Search results for " Nanotube"
showing 10 items of 560 documents
Chirality-controlled preparation and single molecule characterisation of carbon nanotubes
2011
Nanostructures have gained increasing attention not only for their basic scientific richness, but also because they promise novelties and potentials that may lead to technological revolution. Carbon nanotubes (CNT’s) are one of the primary focuses of nanotechnology because of their unique physical properties such as huge Young modulus, high tensile strength, thermal and electrical conductivity. However many of their physical properties are extremely sensitive to their atomic structure. In order to optimize utilization of CNTs, their fundamental material properties should be well understood. A single shell of a CNT is composed of a wrapped up sheet of graphite. Depending on the wrapping, sin…
Synthèses optimisées et caractérisations avancées de nanotubes de titanate et de leurs fonctionnalisations : vers l'élaboration de nanovecteurs de mo…
2017
The aim of this PhD thesis is to develop new nanohybrids based on titanate nanotubes (TiONts) in order to use them as nanocarrier of a therapeutic molecule: a stilbene phenol, 4'-hydroxy-4-(3-aminopropoxy)-trans-stilbene (HAPtS), which is a transresveratrol derivative.TiONts are synthesized by a hydrothermal treatment from a precursor of rutile titanium dioxide. Two methods of hydrothermal synthesis have been studied (the static and dynamic ones): the second approach uses an original hydrothermal device which provides a vigorous mechanical stirring during the hydrothermal process with controllable stirring time par hour. A parametric study was carried out to evaluate the effect of reaction …
Multi-residue determination of organic micro-pollutants in river sediment by stir-disc solid phase extraction based on oxidized buckypaper
2020
This paper describes a procedure for the isolation of 20 organic micro-pollutants among pesticides, drugs, recreational drugs, flame retardants from river sediments. After a solid-liquid extraction with a methanol:water (50:50, v/v) solution, the supernatant was diluted with water and cleaned up by stir-disc solid-phase extraction (SPE). The disc was made of buckypaper, a self-supporting entangled assembly of carbon nanotubes, which was used as a highly porous, two-sided, sorbent membrane. In the preliminary activation step, the membrane was oxidised for 2-hours with nitric acid to extend its extraction capability also to more polar compounds. All extracts were analysed by ultra-high-perfor…
Halloysite nanotubes-carbon dots hybrids multifunctional nanocarrier with positive cell target ability as a potential non-viral vector for oral gene …
2019
Abstract Hypothesis The use of non-viral vectors for gene therapy is hindered by their lower transfection efficiency and their lacking of self-track ability. Experiments This study aims to investigate the biological properties of halloysite nanotubes-carbon dots hybrid and its potential use as non-viral vector for oral gene therapy. The morphology and the chemical composition of the halloysite hybrid were investigated by means of high angle annular dark field scanning TEM and electron energy loss spectroscopy techniques, respectively. The cytotoxicity and the antioxidant activity were investigated by standard methods (MTS, DPPH and H2O2, respectively) using human cervical cancer HeLa cells …
Combining Atomic Force Microscopy and Depth-Sensing Instruments for the Nanometer-Scale Mechanical Characterization of Soft Matter
2009
Complex materials exhibit a hierarchical structure where a gradient of features on nanometer scale is induced by the synthetic route eventually enhanced by the loading condition. The nanometer scale at which individual components arrange, determining their properties, is a current challenge of mechanical testing. In this work, a survey on nanoindentation is outlined based on the comparison of results obtained by Atomic Force Microscopy and Depth-Sensing Instruments and their combination. An Atomic Force Microscope equipped with a Force Transducer gives indeed the possibility to scan the sample surface in contact mode, thereby allowing one to choose a suitable position for the nanoindentatio…
A computational and experimental investigation of halloysite silicic surface modifications after alkaline treatment
2023
Density functional theory calculations were performed in order to investigate the formation of silanol groups on the outer surface of halloysite nanotubes, as possible products of the reactions with water in alkaline environments. The results, discussed in terms of energy release and structural properties of the modified surface, suggest that the formation of various kinds of silanol group constellations, and even the extraction of orthosilicic acid, are highly exothermic reaction in the presence of hydroxide ions. Thermogravimetric analysis, FT-IR, XRD and X-ray fluorescence spectrometry performed on halloysite treated at high pH conditions indicate that the adsorption of water on the oute…
Microemulsion encapsulated into halloysite nanotubes and their applications for cleaning of a marble surface
2018
Halloysite nanotubes were used to incorporate anionic surfactant micelles and an organic solvent to generate a cleaning system to be applied in Cultural Heritage restoration. The targeted adsorption is driven by electrostatic interactions based on the nanotubes peculiar charge separation. Namely anionic species are driven to the positively charged inner surface while being prevented from interacting with the halloysite outer surface that possesses a positive charge density. The hybrid organic/inorganic emulsion was characterized by dynamic light scattering. Analysis of the autocorrelation function allowed us to define the presence of surfactant aggregates inside/outside the nanotube lumen a…
Twisting graphene nanoribbons into carbon nanotubes
2011
Although carbon nanotubes consist of honeycomb carbon, they have never been fabricated from graphene directly. Here, it is shown by quantum molecular-dynamics simulations and classical continuum-elasticity modeling, that graphene nanoribbons can, indeed, be transformed into carbon nanotubes by means of twisting. The chiralities of the tubes thus fabricated can be not only predicted but also externally controlled. This twisting route is an opportunity for nanofabrication, and is easily generalizable to ribbons made of other planar nanomaterials.
Computational studies of torsional properties of single-walled carbon nanotubes
2010
Current thesis presents computational studies of the torsional twist in single walled carbon nanotubes (SWCNTs). Since SWCNTs can be viewed as rolled up graphene sheets, our aim is to explain their torsion constants via shear mod- ulus of graphene in pristine, and single- and double vacancy cases. In addition, fundamental energy gap response to torsion is investigated. Calculations of defected structures is computationally expensive as it requires larger simula- tion cell with large number of atoms. To reduce the cost of computations we take the advantage of chiral symmetry of nanotubes instead of translational one, and faster performance of density-functional tight-binding method compared …
Characterization of electrospun poly(lactide) composites containing multiwalled carbon nanotubes
2019
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors would like to thank the Ministry of Education, Science and Technological Development, Republic of Serbia, for funding projects III45022 and 172056 and European Cooperation in Science and Technology (COST) action CA15107.