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History and National Initiatives of Carbon Nanotube and Graphene Research in Brazil
摘要： In this article, we first introduce and discuss the fundamental science of carbon nanomaterials (especially nanotubes and graphene) and the different technological applications from using these materials. We then discuss the first works of Brazilians scientists, done in collaboration with scientists of other countries and, in particular, the role of Prof. M. S. Dresselhaus from MIT, US, in the development of the nanocarbon science in Brazil. We briefly discuss some experimental and theoretical works about nanotubes and graphene done in Brazil in the late 1990s and early 2000s, and the formation of the first Brazilian network on carbon nanotubes in 2005. We present the activities of the National Institute of Science and Technology (INCT) in Carbon Nanomaterials (CN) created in 2009. A scientometric analysis is used to describe the INCT-CN network formation. Finally, we present the Center of Technology in Nanomaterials (CTNano) installed at UFMG, where pilot plants were developed to produce graphene and nanotubes at large scales, and the work being done at the center in collaboration with companies aiming to solve specific technological problems and to create bridges between the academic and the industrial sectors.
关键词： Graphene,Scientometric Analysis,Nanotechnology,Carbon nanotubes
更新于2025-09-23 15:22:29
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Double-layer Electromagnetic Wave Absorber Based on Carbon Nanotubes Doped with La(NO3)3 and Fe3O4 Nanoparticles
摘要： Double-layer structure absorbing materials based on the impedance matching principle and transmission line theory can effectively improve the electromagnetic wave absorbing properties. In this paper, the electromagnetic wave absorbing properties of double-layer absorbers (MWCNT)-La(NO3)3/polyvinyl chloride (PVC) and MWCNT-Fe3O4/PVC composites had been taken turns as the absorption layer and matching layer, were investigated in 2 – 18 GHz range. The absorbing properties of single- and double-layer structure and different each-layer thickness with two types of combinations were compared. The results showed that the design of double-layer structure for composites could effectively broaden the absorption frequency area, and increase the absorption intensity. When MWCNT-La(NO3)3/PVC composite were used as absorption layers with 0.6 mm thickness, the absorption bandwidth (< – 15 dB or > 97 %) of double-layer composite was the widest, reaching a maximum of about 3.36 GHz, and the absorption peak value was also the lowest about – 46.02 dB at 16.24 GHz.
关键词： La(NO3)3,multiwall carbon nanotubes,Fe3O4,electromagnetic wave absorbing properties
更新于2025-09-23 15:22:29
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Raman Spectroscopy || Graphene Nanocomposites Studied by Raman Spectroscopy
摘要： The goal of this chapter is to provide a general introduction about graphene nanocomposites studied by Raman spectroscopy. The chapter will therefore begin with a brief description of the major Raman bands of carbon allotropes. In the following chapter a concise comparison between single walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), fullerenes and graphene is exposed. The characteristic features in Raman spectra of carbon allotropes, namely the intense signals D and G are investigated. In particular, the chapter will outline the Raman spectrum of graphene and different types of graphene oxide. The last part of the chapter is devoted to graphene nanocomposites.
关键词： carbon nanotubes,graphene Raman bands,graphene oxide,polymeric nanocomposites,carbon allotropes
更新于2025-09-23 15:22:29
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Highly Stretchable Carbon Nanotube Fibers with Tunable and Stable Light Emission
摘要： Carbon nanotubes (CNTs) possess intriguing photoluminescence properties, and CNT fibers emit strong incandescent light thus act as macroscopic light sources. So far, straight-shaped CNT fibers are a focus of study and their emission properties are elucidated. Here, the authors show that helical-shaped single-walled carbon nanotube (SWNT) fibers produce uniform and stable incandescent light along the entire fiber under moderate voltages, and the emission intensity is tailored over a wide range by the applied voltage and the elongation of the fiber (up to 70% strain), and in a reversible way during mechanical deformation. Their highly stretchable SWNT fibers with tunable light emission have promising applications in emerging research areas such as wearable electronics and high-performance optoelectronic fiber systems.
关键词： single-wall carbon nanotubes,stretchable device,helical fiber,light emission
更新于2025-09-23 15:22:29
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Enhanced photocatalytic activity of hierarchical titanium dioxide microspheres with combining carbon nanotubes as “e-bridge”
摘要： Enhancing photocatalytic activity of titanium dioxide (TiO2) by efficient charge separation is essential but challenging. Herein, the recombination between photo-generated e–-h+ pairs is effectively hindered owing to the “e-bridge” formed between hierarchical TiO2 microspheres and carbon nanotubes (CNTs). The as-prepared three-dimensional TiO2 microspheres covered by intercrossing lamellar crystals are abundant in pores and sharp edges, forming an ideal interface with large surface area and numerous active sites for photocatalysis. Combined with CNTs, the TiO2 microspheres are connected and stabilized. Moreover, the CNTs serve as pathways for electrons, benefiting the effective separation of e–-h+ pairs and accounting for the superior photocatalytic activity. Transient fluorescence spectra shows that the lifetime of electrons on TiO2 prolongs from 5.23 ns to 10.14 ns assisted by CNTs. In aqueous matrix, electrons gathering on the CNTs can react with O2 to produce O2–, and simultaneously, plenty of holes left in TiO2 host generate OH by oxidizing adsorbed H2O, producing abundant active species for photocatalytic degradation of 4-nitrophenol. The highest degradation efficiency in removing organic contaminants is achieved on TiO2@CNTs hybridized with CNTs weight ratio being 5%.
关键词： e-Bridge,Titanium dioxide,Carbon nanotubes,Organic pollutant,Photocatalytic degradation
更新于2025-09-23 15:22:29
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Photocatalytic and Filtration performance study of TiO2/CNTs-Filter for oil particle
摘要： Carbon nanotubes (CNTs) with large aspect ratio and specific surface area have the potential in oil liquid particle filtration and catalysis substrate field. In this work, we synthesized the TiO2/CNTs-filter for removing oil particle. Compared with the CNTs-filter, we found that the TiO2/CNTs-filter has smaller pore sizes, higher specific area. TiO2/CNTs-filter shows the excellent filtration performance which is higher than the high efficiency particulate air (HEPA) filter. In addition, the initial pressure drop of TiO2/CNTs-filter is close to conventional HEPA filter and the raise ratio of pressures drop at equilibrium states is less than conventional HEPA filter. Furthermore, the degradation rate of initial state and saturation state reach to 94.5 and 724 μg cm-2 h-1 in first 20 h respectively. At last, we simply discuss the application the composite filter on filtering cooking fume.
关键词： carbon nanotubes,filtration,composite filter,oil particle,photocatalytic
更新于2025-09-23 15:22:29
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Layer by layer deposition of alternate carbon nanotubes and Ni films for efficient multilayer thin film temperature gauges
摘要： This study reports a novel approach for growing multilayer thin films consisting of alternate layers of carbon nanotubes (CNT) and nickel on Si (1 0 0) substrates and justifies their use in thin film temperature sensors. A low pressure chemical vapor deposition system was employed for synthesizing CNT films, while Ni films were deposited by electrodeposition. Porous-Si was used as substrate to increase adhesion between the layers of the multilayer structure. The structure of the multilayer films and the quality of the CNT grown were analyzed using several characterization methods, including scanning electron microscopy, x-ray photoelectron spectroscopy, x-ray auger electron spectroscopy and Raman spectroscopy. The electrical characteristics were investigated using a van der Pauw setup and the effect of the increasing number of CNT layers in the multilayer structure was studied. The sensitivity of the multilayer film was found to increase with increasing number of CNT layers, despite the decrease of the temperature coefficient of resistance. On the other hand, the initial resistance was found to increase. Results indicated that these multilayer structures are appropriate for fabricating highly sensitive thin film gauges that can detect lower heat fluxes with more accuracy.
关键词： carbon nanotubes,thin film gauges,surface and interface chemistry,porous silicon,adhesion sensing,x-ray photoelectron spectroscopy
更新于2025-09-23 15:22:29
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Growth orientation Mechanism of TiO<sub>2</sub> Nanotubes Fabricated by Anodization
摘要： TiO2 nanotube fabricated by anodization has been extensively researched in the past decades. However, the mechanism that controls the growth orientation of anodic TiO2 nanotube is still not clear. Here we firstly dig into their growth orientation systematically. Combining with previous literatures, the results of anodization on rotated Ti foil and thin Ti wire confirm that almost all of the TiO2 nanotubes grow vertically to the local Ti substrate surface. Their growth orientation predominantly depends on the local electric field around the nanotube bottom. The distribution of local electric field is regulated by the shape of initial nano-scale local Ti substrate surface. Mostly, the initial nano-scale local Ti substrate surface is nearly flat, which leaves vertical, circle and straight TiO2 nanotubes. In terms of evolution of TiO2 nanotubes fabricated on micron-scale convex surface, the vertical growth of TiO2 nanotubes leads to a continuous decrease in the oxide/substrate interface area, and a few TiO2 nanotubes are crushed and detached periodically from oxide/substrate interface. For micron-scale concave surface, due to the ever-increasing of oxide/substrate interface area, Y-branched TiO2 nanotubes occurred periodically as a response to avoid the vacancy on oxide/substrate interface.
关键词： growth orientation,anodic TiO2 nanotubes,concave surface,convex surface
更新于2025-09-23 15:22:29
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Direct observation of cross-polarized excitons in aligned single-chirality single-wall carbon nanotubes
摘要： Optical properties of single-wall carbon nanotubes (SWCNTs) for light polarized parallel to the nanotube axis have been studied extensively, whereas their response to light polarized perpendicular to the nanotube axis has not been well explored. Here, by using a macroscopic film of highly aligned single-chirality (6,5) SWCNTs, we performed a systematic polarization-dependent optical absorption spectroscopy study. In addition to the commonly observed angular-momentum-conserving interband absorption of parallel-polarized light, which generates E11 and E22 excitons, we observed a small but unambiguous absorption peak whose intensity is maximum for perpendicular-polarized light. We attribute this feature to the lowest-energy cross-polarized interband absorption processes that change the angular momentum along the nanotube axis by ±1, generating E12 and E21 excitons. Unlike previous observations of cross-polarized excitons in polarization-dependent photoluminescence and circular dichroism spectroscopy experiments, our direct observation using absorption spectroscopy allowed us to quantitatively analyze this resonance. Specifically, we determined the energy and oscillator strength of this resonance to be 1.54 and 0.05, respectively, compared with the values for the E11 exciton peak. These values, in combination with a comparison with theoretical calculations, in turn led to an assessment of the environmental effect on the strength of Coulomb interactions in this aligned single-chirality SWCNT film.
关键词： polarization-dependent,single-wall carbon nanotubes,cross-polarized excitons,aligned film,optical absorption spectroscopy,Coulomb interactions
更新于2025-09-23 15:22:29
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[IEEE 2018 International Semiconductor Conference (CAS) - Sinaia, Romania (2018.10.10-2018.10.12)] 2018 International Semiconductor Conference (CAS) - Carbon Nanotube/Polyaniline Composite Films Prepared by Hydrothermal- Electrochemical Method for Biosensor Applications
摘要： In this study, CNT-PANI composites were prepared in soft chemical synthesis conditions using hydrothermal method. Our aim is to obtain CNT-PANI films with potential applications in VOC’s detection, using an environmental friendly, low energy consumption technique: hydrothermal-electrochemical deposition of composite films. Thin films were characterized by AFM and FT-IR analyses.
关键词： carbon nanotubes,poly(aniline),composites,biosensor,electrochemical
更新于2025-09-23 15:22:29