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Field emission property of vertically aligned nitrogen-doped multi-walled carbon nanotubes produced by chemical vapor deposition
摘要： Vertically aligned nitrogen-doped multi-walled carbon nanotubes (N-MWNTs) were synthesized by the chemical vapor deposition (CVD) at 900 °C using imidazole mixed with ferrocene as carbon and nitrogen sources, and catalyst, respectively. The effects of ammonia (NH3) and hydrogen (H2) flow rates on the growth of N-MWNTs were investigated (hereafter referred to A-N-MWNTs and H-N-MWNTs, respectively). Transmission electron microscopy (TEM) revealed the bamboo-like structure of the N-MWNTs, in which the separation between individual bamboo compartments decreased with increasing nitrogen concentration in N-MWNTs. X-ray photoelectron spectroscopy (XPS) analysis results supported that the nitrogen concentrations in N-MWNTs is 0.55 at.%, whereas A-N-MWNTs and H-N-MWNTs with the flow rate at 10 standard cubic centimeters per minute (sccm) (10A-N-MWNTs and 10H-N-MWNTs, respectively) showed 1.14 and 4.06 at.%, respectively. We found that the optimal conditions for the highest nitrogen-doped multi-walled carbon nanotubes (MWNTs) was a flow rate of NH3 and H2 at 10 sccm. Results from field emission measurements indicated that the turn-on fields of N-MWNTs, 10A-N-MWNTs and 10H-N-MWNTs were 6.7, 4.3 and 3.1 V/μm, respectively, while the field enhancement factors (β) were 5230, 10,805 and 20,390, respectively. Furthermore, the current density of N-MNWTs increased with increasing the nitrogen atoms in MWNTs. The results support that field emission based on N-MWNTs is a good emitter with low turn-on field and large field enhancement factor. Nitrogen doping in MWNTs makes them attractive candidates as high-performance field emitters.
关键词： Field emission,Nitrogen-doped multi-walled carbon nanotubes,Chemical vapor deposition
更新于2025-09-12 10:27:22
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First-principle study of SO2 adsorption on Fe/Co-doped vacancy defected single-walled (8, 0) carbon nanotubes in sensor applications
摘要： To explore the excellent sensor for detecting the pollution gas SO2, the adsorptions of SO2 molecule on the surfaces of Fe/Co-doped carbon nanotubes (CNTs) and single vacancy defected (8, 0) CNTs were investigated by using density functional theory (DFT). In addition, the adsorption energies, geometries, energy gaps and electronic structures were analyzed. The results showed that Fe/Co-doping and single-vacancy-defected can improve the adsorption and sensitiveness of CNTs toward SO2. Considering the changes of energy gap before and after the SO2 molecule adsorbed on each modiˉed CNTs and its adsorption strength, Fe-doped CNTs (Fe-CNTs) and Co-doped site-2 single-vacancy-defected CNTs performed better for detecting SO2 molecule. With the decreasing number of electrons of the doped atom (Fe, Co, Ni), the adsorption became more stable. The results of this paper are profound and meaningful for designing SO2 sensing devices.
关键词： SO2,adsorption,carbon nanotubes,co-doping,vacancy,Fe-doping
更新于2025-09-12 10:27:22
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Optical Voltammetry of Polymer-Encapsulated Single-Walled Carbon Nanotubes
摘要： The semiconducting single-walled carbon nanotube (SWCNT), noncovalently wrapped by a polymeric monolayer, is a nanoscale semiconductor?electrolyte interface under investigation for sensing, photonics, and photovoltaic applications. SWCNT complexes are routinely observed to sensitize various electrochemical/redox phenomena, even in the absence of an external ?eld. While the photoluminescence response to gate voltage depends on the redox potential of the functionalized nanotube, analogous optical voltammetry of carbon nanotubes could be conducted in suspension without applying voltage but by varying the solution conditions as well as the chemistry of the encapsulating polymer. Steady-state photoluminescence, absorbance, and in situ measurements of O2/H2O reactivity show correlation with the pH/pKa-dependent reactivity of π-rich coatings. The nanotube emission responses suggest that the presence of photogenerated potential may explain the observed coating electrochemical reactivity. This work ?nds that electronic and chemical interactions of the nanotube with the encapsulating polymer may play a critical role in applications that depend on radiative recombination, such as optical sensing.
关键词： redox phenomena,optical voltammetry,single-walled carbon nanotubes,photoluminescence,polymer encapsulation
更新于2025-09-12 10:27:22
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Thermodynamic control of quantum defects on single-walled carbon nanotubes
摘要： Single-walled carbon nanotubes with designed quantum defects are prepared and characterized. The photoluminescence (PL) of the nanotubes can be modified by thermal treatment from 1215–1224 to 1249–1268 nm. Theoretical calculations suggest that the change in the PL spectra by thermal treatment can be explained by isomerization from kinetic to thermodynamic products.
关键词： quantum defects,Single-walled carbon nanotubes,photoluminescence,thermal treatment,isomerization
更新于2025-09-12 10:27:22
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Bias Tunable Photocurrent in Metal-Insulator-Semiconductor Heterostructures with Photoresponse Enhanced by Carbon Nanotubes
摘要： Metal-insulator-semiconductor-insulator-metal (MISIM) heterostructures, with rectifying current-voltage characteristics and photosensitivity in the visible and near-infrared spectra, are fabricated and studied. It is shown that the photocurrent can be enhanced by adding a multi-walled carbon nanotube film in the contact region to achieve a responsivity higher than 100 mA W?1 under incandescent light of 0.1 mW cm?2. The optoelectrical characteristics of the MISIM heterostructures are investigated at lower and higher biases and are explained by a band model based on two asymmetric back-to-back Schottky barriers. The forward current of the heterojunctions is due to majority-carrier injection over the lower barrier, while the reverse current exhibits two different conduction regimes corresponding to the diffusion of thermal/photo generated carriers and majority-carrier tunneling through the higher Schottky barrier. The two conduction regimes in reverse bias generate two plateaus, over which the photocurrent increases linearly with the light intensity that endows the detector with bias-controlled photocurrent.
关键词： Schottky junctions,carbon nanotubes,photoconductivity,heterostructures,MISIM
更新于2025-09-12 10:27:22
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Photoswitchable single-walled carbon nanotubes for super-resolution microscopy in the near-infrared
摘要： The design of single-molecule photoswitchable emitters was the first milestone toward the advent of single-molecule localization microscopy, setting a new paradigm in the field of optical imaging. Several photoswitchable emitters have been developed, but they all fluoresce in the visible or far-red ranges, missing the desirable near-infrared window where biological tissues are most transparent. Moreover, photocontrol of individual emitters in the near-infrared would be highly desirable for elementary optical molecular switches or information storage elements since most communication data transfer protocols are established in this spectral range. Here, we introduce a type of hybrid nanomaterials consisting of single-wall carbon nanotubes covalently functionalized with photoswitching molecules that are used to control the intrinsic luminescence of the single nanotubes in the near-infrared (beyond 1 mm). Through the control of photoswitching, we demonstrate super-localization imaging of nanotubes unresolved by diffraction-limited microscopy.
关键词： single-molecule localization microscopy,near-infrared,super-resolution microscopy,carbon nanotubes,photoswitchable emitters
更新于2025-09-12 10:27:22
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Excellent ambipolar gas sensing response of Eu[Pc(OC4H9)8]2/acidified multiwalled carbon nanotubes hybrid at room temperature
摘要： A new hybrid material has been developed by mixing a sandwich-type double-decker, Eu[Pc(OC4H9)8]2 = 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninate] with acidified multiwalled carbon nanotubes (aMWCNTs) through non-covalent interactions. The UV-vis spectrum, X-ray diffraction and scanning electron microscope have been employed to reveal the J-aggregate mode and optimized morphology of Eu[Pc(OC4H9)8]2 molecules in the Eu[Pc(OC4H9)8]2/aMWCNTs hybrid material. The gas-sensing devices based on this hybrid material are fabricated by a simple solvent-processing quasi-Langmuir–Sh?fer (QLS) progress. The n-type and p-type response is shown by the Eu[Pc(OC4H9)8]2/aMWCNTs hybrid film at room temperature. The detection limit of the hybrid for ammonia and nitrogen dioxide gas is 0.5 ppm and 0.3 ppm, respectively.
关键词： phthalocyanine,gas sensing,multiwall carbon nanotubes,ambipolar organic semiconductor,europium complex
更新于2025-09-12 10:27:22
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Preparation and characterization of graphene sheet prepared by laser ablation in liquid
摘要： Graphene sheets prepared successfully by Nd: YAG laser ablation of carbon target immersed in deionized water. The structural, optical and morphological properties investigated using Fourier transform infrared spectroscopy, X-ray diffraction, UV–VIS spectrophotometry, photoluminescence spectroscopy, and Transmission electron microscopy. The result of FTIR spectra conform C?C and C@C bonds, which yield to carbon nanoparticles (CNPs) suspend in liquid. After re-irradiation, new peaks appear at 1723 cm(cid:1)1 and 2697 cm(cid:1)1 caused by the disordered arrangement and irregular layer thickness of graphene sheets. The XRD pattern observed sharp peaks at 2h (cid:3) 24(cid:1), 26.6(cid:1), and 43(cid:1) with higher intensity after the re-irradiation process. The absorption result shows a shoulders peaks among 260 and 320 nm relates to transition in C@O and C@C bands. The PL spectra have a peak in the visible region at 597 nm and increased as laser energy increased. TEM images show straight isolated long multiwall carbon nanotubes MWCNT with the hollow core in different dimensions. While graphene sheet it takes the shape of a ?at transparent layer with small wrinkles and folding sheet, appeared after re-irradiation the suspensions with same laser energy.
关键词： Carbon nanoparticles,Carbon nanotubes,Laser ablation,Graphene sheet
更新于2025-09-11 14:15:04
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Facile preparation and properties of polyvinylidene fluoride dielectric nanocomposites <i>via</i> phase morphology control and incorporation of multiwalled carbon nanotubes conductive fillers
摘要： A novel PVDF dielectric nanocomposite was achieved by controlling phase morphology and incorporating conductive ?llers simultaneously, and the mechanical, thermal, dielectric properties of the resultant dielectric nanocomposites were investigated. Mechanical analysis showed that incorporation of modi?ed MWCNTs (MWCNTs-COOH) in the PVDF nanocomposites resulted in signi?cant improvements on the tensile strength (Ts) and elasticity modulus (Em). When the ?ller content was 12 wt%, the Ts of MWCNTs-COOH/PVDF could reach 64.6 MPa. XRD test showed that the addition of MWCNTs-COOH and MWCNTs promoted the formation of β-phase of PVDF. DMA analysis showed that the glass-transition temperature of the PVDF nanocomposites slightly increases on loading of original MWCNTs and this effect was more pronounced on loading MWCNTs-COOH. The dielectric property analysis showed that the original MWCNTs were more likely to form local conductive networks in the PVDF matrix, promoting the electron displacement polarization, and improving the dielectric constant. When the contents of MWCNTs was 12 wt%, the percolation threshold was obtained and the dielectric constant (ε0) reached 286, which was 36 times of pure PVDF. Our work provides a simple way to fabricate polymer blends with excellent dielectric performances, good mechanical properties as well as good processing capability but low cost.
关键词： polyvinylidene ?uoride (PVDF),thermal performance,dielectric properties,multi-walled carbon nanotubes (MWCNTs),mechanical properties
更新于2025-09-11 14:15:04
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Enrichment of large‐diameter semiconducting single‐walled carbon nanotubes by a mixed‐extractor strategy
摘要： In this work, we report a new mixed-extractor strategy to improve the sorting yield of large-diameter semiconducting single-walled carbon nanotubes (s-SWCNTs) with high purity. In the new mixed-extractor strategy, two kinds of conjugated polymers with different rigidity, poly(9,9-n-dihexyl-2,7-fluorene-alt-9-phenyl-3,6-carbazole) (PDFP) and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (P8BT), are used to sort large-diameter s-SWCNTs through two simple sonication processes. To our surprise, although PDFP itself shows no selectivity toward s-SWCNTs, it can greatly enhance the sorting yield of P8BT. Using the PDFP/P8BT mixed-extractor method, the yield of sorted s-SWCNTs has been enhanced by 5 times with a purity above 99 % in comparison to that using P8BT single-extractor method. In addition, the photoluminescence (PL) excitation maps shows that the PDFP/P8BT mixed-extractor system not only enhances the sorting yield substantially, but also tends to be enrichment of (15,4) SWCNTs with the diameter of 1.36 nm.
关键词： mixed-extractor,high yield and high purity sorting,carbon nanotubes,polymer
更新于2025-09-11 14:15:04