Search results for " Nanotubes"

Halloysite nanotubes as support for metal-based catalysts

2017

Halloysite nanotubes (HNTs) are clay minerals with a hollow nanotubular structure. There is growing interest in these nanomaterials, due to their biocompatibility, potential applications and availability. The surface chemistry of HNTs is versatile for the targeted chemical modification of the inner lumen and outer surface. Functionalized halloysite constitutes a valuable support for metal nanoparticles, promoting catalytic applications with tunable properties. The peculiar tubular shape of HNTs favors the dispersion and surface availability of the supported metal nanoparticles that are active in the catalytic path. Moreover, the presence of an empty lumen opens new perspectives for the prod…

One-step electrochemical synthesis and physico-chemical characterization of CdSe nanotubes

2013

Abstract Stoichiometric CdSe nanotubes (NTs) with a length of ∼700 nm have been successfully grown by one-step electrochemical technique into anodic alumina membranes. Cyclovoltammetric method has been performed using porous anodic alumina as template electrode and an electrochemical bath containing Cd 2+ ions and SeO 2 . The as-prepared NTs have been identified as face-centred-cubic CdSe by XRD, while micro-Raman analysis reveals the typical peaks of nanostructured CdSe. The stoichiometric deposition of CdSe NTs formation is suggested by EDX analysis, with an average atomic percentage of Cd:Se of ∼0.93. Photoelectrochemical measurements reveal that CdSe NTs are photoactive materials with d…

Mechanical properties of sol–gel derived SiO2 nanotubes

2014

The mechanical properties of thick-walled SiO2 nanotubes (NTs) prepared by a sol–gel method while using Ag nanowires (NWs) as templates were measured by using different methods. In situ scanning electron microscopy (SEM) cantilever beam bending tests were carried out by using a nanomanipulator equipped with a force sensor in order to investigate plasticity and flexural response of NTs. Nanoindentation and three point bending tests of NTs were performed by atomic force microscopy (AFM) under ambient conditions. Half-suspended and three-point bending tests were processed in the framework of linear elasticity theory. Finite element method simulations were used to extract Young’s modulus values…

Filling carbon nanotubes with magnetic particles

2013

Magnetic carbon nanotube composites were obtained by filling carbon nanotubes with paramagnetic iron oxide particles. Measurements indicate that these functionalized nanotubes are superparamagnetic at room temperature. Details about the production and characterization of these materials are described along with the experimental procedures employed. These magnetic carbon nanotubes have the potential to be used in a wide range of applications, in particular, the production of nanofluids, which can be controlled by appropriate magnetic fields.

Effects of Bending on Raman-active Vibration Modes of Carbon Nanotubes

2008

We investigate vibration modes and their Raman activity of single-walled carbon nanotubes that are bent within their intrinsic elastic limits. By implementing novel boundary conditions for density-functional based tight-binding, and using non-resonant bond polarization theory, we discover that Raman activity can be induced by bending. Depending on the degree of bending, high-energy Raman peaks change their positions and intensities significantly. These effects can be explained by migration of nodes and antinodes along tube circumference. We discuss the challenge of associating the predicted spectral changes with experimental observations.

Electrical conductance of carbon nanotubes with misaligned ends

2013

During a manufacturing process, when a straight carbon nanotube is placed on a substrate, e.g., production of transistors, its two ends are often misaligned. In this study, we investigate the effects of multiwall carbon nanotubes’ (MWCNTs) outer diameter and chirality on the change in conductance due to misalignment of the two ends. The length of the studied MWCNTs was 120 nm, while the diameters ranged between 4 and 7 nm. A mixed finite element-tight-binding approach was carefully designed to realize reduction in computational time by orders of magnitude in calculating the deformation-induced changes in the electrical transport properties of the nanotubes. Numerical results suggest that ar…

Hybrid catalysts for CO 2 conversion into cyclic carbonates

2019

The conversion of carbon dioxide into valuable chemicals such as cyclic carbonates is an appealing topic for the scientific community due to the possibility of valorizing waste into an inexpensive, available, nontoxic, and renewable carbon feedstock. In this regard, last-generation heterogeneous catalysts are of great interest owing to their high catalytic activity, robustness, and easy recovery and recycling. In the present review, recent advances on CO 2 cycloaddition to epoxide mediated by hybrid catalysts through organometallic or organo-catalytic species supported onto silica-, nanocarbon-, and metal-organic framework (MOF)-based heterogeneous materials, are highlighted and discussed.

Multifunctional Carrier Based on Halloysite/Laponite Hybrid Hydrogel for Kartogenin Delivery

2018

[Image: see text] A novel carrier system based on halloysite nanotubes (HNT), for the potential intraarticular delivery of kartogenin (KGN) by means laponite (Lap) hydrogel (HNT/KGN/Lap), is developed. The drug was first loaded into HNT, and the hybrid composite obtained was used as filler for laponite hydrogel. Both the filler and the hydrogel were thoroughly investigated by several techniques and the hydrogel morphology was imaged by transmission electron microscopy. Furthermore, the gelating ability of laponite in the presence of the filler and the rheological properties of the hybrid hydrogel were also investigated. The kinetic release of kartogenin from HNT and HNT/Lap hybrid hydrogel …

Bismuth-Catalyzed Growth of SnS2 Nanotubes and Their Stability

2009

Carbon nanotubes under electron irradiation: Stability of the tubes and their action as pipes for atom transport

2005

The production and migration of carbon interstitials in carbon nanotubes under electron irradiation is studied experimentally and theoretically. It is shown that the threshold for displacing carbon atoms and the defect production rate strongly depend on the diameter of the nanotubes. Multiwalled nanotubes shrink by a loss of atoms and by diffusion of interstitials through the inner hollow in the axial direction. Thus, experimental evidence is given that nanotubes can act as nanoscale pipes for the transport of atoms.