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Photocatalyst properties depend on the mix
摘要： Photocatalysts use light to power chemical reactions in a whole host of applications from fuel cells to water remediation. There are many ways to improve the performance of titania (TiO2) photocatalysts from using catalyst support materials, which increase photosensitization rates, and help break down organic pollutants, to doping or co-doping with other atoms to expand the absorption range. Since using metal atoms such as dopants is problematic for water treatment if they leach into the environment, non-metallic dopants like nitrogen (N) are considered safer. Researchers from the University of South Africa have used these two strategies in conjunction to produce N-doped TiO2 photocatalysts on a carbon nanotube (CNT) support and systematically compared the effects of using different synthesis routes. Edward N. Nxumalo and his team find that photocatalysts with distinctly different properties and performance are produced depending on whether a hydrothermal or solgel synthetic route is used.
关键词： Carbon nanotubes,Hydrothermal synthesis,Solgel synthesis,Nitrogen doping,Photocatalysts,TiO2
更新于2025-09-11 14:15:04
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Synthesis of nanosized SiC by low-temperature magnesiothermal reduction of nanocomposites of functionalized carbon nanotubes with MCM-48
摘要： Silicon carbide synthesis by a magnesiothermal method was investigated using MCM-48 as the silica source mechanically mixed with carbon nanotubes (CNTs) as the carbon source, and nanocomposites of MCM-48/functionalized CNTs (CNTF). SiC syntheses were carried out with different molar ratios of MCM-48, carbon and magnesium at 700?C in argon. The MCM-48 and carbon nanotube starting materials and the SiC products were characterized by BET, XRD, FESEM, EDX and TEM. The effect of the carbon content and the type of CNTs (either functionalized or unfunctionalized) on the SiC synthesis was studied. The results show that an improved yield of SiC is obtained when the carbon nanotubes are functionalized, producing a better contact with the MCM-48. This improved contact between the reactants ensures a good degree of reaction in a stoichiometric mixture of silicon and carbon, with no improvement in product formation being achieved by the use of additional carbon. These findings suggest that the degree of contact between reactants is an important factor in the magnesiothermal synthesis of SiC. The SiC products from magnesiothermal synthesis of the functionalized nanocomposite precursors were shown by TEM and FESEM to have unusual nanofiber morphologies mimicking the morphology of the CNTF nanotubes.
关键词： MCM-48,Silicon carbide,Magnesiothermal synthesis,Carbon nanotubes,Functionalized carbon nanotubes
更新于2025-09-10 09:29:36
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One step to prepare CNTs modified porous g-C3N4 with excellent visible-light photocatalytic performance
摘要： A kind of carbon nanotubes (CNTs) modified porous graphitic carbon nitride (CNTs/pg-C3N4) photocatalyst was successfully synthesized via one step thermal polycondensation and completely measured by some instruments, such as XRD, FTIR, TEM, BET, DRS, PL, etc. And the relevant experimental data indicated that loaded CNTs could be beneficial to the photoinduced charges transfer, facilitating photoinduced charge separation rate. Meanwhile, surface area and visible light adsorption of CNTs/pg-C3N4 photocatalyst could be increased and improved. These synergetic effects resulted in the as-synthesized CNTs/pg-C3N4 photocatalyst exhibiting better visible-light-induced photocatalytic performance for organic pollutant degradation and the product of clean energy than bulk g-C3N4, pg-C3N4 and CNTs modified bulk g-C3N4, and excellent stable photocatalytic performance was also observed after several recycling experiments. Finally, a reasonable improved photocatalytic reaction mechanism for CNTs/pg-C3N4 photocatalyst is presented.
关键词： Porous graphitic carbon nitride,Photocatalytic performance,Carbon nanotubes,Photocatalyst,Visible-light
更新于2025-09-10 09:29:36
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Advantages of the Surface Structuration of KBr Materials for Spectrometry and Sensors
摘要： A potassium bromide (KBr) material, which has been widely used as the key element in Fourier spectrometers and as the output window of the IR-lasers, was studied via applying carbon nanotubes in order to modify the potassium bromide surface. The laser-oriented deposition method was used to place the carbon nanotubes at the matrix material surface in the vertical position at different electric ?elds varying from 100 to 600 V × cm?1. The main idea of the improvement of the spectral properties of the potassium bromide structure is connected with the fact that the refractive index of the carbon nanotubes is substantially less than the refractive index of the studied material, and the small diameter of the carbon nanotubes allows one to embed these nano-objects in the voids of the lattice of the model matrix systems. Moreover, the mechanical characteristics and wetting features of potassium bromide structures have been investigated under the condition mentioned above. Analytical and quantum-chemical simulations have supported the experimental results.
关键词： surface structuration,potassium bromide,mechanical and wetting properties,laser-oriented deposition method,carbon nanotubes,spectra
更新于2025-09-10 09:29:36
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Complex band structure calculations based on the overbridging boundary matching method without using Green's functions
摘要： A complex band structure describes the dispersion relation not only of propagating bulk states but also of evanescent ones, both of which are together referred to as generalized Bloch states and are important for understanding the electronic nature of solid surfaces and interfaces. On the basis of the real-space finite-difference formalism within the framework of the density functional theory, we formulate the Kohn-Sham equation for generalized Bloch wave functions as a generalized eigenvalue problem without using any Green’s function matrix. By exploiting the sparseness of the coefficient matrices and using the Sakurai-Sugiura projection method, we efficiently solve the derived eigenvalue problem for the propagating and slowly decaying/growing evanescent waves, which are essential for describing the physics of surface/interface states. The accuracy of the generalized Bloch states and the computational efficiency of the present method in solving the eigenvalue problem obtained are compared with those by other methods using the Green’s function matrix. In addition, we propose two computational techniques to be combined with the Sakurai-Sugiura projection method and achieve further improvement in the accuracy and efficiency. Complex band structures are calculated with the present method for single- and multiwall carbon nanotubes, and the interwall hybridization and branch points of evanescent electronic states observed in the imaginary parts of the band structures are also discussed.
关键词： Sakurai-Sugiura projection method,density functional theory,generalized Bloch states,carbon nanotubes,complex band structure
更新于2025-09-10 09:29:36
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Effect of CuS nanocrystalline particles on counter electrodes of multi-wall carbon nanotubes for QDSCs
摘要： CuS nanocrystalline particles are deposited into the acid-treated multi-wall carbon nanotubes (MWCNTs) film on the fluorine-doped tin oxide glass substrate through the successive ionic layer adsorption and reaction combined with spin-coating technology to form MWCNTs/CuS composite counter electrode (CE). The CuS adding amount is changed in different cycles to discuss its effect mechanism on the photoelectric properties of MWCNTs/CuS composite CE based quantum dot sensitized solar cells (QDSCs). The TiO2 photoanodes are prepared by the electrospinning technique with CdS and ZnS as co-sensitizer. QDSCs are assembled with photoanodes, the polysulfide electrolyte and abovementioned CEs. The CEs are characterized by X-ray diffraction, transmission electron microscope and energy dispersed X-ray detector, which verifies CuS nanocrystalline particles are attached to MWCNTs successfully. The photoelectric properties are analyzed by Nyquist, Tafel and J–V curves. The results show that the introduction of CuS nanocrystalline particles can promote reduction rate of polysulfide species and the short circuit current density (Jsc) to improve catalytic activity, leading to a higher power conversion efficiency (PCE). The MWCNTs based CE with deposition CuS in eight cycles exhibits the best photoelectric performance within all CE samples and the electrical conductivity of MWCNTs/8CuS CE is superior to that of Pt CE according to Nyquist and Tafel curve analysis. PCE of QDSCs with MWCNTs/8CuS CE is up to 5.186%, which is a little lower than that of Pt CE (5.250%), but it possesses a higher Jsc value (18.028?mA cm?2) than that of Pt CE (16.057?mA cm?2). The low-cost MWCNTs/CuS composite CE with simple preparation is more suitable than Pt CE for commercial application of QDSCs.
关键词： multi-wall carbon nanotubes,quantum dot sensitized solar cells,CuS nanocrystalline particles,photoelectric properties,counter electrode
更新于2025-09-10 09:29:36
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Light and flexible composite nanofibrous membranes for high-efficiency electromagnetic absorption in a broad frequency
摘要： With the fast advancement of up-to-date communication technologies, electromagnetic wave (EMW) absorption materials are widely required for various applications. However, it is still a big challenge to produce lightweight, flexible and high efficiency EMW absorption materials in a broad-ranging frequency. Herein, we designed to fabricate the magnetic and dielectric nanofibrous membranes which can be effectively used as EMW absorption materials by facile electrospinning process. The as-fabricated composite carbon nanofibers (CNFs), which combined the components of nickel, cobalt antioxidant nanoparticles and carbon nanotubes, exhibited outstanding magnetic, dielectric properties and strong absorption ability in a wide frequency range. These nanoparticles encapsulated in CNFs are extremely beneficial to the electrical conductivity of the composites through decreasing the contact loss within the CNFs by formation the metal-metal interfaces. Correspondingly, the RL value of -46.60 dB was reached at 4.88 GHz frequency range with a layer thickness of 5.5 mm for these mechanically light and flexible membranes. The enhanced absorption performance (<?10 dB) in the wide frequency band (4.16-18 GHz) can be achieved by selecting a suitable thickness of the material. Results demonstrate that the permittivity and permeability of developed samples have been largely improved due to the integrated interaction of all introduced components in the structure. The composite membranes are a promising candidate for scalable, lightweight and high performance EMW absorption materials in the frequency range from C band to Ku band (4?18 GHz).
关键词： Magnetic and dielectric properties,permeability,permittivity,carbon nanotubes,electromagnetic wave absorption
更新于2025-09-10 09:29:36
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Facile Synthesis of Carbon Nanotubes Covalently Modified with ZnO Nanorods for Enhanced Photodecomposition of Dyes
摘要： Utilizing a one-pot solvothermal procedure novel one-dimensional zinc oxide-carbon nanotube nanohybrids (ZnCT) were synthesized in alcohol-alkali solution, free of catalytic assistance. The ZnCT hybrids were prepared through covalent modification of zinc oxide nanorods (ZnO NRs) with functionalized carbon nanotubes (f-CNTs). The morphology and microstructure of as-prepared ZnCT hybrids were characterized by scanning electron microscopy (SEM), powder X-ray diffraction, Raman, X-ray photoelectron and UV-vis absorption spectroscopies. SEM images of the ZnCT hybrids indicated that the ZnOethanol NRs grew longer along the vertical radial (0001) surface and aggregated to a lesser extent than the analogous ZnOmethanol NRs. Photodegradation analysis showed that the off-white ZnCTethanol hybrid with ascendant UV-visible light absorption had displayed superior photocatalytic activity towards Rhodamine B (RhB) dyes than either pure ZnOethanol, ZnOmethanol NRs or ZnCTmethanol hybrid, among which the photocatalytic activity of ZnOethanol NRs was better than that of ZnOmethanol NRs. Raman and X-ray photoelectron spectroscopy analyses confirmed a strong interaction between f-CNTs and ZnOethanol NRs in ZnCTethanol hybrid, in which Zn ions were chemically bonded to negatively charged oxygen-containing groups at the graphene-like surface of f-CNTs. The enhanced separation lifetime of the photogenerated electron-hole observed by surface photovoltage and photocurrent measurements of the ZnCTethanol hybrid was attributed to the efficient covalent linking of Zn-O-C and close contact configuration between the f-CNTs and ZnOethanol NRs. Further controlled photodegradation and electron spin resonance (ESR) analyses revealed that the photodegradation of RhB dyes resulted from photogenerated holes, and radical species, such as ?O2?、?OH?, which were formed in-situ. Details of the photocatalytic mechanism were also explored herein.
关键词： Solvothermal synthesis,ZnO nanorods,Carbon nanotubes,Dyes,Photodegradation
更新于2025-09-10 09:29:36
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Preparation and characterization of poly (3-hexylthiophene) / carbon nanotubes hybrid material via in-situ click chemistry
摘要： The poly(3-hexylthiophene) - multiwalled carbon nanotube hybrid material (P3HT-MWCNT) was successfully prepared in the Cu(I) / DBU catalyst system via in-situ click reaction. The properties of P3HT-MWCNT were measured by FTIR, 1H-NMR, UV-vis, XRD, TEM, SEM and AFM. The fluorescence spectrum of P3HT-MWCNT proved the covalent bond between P3HT and MWCNT, and P3HT could be coated on the surface of MWCNT. Compared with the physical blends of P3HT and MWCNT, P3HT-MWCNT prepared by click chemistry exhibited better thermal stability and a higher melting point of 243.2 oC. TG results also indicated that P3HT content of P3HT-MWCNT was 21.4%. It was expected to prepare novel organic-inorganic donor-acceptor hybrid material with good solubility, optical and thermal stability, which may be a promising material applied in preparation of organic photoelectron in the future.
关键词： multiwalled carbon nanotubes,chemical modification,poly(3-hexylthiophene),organic-inorganic hybrid material,Click chemistry
更新于2025-09-10 09:29:36
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Improvement of the third order nonlinear optical properties of nematic liquid crystal under the influence of different compositional percentage of doped SWCNT and the external electric field
摘要： In this research, the nematic liquid crystal (NLC) was doped with varying concentration (0-1 % wt.) of single walled carbon nanotubes (SWCNTs) at room temperature to study the nonlinear optical (NLO) properties of E5CN7@CNT cell.The third order NLO properties such as the nonlinear susceptibility, the nonlinear refraction (NLR) and the nonlinear absorption (NLA) were determined by using Z-scan techniques. The nonlinear studies have been done using a continuous wave (CW) He: Ne laser at 632.8 nm.Doping SWCNTs to eutectic uniaxial NLC (E5CN7) enhanced the third order nonlinear susceptibility, ??(3) and consequently the nonlinearity properties of composite systems improved.It is found that at lower concentration of CNTs (c< 0.75 % wt.), the third order nonlinear susceptibility are increased, but for concentration 0. 5<c<1 % wt., the third order nonlinear susceptibility are decreased. The negative sign of the observed NLR index, indicates that the E5CN7@CNT exhibits self-defocusing type optical nonlinearity. The two photon absorption (TPA) behavior, corresponding to negative sign NLA of samples. The reorientation of samples molecules amplifies upon the application of electric field, then nonlinearity increases.
关键词： Composite materials,Nematic liquid crystal,Carbon nanotubes,Third order nonlinear susceptibility,Nonlinear optics,Electric field,Z-scan method
更新于2025-09-10 09:29:36