6 research outputs found

    Ice-Assisted Transfer of Carbon Nanotube Arrays

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    Decoupling the growth and the application of nanomaterials by transfer is an important issue in nanotechnology. Here, we developed an efficient transfer technique for carbon nanotube (CNT) arrays by using ice as a binder to temporarily bond the CNT array and the target substrate. Ice makes it an ultraclean transfer because the evaporation of ice ensures that no contaminants are introduced. The transferred superaligned carbon nanotube (SACNT) arrays not only keep their original appearance and initial alignment but also inherit their spinnability, which is the most desirable feature. The transfer-then-spin strategy can be employed to fabricate patterned CNT arrays, which can act as 3-dimensional electrodes in CNT thermoacoustic chips. Besides, the flip-chipped CNTs are promising field electron emitters. Furthermore, the ice-assisted transfer technique provides a cost-effective solution for mass production of SACNTs, giving CNT technologies a competitive edge, and this method may inspire new ways to transfer other nanomaterials

    Observation of Charge Generation and Transfer during CVD Growth of Carbon Nanotubes

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    Carbon nanotube (CNT) is believed to be the most promising material for next generation IC industries with the prerequisite of chirality specific growth. For various approaches to controlling the chiral indices of CNTs, the key is to deepen the understanding of the catalytic growth mechanism in chemical vapor deposition (CVD). Here we show our discovery that the as-grown CNTs are all negatively charged after Fe-catalyzed CVD process. The extra electrons come from the charge generation and transfer during the growth of CNTs, which indicates that an electrochemical process happens in the surface reaction step. We then designed an in situ measurement equipment, verifying that the CVD growth of CNTs can be regarded as a primary battery system. Furthermore, we found that the variation of the Fermi level in Fe catalysts have a significant impact on the chirality of CNTs when different external electric fields are applied. These findings not only provide a new perspective on the growth of CNTs but also open up new possibilities for controlling the growth of CNTs by electrochemical methods

    Laser-Induced Flash-Evaporation Printing CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Thin Films for High-Performance Planar Solar Cells

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    Organic–inorganic hybrid perovskites have been emerging as promising light-harvesting materials for high-efficiency solar cells recently. Compared to solution-based methods, vapor-based deposition technologies are more suitable in preparing compact, uniform, and large-scale perovskite thin films. Here, we utilized flash-evaporation printing (FEP), a laser-induced ultrafast single source evaporation method employing a carbon nanotube evaporator, to fabricate high-quality methylammonium lead iodide perovskite thin films. Stoichiometric films with pure tetragonal perovskite phase can be achieved using a controlled methylammonium iodide to lead iodide ratio in evaporation precursors. The film crystallinity and crystal grain growth could further be promoted after postannealing. Planar solar cells (0.06 cm<sup>2</sup>) employing these perovskite films exhibit a champion power conversion efficiency (PCE) of 16.8% with insignificant hysteresis, which is among the highest reported PCEs using vapor-based deposition methods. Large-area (1 cm<sup>2</sup>) devices based on such perovskite films also achieved a stabilized PCE of 11.2%, indicating the feasibility and scalability of our FEP method in fabricating large-area perovskite films for other optoelectronic applications

    New Approach to Low-Power-Consumption, High-Performance Photodetectors Enabled by Nanowire Source-Gated Transistors

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    Power consumption makes next-generation large-scale photodetection challenging. In this work, the source-gated transistor (SGT) is adopted first as a photodetector, demonstrating the expected low power consumption and high photodetection performance. The SGT is constructed by the functional sulfur-rich shelled GeS nanowire (NW) and low-function metal, displaying a low saturated voltage of 0.61 V ± 0.29 V and an extremely low power consumption of 7.06 pW. When the as-constructed NW SGT is used as a photodetector, the maximum value of the power consumption is as low as 11.96 nW, which is far below that of the reported phototransistors working in the saturated region. Furthermore, benefiting from the adopted SGT device, the photodetector shows a high photovoltage of 6.6 × 10–1 V, a responsivity of 7.86 × 1012 V W–1, and a detectivity of 5.87 × 1013 Jones. Obviously, the low power consumption and excellent responsivity and detectivity enabled by NW SGT promise a new approach to next-generation, high-performance photodetection technology

    Vapor-Condensation-Assisted Optical Microscopy for Ultralong Carbon Nanotubes and Other Nanostructures

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    Here we present a simple yet powerful approach for the imaging of nanostructures under an optical microscope with the help of vapor condensation on their surfaces. Supersaturated water vapor will first form a nanometer-sized water droplet on the condensation nuclei on the surface of nanostructures, and then the water droplet will grow bigger and scatter more light to make the outline of the nanostructure be visible under dark-field optical microscope. This vapor-condensation-assisted (VCA) optical microscopy is applicable to a variety of nanostructures from ultralong carbon nanotubes to functional groups, generating images with contrast coming from the difference in density of the condensation sites, and does not induce any impurities to the specimens. Moreover, this low-cost and efficient technique can be conveniently integrated with other facilities, such as Raman spectroscope and so forth, which will pave the way for widespread applications

    Epitaxial Growth of Aligned and Continuous Carbon Nanofibers from Carbon Nanotubes

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    Exploiting the superior properties of nanomaterials at macroscopic scale is a key issue of nanoscience. Different from the integration strategy, “additive synthesis” of macroscopic structures from nanomaterial templates may be a promising choice. In this paper, we report the epitaxial growth of aligned, continuous, and catalyst-free carbon nanofiber thin films from carbon nanotube films. The fabrication process includes thickening of continuous carbon nanotube films by gas-phase pyrolytic carbon deposition and further graphitization of the carbon layer by high-temperature treatment. As-fabricated nanofibers in the film have an “annual ring” cross-section, with a carbon nanotube core and a graphitic periphery, indicating the templated growth mechanism. The absence of a distinct interface between the carbon nanotube template and the graphitic periphery further implies the epitaxial growth mechanism of the fiber. The mechanically robust thin film with tunable fiber diameters from tens of nanometers to several micrometers possesses low density, high electrical conductivity, and high thermal conductivity. Further extension of this fabrication method to enhance carbon nanotube yarns is also demonstrated, resulting in yarns with ∌4-fold increased tensile strength and ∌10-fold increased Young’s modulus. The aligned and continuous features of the films together with their outstanding physical and chemical properties would certainly promote the large-scale applications of carbon nanofibers
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