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Synthesis of Na-, Fe-, and Co-promoted TiO$_{2}$/multiwalled carbon nanotube composites and their use as a photocatalyst
摘要： The use of multiwalled carbon nanotubes (CNTs) in sol-gel synthesized titanium dioxide (TiO 2) photocatalysts as templates was systematically studied. CNTs have high oxidative thermal stability and the controlled removal of CNTs can be achieved at lower temperatures under air (cid:13)ow by the use of Na, Fe, and Co as a catalyst. These catalysts helped to reduce the oxidation temperature of CNTs; thus anatase phase was achieved without signi(cid:12)cant sintering. The use of a promoter, heat treatment, and various heat treatment atmospheres was e?ective in speci(cid:12)c surface area, crystallinity, and photocatalytic activity against methylene blue (MB) degradation. While the speci(cid:12)c surface area of bare TiO 2 was 22 m 2 /g, after templating surface areas as high as 191 m 2 /g were obtained. For the photocatalytic characterization, with bare TiO 2 , the rate constant for MB decomposition was 0.81 h (cid:0)1 , and for CNT{TiO 2 it was 1.31 h (cid:0)1 . Moreover, after Na promotion, the rate constant increased to 1.85 h (cid:0)1 . The results showed that CNTs can be used as a template to tailor and improve the textural properties. Moreover, as a novel material, the Na promotion in CNT{TiO 2 samples showed the best photocatalytic activity by enhancing the interaction between TiO 2 and CNT surfaces.
关键词： anatase,Carbon nanotubes,TiO 2,doping,sol-gel,template,photocatalysis,composite
更新于2025-09-16 10:30:52
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[IEEE 2018 48th European Microwave Conference (EuMC) - Madrid (2018.9.23-2018.9.27)] 2018 48th European Microwave Conference (EuMC) - Carbon Nanotube Layer Modeling for Computer Simulation of Optically Controlled Phase Shifters
摘要： We propose an approach for efficient modeling of thin carbon nanotube layers for full-wave device simulations without increasing the number of simulation mesh cells. A surface impedance, used in computer simulations, is calculated from the dielectric constant of the material. The dielectric constant is modeled by a Drude–Lorentz resonance, fitted to experimental results. The approach allowed to study the nanotube-induced losses and finite-size resonance effects in optically-controlled, dielectric rod waveguide-based phase shifters. The correctness of the model was verified both by the simulated and the measured S-parameters in the W-band.
关键词： numerical simulation,optically controlled phase shifter,surface impedance,millimeter waves,carbon nanotubes
更新于2025-09-16 10:30:52
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Near-field infrared microscopy of nanometer-sized nickel clusters inside single-walled carbon nanotubes
摘要： Nickel nanoclusters grown inside single-walled carbon nanotubes (SWCNT) were studied by infrared scattering-type scanning near-field optical microscopy (s-SNOM). The metal clusters give high local contrast enhancement in near-field phase maps caused by the excitation of free charge carriers. The experimental results are supported by calculations using the finite dipole model, approximating the clusters with elliptical nanoparticles. Compared to magnetic force microscopy, s-SNOM appears much more sensitive to detect metal clusters inside carbon nanotubes. We estimate that these clusters contain fewer than 700 Ni atoms.
关键词： s-SNOM,infrared scattering-type scanning near-field optical microscopy,magnetic force microscopy,single-walled carbon nanotubes,Nickel nanoclusters
更新于2025-09-16 10:30:52
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Single-walled carbon nanotube membranes for optical applications in the extreme ultraviolet range
摘要： In this paper, we explore the possibility of using free-standing thin films from single-walled carbon nanotube (SWCNT) material in optics of the extreme ultraviolet (EUV) range. Test samples were fabricated using an aerosol chemical vapor deposition method. Synchrotron radiation was used to record the transmittance spectra of samples in the EUV range. The measured transmittance for a film 40 nm thick almost monotonously increases from 76% at a wavelength of 20 nm to 99% at a wavelength of 1 nm. The measured stress-strain curve for the test samples shows that the SWCNT-based thin films have rather high ductility as opposite to fragile films made of conventional solid state materials. We use numerical simulations to demonstrate that the film strain occurs mainly by straightening and sliding of the nanotubes past each other without forming of strain localization responsible for fragile behavior. The combination of high radiation transmittance and unique mechanical properties makes the SWCNT-based thin films very promising for use in the EUV optics. In particular, such films can be used to protect delicate optical elements for EUV lithography from their contamination with debris particles.
关键词： Transmittance,Optics,Single-walled carbon nanotubes,Extreme ultraviolet,Mechanical properties
更新于2025-09-16 10:30:52
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Enhancement of curcumin antitumor efficacy and further photothermal ablation of tumor growth by single-walled carbon nanotubes delivery system <i>in vivo</i>
摘要： Curcumin, a commonly used natural product for antitumor therapy, is unable to achieve full potential due to poor bioavailability. Based on our previous report of a novel delivery system for curcumin using functionalized single-walled carbon nanotubes by phosphatidylcholine and polyvinylpyrrolidone (SWCNT-Cur), we further evaluated SWCNT-Cur’s performance in vivo and characteristics in vitro. SWCNT-Cur significantly increased the blood concentration of curcumin, up to 18-fold, in mice. And in a murine S180 tumor model, SWCNT-Cur exhibited significantly higher inhibition efficacy on tumor growth and no obvious toxicity in main organs. Moreover, photothermal therapy induced by SWCNT under near-infrared radiation further facilitated SWCNT-Cur to inhibit the tumor growth in vivo. In addition, solvent residue is negligible in SWCNT-Cur formulation, and hydrogen bonding was formed between void carriers and curcumin, as demonstrated by GC chromatograph and IR spectra. Furthermore, experiments of confocal microscopy and spectrofluorometer showed that SWCNT-Cur gave a six-fold higher uptake for curcumin compared to native curcumin in human prostate cancer PC-3 cells. In conclusion, curcumin delivery with functionalized SWCNT is a promising strategy to enhance anticancer activity in vivo by enhancing cell uptake and blood concentration, changing physicochemical properties of curcumin and combining phototherapeutic with chemotherapeutic effects.
关键词： cancer therapy,Curcumin,nanocarriers,single-walled carbon nanotubes,photothermal effect
更新于2025-09-16 10:30:52
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Field emission enhancement of PbS colloidal quantum dot-decorated single-walled carbon nanotubes
摘要： Herein, a simple and effective PbS colloidal quantum dot (CQD) decoration method for single-walled carbon nanotube (SWNT) is demonstrated. By dipping the SWNT film into a CQD dispersion followed by a solid-state ligand exchange, CQDs were successfully decorated onto the wall of SWNT without compromising a narrow size distribution. Spectroscopic studies suggested that (1) the CQD decoration and subsequent ligand exchange process did not alter the chemical nature of the SWNT framework and (2) there was a charge (electron) transfer process from the PbS CQD to the SWNT. Field emission (FE) characteristics of the CQD-decorated SWNT films revealed that FE enhancement was indeed established from SWNTs with a moderate degree of CQD decoration, while those with excessive decoration (coating) exhibited notable FE suppression. Horizontal current-voltage measurements with perpendicular-directional external electric field modulation suggested that electron supplement of SWNT from PbS CQD was pronounced as the amount of decorated CQDs increased. Based on the experimental results, we proposed a new mechanism demonstrating FE enhancement of a CQD/SWNT heterostructure.
关键词： Charge transfer,Field emission,Single-walled carbon nanotubes,Quantum dots,Ligand-exchange
更新于2025-09-16 10:30:52
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Theoretical investigation of electronic bandgaps of semiconducting single-walled carbon nanotubes using semi-empirical self-consistent tight binding and <i>ab-inito</i> density functional methods
摘要： We perform a comprehensive theoretical study of electronic band gaps of semiconducting single-walled carbon nanotubes (SWNTs) with different sets of chiral indices using semi-empirical tight binding and density functional (DFT) based ab-initio methods. In particular, self-consistent extended Huckel (EH-SCF) and self-consistent Slater Koster (SK-SCF) tight binding models are used as semi-empirical methods, whereas the DFT based LDA-1/2 and Tran-Blaha (TB09) meta-GGA schemes are used as ab-initio methods. The calculations are performed for 1) (n, m) chiral SWNTs for which experimental optical gaps have been reported 2) (9, 0), (12, 0) and (15, 0) ‘metallic’ zigzag SWNTs for which small bad gaps have been reported 3) Pairs of SWNTs having same diameters but different chiral angles 4) (n, 0) zigzag SWNTs with ? ?n 30. From the comparison of bands gaps of tubes with same diameter, the electronic band gaps are found to vary with chiral angles with opposing trend as compared to that reported for experimental optical band gaps. This result may be expected to have important implications for self-energy corrections and/or exciton binding energies and their dependence on chiral angles. The hopping parameter g0 obtained from ?tting EH-SCF and SK-SCF bandgap data, is found to be in good agreement with that obtained from ?tting experimental data. In general, the band gap values of SWNTs computed using semi-empirical EH-SCF and SK-SCF methods are quite close (within ～ 5%) to those computed using DFT-based LDA-1/2 and TB09 meta-GGA methods. The results suggest that self-consistent semi-empirical methods can be expected to provide similar accuracy in results as that expected from more computationally challenging ab-intio DFT based LDA-1/2 and TB09 meta-GGA methods.
关键词： self-consistent tight binding method,semiconducting carbon nanotubes,electronic structure,first principles calculations
更新于2025-09-16 10:30:52
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Broadening of van Hove Singularities Measured by Photoemission Spectroscopy of Single and Mixed Chirality Single-Walled Carbon Nanotubes
摘要： The occupied valence electronic states of single walled carbon nanotubes (SWCNTs) are responsible for their optoelectronic properties and are unique for each SWCNT chirality. Photoemission spectroscopy (PES) is one of the few methods capable of directly measuring the electron density in the valence states of materials but there are only few reports which have observed the valence states of SWCNTs and no examples for single-chirality SWCNTs. Here we prepare single and mixed chirality SWCNT films and characterise their valence states using PES. Chirality pure SWCNTs were isolated using both gel permeation chromatography and ssDNA facilitated aqueous two phase extraction from starting materials consisting of mixed chirality species. Chirality separation and purity was confirmed with UV-Vis-nIR absorption spectroscopy. SWCNT films were prepared for the single chirality species (10,3), (7,6), (7,3), (6,5), (8,3), (9,1) along with SWCNT chirality mixture of metallic and semiconducting SWCNTs, and as-synthesised mixtures possessing a range of SWCNT diameter. PES using synchrotron radiation was completed for all samples with survey and C 1s core level spectra obtained to confirm SWCNT coverage, defect level and purity. Valence band PES was obtained to characterise the valence electronic states and showed significant broadening of the signal, in comparison to calculated density of states, which could not be accounted for by instrument resolution. An inverse diameter dependence of the broadening was observed with greater broadening for smaller diameter SWCNTs. The broadening is hypothesised to be related to the photohole lifetime which was found to be significantly longer for wide diameter SWCNTs. The diameter dependence of the broadening and photohole lifetimes is discussed in terms of both Tomonaga-Luttinger and Landau theory of Fermi liquids.
关键词： chirality,valence electronic states,single-walled carbon nanotubes,van Hove singularities,photoemission spectroscopy
更新于2025-09-16 10:30:52
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Ni3S2@MWCNTs films for effective counter electrodes of dye-sensitized solar cells
摘要： Composite films nickel sulfide (Ni3S2) nanoparticles were grown on multiwall carbon nanotubes (MWCNTs) and in situ coated onto conducting glass substrates by the hydrothermal process at 170 °C. These Ni3S2@MWCNTs films were applied for counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). In this work, nanostructure, crystalline structure, electrochemical activities and electron-charge transfer resistance of CEs were studied. In addition, the effective surface areas of CEs were analyzed and discussed as well. The power conversion efficiency (PCE) enhancement of up to 7.48%, compared with that of Ni3S2-DSSC, was demonstrated for a Ni3S2@MWCNTs DSSC.
关键词： Counter electrode,Ni3S2,Dye-sensitized solar cell,Hydrothermal method,Multiwall carbon nanotubes
更新于2025-09-16 10:30:52
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Covalent Surface Modification Effects on Singlea??Walled Carbon Nanotubes for Targeted Sensing and Optical Imaging
摘要： Optical nanoscale technologies often implement covalent or noncovalent strategies for the modification of nanoparticles, whereby both functionalizations are leveraged for multimodal applications but can affect the intrinsic fluorescence of nanoparticles. Specifically, single-walled carbon nanotubes (SWCNTs) can enable real-time imaging and cellular delivery; however, the introduction of covalent SWCNT sidewall functionalizations often attenuates SWCNT fluorescence. Recent advances in SWCNT covalent functionalization chemistries preserve the SWCNT’s pristine graphitic lattice and intrinsic fluorescence, and here, such covalently functionalized SWCNTs maintain intrinsic fluorescence-based molecular recognition of neurotransmitter and protein analytes. The covalently modified SWCNT nanosensor preserves its fluorescence response towards its analyte for certain nanosensors, presumably dependent on the intermolecular interactions between SWCNTs or the steric hindrance introduced by the covalent functionalization that hinders noncovalent interactions with the SWCNT surface. These SWCNT nanosensors are further functionalized via their covalent handles with a targeting ligand, biotin, to self-assemble on passivated microscopy slides, and these dual-functionalized SWCNT materials are explored for future use in multiplexed sensing and imaging applications.
关键词： single-walled carbon nanotubes,biosensing,fluorescence,imaging,surface functionalization
更新于2025-09-16 10:30:52