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Lisbon, Portugal

Neves A.I.S.,Telecommunications Institute of Portugal | Santos I.C.,University of Lisbon | Coutinho J.T.,University of Lisbon | Pereira L.C.J.,University of Lisbon | And 6 more authors.
European Journal of Inorganic Chemistry | Year: 2014

Transition metal complexes based on the new ligand 5-methylthiophene-2,3- dithiolate (α-mtpdt) and Au, Ni, Fe, Co, Cu Pt and Pd were prepared as tetraalkylammonium and tetraarylphosphonium salts and characterised by cyclic voltammetry, X-ray diffraction, electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility measurements. Except for the Cu complex, which forms a four-metal cluster [Cu4(α-mtpdt) 3]2-, the metals form complexes of the general formula [M(α-mtpdt)2]. With Au, Ni and Fe, the complexes are directly obtained from the synthesis as monoanionic salts, and the isostructural crystal structures of [nBu4N][Ni(α-mtpdt)2] and [nBu 4N][Au(α-mtpdt)2] were solved by single-crystal X-ray diffraction. For M = Co, Pt and Pd, both monoanionic and dianionic salts were obtained, and the crystal structures of [Ph4As] 2[Co(α-mtpdt)2] and [Ph4As] 2[Pd(α-mtpdt)2] were determined by single-crystal X-ray diffraction. The Co compound presents a rare tetrahedral coordination geometry. The oxidation of the monoanionic Ni and Au complexes with iodine leads to stable neutral complexes, which are fairly soluble in common organic solvents such as acetonitrile and dichloromethane. The crystal structure of [Ni(α-mtpdt)2] was solved by single-crystal X-ray diffraction. The electrical conductivities of the neutral Ni and Au complexes as polycrystalline compressed pellets are typical of a semiconductor; the room-temperature conductivities are 5.2×10-7 and 8.7×10-5 Scm-1, and the activation energies are 325 and 287 meV, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sousa C.T.,University of Porto | Leitao D.C.,INESC MN | Proenca M.P.,University of Porto | Apolinario A.,University of Porto | And 3 more authors.
Nanotechnology | Year: 2011

The role of the alumina barrier layer thickness (δb) on the growth of Ni nanowires (NWs) in porous anodic alumina (PAA) has been revealed. By varying the final anodization voltage to form dendrites at the bottom of the nanoporous structure, we are able to optimize δb (in the 2-16nm range), allowing us to obtain a Ni pore filling percentage (fp) of almost 100% for δb = 10nm. However, deviations from this optimal δb-value led to a strong decrease of fp. Moreover, an increase of the electrodeposition efficiency (EE) and NW homogeneity was also verified for δb up to 10nm. Such increase in nominal δb leads to a consistent growth rate in all pores and consequently a complete and uniform nanopore filling. On the other hand, the decrease in electrodeposition efficiency visible for δb > 10nm is related with hydrogen evolution and dielectric breakdown of the insulator layer due to the required high deposition voltages. Non-uniform NW growth is then visible, with the consequent decrease in f p. The control of the pore filling and length homogeneity of the fabricated 1D metallic nanostructures, combined with the ability to adjust the pore dimensions of PAA, can bring novel approaches for the fabrication of nano-objects and thus exciting new applications. © 2011 IOP Publishing Ltd.

Camara-Martos F.,University of Cordoba, Spain | Da Costa J.,University of Aveiro | Justino C.I.L.,University of Aveiro | Cardoso S.,INESC MN | And 2 more authors.
Talanta | Year: 2016

This paper reports the tuning of a fast, disposable, and label-free biosensor for quantification of iron (III) in food liquid samples such as wine. The biosensor is based on a field effect transistor(FET) where a net work of single-walled carbonnanotubes (SWCNTs) acts as the conductor channel, constituting carbonnanotubes field effect transistors (CNTFETs). An antibody such as transferrin with two specific high-affinity iron (III) binding sites, directly adsorbed to SWCNTs, was used as immunoreaction. Several individual CNTFETs were tested showing a linear range between 0.05 and 2 ng mL-1 and a limit of quantification below 0.05 ng mL-1, much lower than previously reported analytical techniques. The mean coefficient of variation was 0.13% showing a low variability of the analytical response. On the other hand, it was not observed interference effect of zinc (II) ion at least until 1:4 iron-zinc ratio. Finally, recovery percentages of spiked wine samples were around 100%, showing the high accuracy of method. The main advantages of the devices developed are their speed, convenience (it is an economical method), and the avoidance excessive handling samples since they do not require further pre-treatment of samples. © 2016 Elsevier B.V. All rights reserved.

Belkhamssa N.,University of Sfax | Justino C.I.L.,University of Aveiro | Justino C.I.L.,Piaget Institute | Santos P.S.M.,University of Aveiro | And 5 more authors.
Talanta | Year: 2016

This work reports the construction of a fast, disposable, and label-free immunosensor for the determination of atrazine. The immunosensor is based on a field effect transistor (FET) where a network of single-walled carbon nanotubes (SWCNTs) acts as the conductor channel, constituting carbon nanotubes field effect transistors (CNTFETs). Anti-atrazine antibodies were adsorbed onto the SWCNTs and subsequently the SWCNTs were protected with Tween 20 to prevent the non-specific binding of bacteria or proteins. The principle of the immunoreaction consists in the direct adsorption of atrazine specific antibodies (anti-atrazine) to SWCNTs networks. After exposed to increasing concentrations of atrazine, the CNTFETs could be used as useful label-free platforms to detect atrazine. Under the optimal conditions, a limit of detection as low as 0.001 ng mL-1 was obtained, which is lower than that of other methods for the atrazine detection, and in a working range between 0.001 and 10 ng mL-1. The average recoveries obtained for real water samples spiked with atrazine varied from 87.3% to 108.0%. The results show that the constructed sensors display a high sensitivity and could be useful tools for detecting pesticides like atrazine at low concentrations. They could be also applied to the determination of atrazine in environmental aqueous samples, such as seawater and riverine water. © 2015 Elsevier B.V. Allrightsreserved.

Gatzen H.H.,Leibniz University of Hanover | Freitas P.J.P.,INESC MN | Obermeier E.,TU Berlin | Robertson J.,University of Cambridge
IEEE Transactions on Magnetics | Year: 2010

Taking advantage of microelectromechanical system technology, a slider with an integrated microactuator (SLIM) for use in hard disc drives was devised. It allows both a lowering to the operating static flying height and a second-stage actuation for ultraprecision track following. By placing the read/write element on a small chiplet rather than on the trailing edge of a slider, the design promises to be cost competitive. This paper provides an overview over the research results achieved so far. It discusses the fabrication technology applied for fabricating both the micromagnetics and micromechanics and presents experimental dynamic test results on SLIM devices which-although not yet flyable-do have fully functional microactuators. © 2010 IEEE.

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