Showing papers by "Zhen Li published in 2014"
TL;DR: The gram-scale synthesis of single-crystalline GQDs by a facile molecular fusion route under mild and green hydrothermal conditions is reported, which bestowed with excellent optical properties such as brightexcitonic fluorescence, strong excitonic absorption bands extending to the visible region, large molar extinction coefficients and long-term photostability.
Abstract: Graphene quantum dots (GQDs) have various alluring properties and potential applications, but their large-scale applications are limited by current synthetic methods that commonly produce GQDs in small amounts. Moreover, GQDs usually exhibit polycrystalline or highly defective structures and thus poor optical properties. Here we report the gram-scale synthesis of single-crystalline GQDs by a facile molecular fusion route under mild and green hydrothermal conditions. The synthesis involves the nitration of pyrene followed by hydrothermal treatment in alkaline aqueous solutions, where alkaline species play a crucial role in tuning their size, functionalization and optical properties. The single-crystalline GQDs are bestowed with excellent optical properties such as bright excitonic fluorescence, strong excitonic absorption bands extending to the visible region, large molar extinction coefficients and long-term photostability. These high-quality GQDs can find a large array of novel applications in bioimaging, biosensing, light emitting diodes, solar cells, hydrogen production, fuel cells and supercapacitors.
743 citations
TL;DR: These porous hollow ZnO/ZnFe2O4/C octahedra exhibit significantly enhanced electrochemical performances with high rate capability, high capacity, and excellent cycling stability when evaluated as an anode material for lithium-ion batteries.
Abstract: Novel porous ZnO/ZnFe2O4/C octahedra with hollow interiors are fabricated by a facile self-sacrificing template method involving the refluxing synthesis of hollow, metal-organic framework octahedra in solution and subsequent thermal annealing in N2 When evaluated as an anode material for lithium-ion batteries, these porous hollow ZnO/ZnFe2O4/C octahedra exhibit significantly enhanced electrochemical performances with high rate capability, high capacity, and excellent cycling stability
671 citations
TL;DR: An ordered meso-microporous core-shell carbon (MMCS) as a sulfur container, which combines the advantages of both mesoporous and microporous carbon, is presented, demonstrating that the diffusion of the polysulfides into the bulk electrolyte can be greatly reduced.
Abstract: For lithium–sulfur batteries, commercial application is hindered by the insulating nature of sulfur and the dissolution of the reaction intermediates of polysulfides. Here, we present an ordered meso-microporous core–shell carbon (MMCS) as a sulfur container, which combines the advantages of both mesoporous and microporous carbon. With large pore volume and highly ordered porous structure, the “core” promises a sufficient sulfur loading and a high utilization of the active material, while the “shell” containing microporous carbon and smaller sulfur acts as a physical barrier and stabilizes the cycle capability of the entire S/C composite. Such a S/MMCS composite exhibits a capacity as high as 837 mAh g–1 at 0.5 C after 200 cycles with a capacity retention of 80% vs the second cycle (a decay of only 0.1% per cycle), demonstrating that the diffusion of the polysulfides into the bulk electrolyte can be greatly reduced. We believe that the tailored highly ordered meso-microporous core–shell structured carbon ...
534 citations
TL;DR: In this article, high fluorescent cysteine-capped CdTe/CdS core-shell nanowires were successfully synthesized by reacting CdCl2 with NaHTe in aqueous solution under refluxing at 100°C for 140min.
Abstract: Highly fluorescent cysteine-capped CdTe/CdS core–shell nanowires were successfully synthesized by reacting CdCl2 with NaHTe in aqueous solution under refluxing at 100 °C for 140 min. On increasing the reaction time from 10 to 140 min, CdTe/CdS nanocrystals gradually grew into nanorods and eventually completely evolved into nanowires. The nanowires have amino and carboxyl functional groups on their surfaces and can be well dispersed in aqueous solution. The as-prepared CdTe/CdS nanowires show a fluorescence quantum yield (QY) of 7.25 % due to the unique nature of cysteine and the formation of a CdS shell on the surface of the CdTe core, they have a narrower diameter distribution (d = ~5 nm) and a length in the range of 175–275 nm, and their aspect ratio is between 1/35 and 1/55.
474 citations
TL;DR: The flexible and transparent CNT network film shows great potential for realizing flexible and semitransparent perovskite solar cells.
Abstract: Organic–inorganic metal halide perovskite solar cells were fabricated by laminating films of a carbon nanotube (CNT) network onto a CH3NH3PbI3 substrate as a hole collector, bypassing the energy-consuming vacuum process of metal deposition. In the absence of an organic hole-transporting material and metal contact, CH3NH3PbI3 and CNTs formed a solar cell with an efficiency of up to 6.87%. The CH3NH3PbI3/CNTs solar cells were semitransparent and showed photovoltaic output with dual side illuminations due to the transparency of the CNT electrode. Adding spiro-OMeTAD to the CNT network forms a composite electrode that improved the efficiency to 9.90% due to the enhanced hole extraction and reduced recombination in solar cells. The interfacial charge transfer and transport in solar cells were investigated through photoluminescence and impedance measurements. The flexible and transparent CNT network film shows great potential for realizing flexible and semitransparent perovskite solar cells.
420 citations
TL;DR: In this paper, S2−4 and S8/S2-4 composites with highly ordered microporous carbon as a confining matrix are fabricated and the electrode mechanism of the S2 −4 cathode is investigated.
Abstract: In lithium-sulfur batteries, small S2–4 molecules show very different electrochemical responses from the traditional S8 material. Their exact lithiation/delitiation mechanism is not clear and how to select proper electrolytes for the S2–4 cathodes is also ambiguous. Here, S2–4 and S8/S2–4 composites with highly ordered microporous carbon as a confining matrix are fabricated and the electrode mechanism of the S2–4 cathode is investigated by comparing the electrochemical performances of the S2–4 and S2–4/S8 electrodes in various electrolytes combined with theoretical calculation. Experimental results show that the electrolyte and microstructure of carbon matrix play important roles in the electrochemical performance. If the micropores of carbon are small enough to prevent the penetration of the solvent molecules, the lithiation/delithiation for S2–4 occurs as a solid-solid process. The irreversible chemically reactions between the polysulfudes and carbonates, and the dissolution of the polysulfides into the ethers can be effectively avoided due to the steric hindrance. The confined S2–4 show high adaptability to the electrolytes. The sulfur cathode based on this strategy exhibits excellent rate capability and cycling stability.
392 citations
TL;DR: In this article, a Se composite confined within porous carbon nanospheres (Se/PCNs) was developed as a cathode for advanced Li-Se battery, which exhibited impressive cycling stability over 1200 cycles with a capacity decay as low as 0.03% per cycle.
224 citations
TL;DR: Device results show that the novel synthesized materials could be applied as bifunctional materials, namely blue light‐emitting and hole‐transporting materials, with comparable EL efficiencies, and the ηC,max and ηext,max are among the best EL performance for blue AIE luminogens.
Abstract: Great efforts have been devoted to seek novel approaches for constructing blue fluorescent materials, which is one of the most important prerequisites for the commercialization of OLEDs. In recent years, various outstanding luminogens with aggregation-induced emission characteristic exhibit promising applications as emitters, but blue AIE fluorophores with excellent EL performance are still very scarce. Here, five hole-dominated blue AIE molecules are demonstrated by adopting construction approaches of changing linkage modes and increasing intramolecular torsion together, with the aim to restrict conjugation lengths without sacrificing good EL data. Device results show that the novel synthesized materials could be applied as bifunctional materials, namely blue light-emitting and hole-transporting materials, with comparable EL efficiencies, and the ηC,max and ηext,max are up to 8.03 cd A−1 and 3.99% respectively, which is among the best EL performance for blue AIE luminogens.
133 citations
TL;DR: It was found the reaction time and the amount of Ag nanowires play crucial roles in the formation of well-defined 1D Ag@Cu2O core-shell heteronanowires.
Abstract: A novel class of one-dimensional (1D) plasmonic Ag@Cu2O core–shell heteronanowires have been synthesized at room temperature for photocatalysis application. The morphology, size, crystal structure and composition of the products were investigated by XRD, SEM, TEM, XPS, and UV–vis instruments. It was found the reaction time and the amount of Ag nanowires play crucial roles in the formation of well-defined 1D Ag@Cu2O core–shell heteronanowires. The resultant 1D Ag@Cu2O NWs exhibit much higher photocatalytic activity toward degradation of organic contaminants than Ag@Cu2O core–shell nanoparticles or pure Cu2O nanospheres under solar light irradiation. The drastic enhancement in photocatalytic activity could be attributed to the surface plasmon resonance and the electron sink effect of the Ag NW cores, and the unique 1D core–shell nanostructure.
129 citations
TL;DR: In this article, a hierarchical layered K 0.27 MnO 2 microflowers are firstly synthesized via a facile and efficient route based on a topochemical reaction process.
126 citations
TL;DR: Four BTPE derivatives are prepared which give blue or deep-blue EL emissions when used as emitters in non-doped OLEDs, as the result of the tuned dihedral angles of the biphenyl cores.
TL;DR: In this paper, a review of the most recently improvements in dimensionless figure of merit (ZT) in different kinds of inorganic and organic thermoelectric (TE) materials is presented.
Abstract: Direct conversion of heat into electricity through advanced thermoelectric (TE) materials has been one of the most attractive solutions to the severe environmental and energy issues facing humanity. In recent years, great progress has been made in improving their dimensionless figure of merit (ZT), which determines the conversion efficiency of TE devices. ZT is related to three “interlocked” factors—the Seebeck coefficient, electrical conductivity, and thermal conductivity. These three factors are interdependent in bulk TE materials, and altering one changes the other two. The difficulty in simultaneously optimizing them caused TE research to stagnate, until great reductions in thermal conductivity were both theoretically and experimentally proven in nanomaterials in 1993. In this review, we first introduce some TE fundamentals and then review the most recently improvements in ZT in different kinds of inorganic and organic TE materials, which is followed by an investigation of the outlook for new directions in TE technology.
TL;DR: In this article, hole-dominated triphenylamine (TPA) and tetraphenylethene (TPE) moieties together with different linkage positions were successfully synthesized with confirmed structures, and their thermal, optical and electronic properties were fully investigated.
Abstract: In this paper, by merging the hole-dominated triphenylamine (TPA) and tetraphenylethene (TPE) moieties together with different linkage positions, four derivatives of 1,2-bis[4′-(diphenylamino)biphenyl-4-yl]-1,2-diphenylethene (2TPATPE) were successfully synthesized with confirmed structures, and their thermal, optical and electronic properties were fully investigated. Thanks to the introduction of the meta-linkage mode on the TPE core, their π-conjugation length could be effectively restricted to ensure blue emission. The non-doped OLEDs based on these four emitters exhibit blue emissions from 443–466 nm, largely blue-shifted with respect to the green emission of 2TPATPE (514 nm). Meanwhile, good electroluminescence efficiencies with Lmax, ηC,max, and ηP,max of up to 8160 cd m−2, 3.79 cd A−1, and 2.94 Im W−1 respectively, have also been obtained, further validating our rational design of blue AIE fluorophores.
TL;DR: This article comprehensively summarizes state-of-the-art fluorescence imaging using ultra-small nanoparticles as probes, including quantum dots, metal nanoclusters, carbon nanomaterials, up-conversion, and silicon nanmaterials.
Abstract: The novel optical, electrical, and magnetic properties of ultra-small inorganic nanoparticles make them very attractive in diverse applications in the fields of health, clean and renewable energy, and environmental sustainability. This article comprehensively summarizes state-of-the-art fluorescence imaging using ultra-small nanoparticles as probes, including quantum dots, metal nanoclusters, carbon nanomaterials, up-conversion, and silicon nanomaterials.
TL;DR: In this paper, reduced graphene oxide/cuprous oxide (RGO/Cu 2 O) composite films were directly synthesized on the surface of copper foil substrates through a straight redox reaction between GO and Cu foil via a hydrothermal approach.
TL;DR: In this article, the authors considered ZrO2, Al2O3 and SiO2 as supports to disperse La(x)A(1-x)Fe(y)B(1y)O(3) materials and different supports induce great differences in the reaction activity.
TL;DR: In this paper, Nitrogen-doped activated carbons (N-ACs) with controlled nitrogen doping and analogous microporous structures were prepared by pyrolysis of poly[(pyrrole-2,5-diyl)-co-(benzylidene)] (PPCB), and their comprehensive electrochemical properties, such as cyclic voltammograms, galvanostatic charge-discharge and electrochemical impedance spectrum, electrochemical capacitive performance, power density and long cyclic stability, were studied.
Abstract: Nitrogen-doped activated carbons (N-ACs) with controlled nitrogen doping and analogous microporous structures were prepared by pyrolysis of poly[(pyrrole-2,5-diyl)-co-(benzylidene)] (PPCB). The obtained N-ACs were thoroughly characterized using HRTEM, FESEM, BET, FTIR and XPS for their morphology, surface area and chemical composition. The N-ACs were further used to fabricate supercapacitors, and their comprehensive electrochemical properties, such as cyclic voltammograms, galvanostatic charge–discharge, electrochemical impedance spectrum, electrochemical capacitive performance, power density and long cyclic stability, were studied. The galvanostatic charge–discharge (GC) measurements on N-ACs produced at 700 °C and 800 °C show a high specific capacitance (up to 525.5 F g−1 and an energy density of ca. 262.7 W h kg−1 at 0.26 A g−1) in alkaline media (2 M KOH). More importantly, the capacitance remains practically identical when the scan rate was increased from 0.26 to 26.31 A g−1. The observed capacitance retention (∼99.5%) of N-ACs is remarkably stable for electrodes even after 4000 cycles, due to the presence of nitrogen at the surface and in the graphitic edge planes. The nitrogen content plays a significant role in producing micropore dominated ACs and in facilitating the transfer of ions through pores on the surface. The precursor (PPCB) used is cheap and can easily be prepared, making it promising for the large-scale production of N-ACs as excellent electrode materials for supercapacitors.
TL;DR: In this article, the influence of reaction parameters, including precursor concentration, precursor ratio, precursor type, reaction time, reaction temperature, solvent, and organic ligands, on the size, morphology, crystalline structure, and composition of the resultant copper telluride nanostructures was comprehensively investigated.
Abstract: Copper telluride nanocubes, nanosheets, and nanoparticles were prepared by a solvothermal method under the protection of an inert atmosphere. The influence of reaction parameters, including precursor concentration, precursor ratio, precursor type, reaction time, reaction temperature, solvent, and organic ligands, on the size, morphology, crystalline structure, and composition of the resultant copper telluride nanostructures was comprehensively investigated. The results showed that the crystal structure and composition of the resultant nanostructures varied case by case, demonstrating the complexity of copper tellurides, despite their simple molecular formula. The obtained copper telluride nanostructures were tested as anodes in lithium ion batteries. The assembled Li/LiPF6/CuxTe cells exhibit extremely high cycling stability (up to 5000 cycles) and their highest specific capacity is 280 mA h g−1. The results also showed better performance of the Cu2−xTe nanosheet electrodes than those of electrodes made from nanoparticles and nanocubes, demonstrating the importance of controlling the morphology of copper telluride during preparation.
TL;DR: A novel dual coaxial nanocable sulfur composite fabricated with multi-walled nanotubes, nitrogen-doped porous carbon (NPC) and polyethylene glycol (PEG) as a cathode material for Li-S batteries shows good cycling stability and excellent rate capability.
Abstract: Lithium–sulfur batteries have great potential for some high energy applications such as in electric vehicles and smart grids due to their high capacity, natural abundance, low cost and environmental friendliness. But they suffer from rapid capacity decay and poor rate capability. The problems are mainly related to the dissolution of the intermediate polysulfides in the electrolyte, and to the poor conductivity of sulfur and the discharge products. In this work, we propose a novel dual coaxial nanocable sulfur composite fabricated with multi-walled nanotubes (MWCNT), nitrogen-doped porous carbon (NPC) and polyethylene glycol (PEG), i.e. MWCNTs@S/NPC@PEG nanocable, as a cathode material for Li–S batteries. In such a coaxial structure, the middle N-doped carbon with hierarchical porous structure provides a nanosized capsule to contain and hold the sulfur particles; the inner MWCNTs and the outer PEG layer can further ensure the fast electronic transport and prevent the dissolution of the polysulfides into the electrolyte, respectively. The as-designed MWCNT@S/NPC@PEG composite shows good cycling stability and excellent rate capability. The capacity is retained at 527 mA h g−1 at 1 C after 100 cycles, and 791 mA h g−1 at 0.5 C and 551 mA h g−1 at 2 C after 50 cycles. Especially, the high-rate capability is outstanding with 400 mA h g−1 at 5 C.
TL;DR: In this article, a one-step corrosion process was used to synthesize CuO nanosheets, which can be used as anode material for both lithium-ion battery (LIB) and NIB.
TL;DR: The results demonstrate the potential of CuAgSe to simultaneously serve (at different temperatures) as both an n-type and a p-type thermoelectric material.
Abstract: Surfactant-free CuAgSe nanoparticles were successfully synthesized on a large scale within a short reaction time via a simple environmentally friendly aqueous approach under room temperature. The nanopowders obtained were consolidated into pellets for investigation of their thermoelectric properties between 3 and 623 K. The pellets show strong metallic characteristics below 60 K and turn into an n-type semiconductor with increasing temperature, accompanied by changes in the crystal structure (i.e., from the pure tetragonal phase into a mixture of tetragonal and orthorhombic phases), the electrical conductivity, the Seebeck coefficient, and the thermal conductivity, which leads to a figure of merit (ZT) of 0.42 at 323 K. The pellets show further interesting temperature-dependent transition from n-type into p-type in electrical conductivity arising from phase transition (i.e., from the mixture phases into cubic phase), evidenced by the change of the Seebeck coefficient from −28 μV/K into 226 μV/K at 467 K. ...
TL;DR: In this article, the authors carried out first-principles density functional theory calculations to investigate CO2, N2, CH4, and H2 adsorption on the amphoteric regioselective B80 fullerene.
Abstract: Exploring advanced materials for efficient capture and separation of CO2 is important for CO2 reduction and fuel purification. In this study, we have carried out first-principles density functional theory calculations to investigate CO2, N2, CH4, and H2 adsorption on the amphoteric regioselective B80 fullerene. Based on our calculations, we find that CO2 molecules form strong interactions with the basic sites of the B80 by Lewis acid–base interactions, while there are only weak bindings between the other three gases (N2, CH4, and H2) and the B80 adsorbent. The study also provides insight into the reaction mechanism of capture and separation of CO2 using the electron deficient B80 fullerene.
TL;DR: In this article, the authors reported the fabrication of long titanium dioxide nanotube arrays with highly c-axis preferentially oriented crystallization and a high concentration of oxygen vacancies by second anodization in ethylene glycol and annealing under poor-oxygen conditions.
Abstract: We report the fabrication of long titanium dioxide nanotube arrays with highly c-axis preferentially oriented crystallization and a high concentration of oxygen vacancies by second anodization in ethylene glycol and annealing under poor-oxygen conditions. By optimizing the growth and annealing conditions, the [001] oriented crystallization is maximized, and 31.7% of the total Ti ions exists as Ti3+ ions. The carrier density of the [001]-oriented TiO2 nanotube arrays is two orders of magnitude higher than that of the randomly oriented TiO2 nanotube arrays. The unusual c-textured crystallization confined within nanotubes may involve the formation of TiO62− octahedra with a gradient distribution along the tube axis, preferential nucleation at the top, and preferential growth downwards along the c axis. Because of the c-axis preferential orientation and a high-concentration of oxygen vacancies, long TiO2 nanotube arrays can serve as superior electrodes for both lithium ion batteries and supercapacitors without the addition of any conductive agents. Long c-oriented TiO2 nanotube arrays deliver reversible capacities of 293 mA h g−1 at 0.5 C and 174 mA h g−1 at 5 C with Coulombic efficiencies of over 99%, and hold an areal capacitance of 8.21 mF cm−2 with an 85% capacitance retention after 5000 cycles. Double roles played by oxygen vacancies are identified in increasing electrical conductivity and activating the rich-Li phase.
TL;DR: Two aggregation-induced emission active luminogens (TPE-pTPA and TPE-mTPA) were successfully synthesized and exhibited blue or deep-blue emissions, low turn-on voltages, and high electroluminescence efficiencies.
Abstract: Two aggregation-induced emission active luminogens (TPE-pTPA and TPE-mTPA) were successfully synthesized. For comparison, another six similar compounds were prepared. Because of the introduced hole-dominated triphenylamine (TPA), fluorene groups with high luminous efficiency, and unconjugated linkages, the π conjugation length of the obtained luminogens is effectively restricted to ensure their blue emission. The undoped organic light-emitting diodes based on TPE-pTPA and TPE-mTPA exhibited blue or deep-blue emissions, low turn-on voltages (3 V), and high electroluminescence efficiencies with Lmax, ηC,max, and ηP,max values of up to 26,697 cd m(-2), 3.37 cd A(-1), and 2.40 Lm W(-1).
TL;DR: These transgenic zebrafish models with well-defined oncogene-induced tumors are valuable tools for molecular classification of human HCCs and for understanding of molecular drivers in hepatocarcinogenesis in each human H CC subgroup.
Abstract: Previously three oncogene transgenic zebrafish lines with inducible expression of xmrk, kras or Myc in the liver have been generated and these transgenic lines develop oncogene-addicted liver tumors upon chemical induction. In the current study, comparative transcriptomic approaches were used to examine the correlation of the three induced transgenic liver cancers with human liver cancers. RNA profiles from the three zebrafish tumors indicated relatively small overlaps of significantly deregulated genes and biological pathways. Nevertheless, the three transgenic tumor signatures all showed significant correlation with advanced or very advanced human hepatocellular carcinoma (HCC). Interestingly, molecular signature from each oncogene-induced zebrafish liver tumor correlated with only a small subset of human HCC samples (24–29%) and there were conserved up-regulated pathways between the zebrafish and correlated human HCC subgroup. The three zebrafish liver cancer models together represented nearly half (47.2%) of human HCCs while some human HCCs showed significant correlation with more than one signature defined from the three oncogene-addicted zebrafish tumors. In contrast, commonly deregulated genes (21 up and 16 down) in the three zebrafish tumor models generally showed accordant deregulation in the majority of human HCCs, suggesting that these genes might be more consistently deregulated in a broad range of human HCCs with different molecular mechanisms and thus serve as common diagnosis markers and therapeutic targets. Thus, these transgenic zebrafish models with well-defined oncogene-induced tumors are valuable tools for molecular classification of human HCCs and for understanding of molecular drivers in hepatocarcinogenesis in each human HCC subgroup.
TL;DR: In this article, the association between maternal solvent, paint, petroleum exposure, and smoking during pregnancy and risk of childhood acute lymphoblastic leukemia (ALL) was investigated by a meta-analysis.
Abstract: Background The prevalence of childhood leukemia is increasing rapidly all over the world. However, studies on maternal benzene exposure during pregnancy and childhood acute lymphoblastic leukemia (ALL) have not been systematically assessed. Therefore, we performed a meta-analysis to investigate the association between maternal solvent, paint, petroleum exposure, and smoking during pregnancy and risk of childhood ALL. Methods Relevant studies up to September 1st, 2013 were identified by searching the PubMed, EMBASE, Cochrane library and the Web of Science databases. The effects were pooled using either fixed or random effect models based on the heterogeneity of the studies. Results Twenty-eight case-control studies and one cohort study were included for analysis, with a total of 16,695 cases and 1,472,786 controls involved. Pooled odds ratio (OR) with 95% confidence interval (CI) for ALL was 1.25 (1.09, 1.45) for solvent, 1.23 (1.02, 1.47) for paint, 1.42 (1.10, 1.84) for petroleum exposure, and 0.99 (0.93, 1.06) for maternal smoking during pregnancy. No publication bias was found in this meta-analysis and consistent results were observed for subgroup and sensitivity analyses. Conclusions Childhood ALL was associated with maternal solvent, paint, and petroleum exposure during pregnancy. No association was found between ALL and maternal smoking during pregnancy. Avoidance of maternal occupational and environmental benzene exposure during pregnancy could contribute to a decrease in the risk of childhood ALL.
TL;DR: In this article, a facile and nontoxic one-pot hydrothermal method for synthesizing F-doped rutile single crystalline TiO2 with tuneable solar absorption was reported.
Abstract: In this work, we report a facile and nontoxic one-pot hydrothermal method for synthesizing F-doped rutile single crystalline TiO2 with tuneable solar absorption. The optical band gap of the catalyst can be easily manipulated from 3.05 to 2.58 eV via altering the initial F : Ti molar ratio of reaction precursors. The photoanodes made of rutile TiO2 single crystals with appropriate F-doping concentration show excellent photoelectrocatalytic activity towards water oxidation under ultraviolet and visible light illumination. The best photoelectrocatalytic performance under UV irradiation can be obtained by F-doped TiO2 with an initial F : Ti molar ratio of 0.1, which is almost 15 times higher than that of un-doped TiO2. Further, the F-doped TiO2 photoanodes also exhibit superior photoelectrocatalytic activity under visible irradiation, and the best performance can be achieved by F-doped TiO2 photoanode with an initial F : Ti molar ratio of 0.05. The superior photoelectrocatalytic activity could be attributed to the highly n-type dopant introduced by fluorine, which significantly tunes the electrical conductivities and band structures of the resulting TiO2 photoanodes, and thus the photoelectrocatalytic activities under both UV and visible irradiation. Different techniques have been employed to characterize the electrical conductivity, charge carrier density and band structures of the F-doped rutile TiO2 films, such as photoelectrochemical method, electrical impedance spectroscopy (EIS) measurements, Mott–Schottky plots and XPS valence band spectra.
TL;DR: The results showed that these luminescent polymeric nanoparticles with diameters of tens of nanometers showed high water dispersibility and strong fluorescence in aqueous solution and are biocompatible with A549 cells and promising for bioimaging applications.
Abstract: The development of novel fluorescent nanoprobes with remarkable optical properties, suitable particle size, high water dispersibility and good biocompatibility has recently attracted increasing interest for various biomedical applications. In this work, a novel type of luminescent polymeric nanoparticle based on polymerizable dyes with aggregation induced emission (AIE) properties and a zwitterionic monomer were prepared via reversible addition fragmentation chain transfer polymerization. Due to their amphiphilic properties, these copolymers could facilely self-assemble into AIE dye containing luminescent zwitterionic polymeric nanoparticles, which were characterized by a series of characterization techniques including transmission electronic microscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy and X-ray photoelectron spectroscopy. The results showed that these luminescent polymeric nanoparticles with diameters of tens of nanometers showed high water dispersibility and strong fluorescence in aqueous solution. To explore their potential for biomedical applications, biocompatibility and cell uptake behavior of these luminescent polymeric nanopartilces were further evaluated. We demonstrated that these polymeric nanoparticles are biocompatible with A549 cells and promising for bioimaging applications. Taken advantage of these merits of the AIE dye based zwitterionic polymeric nanoparticles, which could elegantly avoid the aggregation induced quenching of conventional organic dyes and nonbiodegradability of fluorescent inorganic nanoparticles, the ultrabright and biocompatible luminescent polymeric nanoparticles described in this work should be of highly potential for various biomedical applications.
TL;DR: In this paper, the effects of a modern cultivation system of plastic film mulching with drip irrigation on soil greenhouse gas fluxes, methane (CH4) and nitrous oxide (N2O) fluxes were quantified and contrasted in an MD system and a traditional system of mulch-free flood-irrigated (MFF) cotton (Gossypium hirsutum L.) in fields of northwest China.
Abstract: To evaluate the effects of a modern cultivation system of plastic film mulching with drip irrigation (MD) on soil greenhouse gas fluxes, methane (CH4) and nitrous oxide (N2O) fluxes were quantified and contrasted in an MD system and a traditional system of mulch-free flood-irrigated (MFF) cotton (Gossypium hirsutum L.) in fields of northwest China. The results showed that soil N2O flux and the absorption rate of CH4 were lower in the MD than the MFF sites. A possible reason for the higher CH4 emissions at MD sites was that the relatively low gaseous oxygen (O2) availability and high ammonium (NH4+) content in the MD soil increased CH4 generation by methanogens and decreased CH4 oxidation by methanotrophs. The lower N2O in the MD sites may be due to an increase of soil denitrification by Thiobacillus denitrificans that reduced some nitrous compounds further into nitrogen gas (N2). Taking into account the global warming potentials of CH4 and N2O in a 100-year time horizon, during the entire growth period, the contribution of CH4 to the greenhouse effect was significantly lower than N2O in these two treatments. Considering these two greenhouse gas fluxes together, a transition from non-mulching cultivation to mulching cultivation could reduce atmospheric emissions by c. 20 g CO2 e m2/season. Based on these findings and previous studies, it can be concluded that mulched-drip irrigation cultivation is a good way to decrease the emission of greenhouse gases and reduce the global warming impact of arid farmlands.
TL;DR: In this paper, the authors provide a comprehensive discussion on the development of the graphene materials-based energy acceptor systems and sensors, sorting the sensors according to the probes with which the energy acceptors are assembled to or conjugated with the luminescent energy donors.
Abstract: Graphene materials have recently attracted considerable attention because of its extraordinary mechanical, electronic, thermal and optical properties, leading to the wide application of graphene such as in biology and energy areas. In recent years, energy-transfer based optical biosensors using graphene materials as the energy acceptors have become the focus of researches, which take the advantages of the high surface area and ultrahigh luminescence quenching efficiency of graphene materials. These sensors have extensively covered the detection of DNA, protein, enzyme activity, metal ions and other small molecules. In this review article, we aim to provide a comprehensive discussion on the development of the graphene materials-based energy acceptor systems and sensors, sorting the sensors according to the probes with which the energy acceptors are assembled to or conjugated with the luminescent energy donors. At the end we also present an overview of future perspective and possible challenges in this rapidly developing area.