Search results for "nanostructure"

Nanostrukturētu pārklājumu iegūšana ar Peninga šūnu, to fizikālo īpašību izpēte un modificēšanas iespējas

2005

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…

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…

Cerium oxyhydroxide nanowire growth via electrogeneration of base in nonaqueous electrolytes

2008

The preparation of compact cerium oxyhydroxide nanowires into anodic alumina membranes from cerium chloride in ethanol solution via electrogeneration of base is reported. Scanning electron microscopy analyses indicate that dense, well-aligned, and highly ordered nanowires can be formed in a wide range of applied potentials and current densities in alcoholic solution. The employment of water brings to a hybrid nanotube/nanowire structure, suggesting a key role of the electrolyte nature in determining the morphology of the deposit. Electrochemical findings and X-ray diffraction analysis have shown that nanowires are constituted by a Ce(III)/Ce(IV) oxyhydroxide that can be completely oxidized …

Chemical modification of halloysite nanotubes for controlled loading and release.

2020

Clay minerals have been used for medical purposes from ancient times. Among them, the halloysite nanotube, an aluminosilicate of the kaolin group, is an emerging nanomaterial which possesses peculiar chemical characteristics. By means of suitable modifications, such as supramolecular functionalization or covalent modifications, it is possible to obtain novel nanomaterials with tunable properties for several applications. In this context the covalent grafting of suitable organic moieties on the external surface or in the halloysite lumen has been exploited to improve the loading and release of several biologically active molecules. The resulting hybrid nanomaterials have been applied as drug…

Encapsulation of single-molecule magnets in carbon nanotubes

2011

Next-generation electronic, photonic or spintronic devices will be based on nanoscale functional units, such as quantum dots, isolated spin centres or single-molecule magnets. The key challenge is the coupling of the nanoscale units to the macroscopic world, which is essential for read and write purposes. Carbon nanotubes with one macroscopic and two nanoscopic dimensions provide an excellent means to achieve this coupling. Although the dimensions of nanotube internal cavities are suitable for hosting a wide range of different molecules, to our knowledge, no examples of molecular magnets inserted in nanotubes have been reported to date. Here we report the successful encapsulation of single-…

Symmetry and Models of Double-Wall BN and TiO2 Nanotubes with Hexagonal Morphology

2011

The line symmetry groups for one-periodic (1D) nanostructures with rotohelical symmetry have been applied for symmetry analysis of double-wall boron nitride and titania nano- tubes (DW BN and TiO2 NTs) formed by rolling up the stoichiometric two-periodic (2D) slabs of hexagonal structure with the same or opposite orientation of translation and chiral vectors. We have considered the two sets of commensurate DW BN and TiO2 NTs with either armchair- or zigzag-type chiralities, i.e., (n1,n1)@(n2,n2 )o r (n1,0)@(n2,0), respectively. To establish theequilibriuminterwalldistancescorrespondingtotheminimaof energy, we have varied chiral indices n1 and n2 of the constituent single-wall (SW) nanotubes…

Carbon nanotube bags: catalytic formation, physical properties, two-dimensional alignment and geometric structuring of densely filled carbon tubes.

2001

The catalytic CVD synthesis, using propyne as carbon precursor and Fe(NO3)3 as catalyst precursor inside porous alumina, gives carbon nanotube (CNT) bags in a well-arranged two-dimensional order. The tubes have the morphology of bags or fibers, since they are completely filled with smaller helicoidal CNTs. This morphology has so far not been reported for CNTs. Owing to the dense filling of the outer mother CNTs with small helicoidal CNTs, the resulting CNT fibers appear to be stiff and show no sign of inflation, as sometimes observed with hollow CNTs. The fiber morphology was observed by raster electron microscopy (REM), transmission electron microscopy (TEM), and atomic force microscopy (A…

Enhancement of photoelectrochemical activity for water splitting by controlling hydrodynamic conditions on titanium anodization

2015

This work studies the electrochemical and photoelectrochemical properties of a new type of TiO2 nanostructure (nanosponge) obtained by means of anodization in a glycerol/water/NH4F electrolyte under controlled hydrodynamic conditions. For this purpose different techniques such as Scanning Electronic Microscopy (SEM), Raman Spectroscopy, Electrochemical Impedance Spectroscopy (EIS) measurements, Mott–Schottky (M−S) analysis and photoelectrochemical water splitting tests under standard AM 1.5 conditions are carried out. The obtained results show that electron–hole separation is facilitated in the TiO2 nanosponge if compared with highly ordered TiO2 nanotube arrays. As a result, nanosponges en…

Validation of a constrained 2D slab model for water adsorption simulation on 1D periodic TiO2 nanotubes

2018

Abstract Solar light driven hydrogen evolution is one focus of modern materials research. Among the different emerging technologies, particular interest is devoted towards metal oxide photocatalysts in the form of various 1D nanostructures. Presently, the mismatch between regular structures that can be synthesized and the largest structures that are feasible for computer simulation is still very large. For example, an in-depth study of water adsorption on nanotube (NT) surfaces requires, in addition to DFT calculations, molecular dynamics simulations to take into account the disordered nature of the aqueous phase. To completely immerse even a very thin nanotube into an aqueous system requir…