Publications

Abstract Molecularly imprinted materials have been used in selective photocatalysis, essentially due to surface properties, possibility of reuse and low cost, that enhance their industrial and economic interest. The molecular imprinting technique allows the development of photocatalysts with selective recognition for a template molecule, used during synthesis, by increasing the surface area caused by selective recognition sites for the template used. In this work the preparation of hollow titania microspheres was merged with the process of generating selectivity for bilirubin in the shell structure by molecular imprinting. Three major synthesis parameters (solvent, temperature and TiO2 precursor) were studied by performing a set of experiments based in a full factorial design. The selected synthesis conditions were mainly dictated by the maximization of the surface area normalized by the thickness of the TiO2 shell and its controllability. The microspheres kept the integrity of the spherical shape while dispersed in the synthesis solvent. The observed imprinting features for the hollow microspheres prepared in the final synthesis conditions included imprinting factors of 3.1 for the binding strength and 1.3 for the capacity, and bilirubin/protoporphirin selectivity factors of 4.0 in terms of binding strength and 9.6 in terms of binding capacity. These features are very promising, especially the high selectivity factors, given the high resemblance between bilirubin and protoporphirin, and also due to the threat that the somewhat aggressive treatment for the silica core removal, might eventually pose to the templated microstructure of the shell. In fact, the photocatalytic selectivity of the imprinted microspheres was confirmed, with the observation of up to two-fold faster rates of bilirubin consumption vs. protoporphyrin consumption. © 2020

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).

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.

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 (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Abstract <jats:p>Relative humidity monitorization is of extreme importance on scientific and industrial applications, and fiber optics-based sensors may provide solutions where other types of sensors have limitations. In this work, fiber optics’ sensors were fabricated by combining Long-Period Fiber Gratings with three different humidity-responding polymers, namely Poly(vinyl alcohol), Poly(ethylene glycol) and Hydromed™ D4. The performance of the multiple sensors was experimentally tested and crossed with numerical simulations, which provide a comparison with the expected response given the optical properties of the materials.</jats:p>

Abstract <jats:p>Over the years, the food industry’s concern to provide safe food that does not cause harm or illness to consumers has increased. The growing demand for the detection of compounds that can contaminate food is increasingly important. Hydrogen peroxide is frequently used as a substance to control the growth of microorganisms in milk, thus increasing its shelf life. Here, a strategy is presented for the detection of hydrogen peroxide as a milk adulterant, using a single shot membrane sensor. The lowest concentration measured with this technique was 0.002% w/w of H2O2 in semi-fat milk.</jats:p>

Abstract <jats:p>Current therapeutic protocols for the treatment of HIV infection consist of the combination of diverse anti-retroviral drugs in order to reduce the selection of resistant mutants and to allow for the use of lower doses of each single agent to reduce toxicity. However, avoiding drugs interactions and patient compliance are issues not fully accomplished so far. Pursuing on our investigation on potential anti HIV multi-target agents we have designed and synthesized a small library of biphenylhydrazo 4-arylthiazoles derivatives and evaluated to investigate the ability of the new derivatives to simultaneously inhibit both associated functions of HIV reverse transcriptase. All compounds were active towards the two functions, although at different concentrations. The substitution pattern on the biphenyl moiety appears relevant to determine the activity. In particular, compound 2-{3-[(2-{4-[4-(hydroxynitroso)phenyl]-1,3-thiazol-2-yl} hydrazin-1-ylidene) methyl]-4-methoxyphenyl} benzamide bromide (EMAC2063) was the most potent towards RNaseH (IC50 = 4.5 mM)- and RDDP (IC50 = 8.0 mM) HIV RT-associated functions.</jats:p>

Abstract Fuel cells are emerging devices as clean and renewable energy sources, provided their efficiency is increased. In this work, we prepared nanocomposites based on multiwalled carbon nanotubes (MWNTs) and transition metal dichalcogenides (TMDs), namely WS2 and MoS2, and evaluated their performance as electrocatalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), relevant to fuel cells. The one- and two-dimensional (1D and 2D) building blocks were initially exfoliated and non-covalently functionalized by surfactants of opposite charge in aqueous media (tetradecyltrimethylammonium bromide, TTAB, for the nanotubes and sodium cholate, SC, for the dichalcogenides), and thereafter, the three-dimensional (3D) MoS2@MWNT and WS2@MWNT composites were assembled via surfactant-mediated electrostatic interactions. The nanocomposites were characterized by scanning electron microscopy (SEM) and structural differences were found. WS2@MWNT and MoS2@MWNT show moderate ORR performance with potential onsets of 0.71 and 0.73 V vs. RHE respectively, and diffusion-limiting current densities of -1.87 and -2.74 mA center dot cm(-2), respectively. Both materials present, however, better tolerance to methanol crossover when compared to Pt/C and good stability. Regarding OER performance, MoS2@MWNT exhibits promising results, with eta(10) and j(max) of 0.55 V and 17.96 mA center dot cm(-2), respectively. The fabrication method presented here is cost-effective, robust and versatile, opening the doors for the optimization of electrocatalysts' performance.

Abstract Aqueous surfactant/polymermixtures form colloidal structures of great fundamental interest and practical relevance, such as nanostructured hydrogels for biomedical and pharmaceutical uses. In this work, we investigated the phase behavior, structure and cytotoxicity of mixtures of a double-tailed lysine-based surfactant, 16Lys12, and two hydroxyethyl cellulose (HEC) derivatives, JR400 and LM200. The surfactant, S-, is anionic and self-assembles into tubular structures at room temperature, undergoing a tubule-to-vesicle transition at approximate to 44 degrees C. JR400 is a cationic homopolymer, P+, longer and more densely charged than LM200, a closely related hydrophobically modified polymer, HMP+. Electrostatic and hydrophobic interactions play a crucial role in the observed phase behavior and resulting colloidal structures. Both the S-/P+ and S-/HMP+ mixtures show three main phase regions: at surfactant charge excess, bluish dispersions containing mixed polymer/tubular aggregates and, upon heating, polymer/vesicle clusters; a white precipitate near charge equimolarity, coexisting with either a solution or a gel; and highly viscous hydrogels, at polymer charge excess. In the bluish dispersions, the S-/P+ and S-/HMP+ systems show relevant differences in thermal behavior and type of aggregates present. Cryogenic scanning electron microscopy shows that the hydrogels consist of honeycomb-like structure of surfactant and polymer moieties. Cytotoxicity assays in the bluish dispersion region indicate good levels of cytocompatibility for both types of surfactant/polymer systems. Overall, these dispersions and hydrogels can be further explored for the encapsulation and temperature-triggered release of biomolecules.

Abstract Most applications of nanocarbons, such as carbon nanotubes and graphene, require that they are well-separated and well-dispersed in a liquid phase. Intensive efforts have been put on exfoliating and dispersing nanocarbons in aqueous solvents, typically using amphiphilic dispersants and sonication/centrifugation procedures, alongside a drive to fundamentally understand and rationally optimize these processes. Herein, we employed a robust method to separate and disperse multiwalled carbon nanotubes (MWNTs), and graphene nanoplatelets (GnPs) either from bulk graphite or from pre-formed GnP powders, using rigorously controlled processing conditions. An ionic (sodium cholate) and a nonionic (Triton X-100) surfactant were used as dispersants. Our aim was to determine high-precision dispersibility curves (concentration of dispersed nanomaterial versus initial surfactant concentration) for the different nanocarbon/dispersant systems, characterize morphologically the dispersed particles and compare the mechanisms of exfoliation of 1D and 2D nanocarbons at molecular level. Typically bell-shaped dispersibility curves with a plateau were obtained, and from the latter several quantitative metrics were extracted that permitted reliable comparisons between nanocarbon/surfactant systems. Scanning electron and atomic force microscopies allowed to characterize the suspended particles in the as-obtained dispersions, namely the MWNT bundle width and GnP dimensions (mean lateral size and layer number). Under fixed conditions (in particular, delivered energy per carbon mass), MWNTs are dispersed in much higher yields, by two orders of magnitude, than GnPs. However, and significantly, a master curve for the dispersibility was obtained, implying that common fundamental features underpin the dispersing process, irrespective of nanocarbon (1D or 2D) or surfactant (ionic or nonionic) types.