Multiwalled Carbon Nanotube Films Research Articles

Tailoring terahertz surface plasmon wave through free-standing multi-walled carbon nanotubes metasurface

Surface plasmons have a fundamental role in the dynamics of photon-electron interactions and in optical metamaterials. Terahertz (THz) time-domain spectroscopy was used to characterize the complex dielectric constant, index of refraction, and conductivity of super-aligned, free-standing, multi-walled carbon nanotube films over the range 0.2-2.5 THz. These complex parameters were in excellent agreement with Maxwell-Garnett and Drude-Lorentz models. In addition, surface plasmon excitations in engineered, subwavelength, multi-walled carbon nanotube metasurfaces were examined. The observed surface plasmon resonances, reproduced by simulation, could be changed over the THz frequency range by altering the lattice constant of the arrays. The THz transmission was enhanced at the resonance peak. Overall, the results indicate potential applications for THz metasurfaces based on super-aligned, free-standing multi-walled carbon nanotubes.

Investigation of the electrochemical behavior of tizanidine on the surface of glassy carbon electrode modified with multi-walled carbon nanotube/titan yellow–doped polypyrrole

The present paper describes a voltammetric sensor based on glassy carbon electrode (GCE) modified with a thin film of multi-walled carbon nanotubes (MWCNTs) coated with an electro-polymerized layer of titan yellow-doped over–oxidized polypyrrole (OPPY) for the determination of tizanidine (TIZ). A significant enhancement was observed in the anodic peak current of TIZ on the surface of OPPY/CNT/GCE, relative to the bare, CNT- and OPPY-coated GCEs. The microscopic structure and surface morphology of the composite film was thoroughly characterized by means of atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV) techniques. The effect of various experimental parameters, such as pH of the supporting electrolyte, drop size of the casted MWCNTs suspension, number of electro-polymerization cycles and accumulation time were investigated by monitoring the LSV responses of TIZ. In the optimal conditions, the modified electrode showed two linear dynamic ranges of 0.01–1.0 μM and 1.0–10 μM with a detection limit of 3 nM for the voltammetric determination of TIZ. Besides high sensitivity, the fabricated sensor represented high stability and good reproducibility for TIZ analysis. These properties made the prepared sensor suitable for the accurate determination of trace amounts of TIZ in pharmaceutical and clinical preparations.

High-Performance Pressure Sensor for Monitoring Mechanical Vibration and Air Pressure.

To realize the practical applications of flexible pressure sensors, the high performance (sensitivity and response time) as well as more functionalities are highly desired. In this work, we fabricated a piezoresistive pressure sensor based on the micro-structured composites films of multi-walled carbon nanotubes (MWCNTs) and poly (dimethylsiloxane) (PDMS). In addition, we establish efficient strategies to improve key performance of our pressure sensor. Its sensitivity is improved up to 474.13 kPa−1 by minimizing pressure independent resistance of sensor, and response time is shorten as small as 2 μs by enhancing the elastic modulus of polymer elastomer. Benefiting from the high performance, the functionalities of sensors are successfully extended to the accurate detection of high frequency mechanical vibration (~300 Hz) and large range of air pressure (6–101 kPa), both of which are not achieved before.

Stretchable array of high-performance micro-supercapacitors charged with solar cells for wireless powering of an integrated strain sensor

The aim of this paper is to report on the fabrication of a stretchable array of high-performance solid-state micro-supercapacitors (MSCs), which can be charged with integrated, commercial Si-based solar cells (SCs). This would facilitate the powering of an integrated strain sensor. The planar MSCs comprised electrodes of potentiostatically deposited polypyrrole, on spray-coated multi-walled carbon nanotube film, and a gel-type electrolyte of LiCl/polyvinyl alcohol with a redox additive of 1-methyl-3-propylimidazolium iodide. The fabricated MSC achieved an areal capacitance of 5.17 mF cm−2. After 5000 charge/discharge cycles, the MSC retained 80% of their initial capacitance. A strain sensor was fabricated utilizing a composite film of fragmentized graphene foam and polydimethylsiloxane. Such fabricated twelve parallel connected MSCs, a strain sensor, and SCs were integrated on a single deformable polymer substrate with embedded stiff platforms of negative epoxy series resist (SU-8) via long serpentine interconnections of polyimide encapsulated Ti/Pt metal film for mechanical stability under stretching. After 1000 repetitive biaxial stretching/releasing cycles by 30%, no noticeable change was observed in the charge/discharge behavior of the MSC array. Furthermore, both the photo-charge/discharge characteristics and electrochemical performance remained stable. When the whole integrated system was attached to the wrist, the integrated strain sensor could detect both externally applied strain and the arterial pulse using the energy stored in the MSCs from the SCs.

Stretchable Array of Wirelessly Charged High Performance Micro-Supercapacitors with Solar Cells for Wireless Powering of the Integrated Strain Sensor

Along with the increasing demands for wearable health care and biomedical applications, there has been extensive research on the development of various stretchable electronic devices with mechanical stability even under deformations caused by body or skin movements. Also, energy storage devices which can be integrated with the stretchable active sensor devices have been actively studied for the practical utilization of wearable electronics without any wire-connected external power sources. Among various candidates for integrated energy storage devices, high performance solid-state micro-supercapcitors (MSCs) have been extensively investigated. Furthermore, integration of those MSCs with photovoltaic devices is expected to provide the power for the sensors, leading to the wirelessly driven skin-attachable health monitoring sensor system. In this work, we report on the fabrication of stretchable array of high performance solid-state MSCs which can be charged via integration with Si-based commercial solar cell so that those can power the integrated strain sensor. The planar MSC consists of electrodes of potentiostatically deposited polypyrrole on spray coated multi-walled carbon nanotubes film and gel-type electrolyte of LiCl/polyvinyl alcohol with redox additive of 1-Methyl-3-propylimidazolium iodide. The fabricated MSC shows areal capacitance 5.2 mF cm-2 at a current density of 100 µA cm-2. The MSC retains 80% of initial capacitance after 5000 charge/discharge cycles at a current density of 100 µA cm-2. A strain sensor was fabricated with a composite film of fragmentized graphene foam and PDMS. Such fabricated MSCs, strain sensor, and the solar cell were integrated on a single deformable polymer substrate with embedded stiff platforms of SU-8 via long serpentine interconnections of Ti/Pt metal film for mechanical stability under stretching. After 1000 repetitive biaxial stretching/releasing cycles by 30%, there appeared no noticeable change in the charge/discharge behaviors. Furthermore, the photo-charge/discharge characteristics and electrochemical performance remained stable under biaxial stretching of 30 %. With the energy stored in MSCs using the solar cell, the integrated strain sensor could detect the externally applied strain and the arterial pulse after attachment of the whole integrated system onto the wrist of the author. This work successfully demonstrates the potential application of our stretchable self-charging power/sensor system to skin-attachable health monitoring devices.

π‐Plasmon absorbance films of carboxylic functionalized CNTs coupled with renewable PGP platforms

π‐Plasmon absorbance films of carboxylic functionalized multiwall carbon nanotubes (CNTs) coupled with renewable and recycled polycaprolactone grafted pectin (PGP) platforms as successful alternative for ordinary nondegradable platforms were investigated. Characterization of the synthesized carboxylic functionalized CNTs was performed using 1H NMR and attenuated total reflectance Fourier transform infrared for structural identification, thermogravimetric analysis and derivative thermogravimetric analysis for thermal stability, and X‐ray powder diffraction for crystal structure, whereas the characterization of prepared PGP was done by means of attenuated total reflectance Fourier transform infrared for chemical structure, differential scanning calorimetry for melting endotherms of polycaprolactone and high crystalline structure of PGP, and thermogravimetric analysis and derivative thermogravimetric analysis for thermal stability of PGP. Fabrication of water‐dispersed carboxylic functionalized CNTs coupled with PGP films was performed by casting technique in the presence of Ca2+ as cross‐linker. The thin films were tested for π‐plasmon absorbance using UV‐Vis spectrometry. Different fractions of carboxylic functionalized CNTs and PGP films demonstrated π‐plasmon absorbance broad peaks at λmax = 232 nm, which corresponded to 5.36 eV. The fabrication of novel films from renewable recycled PGP platform and advanced carboxylic functionalized CNTs properties will be the key features for many of next forthcoming technologies. The PGP considered as environment‐friendly and easily degradable platforms will be a successful alternative for conventional nondegradable electronic platforms, and water‐dispersed carboxylic functionalized CNTs with advanced properties will be finding accelerating executive applications.

SEMICONDUCTOR GAS SENSORS FOR DETECTION OF CHEMICAL WARFARE AGENTS AND TOXIC INDUSTRIAL CHEMICALS

The sensors for detection of toxic and chemical warfare agents (CWA) should be sensitive to low concentrations of gases – considerably lower than ones immediately dangerous to life or health concentrations. The paper shortly discusses classical CWAs and toxic industrial sensors; makes a comparison between nuclear weapons and chemical agents and a toxicity comparison between real gases and simulants. Moreover, the paper analyzes the simulants for testing the sensor devices and semiconductor gas sensor' technique; shows sensitivity change with dimethyl methylphosphonate (DMMP) gas concentration for sensor made of SnO 2 . The MoO 3 , NiO, Al 2 O 3 , In 2 O 3 , Pt, ZnO and ZrO 2 additives are reported to exhibit enhanced sensitivity to dimethyl methylphosphonate (DMMP), and Al2O3, In2O3, ZrO 2 and ZnO additives – to exhibit enhanced sensitivity to dipropyleneglycol methylethylene (DPGME). SnO2 devices with ZrO 2 and ZnO additives exhibit high sensitivity to acetonitrile. The sensors made from Co-doped SnO 2 films demonstrate sensitivity to CWAs such as sarin and yperite. We performed the measurements at the operating temperature of 210 ºC, and found that the sensor exposed comparatively greater concentration of target gas (200 ppm sarin and 100 ppm yperite) and the SnO 2 <Co> sensor was sensitive to yperite starting from 25 ppm. Furthermore, the sensitivities to 50 ppm and 12.5 ppm sarin were found. The paper presents the results of our studies on tin oxide/ multiwall carbon nanotube film nanocomposite sensors of PG, dimethylformamide (DMF) and formaldehyde (FA) using hydrothermal synthesis and sol-gel methods. The investigations of response/recovery characteristics in the 50–300 o C operating temperature range reveal that the optimal operating temperature for the PG, DMF and FA vapor sensors, taking into account both high response and acceptable response and recovery times, was 200–220 ºC. A sensor response dependence on gas concentration in all cases was linear. We measured the minimal PG, DMF and FA gas concentrations at which the perceptible signal was registered.

Terahertz Dispersion Characteristics of Super-aligned Multi-walled Carbon Nanotubes and Enhanced Transmission through Subwavelength Apertures

The terahertz (THz) dielectric properties of super-aligned multi-walled carbon nanotube (MWCNT) films were characterized in the frequency range from 0.1 to 2.5 THz with terahertz time-domain spectroscopy. The refractive index, effective permittivity, and conductivity were retrieved from the measured transmission spectra with THz incident wave polarized parallel and perpendicular to the orientation of carbon nanotubes (CNTs), and a high degree of polarization dependence was observed. The Drude-Lorentz model combined with Maxwell-Garnett effective medium theory was employed to explain the experimental results, revealing an obvious metallic behavior of the MWCNT films. Moreover, rectangular aperture arrays were patterned on the super-aligned MWCNT films with laser-machining techniques, and the transmission measurement demonstrated an extraordinarily enhanced transmission characteristic of the samples with incident wave polarized parallel to the orientation of the CNTs. Surface plasmon polaritons were employed to explain the extraordinarily enhanced transmission with high accuracy, and multi-order Fano profile was applied to model the transmission spectra. A high degree of agreement was exhibited among the experimental, numerical, and theoretical results.

Synthesis and field electron emission properties of multi-walled carbon nanotube films directly grown on catalytic stainless steel substrate

The multi-walled CNT films were directly grown on stainless steel substrates using an oxidation-reduction treatment with chemical vapor deposition. Microstructure and field emission properties of the as-received CNT films were detailedly investigated. The results indicate that the CNTs have originally random orientation with relative high density, good crystalline perfection and large diameter. Besides, the CNT films exhibit superior field electron emission performances with low threshold electric field (∼4.2 V/μm) and very high emission current density (∼24 mA/cm2). Importantly, the CNTs directly grown on stainless steel substrates have remarkable long-term stability with ∼3.4% fluctuation over 50 h continuous measurement under high current density, ∼10 mA/cm2. The perfect graphitization, large field enhancement factor, low contact resistance, good adhesion and high thermal conductivity are believed to be principally responsible for their superior field emission properties, which make them very promising application as an electron source in microthrust space electric propulsion neutralizer.

Current–voltage hysteresis and dielectric properties of PVA coated MWCNT film

In this work, we have prepared polyvinyl alcohol (PVA) coated multiwall carbon nanotube (MWCNT) film by an in situ chemical oxidative preparation technique. The thermogravimetric analysis clearly explains the thermal degradation of pure polymer and polymer nanocomposite film. We have studied the AC electrical transport properties and current–voltage (I–V) characteristic of PVA–MWCNT composites within the temperature range 300 ≤ T ≤ 423 K and frequency range 150 Hz ≤ f ≤ 2 MHz. It is observed that the dielectric constant of the composite film increases significantly. The frequency variation of AC conductivity follows the power law ( $$ \omega^{S} $$ ) and a sharp transition from small polaron tunneling to correlated barrier hopping model is found. The imaginary part of electric modulus shows non-Debye type asymmetric behaviour. The impedance spectroscopy shows the negative temperature coefficient of resistance of the composite film. Nyquist plot of the composite film at different temperatures is established from impedance measurement. The current–voltage characteristic (under ± 20 V) shows hysteresis behaviour and field dependent resistance. We simulate the experimentally observed current density–electric field data with the established theory.

Glass fiber/epoxy composites with integrated layer of carbon nanotubes for deformation detection

An entangled multiwalled carbon nanotube film (Buckypaper) embedded in a polyurethane membrane was integrated into a glass fiber reinforced epoxy composite by means of a vacuum infusion to become a part of the composite and to give it a strain self-sensing functionality. In order to increase the strain sensing, pristine nanotubes were either oxidized by KMnO4 or Ag particles were attached to their surfaces. Moreover, the design of the carbon nanotube/polyurethane sensor allowed a formation of a film of micro-sized cracks, which increased its reversible electrical resistance and resulted in an enhancement of the strain sensing. Prestaining of the sensor with Ag-decorated nanotubes increased its sensitivity to strain, which was quantified by a gauge factor, more than hundredfold in comparison with the sensor with pristine nanotubes. The tests revealed that the integrated strain sensing exhibited a long-term electromechanical stability, which was linked to the level of strain in the host glass fiber/epoxy composite.

Detection of neurochemicals with enhanced sensitivity and selectivity via hybrid multiwall carbon nanotube-ultrananocrystalline diamond microelectrodes.

Abnormal neurochemical signaling is often the underlying cause of brain disorders. Electrochemical microsensors are widely used to monitor neurochemicals with high spatial-temporal resolution. However, they rely on carbon fiber microelectrodes that often limit their sensing performance. In this study, we demonstrate the potential of a hybrid multiwall carbon nanotube (MWCNT) film modified boron-doped ultrananocrystalline diamond (UNCD) microelectrode (250 μm diameter) microsensor for improved detection of dopamine (DA) in the presence of common interferents. A series of modified microelectrodes with varying film thicknesses were microfabricated by electrophoretic deposition (EPD) and characterized by scanning electron microscopy, x-ray photoelectron spectroscopy, electrochemical impedance spectroscopy (EIS) and silver deposition imaging. Using cyclic voltammetry, the 100-nm "thin" film microelectrode produced the most favorable combination of DA sensitivity value of 36 ±2% μA/μM/cm2 with a linear range of 33 nM to 1 μM and a limit of detection (LOD) of 9.5 ± 1.2% nM. The EIS spectra of these microelectrodes revealed three regions with inhomogeneous pore geometry and differing impedance values and electrochemical activity, which was found to be film thickness dependent. Using differential pulse voltammetry, the modified microelectrode showed excellent selectivity by exhibiting three distinct peaks for the DA, serotonin and excess ascorbic acid in a ternary mixture. These results provide two key benefits: first, remarkable improvements in DA sensitivity (>125-fold), selectivity (>2000-fold) and LOD (>180-fold), second, these MWCNTs can be selectively coated with a simple, scalable and low cost EPD process for highly multiplexed microsensor technologies. These advances offer considerable promise for further progress in chemical neurosciences.

Decoration of Ultrathin MoS2 Nanoflakes over MWCNTs: Enhanced Supercapacitive Performance through Electrode to Symmetric All‐Solid‐State Device

AbstractUltrathin nanoflakes surface architecture of MoS2 thin film has been successfully decorated by simple and inexpensive chemical bath deposition onto dip and dry coated multiwalled carbon nanotubes (MWCNTs) to compare electrochemical performance with respect to individual MWCNTs and MoS2 thin films on flexible stainless steel (SS) substrates. Two dimensional thin films of MWCNTs, MoS2 and MoS2/MWCNTs (MCT) have been characterized through X‐ray diffraction, X‐ray photospectroscopy, Raman spectroscopy and scanning/transmission electron microscopes. The unique nanostructured morphology of well anchored nanoflakes over MWCNTs enhances the value of specific capacitance and improves the cycle stability compare to bare MoS2. Strikingly, all‐solid‐state (ASS) symmetric SS/MCT//MCT/SS supercapacitor device has been constructed using flexible stainless steel substrate with the aid of PVA‐LiClO4 gel electrolyte and results are discussed herein.

Ultrasound-spray deposition of multi-walled carbon nanotubes on NiO nanoparticles-embedded perovskite layers for high-performance carbon-based perovskite solar cells

Carbon-based perovskite solar cells (C-PSCs) are prized for their simple device structure, high cost-efficiency and good stability. However, the absolute efficiency of C-PSCs is still low due to inappropriate C/perovskite interfaces. Herein, we report a simple ultrasound spray method to deposit pure multi-walled carbon nanotubes (MWCNT) films. When directly deposited on perovskite films, MWCNT could form a seamless contact at the perovskite/carbon interface, thus boosting the power-conversion efficiency (PCE) of C-PSCs to 14.07% as compared to drop cast MWCNT electrodes. In addition, when the perovskite surface was embedded with a sub-monolayer of nickel oxide nanoparticles (NiO NPs) prior to the MWCNT deposition, we achieved a champion efficiency as high as 15.80%, which is among the highest C-PSCs efficiencies reported to date. Detailed characterizations revealed that by planting NiO NPs into the surface region of CH3NH3PbI3 crystals, the hole extraction efficiency was effectively enhanced and interfacial recombination was reduced. With silicon dioxide (SiO2 NPs) as a control, the NiO NPs layer was found to favorably bend the energy levels at the interface for selective hole extraction, thereby enhancing the overall photovoltaic performance. The combination of ultrasound spray and nanoparticle embedment technologies opens the way to cost-efficient and scalable production of C-PSCs.

Systematic optimization of MWCNT-PEDOT:PSS composite electrodes for organic transistors and dye-sensitized solar cells: Effects of MWCNT diameter and purity

Abstract Multi-walled carbon nanotubes (MWCNTs) and polymer composites have attracted significant attention as metal-free electrode materials for various electronic devices. Many studies have presented strategies to enhance the electrical conductivity of MWCNT/polymer composites. However, systematic studies on the effects of MWCNT features on the composite properties are still missing. Such studies can further the development of MWCNT/polymer-based conducting materials. Herein, we characterize composite films of MWCNTs and poly(3,4-ethylenedioxythiophene) polymerized with poly(4-styrenesulfonate) (PEDOT:PSS), with variations in the MWCNT diameter and purity. MWCNT features greatly affect the physical/chemical/electrical properties of the MWCNT/PEDOT:PSS composite films. In addition, the diameter and purity of MWCNTs also influenced the transition behavior of the composite films during the hydrochloric acid-methanol treatment, which was performed for increasing electrical conductivity. As a result, we could optimize the performance of organic transistors and dye-sensitized solar cells (DSSCs) using MWCNT/PEDOT:PSS composite films as source/drain electrodes and catalytic counter electrodes, respectively. Furthermore, using the optimized device parameters, we successfully fabricated high performance fluorine doped tin oxide-free DSSCs and high-gain organic complementary inverters using MWCNT/PEDOT:PSS composite electrodes.

Investigation into Electromechanical Properties of Biocompatible Chitosan-Based Ionic Actuator

Ionic actuators have attracted much attention due to their remarkably large strain under low-voltage stimulation. Here, we investigate a highly biocompatible ionic polymer actuator, which consists of multi-walled carbon nanotube (MCNT) film as a double electrode layer and an electrolyte layer equipped with chitosan polymer skeleton and ionic liquid. As a result, with the thickness increase of the electrolyte layer and the electrode layer, the membrane capacitance values are obviously improved, which are 0.01 F (membrane thickness of 1.3 mm) and 0.4 F (0.25 mm). The blocking force and its response speed show peak values of 5.75 mN (1.1 mm) and 5.1 mN (0.25 mm), while reverse increases for the displacement and its response speed are observed, which present maximum values of 10.3 mm (0.3 mm) and 13.3 mm (0.15 mm). Furthermore, for various thicknesses of the electrode layers under applied direct current of 5 V, the generated strain of 0.15 mm thickness (59%) is 4.92 times greater than that of the 0.25 mm thickness. This is against the strain difference on the electrode surface due to the growing stiffness of the electrode layer. Additionally, from the experiments of the electromechanical energy efficiency of various electrode layers and electrolyte layers, our actuator exhibits excellent electromechanical energy efficiency under a high electrical conductivity of the electrode layer, which enhance the specific electromechanical energy up to 9.95%.

Improved Performance of Glucose Bioanodes Using Composites of (7,6) Single-Walled Carbon Nanotubes and a Ferrocene-LPEI Redox Polymer.

The effect of incorporating different types of carbon nanotubes into composite films of a redox polymer (FcMe2-C3-LPEI) and glucose oxidase (GOX) was investigated. The composite films were constructed by first forming a high-surface area network film of either single-walled carbon nanotubes (SWNTs) or multiwalled carbon nanotubes (MWNTs) on a glassy carbon electrode (GCE) by solution casting of a suspension of Triton-X-100 dispersed SWNTs. Next a glucose responsive redox hydrogel was formed on top of the nanotube-modified electrode by cross-linking FcMe2-C3-LPEI with glucose oxidase via ethylene glycol diglycidyl ether (EGDGE). Electrochemical and enzymatic measurements showed that composite films made with (7,6) SWNTs produced a higher response (3.3 mA/cm2) to glucose than films made with (6,5) SWNTs (1.8 mA/cm2) or MWNTs (1.2 mA/cm2) or films made without SWNTs (0.7 mA/cm2). We also show that the response of the composite films could be systematically varied by fabricating SWNT films with different weight ratios of (7,6) and (6,5) SWNTs. Optimization of the (7,6) SWNTs loading and the redox polymer-enzyme film produced a glucose response of 11.2 mA/cm2. Combining the optimized glucose films with a platinum oxygen breathing cathode into a biofuel cell produced a maximum power density output of 343 μW/cm2.

Independently double-crosslinked carbon nanotubes/polyaniline composite films as flexible and robust free-standing electrodes for high-performance supercapacitors

Flexible free-standing materials make the electrode fabrication process simple in comparison with the conventional binder-enriched electrodes, especially for those with desirable mechanical strength. In the present work, the crosslinked multi-walled carbon nanotubes (C-CNTs) films with tensile strength of >1.75 MPa, were prepared by facile filtering the dispersion of the micrometer-scaled 3-D framework of crosslinked carbon nanotubes with common water pump, and used as high-strength conductive skeleton for polyaniline (PANI). The preparing conditions were optimized for the best electrochemical property of the flexible C-CNTs/PANI composite films. As free-standing electrodes for supercapacitors, the highest specific capacitance of 507 F/g or 314 F/g, energy density of 70.4 or 43.6 Wh/kg and power density of 0.44 or 0.43 kW/kg were achieved with the in-situ chemical oxidative polymerization or solution coating technique, respectively. Then the independently double-crosslinked carbon nanotubes/polyaniline (C-CNTs/TC-PANI) composite films were obtained by thermal crosslinking (TC) the PANI coatings in the C-CNTs/PANI films. Their specific capacitance, energy density, and power density increased to 531 F/g and 455 F/g, 73.8 and 63.2 Wh/kg, 0.49 and 0.47 kW/kg with the in-situ chemical oxidative polymerization or solution coating technique respectively, and their electrochemical cyclic stability was also enhanced distinctly.

Simple Potential Bioanalysis Micro reactor Fabricated By Vertically-Aligned Multi-Walled Carbon Nanotubes (MWCNTs)

A simple Microreactor was fabricated by vertically-aligned multi-walled carbon nanotubes (MWCNTs) on the mc-Si substrate. MWCNTs were synthesized by homemade equipment aided with chemical vapor deposition (CVD). The wettability of the surfaces of Microreactor with the synthesized MWCNTs, Au coating and plasma irradiation were investigated, respectively. Results show that the initial surface with the MWCNTs film behaves as a super-hydrophobic surface. However, it changes to a super-hydrophilic surface after coated with Au or irradiated by plasma. It shows that Microreactor with treated MWCNTs film can be used as potential applications for bioanalysis.

3D-hierarchical MoSe2 nanoarchitecture as a highly efficient electrocatalyst for hydrogen evolution

Clean hydrogen split from water by hydrogen evolution reaction (HER) is significant for sustainability, environmental emissions, and energy security. So far, it is still a big challenge to develop highly efficient noble metal-free electrocatalysts with comparable HER efficiency to platinum-based catalysts, which are mainly hindered by the intrinsic electrocatalytic property and particularly the reasonable nanostructure design of the electrocatalyst. Here we report a newly-designed three-dimensional hierarchical MoSe2 nanoarchitecture (3D-MoSe2) with outstanding HER performance. The 3D-MoSe2 is grown by chemical vapor deposition method with using perylene-3, 4, 9, 10-tetracarboxylic acid tetrapotassium salt as a seeding promoter. The as-grown 3D-MoSe2 nanoarchitecture is highly crystalline and constructed with curly few-layered vertical nanosheets onto the horizontal layer, which has much larger (~12 times) electrochemically active area and much smaller (only 2%) charge transfer resistance compared to conventional horizontal MoSe2 layer. With these advantages, the Tafel slope of 3D-MoSe2 can be as small as 47.3 mV/dev, which is the smallest record ever reported for pure MoSe2, even for pure two-dimensional transition metal dichalcogenides (2D-TMDs) catalysts. Furthermore, when 3D-MoSe2 is grown on the multiwall carbon nanotube film, its Tafel slope can be further reduced down to 32.5 mV/dec, which is close to the theoretical limit (29 mV/dec) of HER, and comparable to platinum-based electrocatalysts, making it promising as a highly efficient electrocatalyst for hydrogen evolution.