Laboratorní trať pro měření solárních zařízení

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta strojní. Katedra (361) energetik

High-Yield Synthesis and Optical Properties of Carbon Nanotube Porins

Carbon nanotube porins (CNTPs) are a convenient membrane-based model system for studying nanofluidic transport that replicates a number of key structural features of biological membrane channels. We present a generalized approach for CNTP synthesis using sonochemistry-assisted segmenting of carbon nanotubes. Prolonged tip sonication in the presence of lipid molecules debundles and fragments long carbon nanotube aggregates into stable and water-soluble individual CNTPs with lengths in the range 5–20 nm. We discuss the main parameters that determine the efficiency and the yield of this process, describe the optimized conditions for high-yield CNTP synthesis, and demonstrate that this methodology can be adapted for synthesis of CNTPs of different diameters. We also present the optical properties of CNTPs and show that a combination of Raman and UV–vis–NIR spectroscopy can be used to monitor the quality of the CNTP synthesis. Overall, CNTPs represent a versatile nanopore building block for creating higher-order functional biomimetic materials

Laser-Assisted Simultaneous Transfer and Patterning of Vertically Aligned Carbon Nanotube Arrays on Polymer Substrates for Flexible Devices

We demonstrate a laser-assisted dry transfer technique for assembling patterns of vertically aligned carbon nanotube arrays on a flexible polymeric substrate. A laser beam is applied to the interface of a nanotube array and a polycarbonate sheet in contact with one another. The absorbed laser heat promotes nanotube adhesion to the polymer in the irradiated regions and enables selective pattern transfer. A combination of the thermal transfer mechanism with rapid direct writing capability of focused laser beam irradiation allows us to achieve simultaneous material transfer and direct micropatterning in a single processing step. Furthermore, we demonstrate that malleability of the nanotube arrays transferred onto a flexible substrate enables post-transfer tailoring of electric conductance by collapsing the aligned nanotubes in different directions. This work suggests that the laser-assisted transfer technique provides an efficient route to using vertically aligned nanotubes as conductive elements in flexible device applications

Water-Assisted Growth of Uniform 100 mm Diameter SWCNT Arrays

We report a simple method for growing high-quality single-walled carbon nanotube (SWCNT) arrays on 100 mm wafers via the addition of water vapor to highly purified gases during the CNT growth step. We show that adding a small amount of water during growth helps to create a uniform catalyst distribution and yields high-quality (Raman G/D of 26 ± 3), high-density (up to 6 × 10¹¹ cm^–2) and uniform SWCNT arrays on 100 mm large wafers. We rationalize our finding by suggesting that the addition of water decreases catalyst mobility, preventing its coarsening at higher temperatures. We also report a new mechanism of catalyst inactivation in wafer-scale growth using ultrapurified gas sources by the formation of large, 5 ± 3 μm iron particles. We found such formations to be common for substrates with large temperature gradients, such as for wafers processed in a typical cold-wall chemical vapor deposition reactor

Additional file 1: of Effect of Enhanced Thermal Stability of Alumina Support Layer on Growth of Vertically Aligned Single-Walled Carbon Nanotubes and Their Application in Nanofiltration Membranes

Figure S1. AFM on an unstable alumina film annealed at 750 °C. Figure S2. Al 2p XPS spectra of the unstable and the stable alumina films. Figure S3. Diameter distribution of the catalyst particles after annealing extracted from AFM image analysis (bars). Top: unstable alumina films; Bottom: stable alumina films. Overlapping dashed curves represent the corresponding SWCNT diameter distribution measured by TEM. Table S1. Typical methods used in the literature to verify that transport occurs through CNTs rather than through defects in the matrix. NP = nanoparticle; P gas  = gas permeance. (DOCX 459 kb

Osmotically-Driven Transport in Carbon Nanotube Porins

We report the measurements of transport of ions and uncharged species through carbon nanotube (CNT) porinsshort segments of CNTs inserted into a lipid bilayer membrane. Rejection characteristics of the CNT porins are governed by size exclusion for the uncharged species. In contrast, rejection of ionic species is governed by the electrostatic repulsion and Donnan membrane equilibrium. Permeability of monovalent cations follows the general trend in the hydrated ion size, except in the case of Cs⁺ ions