Oxide Carbon Nanotubes Research Articles

In-situ hydrothermal synthesis of CNT decorated by nano ZnS/CuO for simultaneous removal of acid food dyes from binary water samples

The zinc sulfide/copper oxide–carbon nanotube nanocomposite (ZnS/CuO-CNT) was fabricated by using an in-situ hydrothermal synthesis method and was used for simultaneous ultrasound-assisted adsorptive removal of a binary mixture of ponceau 4R (P4R) and tartrazine (TA) acid food dyes from contaminated water. The as-synthesized ZnS/CuO-CNT was described by FESEM, XRD, FTIR, BET, and zeta potential analysis. The results included nested network morphology, high purity with the crystalline structure, oxygen-containing functional groups, mesoporous/micropores texture with cumulate interspace, specific surface area of 106.54 m2 g-1, and zero-point charge (pHzpc) of 5.3. In adsorption experiments, the simultaneous effect of main independent variables, including solution pH, adsorbent dosage, concentration of each dye, temperature, and sonication time on the removal efficiency of dyes was studied systematically using the central composite design (CCD) method based on response surface methodology (RSM). Also, the second-order multivariate equation was presented to determine the relationship between the removal efficiencies of P4R and AT dyes and six independent effective variables. The high correlation coefficient (R2 ≥ 0.99), significant p-value (P < 0.0001), and non-significant lack-of-fit (P > 0.05) showed the high accuracy, and validity of the proposed model to predict the removal efficiency of P4R and TA acid food dyes. The experimental removal efficiency for P4R and TA dyes was found to be 98.45 ± 2.54, and 99.21 ± 2.23, respectively. Also, the Langmuir maximum adsorption capacity for P4R and TA dyes was determined to be 190.1 mg g-1 and 183.5 mg g-1, respectively. Finally, the adsorbent's reusability was tested for six periods and could be reused repeatedly without significant reduction in adsorption performance.

RuCo alloys anchoring on hierarchical oxidized CNT architectures with boosted catalytic activity for water splitting

Exploring cost-competitive electrocatalysts with enhanced catalytic activity is important for producing clean energy via water-splitting, including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, RuCo alloy nanoparticles uniformly anchoring on oxidized carbon nanotube architectures (RuCo-OCA) have been constructed via ozonation, freeze-drying and thermal activation methods. RuCo-OCA exhibits excellent catalytic HER and OER performance. To reach a current density of 10 mA cm−2, RuCo-OCA requires low overpotential of 42 and 258 mV for HER and OER with the Tafel slope of 32.8 and 65.9 mV dec−1 in 1 M KOH, respectively. Meanwhile, RuCo-OCA shows negligible change of current density after chronoamperometry test for 10 h with low charge transfer resistance of 15.9 and 96 Ω for HER and OER. Furthermore, the symmetric RuCu-OCA||RuCu-OCA electrolyzer shows superior water-spitting performance to Pt/C/||RuO2 electrolyzer with a potential of 1.56 V at 10 mA cm−2. The excellent electrocatalytic performance of RuCo-OCA can be attributed to the hierarchical structure of oxidized CNT aerogel for the improved reaction kinetics and the formation of RuCo alloys with the modified electronic structure and adsorbability of intermediates. Meanwhile, the boosted active sites have been probed by density function theory. The coupling of RuCo alloys with conductive oxidized CNT aerogel can provide a new strategy to further expedite the electrocatalytic efficiency and activity of catalysts for water splitting.

Copper Zinc Sulfide (CuZnS) Quantum Dot-Decorated (NiCo)-S/Conductive Carbon Matrix as the Cathode for Li-S Batteries.

Sulfur composites consisting of electrochemical reactive catalysts/conductive materials are investigated for use in lithium–sulfur (Li–S) batteries (LSBs). In this paper, we report the synthesis, physicochemical and electrochemical properties of CuZnS quantum dots (CZSQDs) decorated with nickel–cobalt–sulfide ((NiCo)–S)) mixed with reduced graphene oxide (rGO)/oxidized carbon nanotube (oxdCNT) (rGO/oxdCNT) ((NiCo)–S@rGO/oxdCNT) composites. These composites are for the purpose of being the sulfur host cathode in Li–S batteries. The as-prepared composites showed a porous structure with the CZSQDs being uniformly found on the surface of the rGO/oxdCNT, which had a specific surface area of 26.54 m2/g. Electrochemical studies indicated that the (NiCo)–S@rGO/oxdCNT cells forming the cathode exhibited a maximum capacity of 1154.96 mAhg−1 with the initial discharge at 0.1 C. The smaller size of the CZSQDs (~10 nm) had a positive effect on the CZSQDs@(NiCo)–S@rGO/oxdCNT composites in that they had a higher initial discharge capacity of 1344.18 mAhg−1 at 0.1 C with the Coulombic efficiency being maintained at almost 97.62% during cycling. This latter property is approximately 1.16 times more compared to the absence of the Cu–Zn–S QD loading. This study shows that the CuZnS quantum dots decorated with a (NiCo)–S@rGO/oxdCNT supporting matrix-based sulfur cathode have the potential to improve the performance of future lithium–sulfur batteries.

Preparation and reinforcement performance of RGO-CNTs-SiO2 three-phase filler for rubber composites

Rubber reinforcement technology is developing towards the direction of high efficiency and multi-functionality, and the reinforcement of rubber by a single-component filler can no longer meet the requirements. Nanocomposite fillers have become the development trend of high-performance reinforcing fillers due to the complementary advantages and synergistic reinforcing effects of each component. Reduced graphene oxide-carbon nanotubes (RGO-CNTs) composites were prepared by a method of electrostatic assembly. The non-covalent modified RGO-CNTs was used as a substance to grow in situ SiO2 nanoparticles (RGO-CNTs-SiO2), and the RGO-CNTs-SiO2 three-phase fillers were obtained. The RGO-CNTs-SiO2 three-phase fillers were further used to study the reinforcing properties of hydrogenated nitrile rubber (HNBR). Furthermore, the effects of RGO-CNTs-SiO2 with different component contents on the reinforcing properties of HNBR were systematically studied. The TEM images of RGO-CNTs-SiO2 show that the RGO and CNTs promotes mutual dispersion, and the SiO2 nanoparticles (average diameter 7 nm) are highly dispersed on the surface of RGO-CNTs. The characterization of RGO-CNTs-SiO2/HNBR indicates that the RGO-CNTs-SiO2 efficiently weaken the filler network and improve the filler-rubber interaction. The results show that the three-phase fillers produce obvious synergistic reinforcing effects. The highest tensile strength (30.1 MPa) of RGO-CNTs-SiO2/HNBR is achieved at the RGO:CNTs mass ratio of 1:5, the RGO-CNTs mass percentage of 2%, and the filler loading of 50 phr. This work demonstrates the considerable promise for developing three-phase filler-based rubber composites.

Galvanically Displaced Noble Metal Nanoparticles Onto Electrosprayed Graphene-CNT Electrodes for Lithium-Ion and Fuel Cell Applications

Advanced lithium-ion batteries (LIB) and Fuel Cells demonstrate promise as the next generation energy storage and conversion (ESC) technology especially as it pertains to wearable technology and electric vehicles. Although LIB dominate the battery market (>90%) due its reliability, long cycle life, and market maturity, different and more innovative ways to improve the chemistry of the electrode structure must be discovered in order to reduce the cost of materials, dendritic issues at the solid-electrolyte interphase (SEI) layer, and improve upon the limited anode capacity (graphite theoretical capacity 372 mAh g-1). Fuel cells are also promising renewable energy sources due to their high energy densities and scalability. However, both LIB and Fuel Cells are limited by the 3D materials that enable their enhanced electrochemical and catalytic performance. We propose a platform methodology for the synthesis of 3D electrodes with carbon nanomaterials and noble metals. The enhanced electrical, thermal, chemical, and mechanical stability of graphene and carbon nanotubes (CNTs) offer an ideal platform for electrode design for energy storage applications. Here we utilize spontaneous galvanic displacement driven by reduction potential difference to produce three-dimensional (3D) graphene-CNT-noble metal nanoparticle 3D electrode without the use of any harsh chemical reducing agents. A graphene-CNT slurry with a poly(acrylic acid) (PAA) binder is air-controlled electrosprayed onto copper foil to create 3D composite thin film electrodes. Although noble metals are expensive materials to be used in LIB, we propose a new approach for synthesizing conductive electrochemically stable electrodes. We demonstrate a spontaneous technique to reduce the noble metal salts by galvanically displacement with the copper substrate to deposit noble metal nanoparticles onto the graphene-CNT electrode. The noble metal salt solutions (HAuCl4, K2PtCl4, and Na2PdCl4) are drop casted onto the resulting copper supported graphene-CNT electrodes to enable electroless noble metal nanoparticle deposition. Scanning electron microscopy (SEM) imaging confirms that the carbon nanomaterials are integrated with noble metal nanoparticles forming an overall 3D electrode structure. Raman spectroscopy verifies the characteristic D-band, G-band, and 2D-band peaks from the graphitic structure within the 3D carbon and noble metal nanostructure. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) are used to characterize the electrochemical properties of the electrodes. We demonstrate that the use of an energy-free and spontaneous process based on the difference in thermodynamic reduction potentials as the driving force for producing carbon nanomaterial/noble metal nanostructured electrodes for batteries and fuel cells. This process is a more simple, scalable, and cost-efficient alternative to current methods for developing lightweight and catalytic electrodes for energy storage applications, such as lithium-ion batteries, lithium-air batteries, and fuel cells. Raman Spectroscopy is used to confirm the presence defects on the oxidized carbon nanotube and graphene oxide surface. Scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), and x-ray diffraction (XRD) were used to characterize the morphology of the 3D carbon-noble metal structure and the surface elemental composition. Electrochemical characterization techniques such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), performance testing for oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and potentiostatic measurements are used to characterize the areal specific resistance (ASR), areal capacitance, electrochemical surface area, initial Coulombic efficiency (ICE), rate capability and cycling performance, and electrochemical stability, respectively.

Dopant-Free Conductive SnO2/CNT Support for the Oxygen Evolution Reaction in Polymer Electrolyte Membrane Water Electrolysis

Polymer electrolyte membrane water electrolysis (PEMWE) is an energy conversion device for producing green hydrogen, which is one of the key elements for moving toward a hydrogen society. However, there are two obstacles to the commercialization of PEMWE, which are cost and durability. In particular, a large amount of a noble metal catalyst such as ruthenium (Ru) or iridium (Ir) is required for the oxygen evolution reaction (OER) occurring at the anode electrode. To reduce the usage of noble metal catalysts, carbon supports could be introduced. However, due to the harsh conditions resulting from the high voltage and acidic environment in the anode, the carbon easily corrodes and decomposes into carbon dioxide. To prevent corrosion of support materials, metal oxide support can be used. Tin oxide (SnO2) is one of good candidate support because it is stable under acidic and high potential conditions. However, the electrical conductivity of SnO2 needs to be increased to be used as an anode support material for PEMWE. In previous studies, the electrical conductivity of SnO2 was increased by the introduction of dopants such as antimony (Sb), indium (In), fluorine (F) and so on. However, recently, it was reported that these dopants can be dissolved under the OER conditions. Thus, a new approach for synthesizing dopant-free and stable metal oxide supports is required.Herein, we report tin oxide-carbon nanotube composite (SnO2-CNT) support for the anode in PEMWE. The SnO2 nanoparticles were coated on CNT for high conductivity and stability. For evaluating the electrochemical performance, Ir nanoparticles were supported on SnO2-CNT. Ir/SnO2-CNT showed high OER activity and stability under acidic conditions. These results demonstrated that SnO2-CNT support can be utilized for reducing the amount of precious metal catalysts and increasing the stability of OER supported catalyst in PEMWE.

Grafting Copper Atoms and Nanoparticles on Double-Walled Carbon Nanotubes: Application to Catalytic Synthesis of Propargylamine.

The decoration of carbon nanotubes (CNTs) by metal nanoparticles (NPs) combines the advantages of a high specific surface material with catalytic properties of metal nanocrystals. Little work has been devoted to the decoration of CNTs with copper NPs, and no evidence of copper atomic decoration of CNTs has shown up until now. Herein, we demonstrate that the strong acidic oxidation of double-walled CNTs (dwCNTs) is very efficient for the decoration of the carbon surface by copper NPs and atoms. This treatment severely degraded the CNT walls and generated a large amount of disordered sp3 carbon. This amorphous carbon film bears many chemically active functions like carboxyl and hydroxyl ones. In such conditions, the CNT walls behave as very efficient ligands for the stabilization of copper obtained by the thermolysis of the mesityl precursor in organic solution under mild dihydrogen pressure. In addition to copper NPs, we evidenced the presence of a regular coverage with copper atoms over the dwCNTs. This nanocomposite catalyzes the quantitative synthesis of propargylamines via one A3-type coupling reaction. Five consecutive catalytic cycles with 100% yield could be performed with no loss of activity, and the combination of Cu supported on dwCNTs allows a facile recycling of the catalytic material.

Carbon aerogels derived from waste paper for pipette-tip solid-phase extraction of triazole fungicides in tomato, apple and pear

In order to develop environmentally friendly, economical and facile preparation method of carbon aerogels (CAs), the waste printing paper as the raw material was combined with graphene oxide and carboxylic multi-walled carbon nanotubes to produce CAs (ρ = 44 mg cm−3). The CAs with different composition were investigated, the addition of graphene oxide led to the reduction of adsorption sites and the reduction of extraction performance. But the carbon nanotubes made CAs have a better pore structure. The CAs as adsorbent were loaded into a pipette-tip for solid-phase extraction of hexaconazole and diniconazole. Coupled with gas chromatography, an analytical method was established under the optimized conditions. The limits of detection were between 0.08 and 0.32 mg kg−1, the linear ranges were 0.96–200.0 mg kg−1 and 0.24–200.0 mg kg−1. The relative recoveries were in the range of 81.0–119%. The results indicated that the method had potential application for the determination of triazole fungicides.

A Sequenced Study of Improved Dielectric Properties of Carbon Nanotubes and Metal Oxide-Reinforced Polymer Composites.

Polymers have gained attraction at the industrial level owing to their elastic and lightweight nature, as well as their astonishing mechanical and electrical applications. Their scope is limited due to their organic nature, which eventually leads to the degradation of their properties. The aim of this work was to produce polymer composites with finely dispersed metal oxide nanofillers and carbon nanotubes (CNTs) for the investigation of their charge-storage applications. This work reports the preparation of different polymeric composites with varying concentrations of metal oxide (MO) nanofillers and single-walled carbon nanotubes (SWCNTs). The successful synthesis of nanofillers (i.e., NiO and CuO) was carried out via the sonication and precipitation methods, respectively. After, the smooth and uniform polymeric composite thin films were prepared via the solution-casting methodology. Spectroscopy and diffraction techniques were used for the preliminary characterization. Scanning electron microscopy was used to check the dispersion of carbon nanotubes (CNTs) and MOs in the polymer matrix. The addition of nanofillers and carbon nanotubes (CNTs) tuned the bandgap, reduced the strain, and enhanced the elastic limit of the polymer. The addition of CNT enhanced the mechanical strength of the composite; however, it increased the conductivity, which was tuned by using metal oxides. By increasing the concentration of NiO and CuO from 2% to 6% bandgap of PVA, which is 5–6 eV reduced to 4.41 and 4.34 eV, Young’s moduli of up to 59 and 57.7 MPa, respectively, were achieved. Moreover, improved dielectric properties were achieved, which shows that the addition of metal oxide enhances the dielectric behavior of the material.

Study on the Gamma Irradiation Characteristics of a Carbon Nanotube Sponge/Polydimethylsiloxane/Tungsten Oxide Flexible Force-Sensitive Structure

This paper proposes a new type of flexible force-sensitive structure that is resistant to gamma radiation and is made of tungsten oxide (WO3) powder, polydimethylsiloxane (PDMS), and carbon nanotube (CNT) sponge. The thickness of the sample was 2.2 mm, the middle interlayer was composed of a carbon nanotube (CNT) sponge and PDMS to form a conductive layer, and the upper and lower layers were made of tungsten oxide and PDMS, which formed a gamma-ray shielding layer. When the particle size of the tungsten oxide powder was 50 nm, 100 nm, and 1 µm, the composite force-sensitive structure exhibited better force-sensitive performance. The composite force-sensitive structure was irradiated with doses of 5, 20, 50, and 100 KGy through 60Co- rays with an energy of 1.25 MeV. The results showed that the force-sensitive characteristics changed little in significance after irradiation by different doses of gamma rays, indicating that the force-sensitive structure has good resistance to gamma radiation. This flexible stress sensor can be used in soft robots and health inspection, even in harsh environments without significant performance loss.

Biomimetic Janus photothermal membrane for efficient interfacial solar evaporation and simultaneous water decontamination

Solar-driven water evaporation has been regarded as a promising technology to generate clean water due to the abundance and environmental friendliness of solar energy resources. However, the limited clean water production and limitation in tailored solar-driven system (SDS) have impeded its practical application. Herein, inspired by Lemna minor, a biomimetic, hierarchically structured, photothermal membrane (b-HPM) comprising Ti3C2Tx MXene and oxidized carbon nanotubes cross-linkage is designed. The hydrophilic bottom layer of b-HPM with macropores helps promote water transportation whilst the hydrophobic mesoporous upper layer accelerates solar/contaminant absorption and inhibits heat loss. Such-acquired Janus membrane not only improves the water transfer rate to reach 1.66 kg m−2h−1 but also harvests excellent evaporation efficiency of 99.73% deriving from the direct solar light energy (92.58%) and ambient environment (7.15%) under one-sun illumination. Impressively, PPCP removal of > 99% in raw wastewater, and no pollutants were found in the distilled water. More encouragingly, b-HPM enables a high evaporation rate and contaminant removal efficiency in real waterbody with long-term utilization based upon experimental and theoretical calculation results. Our designed SDS synergizes the merits of facile preparation, high light utilization efficiency, high-rate clean water generation, stability and robust performance, holding great promise in solving freshwater shortage and remedying water pollution under natural sunlight.

Highly Aligned Ni-Decorated GO-CNT Nanostructures in Epoxy with Enhanced Thermal and Electrical Properties.

In this study, graphene oxide–carbon nanotubes nanostructures decorated with nickel nanoparticles (NiGNT) were prepared through the molecular-level-mixing method, followed by a reduction process, and then applied as reinforcements to enhance the epoxy resin matrix. The ferromagnetism of the Ni nanoparticles allowed NiGNT nanostructures to be vertically aligned within the composite with the assistance of a magnetic field. Due to the alignment distribution of the NiGNT, the composites demonstrated enhanced anisotropic thermal and electrical conduction performances, compared with pure epoxy and randomly distributed composites. The aligned distribution of NiGNT–epoxy composites displayed 2.7 times higher thermal conductivity and around 104 times better electrical conduction performance, compared with pure epoxy. The thermal expansion of NiGNT–epoxy composite was also restricted in the aligned direction of NiGNT nanostructures. Thus, NiGNT–epoxy composites show great potential as future aerospace, aviation, and automobile materials.

Effect of Surface Modification of Carbon Nanotubes on the Properties of High-Strength and High-Conductivity Copper Matrix Composites

The use of carbon nanotubes (CNTs) as the reinforcing phase to prepare copper-based composite materials can improve the strength and high conductivity of copper-based conductors. In order to analyze the effect of surface oxidation modification on the structural properties of carbon nanotubes and its strengthening effect on composite materials, this article combines heterogeneous copolymerization liquid phase mixing method and spark plasma sintering molding method; prepares the carbon nanotubes/copper composite materials using carbon nanotubes under different oxidation treatment conditions as the reinforcing phase (the volume fraction of carbon nanotubes is 3%); and characterizes the microstructure, mechanical properties, and electrical and thermal conductivity of the composite material. Studies have shown that the tensile strength and hardness of composite materials first increase with the increase of CNT oxidation treatment time and then decrease with the increase of oxidation treatment time. When the oxidation treatment time is 4 h, CNTs are uniformly dispersed in the matrix while maintaining good structural integrity and load-bearing capacity, and the composite material has the highest mechanical properties. The tensile strength of the composite material made of 80‐ nm CNTs reaches 452.4 MPa, which is 1.6 times that of pure copper, and the hardness reaches 127.4HV, which is twice that of pure copper. The electrical conductivity and thermal conductivity of the composite material first increase with the increase of the oxidation treatment time of carbon nanotubes and then decrease with the increase of the oxidation treatment time. The 80 nm CNT reinforced composite material has better CNT dispersion performance and higher conductivity than that of 15 nm CNT preparation. The electrical conductivity of the composite material reaches the maximum value of 92% IACS when the CNT oxidation treatment time is 4 hours, which is 95% of the pure copper sample, and the electrical conductivity is significantly better than that of the CNT/Cu composite material and copper alloy prepared by other methods. The thermal conductivity of composite materials is lower than that of pure copper. The thermal conductivity of carbon nanotubes with an oxidation treatment time of 2 h decreases most obviously, indicating that the thermal resistance generated by the interface and agglomeration phases in the composite material affects its thermal conductivity.

3D-functionalized carbon nanotube microsphere networks modified by 1-aminopyrene promote silicon anode with an enhanced cyclic performance for Li-ion batteries

Although silicon has higher theoretical specific capacity to meet the demand for higher energy density, its large volume expansion and low conductivity make the practical application of silicon anode difficult in the field of lithium-ion batteries. In this work, Si@(AP-AOCNTs) composites with uniform conductive network and pore structure are prepared by spray drying method. In the composite microspheres, silicon particles are embedded into the 3D interwoven network of 1-aminopyrene modified oxidized carbon nanotubes, which can not only buffer the volume expansion of silicon, but also ensure the effective transport of electrons and ions. This is demonstrated by the remarkable cycle life, and the electrode still has a reversible specific capacity of 939.3mAh/g after 975 cycles at 0.5A/g. Moreover, 97.3% of the initial capacity (at 0.5A/g) is still retained after the rate cycling, when the current density returns to 0.5A/g.

Enhanced Removal of Diesel Oil Using New Magnetic Bentonite-Based Adsorbents Combined with Different Carbon Sources

In this work, new magnetic bentonite-based adsorbents combined with different carbon sources, namely, reduced graphene oxide and multiwall carbon nanotubes, were synthesized via co-precipitation method. The synthesized adsorbents were characterized using XRD, TGA, SEM, EDX, TEM, and BET analysis techniques. The adsorbents were then used to remove oil from aqueous solutions of water-in-oil emulsion by performing batch adsorption experiments. The experimental data were fitted to three isotherm models including Langmuir, Freundlich, and Sips models using non-linear regression and were compared using Akaike Information Criterion statistical model. The data analysis showed that Sips model best fits the experimental data for the adsorption of oil onto both adsorbents. The maximum adsorption capacity of oil from sips model were 81.65 mg/g and 77.12 mg/g for Fe3O4/Bent/rGO and Fe3O4//Bent/MWCNTs, respectively. The obtained kinetics data were fitted to pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Pseudo-second order kinetic model best fitted the kinetic data of both adsorbents. Overall, both adsorbents showed high removal efficiency reaching equilibrium in less than 50 min indicating that both adsorbents can be successfully utilized in industrial adsorption process.Graphical abstract

Eco-friendly surface modification of oxidized carbon nanotubes with curcumin for simultaneous electrochemical detection of dopamine and serotonin

Here we report a surface modification of oxidized carbon nanotubes (oCNTs) pre-modified on a glassy carbon electrode (GCE) with electrodeposited curcumin (CM) as a metal-free platform for simultaneous detection of dopamine (DA) and serotonin (SE). CM dissolved in an alkaline medium, was electrodeposited on various carbon-based materials and its activity towards detection of DA and SE was verified. Excellent synergy was observed between CM and oCNT towards simultaneous detection of DA and SE in pH 7 phosphate buffer saline (PBS) at 0.2 V and 0.34 V, respectively. DFT calculations also showed higher stabilization energy of the oxidized CM i.e., curcumin semiquinone (CMQ) with oCNT (3.35 eV) compared to bare CNT (2.87 eV). The CM-oCNT on a glassy carbon electrode (GCE) exhibited 4.42 times higher surface area and 60 times enhanced anodic current compared to bare GCE towards highly selective oxidative response of DA and SE with a potential difference of 158 mV. Linear calibration curves were obtained for DA and SE ranging from 10 to 170 μM and 10 to 130 μM, respectively. The research outcomes point towards possible metal-free combinations of organic moieties and carbon materials for detection of vital biomolecules in the future.

Microwave-assisted hydrothermal synthesis of three-dimensional NbOPO4-reduced graphene oxide-carbon nanotube composite for high performance sodium-ion battery anode

Sodium-ion batteries (SIBs) have aroused more and more academic and industrial interest due to their decent electrochemical performance and the cost-effectiveness of sodium (Na) resource. However, fabricating an appropriate anode material with high specific capacity, long-term cycle stability and superior rate capability remains a great challenge. Here, we adopt an efficient microwave-assisted hydrothermal method to prepare layered niobium oxyphosphate (NbOPO4) nanosheets, which grows on the single-walled carbon nanotubes (SWCNT) and reduced graphene oxide (rGO) (NbOPO4-rGO-SWCNT). Benefiting from three-dimensional hierarchical architecture combining NbOPO4 nanosheets with rGO-SWCNT framework with excellent electrical conductivity, NbOPO4-rGO-SWCNT electrode delivers a higher reversible specific capacity (323.2 mAh g−1 at 0.1 A g−1) and superior rate capability (147.9 mAh g−1 at 5 A g−1) than that of NbOPO4 (143.1/43.5 mAh g−1). Ex-situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements further reveal the electrochemical mechanism that reversible reaction between niobium phosphate (NbPO4) and niobium (Nb) occurs after the initial intercalation-conversion reaction, which contributes to the stable reversibility and high-rate capability in the following cycling. This work not only indicates that NbOPO4-rGO-SWCNT can act as a desirable anode material for SIBs, but also provide new insights to material design for niobium oxyphosphate composite.

Aromatic Dipeptide Homologue-Based Hydrogels for Photocontrolled Drug Release.

Peptide-based hydrogels are considered of special importance due to their biocompatibility and biodegradability. They have a wide range of applications in the biomedical field, such as drug delivery, tissue engineering, wound healing, cell culture media, and biosensing. Nevertheless, peptide-based hydrogels composed of natural α-amino acids are limited for in vivo applications because of the possible degradation by proteolytic enzymes. To circumvent this issue, the incorporation of extra methylene groups within the peptide sequence and the protection of the terminal amino group can increase the enzymatic stability. In this context, we investigated the self-assembly capacity of aromatic dipeptides (Boc-α-diphenylalanine and Boc-α-dityrosine) and their β- and γ-homologues and developed stable hydrogels. Surprisingly, only the Boc-diphenylalanine analogues were able to self-assemble and form hydrogels. A model drug, l-ascorbic acid, and oxidized carbon nanotubes (CNTs) or graphene oxide were then incorporated into the hydrogels. Under near-infrared light irradiation, the photothermal effect of the carbon nanomaterials induced the destabilization of the gel structure, which caused the release of a high amount of drug, thus providing opportunities for photocontrolled on-demand drug release.

Promising Electrocatalytic Water and Methanol Oxidation Reaction Activity by Nickel Doped Hematite/Surface Oxidized Carbon Nanotubes Composite Structures.

Tailoring the precise construction of non-precious metals and carbon-based heterogeneous catalysts for electrochemical oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) is crucial for energy conversion applications. Herein, this work reports the composite of Ni doped Fe2 O3 (Ni-Fe2 O3 ) with mildly oxidized multi-walled CNT (O-CNT) as an outstanding Mott-Schottky catalyst for OER and MOR. O-CNT acts as a co-catalyst which effectively regulates the charge transfer in Ni-Fe2 O3 and thus enhances the electrocatalytic performance. Ni-Fe2 O3 /O-CNT exhibits a low onset potential of 260 mV and overpotential 310 mV @ 10 mA cm-2 for oxygen evolution. Being a Mott-Schottky catalyst, it achieves the higher flat band potential of -1.15 V with the carrier density of 0.173×1024 cm-3 . Further, in presence of 1 M CH3 OH, it delivers the MOR current density of 10 mA cm-2 at 1.46 V vs. RHE. The excellent electrocatalytic OER and MOR activity of Ni-Fe2 O3 /O-CNT could be attributed to the synergistic interaction between Ni-doped Fe2 O3 and O-CNT.

An electrochemical sensor based on reduced graphene oxide/β-cyclodextrin/multiwall carbon nanotubes/ polyoxometalate tetracomponent hybrid: Simultaneous determination of ascorbic acid, dopamine and uric acid

In this work, a novel tetracomponent hybrid electrochemical sensor was constructed with reduced graphene oxide/β-cyclodextrin/multiwall carbon nanotubes/ polyoxometalate (RGO-CD-MWCNT-POM), which achieved simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA). First, the RGO-CD-MWCNT-POM was synthesized by assembly of graphene oxide (GO), β-cyclodextrin (CD), and multiwall carbon nanotube (MWCNT), with subsequent reduction of GO in the assistance of polyoxometalate (POM). Afterward, the morphology and structural properties were characterized by transmission electron microscope (TEM), energy dispersive X-ray mapping (EDS), scanning electron microscope (SEM), Raman spectroscopy, and thermogravimetric analysis (TGA). After its modification on glassy carbon electrode (GCE), RGO-CD-MWCNT-POM could simultaneously detect AA, DA, and UA by voltammetry method. Its enhanced electrochemical sensing performances derive from the combined merits of each component: supramolecular recognition from CD, excellent electronic properties from carbon components, and electrocatalyst from POM. Under optimal conditions, the linear ranges of AA, DA and UA were 5–2000, 0.5–300 and 1–400 μM with the detection limits with 0.84 μM, 0.04 μM, 0.05 μM, respectively. The proposed sensor was also well applied in practical simultaneous measurement in urine sample with the recovery ranges of 94%∼108%. Our work suggests the fabricated sensor is promising for constructing excellent sensing platform.