INESC MN

Lisbon, Portugal
Lisbon, Portugal
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Justino C.I.L.,University of Aveiro | Rocha-Santos T.A.P.,University of Aveiro | Cardoso S.,University of Aveiro | Duarte A.C.,University of Aveiro | And 2 more authors.
TrAC - Trends in Analytical Chemistry | Year: 2013

We provide a state-of-the-art review of the main strategies for the enhancement of analytical performance of sensors using nanomaterials, particularly nanowires and carbon-based materials. We emphasize the way to overcome the problem of device-to-device variation. We discuss the study of the influence of nanomaterial characteristics, sensor dimensions and operational conditions on sensing performance, and the application of appropriate calibration models. © 2013 Elsevier Ltd.


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.


PubMed | University of Sfax, University of Aveiro and INESC MN
Type: | Journal: Talanta | Year: 2015

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.


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.


Alves H.,University of Aveiro | Neves A.I.S.,INESC MN | Gouveia W.,INESC MN | Silva R.A.L.,University of Lisbon | Belo D.,University of Lisbon
Chemical Communications | Year: 2015

We demonstrate that single component molecular metals can be used as conductive inks for printed electronics. The resistance is 0.3 kΩ sq-1, in a Ni complex, which is one order of magnitude better than that of commercial carbon based conductive inks. © 2015 The Royal Society of Chemistry.


Reis C.L.,INESC MN | Martins J.L.,INESC MN | Martins J.L.,University of Lisbon
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We present a first-principles calculation scheme for crystals that diagonalizes an effective Hamiltonian in a small atomic orbital basis set which is expanded in plane waves, yielding initial trial wave functions. A simple relaxation procedure applied to the trial wave functions expanded in a plane-wave basis can be used to generate a set of correction wave functions. We show that a subsequent diagonalization of the effective Hamiltonian in the subspace of the trial and correction wave functions is sufficient to obtain results quite close from a full converged calculation on the plane-wave basis set used for the projection. The proposed method should be simple to implement in other plane-wave computer programs and leads to substantial gains in computation speed while maintaining reasonable accuracy. © 2014 American Physical Society.


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.


PubMed | University of Aveiro, INESC MN and University of Cordoba, Spain
Type: | Journal: 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 2ngmL(-1) and a limit of quantification below 0.05ngmL(-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.


Chen X.,East China Normal University | Preitas P.P.,INESC MN
Nano-Micro Letters | Year: 2012

Magnetic tunnel junctions (MTJs) based on MgO barrier have been fabricated by sputtering single crystal MgO target and metal Mg target, respectively, using magnetic sputtering system Nordiko 2000. MgO barriers have been formed by a multi-step deposition and natural oxidization of Mg layer. Mg layer thickness, oxygen flow rate and oxidization time were adjusted and the tunnel magnetoresistance (TMR) ratio of optimal MTJs is over 60% at annealing temperature 385 °C. The (001) MgO crystal structure was obtained when the separation distance between MgO target and substrate is less than 6 cm. The TMR ratio of most MgO based MTJs are over 100% at the separation distance of 5 cm and annealing temperature 340°C. The TMR ratios of MTJs are almost zero when the separation distance ranges from 6 to 10 cm, due to the amorphous nature of the MgO film.


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.

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