We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

0D/2D heterojunctions, especially quantum dots (QDs)/nanosheets (NSs) have attracted significant attention for use of photoexcited electrons/holes due to their high charge mobility. Herein, unprecedent heterojunctions of vanadate (AgVO3 , BiVO4 , InVO4 and CuV2 O6 ) QDs/graphitic carbon nitride (g-C3 N4 ) NSs exhibiting multiple unique advances beyond traditional 0D/2D composites have been developed. The photoactive contribution, up-conversion absorption, and nitrogen coordinating sites of g-C3 N4 NSs, highly dispersed vanadate nanocrystals, as well as the strong coupling and band alignment between them lead to superior visible-light-driven photoelectrochemical (PEC) and photocatalytic performance, competing with the best reported photocatalysts. This work is expected to provide a new concept to construct multifunctional 0D/2D nanocomposites for a large variety of opto-electronic applications, not limited in photocatalysis.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.201611127

0D/2D Heterojunctions of Vanadate Quantum Dots/Graphitic Carbon Nitride Nanosheets for Enhanced Visible-Light-Driven Photocatalysis.

Potassium-ion batteries (PIBs) are a promising alternative to lithium-ion batteries because potassium is an abundant natural resource. To date, PIBs are in the early stages of exploration and only a few anode materials have been investigated. This study reports a cobalt sulfide and graphene (CoS@G) composite as anode electrode for PIBs for the first time. The composite features interconnect quantum dots of CoS nanoclusters uniformly anchored on graphene nanosheets. The coexistence of CoS quantum dot nanoclusters and graphene nanosheets endows the composite with large surface area, highly conductive network, robust structural stability, and excellent electrochemical energy storage performance. An unprecedented capacity of 310.8 mA h g−1 at 500 mA g−1 is obtained after 100 cycles, with a rate capability better than an equivalent sodium-ion batteries (SIBs). This work provides the evidence that PIBs can be a promising alternative to SIBs, especially at high charge–discharge rates. The development of the CoS@G anode material also provides the basis of expanding the library of suitable anode materials for PIBs.

/pdf/cos-quantum-dot-nanoclusters-for-high-energy-potassium-ion-4njmo8iqd0.pdf

CoS Quantum Dot Nanoclusters for High-Energy Potassium-Ion Batteries

We have produced ultrathin epitaxial graphite films which show remarkable 2D electron gas (2DEG) behavior. The films, composed of typically 3 graphene sheets, were grown by thermal decomposition on the (0001) surface of 6H-SiC, and characterized by surface-science techniques. The low-temperature conductance spans a range of localization regimes according to the structural state (square resistance 1.5 kOhm to 225 kOhm at 4 K, with positive magnetoconductance). Low resistance samples show characteristics of weak-localization in two dimensions, from which we estimate elastic and inelastic mean free paths. At low field, the Hall resistance is linear up to 4.5 T, which is well-explained by n-type carriers of density 10^{12} cm^{-2} per graphene sheet. The most highly-ordered sample exhibits Shubnikov - de Haas oscillations which correspond to nonlinearities observed in the Hall resistance, indicating a potential new quantum Hall system. We show that the high-mobility films can be patterned via conventional lithographic techniques, and we demonstrate modulation of the film conductance using a top-gate electrode. These key elements suggest electronic device applications based on nano-patterned epitaxial graphene (NPEG), with the potential for large-scale integration.

Ultrathin epitaxial graphite: 2D electron gas properties and a route toward graphene-based nanoelectronics

A facile and cost-efficient hydrothermal and lyophilization two-step strategy has been developed to prepare three-dimensional (3D) SnO2/rGO composites as NO2 gas sensor. In the present study, two different metal salt precursors (Sn2+ and Sn4+) were used to prepare the 3D porous composites. It was found that the products prepared from different tin salts exhibited different sensing performance for NO2 detection. The scanning electron microscopy and transmission electron microscopy characterizations clearly show the macroporous 3D hybrids, nanoporous structure of reduce graphene oxide (rGO), and the supported SnO2 nanocrystals with an average size of 2–7 nm. The specific surface area and porosity properties of the 3D mesoporous composites were analyzed by Braunauer–Emmett–Teller method. The results showed that the SnO2/rGO composite synthesized from Sn4+ precursor (SnO2/rGO-4) has large surface area (441.9 m2/g), which is beneficial for its application as a gas sensing material. The gas sensing platform fab...

Three-dimensional mesoporous graphene aerogel-supported SnO2 nanocrystals for high-performance NO2 gas sensing at low temperature.

Nanocomposites have significant potential in the development of advanced materials for numerous applications. Tin dioxide (SnO2) is a functional material with wide-ranging prospects because of its high electronic mobility and wide band gap. Graphene as the basic plane of graphite is a single atomic layer two-dimensional sp(2) hybridized carbon material. Both have excellent physical and chemical properties. Here, SnO2 quantum dots/graphene composites have been successfully fabricated by a facile ultrasonic method. The experimental investigations indicated that the graphene was exfoliated and decorated with SnO2 quantum dots, which was dispersed uniformly on both sides of the graphene. The size distribution of SnO2 quantum dots was estimated to be ranging from 4 to 6 nm and their average size was calculated to be about 4.8 ± 0.2 nm. This facile ultrasonic route demonstrated that the loading of SnO2 quantum dots was an effective way to prevent graphene nanosheets from being restacked during the reduction. During the calcination process, the graphene nanosheets distributed between SnO2 nanoparticles have also prevented the agglomeration of SnO2 nanoparticles, which were beneficial to the formation of SnO2 quantum dots.

Assembling tin dioxide quantum dots to graphene nanosheets by a facile ultrasonic route.

A novel organic–inorganic hybrid 2D molecular space with regular triphenylphosphine groups (triphenylphosphineamidephenylsilica, PPh3APhS) was successfully synthesized through grafting triphenylphosphine groups in the 2D structure of layered aminophenylsilica dodecyl sulfate (APhTMS-DS), which was developed in our previous research, with regular ammonium groups. The 2D structures were kept after the grafting reaction of triphenylphosphine groups in PPh3APhS. The catalytic potentials of 2D molecular space with regular triphenylphosphine groups were investigated. An unusual catalytic effect was found in a carbon–phosphorus ylide reaction. The PPh3-catalyzed reaction of modified allylic compounds, including bromides and chlorides with tropone yielded a [3 + 6] annulation product. However, an unusual [8 + 3] cycloadduct was obtained in the reaction of modified allylic compounds, including bromides and chlorides with tropone catalyzed by PPh3APhS. Otherwise, the stable catalytic intermediate was successfully s...

Unusual catalytic effect of the two-dimensional molecular space with regular triphenylphosphine groups.

Tin oxide is a unique material of widespread technological applications, particularly in the field of strategic functional materials. Versatile strategies for growth of tin dioxide nanocrystals are...

Electron-Beam Irradiation Strategies for Growth Behavior of Tin Dioxide Nanocrystals

Synthesis method of trimanganese tetroxide material with 3D (three-dimensional) flower-shaped structure

An integrated device or component for the semiconductor industry is highly desirable for versatile advanced applications. Group IV semiconductors such as germanium (Ge) and silicon (Si) are unique materials of widespread technological applications, particularly in the field of microelectronic devices and optoelectronic components. Herein, Pd/Ge bilayer films with interesting Ge clusters, which have noninteger dimensions and are called fractals, were successfully prepared by high-vacuum thermal evaporation techniques. It was found that Ge nanocrystals embedded in Pd matrix showed fascinating fractal morphologies with average size of fractal clusters at 680 nm and fractal dimension at 1.708 when the films were annealed at 350 °C for 30 min. The fractal clusters consisted of Ge nanocrystals with diameters ranging from 25 to 55 nm. Third-order optical nonlinearities of the annealed Pd/Ge bilayer films were investigated in detail by Z-scan techniques using a femtosecond laser. Experimental results indicated th...

Chen Chen

Papers

Assembling tin dioxide quantum dots to graphene nanosheets by a facile ultrasonic route.

Unusual catalytic effect of the two-dimensional molecular space with regular triphenylphosphine groups.

Electron-Beam Irradiation Strategies for Growth Behavior of Tin Dioxide Nanocrystals

Synthesis method of trimanganese tetroxide material with 3D (three-dimensional) flower-shaped structure

Morphologies and nonlinear optical properties of fractal Ge nanocrystals embedded in Pd matrix