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1.
Nanotechnology ; 22(23): 235501, 2011 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-21474871

RESUMO

Hydrogen/sodium titanate nanotubes (TNTs) were investigated as hydrogen (H(2)) sensors. TNT films exhibit good sensing properties and a large response, in particular at room temperature. Electrical conductivity measurements performed under different atmospheres from 25 to 300 °C indicate that, for T > 100 °C, conduction is thermally activated and can be attributed to electronic transport, whereas for T < 100 °C conduction is dominated by protonic transport. The T dependence of the H(2) sensitivity was determined and related to this variation in the dominant transport mechanism. For low T, H(2) sensing originates from the modulation in protonic conduction. Such modulation was attributed to the creation/destruction of surface hydroxyl groups.

2.
Artigo em Inglês | MEDLINE | ID: mdl-30543862

RESUMO

Given the increasing use of carbon nanotubes (CNT) in several industries and technological applications, it is essential to perform in vivo toxicological studies with these nanomaterials to evaluate their potential ecotoxicity. Dopamine (DA) and serotonin (5HT) are key neurotransmitters for brain functions and behavioral responses. Determination of DA and 5HT were performed in brain samples from zebrafish Danio rerio exposed i.p. to single-walled CNT (SWCNT), besides analyzing acetylcholinesterase (AChE) and ectonucleotidases activity, lipid peroxidation and total antioxidant capacity. Results showed that treatment with SWCNT increased between 3 and 6-fold the concentration of DA and 5HT (p < 0.05). Similarly, a significant reduction (p < 0.05) in AChE activity was observed in the brains of SWCNT exposed zebrafish when compared to the control groups. Cholinergic, serotonergic, and dopaminergic systems, through AChE activity and serotonin and dopamine levels, respectively were affected by SWCNT in the zebrafish brain. Alterations in these neurotransmitters can potentially affect several physiological and behavioral that they control.


Assuntos
Antioxidantes/metabolismo , Nanotubos de Carbono/toxicidade , Síndromes Neurotóxicas , Neurotransmissores/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Peroxidação de Lipídeos/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Peixe-Zebra
3.
Appl Radiat Isot ; 69(1): 118-21, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20729094

RESUMO

We report a novel material for use in (125)I brachytherapy that consists of amorphous carbon films grown by ion-beam-assisted deposition and doped with Xe (5 at%) by implantation. Samples of these films grown on Si substrates were irradiated with neutrons in a TRIGA-I nuclear reactor for the production (125)Xe, and latter characterized by gamma spectroscopy. The results indicate that the (124)Xe was efficiently converted into (125)Xe, the precursor of (125)I, and support the activity calculations for a model brachytherapy seed.


Assuntos
Braquiterapia/métodos , Carbono/química , Radioisótopos do Iodo/química , Isótopos de Xenônio/química , Humanos , Radioisótopos do Iodo/farmacologia , Espectrometria gama
4.
Phys Rev Lett ; 100(25): 256804, 2008 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-18643691

RESUMO

We report the direct experimental observation of the semiconductor-metal transition in single-wall carbon nanotubes (SWNTs) induced by compression with the tip of an atomic force microscope. This transition is probed via electric force microscopy by monitoring SWNT charge storage. Experimental data show that such charge storage is different for metallic and semiconducting SWNTs, with the latter presenting a strong dependence on the tip-SWNT force during injection. Ab initio calculations corroborate experimental observations and their interpretation.

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