Degree: Doctor

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Showing 5 latest publications. Total publications: 25
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1. Characterization of Carbon Nanomaterials Dispersions: Can Metal Decoration of MWCNTs Improve Their Physicochemical Properties?, Brandao, ATSC; Rosoiu, S; Costa, R Silva, AF Anicai, L; Enachescu, M; Pereira, CM in NANOMATERIALS, 2022, Volume: 12, 
Article,  Indexed in: wos  DOI: 10.3390/nano12010099 P-00W-3C7
Abstract A suitable dispersion of carbon materials (e.g., carbon nanotubes (CNTs)) in an appropriate dispersant media, is a prerequisite for many technological applications (e.g., additive purposes, functionalization, mechanical reinforced materials for electrolytes and electrodes for energy storage applications, etc.). Deep eutectic solvents (DES) have been considered as a promising "green" alternative, providing a versatile replacement to volatile organic solvents due to their unique physical-chemical properties, being recognized as low-volatility fluids with great dispersant ability. The present work aims to contribute to appraise the effect of the presence of MWCNTs and Ag-functionalized MWCNTs on the physicochemical properties (viscosity, density, conductivity, surface tension and refractive index) of glyceline (choline chloride and glycerol, 1:2), a Type III DES. To benefit from possible synergetic effects, AgMWCNTs were prepared through pulse reverse electrodeposition of Ag nanoparticles into MWCNTs. Pristine MWCNTs were used as reference material and water as reference dispersant media for comparison purposes. The effect of temperature (20 to 60 degrees C) and concentration on the physicochemical properties of the carbon dispersions (0.2-1.0 mg cm(-3)) were assessed. In all assessed physicochemical properties, AgMWCNTs outperformed pristine MWCNTs dispersions. A paradoxical effect was found in the viscosity trend in glyceline media, in which a marked decrease in the viscosity was found for the MWCNTs and AgMWCNTs materials at lower temperatures. All physicochemical parameters were statistically analyzed using a two-way analysis of variance (ANOVA), at a 5% level of significance.

2. Electrochemical and optical biosensing platforms for the immunorecognition of hazelnut Cor a 14 allergen, Costa, R Costa, J; Sagastizabal, I; Brandao, ATSC Moreira, P; Mafra, I; Silva, AF Pereira, CM in FOOD CHEMISTRY, 2021, ISSN: 0308-8146,  Volume: 361, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.1016/j.foodchem.2021.130122 P-00V-1MZ
Abstract Two immunosensors were advanced to target hazelnut Cor a 14 based on electrochemical and optical transduction. Both approaches were developed with two types of custom-made antibodies, namely anti-Cor a 14 IgG (rabbit) and anti-Cor a 14 IgY (hen's egg) targeting the Cor a 14 allergen. Antibody immobilisation was performed via EDC/NHS onto disposable screen-printed electrodes. The detection limit (LOD) of the electrochemical immunoassay for Cor a 14 was 5-times lower than the optical, being down to 0.05 fg mL-1 with a dynamic range of 0.1 fg mL-1 to 0.01 ng mL-1. Antibody selectivity was verified against non-target 2S albumins (potential crossreactive plant species). Anti-Cor a 14 IgY exhibited the best specificity, presenting minor cross-reactivity with peanut/walnut. Preliminary results of the application of anti-Cor a 14 IgY electrochemical immunosensor to incurred foods established a LOD of 1 mg kg- 1 of hazelnut in wheat (0.16 mg kg- 1 hazelnut protein).

3. Sustainable Preparation of Nanoporous Carbons via Dry Ball Milling: Electrochemical Studies Using Nanocarbon Composite Electrodes and a Deep Eutectic Solvent as Electrolyte, Brandao, ATSC; Costa, R Silva, AF Pereira, CM in NANOMATERIALS, 2021, ISSN: 2079-4991,  Volume: 11, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.3390/nano11123258 P-00V-RST
Abstract The urgent need to reduce the consumption of fossil fuels drives the demand for renewable energy and has been attracting the interest of the scientific community to develop materials with improved energy storage properties. We propose a sustainable route to produce nanoporous carbon materials with a high-surface area from commercial graphite using a dry ball-milling procedure through a systematic study of the effects of dry ball-milling conditions on the properties of the modified carbons. The microstructure and morphology of the dry ball-milled graphite/carbon composites are characterized by BET (Brunauer-Emmett-Teller) analysis, SEM (scanning electron microscopy), ATR-FTIR (attenuated total reflectance-Fourier transform infrared spectroscopy) and Raman spectroscopy. As both the electrode and electrolyte play a significant role in any electrochemical energy storage device, the gravimetric capacitance was measured for ball-milled material/glassy carbon (GC) composite electrodes in contact with a deep eutectic solvent (DES) containing choline chloride and ethylene glycol as hydrogen bond donor (HBD) in a 1:2 molar ratio. Electrochemical stability was tracked by measuring charge/discharge curves. Carbons with different specific surface areas were tested and the relationship between the calculated capacitance and the surface treatment method was established. A five-fold increase in gravimetric capacitance, 25.27 F center dot g(-1) (G40) against 5.45 F center dot g(-1), was found for commercial graphene in contact with DES. Optimal milling time to achieve a higher surface area was also established.

4. Characterization and electrochemical studies of MWCNTs decorated with Ag nanoparticles through pulse reversed current electrodeposition using a deep eutectic solvent for energy storage applications, Brandao, ATSC Rosoiu, S; Costa, R Lazar, OA; Silva, AF Anicai, L; Pereira, CM Enachescu, M in JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 2021, ISSN: 2238-7854,  Volume: 15, 
Article,  Indexed in: crossref, wos  DOI: 10.1016/j.jmrt.2021.08.031 P-00V-S7M
Abstract Carbon nanotubes (CNTs) are receiving special attention due to their remarkable thermal, electrical, and mechanical properties. The present work reports an innovative synthesis procedure to decorate MWCNTs with silver nanoparticles (Ag-NPs) via pulsed reverse deposition technique using a deep eutectic solvent (DES) based on choline chloride and glycerol as an electrolyte at room temperature, not requiring any previous surface modification of MWCNTs. MWCNTs decorated with Ag-NPs disclose a significant enhancement of their electrochemical performance as demonstrated by the increase of electrode stability and specific capacitance. Electrochemical characterization of the composite material was performed using cyclic voltammetry and charge/discharge curves, achieving a specific capacitance up to 28.50 F. g-1, against 4.70 F. g-1 for the commercial MWCNTs in a three-electrode system. Retention of the specific capacitance up to 99% for the Ag-MWCNTs composites compared with a value of 78% for electrodes modified with commercial MWCNTs. The Ag-MWCNTs composites were characterized through SEM/EDX analysis, ultrahighresolution STEM, in which the Z - Contrast image was collected, and Raman analysis to prove the successful attachment of the Ag-NPs to the MWCNTs surface. AFM was performed to evaluate the conductivity of the composites. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (

5. Ordering and Nonideality of Air-Ionic Liquid Interfaces in Surface Second Harmonic Generation, Costa, R Pereira, CM Silva, AF Brevet, PF; Benichou, E in JOURNAL OF PHYSICAL CHEMISTRY B, 2020, ISSN: 1520-6106,  Volume: 124, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.1021/acs.jpcb.9b12025 P-00S-4T3
Abstract The air-ionic liquid interface for a series of ionic liquids involving imidazolium cations [C(n)mim] with different alkyl chain lengths (n = 2, 4, 6, 8, 10, and 12) and the same [NTf2] imide anion has been studied by polarization-resolved second harmonic generation (SHG). An increase as a function of the alkyl chain length of the orientational parameter reveals the increasing ordering of the air-pure ionic liquid interfaces although it is not possible to disentangle the change in mean tilt angle from a change in the tilt angle probability distribution width. Besides, the study of the air-mixed ([C(12)mim])(x)([C(2)mim])(1-x)[NTf2] ionic liquid interface clearly demonstrates the interfacial nonideality of the mixed ionic liquids. The long alkyl chain cation perturbs the interface as seen from the orientational parameter and displaces the short alkyl chain one for bulk mixture contents as low as 10%. At higher long alkyl chain cation bulk mixture contents, the interface behaves close to a pure long alkyl chain ionic liquid.