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Two push–pull metal-free sensitizers with 5,11-dihydroindolo[3,2-b]carbazole derivatives as electron-donating groups and 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid (BTZ) as electron-withdrawing unit, denoted by SK201 and SK202, were synthesized and used for fabrication of dye-sensitized solar cells (DSSCs). SK202 contains a thienyl group between the donor and acceptor, whereas in SK201 the donor and acceptor are connected directly by a single bond. Introduction of a thienyl group improved the planarity of the dye molecule, broadened the absorption spectrum, enhanced the molar extinction coefficient, increased the dye loading on TiO2, and accelerated interface electron transfer on TiO2. This fine tuning of dye structure improved the performances of DSSCs based on SK202 sensitizers and gave a power conversion efficiency (PCE) of 11.0% (Jsc 16.5 mA cm−2, Voc 932 mV, and fill factor 71.7%), compared with that of 7.2% for SK201, under standard AM1.5G solar irradiation (100 mW cm−2) with a Co(II/III) complex based redox couple.

Two dyes with dithieno[3,2-b:20,30-d] pyrrole (DTP) as the donor (An101 and An102) have been synthesized and characterized. An101 and An102 were applied to dye-sensitized solar cells (DSSCs) and power conversion efficiencies (PCEs) of 8.0% and 9.5% were achieved with the I2−/I3− redox couple, which correspond to open voltages (Voc) of 784 and 690 mV, current densities (Jsc) of 15.1 and 20.0 mA cm−2, the fill factors of 67.2% and 68.7%, respectively, under AM1.5G irradiation. It is worth noting that the different connection locations of the donors with the π-bridge result in different PCEs. An102 has a higher Jsc owing to its high molar extinction coefficient and small torsion angle, which increase the light-harvesting ability and coplanarity. An101 has a higher Voc owing to introduction of the alkoxybenzene group, which can effectively suppress recombination with the electrolyte and dye. By scanning with different bias voltages with electrochemical impedance spectroscopy, the reason for the high voltage of the An101 dye is up-shift of the TiO2 conduction-band edge and elongated electron lifetimes. However, the main reason for the relatively high PCE of the An102 dye is the coplanarity, which results in good long-term stability.

Building upon the success of TRMM launched in 1997, NASA and JAXA successfully deployed the Global Precipitation Measurement (GPM) mission on February 28, 2014. GPM started to release the new-generation global precipitation products Integrated Multi-satellite Retrievals for GPM (IMERG) since April 2014. Critical data validation over diverse topographic and climatic regions could effectively help users and algorithm developers maximize the accuracy, strengths and weaknesses of the new product. To this end, this study comprehensively evaluated and compared this newly released precipitation product (IMERG V05B) and its predecessor TRMM 3B42V7 based upon the ground-based observations under complex topographic and climatic conditions over the Hexi Region in the northwest arid region of China. The evaluation was conducted at daily, monthly, seasonal and annual scales from April 2014 to September 2017. Results indicated that: (1) compared to ground-based observations, both IMERG and 3B42V7 showed good performance with slightly overestimation (with RB values of 4.58% and 2.27%, respectively) at basin scale. While at the point-to-pixel scale, both products showed overestimation in low-elevation regions and underestimation in high-altitude mountainous areas; (2) on multiple temporal and spatial scales, IMERG correlated better with ground-based observations than 3B42V7, whereas its bias were larger than 3B42V7; (3) both IMERG and 3B42V7 showed better performance in warm seasons (summer and autumn) than in cold seasons (spring and winter); (4) Compared to 3B42V7, IMERG represented both larger hit rate (POD) and false alarm ratio (FAR), but similar correct detection rate (CSI); (5) IMERG showed poorer detection capabilities in light precipitation events (0–2 mm/day), while represented a certain advantage in detecting moderate (5–10 mm/day) and heavy (>25 mm/day) rain events. Most of precipitation estimates over Hexi region are unreliable on daily and monthly time scales. Results suggest that IMERG do not show significant improvement compared to its predecessor 3B42V7, and performed even worse in estimating precipitation amounts. Further data bias-correction is needed before IMERG can be used for climatic and hydrologic research in the Hexi region.

X1 (MeO-TPD) is an inexpensive and easily synthesized pi-conjugated molecule that has been used as a hole-transport material (HTM) in solid-state dye-sensitized solar cells (ssDSSCs), achieving rel ...

Colloidal quantum dot (CQD) solar cells with a ZnO/PbS-TBAI/PbS-EDT/carbon structure were prepared using a solution processing technique. A commercially available carbon paste that was processed at low-temperatures was used as a counter electrode in place of expensive noble metals, such as Au or Ag, which are used in traditional PbS CQD solar cells. These CQD solar cells exhibited remarkable photovoltaic performance with a short circuit density (Jsc) of 25.6 mA/cm2, an open circuit voltage (Voc) of 0.45 V, a fill factor (FF) of 51.8% and a power conversion efficiency (PCE) as high as 5.9%. A reference device with an Au counter electrode had a PCE of 6.0%. The PCE of the carbon-containing CQD solar cell remained stable for 180 days when tested in ambient atmosphere, while the PCE of the Au-containing CQD solar cell lost 48.3% of its original value. Electrochemical impedance spectroscopy (EIS) demonstrated that holes within the PbS CQD were effectively transported to the carbon counter electrode.

Fluorescent nitrogen-doped carbon dots (N-CDs) are synthesized by a facile one-pot solvothermal approach from Taixi anthracite in the presence of dimethyl formamide (DMF). Benefiting from superior dispersion of light components in DMF and easy exfoliation of smaller sp2-carbon structures from the anthracite, the as-prepared N-CDs show a strong photoluminescence (PL) with a high quantum yield (QY) of 47.0% and production yield of 25.6 wt%. Besides, the N-CDs also exhibit a singlet oxygen (1O2) generation behavior with a 1O2 generation QY of 19.0%. Moreover, the as-obtained N-CDs emit blue PL under the excitation wavelength of 365 nm, and can be easily dispersed in polymethyl methacrylate (PMMA), retaining the inherent advantages of the N-CDs and the PMMA matrix. The possible mechanism involved in the formation of N-CDs is proposed and discussed in terms of the macromolecular structure of the anthracite and the solvothermal approach adopted in the study.

Two novel dyes that are similar in chemical structure, except for different donor units, AJ301and AJ303 were synthesized, characterized and applied as sensitizers in dye-sensitized solar cells (DSSCs). Both dyes exhibited a wide absorption of visible sunlight. The introduction of fused rings on the donor unit of AJ303 presented an appropriate energy level, less recombination and longer electron lifetime to achieve a power conversion efficiency (PCE) of 10.2%, far above that achieved for AJ301 of 6.2% with a [Co(bpy)3]2+/3+-based electrolyte under standard AM1.5G solar irradiation (100 mW cm−2). The DSSCs based on AJ303 and AJ301 with [Cu(tmby)2]2+/+-based electrolyte showed a lower PCE of 8.2% and 5.4%, respectively. Therefore, the results indicated that the introduction of a fused-ring in the donor group is a meaningful synthetic strategy to improve the photovoltaic performance.

Petroleum asphalt based ultrathin hollow carbon shell (PACS) was prepared via a facile template-assisted method. As the anode material of lithium-ion batteries, PACS exhibits high reversible capacity, excellent cycling stability, and superior rate performance. A high reversible capacity of 334 mA h g −1 and 90% kept of the theoretical capacity can still be maintained in PACS at a current density of 1 A g −1 even after 1000 cycles, which is ascribed to the unique hollow structure, ultrathin porous shells (4.7 nm), the doped nitrogen atoms, and high level of disorder degree. Meanwhile, the present study paves a milestone for the high-valued utilization of petroleum asphalt and other kinds of heavy oil.

We investigate the electronic structures and magnetism of Rh 3 Z (Z=Al, Ga, In, Si, Ge, Sn, Pb, Sb) with a DO 3 structure using the first-principle calculations. The Rh 3 Z (Z=Si, Ge, Sn, Pb) alloys have been predicted to be half-metallic ferromagnets at their equilibrium lattice parameters. The half-metallicity of Rh 3 Z (Z=Si, Ge, Sn, Pb) alloys can be kept in a quite large hydrostatic strain and tetragonal distortion. The magnetic properties are discussed. The Rh 3 Z (Z=Si, Ge, Sn, Pb) alloys do not follow the M t =Z t - 24 rule but instead of following the M t =Z t - 28 rule ( M t is the total magnetic moment per unit cell and Z t is the valence concentration). Moreover, all the alloys investigated in this paper have a negative formation energy, which implies that they are possible to be synthesized in reality.

Two organic quinoxaline dyes (WQ-1 and WQ-2) with a structure of quinoxaline-2, 3-diol as the electron withdrawing and anchoring group were synthesized and applied in the dye-sensitized solar cells. Fourier transform infrared spectroscopy and two other reference dyes (WQ-R1 and WQ-R2) without the hydroxyl groups were introduced to ascertain the adsorption properties of the dye series. The effect of the new electron acceptor and anchoring group on the performance of solar cells was investigated systematically. Under the standard light illumination (100 mW m−2), WQ-2 got an efficiency of 2.25%, with a short circuit photocurrent density of 5.51 mA cm−2, an open circuit voltage of 0.612 V and a fill factor of 66.74%.

Here we report a new strategy for preparation of water-soluble photoluminescent carbon quantum dots (CQDs) from petroleum coke. Petroleum coke was oxidized first in mixed concentrated H2SO4 and HNO3, and then functionalized by hydrothermal ammonia treatment. The as-made CQDs and nitrogen-doped CQDs (N-CQDs) were characterized by UV–Vis absorption spectroscope, fluorescence spectroscope, transmission electron microscope, atomic force microscope, Raman spectrometer, X-ray powder diffractometer, X-ray photoelectron spectroscope and Fourier transform infrared spectrometer. The results show that the quantum yield of CQDs increases greatly from 8.7 to 15.8%, and the fluorescent lifetime increases from 3.86 to 6.11 ns after the hydrothermal treatment in ammonia. Moreover, the fluorescent color of N-CQDs can be tuned through the amount of doped nitrogen. Both CQDs and N-CQDs are water-soluble, and have uniform particle distribution, strong luminescence, and highly fluorescent sensitivity to pH in a range of 2.0–12.0. The uniform size distribution and nitrogen-doping of N-CQDs help to lead to high yield of radiative recombination, resulting in improved fluorescence properties. This work offers a simple pathway to produce high quality and enhanced photoluminescent CQDs from petroleum coke.

High-resolution, long-term and accurate daily-precipitation is always difficult and rarely measured in the Qinghai-Tibet Plateau (QTP) because of the high altitude and complex terrain. The accuracy of satellite-based gridded precipitation products have been continuously improved recently which is crucial to the study of cryosphere ecology and environment. The goal of this study is to evaluate the accuracy of CHIRPS v2 (Climate Hazards Group Infrared Precipitation with Stations data, version 2) and MSWEP v2 (Multi-source weighted-Ensemble Precipitation, version 2) daily-precipitation products over the QTP during the period 1981–2015. Validation was done using a time series of daily-precipitation data obtained from 104 hydrometeorological stations distributed over the QTP. Error metrics (The correlation coefficient CC, the relative bias BIAS, and root mean square error RMSE) were used for accuracy evaluation and detectability indicators (probability of detection POD, false alarm ratio RFA, and critical success index CSI) were used for the analysis of detection capabilities of rainfall occurrence events. The results indicate that when compared to rain gauge observations, CHIRPS and MSWEP daily-precipitation products represent well the spatial and temporal distribution of the mean daily precipitation over the QTP, while both of them overestimate the daily-precipitation (0.18 mm/d for CHIRPS, 0.56 mm/d for MSWEP). MSWEP performed better than CHIRPS according to CC (MSWEP is 0.44, CHIRPS is 0.23) and RMSE (MSWEP is 4.21 mm, CHIRPS is 5.03 mm) and MSWEP showed better detection capabilities with higher POD (0.65), lower RFA (0.50) and higher CSI (0.39) in the QTP. Both products are less accurate in dry conditions (the north QTP, winter) than in moist conditions (the south QTP, summer). Light precipitation events (0–2 mm/d) are underestimated but heavy precipitation events (2–25 mm/d) are overestimated. CHIRPS and MSWEP have shown great potential to be able to be applied to the precipitation-related study of the QTP. Although the accuracy of MSWEP is higher than that of CHIRPS, the latter has higher spatial resolution (o.o5°) and is more suitable for small-scale studies.

FeIII porphyrin complexes as biomimetic catalysts display remarkable activity in the oxidation of dibenzothiophenes (DBTs) to the corresponding sulfones, in the absence of co-reductants or sacrificial agents, for deep desulfurization. The influence of the reaction conditions on the catalytic oxygenation was investigated. UV–vis spectra of FeIII porphyrin complexes under various reaction conditions revealed that temperature was a vital factor for the catalyst's lifetime. However, catalyst decomposition was not caused by thermal self-destruction but by oxygenation at high temperatures. The FeIII porphyrin complex was decomposed partly during the oxygenation, which was retarded by adding carbazole (CAR) to the reaction medium. FeIII porphyrins, substituted with electron-withdrawing groups (–Cl), showed higher efficiency than electron-donating groups (–OH). Radical scavenging experiments demonstrated that the oxygenation catalyzed by the FeIII porphyrin complex was not a free-radical reaction. Based upon the DBTs’ concentrations, obtained by gas chromatography, the catalytic oxygenation can be treated kinetically as a first-order reaction. Finally, a mechanism involving a two-step nucleophilic addition was proposed for the oxygenation.

Two series of chiral Schiff bases, 4a-e and 5a-e, prepared from the condensation of the mono-, di-, trib-romohydroxynaphthaldehyde or monoiodohydroxynaphthaldehyde with chiral amino alcohols, were ...

Carbon nanotube (CNT)-supported ruthenium catalysts, assembled at the interfaces of emulsion droplets, show excellent activity, selectivity, and stability for the selective oxidations of benzyl alcohol to benzaldehyde with oxygen or air as oxidant in the presence of water. The selective oxidation of benzyl alcohol over Ru/CNTs catalysts is greatly enhanced and quickened due to the presence of water. A reaction pathway is proposed, in which the promotion effect of water on the catalytic activity of Ru/CNTs is discussed. The as-made Ru/CNTs catalysts are also active for the aerobic oxidation of a variety of alcohols with a sulfur or nitrogen atom or a carbon–carbon double bond in the multiphase reaction system. Moreover, after the reactions, the catalysts can be easily separated and recycled by sedimentation.

The unique and significant promotion effect of water has been evidenced by the selective oxidation of benzyl alcohol to benzaldehyde over Au/TiO2 Catalysts. Water has dual promotional functions in the reaction system: to help form unique microdroplets in a multiphase reaction system and to assist the oxygen adsorption and activation. The conversion of benzyl alcohol at a molar ratio of water to solvent (p-xylene) of 7 is 7 times higher than in the absence of water. The present work has highlighted the potential of Au/TiO2 Catalysts in aerobic oxidation of alcohols in the unique multiphase reaction system with water as promoting solvent. (C) 2008 Elsevier B.V. All rights reserved.

Three anthraquinone dyes with carboxylic acid as anchoring group are designed and synthesized as sensitizers for dye-sensitized solar cells (DSSCs). Preliminary photophys. and photoelectrochem. measurements show that these anthraquinone dyes have very low performance on DSSC applications, although they have broad and intense absorption spectra in the visible region (up to 800 nm). Transient absorption kinetics, fluorescence lifetime measurements and d. functional theory (DFT) calcns. are conducted to investigate the cause of such low DSSC performance for these dyes. The strong electron-withdrawing character of the two carbonyl groups on anthraquinone framework may lie behind the low performance by suppressing the efficient electron injection from the dye to the conduction band of TiO2.

Chiral (pyrrolidine salen)Mn(III) complexes 1 with an N-benzoyl group and 2 with an N-isonicotinoyl group as well as the corresponding N-methyl (3) and N-benzyl (4) pyridinium salts of 2 were synth ...

Two dimeric chiral (pyrrolidine salen)Mn(III) complexes 3 and 4 were prepared, in which the two (pyrrolidine salen)Mn(III) units are linked either by a p-xylylene or by ap-phthalyl bridge. High yie ...

Friedel–Crafts alkylations of α-methylnaphthalene with long chain alkenes (C11–12) in liquid–solid phase over alkaline earth metal oxides like MgO, CaO, SrO and BaO modified HY zeolite catalysts have been investigated. Effect of BaO impregnated amount on the reaction was investigated. Results show that 1%BaO modified HY zeolite (1%BaO–HY) exhibits outstanding catalytic performances, and the stability of catalyst may be improved when modified by optimal alkaline earth metal oxide. Moreover, effects of reaction conditions like reaction temperature, volume hour space velocity (VHSV) and time on stream (TOS) on the 1%BaO–HY promoted alkylation were also studied. It is found that Bronsted acid centre is the main catalytic active centre, and Lewis acidic sites have an obvious promotion effect on reaction performance for the alkylation reaction.

A series of chiral (pyrrolidine salen)Mn(III) complexes were synthesized front N-aza-substituted (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-3.4-diaminopyrrolidine salen ligands. High yields and ...

HY zeolite promoted liquid–solid free-solvent alkylations of α-methylnaphthalene with long chain olefins have been performed in intermittent reactor. Effects of various reaction conditions like reaction temperature, dosage of catalyst and reaction time on the alkylation reaction were investigated. The alkylations were also carried out over alkaline earth and rare earth metal oxide modified HY, and effects of impregnated amount on the reactions were investigated simultaneously. It is found that 0.5% of La 2 O 3 modified HY exhibits outstanding catalytic performances, 94.0% of conversion for olefins and 100% of selectivity for the desired products were achieved. Moreover, the generation and reusability of deactivated HY zeolite catalyst were also studied. Results show that the catalytic performances of deactivated catalyst can be refreshed completely, and the regenerated catalyst can be further reused many times without decrease in its catalytic activity.

Alkylations of 1-and 2-methylnaphthalene with long-chain alkenes in different alkyl-containing amine ionic liquids were investigated at room temperature. The effects of both anions and cations of ionic liquids on the alkylations were studied in detail. Results show that the anions determine, to a large extent, the physical and chemical properties of ionic liquids, but organic cations mainly influence physical properties, and have only a little impact on the catalytic performance. High conversion of alkylating agent and excellent selectivity for the desired products were obtained. The products and unreacted reactants were easily isolated from catalysis systems by extraction with cyclohexane. Thanks to the less expensive reagents and the easier synthesis process, methyl and ethylamine chloroaluminate ionic liquids could become novel practical catalysts for long-chain alkylation of methylnaphthalene with alkenes.

This is the first of a series of papers concerning the transformation of propane over a H-ZSM5 catalyst comprising experimental data, a kinetic model, and molecular dynamics calculations. The aim of this work is to provide a more fundamental insight on the catalytic processes involving light alkanes activation over solid acid catalysts. Experimental data for propane cracking was collected in the temperature range 623–773 K and low propane feed partial pressures varying from 3.0 to 9.1 kPa. The results show the existence of two parallel reaction pathways: (1) two monomolecular initiation steps (protolytic cracking or dehydrogenation), characterized by a relatively high activation energy, which becomes predominant at low conversions and high temperatures. Bond rupture may occur on either a CC or CH position leading to stoichiometric amounts of methane and ethene, or hydrogen and propene, respectively, when extrapolated at zero conversion; (2) a bimolecular route (classical cracking mechanism) with lower activation energy which involves carbenium ions chain carriers, and whose relative importance grows with increasing conversion and decreasing temperature, as secondary products, mainly olefins, become important. It is also clear that dehydrogenation reactions are favored at low temperatures, while at higher temperatures cracking is the dominant reaction pathway.