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Chemical vapor deposition (CVD)-grown graphene films on Cu foils, exhibiting fine scalability and high quality, are still suffering from the adverse impact of surface contamination, i.e., amorphous carbon. Despite the recent successful preparation of superclean graphene through Cu-vapor-assisted reactions, the formation mechanism of amorphous carbon remains unclear, especially with regard to the functions of substrates. Herein, we have found that the crystallographic orientations of underlying metal substrates would determine the cleanness of graphene in such a way that slower diffusion of active carbon species on as-formed graphene-Cu(100) surface is the key factor that suppresses the formation of contamination. The facile synthesis of clean graphene is achieved on the meter-sized Cu(100) that is transformed from the polycrystalline Cu foils. Furthermore, a clean surface of graphene on Cu(100) ensures the reduction of transfer-related polymer residues, and enhanced optical and electrical performance, which allows for versatile applications of graphene in biosensors, functioning as flexible transparent electrodes. This work would offer a promising material platform for the fundamental investigation and create new opportunities for the advanced applications of high-quality graphene films.

The wettability of graphene is critical for numerous applications but is very sensitive to its surface cleanness. Herein, by clarifying the impact of intrinsic contamination, i.e., amorphous carbon, which is formed on the graphene surface during the high-temperature chemical vapor deposition (CVD) process, the hydrophilic nature of clean graphene grown on single-crystal Cu(111) substrate was confirmed by both experimental and theoretical studies, with an average water contact angle of ∼23°. Furthermore, the wettability of as-transferred graphene was proven to be highly dependent on its intrinsic cleanness, because of which the hydrophilic, clean graphene exhibited improved performance when utilized for cell culture and cryoelectron microscopy imaging. This work not only validates the intrinsic hydrophilic nature of graphene but also provides a new insight in developing advanced bioapplications using CVD-grown clean graphene films.

A visible-light-promoted electron-donor-acceptor (EDA) complex-initiated [5 + 1] annulation between biguanides and perfluoroalkyl halides for the construction of perfluoroalkyl- s-triazines has been developed. It was found that both visible light and dioxygen in the air are favorable for the reaction. A radical-polar crossover mechanism was proposed, in which sequential SET, radical combination, HF elimination, electrocyclization, and aromatization are involved.

Ground-level ozone is the primary source of air pollution in China, particularly during the warmer months. In this study, we investigated the exposure status of ozone pollution and the temperature distribution in an air-conditioned bus in Jinan during the evening peak period based on field measurements obtained with a handheld portable particle counter and indigo disulfonate spectrophotometry. Statistical analysis showed that the passengers experienced poor air quality within the confines of the bus due to the poor air quality outside. Furthermore, the level of passenger comfort was dissatisfactory because of the high temperature, thereby highlighting the urgent need to improve the current situation. Numerical simulations were conducted using FLUENT software to explore the impacts of the air supply angle, the opening and closing of the bus door, and the chemical reaction between ozone and its precursors on the diffusion and distribution of ozone, the temperature, and the airflow field. The results indicated that high concentrations of ozone were present in the middle and front regions of the bus. Pollution can be reduced by keeping the bus door open for no longer than 20 s when waiting for other passengers, and the best optimization effect in relation to the temperature and passenger comfort was determined as an air supply angle of 30°. In addition, the average individual daily intake of ozone was combined with other relevant parameters to assess the exposure level. It is recommended that the elderly and children should avoid peak time travel to reduce their exposure to ozone (inhalation dose values > 60 μg/m3 and > 56 μg/m3 according to simulations, respectively). These findings are expected to effectively improve the air quality and passenger comfort levels in busses, thereby protecting the health of passengers and reducing carbon usage.

A photo- and dioxygen-enabled intermolecular radical Csp3–Nsp2 cross-coupling between guanidines and perfluoroalkyl iodides has been developed. N2-Perfluoroalkacylguanidines, which are of biological importance, were obtained under mild conditions via Nsp2-perfluoroalkylation and subsequent hydrolysis. The role of dioxygen in the reaction system was tentatively elucidated; it was supposed to act as an electron shuttle (redox mediator).

An efficient halogenation of electron-deficient (hetero)arenes is described. The reaction utilizes common t-BuONa as a catalyst (for iodination) or a promoter (for bromination and chlorination), and perfluorobutyl iodide, CBr4 or CCl4 as the readily-available halogenating agents, respectively. The protocol features broad scope, high efficiency, mild conditions and gram scalability. An ionic pathway involving halogen bond formation and halophilic attack is proposed. The utility of the resulting iodinated heteroarenes is demonstrated in visible light-mediated Caryl-Caryl cross-coupling reaction.

A photo- and dioxygen-enabled intermolecular radical C

We report a radical cation [4+2] annulation of arylalkenes to afford naphthalene derivatives using an organic photosensitizer (9-mesityl-10-methylacridinium perchlorate) under visible light photocatalysis. In the presence of oxygen (in the air), the oxidative dimerization/intramolecular [4+2] cycloaddition of two alkene molecules provides 3,4-dihydronaphthalen-1(2H)-ones in good to high yields. Under a nitrogen atmosphere, (dihydro)naphthalenes were attained in moderate to excellent yields by using Selectfluor as the oxidant. The transformation proceeds via a tandem dimeric electrophilic addition/Friedel–Crafts cyclization/radical coupling/elimination sequence. This approach represents a mild and straightforward assembly of the naphthalene skeleton using a visible light photocatalytic cascade strategy.

Direct α-amination of nitrones has been developed by using N-haloimide-DBU protocol. Reaction of nitrones with N-haloimide takes place readily in the presence of DBU in DCM, affording directly α-aminonitrones in moderate to excellent yields. N-Haloimide activated by DBU provides both a halogen cation and a nitrogen anion source. E- and Z-isomerization of α-aminonitrones was examined and found to be highly sensitive to acidic substances like silica gel and Bronsted acid. In addition to nitrones, quinoline N-oxides are also suitable substrates. Direct amination achieved by the protocol demonstrates new reactivity of nitrones and quinoline N-oxides.

We have demonstrated that N-haloimides can be utilized as an aminating reagent, in addition to the traditional brominating reagent. Herein, the P–N cross-coupling of P(O)–H compounds and N-bromophthalimide has been developed with the DBU activation strategy. The nitrogen source may arise from internal N-bromophthalimide itself (a self-immolating reagent) or external phthalimide derivatives (with NBS-DBU activation system). The reaction features broad phosphorous compounds scope, including H-phosphinates, H-phosphonates, and H-phosphine oxides, and short reaction time (less than 10 min). This method provides a simple, convenient, efficient, and green route toward phosphoramidates which are of biological importance under mild conditions.

In order to study the characteristics of 3D gas-liquid interfaces, flow pattern transitions, and void fraction in mini tubes, virtual multi-vision experiments and numerical simulations are conducted in a 5.16 mm horizontal tube with air as the dispersed phase and water as the continuous phase. Air and water flow velocities range from 0.024 to 12.330 m/s and from 0.039 to 0.942 m/s, respectively. A simple setup is adopted to capture images synchronously from two orthogonal views with a prism. 3D gas-liquid interfaces of bubbly, slug, and annular flows in horizontal mini tubes are reconstructed in Matlab based on the captured images. Flow pattern transitions and void fractions with 3D interfaces are comprehensively investigated both experimentally and numerically. The numerical results fit well with experimental data in terms of 3D interfaces, cross-sectional and volumetric void fractions. The results show that three flow patterns (bubbly, slug, and annular) are observed experimentally and numerically. The increases in both bubble size and interfacial fluctuation are the main reasons for flow pattern transitions. Two peaks are observed in the Probability Density Functions figures for intermittent flows, while only one peak is obtained for annular flow. The volumetric void fraction fits well with the homogenous model when the gas quality is lower than 0.8, while the slip ratio is around 1. The velocity difference between the two phases increases dramatically at a higher gas quality, leading to a lower void fraction than the predicted value by the homogenous model. The results agree well with empirical correlations with a mean average deviation about 10%, which validates the experimental and numerical methods in the present work.

Multiphase flow in mini/micro channels has been widely studied for its potential in many industrial applications. The normal experimental method cannot capture two separate regions of interest (ROI) with a long distance synchronously for the limited field of views. In order to solve this problem, an improved experimental method is proposed and validated with experimental results. Prism groups are applied to reflect the two regions of interest to a very small shooting zone. Though the actual distance between the two regions is far, the reflected regions adjoin with each other on the top surface of the prisms. Thus, the two regions can be captured synchronously with one image using a small field of view. Two types of configurations with 4 prisms and 6 prisms are compared using gas-liquid and liquid-liquid experimental results. The resolution of the two configurations is similar, while the maximum amplification ratio is smaller for the latter configuration with 6 prisms. The first type is more suitable for experimental studies focusing on the formation and breakup of dispersed phases near two branches. The second configuration is recommended for cases focusing on the formation and fully developed hydraulic characteristics of the dispersed phase. The proposed method is very efficient for studies of hydraulic, heat and mass transfer characteristics of multiphase flows in mini/micro channels.

Perfluoroalkyl-containing aza-tricycles have been prepared in one synthetic operation via an ambient light-promoted three-component reaction of β-oxo esters, perfluoroalkyl iodide and DBU. Intramolecular C–F⋯O and double C–H⋯F weak interactions and intermolecular C–H⋯O and C–H⋯π hydrogen bondings were observed partly due to the incorporation of the perfluoroalkyl group. The perfluoroalkylated non-planar aza-tricycles exhibit interesting room-temperature AIE fluorescence and acid-induced fluorescence enhancement characters.

A simple, one-pot, two-step cascade reaction for the synthesis of α-amino ketones has been developed. Both terminal and internal alkynes react with DMF-activated N-bromosuccinimide (phthalimide) and water (as external O-nucleophile), followed by the introduction of DBU, giving imidated ketones efficiently (the N-sources arise from inherent N-haloimides). Monoamino ketones were the main products with NBS. Mono and/or diamino ketones are produced when NBP is utilized. A mechanism of sequential oxy-1,1-dibromogenation of alkynes, nucleophilic substitution and reductive debromination (or second nucleophilic substitution) is proposed.

When DBU is added, the cross-coupling reaction between alkyl halides (halogen = Cl, Br and I) and N-haloimides (halogen = Cl, Br) occurs, resulting in the formation of aminated products. A halogen bond activated nucleophilic substitution mechanism was proposed. The methodology represents an elegant example of applying the halogen bond activation strategy in an organic transformation.

An ambient-light-promoted and metal-free three-component reaction of active methylene compounds, perfluoroalkyl iodides, and guanidines/amidines is reported. This constitutes a powerful method to prepare perfluoroalkylated pyrimidines with mild reaction conditions, broad substrate scope, excellent functional group tolerance, and simple operation. A radical/polar mechanism involving the formation of a halogen-bond adduct and radical cross-coupling is proposed.

1,4-Diazabicyclo[2.2.2]octane (DABCO)-mediated ring opening of 1-acetylcyclopropanecarboxamides efficiently gave stable zwitterions that could be formed in situ or readily isolated. An application of this novel type of ring opening was demonstrated in a one-pot efficient construction of biologically interesting 3-alkyl γ-lactams. The Lewis-base protocol provides an opportunity for performing ring opening, cycloaddition, and rearrangement reactions of donor–acceptor cyclopropanes through organocatalysis.

A novel and efficient method for the construction of γ-lactams with an all-carbon quaternary center is developed via a DABCO-catalyzed reaction of EWG-activated cyclopropanecarboxamides and electron-deficient alkenes. The process involves sequential ring-opening of activated cyclopropanes, intermolecular Michael addition and intramolecular aza-cyclization.

Directly from terminal alkynes and with N-halosuccinimides (halo = Br and I) or N-cholorophthalimide as the halogen sources, DBU as the activator, 1-haloalkynes were prepared in good to excellent yields at room temperature. Bis(bromoalkyne) and bis(iodoalkyne) were also synthesized in excellent yields with the NBS(NIS)/DBU combination. The reaction features inexpensive and readily available reagents, mild conditions, simple execution, extremely short reaction time, broad halogen scope, high efficiency and is metal-free. Compared to the literature reported methods, our synthetic strategy provided a greener approach towards 1-haloalkynes.

Allylic amination reactions of alkenes, with an NBP (N-bromophthalimide) or NBS (N-bromosuccinimide)/DBU combination, were developed, in which both internal and external nitrogen nucleophiles can be installed directly. Dual activation of NBS or NBP by DBU leads to more electrophilic bromine and more nucleophilic nitrogen atoms simultaneously. This protocol may provide a novel and complementary access to allylic amination under mild conditions.

A DABCO-mediated organocatalyzed anion relay cascade based on 1-cinnamoylcyclopropanecarboxamides has been developed and applied in the construction of 2,3-dihydrofurans with the original alkene and amide functionalities intact. In the aza-oxy-carbanion relay process, DABCO provides both the electron source and sink. The enolate anion-triggered ring opening of the cyclopropane is ascribed to the key step in the anion relay cascade.

An organic photoredox catalytic one-pot protocol is developed for the highly stereoselective synthesis of (Z)-1,4-enediones. The reaction starts directly from alkyne precursors, using 4-(4-cyanophenyl)-2,6-diphenylpyrylium tetrafluoroborate (CN-TPT) as an efficient photosensitizer and dioxygen in the air as a green oxidant. A Csp–Csp oxidative coupling/[4 + 2] cyclization (with dioxygen)/fragmentive isomerization cascade mechanism was proposed. The predominant formation of (Z)-1,4-enediones is attributed to the efficient visible-light illumination from blue LEDs, along with possible energy transfer from the photosensitizer CN-TPT to the E-isomers.

Direct α-amination of nitrones has been developed by using N-haloimide-DBU protocol. Reaction of nitrones with N-haloimide takes place readily in the presence of DBU in DCM, affording directly α-aminonitrones in moderate to excellent yields. N-Haloimide activated by DBU provides both a halogen cation and a nitrogen anion source. E- and Z-isomerization of α-aminonitrones was examined and found to be highly sensitive to acidic substances like silica gel and Bronsted acid. In addition to nitrones, quinoline N-oxides are also suitable substrates. Direct amination achieved by the protocol demonstrates new reactivity of nitrones and quinoline N-oxides.

We have demonstrated that N-haloimides can be utilized as an aminating reagent, in addition to the traditional brominating reagent. Herein, the P–N cross-coupling of P(O)–H compounds and N-bromophthalimide has been developed with the DBU activation strategy. The nitrogen source may arise from internal N-bromophthalimide itself (a self-immolating reagent) or external phthalimide derivatives (with NBS-DBU activation system). The reaction features broad phosphorous compounds scope, including H-phosphinates, H-phosphonates, and H-phosphine oxides, and short reaction time (less than 10 min). This method provides a simple, convenient, efficient, and green route toward phosphoramidates which are of biological importance under mild conditions.

By means of the microstructure observation and measurement of creep properties, an investigation has been made into the high-temperature creep behavior of a single crystal nickel-based superalloy containing Re. Results show that, compared to the 2%-Re alloy, the 4.2%-Re superalloy possesses a better creep resistance in the temperature ranges of 1040–1100 °C. The apparent activation energy and stress exponent of the alloy during steady state creep are measured to be Q = 483.5 kJ/mol and n = 4.7 in the experimental temperature and stress ranges. The dislocation climbing over the rafted γ′ phase dominates the creep process of the alloy during steady state creep. In the later stage of creep, the deformation mechanism of the alloy is that the super-dislocations with [ 0 1 ¯ 1 ] and [0 1 1] trace directions shear into the rafted γ′ phase. The main/secondary slipping dislocations are alternately activated to twist the rafted γ′ phase up to the creep fracture, which is thought to be the fracture mechanism of the alloy during creep.

Highly efficient C-O bond formation has been developed via carboxylic acid catalyzed reaction of 1-acetylcyclopropanecarboxamides with N-halosuccinimide (NXS), which provides strategically novel and atom-economic access to biologically important 5-amino-3(2H)-furanones. The mechanism of halonium-initiated tandem oxa-cyclization and ring opening of cyclopropane was proposed. A variety of nucleophiles were found to open the cyclopropane.

Low-bandgap poly(2,7-carbazole) derivatives with variable N-substituent of ethyl (PEtCzBT), phenyl (PPhCzBT) and 4-diphenylaminophenyl (PTPACzBT) on the carbazoles, were synthesized through Suzuki coupling reaction. The polymers show excellent solubility in organic solvents (readily soluble in chloroform, THF and toluene etc.), good thermal stability (5% weight loss temperature of more than 417 degrees C), and electrochemical properties (reversible redox process with narrow bandgap), and deep HOMO energy levels (similar to 5.1 eV), allowing them promising candidates in the solar cell fabrication. Bulk-heterojunction solar cells with these polymers as electron donor and (6,6)-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) as electron acceptor exhibit high V(oc) (0.91-0.95 V) and good power conversion efficiency (PCE) of 1.69% for PEtCzTB, 2.01% for PPhCzTB, and 2.42% for PTPACzTB. (C) 2011 Elsevier Ltd. All rights reserved.

With a FeSO(4)/TBHP system in water, direct oxidation of sp(3) C-H bonds adjacent to nitrogen of arylureas to give both unprecedented tert-butoxylated and hydroxylated products 2 was revealed. Under elevated temperatures, either 2-oxo-N-arylpyrrolidine-1-carboxamides 3 or 1,3-diarylureas 4 were attained, depending on the aliphatic ring size of the arylurea substrates.

By means of the measurement of creep curves and microstructure observation, an investigation has been made into the microstructure evolution and creep behaviors of 9%W single crystal nickel-base superalloy. Results show that the alloy displays an obvious sensibility on the applied stress when applied stress is more than 160 MPa at 1040 °C. In the ranges of the applied temperatures and stresses, the apparent creep activation energy is measured to be about 465 kJ/mol. In the initial stage of creep, the cubical γ′ phase in the alloy is transformed into the N-type rafted structure along the direction vertical to the applied stress axis, the deformed mechanism of the alloy during steady state creep is dislocations climbing over the rafted γ′ phase, the dislocation shearing into the rafted γ′ phase is thought to be the creep mechanism of the alloy during later stage of creep. After crept up to fracture, the various morphology of the rafted γ′ phase is displayed in the different regions of the sample, the rafted γ′ phase vertical to the stress axis displays in the region far from the fracture, but the coarser twisted γ′ phase is detected in the regions near the fracture, which is attributed to the bigger plastic deformation occurred in the region near the fracture.

By means of the electrolytic extraction, microstructure observation and X-ray diffraction analysis, an investigation has been made into the composing and distribution features of the phases in FGH95 nickel base superalloy. The results show that, after solution treated at 1140 °C and aging, microstructure of the alloy consists of γ′, γ phases and the particles of (Nb,Ti)C, (Nb,W)B2, Nb3B2 and Cr23C6 carbide phases, the mass fraction of γ′ and γ phases in the alloy are measured to be 47.8% and 51.2%, respectively, and the mass fraction of carbide phase is about 1%. The fine γ′ phase is dispersedly distributed within the grains, the coarser γ′ phase is distributed in the wider boundary regions. Thereinto, the mass fraction of γ′ phase about 36–60 nm in size is measured to be 30.6%, the mass fraction of γ′ phase about 60–90 nm in size is measured to be 29.1%. The chemical formula of γ′ phase is identified as (Ni0.896Co0.055Cr0.017Fe0.031)3(Ti0.224Nb0.134Al0.473 Mo0.038 W0.066Cr0.064). The parameters of γ′, γ phases are measured to be αγ′ = 0.35986nm and αγ = 0.35912 nm, respectively, and the misfit of γ′, γ phases in the alloy is measured as 0.2058%.

Ultrafast dynamics of newly synthesized low band gap polymers polyfluorene–thiophene–benzothiadiazole are studied. Additional carbazole groups are added to the side chain to modify its morphological and electronic characters. In solution, ultrafast interband excitation energy transfer is found to be faster in polymer without carbazole side group. In film form, fast quenching happens for exciton–exciton annihilation and charge recombination. The existence of carbazole group dramatically affects the excitation behavior of the film. The polaron-pair recombination was resolved dominant with carbazole group present in side chain.

A domino reaction based on arylaldehydes and 1-acetylcyclopropanecarboxamides has been developed, which allows one-pot and efficient synthesis of structurally complex piperidine-2,4-diones with multiple functionalities under mild conditions. The overall transformation involves tandem aldol/intramolecular aza-Michael/(aldol)/Michael sequences.

New zinc phthalocyanine (ZnPc-TDA), peripherally functionalized with donor-acceptor conjugates was synthesized, and its optical, thermal, electrochemical, and photovoltaic properties were studied. The black ZnPc-TDA exhibited both excellent solubility in common organic solvents, and broad absorption covering the range 300-900 nm. The photovoltaic devices with the configuration of ITO/PEDOT-PSS/ZnPc-TDA:PCBM/LiF/Al produced short circuit current densities of 2.26 mA/cm(2), the open circuit voltage of 0.68 V and power conversion efficiency of 0.4% under AM1.5G illumination. (C) 2010 Elsevier B.V. All rights reserved.

Three novel low-bandgap (LGB) conjugated polythiophenes (PThBTDmCzn) incorporating separate and content-tunable benzothiadiazole and carbazole moieties have been designed and synthesized for application in bulk heterojunction polymer solar cells (PSCs). The absorption spectral, thermal, electrochemical and photovoltaic properties of the random copolymers were investigated. Broad absorption from a single polymer covering the visible region from 300 to 800 nm was observed, which was ideal for highly efficient harvesting of the solar spectrum. DSC analysis showed that the polymers readily crystallized, indicating highly ordered intermolecular packing, which is beneficial for efficient charge-carrier transport. Electrochemical studies indicate desirable HOMO/LUMO levels that enable a high open-circuit voltage while blending them with fullerene derivatives as electron acceptors. Polymer solar cells using 1:1 or 1:2 wt/wt polymer: PC61BM (methanofullerene [6,6-phenyl C61-butyric acid methyl ester] blends as the photoactive layers were fabricated and characterized. The preliminary investigation on the photovoltaic device of the PThBTDmCzn polymers gave similar power conversion efficiency of 1.1–1.2% with Voc of 0.64–0.68 V under simulated solar light AM 1.5 G (100 mW/cm2).

p-Terphenyls and heteroaryl analogues including bipyridines were prepared via [5C + 1C(N)] annulation of alpha-aryl-alpha-alkenoyl ketene-(S,S)-acetals (five carbon 1,5-bielectrophilic species) with nitroethane or ammonium acetate. The reaction features mild conditions, multisubstitution, and functional group tolerance and is metal catalyst free. The present protocol provides a new alternative to the conventional methodologies for the synthesis of teraryls.

A novel carbon tetrabromide promoted one-pot reaction of amines and carbon disulfide under mild conditions has been developed, which provides a straightforward and efficient access to thioureas and thiuram disufides, depending on the nature of the amines employed. The promotion effect is explained as the transient formation of a sulfenyl bromide intermediate from dithiocarbamate and carbon tetrabromide during the reaction.