To realize graphene-based electronics, various types of graphene are required; thus, modulation of its electrical properties is of great importance. Theoretic studies show that intentional doping is a promising route for this goal, and the doped graphene might promise fascinating properties and widespread applications. However, there is no experimental example and electrical testing of the substitutionally doped graphene up to date. Here, we synthesize the N-doped graphene by a chemical vapor deposition (CVD) method. We find that most of them are few-layer graphene, although single-layer graphene can be occasionally detected. As doping accompanies with the recombination of carbon atoms into graphene in the CVD process, N atoms can be substitutionally doped into the graphene lattice, which is hard to realize by other synthetic methods. Electrical measurements show that the N-doped graphene exhibits an n-type behavior, indicating substitutional doping can effectively modulate the electrical properties of graphene. Our finding provides a new experimental instance of graphene and would promote the research and applications of graphene.

Graphene and graphene oxide have attracted tremendous interest over the past decade due to their unique and excellent electronic, optical, mechanical, and chemical properties.

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A microscopic understanding of the growth mechanism of two-dimensional materials is of particular importance for controllable synthesis of functional nanostructures. Because of the lack of direct and insightful observations, how to control the orientation and the size of two-dimensional material grains is still under debate. Here we discern distinct formation stages for MoS2 flakes from the thermolysis of ammonium thiomolybdates using in situ transmission electron microscopy. In the initial stage (400 °C), vertically aligned MoS2 structures grow in a layer-by-layer mode. With the increasing temperature of up to 780 °C, the orientation of MoS2 structures becomes horizontal. When the growth temperature reaches 850 °C, the crystalline size of MoS2 increases by merging adjacent flakes. Our study shows direct observations of MoS2 growth as the temperature evolves, and sheds light on the controllable orientation and grain size of two-dimensional materials.

A series of peapod‐like composites with component‐controllable Co(SxSe1−x)2 nanoparticles encapsulated in porous carbon fibers is fabricated by Yu Wang and co‐workers in article number https://doi.org/10.1002/adfm.201701008. The peapod‐like structure exhibits increased exposure of active sites and improved charge and mass transport capability in electrolysis. The optimized composition Co(S0.71Se0.29)2∥Co(S0.22Se0.78)2 demonstrates a durable catalytic activity for overall water splitting.

Here we present the synthesis of core-shell structured hexagonal-phase NaYF 4 : Yb 3+ ,Er 3+ @Ag nanoparticles (NPs) and their unique bio-functional properties. The structure and morphology of the NPs are confirmed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) measurements. They displayed both strong 2 H 11/2 / 4 S 3/2 -4 I 15/2 (green) and 4 F 9/2 -4 I 15/2 (red) upconversion luminescence (UCL) and photothermal transfer properties under the excitation of a continuous 980 nm laser diode. Furthermore, the UCL intensity ratio of 2 H 11/2 -4 I 15/2 to 4 S 3/2 -4 I 15/2 acted as a temperature sensor due to the low energy gap between 2 H 11/2 and 4 S 3/2 ($740 cm À1 ). After coating with the silver shell, the cytotoxicity of the composite NPs was reduced largely in contrast to the pure NaYF 4 : Yb 3+ ,Er 3+ NPs. HepG2 cells from human hepatic cancer and BCap-37 cells from human breast cancer incubated with the composite NPs in vitro were found to undergo photothermally induced death on exposure to 980 nm NIR light, and the optimum mortality approaches 95% with a power density of 1.5 W cm À2 which is much lower than that reported for Au nanoshells and Au nanorods. Overall, this class of core/shell NPs is expected to be an attractive therapeutic agent for tumor ablation with bioimaging and thermal detection in real time.

lowest energy density. [4][5][6] To improve this, much attention has been particularly paid to antiferroelectric ceramics such as PZ, [ 7,8 ] PLZT, [ 9,10 ] PZN-PMN-PT, [ 4 ] PLZST, [ 4 ] etc., since they normally have higher energy density than ferroelectric and paraelectric ceramics at comparable electric fi eld. [ 2 ] The energy density in bulk ceramics is usually less than 1 J cm −3 because of the limitation of low dielectric breakdown strength (<100 kV cm −1 ). [ 11,12 ] With the development of high-quality thin fi lms by sol-gel, pulsed laser deposition (PLD), molecular beam epitaxy, etc., large energy density, mainly in lead-based antiferroelectric thin fi lms, has been achieved due to the higher dielectric breakdown strength (>500 kV cm −1 ). [ 3,9,13,14 ] For example, a high energy density of 53 J cm −3 at 3500 kV cm −1 was obtained in relaxor antiferroelectric (Pb 0.92 La 0.08 )(Zr 0.9 Ti 0.05 ) O 3 sol-gel thin fi lm. [ 9 ] However, widespread applications of lead-based materials are prohibited due to the toxicity of lead. As a lead-free dielectric material, poly(vinylidene fl uoride) (PVDF)-based polymer was also widely studied and a high energy density of 27 J cm −3 at 8000 kV cm −1 was reported. [ 1,4 ] However, its lifetime and reliability are seriously impaired at the maximum operating temperature (typically less than 85 °C), seriously limiting its applications as capacitors.Ferroelectrics/antiferroelectrics with high dielectric breakdown strength have the potential to store a great amount of electrical energy, attractive for many modern applications in electronic devices and systems. Here, it is demonstrated that a giant electric energy density (154 J cm −3 , three times the highest value of lead-based systems and fi ve times the value of the best dielectric/ ferroelectric polymer), together with the excellent fatigue-free property, good thermal stability, and high effi ciency, is realized in pulsed laser deposited (Bi 1/2 Na 1/2 ) 0.9118 La 0.02 Ba 0.0582 (Ti 0.97 Zr 0.03 )O 3 (BNLBTZ) epitaxial lead-free relaxor thin fi lms with the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases. This is endowed by high epitaxial quality, great relaxor dispersion, and the coexistence of the FE/AFE phases near the morphotropic phase boundary. The giant energy storage effect of the BNLBTZ lead-free relaxor thin fi lms may make a great impact on the modern energy storage technology.

Selective dissolution is a common corrosion process in dealloying in which an alloy is immersed in acid to remove the active element, leaving behind an inert constituent. We introduce this technique into the treatment of oxide catalysts. A three-dimensionally ordered macroporous LaMnO3 perovskite has been prepared and treated with diluted HNO3 to selectively remove La cations, acquiring a novel γ-MnO2-like material. LaMnO3 is not a satisfactory catalyst on CO oxidation. Upon the removal of La cations, the obtained sample showed a significantly higher CO oxidation catalytic activity (T50=89 °C) than the initial precursor LaMnO3 (T50=237 °C) and ordinary γ-MnO2 (T50=148 °C). A large surface area, a high degree of mesoporosity, excellent low-temperature reducibility, and especially improved surface oxygen species are deduced to be responsible for CO oxidation at lower temperatures.