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An oxygen-enhanced organosolv fractionation method to produce lignin from waste biomass was investigated. In this novel biorefinery process, mild conditions, i.e., temperature at 80 to 100 °C and pressure < 0.8 MPa, were employed to alleviate energy input and to retain the original lignin structure as much as possible. The results showed that the lignin yield was increased with increasing process temperature, ethanol concentration, and ratio of liquid to solid. Although little structural changes were observed, the normalized Infrared transmittance results revealed quantitative differences. Moreover, a basic kinetic study was conducted, and the results showed that there existed two stages with fast and slow rates during the delignification processes. Analysis of the fibers’ micro-structure also demonstrated the effectiveness of oxygen-enhanced organosolv fractionation. However, a phenol-based inducer could possibly further improve the efficiency based on the delignification mechanism of reactive oxygen species, which will be studied in future research.

Nitrogen-doped pyrolytic carbon coated Fe3O4 nanocrystals supported by large sheet-size graphene (N-pC/Fe3O4/G) were synthesized by a self-assembly process followed by heating to obtain a high-performance anode material. The 3D porous poly-melamine sponge (PMS) acted as a template for the assembly of graphene to form curved and hollow foam structure, and as a source of N-doped carbon coating of Fe3O4 nanocrystals. The N-pC/Fe3O4/G composite exhibits good reversible capacity of 825 mAh/g after 350 cycles at a high current density of 1 A/g, showing much better performance than either one of its two components. Its performance benefits from the long-range conductivity of the graphene foam and the short-range local conductivity of the N-doped carbon coating.

Rechargeable lithium-sulfur battery with a high theoretical energy density attracts intense attention, but it still often suffers from poor cyclability. Herein, a hierarchical porous carbon/graphene hybrid is designed to host sulfur for Li–S battery. The batteries exhibit good performances including a specific capacity of 1178 mA h g−1 after 70 cycles at 0.2C, a stable reversible capacity of 400 mA h g−1 after 600 cycles at 1.0C (80% retention). Extensive characterizations including adsorption-desorption isotherms, XRD, Raman spectroscopy, HAADF-STEM combining with soft XAS study the relationship between the structure and the performance of as-synthesized cathode material. The synergistic effect of graphene and hierarchical porous carbon provides the pathway of the electron and Li+ ingress/egress to react with the confined sulfur clusters, retard the loss of the polysulfide anions from the cathode and suppress the shuttle effect during long-term cycling process.

Solar cells are the key part of photovoltaic power system, and the online quality inspection of solar cells ensures conversion efficiency and usable lifetime of photovoltaic modules. However, automatic crack detection in EL images of solar cells has been a challenging task, owing to the heterogeneously textured background, low contrast between crack and surrounding background including randomly distributed crystal grains, the diversity of crack types, and so on. To address these challenges, this paper presents a new accurate and robust crack detection scheme for multicrystalline solar cells. Firstly, a novel steerable evidence filter is developed to generate the crack saliency map, which significantly enhances the contrast between crack and surrounding background. Secondly, a segmentation-based method including local threshold and minimum spanning tree is employed, which ensures the extraction of complete crack. Next, the crack can be accurately located in the inspection image by computing the crack skeleton. Finally, experimental results on defective and defect-free EL images show that the proposed scheme is accurate and robust, and various types of cracks can be correctly detected. The proposed scheme achieved average detection rate of 94.4% on the data set, which performs better than the previous methods.

Electron transfer (ET) and Auger recombination (AR) processes in quantum dots (QDs) are key mechanisms for the advance of QD-based devices. However, it still remains a challenge to promote ET and suppress AR simultaneously. Here, we use in situ high-pressure ultrafast transient absorption spectroscopy to explore the impact of pressure on the ET between CdSe/ZnS and anthraquinone (AQ) and AR dissolved in cyclohexane. Remarkably, under compression, ET lifetimes are shorten, while suppression of AR lifetimes is present. The promotion of ET is attributed to the shortened distance between CdSe/ZnS and AQ induced by pressure. We rationalize that for the AR suppression, pressure may enhance the formation of an alloy layer at the core/shell interface. These findings indicate that compression is an effective approach to promote ET and suppress AR simultaneously. This study highlights a brand-new approach for modulating ET and AR and provides new routes toward QD-based applications.

Rice samples were collected at 560 sites in 15 provinces across China in areas without known point mercury (Hg) sources. Total mercury (THg) and methylmercury (MeHg) concentrations were analyzed in these rice samples for risk assessment. Relatively low THg and MeHg concentrations were found in the majority of the white rice samples with an overall mean of 4.74 (1.06–22.7) μg kg−1 and 0.682 (0.03–8.71) μg kg−1, respectively. The means (range of) THg concentration of rice in each geographical region were 5.23 (1.07–19.5) μg kg−1, 5.14 (1.06–17.2) μg kg−1, 4.45 (1.41–17.2) μg kg−1, 4.20 (1.48–19.4) μg kg−1, 3.49 (1.49–10.7) μg kg−1, and 4.53 (1.30–19.4) μg kg−1 in east, centre, south, southwest, northwest and northeast, China, respectively, and the corresponding values for MeHg concentrations were 0.898 (0.127–8.35) μg kg−1, 0.603 (0.207–2.48) μg kg−1, 0.516 (0.032–1.50) μg kg−1, 0.615 (0.050–5.03) μg kg−1, 0.704 (0.148–2.41) μg kg−1 and 0.565 (0.035–8.71) μg kg−1, respectively. Hg contents in rice across China were found to be at background levels. Both the probable daily intakes (PDIs) of inorganic Hg (IHg) and MeHg from rice consumption showed low risks for general population in the investigated regions. Keywords: Rice, Mercury, Methylmercury, Probable daily intake, Health risk

Herein, a porous hydrostable metal–organic framework (MOF), CAU-1, was systematically studied for its adsorption performance of tinidazole (TNZ). Owing to the abundant −OH and −NH2 groups as well as the strong positively charged surface of the framework, the H-bond interaction and electrostatic interaction can play important roles in the adsorption process of TNZ. As a result, CAU-1 exhibits an excellent saturated adsorption capacity of TNZ (∼450 mg·g–1), superior to all of the previous reported porous adsorbents including other common MOFs. Meanwhile, the loaded TNZ molecules in CAU-1 can be released under simulated physiological conditions and the cumulative release amount can be controlled via the pH value of solution. This work demonstrates that such an MOF may be promising in TNZ removal, and rational selection of organic functional groups is an efficient strategy to design high-capacity adsorbents for the removal of antibiotics. Additionally, further study indicates that CAU-1 can serve as a pH-resp...

The twisted intramolecular charge transfer (TICT) state plays an important role in determining the performance of optoelectronic devices. However, for some nonfluorescent TICT molecules, the "invisible" TICT state could only be visualized by modifying the molecular structure. Here, we introduce a new facile pressure-induced approach to light up the TICT state through the use of a pressure-related liquid-solid phase transition of the surrounding solvent. Combining ultrafast spectroscopy and quantum chemical calculations, it reveals that the "invisible" TICT state can emit fluorescence when the rotation of a donor group is restricted by the frozen acetonitrile solution. Furthermore, the TICT process can even be effectively regulated by the external pressure. Our study offers a unique strategy to achieve dual fluorescence behavior in charge transfer molecules and is of significance for optoelectronic and biomedical applications.

Organic dye molecules with excited state proton transfer property gain huge scientific interest owing to the design flexibility and functional diversity. However, the anti-counterfeiting of a single dye molecule through intra- and intermocular excited state proton transfer (ESIPT and ESPT) has yet to be achieved. This study demonstrates a simple and efficient approach to realize the anti-counterfeiting of a single dye molecule in a PMMA film. We control the 1-hydroxypyrene-2-carbaldehyde (HP) to be fluorescent or not through two different solvents based on ESIPT and ESPT mechanisms. Furthermore, we investigate the detailed information of excited-state dynamics for HP in two solvents, aiming at exploring the mechanisms of totally different luminescence property, through the femtosecond transient absorption spectroscopy. Meanwhile, the theoretical TDDFT research sheds light on the correlation between molecular structure and luminescence character. Specifically, the fluorescence of the molecule in acetonitrile is quenched by an ESIPT (127 fs) induced intersystem crossing (11.8 ps) whereas the ESPT (195 fs) and following aldehyde group rotation (26.5 ps) make the molecule to exhibit a strong luminescence property in dimethyl sulfoxide. The results are promising and offer new avenues to realize the greener and sustainable anti-counterfeiting of a single dye molecule.

Indica-japonica hybrid rice cultivars show great yield potential but poor eating quality and require more nitrogen (N) input relative to japonica rice. However, the effect of N levels on the eating quality of indica-japonica hybrid rice is little known. A field experiment was carried out to investigate the effects of four N levels on two indica-japonica hybrid rice cultivars (Yongyou12 and Yongyou17) differing in eating quality. The results showed that the contents of amylose chains and water-insoluble storage proteins, especially prolamin, increased largely under a high N level, leading to deterioration of the rice-eating quality, although a low N level (100 N kg/ha) had a less negative effect on the eating quality. Moreover, both of the indica-japonica hybrids had high ratios of inferior grains (IG), and the ratio of IG increased with the N level. Grain weight and the immature ratio of IG were reduced and increased with the N level, respectively, which are also factors for deterioration of the eating quality. The two cultivars differed greatly in the responses of eating quality to the N level, with Yongyou17 being more sensitive than Yongyou12. The current results indicated that a high N level deteriorates the eating quality of indica-japonica hybrid rice mainly due to a large increase of IG.

Plants will meet various abiotic stresses during their growth and development. One of the important strategies for plants to deal with the stress is involved in metabolic regulation, causing the dramatic changes of metabolite profiles. Metabolomic studies have been intensively conducted to reveal the responses of plants to abiotic stress, but most of them were limited to one or at most two abiotic stresses in a single experiment. In this study, we compared the metabolite profiles of barley seedlings exposed to seven abiotic stresses, including drought, salt stress, aluminum (Al), cadmium (Cd), deficiency of nitrogen (N), phosphorus (P) and potassium (K). The results showed that metabolite profiles of barley under these stresses could be classified into three groups: osmotic stresses (drought and salt); metal stresses (Al and Cd) and nutrient deficiencies (N, P and K deficiencies). Compared with the control, some metabolites (including polyamines, raffinose and pipecolic acid) in plants exposed to all abiotic stresses changed significantly, while some other metabolites showed the specific change only under a certain abiotic stress, such as proline being largely increased by osmotic stress (drought and salinity), the P-containing metabolites being largely decreased under P deficiency, some amino acids (lysine, tyrosine, threonine, ornithine, glutamine and so on) showing the dramatic reduction in the plants exposed to N deficiencies, respectively. The current meta-analysis obtained a comprehensive view on the metabolic responses to various abiotic stress, and improved the understanding of the mechanisms for tolerance of barley to abiotic stress.

Antibiotic residues in wastewater have attracted great attention for their potential toxicity to environment. In this work, a zirconium-based metal–organic framework (PCN-777) was synthesized as adsorbent to remove cephalexin from water. Attributed to synergistic effect of the electrostatic interaction and coordination interaction between MOF framework and cephalexin, PCN-777 exhibits a high adsorption capacity of 442.48 mg·g−1, which is higher than those of reported adsorbents. The adsorption behavior follows Langmuir model and pseudo-second-order model. Besides, this MOF can be reused via a simple method. Therefore, PCN-777 may have a promising potential application for purification of waste water containing trace antibiotics.

Alkali‑oxygen cooking of lignocellulose offers lignin many structural properties and bioactivities for biorefinery. In this work, milled wood lignin (MWL) and alkali‑oxygen lignin (AOL) were isolated from rice straw and alkali‑oxygen black liquor, respectively. The lignin structure was characterized by spectroscopy and wet chemistry. Antioxidant activity of lignins was assessed by DPPH·and ABTS scavenging ability assay. Results showed the oxidization and condensation of lignin occurred during alkali‑oxygen cooking. The p-hydroxyphenyl was more easily removed from rice straw than guaiacyl and syringyl units. The ester or ether linkages derived from hydroxycynnamic acids, and the main interunit linkages, i.e. β–O–4′ bonds, were mostly cleaved. Lignin-xylan complex had high reactivity under alkali‑oxygen condition. Tricin, incorporated into lignin, was detected in MWL but was absent in AOL. Nitrobenzene oxidation showed MWL can well represent the protolignin of rice straw, and the products yield decreased dramatically after alkali‑oxygen cooking. AOL had higher radical scavenging ability than MWL indicating alkali‑oxygen cooking was an effective pathway for the enhancement of antioxidant activity of lignin.

High-efficiency removal of chloramphenicol (CAP) drug from waste water still faces a large challenge up to date. Herein, we report the first metal-organic framework-based adsorbent (PCN-222) for CAP and effective removal was achieved. PCN-222 exhibits a large adsorption capacity of 370 mg g−1, superior to some other MOFs and various reported adsorbents; and more importantly, the adsorption equilibrium can be quickly obtained at only 58 s. Besides, ∼99.0% of CAP can be removed from water in the low concentrations (including the concentrations found in real water). Further investigation indicates that H-bond interaction, electrostatic interaction and the special pore structure of PCN-222 all play important effects on the high-efficiency removal of CAP. Therefore, our work may provide a novel perspective for removing CAP or other antibiotic drugs from contaminated water.

In this work, the fluorescent CAU-1-(OH)2 was successfully exploited as a fluorescent probe for bismuth ion (Bi3+) in aqueous solutions, which is the first MOF-based fluorescent sensor for Bi3+ up to date. The MOF can exhibit bright green fluorescence in H2O for the intramolecular proton transfer process between the ligand and H2O molecule. In addition, the carboxylate and hydroxyl groups in the MOF can strongly coordinate with Bi3+. Accordingly, CAU-1-(OH)2 can selectively detect Bi3+ in water in 24 s. In addition, the limit of detection of this MOF was calculated to be 2.16 μM, superior to those of some traditional methods such as spectrophotometry and flow injection potentiometry.

Effective removal of toxic 1,5-naphthalenedisulfonic acid (NDS) and 2-naphthalenesulfonic acid (NSA) from contaminated water still faces a challenge to date. Herein, porous MIL-101, MIL-101-NH2, and MIL-101-SO3H were systematically studied for their adsorption performances toward these toxic molecules. Upon the introduction of −NH2 groups, H-bond interaction and electrostatic interaction were enhanced, and accordingly MIL-101-NH2 can exhibit more excellent adsorption capacity (NDS, 188.1 mg g–1; NSA, 285.0 mg g–1) compared to MIL-101-SO3H, MIL-101, and some other common adsorbents. Further study indicates that MIL-101-NH2 can be easily regenerated even after three adsorption processes. This work demonstrates that MIL-101-NH2 may have large potential in naphthalenesulfonic acids removal and rational selection of organic functional groups may be critical in construction of adsorbents.

In this work, a fundamental understanding of oxygen delignification distracted by dissolved lignin was investigated. In the new biorefinery model of shortening kraft pulping integrated with extended oxygen delignification process, increasing content of residual lignin in the original pulp could result in enhanced delignification efficiency, higher pulp viscosity and less carbonyl groups. However, the invalid oxygen consumption by dissolved lignin could be increased with the increase of process temperature and alkali dosage. The normalized ultraviolet absorbance (divided by absorbance at 280 nm) also showed that the content of chromophoric group in dissolved lignin decreased with oxygen delignification proceeded, both of which indicated that dissolved lignin could enhance the invalid oxygen consumption. Therefore, a conclusion that replacement of the liquor at the initial phase of oxygen delignification process would balance the enhancement of delignification efficiency and invalid oxygen consumption was achieved.

Electrochemical water splitting by a robust electrocatalyst plays a key role in hydrogen production for clean and sustainable energy. In this work, a kind of nanohybrid of graphene supported atomic Co and nanocrystalline Co3O4 was synthesized through electrochemical synthesis of atomic cobalt onto graphene using 1-Butyl-3-methylimidzolium tetrachlorocobalt [(BMIm)2CoCl4] as an electrolyte. By virtue of the synergistic effect of single-cobalt atoms and Co3O4 nanoparticles, the nanohybrid presents enhanced electrocatalytic performance toward the oxygen evolution reaction. The low onset potential is 0.49 V (vs. Ag/AgCl) and the overpotential of the current density of 10 mA cm−2 is 0.30 V in aqueous solution, which is comparable to commercial RuO2. Moreover, the nanohybrid exhibits remarkably long stability for over 45 h at a fixed potential of 0.6 V.

In situ X-ray diffraction and Raman scattering experiments using a diamond anvil cell revealed that Im-3-type KSbO3 remains stable up to 40.5 GPa with a bulk modulus K0 = 101.6 (7) GPa. Rietveld st...

Large-scale synthesis of either single-metal atom catalyst or graphene from graphite direct exfoliation at high yield is quite challenging. Here we demonstrated a scalable electrochemical approach to synthesize few-layer graphene flakes and isolated Fe atoms at the same time. It was found that graphite could be expanded in FeCl4--based ionic liquid at a low potential of 2 V. Fe isolated onto graphene resulted from electrochemical reactions of FeCl4--based intercalates. After annealing at the presence of nitrogen source, atomic Fe isolation was kept and coordinated with nitrogen. The paintable atomic layer material exhibited superior oxygen reduction reaction performance to Pt/C. The catalytic activity could be enhanced 30 times per gram and 100 times per metal atom, if Fe-Nx/graphene was compared with Pt/C (20 wt.% Pt) on the basis of metal content.

Density functional theory and time-dependent density functional theory methods were carried out to investigate the excited-state intramolecular charge transfer process (ICT) of coumarin 340 (C340) in tetrahydrofuran (THF) solvent for the first time. The plotted electrostatic potential and optimized geometric structures vividly indicated that the intermolecular hydrogen bond can be formed between the N–H group of C340 monomer and the oxygen atom of THF solvent. The analysis of frontier molecular orbitals and the differences in electronegativity confirmed the occurrence of ICT process in hydrogen-bonded complex C340-THF upon photoexcitation. The results of calculated bond lengths and bond energies revealed that the intermolecular hydrogen bond in C340-THF is significantly strengthened in the first excited state. Furthermore, the calculated electronic spectra, non-covalent interactions and IR spectra provided strong evidence for the hydrogen bond reinforce. Based on the theoretical calculations, we demonstrated that the ICT process in C340-THF can be facilitated effectively by the excited-state intermolecular hydrogen bond strengthening.

The excited-state double proton transfer (ESDPT) process of dipyrido[2,3-a:3',2'-i]carbazole (DPC) in ethanol (EtOH) solvent is investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The computational results provide convincing evidence that proton transfer did not occur spontaneously for the DPC monomer due to the lack of hydrogen bonds. Interestingly, after adding EtOH to DPC, two intermolecular hydrogen bonds were formed in the ground-state, and the intermolecular hydrogen bonds were strengthened in the excited-state, as confirmed by comparing the changes in the primary bond parameters. In addition, the charge transfer was observed in the DPC-EtOH complex compared with the DPC monomer. In particular, a reliable ESDPT process occurs within the system upon photoexcitation, which was monitored by the formation and disappearance of characteristic peaks in the IR spectrum. All results adequately proved that the participation of EtOH exerts a remarkable effect on the ESDPT process. Overall, our work not only comprehensively elaborated the simultaneous mechanism of ESDPT but can also pave the way towards the design and synthesis of novel molecules.

A catalyst consisting of atomic iron embedded in a new hierarchical carbon matrix was synthesised, and this catalyst exhibited superior performance in CO2 electroreduction. Bamboo-like carbon nanotubes were catalytically grown by Fe3C nanocrystals on graphene co-doped with atomic iron and nitrogen by a new approach of electrochemical oxidation of graphene films in an FeCl4−-based ionic liquid followed by annealing. The highly selective generation of CO from CO2 was achieved at a low overpotential of 0.55 V with a maximum CO faradaic efficiency of ∼95% for over 12 h.

It is interesting to convert industrial pitch to carbon based materials with high yield for energy storage owing to environmental and energy concerns. In this study, we activated coal tar pitch by a green process to obtain porous carbon sheets sandwiched by graphene, and further impregnated with 71% sulphur as the cathode for long-term cycling lithium–sulphur battery. In the presence of 4.0% of electrochemically exfoliated graphene flakes, the yield of carbon from pitch is as high as 72%, while the activation temperature of the pitch is as low as 700 °C. This carbon sheet has a high specific surface area of 2930 m2 g−1 and large pore volume of 1.5 cm3 g−1, which is nearly 3 times that of activated carbon derived from pitch without graphene. The cathode loaded with 71% sulfur (3.0 mg cm−2 of sulphur) demonstrated a discharge capacity of 1340 mA h g−1 at 0.05 C, which faded by only 0.001% per cycle at 1 C during 201–1500 cycles. Surface oxygen groups, 1.1 nm nanopore confinement and the sandwich structure of conductive graphene may contribute to the stable and reversible electrochemical reaction of the Li and sulphur clusters. Our investigation demonstrates that graphene can enhance the pitch activation to high quality microporous carbon and further confine sulphur species for long-term cycling Li–S batteries.

All carbon-electrode is ideal for supercapacitor, but synthesizing macro-level >3 GPa strong porous carbon electrode is challenging. Here, we presented an approach of synthesizing robust flexible “carbon-concrete” films integrating carbon fibers, graphene and hierarchical porous activated carbon. The method involved electrochemically spreading of carbon fiber bundles and in-situ activation of cellulose coating layers. It was found that 10–30 μm large literal size of electrochemically exfoliated graphene flakes could play a key role in in-situ fixing individual carbon fiber layer and protecting carbon fibers from activation corrosion. The new flexible porous “carbon-concrete” film with 40 μm thickness exhibited 5.3 GPa mechanical strength, specific area of 830 m2/g and broad pore size distribution. This light carbon material could be potentially used for integrating supercapacitor energy storage with automobiles.

The effects of atomic electronegativity (O, S and Se atoms) on the excited-state intramolecular proton transfer (ESIPT) properties of three compounds (3-HF, 3-HTF and 3-HSeF) were systematically studied using the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Furthermore, the antioxidant activities of the three compounds were evaluated using different parameters from the perspective of biological activities. The calculated results indicate that the generation of ESIPT is attributed to the excited-state intramolecular charge transfer owing to the change in electron density distribution on the frontier molecular orbitals and natural bond orbital (NBO) charge distribution of the O1 and O2 atoms at the S0 and S1 states. Moreover, 3-HTF shows the greatest red shift of the O1–H1 stretching peak and the lowest energy barrier at the S1 state among the three compounds, implying that 3-HTF would have the strongest intramolecular hydrogen bond at the S1 state, which is most beneficial for the occurrence of ESIPT. In addition, the decreased ionization potentials and energy gaps from 3-HF to 3-HTF and 3-HSeF means that the antioxidant activity of the compound would be enhanced along with the lowered atomic electronegativity. Interestingly, the lower ionization potentials and energy gaps of the compounds in keto forms suggest that the compound (3-HTF) easy to carry out ESIPT reaction would exhibit efficient antioxidant activity, which would establish the relationship between ESIPT reaction and antioxidant activity of the compound and provide a new notion for synthesizing more efficient antioxidants in experiments.

Low-cost preparation of durable electrocatalysts is vital for energy storage and conversion. Here, we integrated two methods of synthesizing isolated iron atoms into a special carbon matrix as an advanced electrocatalyst. Atomic Fe isolation and graphene nanomeshes or curved carbon nanoshells were almost synthesized simultaneously. The hierarchical atomic Fe/carbon material with 0.53 atom % Fe exhibited superior oxygen reduction reaction (ORR) performance to Pt–C (20 wt % Pt) with 40 mV more positive onset potential, larger current density, and stronger methanol-tolerant capability. We demonstrated that the catalytic active sites were Fe isolation and coordinated with nitrogen in the porous curved carbon-graphene matrix. This strategy could be developed into a general approach to prepare atomic metal/carbon electrocatalysts.

In the theory research and engineering practice, more basic inflatable models are essential for the mechanical property analysis of inflatable structures. Firstly, this paper presents a model of the tapered inflatable cantilever beam based on Timoshenko's theory and analyzes its deformation under a concentrated force. Moreover, the following forces resulting from internal pressure and taper ratio are introduced into the equilibrium equations of the deformed configuration. Thus, the model is optimized compared to the existing one for a straight beam. To verify the effectiveness and the superiority of the established model, the theoretical method based on the model and FEM method are compared by adopting an example about the tapered beams. Finally, the theoretical method is applied in analyzing the influence of geometry and estimating a valid range of taper ratio. By the criterion of the same amount material area, the optimum taper ratio is obtained.

In mercury (Hg) contaminated areas of Asia, human exposure to toxic methyl-Hg (MeHg) through a rice-based diet of locally produced crop may pose a health threat. Alternative cropping system to rice in such areas would be most desirable. In this study, corn, the leading cereal source in the world with large biomass, was demonstrated to accumulate an insignificant amount of MeHg from the soil in its edible portion compared to that in rice, suggesting corn being a very competitive alternative crop. By examining Hg stable isotope composition, Hg in the aerial parts of corn was found to be mostly from the atmosphere. Maize cropping worldwide is estimated to be a discemible sink of atmospheric Hg with approximately 44 Mg Hg accumulated in each growing season on a yearly basis, most of which is from foliar uptake of atmospheric Hg and this amount is comparable to litterfall Hg observed in North America and Europe. It is thus recommended to use corn as a replacement of rice in highly Hg-contaminated areas for remediation of Hg pollution in the food supply.

The electron transfer (ET) rate in quantum dot (QD)-molecular acceptor systems is dependent upon system reorganization energy (RE, λ), which comprises contributions from solvent (λ0) and reactants (λi). However, to date, the effect of λi on ET rate has been largely ignored. Herein, the ET from CdSe/ZnS QDs to 1-chloroanthraquinone (1-CAQ) in different solvents was investigated using ultrafast transient absorption spectroscopy as a means to evaluate the effect of λi on ET rate. The results revealed that ET rate is strongly solvent dependent. Amazingly, the ET rate in carbon disulfide is 300-times higher than that in n-dodecane. Theoretical calculations indicated that the λi contribution from 1-CAQ alone accounts for a large proportion of system RE and varies greatly in different solvents. Furthermore, the ET rate increases first and, then, decreases with the λ value in different solvents. This trend was interpreted consistently in terms of Marcus theory by adding λi to λ for different solvents. Thus, our present work demonstrates that the RE of the acceptor molecule has a non-negligible effect on ET rate, providing new insight into the mechanisms of ET process and for the development of QD-based devices.

It is of significance to analyze various small molecules with high efficiency using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). In this work, we synthesized N and B dual-doped 3D carbon (N, B-C) nanofiber as a promising MALDI matrix through a facile impregnation and thermal pyrolysis process. Compared to the control C nanofiber, the N and B codoping could enhance surface area, functional groups, defective and active sites, which was conducive to adsorb the laser and enrich the desorption/ionization of analytes. For the first time, the N, B-C nanofiber was utilized as a novel matrix for MALDI-TOF MS analysis of various small molecules both in the positive-ion and negative-ion modes. This matrix showed high signal to noise (S/N) ratio, excellent salt-tolerance, and homogeneous ion distribution for the analysis of amino acids, saccharides, polymers and surfactant, which was obviously superior to the traditional α-cyano-4-hydroxycinnamic acid (CHCA) and the control C nanofiber matrix. Noticeably, the wide linear ranges (0.05–5 mM) of glucose was achieved by MALDI-TOF MS with N, B-C nanofiber matrix. Meanwhile, the MALDI-TOF MS imaging could observe the change of different content glucose based on the ion peak of [M + Na]+. Furthermore, N, B-C nanofiber-assisted LDI-TOF MS has also been applied to identify and analyze the saccharides in the natural honey.

Northeast China possess large areas of agricultural farmlands that were reclaimed from earlier marsh wetlands in the past several decades, while the response of trace element like mercury (Hg) in this process were not fully understood. In the present study, total mercury (THg) and Hg isotope composition were determined in reservoir sediment cores of a reservoir, agricultural soils and forest soils in Northeast China to reveal the possible impacts of agricultural activities on Hg geochemistry in the reservoir. The more negative δ202Hg (↓0.35‰), increased concentrations of THg (↑22.4 ng g−1), and higher organic matter (OM) (↑10%) in the deeper than the upper layer sediments indicate noticeable Hg input about 50–60 years ago, which is coincident with the grand reclamation of marsh wetland in the study area. The gradual decrease in THg content and the increase of δ202Hg value in the upper sediment layer reflect the weakened reclamation and thus less Hg input in the later decades. Using a triple mixing model, it is estimated that more than half of Hg in this reservoir sediment was originated from the reclamation of marsh wetlands into farmlands in the earlier stage and soil erosion in the later period. The study demonstrated that Hg isotope signatures in reservoir sediment core can reflect the landscape changes, such as reclamation.

Characterizing the composition of mercury (Hg) isotopes in the atmospheric emissions of cement plants is critical to understand the global circulation of Hg because large quantities of Hg are released from this source annually. A pre-calciner cement plant in Guizhou Province in Southwest China was selected to investigate the mass dependent fractionation (MDF) and mass independent fractionation (MIF) of Hg in the entire production process and the speciated Hg isotope composition in stack gas. Significant MDF and insignificant MIF were observed in this cement plant. Different raw/correction materials have δ202Hg signals ranging from -1.68 to -2.19‰. Raw meal is featured with lighter Hg (δ202Hg = -2.83 ± 0.18‰) as results of Hg circulation and accumulation during the clinker production. Cement products possess negative δ202Hg values (-1.98 ± 0.02‰) due to the input of light δ202Hg isotopes through additives/retarder limestone, and fly ash and gypsum from coal-fired power plant (CFPPs). Speciated Hg isotopes in the stack gas of the kiln tail and kiln head show no significant differences, and δ202Hg and Δ199Hg in the discharged flue gas averaged at -2.03 ± 0. 31‰ and -0.03 ± 0.07‰, respectively, which has negative δ202Hg characteristics with other anthropogenic sources.

We have measured the alignment influence on ion yields of CH3I and CH3Br molecules in the laser intensity regime from 1013 W/cm2 to 1015 W/cm2. The hexapole state-selection technique combined with laser induced alignment has been employed to obtain aligned (〈P2(cosθ)〉=0.7) and anti-aligned (〈P2(cosθ)〉=-0.1) CH3I and CH3Br molecules. The ratio of saturation intensities observed for the CH3I and CH3Br molecules with different alignments are simulated using a modified PPT model for molecules considering different orbitals and a good agreement has been achieved, indicating the contribution from multiple orbitals in the ionization.

The T296V mutant of amorpha-4, 11-diene synthase catalyzes the abortive conversion of the natural substrate (E,E)-farnesyl diphosphate mainly into the acyclic product (E)-β-farnesene (88%) instead of the natural bicyclic sesquiterpene amorphadiene (7%). Incubation of the T296V mutant with (3R,6E)-nerolidyl diphosphate resulted in cyclization to amorphadiene. Analysis of additional mutants of amino acid residue 296 and in vitro assays with the intermediate analogue (2Z,6E)-farnesyl diphosphate as well as (3S,6E)-nerolidyl diphosphate demonstrated that the T296V mutant can no longer catalyze the allylic rearrangement of farnesyl diphosphate to the normal intermediate (3R,6E)-nerolidyl diphosphate, while retaining the ability to cyclize (3R,6E)-nerolidyl diphosphate to amorphadiene. The T296A mutant predominantly retained amorphadiene synthase activity, indicating that neither the hydroxyl nor the methyl group of the Thr296 side chain is required for cyclase activity.

Automatic crack defect detection for multicrystalline solar cells is a challenging task, owing to inhomogeneously textured background, disturbance of crystal grains pseudo defects, and low contrast between crack defect and background. In this paper, a novel structure-aware-based crack defect detection scheme (SACDDS) is proposed. Firstly, the structure features of crack defect and randomly distributed crystal grains are analyzed, and corresponding mathematical models are used to represent two structure features. Secondly, according to Hessian eigenvalues of the above mathematical models, the identification functions of linear-structure and blob-structure are obtained. Then, a novel structure similarity measure (SSM) function is designed by using the identification functions of two structures, which can highlight crack defect, suppress crystal grains simultaneously. It significantly weakens the interference of inhomogeneous texture and obtains uniform background. Further, in order to overcome non-uniform response of crack region and extract crack defect, a tensor voting-based non-maximum suppression (TV-NMS) method is developed. It improves the uniformity of crack defect response and extracts candidate crack defect pixels. Finally, an effective morphological operation is applied to remove non-crack pixels and complete crack defect can be located in the EL images. Experimental results show that the proposed method can completely extract crack defect in the inhomogeneously textured background, which is well effective and outperforms the previous methods.

It is challenging to realize a dual-ion mode of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for detecting small molecules. Herein, graphene coated by porous amorphous carbon with P-O surface group and codoped by phosphorus and nitrogen (O-P,N-C/G) was synthesized from an aerogel formed by phytic acid, polyaniline, and electrochemically exfoliated graphene. The carbon material synthesized has the feature of large surface area (583 m2/g), good electrical conductivity, strong UV absorption, heteroatom doping, and surface functional groups suitable for laser- induced desorption/ionization. It was employed as a novel matrix suitable for both positive-ion and negative-ion modes in MALDI-TOF MS for the analysis of various small molecules including amino acids, small peptides, saccharides, drugs, and environmental pollutants, significantly outperforming control materials and a traditional CHCA (α-cyano-4-hydroxycinnamic acid) or 2,5-dihydroxybenzoic (DHB) matrix. Remarkably, the detection limit of the anticancer drugs (5-fluorouracil and ellagic acid) reaches 50 pmol. In addition, nice MALDI-TOF MS images can be mapped to detect mixed amino acids corresponding to homogeneous distribution of ion intensity. The monosaccharides and disaccharides can be distinguished by using the new matrix. Last but not least, it can be used to quantitatively detect glucose in human serum and soft drinks (glucose/fructose, 203.1 mM) without adding standards.

In this paper, we report time resolved fluorescence resonance energy transfer (FRET) using femtosecond ultrafast transient absorption spectroscopy. The lifetimes of FRET are strongly dependent on the molecular concentration and ratio of donor and acceptor. Also, in the FRET, photoinduced intermolecular charge transfer (PICT) is also investigated theoretically. The driving force for PICT in FRET system equals the reorganization energy, which gives barrier-less charge transfer according to Marcus theory. The rates of PICT in the FRET system can be estimated with our simplified Marcus equation. Our results of PICT in FRET system provide a new efficient way for the charge transfer in donor-acceptor system.

Lignin and lignin-carbohydrate complexes are important polymers for lignocellulosic biorefinery and functional materials, but those in ginkgo shells are not effectively analyzed and exploited. Based on this background, milled wood lignins (MWLML and MWLFZ) and lignin-carbohydrate complexes (LCCML and LCCFZ) were isolated from the shells of Ginkgo biloba L. cv. Damaling (ML) and Ginkgo biloba L. cv. Dafozhi (FZ) correspondingly, and were structurally characterized by comprehensive NMR spectroscopy. The results showed that ginkgo shells exhibited higher lignin (42%) and xylan (20%) content than general softwood species. Isolated MWLs were rich in guaiacyl units with the presence of ferulates and p-coumarates, and the molecular formula was C9H7.93O2.73(OCH3)0.81 and C9H7.87O2.76(OCH3)0.88 for MWLML and MWLFZ, respectively. Phenolic hydroxyl of MWLML (1.38 mmol/g) and MWLFZ (1.23 mmol/g) in ginkgo shells was much less than that in general softwoods, suggesting a higher etherification and condensation degree of ginkgo shells lignin, and &beta, 5&prime, &alpha, O-4&prime, and 4-O-5&prime, bonds were the main condensed structures. O-acetylated &beta, d-xylopyranoside and &beta, d-mannopyranoside were the main polysaccharides associated with lignin, and the acetyl groups frequently acylate the C2 and C3 positions. LCCML had more phenyl glycoside (0.035/Ar) and less &gamma, ester (0.026/Ar) linkages than LCCFZ.

The effects of lignin-combined manganese ion, iron ion, and lignin-combined iron and manganese on the decomposition of hydrogen peroxide were investigated. Elemental analysis and inductively coupled plasma-atomic emission spectrometry were used to analyze the chemical features of the lignin composites and the amount of metal ions present in the solution or adsorbed on lignin, respectively. The results showed that the main transition metal elements remaining in the precipitated lignin were Fe, Mn, and Cu. The hydrogen peroxide decomposition in the presence of lignin-combined transition metal was represented by pseudo-first-order kinetics, and the pseudo-first-order rate constant (kobs) of peroxide decomposition with lignin-combined iron was 0.0068 min-1, while it was 0.0063 min-1 in the presence of lignin-combined manganese. A synergistic effect of manganese and iron combined with lignin on peroxide decomposition was demonstrated, and a kobs value of 0.0053 min-1 was obtained. The mixed addition of magnesium sulfate (MgSO4), sodium silicate (Na2SiO3), and ethylene diamine tetraacetic acid disodium salt (Na2EDTA) resulted in an optimal reduction in peroxide decomposition when single lignin-combined metal ion existed. However, adding Na2EDTA alone had an optimal effect on the reduction of peroxide decomposition in the presence of lignin-combined iron and manganese, with a kobs value of 0.0004 min-1.

Robust crack defect detection in solar cells has been challenging because of the inhomogeneously textured surface, low contrast between crack defect and background, the diversity of crack types, and so on. To overcome these challenges, this paper presents a new robust crack defect detection scheme for multicrystalline solar cells. Firstly, a steerable evidence filter is designed to process EL image to obtain the response map, which enhances the contrast between crack and background and provides evidence for the presence of crack defect. Secondly, complete crack extraction from the response map is employed. Finally, the complete crack can be located in the inspection image by the crack skeleton extraction. Experimental results on defective and defect-free EL images show that the proposed scheme is robust, and various cracks can be effectively detected, which outperforms the previous methods.

The porous metal–organic frameworks, MIL-101, MIL-101-SO3H and MIL-101-NH2 were used for the removal of harmful drug (rocephin) from water via adsorption. The kinetics study suggests that the adsorption onto all the MOFs follows the pseudo-second-order model. The adsorption isotherms results suggest that the adsorption onto MIL-101 and MIL-101-NH2 fits well with Langmuir model and the maximum adsorption capacities are calculated to 204.08 mg g−1 and 277.78 mg g−1, respectively; while the adsorption onto MIL-101-SO3H cannot fit well with both Langmuir and Freundlich models and the maximum adsorption capacity in the experiment is 25 mg g−1. Furthermore, the effect of pH as well as the adsorption mechanism was analysed systematically. It was found that electrostatic interaction as well as hydrogen-bond interaction plays dominant roles in adsorption of rocephin, and MIL-101-NH2 with abundant amino groups can exhibit better adsorption capacity and removal percentage towards rocephin than MIL-101, MIL-101-SO3H, and some other common adsorbents. In addition, co-existed Zn(NO3)2 can induce a large improvement of rocephin adsorption performance of MIL-101-NH2. At last, MIL-101-NH2 demonstrates to be a renewable adsorbent. In conclusion, we suggest MIL-101-NH2 is a promising adsorbent for effective removal of rocephin in water.

Li3PO4 and Co3(PO[Formula: see text]8H2O precursors, precipitated within a micro reactor using ethyl alcohol as anti-solvent, are sintered to form nanosphere-like LiCoPO4. Even without carbon coating, the resulting sample with 2.1[Formula: see text]wt.% Li3PO4 existence presents surprisingly high initial discharge capacity (up to 164[Formula: see text]mAh/g and 787[Formula: see text]Wh/kg at 0.1C) and superior high rate performance (117[Formula: see text]mAh/g and 561[Formula: see text]Wh/kg at 5C).

Excited-state charge-carrier dynamics governs the performance of organometal trihalide perovskites (OTPs) and is strongly influenced by the crystal structure. Characterizing the excited-state charge-carrier dynamics in OTPs under high pressure is imperative for providing crucial insights into structure-property relations. Here, we conduct in situ high-pressure femtosecond transient absorption spectroscopy experiments to study the excited-state carrier dynamics of CH3NH3PbBr3 (MAPbBr3) under hydrostatic pressure. The results indicate that compression is an effective approach to modulate the carrier dynamics of MAPbBr3. Across each pressure-induced phase, carrier relaxation, phonon scattering, and Auger recombination present different pressure-dependent properties under compression. Responsiveness is attributed to the pressure-induced variation in the lattice structure, which also changes the electronic band structure. Specifically, simultaneous prolongation of carrier relaxation and Auger recombination is achieved in the ambient phase, which is very valuable for excess energy harvesting. Our discussion provides clues for optimizing the photovoltaic performance of OTPs.