Search results for " Nanotubes"

Palladium nanoparticles immobilized on halloysite nanotubes covered by a multilayer network for catalytic applications

2018

The synthesis of pure fine chemicals for industrial purposes is one of the most attractive challenges of chemical research. The use of catalytic pathways mediated by palladium nanoparticles (PdNPs) for C-C bond formation is a useful way to obtain these kinds of compounds. To achieve this objective, the PdNPs can be efficiently loaded on a functionalized natural nanostructured support such as halloysite nanotubes (HNTs). Hybrid materials based on thiol functionalized halloysite nanotubes and highly cross-linked imidazolium salts were successfully developed and used for the stabilization of PdNPs. The HNT/Pd hybrids were thoroughly characterized from a physico-chemical point of view and teste…

Nanocarrier based on halloysite and fluorescent probe for intracellular delivery of peptide nucleic acids

2022

The development of systems able to deliver genetic material into a target site is a challenge for modern medicine. Single-stranded peptide nucleic acids have attracted attention as promising therapeutic molecules for diagnostic and gene therapy. However, their poor cell membrane permeability represents a drawback for biomedical applications. Halloysite nanotubes (HNTs) are emerging materials in drug delivery applications both for their ability to penetrate cell membranes and for enhancing the solubility of drugs in biological media. Herein, we report the first example of the use of a nanocarrier based on halloysite labelled with fluorescent switchable halochromic oxazine molecules, to deliv…

Exploring the anticancer activity and the mechanism of action of pyrrolomycins F obtained by microwave-assisted total synthesis

2023

Pyrrolomycins (PMs) are a family of naturally occurring antibiotic agents, isolated from the fermentation broth of Actinosporangium and Streptomyces species. Pursuing our studies on pyrrolomycins, we performed the total synthesis of the F-series pyrrolomycins (1–4) by microwave-assisted synthesis (MAOS), thus obtaining the title compounds in excellent yields (63–69%). Considering that there is no evidence so far of the anticancer effect of this class of compounds, we investigated PMs for their antiproliferative activity against HCT116 and MCF-7 cancer cell lines. PMs showed anticancer activity at submicromolar level with a minimal effect on normal epithelial cell line (hTERT RPE-1), and the…

Temperature Dependence of Electronic Transitions of Single-Wall Carbon Nanotubes:  Observation of an Abrupt Blueshift in Near-Infrared Absorption

2007

Near-infrared (NIR) absorption spectra of single-wall carbon nanotube (SWNT) films are studied between 10 and 293 K. The most prominent effect is the shift of bands with temperature. Some nanotubes show a redshift of transition upon increasing temperature while some show blueshift and others show no shift. The shift is interpreted to originate mainly from the effect of strain induced in the tubes because of interaction with the environment. In particular, at temperatures T = 175−225 K, for some bands, there is an abrupt large blueshift, which is interpreted to originate from interaction of the nanotubes with water. Two models could be considered to explain the effect:  (1) strain induced by…

Ab initio simulations on the atomic and electronic structure of single-walled BN nanotubes and nanoarches

2009

To simulate the perfect single-walled boron nitride nanotubes and nanoarches with armchair- and zigzag-type chiralities and uniform diameter of � 5 nm, we have constructed their one-dimensional (1D) periodic models. In this study, we have compared the calculated properties of nanotubes with those for both hexagonal and cubic phases of bulk: bond lengths, binding energies per B–N bond, effective atomic charges as well as parameters of total and projected one-electron densities of states. For both phases of BN bulk, we have additionally verified their lattice constants. In the density functional theory (DFT), calculations performed using formalism of the localized Gaussian-type atomic functio…

Photo-oxidation resistance of polyethylene/carbon nanotubes composites: aspect ratio and surface functionalization effect

2012

Photo-oxidation behaviour of polystyrene-block-polybutadiene-block-polystyrene /CNTs nanocomposites

2014

Synergistic effect between hydrodynamic conditions during Ti anodization and acidic treatment on the photoelectric properties of TiO2 nanotubes

2015

In the present work, the combined influence of controlled hydrodynamic conditions during Ti anodization and the acidic treatment with HClO4 on the photoelectric properties of mixed anatase/rutile TiO2 nanotubes has been studied. Anodized samples were analyzed by means of Field Emission Scanning Electronic Microscopy (FE-SEM), Confocal Raman Microscopy, electrochemical measurements (electrochemical impedance spectroscopy and Mott-Schottky analysis) and photoelectrochemical measurements. It has been observed that the use of hydrodynamic conditions increases the surface area of nanotubes, while acidic treatment enhances their conductivity. Besides, there is a clear synergistic effect between t…

Photoelectrocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 by TiO2 nanotubes

2020

In this paper, the first photoelectrocatalytic (PEC) 3-pyridinemethanol oxidation to 3-pyridinemethanal and vitamin B-3 was investigated. To meet this aim, efficient nanotube structured TiO2 on a Ti plate as a photoanode was prepared by an anodic oxidation method in ethylene glycol and characterized by XRD, SEM, and photocurrent techniques. The effect of nanotube morphology, applied potential, Na2SO4 concentration, stirring speed of solution, and pH on the reaction activity and product selectivities were investigated. The TiO2 phase of all of the anodes was mainly the anatase one. The PEC activity, the intensity of the XRD peak and the photocurrent increased by increasing the nanotube lengt…

Photoelectrochemical Evidence of Cu2O/TiO2 Nanotubes Hetero-Junctions formation and their Physicochemical Characterization

2014

Cu2O/TiO2 nanotubes heterojunctions were fabricated by electrochemical deposition of cuprous oxide on TiO2 nanotubes arrays grown by anodizing. X-ray diffraction and Raman Spectroscopy analysis allows for identification of Cu2O, whose morphological features were studied by Scanning Electron Microscopy as a function of the charge circulated during the electrodeposition step. Photoelectrochemical measurements in aqueous solutions evidenced a red shift of the light absorption threshold of TiO2 nanotubes due to the presence of cuprous oxide even for very low circulated charges, while electrochemical impedance measurements proved a significant reduction of the electrode impedance due the presenc…