Boron-doped Carbon Nanotubes Research Articles

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.

Electrochemical detection of l-cysteine using a boron-doped carbon nanotube-modified electrode

A boron-doped carbon nanotube (BCNT)-modified glassy carbon (GC) electrode was constructed for the detection of l-cysteine (L-CySH). The electrochemical behavior of BCNTs in response to l-cysteine oxidation was investigated. The response current of L-CySH oxidation at the BCNT/GC electrode was obviously higher than that at the bare GC electrode or the CNT/GC electrode. This finding may be ascribed to the excellent electrochemical properties of the BCNT/GC electrode. Moreover, on the basis of this finding, a determination of L-CySH at the BCNT/GC electrode was carried out. The effects of pH, scan rate and interferents on the response of L-CySH oxidation were investigated. Under the optimum experimental conditions, the detection response for L-CySH on the BCNT/GC electrode was fast (within 7 s). It was found to be linear from 7.8 × 10 −7 to 2 × 10 −4 M ( r = 0.998), with a high sensitivity of 25.3 ± 1.2 nA mM −1 and a low detection limit of 0.26 ± 0.01 μM. The BCNT/GC electrode exhibited high stability and good resistance against interference by other oxidizable amino acids (tryptophan and tyrosine).

Pressure dependence of Meissner effect in films of ropes of boron-doped carbon nanotubes

Superconductivity in carbon nanotubes (CNTs) is attracting considerable attention. Recently, we have reported successful boron doping into single-walled CNTs (SWNTs) and also revealed its correlation with superconductivity. In the present study, we report results of high-pressure magnetization measurements in films consisting of ropes of boron-doped SWNTs. It reveals that T c and magnitude for Meissner effect are mostly independent of applied pressure, while the magnitude of graphite diamagnetism drastically increases as pressure increases. We also report the observation of resistance drop and correlation of boron doping with multi-walled CNTs, in which we reported superconductivity previously.

A first-principles study of nitrogen- and boron-assisted platinum adsorption on carbon nanotubes

We have performed first-principles calculations to investigate the origin of adsorption of platinum on nitrogen- and boron-doped carbon nanotubes (CNTs). Our calculation results reveal that both nitrogen- and boron-doped CNTs can assist the reactivity of platinum adsorption on the CNT surface, although the detailed mechanisms are very different. For nitrogen-doped CNTs, the enhanced adsorption results from activation of the nitrogen-neighboring carbon atoms due to the large electron affinity of nitrogen. In this case, the nitrogen atoms mediate the platinum adsorption enhancement on the CNT surface. In contrast, the enhanced platinum adsorption in boron-doped CNTs can be attributed to the strong hybridization between the platinum d orbital and boron p orbital. Our results explain the experimentally observed enhanced adsorption of platinum on nitrogen-doped CNTs and also suggest that boron-doped CNTs may be a better candidate for fuel cell applications.

Electronic structures and three-dimensional effects of boron-doped carbon nanotubes

We study boron-doped carbon nanotubes by first-principles methods based on the density functional theory. To discuss the possibility of superconductivity, we calculate the electronic band structure and the density of states (DOS) of boron-doped (10,0) nanotubes by changing the boron density. It is found that the Fermi level density of states D(∊F) increases upon lowering the boron density. This can be understood in terms of the rigid band picture where the one-dimensional van Hove singularity lies at the edge of the valence band in the DOS of the pristine nanotube. The effect of three-dimensionality is also considered by performing the calculations for bundled (10,0) nanotubes and boron-doped double-walled carbon nanotubes (10,0)@(19,0). From the calculation of the bundled nanotubes, it is found that interwall dispersion is sufficiently large to broaden the peaks of the van Hove singularity in the DOS. Thus, to achieve the high D(∊F) using the bundle of nanotubes with single chirality, we should take into account the distance from each nanotube. In the case of double-walled carbon nanotubes, we find that the holes introduced to the inner tube by boron doping spread also on the outer tube, while the band structure of each tube remains almost unchanged.

Strain promoted conductivity of doped carbon nanotubes

Strain promoted conductivity is detected in boron-doped carbon nanotubes and conductance biased at 3.5, 3.8, −4.6, −5.7, and −6.4 V exceeds 0.5G0. Deflection induced degeneracy of BC3-π bands accounts for conductance increment.

A novel and simple strategy for selective and sensitive determination of dopamine based on the boron-doped carbon nanotubes modified electrode

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. 238mV) at the BCNTs/GC electrode, which is superior to that at the CNTs/GC electrode (ca. 122mV). Thus, the selective determination of DA was carried out successfully in the presence of AA. A wide concentration range (2.0×10−8–7.5×10−5M) and low detection limit (1.4nM, 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.

Transparent Boron-Doped Carbon Nanotube Films

We report results of studies on the sheet resistance and optical transmission of thin films of boron-doped single-walled carbon nanotubes (SWNTs). Boron doping was carried out by exposure of SWNTs to B 2O 3 and NH 3 at 900 degrees C and 1-3 atom % boron was found in the SWNT bundles via electron energy loss spectroscopy (EELS). Boron doping was found to downshift the positions of the optical absorption bands associated with the van Hove singularities (E 11 (s) E 22 (s) and E 11 (m)) by approximately 30 meV relative to their positions in acid-treated and annealed SWNTs. Raman spectroscopy, EELS, and optical data are consistent with the picture that a few atom % boron has been substituted for carbon in the sp (2) framework of SWNTs. Finally, our results show that boron doping does not significantly affect the optical transmittance in the visible region. However, boron doping lowers the sheet resistance by approximately 30% relative to pristine SWNT films from the same batch. Boron-doped SWNT may provide a better approach to touch-screen technology.

Superconductivity in Thin Films of Boron-Doped Carbon Nanotubes

Superconductivity in carbon nanotubes (CNTs) is attracting considerable attention. However, its correlation with carrier doping has not been reported. We report on the Meissner effect found in thin films consisting of assembled boron (B)-doped single-walled CNTs (B-SWNTs). We find that only B-SWNT films consisting of low boron concentration leads to evident Meissner effect with Tc=12 K and also that a highly homogeneous ensemble of the B-SWNTs is crucial. The first-principles electronic-structure study of the B-SWNTs strongly supports these results.

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.

Resistivity reduction of boron-doped multiwalled carbon nanotubes synthesized from a methanol solution containing boric acid

Boron-doped multiwalled carbon nanotubes (MWNTs) were synthesized using a methanol solution of boric acid as a source material. Accurate measurements of the electrical resistivity of an individual boron-doped MWNT was performed with a four-point contact, which was fabricated using an electron beam lithography technique. The doped boron provides conduction carriers, which reduces the resistivity of the MWNT.

Amperometric glucose biosensor based on boron-doped carbon nanotubes modified electrode

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.

Electronic structure of boron-doped carbon nanotubes

We study boron-doped single-walled carbon nanotubes by using first-principles methods based on the density functional theory. The total energy, band structure, and density of states are calculated. From the formation energy of boron-doped nanotubes with different diameters, it is found that a narrower tube needs a smaller energy cost to substitute a carbon atom with a boron atom. By using the result of different doping rates in the (10,0) tube, we extrapolate the result to low boron density limit and find that the ionization energy of the acceptor impurity level should be approximately 0.2 eV. Furthermore, we discuss the doping rate dependence of the density of states at the Fermi level, which is important to realize superconductivity.

Boron-doped carbon nanotubes modified electrode for electroanalysis of NADH

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.

Synthesis and characterization of boron-doped carbon nanotubes

Boron-doped carbon nanotubes have been prepared by chemical vapour deposition of ethyl alcohol doped with B2O3 using a hot-filament system. Multi-wall carbon nanotubes of diameters in the range of 30 – 100 nm have been observed by field emission scanning electron microscopy (FESEM). Raman measurements indicated that the degree of C-C sp2 order decreased with boron doping. Lowest threshold fields achieved were 1.0 V/μm and 2.1 V/μm for undoped and boron-doped samples, respectively.

Direct growth of carbon nanotube junctions by switching source gases in a continuous chemical vapor deposition

A new method is used to directly grow carbon nanotube (CNT) junctions with two different structures through a continuous chemical vapor deposition (CVD) process. CH 4/B 2H 6/H 2 and CH 4/H 2 source gases were used as the feeding gas, respectively. By switching between different source gases in the CVD process, the junctions composed of boron-doped and pure CNTs were prepared. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the structure and composition of such junctions. The results show that each junction is having a bamboo boron-doped CNT at one side and a hollow CNT at another side, and the two different structures are connected with each other successfully.

Nitrogen- and Boron-Doped Double-Walled Carbon Nanotubes

Double-walled carbon nanotubes (DWNTs) doped with nitrogen and boron have been prepared by the decomposition of a CH(4) + Ar mixture along with pyridine (or NH(3)) and diborane, respectively, over a Mo(0.1)Fe(0.9)Mg(13)O catalyst, prepared by the combustion route. The doped DWNTs bave been characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, electron energy loss spectroscopy, and Raman spectroscopy. The dopant concentration is around 1 atom % for both boron and nitrogen. The radial breathing modes in the Raman spectra have been employed along with TEM to obtain the inner and outer diameters of the DWNTs. The diameter ranges for the undoped, N-doped (pyridine), N-doped (NH(3)), and B-doped DWNTs are 0.73-2.20, 0.74-2.30, 0.73-2.32, and 0.74-2.36 nm, respectively, the boron-doped DWNTs giving rise to a high proportion of the large diameter DWNTs. Besides affecting the G-band in the Raman spectra, N- and B-doping affect the proportion of semiconducting nanotubes.

Direct electrochemistry of glucose oxidase and biosensing for glucose based on boron-doped carbon nanotubes modified electrode

Due to their unique physicochemical properties, doped carbon nanotubes are now extremely attractive and important nanomaterials in bioanalytical applications. In this work, selecting glucose oxidase (GOD) as a model enzyme, we investigated the direct electrochemistry of GOD based on the B-doped carbon nanotubes/glassy carbon (BCNTs/GC) electrode with cyclic voltammetry. A pair of well-defined, quasi-reversible redox peaks of the immobilized GOD was observed at the BCNTs based enzyme electrode in 0.1 M phosphate buffer solution (pH 6.98) by direct electron transfer between the protein and the electrode. As a new platform in glucose analysis, the new glucose biosensor based on the BCNTs/GC electrode has a sensitivity of 111.57 μA mM −1 cm −2, a linear range from 0.05 to 0.3 mM and a detection limit of 0.01 mM (S/N = 3). Furthermore, the BCNTs modified electrode exhibits good stability and excellent anti-interferent ability to the commonly co-existed uric acid and ascorbic acid. These indicate that boron-doped carbon nanotubes are the good candidate material for the direct electrochemistry of the redox-active enzyme and the construction of the related enzyme biosensors.

Boron-doped carbon nanotube coating for transparent, conducting, flexible photonic devices

Conducting transparent polymer materials were made by applying boron-doped single-walled carbon nanotubes to the surfaces of glass and flexible polyethylene terephthalate film substrates. Optical transmission and sheet resistance measurements showed that the boron-doped coated samples had sheet resistances of ∼7kΩ∕◻ and flat optical transmission of ∼89% for visible light. Temperature and humidity tests showed that the materials remained conductive after nearly 150h of testing. The materials are robust and even maintain their conducting properties after being folded. Fabrication of a simple light emitting device demonstrates usage of the material as a flexible transparent electrode.