Boron-doped Multiwalled Carbon Nanotubes Research Articles

Boron-doped multi-walled carbon nanotubes as sensing material for analysis of dopamine and epinephrine in presence of uric acid

Boron-doped multi-walled carbon nanotubes (B-MWCNTs) were synthesized, treated with hydrochloric acid, “piranha” solution, and decorated with gold nanoparticles (AuNPs). B-MWCNTs were characterized using Raman spectroscopy, scanning electron- and transmission electron microscopy, and electrochemical techniques. The results exhibit enhanced response and sensitivity of B-MWCNTs upon modification with AuNPs. Analysis of dopamine (DA) and epinephrine (EP) in presence of uric acid (UA) was investigated on B-MWCNTs/AuNPs in pig blood serum. Limits of detection of 0.20 and 0.30 μM were estimated for DA and EP, respectively. The findings demonstrate that B-MWCNTs/AuNPs is proper for analysis of DA and EP under coexistence of UA.

Localized plasmon resonance in boron-doped multiwalled carbon nanotubes

Localized plasmon resonance in boron-doped multiwalled carbon nanotubes

Removal of bisphenol A by electrochemical carbon-nanotube filter: Influential factors and degradation pathway

Bisphenol A is a chemical with hazardous health effects that is largely used in the manufacture of extensively used products including adhesives, plastics, powder paints, thermal paper and paper coatings, and epoxy resin, and is reported to exist in nature in an accumulative manner. In this study, both pristine and boron-doped multiwalled carbon nanotubes (MWNTs) were employed as filtration and electrochemical filtration materials, resulting in a significant removal of bisphenol A with identical performance for both MWNTs types. It was shown that the presence of salt is not critical for the greatest contaminant removal efficiency, likely due to the vital role of other electroactive species (e.g. reactive oxygen species). Near complete removal of 1 mg L−1 bisphenol A at 2 and 3 V of applied DC potentials was achieved, indicating that the electrochemical filtration process is voltage dependent at both 2 and 3 V. Increasing the residence time by 7.4 fold (from 2.0 to 14.9 s) resulted in a significant removal of bisphenol A and its toxic byproducts, up to 424 min of electrochemical filtration time at 3 V of applied potential. Based on these results, electrochemical filtration using MWNTs is considered a promising technology for the removal of the accumulative bisphenol A and the reduction of its hazardous effects in waters.

Thermally Stable Boron-Doped Multiwalled Carbon Nanotubes as a Pt-free Counter Electrode for Dye-Sensitized Solar Cells

A polymeric dispersant is usually used for preparing the uniform multiwalled carbon nanotubes (CNT) film for replacing Pt as the catalyst on the counter electrode (CE) of dye-sensitized solar cells (DSSCs). However, it is necessary to remove the polymeric dispersant completely due to its nonconductive property. Herein, boron-doped CNT (BCNT) with enhanced thermal stability, as the benefit to the dispersant removal, was prepared as the catalyst on the CE of a DSSC, and the cells with pristine CNT and Pt as the catalyst on the CEs were compared. The BCNT based DSSC shows the best light-to-electricity conversion efficiency (η) of 7.91 ± 0.21%, which is higher than that of the cell with a CNT CE (η = 6.02 ± 0.19%) and is comparable to that of the cell with a Pt CE (η = 8.03 ± 0.11%).

A Polysulfide-Trapping Interface for Electrochemically Stable Sulfur Cathode Development

Lithium-sulfur (Li-S) cells have a strong edge to become an inexpensive, high-capacity rechargeable battery system. However, currently, several prohibitive challenges occur within the sulfur core, especially the polysulfide-diffusion problem. To address these scientific issues, we present here a boron-doped multiwalled carbon nanotube coated separator (B-CNT-coated separator). The B-CNT-coated separator creates a polysulfide trap between the pure sulfur cathode and the polymeric separator as a "polysulfide-trapping interface," stabilizing the active material and allowing the dissolved polysulfides to activate the bulk sulfur cores. Therefore, the dissolved polysulfides change from causing fast capacity fade to assisting with the activation of bulk sulfur clusters in pure sulfur cathodes. Moreover, the heteroatom-doped polysulfide-trapping interface is currently one of the missing pieces of carbon-coated separators, which might inspire further studies in its effect and battery chemistry. Li-S cells employing B-CNT-coated separators (i) exhibit improved cyclability at various cycling rates from 0.2C to 1.0C rate and (ii) attain a high capacity retention rate of 60% with a low capacity fade rate of 0.04% cycle(-1) after 500 cycles. We believe that our B-CNT-coated separator could light up a new research area for integrating heteroatom-doped carbon into the flexible, lightweight, carbon-coated separator.

Properties and electrochemical characteristics of boron-doped multi-walled carbon nanotubes

Boron-doped multi-walled carbon nanotubes were synthesized upon decomposition of ethyl alcohol and boric acid via chemical vapor deposition. The boron-doped nanotubes were treated with hydrochloric acid and were characterized by means of scanning electron and transmission electron microscopy in conjunction with energy-dispersive X-ray spectrometry and X-ray photoelectron spectroscopy. The electrochemistry of ferrocyanide/ferricyanide on boron-doped nanotubes was studied in temperature range of 283.15–303.15K. The findings exhibit an improvement of films’ current response and kinetics of electron transfer with the rise in temperature. The kinetics for electron transfer enhances and the redox process occurs slightly more spontaneously upon acid treatment.

Multi-walled carbon nanotubes doped with boron as an electrode material for electrochemical studies on dopamine, uric acid, and ascorbic acid

Boron-doped multi-walled carbon nanotubes (B-MWCNTs) were deposited on oxidized silicon substrate via decomposition of ethanol and boric acid in the presence of the catalyst ferrocene by means of chemical vapor deposition in a thickness of typically 900 nm. The B-MWCNTs were characterized using Raman spectroscopy and scanning electron microscopy and transmission electron microscopy in combination with energy dispersive X-ray spectroscopy. The deposited B-MWCNTs were electrochemically characterized using the ferrocyanide/ferricyanide redox system by means of cyclic voltammetry and electrochemical impedance spectroscopy. The response of B-MWCNTs towards oxidation of dopamine (DA), uric acid (UA), and ascorbic acid (AA) was studied. DA, UA and AA can be determined at working potentials of typically 0.267, 0.412, and 0.127 V (vs. Ag/AgCl) with detection limits of 0.11, 0.65, and 1.21 μM, respectively.

Ag Nanoparticles on Boron Doped Multi-walled Carbon Nanotubes as a Synergistic Catalysts for Oxygen Reduction Reaction in Alkaline Media

Here we report the oxygen reduction reaction (ORR) activity of Ag nanoparticles supported on boron doped multi-walled carbon nanotubes (Ag/B-MWCNTs) with different Ag loadings synthesized by a facile chemical method. Transmission electron microscopy (TEM) and X-ray diffraction patterns (XRD) measurements were employed to investigate the morphology and crystal structure of the as-prepared catalysts. The electrochemical results demonstrated that all the Ag/B-MWCNTs samples catalyzed the ORR in alkaline media by an efficient four-electron pathway. Furthermore, Ag/B-MWCNTs with lowest Ag loading (20%) performed the highest mass activity towards ORR mainly due to the synergistic effect of Ag nanoparticles and B-MWCNTs. This work brings insight into the role of supporting materials in reducing the loading of metal catalyst towards low-cost ORR in alkaline media.

Boron Doped Multi-walled Carbon Nanotubes as Catalysts for Oxygen Reduction Reaction and Oxygen Evolution Reactionin in Alkaline Media

The boron doped multi-walled carbon nanotubes (B-MWCNTs) were synthesized by thermal annealing multi-walled carbon nanotubes (MWCNTs) in the presence of boric acid. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) results revealed that the structure of MWCNTs does not be destroyed during the doping process, and X-ray photoelectron spectroscopy (XPS) analysis demonstrated the boron atoms were successfully doped in the structure of MWCNTs. The electrocatalytic properties of B-MWCNTs are characterized by rotating disk electrode (RDE) methods. The results demonstrated that the B-MWCNTs catalyzed oxygen reduction reaction (ORR) in alkaline media by a 2+2 electron pathway and it showed good catalytic activity for oxygen evolution reaction (OER) as well.

Undoped, nitrogen-doped and boron-doped multiwalled carbon nanotube/poly(vinyl alcohol) composite as active layer in simple hydrostatic pressure sensors

We report on hydrostatic pressure sensors prepared using 10 % w/w multiwalled carbon nanotube (MWCNT)/poly(vinyl alcohol) composites. Three types of carbon nanotubes were used in the composites: undoped MWCNTs, nitrogen-doped MWCNTs and boron-doped MWCNTs (B-MWCNTs). The sensor response was tested using an alternating current input, measuring the capacitance and conductance outputs. The sensors based on the three composites show a linear capacitance and conductance sensitivity pressure dependence in the range 50–120 kPa, but a higher sensitivity to pressure dependence above this interval. The highest angular coefficient of the sensitivity, which reached 0.092 kPa−1, was observed for the capacitance sensitivity of the B-MWCNT based composite.

Nitrogen-doped, boron-doped and undoped multiwalled carbon nanotube/polymer composites in WORM memory devices

We report the preparation of write-once-read-many times memory devices using composites of carbon nanotubes and poly(vinyl phenol) sandwiched between Al electrodes. Three types of nanotubes (undoped multiwalled carbon nanotubes, nitrogen-doped multiwalled carbon nanotubes and boron-doped multiwalled carbon nanotubes) are investigated for this application. The OFF to ON state switching threshold is only slightly dependent on nanotube type, but the ON/OFF current ratio depends on both nanotube type and concentration and varies up to 106, decreasing for nanotube concentrations larger than 0.50 wt% in the composite.

Effect of Pressure on the Electrical Resistance of Individual Boron-Doped Carbon Nanotubes

The electrical resistance of an individual boron-doped multi-walled carbon nanotube was measured under high pressure up to 1.73 GPa. The resistance decreased drastically when pressure was applied. The temperature dependence of the resistance was explained by a variable range hopping transport model, and the dimensionality was observed to change from one to three dimensions with increasing pressure.

Preparation and characteristic of platinum catalyst deposited on boron-doped carbon nanotubes

In this work, boron doped multi-walled carbon nanotubes (BMWNTs) were introduced as a Pt catalyst support due to their unique physicochemical properties. The effect of BMWNTs on methanol oxidation was investigated with different Pt loading contents. The surface and structural properties of the modified MWNT supports were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The Pt loading contents in the catalysts were confirmed by inductive coupled plasma-mass spectrometer (ICP-MS) and the morphological structures of the catalysts were analyzed by transmission electron microscopy (TEM). The electrocatalytic activity of Pt/MWNTs was investigated by cyclic voltammetry measurement. As a result, the boron oxide vapor reacted with MWNTS to form BMWNTs, which led to enhancing the properties, such as graphitization and electrochemical behaviors. Moreover, Pt deposited on BMWNTs exhibited better electrocatalytic activity than on MWNTs for methanol oxidation. Consequently, it was found that partial boron doped MWNTs could influence on the properties of the MWNTs, resulting in enhancing the electrocatalytic activity of the catalysts for DMFCs.

Comparison of structural changes in nitrogen and boron-doped multi-walled carbon nanotubes

We investigated the effect of the reaction parameters on the structure of multi-walled carbon nanotubes containing different concentrations of nitrogen and boron. The nanotubes were produced using a ‘standard’ aerosol chemical vapour deposition technique in conjunction with benzylamine, triethylborane, hexane and toluene mixtures. These precursors were thermally decomposed between 800 and 1100 °C under argon at atmospheric pressure. By varying the precursor concentrations, the nitrogen and boron content of the nanotubes could be altered between 0–2.2 and 0–0.5 at.% respectively. Using a typical laboratory-sized 50 cm long tube furnace, yields between 0.3 and 1.5 g of nanotubes/10 min were relatively easily achieved. Moreover, we show that doping carbon nanotubes with heteroatoms, such as B and N, can be used to control nanotube diameters, change their defect density, and manipulate their oxidation resistance within a range of ca. 170 °C. Hence, we show that it is possible to tune nanotube properties within a certain interval and to produce nanotubes with relatively well defined properties in quantities usable for further characterisation and for studying their viability in applications such as composite materials, gas sensors, capacitors, and electronic components.

Erratum: An EELS study on an individual boron-doped multi-walled carbon nanotube [Tanso 239: 162-168 (2009)

Erratum: An EELS study on an individual boron-doped multi-walled carbon nanotube [Tanso 239: 162-168 (2009)

An EELS study of an individual boron-doped multi-walled carbon nanotube

An EELS study of an individual boron-doped multi-walled carbon nanotube

Electrical properties of boron-doped MWNTs synthesized by hot-filament chemical vapor deposition

We have synthesized a large amount of boron-doped multiwalled carbon nanotubes (MWNTs) by hot-filament chemical vapor deposition. The synthesis was carried out in a flask using a methanol solution of boric acid as a source material. The scanning electron microscopy, transmission electron microscopy, and micro-Raman spectroscopy were performed to evaluate the structural properties of the obtained MWNTs. In order to evaluate the electrical properties, temperature dependence of resistivity was measured in an individual MWNTs with four metal electrodes. The Raman shifts suggest carrier injection into the boron-doped MWNTs, but the resistivity of the MWNTs was high and increased strongly with decreasing temperature. Defects induced by the plasma may cause this enhanced resistivity.

An EELS study on an individual boron-doped multi-walled carbon nanotube

A pellet of as-grown multi-walled carbon nanotubes (MWNTs) prepared by compression was heat-treated at 3000°C for 30 min to eliminate metal impurities and a piece of the 3000°C-treated pellet was boron doped with a diffusion method. Electron energy loss (EEL) spectrum measurements for an individual boron-doped MWNT (B-MWNT) selected from the boron doped pellet were taken along the central line of the high resolution transmission electron microscope image, i.e. the line of the MWNT axis of the individual B-MWNT. Along the central line, a K-shell excitation EEL spectrum composed of two spectra, a weak boron K-shell excitation EEL spectrum and a strong carbon K-shell excitation EEL spectrum, was obtained at some positions, while at other positions only a carbon K-shell excitation EEL spectrum was recorded. Semi quantitative analysis of the energy loss near the edge structure of the boron K-edge revealed that boron doping had taken place quite locally in the individual B-MWNT.

Physical properties of CVD boron-doped multiwalled carbon nanotubes

The effects of boron doping and electron correlation on the transport properties of CVD boron-doped multiwalled carbon nanotubes are reported. The boron-doped multiwalled carbon nanotubes were characterized by TEM as well as Raman spectroscopy using different laser excitations (viz. 488, 514.5 and 647 nm). The intensity of the D-band laser excitation line increased after the boron incorporation into the carbon nanotubes. The G-band width increased on increasing the boron concentration, indicating the decrease of graphitization with increasing boron concentration. Electrical conductivity of the undoped and boron-doped carbon nanotubes reveal a 3-dimensional variable-range-hopping conductivity over a wide range of temperature, viz. from room temperature down to 2 K. The electrical conductivity is not found to be changed significantly by the present levels of B-doping. Electron Paramagnetic Resonance (EPR) results for the highest B-doped samples showed similarities with previously reported EPR literature measurements, but the low concentration sample gives a very broad ESR resonance line.

New synthesis and physical property of low resistivity boron-doped multi-walled carbon nanotubes

A novel growth technique of boron-doped multi-walled carbon nanotubes (MWNTs) was developed. Our new technique uses a methanol solution of boric acid as a source material. Resistivity of the boron-doped MWNTs was successfully reduced independently of chirality by our technique. Temperature dependence of resistivity in each individual boron-doped MWNT was measured by using small-sized four-point contacts, which were fabricated by electron beam (EB) lithography technique. Conduction carriers were introduced into the MWNT effectively by boron-doping.