Search results for "OTU"
showing 10 items of 2539 documents
Computational study of water adsorption on halloysite nanotube in different pH environments
2020
Abstract The comprehension of structural and energetic features of halloysite nanotube (HNT) in different chemical environments plays a crucial role in developing new HNT based materials. So far these aspects were investigated by means of laboratory techniques that hardly are able to provide hints at atomistic level of detail. Our investigation aims to obtain such accurate informations through density functional theory calculations on HNT models, in order to figure out the most stable forms of HNT under different pH conditions. It turns out that, at low pH, the preferred protonation sites are located in the inner aluminic surface while in alkaline medium the silicic layer can show delocaliz…
First principles modeling of 3d-metal doped three-layer fluorite-structured TiO2 (4,4) nanotube to be used for photocatalytic hydrogen production
2017
This study has been supported by the EC ERA.Net RUS Plus project No. 237 WATERSPLIT, Russian Basic Research Foundation No. 16-53-76019, and additionally by the IMIS2 Program (Latvia). The authors are also indebted to R. A. Evarestov and O. Lisovski for stimulating discussions as well as to A. Chesnokov for technical assistance.
Effect of Polymer Length on the Adsorption onto Aluminogermanate Imogolite Nanotubes
2021
This study evidences the adsorption of model nonionic polymers onto aluminogermanate imogolite nanotubes, attractive porous nanofillers with potential molecular loading and release applications. We resolve the underlying mechanisms between nanotubes and polyethylene glycols with different molecular weights by means of nanoisothermal titration calorimetry. The analysis of the results provides a direct thermodynamic characterization, allowing us to propose a detailed description of the energetics involved in the formation of polymer/imogolite complexes. The affinity toward the nanotube surface is enthalpy-driven and strongly depends on the polymer chain length, which significantly affects the…
Controlling electrical percolation in multicomponent carbon nanotube dispersions
2011
Carbon nanotube reinforced polymeric composites can have favourable electrical properties, which make them useful for applications such as flat-panel displays and photovoltaic devices. However, using aqueous dispersions to fabricate composites with specific physical properties requires that the processing of the nanotube dispersion be understood and controlled while in the liquid phase. Here, using a combination of experiment and theory, we study the electrical percolation of carbon nanotubes introduced into a polymer matrix, and show that the percolation threshold can be substantially lowered by adding small quantities of a conductive polymer latex. Mixing colloidal particles of different …
Launching propagating surface plasmon polaritons by a single carbon nanotube dipolar emitter.
2011
International audience; We report on the excitation of propagating surface plasmon polaritons in thin metal films by a single emitter. Upon excitation in the visible regime, individual semiconducting single-walled carbon nanotubes are shown to act as directional near-infrared point dipole sources launching propagating surface plasmons mainly along the direction of the nanotube axis. Plasmon excitation and propagation is monitored in Fourier and real space by leakage radiation microscopy and is modeled by rigorous theoretical calculations. Coupling to plasmons almost completely reshapes the emission of nanotubes both spatially and with respect to polarization as compared to photoluminescence…
Surfactant-Dependent Exciton Mobility in Single-Walled Carbon Nanotubes Studied by Single-Molecule Reactions
2010
Measurements of stepwise photoluminescence quenching in individual, (n,m)-selected single-walled carbon nanotubes (SWCNTs) undergoing chemical reaction have been analyzed to deduce mobilities of optically generated excitons. For (7,5) nanotubes, the mean exciton range varies between approximately 140 and 240 nm for different surfactant coatings and correlates weakly with nanotube PL intensity. The results are consistent with a model of localized SWCNT excitons having substantial diffusional mobility along the nanotube axis.
Hierarchical Assembly of TiO2 Nanoparticles on WS2 Nanotubes Achieved Through Multifunctional Polymeric Ligands
2007
Thefunctionalization of nanotubes is required in order to bene-fit from their outstanding properties, as any application inmaterials and devices is hindered by processing and manipu-lation difficulties. Only the attachment of appropriate chem-ical functionalities on the nanotube surface allows tailoringof the properties for the respective applications. As an ex-ample, the enhancement of the nanotube solubility is onemajor task since most pristine nanotubes are insoluble inboth water and organic solvents. Thus, the improvement ofthe solubility by chemical functionalization is an importantconcept for synthetic chemists and materials scientists. Tai-loring of the surface chemical bonds might a…
In situ nucleation of carbon nanotubes by the injection of carbon atoms into metal particles.
2007
The synthesis of carbon nanotubes (CNTs) of desired chiralities and diameters is one of the most important challenges in nanotube science and achieving such selectivity may require a detailed understanding of their growth mechanism. We report the formation of CNTs in an entirely condensed phase process that allows us, for the first time, to monitor the nucleation of a nanotube on the spherical surface of a metal particle. When multiwalled CNTs containing metal particle cores are irradiated with an electron beam, carbon from graphitic shells surrounding the metal particles is ingested into the body of the particle and subsequently emerges as single-walled nanotubes (SWNTs) or multiwalled nan…
Template electrosyntesis of CeO2 nanotubes
2007
Nanotube arrays of CeO2 were produced in a single step by potentiostatic electrochemical deposition from a non-aqueous electrolyte, using anodic alumina membrane templates. The CeO2 nanotubes showed a polycrystalline structure, and they were assembled in the membrane nanochannels. The nanotubes had somewhat uniform diameters, with an average external value of about 210 nm, and a maximum length of about 60 µm; the latter parameter was controlled by the electrodeposition time. Each single nanotube was found to consist of crystalline grains having a size of about 3 nm. Raman analysis shows that these CeO2 nanotubes are suitable for catalytic applications.
Multiwalled carbon nanotube reinforced polymer composites
2008
Due to their high stiffness and strength, as well as their electrical conductivity, carbon nanotubes are under intense investigation as fillers in polymer matrix composites. The nature of the carbon nanotube/polymer bonding and the curvature of the carbon nanotubes within the polymer have arisen as particular factors in the efficacy of the carbon nanotubes to actually provide any enhanced stiffness or strength to the composite. Here the effects of carbon nanotube curvature and interface interaction with the matrix on the composite stiffness are investigated using micromechanical analysis. In particular, the effects of poor bonding and thus poor shear lag load transfer to the carbon nanotube…