Graphene Structure in Carbon Nanocones and Nanodiscs

Carbon nanoparticles, like nanocones and nanodiscs, can be obtained by mechanical treatment of carbon nanofilaments. Microstructural studies suggest that in nanocones the conical graphene stacking with progressively increasing apex (cone) angles does not fully agree with current theoretical geometry models, such as a closed cones model and a cone−helix model. The unusual stacking form of nanocones was taken into account in a modified cone−helix model. The formation mechanism of the distinctive microstructure is attributed to the inclined anchoring effect, and the relaxation of internal stresses, which were induced by the confined pyrolysis process, resulting in easier disintegration by sonication the nanofilaments. This is disclosed for the first time in literature regarding the attainment of uniform carbon nanoparticles

Layer-by-Layer Graphene/TCNQ Stacked Films as Conducting Anodes for Organic Solar Cells

Large-area graphene grown by chemical vapor deposition (CVD) is a promising candidate for transparent conducting electrode applications in flexible optoelectronic devices such as light-emitting diodes or organic solar cells. However, the power conversion efficiency (PCE) of the polymer photovoltaic devices using a pristine CVD graphene anode is still not appealing due to its much lower conductivity than that of conventional indium tin oxide. We report a layer-by-layer molecular doping process on graphene for forming sandwiched graphene/tetracyanoquinodimethane (TCNQ)/graphene stacked films for polymer solar cell anodes, where the TCNQ molecules (as p-dopants) were securely embedded between two graphene layers. Poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM) bulk heterojunction polymer solar cells based on these multilayered graphene/TCNQ anodes are fabricated and characterized. The P3HT/PCBM device with an anode structure composed of two TCNQ layers sandwiched by three CVD graphene layers shows optimum PCE (∼2.58%), which makes the proposed anode film quite attractive for next-generation flexible devices demanding high conductivity and transparency

High-Thermal-Transport-Channel Construction within Flexible Composites via the Welding of Boron Nitride Nanosheets

Efficient heat dissipation is a prerequisite for further improving the integration of devices. However, the polymer composites are not satisfying heat dissipation. For that reason, high-thermal-transport channels were manufactured by the direct freezing method and boron nitride nanosheets (BNNS) were further welded by carbonization. Composites with high thermal conductivity (7.46 W m–1 K–1) were obtained by immersion in poly­(dimethylsiloxane) (PDMS). Thermal conductivity enhancement of composites reached about 3900% at 15.8 vol % loading of BNNS. Besides, the composites maintained the structural flexibility of PDMS and allowed repeated bending and twisting. In addition, the PDMS composites exhibited excellent antistatic properties because of a conductive network formed by residual carbon. Therefore, dust could be avoided and the surface kept clean. This provides a better choice for thermal management materials and meets the antistatic requirements of the devices

Hydrophilic modification of carbon nanotube to prepare a novel porous copper network-carbon nanotube/erythritol composite phase change material

Carbon nanotube(CNT)-based materials is a promising thermally conductive filler for phase change materials(PCM), while its widely applications are greatly hampered by the hydrophobicity of CNTs. In this work, a novel composite PCM based on hydrophilic modified porous copper network(PCN)-CNT filler and erythritol(Ery) was explored. The hydrophilic modified PCN-CNT filler can be obtained upon heat treatment. During the heat treatment process, defects and oxygen-containing functional groups formed on the surface of CNTs, thus improving the hydrophilicity of CNTs. The optimum heat treatment temperature is determined to be 500°C, at which the adsorptive capacity of the modified filler reaches 88.2% for Ery, larger than 28.2% of the unmodified one. The as-prepared PCN-CNT/Ery composite PCM maintains a similar melting point to that of pure Ery, and its latent heat is as high as 213.2 J g−1. The thermal conductivity of PCN-CNT/Ery composite PCMs increases by 892% and 51% compared with pure Ery and PCN/Ery composite PCM, respectively. Moreover, the PCN-CNT filler could help improve the supercooling of Ery significantly. Besides, the enthalpy loss of the composite PCM was negligible after 20 cycles. Defects and functional groups are introduced on the surface of CNTs by heat treatment. Therefore, the heat-treated CNTs showed a transition from hydrophobic to hydrophilic, thus improving the interface compatibility of PCN-CNT and Ery phases in composites. Highly conductive PCN-CNT filler modified under the optimal heat treatment temperature compound with pure Ery by vacuum impregnation, significantly improving the thermal transfer properties of Ery. </p

Solid-Phase Coalescence of Electrochemically Exfoliated Graphene Flakes into a Continuous Film on Copper

The ability to directly synthesize high-quality graphene patterns over large areas is important for many applications such as electronic and optoelectronic devices and circuits. Here, we report a facile and scalable approach to coalesce and recrystallize electrochemically exfoliated graphene flakes into a continuous film by thermal annealing on copper foils. The underlying growth mechanism involves defect-mediated decomposition of electrochemically exfoliated graphene flakes into active polycyclic carbon species, followed by coalescence of the active carbon species into a continuous, monolayer film of high material quality. First-principles calculations confirm that the enhanced affinity of the polycyclic carbon species with copper effectively prevents their surface desorption at elevated temperatures, which is distinct from graphene growth based on the decomposition of solid carbon sources into gaseous hydrocarbons. Significantly, the localized supply of active carbon species in our approach enables spatially confined growth of graphene. Combined with stencil printing of the exfoliated flakes, transparent and conductive graphene circuits have been directly synthesized over large areas

High-Thermal-Transport-Channel Construction within Flexible Composites via the Welding of Boron Nitride Nanosheets

Efficient heat dissipation is a prerequisite for further improving the integration of devices. However, the polymer composites are not satisfying heat dissipation. For that reason, high-thermal-transport channels were manufactured by the direct freezing method and boron nitride nanosheets (BNNS) were further welded by carbonization. Composites with high thermal conductivity (7.46 W m–1 K–1) were obtained by immersion in poly­(dimethylsiloxane) (PDMS). Thermal conductivity enhancement of composites reached about 3900% at 15.8 vol % loading of BNNS. Besides, the composites maintained the structural flexibility of PDMS and allowed repeated bending and twisting. In addition, the PDMS composites exhibited excellent antistatic properties because of a conductive network formed by residual carbon. Therefore, dust could be avoided and the surface kept clean. This provides a better choice for thermal management materials and meets the antistatic requirements of the devices

Non-Enzymatic Glucose Sensor Based on Hierarchical Au/Ni/Boron-Doped Diamond Heterostructure Electrode for Improving Performances

A novel hierarchical Au/Ni/boron-doped diamond (BDD) heterostructure electrode was fabricated by two-step heat-treatment. The heterostructure that hierarchical Au/Ni nanoparticles are embedded on the surface of BDD was demonstrated by transmission electron microscope (TEM). Cyclic voltammetry (CV) and amperometric detection were used to test electrochemical properties of the prepared electrodes. The Au/Ni/BDD electrode exhibited enhanced catalytic activity and stability in glucose detection, as compared to that of the Au/BDD and Ni/BDD electrodes. On the optimal NaOH concentration and applied potential, the Au/Ni/BDD electrode exhibited an extremely wide detection range of 0.005–32 mM with high sensitivity of 1229.5 ?AmM?1cm?2 and an excellent long-term stability (maintains 94.8% of initial current after one month). In addition, the prepared electrode also exhibited a low detection limit of 2 ?M (S/N = 3), good selectivity and reproducibility. At last, the reasons for enhanced catalytic activity and excellent stability of Au/Ni/BDD electrode were discussed.</p

Efficient Thermal Transport Highway Construction Within Epoxy Matrix via Hybrid Carbon Fibers and Alumina Particles

Polymer composites with excellent thermal conductivity and superior mechanical strength are in high demand in the electrical engineering systems. However, achieving superior thermal conductivity and mechanical properties simultaneously at high loading of fillers will still be a challenging issue. In this work, a facile method was proposed to prepare the epoxy composite with carbon fibers (CFs) and alumina (Al2O3). This CF and Al2O3 hybrid structure can effectively reduce the interfacial thermal resistance between the matrix and the CFs. The thermal conductivity of epoxy composite with 6.4 wt % CFs and 74 wt % Al2O3 hybrid filler reaches 3.84 W/(m K), which is increasing by 2096% compared with that of pure epoxy. Meanwhile, the epoxy composite still retains outstanding thermal stability and mechanical performance at high filler loading. A cost-effective avenue to prepare highly thermally conductive and superior mechanical properties of polymer-based composites may enable some prospective application in advanced thermal management

Antifouling nanoporous diamond membrane for enhanced detection of dopamine in human serum

In vivo tracking or in vitro real sample analysis by electrochemistry is one of the most straight and useful methods in biosensor field. However, surface biofouling of electrodes by non-specific protein adsorption is inevitable and usually leads to a decrease in sensitivity. Here, we developed a Nafion-coated porous boron-doped diamond (NAF/pBDD) electrode with hydrophobic nanostructures to minimize the biofouling effect and selectively detect dopamine (DA). Larger active area was obtained by this procedure compared to a bare diamond electrode. The as-prepared electrode shows excellent antifouling property and enrichment capacity toward selective detection of dopamine (DA). The low background current of the BDD electrode and the enhanced signals enables a lower detection limit, 42 nmol L?1, and a wider linear range, 0.1–110 ?mol L?1, for determination of DA in human serum. Additionally, the facile modified electrode demonstrated renewable property and long-term stability due to the fact that the antifouling nanostructures belong to its own.</p