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In this work, we developed a novel hierarchical hybrid nanostructure of reduced graphene oxide (rGO) supported cobalt-doped ZnO nanoparticles (Co-doped ZnO NPs@rGO) via a simple solution-refluxing strategy. The ultrafine CoZn-glycolate nanoparticles precursor was obtained from the alkoxide reaction among ethylene glycol and Co 2+ /Zn 2+ ions absorbed onto GO support. The post-annealing process makes the precursor easily transferred into crystalline Co-doped ZnO NPs@rGO with well-retained morphology and the oxidation state of Co element to be Co 2+ in the final hybrid. When evaluated as an oxygen reduction reaction (ORR) electrocatalyst in an O 2 -saturated 0.1 M KOH solution, the Co-doped ZnO NPs@rGO hybrid with the optimal Co-doping concentration of 0.38 ( i.e. , Co 0.38 Zn 0.62 O NPs@rGO) exhibits highly enhanced ORR electrocatalytic activity compared to the ZnO@rGO composite with an ORR peak potential of 0.74 V ( vs . RHE), an onset potential of 0.90 V, a current density of 3.94 mA cm −2 (at 0.4 V (vs. RHE)) and a nearly four-electron catalytic pathway. The good electrochemical stability and excellent methanol-tolerance capability of the resultant Co 0.38 Zn 0.62 O NPs@rGO hybrid, superior to those of the commercial Pt/C catalyst, further demonstrate its great potential as an efficient ORR electrocatalyst. This work proposes the feasibility of the semiconducting ZnO nanomaterials as novel ORR electrocatalysts via doping active oxygen catalytic element, such as Co 2+ , for the first time.

Developments of nanostructured transition metal dichalcogenides (TMDs) materials as novel electrocatalyst candidates for oxygen reduction reaction (ORR) is a new strategy to promote the developments of non-precious metal ORR catalysts. In this work, a three-dimensional (3D) hybrid of rosebud-like MoSe2 nanostructures supported on reduced graphene oxide (rGO) nanosheets was successfully synthesized through a facile hydrothermal strategy. The prepared MoSe2@rGO hybrid nanostructure showed enhanced electrocatalytic activity for the ORR in alkaline medium compared to that of the pure MoSe2, rGO, and their simple physical mixture, which could benefit from the excellent oxygen adsorption ability of the abundantly exposed active edge sites of the ultrathin MoSe2 layers, the conductivity and aggregation-limiting effect of the rGO platform, as well as the unique 3D rosebud-like architecture of the hybrid material. The electrocatalytic activity of the MoSe2@rGO hybrid towards ORR was comparable to that of commercial Pt/C catalysts. And the promoted reaction was revealed to involve a nearly four-electron-dominated ORR process by analysis of the obtained Koutecky–Levich plots. The scanning electrochemical microscopy (SECM) technique, with the advantages of investigating of the local catalytic activity of samples with high spatial resolution and simultaneously evaluating activities of different catalysts in a single experiment, was further applied to investigate the local ORR electrocatalytic activity of MoSe2@rGO and compare it with those of other catalyst samples through applying different sample potentials. The excellent stability and methanol tolerance of the 3D nanostructured MoSe2@rGO hybrid against methanol further prove the 3D nanostructured MoSe2@rGO hybrid as a promising ORR electrocatalyst in alkaline solution for potential applications in fuel cells and metal–air batteries.

As a member of the ternary metal oxide family, nickel cobaltite is considered as a promising electrode material. This is due to its high theoretical capacity, low diffusional resistance to protons, ease of electrolyte penetration, superior ionic/electronic conductivity and higher electrochemical activity compared to single metallic oxides such as NiO or Co3O4. However, NiCo2O4's relatively low electrical conductivity and its tendency to pulverize due to the volume changes experienced during the charge–discharge process remain a pressing issue to be solved. Here we demonstrate a simple co-precipitation and calcination routine to graft ultrathin NiCo2O4 nanosheets onto highly-ordered mesoporous carbon CMK-3 to form a new mesoporous-nanosheet structure which can accommodate stresses induced by volume changes and provide favourable conducting paths. The material exhibits a high specific surface area and excellent electrochemical performance, which can be ascribed to the ultrathin NiCo2O4 nanosheets and the interconnected conductive network of the mesoporous matrix. The nanosheets and the inner channels of CMK-3 are more beneficial to the diffusion of Li+ while the interconnected conductive network favours fast electron conduction.

Nitrogen-doped graphene quantum dots (N-GQDs) with a size of 2.5–8.5 nm are ultra-uniformly grown in situ on thermally reduced graphene oxide (rGO) and are different from those catalysts fabricated by adding pre-prepared GQDs artificially. N-GQD/rGO shows catalytic activity for the oxygen reduction reaction, which is comparable to that of the Pt/C catalyst, but with better durability and a higher tolerance to the methanol crossover effect. This method might extend the application of N-GQDs in electrocatalysis.

In this work, we demonstrate a step-wise route to build a novel one-dimensional (1D) architecture formed by MoS2 nanosheets and amorphous carbon nanotubes (ACNTs). Being evaluated as an anode material for NIBs, the as-prepared MoS2@ACNT electrode is capable of exhibiting a remarkable reversible capacity of 461 mA h g−1 at a current density of 500 mA g−1 over 150 cycles. Moreover, the coulombic efficiency is almost up to 100% except for the initial few cycles during the whole cycling test. The smart electrode architecture and appropriate synergistic effect between MoS2 and ACNTs are probably responsible for the enhanced electrochemical performance.

A bowl-like carbon backbone supported CoFe2O4 nanoparticles (CoFe2O4 NPs@C) composite was successfully synthesized and used as a high performance anode in lithium batteries. The as-prepared hierarchical structure takes full use of favorable characteristics of individual components down to the nano-sized building block, i.e., high specific capacities of CoFe2O4 NPs and volume change buffering of the bowl-like carbon during charge/discharge cycles. Moreover, the bowl-like carbon architecture sufficiently realizes the space-efficient packing of electrode materials to augment the energy density of batteries. Owing to the efficient combination of individual merits, the CoFe2O4 NPs@C composite presents superior lithium storage properties. Even after 200 cycles at current density of 400 mA h g−1, the as-prepared material exhibits a discharge capacity of 1111.5 mA h g−1.

A step-wise method to synthesize uniform NiCoO 2 nanosheets on carbon nanotubes (CNT) is designed for non-enzyme glucose detection. CNT is coated with a sulfonated polystyrene layer on which the sulfonic acid group is capable to absorb metal ions and induce the growth of nanostructured metal oxides. Owing to the smart architecture and synergistic effect provided by the individual ingredients, the NiCoO 2 @CNT-modified electrode shows fast surface reaction kinetics and excellent catalytic properties towards glucose oxidation. As electrode material for non-enzyme glucose sensors, it displays good analytical performance for glucose with response sensitivity of 1424.41 μA mM −1 , low detection limit of 1.14 μM, satisfactory selectivity and stability.

A novel nanosheet-structured ZnCo 2 O 4 /carbon nanotubes ( i.e. , ZnCo 2 O 4 nanosheets/carbon nanotubes (ZnCo 2 O 4 NSs/CNTs)) composite is successfully synthesized. Its catalytic activity towards oxygen reduction reaction (ORR) in alkaline electrolyte is evaluated by both cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The CV results demonstrate that the ZnCo 2 O 4 NSs/CNTs composite has good ORR catalytic activity, which is better than those of ZnCo 2 O 4 , CNTs, physically mixed ZnCo 2 O 4 and CNTs, and Co 3 O 4 NSs/CNTs. It could attribute to the unique ultrathin nanosheet structure and the synergetic effects of ZnCo 2 O 4 and CNTs. Through recording the ORR currents using a microelectrode above the catalyst sample surfaces with applying different sample potentials, the differences in the local catalytic activities of these catalysts are simultaneously investigated and visualized by SECM. The obtained SECM results agree well with the CV results and also as important complements to the CV measurements. Our work proves the good ORR catalytic performance of the nanosheet-structured ZnCo 2 O 4 /CNTs composite and introduces the SECM technique as a rapid screening method for predicting the ORR catalytic performances of the mixed transition metal oxides hybrids with providing both qualitative and quantitative local catalytic activity information.

The sediment provenance and sedimentary processes of the Parece Vela Basin in the western Pacific during the last ca. 1 Myr were studied based on the analysis of magnetic properties, mineral features, and paleomagnetic ages of core C-P19. The results show that the sedimentary sequence has a lower limit age younger than 1.072 Ma, and the sedimentation process can be divided into two stages with sedimentation rates of 4.0 mm/kyr during ca. 1–0.78 Ma and 3.6 mm/kyr since 0.78 Ma. These sedimentation rates are higher than those in the surrounding area, where the sedimentation rate is generally less than 2 mm/kyr. Taken together with the mineral features and magnetic parameters, these findings show that volcanic sediments eroded from the nearby ridge were transported by currents to the sampling site. These volcanic sediments represent the main source of sediment in the area, with eolian inputs contributing little and nonbiogenic authigenic magnetite accounting for part of the magnetic fraction. The sedimentary environment and sediment provenance have varied during the last approximately 1 million years. During 997–880 ka, volcanic activity increased, and the input of volcanic clasts was high, whereas during 880–443 ka, the sedimentary environment tended to be stable, and the sediment supply decreased. With the increase in volcanic activity in the western Pacific, the sediment input increased again during ca. 443 ka-present.

Exploring highly efficient, cost-effective and stable electrocatalysts for hydrogen evolution reaction (HER) based on naturally abundant elements is of great interest but still a challenge. As is generally known, molybdenum disulfide (MoS2) represents a promising catalyst to replace the state of the-art platinum (Pt) for HER, but an effective way of applying it is yet unknown due to a significant resistance between basal planes. Herein, for the first time, a novel nanostructure with three-dimensional (3D) flower-like defected MoS2 nanosheets grown directly on candle soot by magnetron sputtering with Ni foam as a supporter was developed, and it displayed excellent catalytic activity and stability. On the one hand, the bombardment of Ar ions in the deposition system could effectively etch the inert basal plane, leading to the formation of defects and steps to increase the active edge sites. On the other hand, the resistance of MoS2-based electrocatalysts decreased due to the unique topographic structure and the existence of 1T-MoS2 phase, and also the composite was superhydrophilic which is beneficial to the contact of the solid-liquid interface. The as-prepared 3D MoS2/candle soot/Ni foam (NF + CS + MoS2) composite has an overpotential of 56 mV at the current density of 10 mA cm−2 and a small Tafel slope of 49 mV decade-1. This present work provides new insight into the large-scale production of chemically active MoS2-based catalysts for HER.

Ni3N has been demonstrated as an excellent hydrogen evolution reaction (HER) catalysts that contain active sites with hydrogen adsorption energy. However, the catalytic efficiency of Ni3N is hindered by its inferior electrical conductivity. Herein, we successfully present an effective strategy to boost the H adsorption capability and HER property of Ni3N supported by nickel foam is illustrated. Ni3N nanosheets/nickel foam (Ni3N NSs/NiF) achieve a super low overpotential of 34 mV at 10 mA cm−2 and a fairly small Tafel slope of 54 mV dec−1 in 1 M KOH aqueous solution. Focusing on a self-supported electrode structural design, Ni3N NSs/NiF composites catalysts possess following advantages: (1) abundant exposed edges deriving from thin Ni3N nanosheets; (2) high conductivity of the entire system generating from metallic metal nitrides integrated by metal substrate; (3) synergistic effect between Ni3N and nickel foam, and more effective facets to accelerated reaction kinetics. The developed compound is among the most active electrocatalysts based on non-precious catalysts, which expand and enrich the family of materials suitable as efficient HER catalysts.

Rational design and development of non-precious metal-based electrocatalysts for bifunctional oxygen reduction/evolution reactions (ORR/OER) are essential to realize the dischargeable Zinc-air batteries (ZABs). Herein, for the first time we synthesize CoFe-alloy nanoparticles enveloped by N, P co-doped carbon nanotubes (NPMC/CoFe), through a simple route by pyrolyzing dicyandiamide complex in the presence of phytic acid. The obtained electrocatalysts possess excellent ORR (a half wave potential of 0.896 V in 0.1 M KOH) and OER (η10 mA cm-2 = 310 mV in 1 M KOH) performance, respectively. The liquid-state ZABs based on the NPMC/CoFe air-cathode demonstrates a high peak power density of 146.34 mW cm−2 and excellent durability. Specifically, flexible and button-like ZABs with impressive performances are both realized, which could power light-emitting diodes. This work offers an attractive approach to develop the nonprecious metal-based ORR/OER catalysts, and modulators for the design of performance oriented electrocatalysts for wider electrochemical energy applications.

Engineering heterojunction is an underlying strategy to develop remarkable electrocatalysts for carbon dioxide (CO2) reduction due to its ability to tune electronic properties by interfacial cooperation. Herein, we report a novel type of cube-like Zn2SnO4/SnO2 heterostructure catalyst for CO2 reduction through a simple co-precipitation process. The high-quality heterostructures with band alignment promote interfacial charge transfer from Zn2SnO4 to SnO2, achieving the electronic modulation of Zn2SnO4/SnO2 for reducing the kinetic barriers of CO2 reduction. Density functional theory further reveals that Zn2SnO4/SnO2 allows HCOO* intermediate favorably stabilizing on its surface through improved hydrogen coverage effect comparing to pure Zn2SnO4 or SnO2. The hybrid catalyst presents satisfactory CO2 reduction properties with a stable HCOOH selectivity of 77% during 24 h at −1.08 V vs. RHE. This study provides a new heterostructure modeling and general methodology for electronic modulation and electrocatalysts development for high-performance CO2 reduction.

Bowl-like hybrid structures have been designed and fabricated by anchoring NiO nanosheets on flat carbon hollow particles. When evaluated as an anode material for lithium-ion batteries, these unique NiO/carbon hybrid particles exhibit superior lithium storage properties in terms of high capacity, long term cycling stability and excellent rate capability.

Nitrogen containing carbon layer-coated carbon nanotubes (CNx-CNTs) was prepared as the support for platinum nanoparticles (Pt NPs) and their enhanced properties for electrochemical biosensor has been demonstrated in this paper. The CNx-CNTs were obtained from pyrolysis of polydopamine-wrapped CNTs, which were synthesized by a single deposition process based on the oxidative self-polymerization of dopamine on CNTs. It is found that Pt NPs are deposited on the surface of the CNx-CNTs (Pt/CNx-CNTs) with highly dispersion and small particle size (with an average diameter of 1.7 ± 0.3 nm). Compared to the nitrogen-free CNTs supported Pt NP composite (Pt/CNTs), the Pt/CNx-CNTs modified glassy carbon (GC) electrode exhibits superior electrocatalytic performance towards the oxidation of hydrogen peroxide (increase by about 55% of response current). Taking glucose oxidase (GOD) as the model, the proposed amperometric enzyme biosensor based on the Pt/CNx-CNTs shows excellent analytical characteristics to glucose detection, such as excellent sustainability in large range of pH values, high sensitivity (66.51 μA (mmol dm−3)−1 cm−2), wide linear range (0.01-6.1 mmol dm−3) and low detection limit (0.4 μmol dm−3).

Fe-N/C composites are considered one of the most promising non-precious-metal electrocatalysts for oxygen reduction reaction (ORR). In this paper, we fabricate a novel and efficient carbon nanotube (CNT)-supported Fe-N/C composite catalyst, via the surface-self-polymerization of polydopamine and then the incorporation with Fe species on CNTs, followed by the pyrolysis process. The obtained catalyst demonstrates excellent electrocatalytic performance towards ORR in alkaline media. The modification of Fe-incorporated nitrogen-rich-carbons (Fe-CNx) on CNTs lowers the ORR half-wave-potential by ∼190 mV, giving this catalyst with an onset ORR potential of 0.95 V (versus reversible hydrogen electrode (RHE)), a half-wave potential of 0.82 V (versus RHE), and the limiting current density of 5.39 mA cm-2 in 0.1 M KOH. The performance of the as-prepared catalyst is comparatively better than the commercially available Pt/C in terms of positive half-wave potential and larger limiting current, superior durability, and higher tolerance to the methanol.

A unique ionic liquid polymer (ILP)-assisted method is developed for preparation of PdPt nanoparticles (NPs) on carbon nanotubes (CNTs). Due to its intrinsic hydrophilicity and regularly arranged imidazolium cationic functional groups, ILP induces the growth of uniform PdPt NPs with an average size of 3.5 ± 0.5 nm on CNTs. The cyclic voltammetry and amperometric studies indicated that the resulting PdPt NP/ILP–CNT nanohybrids have larger electrochemical surface area, better electrocatalytic performance, and higher stability towards the formic acid oxidation compared to NPs supported on the pristine CNTs. The excellent electrocatalytic performance is mainly contributed to the smaller particle size and more uniform dispersion of PdPt NPs. These results imply that PdPt NP/ILP–CNT nanohybrids are promising electrocatalytic material for formic acid oxidation. This work may also explore a universal approach to fabricate superior framework of metal nanocrystalline on CNTs for broad applications in energy systems and sensing devices.

In this paper, we report a facile approach to the synthesis of one-dimension (1D) hierarchical NiCoO2 nanosheets (NSs)@amorphous CNT composites based on the templates and carbon source of polymeric nanotubes (PNTs). Importantly, these sulfonated PNTs can also be used to prepare many other functional 1D metal oxides@amorphous CNT nanostructures, such as TiO2, SnO2, CoO and NiO, etc. Due to the outstanding nanostructures and the synergistic effects of the NiCoO2 NSs and amorphous CNTs, an ultrahigh discharge capacity of 1309 mA h g−1 is delivered by the NiCoO2@CNT composites, even after 300 cycles at a current density of 400 mA g−1. The favorable improvements of the NiCoO2 based lithium-ion batteries (LIBs) reported in this work illustrate that the 1D amorphous carbon matrix offers significant benefits for high-capacity metal oxide anode nanomaterials.

Exploring efficient metal-free electrocatalysts for oxygen reduction reactions (ORR) will have a great impact on the field of fuel cells and metal-air batteries. In this paper, we report a simple and efficient routine to coat ordered mesoporous carbon (CMK-3) with nitrogen-doped carbon via pyrolysis of the surface-self-polymerized polydopamine. The optimized CMK-3 catalyst with a coating of nitrogen-doped carbon demonstrates excellent electrocatalytic activity towards ORR in alkaline media. The coating procedure under optimized conditions lowers the ORR half-wave-potential by 80 mV, giving a genuine metal-free catalyst with an onset ORR potential of 0.96 V (vs reversible hydrogen electrode (RHE)) and half-wave potential of 0.83 V (vs RHE) in 0.1 M KOH, which is much better than other carbon material-based catalysts (such as carbon nanotubes and their composites). The performance of this surface-nitrogen-rich CMK-3 catalyst is also superior to that of N-doped ordered mesoporous carbon synthesized by means of the 'nanocasting' technique. Furthermore, the as-prepared catalyst performs comparably in terms of activity, superior durability, and higher tolerance to methanol compared with commercially available Pt/C.

It still remains very challenging to design proper heterostructures to enhance the electrochemical performance of transition metal oxide-based anode materials for lithium-ion batteries. Here, we synthesized the NiCoO2 nanosheets@SnO2 layer heterostructure supported by amorphous carbon nanotubes (ACNTs) which is derived from polymeric nanotubes (PNTs) by a stepwise method. The inner SnO2 layer not only provides a considerable capacity contribution but also produces the extra Li2O to promote the charge process of NiCoO2 and thus results in a rising cycling performance. Combining with the contribution of ACNTs backbone and ultrathin NiCoO2 nanosheets, the specific capacities of these one-dimensional nanostructures show an interesting gradually increasing trend even after 100 cycles at 400 mA g(-1) with a final result of 1166 mAh g(-1). This approach can be an efficient general strategy for the preparation of mixed-metal-oxide one-dimensional nanostructures and this innovative design of hybrid electrode materials provides a promising approach for batteries with improved electrochemical performance.

Dopamine, a sustainable and cheap raw material, was selected as the carbon and nitrogen sources to synthesize hollow nitrogen-doped carbon microspheres (HNCMS). The obtained HNCMS were used as a non-noble-metal electrocatalyst for oxygen reduction in alkaline solution and show high electrocatalytic activity, excellent long-term stability, and tolerance to crossover effect of methanol.

A novel one-dimensional (1-D) caterpillar-like manganese dioxide-carbon (MnO(2)-C) nanocomposite has been synthesized by a direct redox reaction between carbon nanotubes (CNTs) and permanganate ions for the first time. The as-prepared nanostructured MnO(2)-C composite mainly consisting of ε-MnO(2) nanoflakes had a unique microstructure, high specific surface area (200 m(2) g(-1)) and favourable conductivity. The nanostructured MnO(2)-C composite, added as a modification to the glassy carbon (GC) electrode via a direct electrochemical co-deposition process with a chitosan hydrogel, was found to exhibit excellent catalytic activity toward L-cysteine electro-oxidation because the specific interaction between the -SH group of L-cysteine and solid MnO(2) occurred to form surface complexes. A determination of L-cysteine at the MnO(2)-C/chitosan/GC (MnO(2)-C/chit/GC) electrode was carried out by amperometric measurement. Under the optimum experimental conditions, the detection response for L-cysteine was fast (within 7 s). The logarithm of catalytic currents shows a good linear relationship with that of the L-cysteine concentration in the range of 0.5-680 μM (R = 0.9986), with a low detection limit of 22 nM. The MnO(2)-C/Chit/GC electrode exhibited excellent stability (without any decrease of the response signal after 1 month) and admirable resistance against interference like glutathione and other oxidizable amino acids (tryptophan, tyrosine, L-lysine and methionine).

A new amperometric glucose biosensor has been developed based on platinum (Pt) nanoparticles/polymerized ionic liquid-carbon nanotubes (CNTs) nanocomposites (PtNPs/PIL-CNTs). The CNTs was functionalized with polymerized ionic liquid (PIL) through directly polymerization of the ionic liquid, 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIM]BF 4 ), on carbon nanotubes and then used as the support for the highly dispersed Pt nanoparticles. The electrochemical performance of the PtNPs/PIL-CNTs modified glassy carbon (PtNPs/PIL-CNTs/GC) electrode has been investigated by typical electrochemical methods. The PtNPs/PIL-CNTs/GC electrode shows high electrocatalytic activity towards the oxidation of hydrogen peroxide. Taking glucose oxidase (GOD) as the model, the resulting amperometric glucose biosensor shows good analytical characteristics, such as a high sensitivity (28.28 μA mM −1 cm −2 ), wide linear range (up to 12 mM) and low detection limit (10 μM).

The Boron-doped carbon nanotubes (BCNTs) modified glassy carbon (GC) electrode was obtained simply and used for highly selective and sensitive determination of dopamine (DA). Comparing with the bare GC and CNTs/GC electrodes, the BCNTs have higher catalytic activity toward the oxidation of DA and ascorbic acid (AA). Moreover, the voltammetric peaks of AA and DA were separated enough (ca. 238 mV) at the BCNTs/GC electrode, which is superior to that at the CNTs/GC electrode (ca. 122 mV). Thus, the selective determination of DA was carried out successfully in the presence of AA. A wide concentration range (2.0 × 10 −8 –7.5 × 10 −5 M) and low detection limit (1.4 nM, S/N = 3) for the DA detection were obtained. The possibility of the BCNTs/GC electrode for the determination of DA in human blood serum has also been evaluated. The advantageous properties of this electrode for the DA determination lie in its excellent catalytic activity, selectivity and simplicity. The more edge plane sites presented on the BCNTs surface were partially responsible for its good analytical behavior.

Doped carbon nanotubes are now extremely attractive and important nanomaterials in bioanalytical applications due to their unique physicochemical properties. In this paper, the boron-doped carbon nanotubes (BCNTs) were used in amperometric biosensors. It has been found that the electrocatalytic activity of the BCNTs modified glassy carbon (GC) electrode toward the oxidation of hydrogen peroxide is much higher than that of the un-doped CNTs modified electrode due to the large amount of edge sites and oxygen-rich groups located at the defective sites induced by boron doping. Glucose oxidase (GOD) was selected as the model enzyme and immobilized on the BCNTs modified glassy carbon electrode by entrapping GOD into poly( o -aminophenol) film. The performance of the sensor was investigated by electrochemical methods. At an optimum potential of +0.60 V and pH 7.0, the biosensor exhibits good characteristics, such as high sensitivity (171.2 nA mM −1 ), low detection limit (3.6 μM), short response time (within 6 s), satisfactory anti-interference ability and good stability. The apparent Michaelis–Menten constant ( K m app ) is 15.19 mM. The applicability to the whole blood analysis of the enzyme electrode was also evaluated.

Pt/MgO/CNT hybrid electrocatalysts for ethanol electrooxidation were simply prepared in this paper. The micrograph and elemental compositions of Pt/MgO/CNT catalysts were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The electrocatalytic properties of the Pt/MgO/CNT catalyst for ethanol oxidation have been investigated by cyclic voltammetry in 1.0 mol L-1 CH3CH2OH and 1.0 mol L-1 KOH aqueous solution. The effect of the content of MgO on the electrocatalytic activity of the Pt/MgO/CNT catalyst was also investigated. Under the same Pt loading mass and experimental conditions for ethanol oxidation, the Pt/MgO/CNT catalyst shows higher electrocatalytic activity than the Pt/CNT catalyst. Additionally, the Pt/MgO/CNT catalyst possesses a good antipoisoning ability.

To observe blood B-type natriuretic peptide (BNP) level changes and the clinical implications in different periods and different cardiac pacing modes, the BNP levels of 105 patients with permanent cardiac pacing were assayed before pacemaker implantation and 1 day, 1 week, 1 month, 3 months, 6 months, and 9 months postoperatively. BNP level changes were compared in different periods and during different pacing modes. DDD(R) pacing mode was performed in 32 patients for 9 months and then changed to AAI(R) and VVI(R) pacing modes for 2 months, respectively. BNP levels were assayed during three different pacing modes. BNP levels did not change at any time with any pacing mode in patients with New York Heart Association (NYHA) heart functional class I to II before pacemaker implantation, however, BNP levels did change significantly with physiologic pacing mode and nonphysiologic pacing mode in patients with NYHA heart functional class III to IV before pacemaker implantation. BNP levels during physiologic pacing mode decreased significantly while it increased during nonphysiologic pacing mode. BNP levels were the lowest in AAI(R) pacing and the highest in VVI(R) pacing among the three pacing modes. The BNP level in DDD(R) pacing was between that for AAI(R) pacing and VVI(R) pacing. The results indicate that physiologic pacing should first be chosen in patients with bradycardia and congestive heart failure (CHF), and that AAI(R) was the best pacing mode if atrioventricular conduction function was normal.

Ultrathin cobalt ferrite nanosheets have been successfully assembled on the surface of reduced graphene oxide (rGO) via only adjusting the volume ratio of ethanol and deionized (DI) water and a post calcination treatment. The perpendicular ultrathin cobalt ferrite nanosheets supported by rGO sheets (CoFe2O4 NSs@rGO) can be obtained when the volume ratio of ethanol and DI water is 10:30. Correspondingly, the hierarchical porous films covering the total rGO sheets will be formed nanosheets. When evaluated as the electrodes for lithium ion batteries (LIBs) and supercapacitors (SCs), the resultant CoFe2O4 NSs@rGO hybrids exhibit highly enhanced electrochemical performance. Even after 200 charge-discharge cycles at 400 mA g-1, the electrodes as the anode material for LIBs still exhibit a reversible discharge capacity of 835.6 mAh g-1. In addition, this electrode for SCs also exhibits specific capacitance of ca 1120 F g-1 after 3000 cycles. These superior results imply that CoFe2O4 NSs with novel hybrid structure of rGO could potentially lead to an excellent electrochemical performance for energy storage.

Boron-doped carbon nanotubes (BCNTs) as a novel carbon nanomaterial have higher catalytic activity. Electroanalysis of dihydronicotinamide adenine dinucleotide (NADH) based on the BCNTs modified electrode has been investigated. Comparing with the bare glassy carbon (GC) and carbon nanotubes (CNTs)/GC electrodes, the BCNTs/GC electrode allowed highly sensitive amperometric detection of NADH at the lower applied potential, and minimization of surface contamination. Therefore, BCNTs are useful and promising material for the detection of NADH and are attractive for dehydrogenase-based amperometric biosensor or other analytical applications. Keywords: Boron-doped carbon nanotubes (BCNTs), Dihydronicotinamide adenine dinucleotide (NADH), Electroanalysis, Catalytic activity, Surface contamination

Nitrogen doping has been demonstrated to play a crucial role in controlling the electronic properties of carbon-based composites. In this paper, nitrogen-doped carbon coated γ-Fe2O3 (NC@γ-Fe2O3) composite was successfully fabricated through a facile and high-yield strategy, including a hydrothermal reaction process for porous γ-Fe2O3 and a subsequent coating of nitrogen-doped carbon by using dopamine as precursor. The resulting composite combines the superior properties of porous Fe2O3 and heteroatom-doped conductive carbon layer derived from polydopamine. When used as the anode material of the lithium-ion battery, the as-prepared NC@γ-Fe2O3 composite exhibits excellent lithium storage properties in terms of high capacity, stable cycling performance (869.6 mAh g(-1) at the current density of 0.5 A g(-1) after 150 cycles) and excellent rate capability.

Motivated by the use of ionic liquids (ILs) as green replacers of traditional electrolytes, a mechanistic study has been systematically conducted to comprehend various design principles responsible for electrochemical profiling of redox-active species in ILs. The full spectrum of properties associated with ILs is exploited to assess the viability of this platform, thus revealing the correlation between the redox properties and the physiochemical parameters of the species involved. This includes the evaluation of (1) the variation of redox responses toward analytes with similar molecular structures or functionalities of ILs, (2) the influence in terms of physical criteria of the system such as viscosity and conductivity as well as chemical structure of ILs, and (3) the sustainability in harsh conditions (high temperature or humidity) and interferences. The principle is exemplified via trinitrotoluene (TNT) and dinitrotoluene (DNT) with inherent redox activity as analytes and IL membranes as solvents and electrolytes using glassy carbon (GC) electrodes. A discrete response pattern is generated that is analyzed through linear discriminant analysis (LDA) leading to 100% classification accuracy even for the mixture of analytes. Quantitative analysis through square wave voltammetry (SWV) gave rise to the detection limits in liquid phase of 190 and 230 nM for TNT and DNT, respectively, with a linear range up to 100 μM. Gas-phase analysis shows strong redox signals for the estimated concentrations of 0.27 and 2.05 ppm in the gas phase for TNT and DNT, respectively, highlighting that ILs adopt a role as a preconcentrator to add on sensitivity with enhanced selectivity coming from their physiochemical diversity, thus addressing the major concerns usually referred to most sensor systems.

Based on the excellent physicochemical properties of boron-doped carbon nanotubes (BCNTs), the electrochemical analysis of four free DNA bases at the BCNTs modified glassy carbon (GC) electrode was investigated. Herein, the BCNTs/GC electrode exhibited remarkable electrocatalytic activity towards the oxidation of purine bases (guanine (G), adenine (A)). More significantly, the direct oxidation of pyrimidine bases (thymine (T), cytosine (C)) was realized. It may be due to that BCNTs have the advantages of high electron transfer kinetics, large surface area, prominent antifouling ability and electrode activity. On basis of this, a novel and simple strategy for the determination of G, A, T and C was proposed. The BCNTs/GC electrode showed high sensitivity, wide linear range and capability of detection for the electrochemical determination of G, A, T, and C. On the other hand, the electrochemical oxidation of quaternary mixture of G, A, T, and C at the BCNTs/GC electrode was investigated. It was obtained that the peak separation between G and A, A and T, T and C were large enough for their potential recognition in mixture without any separation or pretreatment. The BCNTs/GC electrode also displayed good stability, reproducibility and excellent anti-interferent ability. Therefore, it can be believed that the BCNTs/GC electrode would provide a potential application for the electrochemical detection of DNA in the field of genetic-disease diagnosis.

Hollow nitrogen-doped carbon microspheres (HNCMS) as a novel carbon material have been prepared and the catalytic activities of HNCMS-modified glassy carbon (GC) electrode towards the electro-oxidation of uric acid (UA), ascorbic acid (AA) and dopamine (DA) have also been investigated. Comparing with the bare GC and carbon nanotubes (CNTs) modified GC (CNTs/GC) electrodes, the HNCMS modified GC (HNCMS/GC) electrode has higher catalytic activities towards the oxidation of UA, AA and DA. Moreover, the peak separations between AA and DA, and DA and UA at the HNCMS/GC electrode are up to 212 and 136 mV, respectively, which are superior to those at the CNTs/GC electrode (168 and 114 mV). Thus the simultaneous determination of UA, AA and DA was carried out successfully. In the co-existence system of UA, AA and DA, the linear response range for UA, AA and DA are 5–30 μM, 100–1000 μM and 3–75 μM, respectively and the detection limits (S/N = 3) are 0.04 μM, 0.91 μM and 0.02 μM, respectively. Meanwhile, the HNCMS/GC electrode can be applied to measure uric acid in human urine, and may be useful for measuring abnormally high concentration of AA or DA. The attractive features of HNCMS provide potential applications in the simultaneous determination of UA, AA and DA.

Polymerized ionic liquid-wrapped carbon nanotubes (PIL-CNTs) were firstly designed for direct electrochemistry and biosensing of redox proteins. The CNTs were coated successfully with polymerized ionic liquid (PIL) layer, as verified by transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. The PIL-CNTs were dispersed better in water and showed superior electrocatalysis toward O(2) and H(2)O(2) comparing to pristine CNTs and the mixture of IL monomer and CNTs. With glucose oxidase (GOD) as a protein model, the direct electrochemistry of the redox protein was investigated on the PIL-CNTs modified glassy carbon (GC) electrode and excellent direct electrochemical performance of GOD molecules was observed. The proposed biosensor (GOD/PIL-CNTs/GC electrode) displayed good analytical performance for glucose with linear response up to 6mM, response sensitivity of 0.853 microA mM(-1), good stability and selectivity.

To observe blood B-type natriuretic peptide (BNP) level changes and the clinical implications in different periods and different cardiac pacing modes, the BNP levels of 105 patients with permanent cardiac pacing were assayed before pacemaker implantation and 1 day, 1 week, 1 month, 3 months, 6 months, and 9 months postoperatively. BNP level changes were compared in different periods and during different pacing modes. DDD(R) pacing mode was performed in 32 patients for 9 months and then changed to AAI(R) and VVI(R) pacing modes for 2 months, respectively. BNP levels were assayed during three different pacing modes. BNP levels did not change at any time with any pacing mode in patients with New York Heart Association (NYHA) heart functional class I to II before pacemaker implantation, however, BNP levels did change significantly with physiologic pacing mode and nonphysiologic pacing mode in patients with NYHA heart functional class III to IV before pacemaker implantation. BNP levels during physiologic pacing mode decreased significantly while it increased during nonphysiologic pacing mode. BNP levels were the lowest in AAI(R) pacing and the highest in VVI(R) pacing among the three pacing modes. The BNP level in DDD(R) pacing was between that for AAI(R) pacing and VVI(R) pacing. The results indicate that physiologic pacing should first be chosen in patients with bradycardia and congestive heart failure (CHF), and that AAI(R) was the best pacing mode if atrioventricular conduction function was normal.

To observe blood B-type natriuretic peptide (BNP) level changes and the clinical implications in different periods and different cardiac pacing modes, the BNP levels of 105 patients with permanent cardiac pacing were assayed before pacemaker implantation and 1 day, 1 week, 1 month, 3 months, 6 months, and 9 months postoperatively. BNP level changes were compared in different periods and during different pacing modes. DDD(R) pacing mode was performed in 32 patients for 9 months and then changed to AAI(R) and VVI(R) pacing modes for 2 months, respectively. BNP levels were assayed during three different pacing modes. BNP levels did not change at any time with any pacing mode in patients with New York Heart Association (NYHA) heart functional class I to II before pacemaker implantation, however, BNP levels did change significantly with physiologic pacing mode and nonphysiologic pacing mode in patients with NYHA heart functional class III to IV before pacemaker implantation. BNP levels during physiologic pacing mode decreased significantly while it increased during nonphysiologic pacing mode. BNP levels were the lowest in AAI(R) pacing and the highest in VVI(R) pacing among the three pacing modes. The BNP level in DDD(R) pacing was between that for AAI(R) pacing and VVI(R) pacing. The results indicate that physiologic pacing should first be chosen in patients with bradycardia and congestive heart failure (CHF), and that AAI(R) was the best pacing mode if atrioventricular conduction function was normal.