 electron-resistance states). Using the bipolar charge transport and multistorage states of WSe2/h-BN/MoTe2 floating gate memory, we mimicked reconfigurable excitatory and inhibitory synaptic plasticity in a single device. Furthermore, the convolution neural network formed by these synaptic devices can recognize handwritten digits with an accuracy of >92%. This study identifies the unique properties of heterostructure devices based on two-dimensional materials as well as predicts their applicability in advanced recognition of neuromorphic computing.

Clinical benefit of COX-2 inhibitors in the adjuvant chemotherapy of advanced non-small cell lung cancer: A systematic review and meta-analysis.

BACKGROUND: Lung cancer is a major cause of death among patients, and non-small cell lung cancer (NSCLC) accounts for more than 80% of all lung cancers in many countries. AIM: To evaluate the clinical benefit (CB) of COX-2 inhibitors in patients with advanced NSCLC using systematic review. METHODS: We searched the six electronic databases up until December 9, 2019 for studies that examined the efficacy and safety of the addition of COX-2 inhibitors to chemotherapy for NSCLC. Overall survival (OS), progression free survival (PFS), 1-year survival rate (SR), overall response rate (ORR), CB, complete response (CR), partial response (PR), stable disease (SD), and toxicities were measured with more than one outcome as their endpoints. Fixed and random effects models were used to calculate risk estimates in a meta-analysis. Potential publication bias was calculated using Egger's linear regression test. Data analysis was performed using R software. RESULTS: The COX-2 inhibitors combined with chemotherapy were not found to be more effective than chemotherapy alone in OS, progression free survival, 1-year SR, CB, CR, and SD. However, there was a difference in overall response rate for patients with advanced NSCLC. In a subgroup analysis, significantly increased ORR results were found for celecoxib, rofecoxib, first-line treatment, and PR. For adverse events, the increase in COX-2 inhibitor was positively correlated with the increase in grade 3 and 4 toxicity of leukopenia, thrombocytopenia, and cardiovascular events. CONCLUSION: COX-2 inhibitor combined with chemotherapy increased the total effective rate of advanced NSCLC with the possible increased risk of blood toxicity and cardiovascular events and had no effect on survival index.

Visible-Light-Enabled Oxidative Coupling of Alkenes with Dialkylformamides To Access Unsaturated Amides.

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.

Visible-light-promoted oxidation/condensation of benzyl alcohols with dialkylacetamides to cinnamides.

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.

Visible-Light-Enabled Oxidative Alkylation of Unactivated Alkenes with Dimethyl Sulfoxide through Concomitant 1,2-Aryl Migration.

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.

Synthesis of oxindoles through trifluoromethylation of N-aryl acrylamides by photoredox catalysis.

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.

Multifunctional high-performance van der Waals heterostructures.

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.

Characterization of particulate products for aging of ethylbenzene secondary organic aerosol in the presence of ammonium sulfate seed aerosol.

Aging of secondary organic aerosol (SOA) particles formed from OH- initiated oxidation of ethylbenzene in the presence of high mass (100-300µg/m(3)) concentrations of (NH4)2SO4 seed aerosol was investigated in a home-made smog chamber in this study. The chemical composition of aged ethylbenzene SOA particles was measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) coupled with a Fuzzy C-Means (FCM) clustering algorithm. Experimental results showed that nitrophenol, ethyl-nitrophenol, 2,4-dinitrophenol, methyl glyoxylic acid, 5-ethyl-6-oxo-2,4-hexadienoic acid, 2-ethyl-2,4-hexadiendioic acid, 2,3-dihydroxy-5-ethyl-6-oxo-4-hexenoic acid, 1H-imidazole, hydrated N-glyoxal substituted 1H-imidazole, hydrated glyoxal dimer substituted imidazole, 1H-imidazole-2-carbaldehyde, N-glyoxal substituted hydrated 1H-imidazole-2-carbaldehyde and high-molecular-weight (HMW) components were the predominant products in the aged particles. Compared to the previous aromatic SOA aging studies, imidazole compounds, which can absorb solar radiation effectively, were newly detected in aged ethylbenzene SOA in the presence of high concentrations of (NH4)2SO4 seed aerosol. These findings provide new information for discussing aromatic SOA aging mechanisms.

Visible-Light-Enabled Decarboxylative Sulfonylation of Cinnamic Acids with Sulfonylhydrazides under Transition-Metal-Free Conditions.

Decarboxylative cross-coupling reactions of cinnamic acids with sulfonylhydrazides were explored using oxygen as the sole terminal oxidant, realizing a conceptually novel technology for vinyl sulfone synthesis under the synergistic interactions of visible light irradiation, organic dye-type photocatalyst eosin Y, KI, and Cs2CO3 at room temperature.

Visible-light-promoted syntheses of ß-keto sulfones from alkynes and sulfonylhydrazides.

A variety of functionalized ß-keto sulfones were smoothly prepared through oxysulfonylation of commercially available alkynes with sulfonylhydrazides under the synergistic interactions of visible light irradiation, Ru(bpy)3Cl2 photocatalyst, oxygen, KI, and NaOAc basic additive under very mild reaction conditions.

Broadband Black-Phosphorus Photodetectors with High Responsivity.

An array of black-phosphorus photodetectors with channel lengths down to 100 nm is fabricated, and temperature-dependent photodetection measurements from 300 K down to 20 K are carried out. The devices show high photoresponse in a broadband spectral range with a record-high photoresponsivity of 4.3 × 10(6) A W(-1) at 300 K for the 100 nm device.

Performance potential and limit of MoS2 transistors.

High-performance MoS2 transistors scaled down to 100 nm are studied at various temperatures down to 20 K, where a highest drive current of 800 µA µm(-1) can be achieved. Extremely low electrical noise of 2.8 × 10(-10) µm(2) Hz(-1) at 10 Hz is also achieved at room temperature. Furthermore, a negative differential resistance behavior is experimentally observed and its origin of self-heating is identified using pulsed-current-voltage measurements.

Size distribution and chemical composition of secondary organic aerosol formed from C1-initiated oxidation of toluene.

Secondary organic aerosol (SOA) formed from C1-initiated oxidation of toluene was investigated in a home-made smog chamber. The size distribution and chemical composition of SOA particles were measured using aerodynamic particle sizer spectrometer and the aerosol laser time-of-flight mass spectrometer (ALTOFMS), respectively. According to a large number of single aerosol diameter and mass spectra, the size distribution and chemical composition of SOA were obtained statistically. Experimental results showed that SOA particles created by C1-initiated oxidation of toluene is predominantly in the form of fine particles, which have diameters less than 2.5 microm (i.e., PM2.5), and glyoxal, benzaldehyde, benzyl alcohol, benzoquinone, benzoic acid, benzyl hydroperoxide and benzyl methyl nitrate are the major products components in the SOA. The possible reaction mechanisms leading to these products are also proposed.

A VUV photoionization mass spectrometric study on the OH-initiated photooxidation of isoprene with synchrotron radiation.

The gas-phase organic compounds resulting from OH-initiated photooxidation of isoprene have been investigated on-line by VUV photoionization mass spectrometry based on synchrotron radiation for the first time. The photoionization efficiency curves of the corresponding gaseous products as well as the chosen standards have been deduced by gating the interested peaks in the photoionization mass spectra while scanning the photon energy simultaneously, which permits the identification of the pivotal gaseous products of the photooxidation of isoprene, such as formaldehyde (10.84 eV), formic acid (11.38 eV), acetone (9.68 eV), glyoxal (9.84 eV), acetic acid (10.75 eV), methacrolein (9.91 eV), and methyl vinyl ketone (9.66 eV). Proposed reaction mechanisms leading to the formation of these key products were discussed, which were completely consistent with the previous works of different groups. The capability of synchrotron radiation photoionization mass spectrometry to directly identify the chemical composition of the gaseous products in a simulation chamber has been demonstrated, and its potential application in related studies of atmospheric oxidation of ambient volatile organic compounds is anticipated.

Experimental study of photooxidation products of ethylbenzene.

Smog chamber experiments were performed to investigate the composition of products formed from photooxidation of aromatic hydrocarbon ethylbenzene. Vacuum ultraviolet photoionization mass spectrometer and aerosol time-of-flight mass spectrometer were used to measure the products in the gas and particle phases in real-time. Experimental results demonstrated that ethylphenol, methylglyoxal, phenol, benzaldehyde, and 2-ethylfurane were the predominant photooxidation products in both the gas and particle phases. However, there were some differences between detected gas phase products and those of particle phase, for example, 2-ethylfurane, ethylglyoxylic acid, nitroethylbenzene, 3,4-dioxopentanal and ethyl-nitrophenol were only existing in the particle-phase. The possible reaction mechanisms leading to these products were also discussed and proposed.

Effect of illumination intensity and light application time on secondary organic aerosol formation from the photooxidation of alpha-pinene.

Secondary organic aerosol (SOA) formation from hydroxyl radical (OH*) initiated photooxidation of alpha-pinene was investigated in a home-made smog chamber. The size distribution of SOA particles was measured using aerodynamic particle sizer spectrometer. The effects of illumination intensity and light application time on SOA formation for alpha-pinene were evaluated. Experimental results show that the concentration of SOA particles increased significantly with an increasing of illumination intensity, and the light application time, the concentration, and the size of SOA particles were also increased. In addition, the factors influencing the formation of SOA were discussed. In addition, this article compared the effect of alpha-pinene with that of toluene, and discussed the contribution of alpha-pinene to SOA formation.