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[en] Concern over the health effects from the inhalation of carbon nanotubes (CNTs) has been building for some time, and adverse health effects found in animal studies include acute and chronic respiratory damage, cardiac inflammation, and cancer including mesothelioma, heretofore only associated with asbestos exposure. The strong animal evidence of toxicity requires that the occupational hygiene community develops strategies for reducing or eliminating worker exposures to CNTs; part of this strategy involves the setting of occupational exposure limits (OELs) for CNTs. A number of government agencies and private entities have established OELs for CNTs; some are mass-based, while others rely on number concentration. We review these various proposed standards and discuss the pros and cons of each approach. We recommend that specific action be taken, including intensified outreach to employers and employees concerning the potential adverse health effects from CNT inhalation, the development of more nuanced OELs that reflect the complex nature of CNT exposure, a broader discussion of these issues among all interested parties, and further research into important unanswered questions including optimum methods to evaluate CNT exposures. We conclude that current animal toxicity evidence suggests that strong action needs to be taken to minimize exposures to CNTs, and that any CNT OEL should be consistent with the need to minimize exposures.
[en] In this work, the role of optical wavelength on the photo induced strain in carbon nanotubes (CNT) is probed using a Fiber Bragg Grating (FBG), upon exposure to infrared (IR) (21 με mW"−"1) and visible (9 με mW"−"1) radiations. The strain sensitivity in CNT is monitored over a smaller range (10"−"3 to 10"−"9 ε) by exposing to a low optical power varying in the range 10"−"3 to 10"−"6 W. In addition, the wavelength dependent response and recovery periods of CNT under IR (τ_r_i_s_e = 150 ms, τ_f_a_l_l = 280 ms) and visible (τ_r_i_s_e = 1.07 s, τ_f_a_l_l = 1.18 s) radiations are evaluated in detail. This study can be further extended to measure the sensitivity of nano–scale photo induced strains in nano materials and opens avenues to control mechanical actuation using various optical wavelengths. (paper)
[en] We report thermally activated transport resonances for biases below the superconducting energy gap in a carbon nanotube quantum dot (QD) device with a superconducting Pb and a normal metal contact. These resonances are due to the superconductor's finite quasi-particle population at elevated temperatures and can only be observed when the QD life-time broadening is considerably smaller than the gap. This condition is fulfilled in our QD devices with optimized Pd/Pb/In multi-layer contacts, which result in reproducibly large and “clean” superconducting transport gaps with a strong conductance suppression for subgap biases. We show that these gaps close monotonically with increasing magnetic field and temperature. The accurate description of the subgap resonances by a simple resonant tunneling model illustrates the ideal characteristics of the reported Pb contacts and gives an alternative access to the tunnel coupling strengths in a QD.
[en] Nanocarbons represented especially by carbon nanotubes (CNTs) and graphene have been of great interest during the last two decades, both from a fundamental point of view and for future applications. The most eye-catching features of carbon nanostructures (CNSs) are their electronic, mechanical, optical and chemical characteristics, which open a way for versatile applications. Among those future prospects, actuators are one of the promising technologies. Since 1999 when the first macroscopic actuator containing CNTs was reported, the interest of utilizing these materials as well as other CNSs in active systems has been triggered all over the world. This paper gives a thorough review as well as in-depth descriptions of the many aspects of nanocarbon-based actuators. The review covers aspects of worldwide research and development of nanocarbon ionic actuators up to 2012. Materials which are covered by this review include CNTs and their composites, carbon nanofibres (CNFs), graphene and its derivatives, microporous carbon materials (for example carbide derived carbons (CDCs) and carbon aerogels) as well as the possible combinations of these materials. The considered aspects cover the following fields: synthesis and characterization of the investigated materials, the actuation mechanism as well as modelling and simulation. Applications comprising system integration and device development are also reviewed within this paper. (paper)
[en] The most important quantities referred to transport phenomena in nanostructures are well described by the Drude–Lorentz model and generalizations. I have presented a new “time-domain” Drude–Lorentz-like model for nano-transport and its quantum generalization; the model is general and offers good fitting using experimental data obtained from scientific literature. It allows interesting applications in the field of nanostructured materials, also in the biological and medical fields. I consider in this paper the elaboration of experimental data of SWCN; implemented data offer interesting details regarding the influence of temperature for velocity and diffusivity in transparent carbon nanotube films.
[en] Studies of materials consisting of carbon nanotubes or containing them have been analyzed and generalized. Classification of these materials is proposed, their general features and main types are considered, and individual examples are presented. The bibliography includes 372 references.
[en] Highlights: • This work adopts one- and two-step Hummers' method to prepare graphene nanosheets. • The thermal reduction narrows the band gap of graphene-based electrodes. • The photoluminescence (PL) is affected by the band gap of graphene quantum dots. • The blue-shift behavior primarily originated from surface functionalization. • This study offers a way to tune PL response, favoring optoelectronic application.
[en] Hollow fiber ultrafiltration membranes on the basis of polysulfone and multiwalled carbon nanotubes (MWCNT) have been obtained by phase inversion process. MWCNT were dispersed in N,N-dimethylacetamide by non-covalent modification method using polyvinylpyrrolidone, which is one of the component of the spinning solution. It has been shown that incorporation of MWCNT at low concentration has a significant effect on the structure and transport properties of the hollow fiber membranes. (authors)