Hui Ying Yang

Hydrogen‐Bonded Supramolecular Conjugated Polymer Nanoparticles for White Light‐Emitting Devices

Supramolecular polyfluorenol enable assembly into conjugated polymer nanoparticles (CPNs). Poly{9-[4-(octyloxy)phenyl]fluoren-9-ol-2,7-diyl} (PPFOH)-based supramolecular nanoparticles are prepared via reprecipitation. PPFOH nanoparticles with diameters ranging from 40 to 200 nm are obtained by adding different amounts of water into DMF solution. Size-dependent luminescence is observed in PPFOH-based hydrogen-bonded nanoparticles that is different from that of poly(9,9-dioctylfluorenes). Finally, white light-emitting devices using CPNs with a size of 80 nm exhibit white emission with the CIE coordinates (0.31, 0.34). Amphiphilic conjugated polymer nanoparticles are potential organic nano-inks for the fabrication of organic devices in printed electronics.

van der Waals Epitaxy of MoS2 Layers Using Graphene As Growth Templates

We present a method for synthesizing MoS(2)/Graphene hybrid heterostructures with a growth template of graphene-covered Cu foil. Compared to other recent reports, (1, 2) a much lower growth temperature of 400 °C is required for this procedure. The chemical vapor deposition of MoS(2) on the graphene surface gives rise to single crystalline hexagonal flakes with a typical lateral size ranging from several hundred nanometers to several micrometers. The precursor (ammonium thiomolybdate) together with solvent was transported to graphene surface by a carrier gas at room temperature, which was then followed by post annealing. At an elevated temperature, the precursor self-assembles to form MoS(2) flakes epitaxially on the graphene surface via thermal decomposition. With higher amount of precursor delivered onto the graphene surface, a continuous MoS(2) film on graphene can be obtained. This simple chemical vapor deposition method provides a unique approach for the synthesis of graphene heterostructures and surface functionalization of graphene. The synthesized two-dimensional MoS(2)/Graphene hybrids possess great potential toward the development of new optical and electronic devices as well as a wide variety of newly synthesizable compounds for catalysts.

Selective decoration of Au nanoparticles on monolayer MoS2 single crystals.

We report a controllable wet method for effective decoration of 2-dimensional (2D) molybdenum disulfide (MoS2) layers with Au nanoparticles (NPs). Au NPs can be selectively formed on the edge sites or defective sites of MoS2 layers. The Au-MoS2 nano-composites are formed by non-covalent bond. The size distribution, morphology and density of the metal nanoparticles can be tuned by changing the defect density in MoS2 layers. Field effect transistors were directly fabricated by placing ion gel gate dielectrics on Au-decorated MoS2 layers without the need to transfer these MoS2 layers to SiO2/Si substrates for bottom gate devices. The ion gel method allows probing the intrinsic electrical properties of the as-grown and Au-decorated MoS2 layers. This study shows that Au NPs impose remarkable p-doping effects to the MoS2 transistors without degrading their electrical characteristics.

Self-assembly of hierarchical MoSx/CNT nanocomposites (2<x<3): towards high performance anode materials for lithium ion batteries.

Two dimension (2D) layered molybdenum disulfide (MoS2) has emerged as a promising candidate for the anode material in lithium ion batteries (LIBs). Herein, 2D MoSx (2 ≤ x ≤ 3) nanosheet-coated 1D multiwall carbon nanotubes (MWNTs) nanocomposites with hierarchical architecture were synthesized via a high-throughput solvent thermal method under low temperature at 200°C. The unique hierarchical nanostructures with MWNTs backbone and nanosheets of MoSx have significantly promoted the electrode performance in LIBs. Every single MoSx nanosheet interconnect to MWNTs centers with maximized exposed electrochemical active sites, which significantly enhance ion diffusion efficiency and accommodate volume expansion during the electrochemical reaction. A remarkably high specific capacity (i.e., > 1000 mAh/g) was achieved at the current density of 50 mA g−1, which is much higher than theoretical numbers for either MWNTs or MoS2 along (~372 and ~670 mAh/g, respectively). We anticipate 2D nanosheets/1D MWNTs nanocomposites will be promising materials in new generation practical LIBs.

Functionalized MoS 2 Nanosheet-Based Field-Effect Biosensor for Label-Free Sensitive Detection of Cancer Marker Proteins in Solution

Label-free MoS(2) nanosheet-based field-effect biosensor detects cancer marker protein Prostate Specific Antigen in real time with high sensitivity and selectivity, exhibiting great potential in point-of-care diagnostics application.

Three-Dimensional NiCo2O4@Polypyrrole Coaxial Nanowire Arrays on Carbon Textiles for High-Performance Flexible Asymmetric Solid-State Supercapacitor

In this article, we report a novel electrode of NiCo2O4 nanowire arrays (NWAs) on carbon textiles with a polypyrrole (PPy) nanosphere shell layer to enhance the pseudocapacitive performance. The merits of highly conductive PPy and short ion transport channels in ordered NiCo2O4 mesoporous nanowire arrays together with the synergistic effect between NiCo2O4 and PPy result in a high specific capacitance of 2244 F g(-1), excellent rate capability, and cycling stability in NiCo2O4/PPy electrode. Moreover, a lightweight and flexible asymmetric supercapacitor (ASC) device is successfully assembled using the hybrid NiCo2O4@PPy NWAs and activated carbon (AC) as electrodes, achieving high energy density (58.8 W h kg(-1) at 365 W kg(-1)), outstanding power density (10.2 kW kg(-1) at 28.4 W h kg(-1)) and excellent cycling stability (∼89.2% retention after 5000 cycles), as well as high flexibility. The three-dimensional coaxial architecture design opens up new opportunities to fabricate a high-performance flexible supercapacitor for future portable and wearable electronic devices.

Three-dimensional Co3O4@C@Ni3S2 sandwich-structured nanoneedle arrays: towards high-performance flexible all-solid-state asymmetric supercapacitors

In this paper, we report the design and fabrication of a novel hierarchical Co3O4@C@Ni3S2 sandwich-structured nanoneedle array (NNA) electrode for supercapacitor application. The supercapacitor performance based on Co3O4@C@Ni3S2 NNA electrodes is investigated in detail. A lightweight and flexible asymmetric supercapacitor (ASC) is successfully fabricated using Co3O4@C@Ni3S2 NNAs as the positive electrode and activated carbon (AC) as the negative electrode, which delivers an output voltage of 1.8 V and high energy/power density (1.52 mW h cm−3 at 6 W cm−3 and 0.920 mW h cm−3 at 60 W cm−3), as well as remarkable cycling stability (∼91.43% capacitance retention after 10 000 cycles), owing to the unique 3D porous sandwich-structured nanoneedle array architecture and a rational combination of the three electrochemically active materials. As a result, the ternary hybrid architectural design demonstrated in this study provides a new approach to fabricate high-performance metal oxide/sulfide composite nanostructure arrays for next-generation energy storage devices.

Hierarchical porous carbon nanosheets and their favorable high-rate performance in lithium ion batteries

Novel hierarchical porous carbon nanosheets (HPCS) with quantities of micropores and mesopores were prepared on a large-scale by using thermoplastic phenolic formaldehyde resin as the carbon source and copper nitrate as the template precursor. The HPCS, possessing a thickness of about 40 nm and the width of several microns, exhibited a high specific capacity and favorable high-rate performance when used as an anode material for lithium ion batteries (LIBs). The reversible capacities were 748 mA h g−1 at a current density of 20 mA g−1 and 460 mA h g−1 even at 1 A g−1, which were much higher than those of traditional porous carbon materials. It also showed superior cyclical stability for only 0.3% capacity loss per cycle under high rate charge-discharge process, suggesting that HPCS should be a promising candidate for anode materials in high-rate LIBs. The roles of various-sized pores in HPCS in Li storage were discussed briefly.

Direct Growth of ZnO Nanocrystals onto the Surface of Porous TiO2 Nanotube Arrays for Highly Efficient and Recyclable Photocatalysts

Recently, extensive investigations have been concentrated on the design and synthesis of nanocompositemetal oxides such as ZnO/TiO2 nanocomposite materials to improve the quantum efficiency of photocatalysts for applications in water purification. This is due to the high reactivity of TiO2 and the large binding energy of ZnO, which improve the process of electron and hole transfer between the corresponding conduction and valence bands. As a result, a better separation of photogenerated carriers can be achieved when compared with catalysts from a single metal oxide. A double-layered ZnO/TiO2 system had been proposed to improve thequantumefficiencyofphotocatalysts, however, the photogenerated electrons accumulated in the TiO2 underlayer may be unavailable to participate in the photocatalytic reactions so that the corresponding quantum efficiency could bedegraded.ZnOtetrapods coatedwithTiO2nanoparticles were also suggested for the realization of high efficiency photocatalysts, but the poor control of the total surface exposure area for both metal oxides limited their usefulness as high efficiency photocatalysts. Alternatively, the use of a

Synthesis, characterization, self-assembly, and physical properties of 11-methylbenzo[d]pyreno[4,5-b]furan.

Synthesis, structure, and physical properties of a novel 11-methylbenzo[d]pyreno[4,5-b]furan (BPF) and its self-assembly in water have been reported. The performance of nanowire-based films in organic light-emitting diodes is much better than that of the thin film deposited by directly drop-coating BPF molecules in THF solution. SEM study indicates that the well-organized structure (nanowires) is an important factor in enhancing the performance of OLED devices.