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Hamilton Jr. R.F.,University of Montana | Xiang C.,WVNano Initiative | Xiang C.,West Virginia University | Li M.,WVNano Initiative | And 6 more authors.
Inhalation Toxicology | Year: 2013

This study examined the consequences of surface carboxylation of multiwalled carbon nanotubes (MWCNT) on bioactivity. Since commercial raw MWCNT contain impurities that may affect their bioactivity, HCl refluxing was exploited to purify raw "as-received" MWCNT by removing the amorphous carbon layer on the MWCNT surface and reducing the metal impurities (e.g. Ni). The removal of amorphous carbon layer was confirmed by Raman spectroscopy and thermogravimetric analysis. Furthermore, the HCl-purified MWCNT provided more available reaction sites, leading to enhanced sidewall functionalization. The sidewall of HCl-purified MWCNT was further functionalized with the-COOH moiety by HNO3 oxidation. This process resulted in four distinct MWCNT: raw, purified,-COOH-terminated raw MWCNT, and-COOH-terminated purified MWCNT. Freshly isolated alveolar macrophages from C57Bl/6 mice were exposed to these nanomaterials to determine the effects of the surface chemistry on the bioactivity in terms of cell viability and inflammasome activation. Inflammasome activation was confirmed using inhibitors of cathepsin B and Caspase-1. Purification reduced the cell toxicity and inflammasome activation slightly compared to raw MWCNT. In contrast, functionalization of MWCNT with the-COOH group dramatically reduced the cytotoxicity and inflammasome activation. Similar results were seen using THP-1 cells supporting their potential use for high-throughput screening. This study demonstrated that the toxicity and bioactivity of MWCNT were diminished by removal of the Ni contamination and/or addition of-COOH groups to the sidewalls. © 2013 Informa UK Ltd All rights reserved.

Li M.,WVNano Initiative | Cushing S.K.,WVNano Initiative | Cushing S.K.,Stanford University | Hornak L.A.,West Virginia University | And 3 more authors.
Journal of Physical Chemistry Letters | Year: 2011

This Letter deals with the effect of the particle size on the energy transfer from CdSe/ZnS quantum dots to the proximal gold nanoparticles with different sizes. The 3 nm sized gold nanoparticles have negligible localized surface plasmon resonance (LSPR) absorption and quench the fluorescence emission of the quantum dots with a 1/d4 distance-dependence, indicating the nanometal surface energy transfer (NSET) mechanism. The 15 and 80 nm sized gold nanoparticles have strong LSPR absorption bands that overlap with the emission band of the quantum dots. The energy transfer efficiency depends on the 1/d 6 separation distance, which is dominated by the dipole-dipole interaction according to Förster resonance energy transfer (FRET). The 80 nm sized gold nanoparticle displays higher quenching efficiency due to the increased spectral overlap of the LSPR band with the emission band of quantum dots. © 2011 American Chemical Society.

Wei M.-Y.,CAS Research Center for Eco Environmental Sciences | Wei M.-Y.,West Virginia University | Guo L.-H.,CAS Research Center for Eco Environmental Sciences | Famouri P.,WVNano Initiative | Famouri P.,West Virginia University
2010 10th IEEE Conference on Nanotechnology, NANO 2010 | Year: 2010

Nano-materials show great electrocatalysis on redox reaction, e.g. metal nano-particles and carbon nano-tube. The electrocatalytic activity of semiconductor nano-particles, however, has not been reported although semiconductor was widely used as an electrode substrate for a variety of applications. In this work, we demonstrated a remarkable catalysis on electro-oxidation of ascorbic acid on indium tin oxide nano-particles (ITO NPs)-modified electrode. It was found that the oxidation potential of ascorbic acid decreased by ∼800 mV, compared with that on sputtered ITO film electrode. Coupling with X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) emission studies, the catalytic effect can be deduced to relate with the existence of oxygen vacancy defects in In2O 3 crystals, one of the components of ITO. The findings could shed light on fabricating novel electrochemical device for biosensing in future work. ©2010 IEEE.

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