Rational structure design of microwave absorption material (MAM) is of fundamental significance in terms of enhancing the electromagnetic microwave absorption performance and deeply understanding the specific correlation between the material structure and its electromagnetic microwave absorption (EMA) performance. Here, bowl-like carbon nanoparticles (BLCNs) as novel MAM have been successfully fabricated via calcination of bowl-like polydopamine. Interestingly, BLCNs have exhibited dramatically enhanced EMA performance with a minimum reflection loss of −45.3 dB and an effective bandwidth of below −10 dB in the wide range of 4.2 GHz, implying the unique critical role of the microstructure in adjusting the EMA performance. Our work not only paves an attractive way for the design of advanced and lightweight MAM, but also provides valuable insights into the relationships between the material structure and its EMA performance.

The scalable production of large quantities of defect-free graphene nanosheets (GNs) with low cost and excellent properties is essential for practical applications. Despite the highly intense research of this area, the mass production of graphene nanosheets with high solubility remains a key challenge. In the present work, we propose a scalable exfoliation process for hydrophilic GNs by ball-milling-assisted supercritical CO2 exfoliation in the presence of poly(vinylpyrrolidone) via the synergetic effect of chemical peeling and mechanical shear forces. The exfoliation difficulty has been reduced due to the intercalation effects of supercritical CO2 molecules. With the ball-milling assistance, the modifier has been introduced onto the edge or/and surface of the GNs. The process results in hydrophilic GNs with little damage to the in-plane structure. The GNs can be dispersed in various solvents with a concentration of up to 0.854 mg/mL (water) and remain stable for several months.

Three-dimensional individual S-doped porous red-blood-cell-like graphene (SRBCG) microspheres with double concave-surface morphology duplicated from a template-directed chemical vapor deposition process in a fluidized bed reactor not only exhibit high porosity, good structural stability, and strong anticompression properties but also present superior capacitive energy-storage abilities with respect to a symmetric supercapacitor (great compatibility at different rates) and a Li ion capacitor (no capacitance loss after 3500 cycles at 2 A g–1). The well-kept integrity of the electrode configuration after cycling benefits from the intrinsic robust scaffold which acts as a structural buffer for volume expansion to inhibit structure collapse. The unique individual microarchitecture with well-developed pore channels of SRBCG can effectively prevent the obtained graphene from aggregation or restacking, expanding the contact area between electrolyte ions and the electrode. The excellent capacitive behaviors of SRBCG are guaranteed by the unique robust microarchitecture accompanied by the good structural stability. Additionally, the fluidized bed technology is conducive to the realization of the homogeneous growth and scalable production of SRBCG.

Exploiting highly active and stable counter electrodes (CEs) has been a persistent challenge for the practical application of dye-sensitized solar cells (DSSCs). Herein, we present an edge-enhanced modification to fabricate nitrogen doped holey graphene (NHG) by rationally employing N2 plasma treatment at the exposed edge sites of holey graphene. The as-synthesized NHG exhibits a highly conductive and unique holey scaffold with a large surface area, along with abundant edge-induced topological defects and nitrogen dopants. Benefiting from such unique features, NHG exhibits outstanding electrocatalytic activity and high electrochemical stability for the I−/I3− redox reaction. Furthermore, density functional theory calculations are performed to further elucidate the underlying mechanism behind this encouraging performance, in particular the effect of edge-induced topological defects. The DSSCs based on NHG CEs display a power conversion efficiency of 9.07%, which is even superior to that of Pt (8.19%). These results strongly indicate possibilities for the large-scale fabrication of low-cost and metal-free NHG materials for DSSCs with an I-complex redox couple.

•Producing hydrogen through infrared light irradiation by Al@rGO.•Preventing passivation of Al and accelerating Al-water reaction by graphene coating.•Infrared light absorption of graphene enhances water temperature.•Byproduct is nature friendly and is recyclable for toxic absorption.Promoting the Al-water reaction in a neutral condition without adding any sacrificial agents and generating no poisonous byproduct is always the aim of green production of hydrogen. In this study, we fabricated the reduced graphene oxide wrapped aluminum nanoparticles (Al@rGO) through an ultrasonic atomization process. And a high-efficiency hydrogen production is realized in pure water under the infrared light irradiation. Firstly, the graphene wrapping keeps the activity of aluminum nanoparticles by preventing the formation of dense passivation films on the surface of Al and accelerating the ions migration between Al and water. Secondly, the water temperature is enhanced due to the infrared light absorption of graphene, which contributes to the improved hydrogen generation as well. Moreover, the residual byproduct is nature-friendly and recyclable for toxic ion absorption applications. Our results provide an important technique towards the large scale green production of hydrogen by Al@rGO.Download high-res image (92KB)Download full-size image

•NG-Fe2O3 catalysts are prepared by a facile one-pot hydrothermal method.•The catalysts show excellent activity in catalysis of aldehyde oxidization.•The catalysts present certain tolerance to variety of different functional groups.•The synergistic effect of NG and Fe2O3 is revealed by DFT calculations.Promotion of nitrogen-doped graphene (NG) by incorporation of ferric oxide (NG-Fe2O3) is found to strongly enhance the activity in the catalytic oxidization of aldehyde to synthesize carboxylic acid with O2. The composite NG-Fe2O3 catalysts can be fabricated by a facile one-pot hydrothermal method. The characterization results of the composite catalysts have revealed that the Fe2O3 nanoparticles (NPs) with sizes of 40–90 nm are not only on both sides of NG sheets but also tightly enwrapped by the graphene layers. In comparison to NG and Fe2O3 NPs, synergistic adsorption that confirmed by DFT studies has been created on the NG-Fe2O3 composites, where both NG and Fe2O3 are proposed to be involved in the adsorptive interaction. The synergistic adsorption can lead to strengthen O2 molecule adsorption of NG and weaken O2 molecule adsorption of Fe2O3 NPs. More importantly, the NG-Fe2O3 composite is found to considerably facilitate the longest elongation of O-O bonds and contribute to the striking enhancement of the catalytic performance. The highly active NG-Fe2O3 composite shows wide scope for catalysis of oxidation of aldehydes to carboxylic acids and good stability for recycle six times.Promotion of nitrogen-doped graphene (NG) by incorporation of ferric oxide (NG-Fe2O3) is found to strongly enhance the activity in the catalytic oxidization of aldehyde to synthesize carboxylic acid with O2. The composite NG-Fe2O3 catalysts can be fabricated by a facile one-pot hydrothermal method. In comparison to NG and Fe2O3 NPs, synergistic adsorption have been created on the NG-Fe2O3 composites, where both NG and Fe2O3 are proposed to be involved in the adsorptive interaction, which has been confirmed by DFT studies. This can lead to strengthen O2 molecule adsorption of NG and weaken O2 molecule adsorption of Fe2O3 NPs. More importantly, the NG-Fe2O3 composite is found to considerably facilitate the longest O-O bonds of O2 and contribute to the striking enhancement of the catalytic performance. The highly active NG-Fe2O3 composite shows wide scope for catalysis of oxidation of aldehydes to carboxylic acids and good stability for recycle six times.Download high-res image (146KB)Download full-size image

•Cu/Gra/AZO transparent conductive film was fabricated on the PET substrate.•This multilayer owns a low and stable resistance during the deformation process.•This transparent conductive film shows a good air stability.The fabricating of transparent conductive films with low resistance, high transparency, flexibility and air stability is significant in the study of flexible electronics. In this work, Cu nanowire/Graphene/Al doped ZnO (Cu/Gra/AZO) composite transparent conductive films were fabricated on PET substrate at room temperature. It is found that this composite film has a high transmittance of 74% at 550 nm, a low sheet resistance of 9.40 Ω/sq and good air stability. In this sandwich structure electrode, Cu nanowires (NWs) play an important role for ensuring the low resistance of the composite film, and the addition of graphene further reduces the resistance plus protects Cu NWs from oxidation. Moreover, the top layer AZO can protect the graphene layer from external damage and improve its stability.We have successfully fabricated a Cu/Gra/AZO multilayer composite film on PET substrate, which shows a relatively low sheet resistance, high transmittance, good flexibility and air stability, indicating the expectation of being applied to flexible electronic products.Download high-res image (82KB)Download full-size image

Phosphorus-doped nanomesh graphene (PG) with huge specific surface area and lamellar hexagonal structure has been synthesized by a thermal annealing method using MgO as a template and triphenylphosphine (TPP) as both phosphorus and carbon source. The synthesized PG with a high phosphorous content of 1.61 at% is found to exhibit efficient metal-free heterogeneous catalytic activity for aerobic oxidative coupling of amines catalysts under mild and neat conditions using molecular oxygen as the oxidant. Moreover, our results indicate that the phosphorus doping is more efficient to promote the catalytic activity than that of nitrogen doping in aerobic oxidative coupling of amines. Based on the results of density function theory (DFT) calculations, it is found that phosphorus incorporated into the graphene matrix exhibit the highest catalytic activity due to its lowest adsorption energy of benzylamine and longest elongation of OO bonds.Download high-res image (296KB)Download full-size image

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.

Readily prepared CuO nanowires (CuO NWs) have been found to be effective heterogeneous catalysts for the 1,3-dipolar cycloaddition (CuAAC) reaction without using any additional support and bases. Examination of CuO nanowire catalysts synthesized at various temperatures showed that the use of CuO-600 catalyst was the best choice for the success of the present click reaction. Not only aromatic and heteroaromatic alkynes but also alkylalkynes were catalyzed regioselectively, affording triazoles in excellent yields. Furthermore, we have identified that the reaction proceeded in a heterogeneous manner. It is noteworthy that the CuO-600 catalyst can be easily recovered and reused nine times.

•TiO2/g-C3N4/G was synthesized by photochemical reduction self-assembly methods.•Noticeable photocurrent response exhibits during both UV-region and visual-region.•High photocatalytic activity and selectivity show in the reduction of nitrobenzene.•Synergistic effect facilitate the separation of photogenerated charges.A simple self-assembly photochemical reduction method has been proposed to prepare highly photocatalytic TiO2 nanowire/g-C3N4 nanosheet/graphene heterostructures (TiO2/g-C3N4/G). In this hybrid structure, graphene enhances the charge transportation during photocatalytic process, and TiO2 nanowires prevent graphene and g-C3N4 from restacking. Meanwhile, g-C3N4 with a more suitable band gap, extends the adsorption edge of the TiO2/g-C3N4/G composite to visual-region. Benefiting from the positive synergetic effect, 97% of nitrobenzene can be selectively reduced within 4 h by using TiO2/g-C3N4/G as the photocatalyst. The TiO2/g-C3N4/G composite with 3D structure demonstrates a great potential in selective oxidation and reduction of organics for the synthesis of high added-value organic compounds.Download high-res image (241KB)Download full-size imageTiO2 nanowire/g-C3N4 nanosheet/graphene heterostructures (TiO2/g-C3N4/G) with highly photocatalytic activity has been prepared via a simple self-assembly photochemical reduction method. Benefiting from the positive synergetic effect, 97% of nitrobenzene can be selectively reduced within 4 h by using TiO2/g-C3N4/G as the photocatalyst.

•Graphene film wrapped on the NiTi alloy exhibits good anticorrosion and biocompatibility.•The supervisory of graphene is its flexibility, which keeps excellent mechanical stability upon deformation.•The behavior of graphene for inhibiting poisonous Ni ions releasing was explored through theoretical calculation.Due to their unique shape memory effect and superelasticity, NiTi shape memory alloys have been considered for a wide range of biomedical applications. However, they are still controversial because of the potential toxic, carcinogenic and allergic effects caused by Ni2 + release for a long term use. Wrapping protective layers with good flexibility and biocompatibility is significant for inhibiting the poisonous Ni2 + releasing from NiTi. Here, we report a novel method to protect the NiTi and enhance its biocompatibility by using graphene fabricated via a modified chemical vapour deposition (CVD) technique. The graphene layer not only prevents effectively the leak of Ni2 + but also improves the biocompatibility of NiTi upon deformation. The detailed mechanism for enhancing the anti-corrosion and biocompatibility of NiTi alloy by using graphene is also explored. Compared with traditional surface modification layer, graphene obtained by CVD is chemically inert and highly flexible, possesses both good anti-corrosion and biocompatibility properties, which may improve the surface coatings for NiTi alloys and promote more application of graphene in biomedical materials.A large sheet of graphene was fabricated by a CVD method, and transferred onto the NiTi shape memory alloy substrate. It is calculated that the significant inhabitation of Ni2 + releasing is kinetically hindered caused by the high energy barrier built upon graphene wrapping even under stain or with Cl−. The graphene film obtained by CVD is chemically inert and highly flexible, which demonstrates a significant reduction of Ni2 + releasing from NiTi and greatly enhances its anti-corrosion ability. Additionally, both blood and tissue cells display a better attachment on the NiTi with graphene manifests the improvement of its biocompatibility.Download high-res image (175KB)Download full-size image

Four kinds of nitrogen-doped graphene (NG) as metal-free catalysts are synthesized by a one-step hydrothermal reaction and thermal treatment using graphene oxide and urea as precursors. It is found that the reduction of nitroarenes can be catalyzed by using a low NG loading and a small amount of NaBH4 in water with high yield. The type of nitrogen species in NG has an important effect on the reduction reaction. The NG catalyst containing the most graphite N shows the highest catalytic activity during reduction of nitroarenes, which demonstrates that the graphite N of NG plays a key role in impelling this reaction. The reaction mechanism is proven by GC-MS experiments, and DFT calculations reveal the reasons for the graphite N showing better catalytic activity. It is worth noting that no dehalogenation phenomenon occurs during the reduction process for halogen-substituted nitroarenes in contrast to conventional metal catalysts. In addition, the NG catalyst can be simply recycled and efficiently used for eight consecutive runs with no significant decrease in activity.

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.

•An interconnected N/S-PC has been used as counter electrode in DSSC.•N/S dual-doping can significantly enhance the activity toward I3− reduction.•N/S-PC electrode shows a comparable photovoltaic performance with Pt electrode.•Our work provides a new way in making high-efficient but low-cost DSSCs.Exploiting cost-effective and efficient counter electrodes (CEs) for the reduction of triiodide (I3−) has been a persistent objective for the development of dye-sensitized solar cells (DSSCs). Here, we propose a strategy for the synthesis of nitrogen and sulfur dual-doped porous carbon (N/S-PC) via a thermal annealing approach by using melamine as N source, and basic magnesium sulfate (BMS) whiskers as S source and templates. Benefiting from the high surface area, unique interconnected structural feature and synergistic effects of N/S dual-doping, the N/S-PC shows excellent electrocatalytic activity toward I3− reduction, which has simultaneously been confirmed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. The DSSC devices with N/S-PC CEs exhibit a PCE up to 7.41%, which is higher than that of DSSC devices with single heteroatom (N or S) doped CEs and even Pt CEs (7.14%).

Hollow carbon nanospheres (HCNs) with tunable sizes have been successfully prepared by the calcination of hollow copolymer nanospheres. Our findings indicate that compared to the counterpart solid carbon particle, HCNs all achieve substantially enhanced microwave absorption, suggesting that hollow structure plays an important role during microwave absorption. Moreover, further investigation on the effect of different HCNs sizes upon microwave absorption has been conducted. It is found that HCNs with an outer diameter of ∼70 nm and inner diameter of ∼30 nm exhibit the champion EM absorption performance, a minimum reflection loss (RL) of −50.8 dB at 13.5 GHz with a thickness of 1.9 mm, along with the corresponding bandwidth of RL less than −10 dB (90% absorption) covering 4.8 GHz. Notably, such excellent microwave absorption performance, probably as a result of well-matched impedance together with multiple reflection induced by the distinctive hollow structure, demonstrates HCNs to be one of the most competitive carbon-based absorbers to date. More importantly, this study provides an effective strategy to tune the microwave performance via tailoring the sizes of HCNs.

Till now, the counter electrode (CE) material for dye sensitized solar cells (DSSCs) has been developed by improving the conductivity and electrocatalytic activity of the material. This work proposes a new technique to further enhance the exploration of advanced CE materials. In the new technique the reflectivity of the CE material (MoS2 based) is increased by vertically inclining the MoS2 on the substrate (FTO). The MoS2 is synthesized through chemical vapor deposition (CVD), which eliminates the complicated CE fabrication process. As a result, the CE possesses high reflectivity which facilitates the absorbance of more photons, and also leads to create more active edge sites exposed to I−/I3− redox couple in the electrolyte. This technique yields an efficiency of approximately 7.5% which excels that of the Pt based (7.28%) electrodes.

Fe3O4 magnetic nanocomposites combined with graphene oxide (GO) and carbon nanotubes (CNTs) are synthesized by a hydrothermal method, followed by synthesis of GO/CNT–Fe3O4 supported Pd nanoparticles using a gas–liquid interfacial plasma (GLIP) method with Pd(OAc)2 as a precursor, and the Pd nanoparticles show a uniform particle size distribution. The catalysts exhibit remarkable catalytic activity during the hydrogenation of nitroarenes under H2 atmosphere at 60 °C in water using a small amount of catalyst, and the catalyst can be magnetically separated from the reaction mixture. The addition of the Fe3O4 component to the GO/CNTs can be used to effectively prevent aggregation and restacking of GO and the CNTs, and the GO/CNT composite can adjust the hydrophilic–hydrophobic property of the catalysts. Furthermore, the Pd catalyst can be readily recovered and reused several times without a significant decrease in activity. It is worth mentioning that the Pd-3 catalysts show remarkable activity during C–H functionalization.

•N–TiO2/N-graphene heterostructures were obtained by a facile hydrothermal method.•The nitrogen atoms originated from urea entered into both the lattice of TiO2 and the skeleton of graphene.•N–TiO2/N-graphene shows better photocatalytic activity to degrade MB than pristine TiO2 nanowires and TiO2/graphene.•The synergistic effect of graphene and N doping led to a better separation of the carriers and a higher photocurrent.N-doped TiO2 nanowire/N-doped graphene (N–TiO2/NG) heterojunctions are fabricated by a simple hydrothermal method in a solution containing urea. In this hybrid structure, a three-dimensional hybrid photocatalyst was fabricated by using one-dimensional N-doped TiO2 nanowires penetrating through two-dimensional graphene nanosheets. Compared with TiO2 nanowire/graphene and N-doped TiO2 nanowire/graphene composites, the N–TiO2/NG heterostructures demonstrate a better photocatalytic performance for the degradation of methylene blue under visible light irradiations, as well as displaying a better recyclability. It is found that the nitrogen atoms originated from the decomposition of urea were not only entered into the lattice of TiO2 nanowires but also doped into the skeleton of graphene nanosheets. Results show that N doping expands the visible light absorption region of TiO2, and N-doped graphene additionally improves the separation and transportation of photogenerated electron–hole pairs plus generating a higher photocurrent, which plays a critical role for enhancing the photocatalytic activity.

•The NiO/CNTs composite was prepared by thermal treatment of Ni(OH)2/CNTs obtained from an in-situ hydro-thermal method.•Porous NiO nanoflakes are threaded by CNTs, leading to the formation of the composite with different NiO loadings•The lightweight NiO/CNTs composite is highly porous and effective for microwave absorption.Composite material of NiO/CNTs consisting of two-dimensional porous NiO nanosheets threaded by carbon nanotubes was prepared by thermal treatment of Ni(OH)2/CNTs obtained from an in-situ hydro-thermal method. The introduction of CNTs during the synthesis processes can effectively prevented the aggregations of NiO nanosheets, and form interpenetrated composite structure. Therefore, porous NiO nanoflakes are threaded by CNTs, leading to the formation of the lightweight composite with different NiO loadings. The as-prepared NiO/CNTs composite is highly porous, effective for microwave absorption. The minimum reflection loss reaches −25.4 dB when the NiO loading is 85 wt% with thickness of 2.0 mm at 10 GHz. This composite material is expected to be a promising candidate as microwave absorbing materials.

A heterogeneous catalytic assembly of the different Pd/PdO ratio nanoparticles supported on oxide carbon nanotubes (OCNTs) can be controllably synthesized by a one-pot gas–liquid interfacial plasma (GLIP) method via adjusting the glow produced parameter. The Pd/PdO nanoparticles have uniform particle size distribution. It is found that the catalysts with different Pd/PdO ratios could affect catalytic activity during the reduction of 4-nitrophenol (4-NP) in water by NaBH4. The best turn over frequency (TOF) value is up to 3000 h−1, which is much higher than the case only using Pd nanoparticles as catalysts. Moreover, the catalysts allowed hydrogenation of nitroarenes in water by atmospheric pressure H2, and it displayed remarkable activity toward the hydrogenation of nitroarenes using low Pd loading in good yields. The catalyst can be simply and efficiently used for ten consecutive runs without significant decrease in activity.

Flexible graphite nanoplatelets (GNPs)–copper nanowires (Cu NWs) composites of a sandwich-like structure were prepared by a simple filtration method. Cu NWs were sandwiched between GNPs films (G/NWs/G). The sandwiched structure results in conductivity up to 3.18 × 105 S m−1, higher than the reported graphene based papers and bulk graphite. The performance of the sandwiched papers is further improved to 8.65 × 105 S m−1 through mechanical pressing. Compared to the pure Cu NWs film, the sandwiched composite is oxidation resistant and stable in air, thus promising as candidates for high performance flexible electronics.

•Pd/PdO nanoparticles supported on porous graphene are synthesized by a gas-liquid interfacial plasma method.•The Pd/PdO electrocatalysts exhibit a high electrocatalytic activity for methanol oxidation.•The PdO present in Pd nanoparticles can enhance the electrocatalytic activity.•The Pd/PdO nanoparticles with PG support displays much better activity than CNT support for methanol oxidation.Pd/PdO nanoparticles supported on porous graphene (PG) are synthesized by a gas-liquid interfacial plasma method using Pd(NO3)2·2H2O as precursor. The Pd/PdO ratios can be controlled by changing the amount of Pd(NO3)2·2H2O. The synthesized Pd/PdO electrocatalysts exhibit a high electrocatalytic activity for methanol oxidation. The Pd/PdO nanoparticles attached on PG support shows better activity than that on oxidation carbon nanotubes support for methanol oxidation. In addition, our findings show that the PdO present in the Pd nanoparticles can enhance the electrocatalytic activity. It is worth to mention that the Pd/PdO nanoparticles supported on porous graphene catalysts show better electrochemical stability than that of commercial Pd/C catalyst.

A novel heterostructure of TiO2 modified Co3O4 (TiO2/Co3O4) acicular nanowire (NW) arrays has been fabricated in this study, which demonstrates a good performance for ethanol detection at working temperatures as low as 160 °C. Co3O4 NW arrays were first grown on an Al2O3 substrate patterned with an Ag/Pd electrode by a hydrothermal method, and then TiO2 nanoparticles were decorated on the surface of Co3O4 NW arrays by using pulsed laser deposition (PLD). It is found that after decoration of TiO2, the TiO2/Co3O4 NW array sensor exhibits a much higher response to ethanol (Rg/Ra = 65, Rg is the sensor resistance measured in a mixture of target gases and Ra is the resistance measured in air) compared with the pristine Co3O4 NW sensor (Rg/Ra = 25). Importantly, the TiO2/Co3O4 sensor has shown a detection limit as low as 10 ppm, and a good reproducibility. The reason for the enhanced sensing properties of TiO2/Co3O4 is considered to be due to the formation of a p–n junction between the p-type Co3O4 and n-type TiO2.

Flower-shaped Au–ZnO hybrid nanoparticles have been prepared via seeding growth and subsequent wet-chemical etching of Au–ZnO core–shell nanoparticles. The etched Au–ZnO hybrid nanoparticles have shown a stronger surface-enhanced Raman scattering (SERS) signal of the nontotally symmetric (b2) vibrational modes of PATP molecules than Au nanoparticles alone, which is attributed to the chemical enhancement effect of the ZnO layer which is greatly excited by the localized surface plasmon resonance (LSPR) of Au cores. Further, the mechanism of the LSPR-enhanced charge transfer (CT) effect has been proved by the SERS spectra of PATP molecules excited using different laser sources from 325 to 785 nm. Moreover, the photocatalytic experimental results indicated that Au–ZnO hybrid nanoparticles are promising as biologically compatible and recyclable SERS-active platforms for different molecular species.

•DSSCs based on low-cost sulfur-doped porous carbon (S-PC) counter electrodes are fabricated.•S doping can significantly enhance the charge-transfer ability toward iodide reduction.•S-PC electrode shows a comparable photovoltaic performance with Pt electrode.•Our work provides a new way in making high-efficient but low-cost DSSCs.In this study, we demonstrate a high performance of sulfur-doped porous carbon (S-PC) as metal-free low-cost counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The S-PC material is synthesized by using pitch as carbon source and basic magnesium sulfate (BMS) whiskers as both template and S source. The doped sulfur is mainly present in the C–S–C configuration. The enhanced electrocatalytic performance can be attributed to the S atoms doped into the carbon framework which has large effective surface areas due to their porous or rough morphology. Therefore, it enhances the asymmetry of the atomic charge density in C atoms, leading to a large number of reduction sites and low charge transfer resistance. The S-PC significantly enhances the performance compared to the pure porous carbon (PC) due to the lower charge-transfer resistance. The DSSC with S-PC as the CE exhibits a high conversion efficiency of 6.97% which is comparable to that of the traditional Pt CE (7.28%).

In this study, we report modification of few-layer graphene grown by chemical vapour deposition via nitrogen plasma ion irradiation and its application as counter electrodes in bifacial dye-sensitized solar cells (DSSCs). The incorporation of nitrogen (N) atoms and defects are confirmed by X-ray photoelectron spectroscopy and Raman spectroscopy. Electrochemical impedance spectroscopy measurement reveals that the charge transfer resistance of graphene for triiodide reduction shows a decrease with increasing plasma treatment time, which is attributed to the increase of catalytic sites. The energy conversion efficiency of 3.12% is obtained when using the N-doped graphene films as counter electrodes, which is nearly 3 times higher than that of the pristine graphene films in DSSCs. More importantly, the DSSCs based on N-doped graphene CEs show much higher ηrear/ηfront ratio and better long-term stability than that based on Pt CEs. These results reveal the promising potential of this transparent N-doped graphene CEs in low cost and effective bifacial DSSCs.

We report a simple approach for fabricating flexible, free-standing, catalytic films composed of graphene oxide/carbon nanotube–Au (GO/CNT–Au) composites by using a one-pot chemical reduction route. The catalyst film was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and Raman spectroscopy to investigate the morphology, crystalline structure of the composites. The layered structure of the catalyst film is porous, flexible and exhibits excellent catalytic property in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) reaction. This study demonstrate here for simple yet effective synthesis of catalyst film with a number of advantages such as good strength, high stability, easy operation, and good reusability with minimal loss of activity.

In this work, we demonstrate that the presence of PdO nanoparticles can significantly enhance the catalytic performance of Pd catalysts for the reduction of 4-nitrophenol (4-NP). Heterogeneous Pd/PdO nanoparticles supported on an oxidized multi-walled carbon nanotube (OCNTs) catalyst is prepared by a one-pot gas–liquid interfacial plasma (GLIP) method with the precursor Pd(NO3)2·2H2O. The Pd/PdO catalysts with uniform size distribution exhibit remarkable catalytic activity during the reduction of 4-NP to 4-aminophenol (4-AP) in neat water at room temperature. The turnover frequency (TOF) value is up to 750 h−1, which shows much higher catalytic activity than single Pd nanoparticles supported on OCNTs. Our results indicate that the Pd/PdO catalyst can be readily recovered and reused 10 times.

•Synthesis of three-dimensional nanoporous graphene at low temperature.•Nanoporous graphene has special structure and morphology compared with planar graphene.•Nanoporous graphene can be used as a substrate for surface-enhanced Raman scattering.We synthesized 3D nanoporous graphene by a chemical vapour deposition method with nanoporous copper as a catalytic substrate, and we show that the resulting nanoporous graphene has the same average pore size and the same morphology as the underlying copper substrate. Our surface-enhanced Raman scattering (SERS) investigation indicates that the nanoporosity of graphene significantly improves the SERS efficiency of graphene as a substrate, which is better than that of planar single-layer graphene substrates.

We report the green synthesis of silanols from hydrosilanes in high yields by using oleylamine (OA) stabilized gold nanoparticles (AuNPs) supported on oxidized multi-walled carbon nanotubes (o-CNTs) as catalysts in H2O. The Au catalyst can be easily synthesized by a one-pot gas–liquid interfacial plasma method, and the catalyst exhibited much more remarkable catalytic activity in the oxidation of various organosilanes by using water as the solvent compared with other organic solvents (for example THF, ethyl acetate, and acetone), which is very important for organic synthesis from both the standpoint of practical reasons and an economic perspective. The Au catalyst can be readily recovered and reused without any loss of catalytic activity. In addition, our findings indicate that o-CNTs and OA are the key components of the catalyst in which the o-CNT support makes the hybrid materials hydrophilic, and the OA stabilizer makes the hybrid materials lipophilic, resulting in the high activity of the catalyst in H2O.

We report a simple procedure for fabricating flexible, free-standing, and magnetic film of GO/CNT–Fe3O4 composites by using a one-pot co-precipitation in situ growth route. Characterizations including X-ray diffraction, Raman spectroscopy, superconducting quantum interference device magnetometry, scanning electron microscopy and transmission electron microscopy have been carried out to investigate the morphology, crystalline structure and magnetic properties of the composites. The layered structure of the as-prepared composites is porous and superparamagnetic. The GO/CNT–Fe3O4 composites exhibit excellent microwave absorbing properties in the range of 2–18 GHz and are expected to be promising candidates as microwave absorbing materials.

Single- and double-walled carbon nanotubes (SWCNTs and DWCNTs) have been controllably synthesized by an arc discharge in different atmosphere using petroleum coke as carbon source. The morphology and properties of two kinds of carbon nanotubes (CNTs) synthesized with Fe as catalyst were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, UV–visible spectroscopy, inductively coupled plasma optical emission spectrometer, thermogravimetric analysis and infrared spectroscopy. In the He gas atmosphere only SWCNTs were found to be synthesized by arc discharge in contrast to the case in Ar gas atmosphere in which only DWCNTs were formed, In addition, properties of solar cells based on both kinds of CNTs and n-type Si are examined under illumination of light emission diode (LED). It is found that the performance of solar cells depends significantly on the type of CNTs, i.e., SWCNTs-based solar cells show better performance under LED illumination with wavelengths in the range of 400–940 nm than the case of DWCNTs which exhibit high performance under illumination of the 1310 nm infrared light.

We report that graphene films with thickness ranging from 1 to 7 layers can be controllably synthesized on the surface of polycrystalline copper by a chemical vapour deposition method. The number of layers of graphene is controlled precisely by regulating the flow ratio of CH4 and H2, the reaction pressure, the temperature and the reaction time. The synthesized graphene films were characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction and Raman spectroscopy. In addition, the graphene films transferred from copper to other substrates are found to have a good optical transmittance that makes them suitable for transparent conductive materials.

We have developed an environmentally-friendly method for the synthesis of Pd nanoparticle (Pd NPs) decorated different graphene supports, and the morphology and structure of the hybrids are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and elemental mappings. Four hybrid materials based on graphene foam (GF), oxidized graphene foam (OGF), graphene oxide (GO) and reduced graphene oxide (RGO) have been used to catalyze Heck coupling reactions, and the effect of support on the activity of the hybrid material has been studied. Our results have revealed that Pd NP decorated OGF (Pd/OGF) is the most active catalyst, showing better performance than the commercial Pd/C catalyst. More importantly, the Pd/OGF catalyst has been successfully used for one-pot synthesis of dibenzyls with different aryl bromides and olefins, which has simplified the separation and purification process and realized a green organic synthesis process.

In this study, a three-dimensional CuO nanowire (NW) network decorated with N-doped graphene (NG/CuO) was fabricated by a method of thermal oxidation combined with hydrothermal and ion implantation. The morphological investigation of products was analyzed by field emission scanning electron microscopy (FESEM), which confirmed that the synthesized CuO is wire-shaped and obtained in a high density and large quantity. Meanwhile, it is found that the graphene was successfully wrapped on the surface of the CuO NWs. Subsequently, N ions were injected into graphene by using a plasma method. The detailed structural, compositional and optical characterizations of the synthesized NG/CuO are characterized by X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) which have collectively confirmed that the obtained sample is highly crystalline CuO NWs decorated with N doped graphene. It is found that NG/CuO demonstrates better photocatalytic activity than the pristine graphene decorated CuO NW (Gra/CuO) and much higher activity than that of the pure CuO NW, which shows a good reproducibility and could be further enhanced by adding H2O2. The formation of a heterojunction between the N-doped graphene and CuO can efficiently avoid the combination of photogenerated carriers, which contributes to the enhancement of its photocatalytic activities.

We report an environmentally-friendly approach to the synthesis of hybrids based on porous graphene and metal nanoparticles. The nitrogen-doped porous graphene (N-PG) and Pd nanoparticles decorated N-PG (Pd/N-PG) was synthesized by a plasma method. The N-PG was characterized by X-ray photoelectron spectroscopy and Raman spectroscopy, and the results clearly indicate that the amount of nitrogen doping was 6.65 wt%. The synthesized Pd/N-PG hybrid materials were confirmed by transmission electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy mapping. The hybrid material based on Pd/N-PG as a new catalyst was applied in Suzuki reaction. This catalyst offers a number of advantages such as high stability, easy removal from the reaction mixture and reusability with minimal loss of activity, showing better performance than the well-known commercial Pd/C catalyst.

•Synthesis of three-dimensional graphene with petroleum asphalt as carbon source.•The planar aromatic rings in asphalt involved into the formation process of graphene.•Our work opens up a new avenue in economically converting asphalt into high value-added carbon materials.The synthesis of three-dimensional (3D) graphene with petroleum asphalt as a carbon source by chemical vapor deposition on a Ni foam substrate has been studied. The morphology and properties of three-dimensional graphene synthesized from asphalt were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction. The results demonstrate that most of as-prepared 3D graphene foams have 2–5 layers, and small amounts of them have sheets more than 5 layers. The hydrocarbon fragments in asphalt consist of planar aromatic ring structures are considered to play a key role during the formation of 3D graphene. The results demonstrate that asphalt is one of the suitable starting carbon sources for making 3D graphene networks.

•The potential of P-G with rationally designed structure in DSSCs is explored.•P-G possesses huge surface area, enriched open sites and suitable pore structure.•P-G exhibits comparable performance with that of Pt electrode.Phosphorus-doped porous graphene nanosheet with a large specific surface area (1627.8 m2 g−1) was prepared via chemical vapour deposition (CVD) with porous Mg3(PO4)2 as phosphorus (P) source and template, then it was applied as the counter electrode (CE) for dye-sensitized solar cell (DSSC). Due to the enhanced intrinsic catalytic activity induced by P doping, along with abundant open edge sites originated from the unique porous nanosheet, DSSCs with P doped porous graphene nanosheets CEs exhibited a high power conversion efficiency of 7.08%, which was comparable to that of DSSCs with Pt CEs.Figure optionsDownload full-size imageDownload high-quality image (196 K)Download as PowerPoint slide

Exploiting highly active and stable counter electrodes (CEs) has been a persistent challenge for the practical application of dye-sensitized solar cells (DSSCs). Herein, we present an edge-enhanced modification to fabricate nitrogen doped holey graphene (NHG) by rationally employing N2 plasma treatment at the exposed edge sites of holey graphene. The as-synthesized NHG exhibits a highly conductive and unique holey scaffold with a large surface area, along with abundant edge-induced topological defects and nitrogen dopants. Benefiting from such unique features, NHG exhibits outstanding electrocatalytic activity and high electrochemical stability for the I−/I3− redox reaction. Furthermore, density functional theory calculations are performed to further elucidate the underlying mechanism behind this encouraging performance, in particular the effect of edge-induced topological defects. The DSSCs based on NHG CEs display a power conversion efficiency of 9.07%, which is even superior to that of Pt (8.19%). These results strongly indicate possibilities for the large-scale fabrication of low-cost and metal-free NHG materials for DSSCs with an I-complex redox couple.

We report a simple procedure for fabricating flexible, free-standing, and magnetic film of GO/CNT–Fe3O4 composites by using a one-pot co-precipitation in situ growth route. Characterizations including X-ray diffraction, Raman spectroscopy, superconducting quantum interference device magnetometry, scanning electron microscopy and transmission electron microscopy have been carried out to investigate the morphology, crystalline structure and magnetic properties of the composites. The layered structure of the as-prepared composites is porous and superparamagnetic. The GO/CNT–Fe3O4 composites exhibit excellent microwave absorbing properties in the range of 2–18 GHz and are expected to be promising candidates as microwave absorbing materials.

A novel heterostructure of TiO2 modified Co3O4 (TiO2/Co3O4) acicular nanowire (NW) arrays has been fabricated in this study, which demonstrates a good performance for ethanol detection at working temperatures as low as 160 °C. Co3O4 NW arrays were first grown on an Al2O3 substrate patterned with an Ag/Pd electrode by a hydrothermal method, and then TiO2 nanoparticles were decorated on the surface of Co3O4 NW arrays by using pulsed laser deposition (PLD). It is found that after decoration of TiO2, the TiO2/Co3O4 NW array sensor exhibits a much higher response to ethanol (Rg/Ra = 65, Rg is the sensor resistance measured in a mixture of target gases and Ra is the resistance measured in air) compared with the pristine Co3O4 NW sensor (Rg/Ra = 25). Importantly, the TiO2/Co3O4 sensor has shown a detection limit as low as 10 ppm, and a good reproducibility. The reason for the enhanced sensing properties of TiO2/Co3O4 is considered to be due to the formation of a p–n junction between the p-type Co3O4 and n-type TiO2.

We report the green synthesis of silanols from hydrosilanes in high yields by using oleylamine (OA) stabilized gold nanoparticles (AuNPs) supported on oxidized multi-walled carbon nanotubes (o-CNTs) as catalysts in H2O. The Au catalyst can be easily synthesized by a one-pot gas–liquid interfacial plasma method, and the catalyst exhibited much more remarkable catalytic activity in the oxidation of various organosilanes by using water as the solvent compared with other organic solvents (for example THF, ethyl acetate, and acetone), which is very important for organic synthesis from both the standpoint of practical reasons and an economic perspective. The Au catalyst can be readily recovered and reused without any loss of catalytic activity. In addition, our findings indicate that o-CNTs and OA are the key components of the catalyst in which the o-CNT support makes the hybrid materials hydrophilic, and the OA stabilizer makes the hybrid materials lipophilic, resulting in the high activity of the catalyst in H2O.