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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
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Highly ordered combined structure of anodic TiO2 nanotubes and TiO2 nanoparticles prepared by a novel route for dye-sensitized solar cells
摘要： Combined structure of anodic TiO2 nanotubes and TiO2 nanoparticles (TiNTs-TiNPs) has been synthesized by a facile combination of hydrothermal and chemical vapor deposition methods. Ordered TiO2 nanotubes with smooth walls were fabricated by two step anodization method in ethylene glycol containing NH4F at 50V. This nanotubular array after annealing at 450 oC was subjected to the hydrothermally produced gaseous environment in an autoclave with diluted TiCl4 solution at its bottom. Vapors of TiCl4 were allowed to react chemically with water vapors for predefined time durations at 180 oC that resulted in the deposition of TiO2 nanoparticles on tubes’ surface and side walls. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that for one hour reaction duration, nanoparticles were evenly coated on the walls of nanotubes, whereas, longer durations tend to deteriorate the tubular structure. Consequently, the ordered TiNTs-TiNPs array produced after one hour coating has shown better performance for dye-sensitized solar cell DSSC) in back illumination mode with 130 % increase in efficiency as compared to the device based on bare TiO2 nanotubes. The same photoanode has higher reflective properties with higher scattering ability. The solar cell based on this photoanode exhibits higher external quantum efficiency and effective charge transport properties. This study shows that porous ordered 1D structures based on TiO2 are of crucial importance for the high performance of DSSCs.
关键词： TiO2 nanotubes,anodization,ordering,TiO2 nanoparticles,hydrothermal
更新于2025-09-11 14:15:04
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Characterization of the Electronic Properties of Single‐Walled Carbon Nanotubes Filled with an Electron Donor—Rubidium Iodide: Multifrequency Raman and X‐ray Photoelectron Spectroscopy Studies
摘要： Single-walled carbon nanotubes (SWCNTs) with a mean diameter of 1.4 nm are filled with rubidium iodide. The filling of nanotubes is proved by high-resolution scanning transmission electron microscopy. The chemical composition of the filler is confirmed by X-ray photoelectron spectroscopy (XPS). The electronic properties of the filled SWCNTs are studied by XPS and Raman spectroscopy. The encapsulated salt leads to n-doping of nanotubes. The detailed multifrequency Raman spectroscopy investigation of the alteration of Raman modes of SWCNTs upon filling is conducted. The doping-induced changes in the radial breathing mode and G-band are revealed. It is found that these changes differ for the metallic and semiconducting SWCNTs. The obtained data and revealed trends are expected to be helpful for forthcoming studies to interpret the observed changes in Raman spectra of filled metallic and semiconducting SWCNTs.
关键词： Raman spectroscopy,electronic properties,X-ray photoelectron spectroscopy,rubidium iodide,filling,single-walled carbon nanotubes
更新于2025-09-11 14:15:04
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Global alignment of solution-based single-wall carbon nanotube films via machine-vision controlled filtration
摘要： Over the past decade, substantial progress has been made in the chemical control (chiral enrichment, length sorting, handedness selectivity, and filling substance) of single-wall carbon nanotubes (SWCNTs). Recently, it was shown that large, horizontally-aligned films can be created out of post-processed SWCNT solutions. Here, we use machine-vision automation and parallelization to simultaneously produce globally-aligned SWCNT films using pressure-driven filtration. Feedback control enables filtration to occur with a constant flow rate that not only improves the nematic ordering of the SWCNT films, but also provides the ability to align a wide range of SWCNT types and on a variety of nanoporous membranes using the same filtration parameters. Using polarized optical spectroscopic techniques, we show that under standard implementation, meniscus combing produces a two-dimensional radial SWCNT alignment on one side of the film. After we flatten the meniscus through silanation, spatially-resolved nematicity maps on both sides of the SWCNT film reveal global alignment across the entire structure. From experiments changing ionic strength and membrane charging, we provide evidence that the SWCNT alignment mechanism stems from an interplay of intertube interactions and ordered membrane charging. This work opens up the possibility of creating globally-aligned SWCNT film structures for a new-generation of nanotube electronics and optical control elements.
关键词： Nematic ordering,single-wall carbon nanotubes,directional charging,1D crystals
更新于2025-09-11 14:15:04
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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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Carbon nanotube: Controlled synthesis determines its future; 碳纳米管: 可控制备决定未来;
摘要： Carbon nanotubes (CNTs) have received broad attention in the past decades due to their excellent physical and chemical properties and thus been regarded as a powerful candidate for future star-materials. Although various CNT products and their related applications have been demonstrated recently, their performance can hardly meet the researchers’ expectations compared with their theoretical properties. The current predicament is caused by the immature synthesis method, including the basic science and the producing technology. As the synthesis with controlled structures determines its future, this review summarizes the progress on the basic research and industrialization of CNTs in the past decades, including the fine structure control, aggregation status design and scale-up production, and further points out the way for the future development of CNTs combining with specific applications.
关键词： applications,carbon nanotubes,scale-up synthesis,structure-controlled synthesis
更新于2025-09-11 14:15:04
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Carbon-nanotube computer scaled up
摘要： Electronic devices that are based on carbon nanotubes have the potential to be more energy efficient than their silicon counterparts, but have been restricted in functionality. This limitation has now been overcome. See Article p.595
关键词： microelectronic devices,silicon transistors,PMOS,CMOS technology,carbon nanotubes,NMOS
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Yb:KLuW Channel Waveguide Lasers Passively Q-Switched by Evanescent-Field Interaction with Carbon Nanotubes
摘要： Highly efficient and compact pulsed laser sources have tremendous potential for integrated photonic devices in numerous applications including spectroscopy, metrology and microscopy. Yb3+-doped monoclinic double-tungstate crystals exhibit broad and large absorption and emission cross-sections and extremely low quantum defects. Channel waveguide structures have been actively studied for miniaturization of laser systems and efficient fundamental-mode laser operation with low lasing thresholds. One of the powerful methods to fabricate waveguide structures in a transparent material is the femtosecond direct laser writing (fs-DLW). Recently, pulsed waveguide lasers utilizing saturable absorbers (SAs) have been demonstrated with SESAM and low-dimensional carbon nanostructures. [1-3] Intrinsic characteristics such as ultrafast response, broadband nonlinear absorption and flexibility for integration make single-walled carbon nanotubes (SWCNTs) and graphene unique for various types of pulsed lasers. Placing a SA between the waveguide and the laser mirror results in additional intracavity losses and Q-switching instabilities due to thermal loads through direct-field interaction with the SA. Therefore, the damage-free coupling and the potential of a monolithic design including SAs in compact lasers are highly desired. Here we demonstrate the first Q-switched operation of the Yb-doped channel waveguides based on evanescent-field interaction with SWCNTs and compare with a direct-field interaction scheme. A surface circular cladding waveguide with a vertical width of 50 μm is inscribed in the 5 at.% Yb3+-doped KLu(WO4)2 crystal by fs-DLW (employing 120-fs / 65-nJ / 1-kHz pulses at a wavelength of 795 nm). Arc-discharged SWCNTs are spin-coated on top of the Yb:KLuW waveguide or on output couplers. A 982-nm tapered amplifier diode is used as the pump source. The polarization and power of the pump beam are controlled by a polarizer and two λ/2 wave plates. The 2.88-mm-long laser cavity consists of the Yb:KLuW channel waveguide and two mirrors directly attached to both end facets of the waveguide for two interaction schemes with SWCNTs, as shown in Fig. 1(a).
关键词： Channel Waveguide Lasers,Q-switched,Yb:KLuW,Evanescent-field Interaction,Carbon Nanotubes
更新于2025-09-11 14:15:04
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Enhanced piezoresponse and nonlinear optical properties of fluorinated self-assembled peptide nanotubes
摘要： Self-assembled L,L-diphenylalanine (FF) nanostructures offer an attractive platform for photonics and nonlinear optics. The nonlinear optical (NLO) coefficients of FF nanotubes depend on the diameter of the tube [S. Khanra et al. Phys. Chem. Chem. Phys. 19(4), 3084–3093 (2017)]. To further enhance the NLO properties of FF, we search for structural modifications. Here, we report on the synthesis of fluorinated FF dipeptides by replacing one ortho-hydrogen atom in each of the phenyl groups of FF by a fluorine atom. Density-functional theoretical calculations yield insights into minimum energy conformers of fluorinated FF (Fl-FF). Fl-FF self-assembles akin to FF into micron-length tubes. The effects of fluorination are evaluated on the piezoelectric response and nonlinear optical properties. The piezoelectric d15 coefficient of Fl-FF is found to be more than 10 times higher than that of FF nanotubes, and the intensity of second harmonic generation (SHG) polarimetry from individual Fl-FF nanotubes is more than 20 times that of individual FF nanotubes. Furthermore, we obtain SHG images to compare the intensities of FF and Fl-FF tubes. This work demonstrates the potential of fluorine substitution in other self-assembled biomimetic peptides for enhancing nonlinear optical response and piezoelectricity.
关键词： piezoresponse,density-functional theory,nonlinear optical properties,fluorinated self-assembled peptide nanotubes,second harmonic generation
更新于2025-09-11 14:15:04