Aerosol-Assisted Heteroassembly of Oxide Nanocrystals and Carbon Nanotubes into 3D Mesoporous Composites for High-Rate Electrochemical Energy Storage.

Nanostructured composites built from ordinary building units have attracted much attention because of their collective properties for critical applications. Herein, we have demonstrated the heteroassembly of carbon nanotubes and oxide nanocrystals using an aerosol spray method to prepare nanostructured mesoporous composites for electrochemical energy storage. The designed composite architectures show high conductivity and hierarchically structured mesopores, which achieve rapid electron and ion transport in electrodes. Therefore, as-synthesized carbon nanotube/TiO2 electrodes exhibit high rate performance through rapid Li(+) intercalation, making them suitable for ultrafast energy storage devices. Moreover, the synthesis process provides a broadly applicable method to achieve the heteroassembly of vast low-dimensional building blocks for many important applications.

Hierarchically porous activated carbons prepared via a dissipative process: a high-capacity cathode for Li-ion capacitors.

Activated carbons with high specific surface area (SSA) and well-modulated pore structure are highly desirable for achieving high-performance capacitive energy storage. Herein, hierarchically porous activated carbons (PACs) are synthesized by a tableting-activation method. The quick release of high-pressure gaseous products from the inside of the tablets can be regarded as a dissipative process, which leads to the formation of well-ordered high density meso- or macropores in the resulting material. The porous structure of the PACs has been modulated by adjusting the dissipative process parameters, such as the tableting pressure and tablet thickness. As a result, the optimal PAC (PAC-10) possesses an ultrahigh SSA (up to 3211 m2 g-1) and a well-developed hierarchical porous structure, which leads to an excellent capacitive energy-storage performance both in an aqueous electrolyte supercapacitor system and a Li ion capacitor (LIC) system. In particular, as a cathode for LICs, PAC-10 exhibits an extremely high specific capacity of 251 mA h g-1 at 0.5 A g-1 and still retains 158 mA h g-1 at a high rate of 15 A g-1.

MnO@graphene nanopeapods derived via a one-pot hydrothermal process for a high performance anode in Li-ion batteries.

Although transition metal oxide-carbon (TMO-C) composites exhibit high Li storage capacity, the weak bonding between TMO particles and carbon mainly via van der Waals' force and the limited internal void space result in poor rate capability and cycling performance. Herein, MnO@graphene nanopeapods are produced by calcination of hydrothermally-synthesized MnO2-C composites. The flexible graphene shells provide superior conductivity and excellent structural stability to the MnO cores, and the enough internal void space can significantly buffer the drastic volume expansion. The MnO@graphene nanopeapods exhibit high Li storage capacity (1168 mA h g-1 at 50 mA g-1 and 945 mA h g-1 at 500 mA g-1) at a voltage platform of ∼1.2 V, excellent rate capability (728 mA h g-1 at 1000 mA g-1 and 505 mA h g-1 at 3000 mA g-1), high initial coulombic efficiency (85.9%) and remarkable long-life cycling performance (undiminished after 1000 cycles). The MnO@graphene nanopeapods have been successfully used as the anode to assemble a full battery with LiFePO4 as the cathode. Our results provide a useful and rational strategy to design high performance graphene-supported MnO composites for Li ion batteries.

Carbon quantum dots derived by direct carbonization of carbonaceous microcrystals in mesophase pitch.

Aggregation of the central aromatic ring system of asphaltene molecules due to π-π interaction can lead to the formation of carbon quantum dots (CQDs). However, to date, such a roadmap has not been demonstrated. Here, we present a simple approach to the synthesis of CQDs by direct carbonization of dispersed carbonaceous microcrystals in mesophase pitch. The size of the as-prepared CQDs is modulated by adjusting the nucleation temperature for mesophase formation. Due to the oxygen-free character, the CQDs exhibit excitation-independent fluorescent behavior with a quantum yield up to 87%. The CQDs were successfully applied to fluorescent detection of Fe3+ ions with good specificity and sensitivity. Our results not only provide a scalable production of CQDs at low cost, but also give valuable clues to understand the solidification of asphaltene at nanoscale.

Excellent Compatibility of the Gravimetric and Areal Capacitances of an Electric-Double-Layer Capacitor Configured with S-Doped Activated Carbon.

Coffee grounds were converted into S-doped activated carbon (SAC) in the presence of an active agent and S dopant through a one-step synthesis approach. Carbonization, activation, and S doping was achieved through this one-step methodology. The SAC was used as an electrode material for the preparation of a symmetric electrical-double-layer capacitor (EDLC), and the influence of the loading mass of the active materials on the capacitive behaviors was investigated. The assembled SAC-based symmetric EDLC not only yielded a high capacitance but it also afforded a satisfactory capacitance retention. The symmetric EDLC constructed with loading mass SAC of 7.5 mg cm-2 was capable of delivering a maximum gravimetric and areal capacitance of 200 F g-1 and 1.5 F cm-2 , respectively. The compatibility of the gravimetric and areal capacitances of SAC was mainly attributed to the high abundance of interconnected pore channels, which were beneficial for the increased contact area between electrode and electrolyte ions, fast charge transfer, and fast diffusion of the electrolyte ions. In addition to the well-developed porous networks, the introduction of S into the carbon frameworks significantly enhanced the electrical conductivity, storage capacity, and rate capability. The developed one-step synthesis provides a facile and effective route for obtaining high-performance capacitive electrode materials and realizing high value-added utilization of biomass.

Enhanced Electromagnetic Microwave Absorption Property of Peapod-like MnO@carbon Nanowires.

Investigating lightweight electromagnetic microwave absorption materials is still urgent because of the issue related to the electromagnetic pollution or military defense. Our findings indicate that core-shell MnO@carbon nanowires (MnO@C NWs) achieve substantially enhanced microwave absorption, suggesting the suitable impedance matching induced by the synergetic effect between MnO and carbon. Furthermore, the peapod-like MnO@C NWs with internal void space can be facially synthesized by partial etching of core-shell MnO@C NWs. The peapod-like MnO@C NWs with internal voids/cavities exhibit dramatically enhanced electromagnetic microwave absorption property when the carbon content is about 64 wt %, a minimum reflection loss (RL) of -55 dB at 10 wt % loading was observed at 13.6 GHz, and the bandwidth of RL less than -10 dB (90% absorption) covers 6.2 GHz at the thickness of 2 mm. The excellent electromagnetic microwave absorption performance is superior to the most of MnO x/C composites in the literatures, which probably benefits from the dielectric polarization among conductive network structure between MnO and carbon, as well as the multiple reflection and absorption induced by internal void space. Our work is expected to pave an effective way to extend the electromagnetic microwave absorption performance of MnO/C composites through partial etching to create a void space.

High capacity oil adsorption by graphene capsules.

We report on a chemical vapor deposition synthesis of graphene capsules (GCs) in sizes of tens to thousands of nanometers and their oil adsorption performance. MgO particles with different particle sizes are used as templates to produce GCs with different sizes. At a larger GC size and higher pore volume, a higher oil capacity is obtained. The highest oil adsorption capacity achieved by the GCs is 156 gdiesel gGC-1, which is much higher than that obtained by expanded graphite. The adsorption capacity proportionally increases as the viscosity of the fluid increases. Both the capsule structure and the viscosity of oil are relative to the adsorption capacity, showing that capillary adsorption with a limited entrance might have contributed to the high capacity oil adsorption by GCs.

Improvement of Fe/MgO catalysts by calcination for the growth of single- and double-walled carbon nanotubes.

Calcination at 900-1000 degrees C for 8-12 h of an Fe/MgO catalyst prepared by impregnation was found to result in a uniform MgFe2O4/MgO solid solution that showed a successful settling of well-dispersed iron species into the MgO lattice. During methane reduction, many iron-containing particles with a diameter of about 4 nm were formed on the catalyst surface to provide numerous active sites for the growth of single- and double-walled carbon nanotubes. There was a significant improvement of the Fe/MgO catalyst that resulted in a high yield of impurity-free nanotubes. Using C2H4 cracking at 600 degrees C and transmission electron microscope observations, the Fe species distribution in the catalysts and microscope images of nanotube growth were described in detail. H2 reduction of the calcined Fe/MgO catalyst was found to cause the formation of iron layers on the catalyst surface, which resulted in the growth of only carbon layers. The results are useful for understanding changes in the metal species distribution in the catalysts and the nanotube growth mechanism, and they provide a simple method to improve Fe/MgO catalysts.

High-surface-area nanomesh graphene with enriched edge sites as efficient metal-free cathodes for dye-sensitized solar cells.

Exploiting cost-effective and highly efficient counter electrodes (CEs) has been a persistent objective for practical application of dye-sensitized solar cells (DSSCs). Here, we present an efficient CE by using pure three-dimensional (3D) nanomesh graphene frameworks (NGFs) which are synthesized via a template-directed chemical vapor deposition (CVD) approach. The high-surface-area 3D NGFs associated with the enriched surface edge defects make it very efficient towards I3(-) reduction even without any Pt catalyst. More interestingly, by virtue of the interpenetrating graphene frameworks, the NGFs exhibit excellent electron conductivity, thus leading to facile charge transfer. Consequently, the DSSCs with pure NGFs as CEs display a power conversion efficiency of 7.32%, which is comparable to that of Pt as CEs (7.28%), thereby exhibiting great potential as low-cost and highly efficient CE materials for large-scale deployment of DSSCs.

Enhanced electrode performance of Fe2O3 nanoparticle-decorated nanomesh graphene as anodes for lithium-ion batteries.

Nanostructured Fe2O3-nanomesh graphene (NMG) composites containing ∼3 nm Fe2O3 nanoparticles (NPs) uniformly distributed in the nanopores of NMG are synthesized by an adsorption-precipitation process. As anodes for Li ion batteries (LIBs), the 10%Fe2O3-NMG composite exhibits an upward trend in the capacity and delivers a reversible specific capacity of 1567 mA h g(-1) after 50 cycles at 150 mA g(-1), and 883 mA h g(-1) after 100 cycles at 1000 mA g(-1), much higher than the corresponding values for the NMG electrode. The significant capacity enhancement of the 10%Fe-NMG composite is attributed to the positive synergistic effect between NMG and Fe2O3 NPs due to the catalytic activity of Fe2O3 NPs for decomposition of the solid electrolyte interface film. Our results indicate that decoration of ultrasmall Fe2O3 NPs can significantly change the surface condition of graphene. This synthesis strategy is simple, effective, and broadly applicable for constructing other electrode materials for LIBs.

Phosphorus and nitrogen dual-doped few-layered porous graphene: a high-performance anode material for lithium-ion batteries.

Few-layered graphene networks composed of phosphorus and nitrogen dual-doped porous graphene (PNG) are synthesized via a MgO-templated chemical vapor deposition (CVD) using (NH4)3PO4 as N and P source. P and N atoms have been substitutionally doped in graphene networks since the doping takes place at the same time with the graphene growth in the CVD process. Raman spectra show that the amount of defects or disorders increases after P and N atoms are incorporated into graphene frameworks. The doping levels of P and N measured by X-ray photoelectron spectroscopy are 0.6 and 2.6 at %, respectively. As anodes for Li ion batteries (LIBs), the PNG electrode exhibits high reversible capacity (2250 mA h g(-1) at the current density of 50 mA g(-1)), excellent rate capability (750 mA h g(-1) at 1000 mA g(-1)), and satisfactory cycling stability (no capacity decay after 1500 cycles), showing much enhanced electrode performance as compared to the undoped few-layered porous graphene. Our results show that the PNG is a promising candidate for anode materials in high-rate LIBs.

Enhancing the Li storage capacity and initial coulombic efficiency for porous carbons by sulfur doping.

Here, we report a new approach to synthesizing S-doped porous carbons and achieving both a high capacity and a high Coulombic efficiency in the first cycle for carbon nanostructures as anodes for Li ion batteries. S-doped porous carbons (S-PCs) were synthesized by carbonization of pitch using magnesium sulfate whiskers as both templates and S source, and a S doping up to 10.1 atom % (corresponding to 22.5 wt %) was obtained via a S doping reaction. Removal of functional groups or highly active C atoms during the S doping has led to formation of much thinner solid-electrolyte interface layer and hence significantly enhanced the Coulombic efficiency in the first cycle from 39.6% (for the undoped porous carbon) to 81.0%. The Li storage capacity of the S-PCs is up to 1781 mA h g(-1) at the current density of 50 mA g(-1), more than doubling that of the undoped porous carbon. Due to the enhanced conductivity, the hierarchically porous structure and the excellent stability, the S-PC anodes exhibit excellent rate capability and reliable cycling stability. Our results indicate that S doping can efficiently promote the Li storage capacity and reduce the irreversible Li combination for carbon nanostructures.

High capacity gas storage in corrugated porous graphene with a specific surface area-lossless tightly stacking manner.

We report for the first time an experimental investigation of gas storage in porous graphene with nanomeshes. High capacity methane storage (236 v(STP)/v) and a high selectivity to carbon dioxide adsorption were obtained in the nanomesh graphene with a high specific surface area (SSA) and a SSA-lossless tightly stacking manner.

Gram-scale synthesis of nanomesh graphene with high surface area and its application in supercapacitor electrodes.

Graphene that had nanomeshes, only one to two graphene layers, and specific surface areas of up to 1654 m(2) g(-1) was produced on gram-scale by template growth on porous MgO layers. Its unique porous structure gave excellent electrochemical capacitance (up to 255 F g(-1)), cycle stability and rate performance.

Nanographene-constructed carbon nanofibers grown on graphene sheets by chemical vapor deposition: high-performance anode materials for lithium ion batteries.

We report on the fabrication of 3D carbonaceous material composed of 1D carbon nanofibers (CNF) grown on 2D graphene sheets (GNS) via a CVD approach in a fluidized bed reactor. Nanographene-constructed carbon nanofibers contain many cavities, open tips, and graphene platelets with edges exposed, providing more extra space for Li(+) storage. More interestingly, nanochannels consisting of graphene platelets arrange almost perpendicularly to the fiber axis, which is favorable for lithium ion diffusion from different orientations. In addition, 3D interconnected architectures facilitate the collection and transport of electrons during the cycling process. As a result, the CNF/GNS hybrid material shows high reversible capacity (667 mAh/g), high-rate performance, and cycling stability, which is superior to those of pure graphene, natural graphite, and carbon nanotubes. The simple CVD approach offers a new pathway for large-scale production of novel hybrid carbon materials for energy storage.

Unsynchronized diameter changes of double-wall carbon nanotubes during chemical vapour deposition growth.

Novel structural changes of double-wall carbon nanotubes (DWNTs) triggered by sudden swings of reaction condition have been elucidated. A quick temperature decrease or increase would lead to a decrease or increase, respectively, in the CH(4) decomposition rate and to reformation of catalyst metal particles. In particular, unsynchronized diameter changes of the inner and the outer tubes are observed in the DWNTs prepared by CoMo/MgO catalysts. We have found that the difference of the growth surroundings for the inner and outer tubes of DWNTs can consistently explain the observed unsynchronized diameter changes.

[Association between expressions of HSP70, HSP90 and efficacy of chemotherapy in colorectal cancer patients with unresectable liver metastasis].

OBJECTIVE: To investigate the association between expressions of HSP70, HSP90 and efficacy of chemotherapy in colorectal cancer patients with unresectable liver metastasis. METHODS: Data of 52 colorectal cancer cases, whose primary colorectal focuses were resected but hepatic metastatic tumors were unresectable, were reviewed retrospectively. All the patients underwent FOLFOX4 regimen well. Immunohistochemistry assay was applied to determine the expressions of HSP70 and HSP90 in primary focus tissues. The number and size of hepatic metastatic tumors pre- and post-chemotherapy were compared by CT scanning. RESULTS: Partial remission(PR) rate was 33.3% in cases with up-regulated expression of HSP70, while 64.5% in cases with down-regulated expression of HSP70, whose difference was significant. PR rate was 50% in cases with up-regulated expression of HSP90, and 53.1% in the others with down-regulated expression of HSP90, whose difference was not significant. CONCLUSIONS: FOLFOX4 regimen has advantages in cases with lower HSP70 expression over those with higher HSP70 expression. HSP90 expression level is not associated with the efficacy of FOLFOX4 regimen.