Time filter

Source Type

Vervacke C.,Leibniz Institute for Solid State and Materials Research | Bof Bufon C.C.,Leibniz Institute for Solid State and Materials Research | Bof Bufon C.C.,Brazilian Nanotechnology National Laboratory | Thurmer D.J.,Leibniz Institute for Solid State and Materials Research | And 4 more authors.
Analytical Chemistry | Year: 2012

Here, we demonstrate the fabrication, characterization, and tailoring of porous organic nanomembranes and their direct integration on inorganic substrates for sensing applications. The chemically prepared nanomembranes can be integrated on both conducting and insulating substrates by either transfer or direct synthesis. We also successfully demonstrate their use for the detection of commonly used acids including HCl, H2SO4, or H 3PO4 and their respective counterions, chlorides, sulfates, and phosphates. Impressively, the in situ acid detection is achieved down to 5 nmol·L-1, while the quantification is feasible between 5 μmol·L-1 and 10 mmol·L-1. These values are among the lowest values reported so far in literature. Furthermore, the organic nanomembrane based sensor covers a wide concentration range of almost 8 orders of magnitude including the environmental limits currently adopted. © 2012 American Chemical Society. Source

Barbosa A.F.,Federal University of Alfenas | Barbosa V.M.P.,Federal University of Alfenas | Bettini J.,Brazilian Nanotechnology National Laboratory | Luccas P.O.,Federal University of Alfenas | Figueiredo E.C.,Federal University of Alfenas
Talanta | Year: 2015

In this paper, we propose a new sorbent that is able to extract metal ions directly from untreated biological fluids, simultaneously excluding all proteins from these samples. The sorbent was obtained through the modification of carbon nanotubes (CNTs) with an external bovine serum albumin (BSA) layer, resulting in restricted access carbon nanotubes (RACNTs). The BSA layer was fixed through the interconnection between the amine groups of the BSA using glutaraldehyde as cross-linker. When a protein sample is percolated through a cartridge containing RACNTs and the sample pH is higher than the isoelectric point of the proteins, both proteins from the sample and the BSA layer are negatively ionized. Thus, an electrostatic repulsion prevents the interaction between the proteins from the sample on the RACNTs surface. At the same time, metal ions are adsorbed in the CNTs (core) after their passage through the chains of proteins. The Cd 2+ ion was selected for a proof-of-principle case to test the suitability of the RACNTs due to its toxicological relevance. RACNTs were able to extract Cd2+ and exclude almost 100% of the proteins from the human serum samples in an online solid-phase extraction system coupled with thermospray flame furnace atomic absorption spectrometry. The limits of detection and quantification were 0.24 and 0.80 μg L-1, respectively. The sampling frequency was 8.6 h-1, and the intra- and inter-day precisions at the 0.80, 15.0, and 30.0 μg L-1 Cd 2+ levels were all lower than 10.1% (RSD). The recoveries obtained for human blood serum samples fortified with Cd2+ ranged from 85.0% to 112.0%. The method was successfully applied to analyze Cd2+ directly from six human blood serum samples without any pretreatment, and the observed concentrations ranged from Source

Barbosa V.M.P.,Federal University of Alfenas | Barbosa A.F.,Federal University of Alfenas | Bettini J.,Brazilian Nanotechnology National Laboratory | Luccas P.O.,Federal University of Alfenas | Figueiredo E.C.,Federal University of Alfenas
Talanta | Year: 2016

Oxidized carbon nanotubes were covered with layers of bovine serum albumin to result in so-called restricted-access carbon nanotubes (RACNTs). This material can extract Pb2+ ions directly from untreated human blood serum while excluding all the serum proteins. The RACNTs have a protein exclusion capacity of almost 100% and a maximum Pb2+ adsorption capacity of 34.5 mg g-1. High resolution transmission electron microscopy, scanning transmission electron microscopy and energy dispersive spectroscopy were used to confirm the BSA layer and Pb2+ adsorption sites. A mini-column filled with RACNTs was used in an on-line solid phase extraction system coupled to a thermospray flame furnace atomic absorption spectrometry. At optimized experimental conditions, the method has a detection limit as low as 2.1 μg L-1, an enrichment factor of 5.5, and inter- and intra-day precisions (expressed as relative standard deviation) of <8.1%. Recoveries of the Pb2+ spiked samples ranged from 89.4% to 107.3% for the extraction from untreated human blood serum. © 2015 Published by Elsevier B.V. Source

Tallarico D.A.,Federal University of Sao Carlos | Gobbi A.L.,Brazilian Nanotechnology National Laboratory | Paulin Filho P.I.,Federal University of Sao Carlos | Maia Da Costa M.E.H.,Pontifical Catholic University of Rio de Janeiro | Nascente P.A.P.,Federal University of Sao Carlos
Materials Science and Engineering C | Year: 2014

Low modulus of elasticity and the presence of non-toxic elements are important criteria for the development of materials for implant applications. Low modulus Ti alloys can be developed by designing β-Ti alloys containing non-toxic alloying elements such as Nb and Zr. Actually, most of the metallic implants are produced with stainless steel (SS) because it has adequate bulk properties to be used as biomaterials for orthopedic or dental implants and is less expensive than Ti and its alloys, but it is less biocompatible than them. The coating of this SS implants with Ti alloy thin films may be one alternative to improve the biomaterial properties at a relatively low cost. Sputtering is a physical deposition technique that allows the formation of nanostructured thin films. Nanostructured surfaces are interesting when it comes to the bone/implant interface due to the fact that both the surface and the bone have nanoscale particle sizes and similar mechanical properties. TiNbZr thin films were deposited on both Si(111) and stainless steel (SS) substrates. The TiNbZr/Si(111) film was used as a model system, while the TiNbZr/SS film might improve the biocompatibility and extend the life time of stainless steel implants. The morphology, chemical composition, Young's modulus, and hardness of the films were analyzed by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), and nanoindentation. © 2014 Elsevier B.V. Source

Paula A.J.,University of Campinas | Montoro L.A.,Brazilian Nanotechnology National Laboratory | Filho A.G.S.,Federal University of Ceara | Alves O.L.,University of Campinas
Chemical Communications | Year: 2012

The highly uniform micro- and mesoporous SiO 2 nanoparticles (40-70 nm) are hierarchically functionalized with antagonistic groups: hydrophobic (phenyl) on the internal pores and hydrophilic (methyl-phosphonate) on the external surface. Considering the large hydrophobic internal coating and the long-term colloidal stability, these systems are suitable nanocarriers by using the host-guest approach. © 2012 The Royal Society of Chemistry. Source

Discover hidden collaborations