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Elucidating the synergistic catalytic mechanism between multiple active centers is of great significance for heterogeneous catalysis; however, finding the corresponding experimental evidence remains challenging owing to the complexity of catalyst structures and interface environment. Here we construct an asymmetric TeN2–CuN3 double-atomic site catalyst, which is analyzed via full-range synchrotron pair distribution function. In electrochemical CO2 reduction, the catalyst features a synergistic mechanism with the double-atomic site activating two key molecules: operando spectroscopy confirms that the Te center activates CO2, and the Cu center helps to dissociate H2O. The experimental and theoretical results reveal that the TeN2–CuN3 could cooperatively lower the energy barriers for the rate-determining step, promoting proton transfer kinetics. Therefore, the TeN2–CuN3 displays a broad potential range with high CO selectivity, improved kinetics and good stability. This work presents synthesis and characterization strategies for double-atomic site catalysts, and experimentally unveils the underpinning mechanism of synergistic catalysis. Elucidating the synergistic catalytic mechanism involving multiple active centers is of great significance for heterogeneous catalysis. Here the authors construct an asymmetric TeN2–CuN3 double atomic site catalyst featuring synergistic CO2 activation and H2O dissociation for CO2 electroreduction. [ABSTRACT FROM AUTHOR]

For heterogeneous catalysts, the active sites exposed on the surface have been investigated intensively, yet the effect of the subsurface‐underlying atoms is much less scrutinized. Here, a surface‐engineering strategy to dope Ru into the subsurface/surface of Co matrix is reported, which alters the electronic structure and lattice strain of the catalyst surface. Using hydrogen evolution (HER) as a model reaction, it is found that the subsurface doping Ru can optimize the hydrogen adsorption energy and improve the catalytic performance, with overpotentials of 28 and 45 mV at 10 mA cm−2 in alkaline and acidic media, respectively, and in particular, 28 mV in neutral electrolyte. The experimental results and theoretical calculations indicate that the subsurface/surface doping Ru improves the HER efficiency in terms of both thermodynamics and kinetics. The approach here stands as an effective strategy for catalyst design via subsurface engineering at the atomic level. [ABSTRACT FROM AUTHOR]

Hollow nanomaterials consisting of non‐noble metal oxides have wide applications in catalysis, and many preparation methods for this kind of structures are established. However, it is still challenging to fabricate non‐noble‐metal hollow structures featuring high crystallinity, regular polyhedral morphologies, and small sizes, owing to their relatively low chemical stability and the stringent hollowing conditions. Here in this work, an optimized self‐templating synthesis method with refined control over the heating program and solution environment, which can alleviate the common issues of morphology and crystallinity degradation from precursors during hollowing process, is reported. Through this method, highly crystalline Cu2O nanobox with sizes below 50 nm is successfully prepared. Benefiting from the unique hollow structures, the Cu2O nanobox/C catalyst gives outstanding performances in catalyzing the oxidative homocoupling of phenylacetylene, with the advantages of lower metal loading, mild reaction conditions, and no additives. This optimized method can be extended to the preparation of other non‐noble‐metal hollow materials with sophisticated architectures. [ABSTRACT FROM AUTHOR]

In the past few decades, polymer solar cells (PSCs) have been intensively investigated in academic fields. The study of non-fullerene polymer acceptors has become a hot research focus due to their excellent opto-electronic properties such as wide light-absorbing ability, appropriate molecular energy levels, and easy chemical modifications. The much higher power conversion efficiencies (PCEs) of non-fullerene PSCs relative to fullerene PSCs revealed the significant potential of non-fullerene acceptors in PSCs. This review systematically summarizes the recent advancements of efficient polymer acceptors, including perylene diimide-based, naphthalene diimide-based, diketopyrrolopyrrole-based, double B←N bridged bipyridyl-based, and other polymer acceptors. Their structure–property relationships were thoroughly analyzed and summarized, which may provide new guidance for the rational structural design of high-performance photovoltaic materials. [ABSTRACT FROM AUTHOR]

In this paper, uniform NaGdF4:Yb3+, Er3+ nanorods doped with Fe3+ were synthesized by a facile hydrothermal method. The prepared NaGdF4:Yb3+, Er3+ doped with Fe3+ displayed hexagonal phase structure from XRD pattern and uniform nanorods with narrow size distribution from TEM. The signal of Fe3+ is accompanied with the Yb3+ and Er3+ from EDX line-scanning, which was confirmed that Fe3+ was doped successfully. The NaGdF4:Yb3+, Er3+ nanorods doped with Fe3+ show absorption of near-infrared region from UV–Vis absorption spectra. The upconversion luminescence intensity enhances with increasing content of Fe3+ under 980 nm excitation. When stoichiometric ratio of Fe3+ is 20 mol%, the strongest upconversion emission intensity could be obtained. But the upconversion luminescence would become weak when the stoichiometric ratio of Fe3+ is above 20 mol%. Based on above analysis, it is inferred that there is energy conversion between Fe3+ and rare earth ions by the luminescence mechanism. In this work, it provides a facile method for preparation of NaGdF4:Yb3+, Er3+ nanorods, which displays improving upconversion luminescence by Fe3+ doping. [ABSTRACT FROM AUTHOR]

The well-defined NaGdF4:Yb,Er nanorods (NRs) with various aspect ratios were synthesized using a facile hydrothermal method. The morphology and crystal phase of NRs could be controlled by reaction conditions. NaGdF4:Yb,Er NRs with various aspect ratios could be synthesized and their upconversion (UC) luminescence was tuned. It is displayed that the NRs with aspect ratios about 5 exhibited the strongest UC luminescence among samples. The growth mechanism and morphology transition of NRs had been deduced by schematic diagram. And UC mechanism had been determined by energy level diagrams. Compared with previous reports, the work provided a facial method for UCNRs with various aspect ratios at lower temperature. NaGdF4:Yb,Er nanorods (NRs) with various aspect ratios were synthesized using a facile hydrothermal method at lower temperature. The upconversion luminescence of various aspect ratios was studied, and the NRs with aspect ratio of about 5 exhibited the strongest luminescence among the samples. Both the growth mechanism and upconversion mechanism of NRs had been deduced by schematic diagram. [ABSTRACT FROM AUTHOR]

Ferromagnetic resonance (FMR) is one of the most important characteristics of soft magnetic materials, which practically sets the maximum operation speed of these materials. There are two FMR modes in exchange coupled ferromagnet/nonmagnet/ferromagnet sandwich films. The acoustic mode has relatively lower frequency and is widely used in radio-frequency/microwave devices, while the optical mode is largely neglected due to its tiny permeability even though it supports much higher frequency. Here, a realistic method is reported to enhance the permeability in the optical mode to an applicable level. FeCoB/Ru/FeCoB trilayers are carefully engineered with both uniaxial magnetic anisotropy and antiferromagnetic interlayer exchange coupling. This special magnetic structure exhibits a high optical mode frequency up to 11.28 GHz and a maximum permeability of 200 at resonance. An abnormally low inverse switch field (<200 Oe, less than 1/5 of the single layer) is observed which can effectively switch the system from optical mode with higher frequency into acoustic mode with lower frequency. The optical mode frequency and inverse switch field can be controlled by tailoring the interlayer coupling strengths and the uniaxial anisotropy fields, respectively. The tunable optical mode resonance thus can increase operation frequency while reduce operation field overhead in FMR based devices. [ABSTRACT FROM AUTHOR]

In this article, diblock copolymer (DBC), poly (methyl methacrylate)-block-poly (acrylic acid) was synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT). The DBC-Eu3+solid micelles were prepared through the complex interaction between DBC and Eu3+ions. As cross-linker, Eu3+ions accept the electron donation of the ligand groups (carboxyl) sited on the polar PAA segments of DBC and form the DBC-Eu3+solid micelles. The observations by transmission electron microscopy showed the embedment of Eu3+ions in DBC and the nonpolar segments [poly (methyl methacrylate)] of DBC play a role of compatible agent for DBC-Eu3+solid micelles to disperse in hydrophobic solvent [for example, dimethyl formamide] or polymer matrix. Very importantly, we found the dependence of the morphological structure (i.e. the size of solid micelles) on the molecular weight of DBC. On the other hand, the dependence of photoluminescent property of DBC-Eu3+solid micelles on the molecular weight of DBC and the ratio of polar and nonpolar segments was confirmed through our experiments. The results showed the existence of enhanced photoluminescent property of DBC-Eu3+solid micelles. [ABSTRACT FROM PUBLISHER]

Graphical abstract [ABSTRACT FROM AUTHOR]

Flexible lithium-ion batteries (LIBs) have recently attracted increasing attention with the fast development of bendable electronic systems. Herein, a facile and templatefree solvothermal method is presented for the fabrication of hybrid yolk-shell CoS2 and nitrogen-doped graphene (NG) sheets. The yolk-shell architecture of CoS2 encapsulated with NG coating is designed for the dual protection of CoS2 to address the structural and interfacial stability concerns facing the CoS2 anode. The as-prepared composite can be assembled into a film, which can be used as a binder-free and flexible electrode for LIBs that does not require any carbon black conducting additives or current collectors. When evaluating lithium-storage properties, such a flexible electrode exhibits a high specific capacity of 992 mAh g-1 in the first reversible discharge capacity at a current rate of 100 mA g-1 and high reversible capacity of 882 mAh g-1 after 150 cycles with excellent capacity retention of 89.91 %. Furthermore, a reversible capacity as high as 655 mAh g-1 is still achieved after 50 cycles even at a high rate of 5 C due to the yolk-shell structure and NG coating, which not only provide short Li-ion and electron pathways, but also accommodate large volume variation. [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, novel antistatic isotactic polypropylene (iPP) fibers were prepared through adding ternary polymer water-absorbing nanospheres (TPWANs) into iPP melt in melt spinning process. The TPWANs were synthesized through emulsion copolymerization of styrene (St), butyl acrylate (BA), and sodium allylsulfonate (SAS). The characterization results of Fourier transform infrared spectrometer (FT-IR) and 1H nuclear magnetic resonance (1H NMR) confirmed the ternary components in this copolymer. Transmission electron microscopy (TEM) images indicated the nanospherical shape of TPWANs with the characteristics of 80-90 nm size range of diameter and good dispersion in iPP fibers. The volume resistance of iPP fibers decreased by three orders from 1012 to 109 Ω cm when the 6 wt % TPWANs was added into iPP fibers, indicating that the blend fibers have good antistatic property. Most importantly, the nanospherical structure of TPWANs imparts both the compatibility and antistatic property into the blend iPP fibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40568. [ABSTRACT FROM AUTHOR]

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber (NR) was carried out by supercritical carbon dioxide (scCO2) swelling polymerization with benzoyl peroxide (BPO) as an initiator. Fourier transform-infrared spectroscopy (FT-IR) was used to confirm the formation of graft copolymers with the characteristic bands of symmetric CO and COC stretching vibrations at 1728 cm−1 and 1147 cm−1, respectively. The effects of the rubber-to-monomer ratio, amount of initiator, reaction time, and pressure on the monomer grafting level (GL) and grafting efficiency (GE) were investigated, and the optimum conditions for the preparation of NR-g-MMA were found to be 70:30 of the rubber-to-monomer ratio, 1.2% of the initiator content, and the reaction pressure of 23 MPa for 6 h. The thermal behavior of the NR and the different NR/MMA molar ratio grafted copolymer samples was studied by differential scanning calorimetry (DSC). The observed glass transition temperature ( Tg) was consistent with the GL. The tensile strength, modulus of elasticity, elongation at break, hardness, and oil resistance of graft copolymers were determined and compared with the values of NR and that of polymerization products prepared in traditional toluene solution. The results showed that the tensile strength, modulus of elasticity, hardness and oil resistance were greatly improved after modification in scCO2. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Sn4+-doped FeS2 cubes with high yield thin films have been successfully synthesized on FTO glass through a simple hydrothermal process. The Sn4+-doped FeS2 cubes are single crystalline in cubic structure with (200) facet as the main exposed surface. The formation process was investigated. Sn2+ was found to play an important role during the formation process of FeS2 growing on FTO glass. The direct optical band gap value can be estimated to be 1.71eV which is much larger than that of bulk FeS2 due to the Sn4+ doping. The photoelectrochemical properties of the Sn4+-doped FeS2 films were studied as well. There is a significant increase in photocurrent of Sn4+-doped FeS2 electrode compared to that of undoped sample. [Copyright &y& Elsevier]