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Cordeiro, T, Santos AFM, Nunes G, Cunha G, Sotomayor JC, Fonseca IM, Florence Danède, Dias CJ, Cardoso MM, Correia NT, Viciosa TM, Dionísio M.  2016.  Accessing the Physical State and Molecular Mobility of Naproxen Confined to Nanoporous Silica Matrixes. The Journal of Physical Chemistry C. 120:14390-14401., Number 26 AbstractWebsite

The pharmaceutical drug naproxen was loaded in three different silica hosts with pore diameters of 2.4 (MCM), 3.2 (MCM), and 5.9 nm (SBA), respectively: napMCM\_2.4 nm, napMCM\_3.2 nm, and napSBA\_5.9 nm. To access the guest physical state in the prepared composites, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and attenuated total reflectance Fourier transform infrared spectroscopy were used. The different techniques provided complementary information on a molecular population that was revealed to be distributed among different environments, namely the pore core, the inner pore wall, and the outer surface. It was found that naproxen is semicrystalline in the higher pore size matrix being able to crystallize inside pores; after melting it undergoes full amorphization. In the case of the lower pore size matrix, naproxen crystallizes outside pores due to an excess of filling while most of the remaining fraction is incorporated inside the pores as amorphous. Crystallinity in these two composites was observed by the emergence of the Bragg peaks in the XRD analysis, whereas for napMCM\_3.2 nm only the amorphous halo was detected. The latter only exhibits the step due to the glass transition by DSC remaining stable as amorphous at least for 12 months. The glass transition in the three composites is abnormally broad, shifting to higher temperatures as the pore size decreases, coherent with the slowing down of molecular mobility as probed by dielectric relaxation spectroscopy. For napSBA\_5.9 nm the dielectric response was deconvoluted in two processes: a hindered surface (S-) process due to molecules interacting with the inner pore wall and a faster α-relaxation associated with the dynamic glass transition due to molecules relaxing in the pore core, which seems a manifestation of true confinement effects. The drug incorporation inside a nanoporous matrix, mainly in 3.2 nm pores, was revealed to be a suitable strategy to stabilize the highly crystallizable drug naproxen in the amorphous/supercooled state and to control its release from the silica matrix, allowing full delivery after 90 min in basic media.

Godino-Ojer, M, Matos I, Bernardo M, Carvalho R, G.P. Soares OS, Durán-Valle C, Fonseca IM, Mayoral PE.  2020.  Acidic porous carbons involved in the green and selective synthesis of benzodiazepines. Catalysis Today. 357:64-73. AbstractWebsite

Eco-sustainable and recyclable porous carbons are reported as metal-free catalysts for the synthesis of benzodiazepines for the first time. The porous carbons were able to efficiently catalyse the synthesis of benzodiazepine 1 from o-phenylendiamine 2 and acetone 3 under mild conditions. Both acidic functions and the porosity of the catalysts were determinant features. High conversion values were obtained when using HNO3 oxidized carbons. The highest selectivity to benzodiazepine 1 was obtained in the presence of the most microporous catalyst N-N, which is indicative of the great influence of porous properties. Stronger acid sites and high microporosity of the carbon treated with H2SO4 yield benzodiazepine 1 with total selectivity.

Dias, D, Bernardo M, Lapa N, Pinto F, Matos I, Fonseca I.  2018.  Activated carbons from the Co-pyrolysis of rice wastes for Cr(III) removal. Chemical Engineering Transactions. 65:601-606.
Dias, D, Bernardo M, Matos I, Fonseca I, Pinto F, Lapa N.  2020.  Activation of co-pyrolysis chars from rice wastes to improve the removal of Cr3+ from simulated and real industrial wastewaters. Journal of Cleaner Production. 267:121993. AbstractWebsite

Chromium is one of the most important raw materials for the European Union. Adsorption has become an important process for the recovery of metals from wastewaters, which has led to a demand for low-cost and eco-friendly adsorbents. The objective of this work was to use new and renewable carbon-based adsorbents from rice wastes in the removal/recovery of Cr(III) from synthetic and real wastewaters. Rice wastes were submitted to co-pyrolysis and the resulting char was optimized through physical and/or chemical activations/treatments. A commercial activated carbon was used for comparison purposes. All adsorbents were characterized (including an ecotoxicity test for the char precursor) and submitted to Cr(III) removal assays from a synthetic solution, in which two solid/liquid ratios (S/L) were tested (5 and 10 g/L). The CO2 activated carbon at a S/L = 5 g/L was the biomass-derived adsorbent that performed better, obtaining a maximum Cr(III) uptake capacity of 9.23 mg/g comparable to the one obtained by the commercial adsorbent at the same S/L (9.80 mg/g). The good results on this biomass-derived carbon were due to the effective volatile matter removal during the activation (from 22.7 to 4.25% w/w), which increased both surface area (from <5.0 to 325 m2/g) and ash content (from 30.0 to 40.4% w/w), allowing an increase in Cr(III) removal due to ion exchange mechanism and porosity development. The best adsorbent, under optimized conditions, was also applied to a chromium rich industrial wastewater. The results obtained in this real case application demonstrated a competition effect due to the presence of other ions.

Godinho, D, Dias D, Bernardo M, Lapa N, Fonseca I, Lopes H, Pinto F.  2017.  Adding value to gasification and co-pyrolysis chars as removal agents of Cr3+. Journal of Hazardous Materials. 321:173-182. AbstractWebsite

The present work aims to assess the efficiency of chars, obtained from the gasification and co-pyrolysis of rice wastes, as adsorbents of Cr3+ from aqueous solution. GC and PC chars, produced in the gasification and co-pyrolysis, respectively, of rice husk and polyethylene were studied. Cr3+ removal assays were optimised for the initial pH value, adsorbent mass, contact time and Cr3+ initial concentration. GC showed a better performance than PC with about 100% Cr3+ removal, due to the pH increase that caused Cr precipitation. Under pH conditions in which the adsorption prevailed (pH<5.5), GC presented the highest uptake capacity (21.1mg Cr3+ g−1 char) for the following initial conditions: 50mg Cr3+ L−1; pH 5; contact time: 24h;L/S ratio: 1000mLg−1. The pseudo-second order kinetic model showed the best adjustment to GC experimental data. Both the first and second order kinetic models fitted well to PC experimental data. The ion exchange was the dominant phenomenon on the Cr3+ adsorption by GC sample. Also, this char significantly reduced the ecotoxicity of Cr3+ solutions for the bacterium Vibrio fischeri. GC char proved to be an efficient material to remove Cr3+ from aqueous solution, without the need for further activation.

Dias, D, Lapa N, Bernardo M, Ribeiro W, Matos I, Fonseca I, Pinto F.  2018.  Cr(III) removal from synthetic and industrial wastewaters by using co-gasification chars of rice waste streams. Bioresource Technology. 266:139-150. AbstractWebsite

Blends of rice waste streams were submitted to co-gasification assays. The resulting chars (G1C and G2C) were characterized and used in Cr(III) removal assays from a synthetic solution. A Commercial Activated Carbon (CAC) was used for comparison purposes. The chars were non-porous materials mainly composed by ashes (68.3–92.6% w/w). The influences of adsorbent loading (solid/liquid ratio – S/L) and initial pH in Cr(III) removal were tested. G2C at a S/L of 5 mg L−1 and an initial pH of 4.50 presented an uptake capacity significantly higher than CAC (7.29 and 2.59 mg g−1, respectively). G2C was used in Cr(III) removal assays from an industrial wastewater with Cr(III) concentrations of 50, 100 and 200 mg L−1. Cr(III) removal by precipitation (uptake capacity ranging from 11.1 to 14.9 mg g−1) was more effective in G2C, while adsorption (uptake capacity of 16.1 mg g−1) was the main removal mechanism in CAC.

Godino-Ojer, M, Milla-Diez L, Matos I, Durán-Valle CJ, Bernardo M, Fonseca IM, Pérez Mayoral E.  2018.  Enhanced Catalytic Properties of Carbon supported Zirconia and Sulfated Zirconia for the Green Synthesis of Benzodiazepines. ChemCatChem. 10:5215-5223., Number 22 AbstractWebsite

Abstract This work reports for the first time a new series of promising porous catalytic carbon materials, functionalized with Lewis and Brønsted acid sites useful in the green synthesis of 2,3-dihydro-1H-1,5-benzodiazepine – nitrogen heterocyclic compounds. Benzodiazepines and derivatives are fine chemicals exhibiting interesting therapeutic properties. Carbon materials have been barely investigated in the synthesis of this type of compounds. Two commercial carbon materials were selected exhibiting different textural properties: i) Norit RX3 (N) as microporous sample and ii) mesoporous xerogel (X), both used as supports of ZrO2 (Zr) and ZrO2/SO42− (SZr). The supported SZr led to higher conversion values and selectivities to the target benzodiazepine. Both chemical and textural properties influenced significantly the catalytic performance. Particularly relevant are the results concerning the non-sulfated samples, NZr and XZr, that were able to catalyze the reaction leading to the target benzodiazepine with high selectivity (up to 80 %; 2 h). These results indicated an important role of the carbon own surface functional groups, avoiding the use of H2SO4. Even very low amounts of SZr supported on carbon reveal high activity and selectivity. Therefore, the carbon materials herein reported can be considered an efficient and sustainable alternative bifunctional catalysts for the benzodiazepine synthesis.

Fernandes, MJ, Moreira MM, Paíga P, Dias D, Bernardo M, Carvalho M, Lapa N, Fonseca I, Morais S, Figueiredo S, Delerue-Matos C.  2019.  Evaluation of the adsorption potential of biochars prepared from forest and agri-food wastes for the removal of fluoxetine. Bioresource Technology. 292:121973. AbstractWebsite

Twelve biochars from forest and agri-food wastes (pruning of Quercus ilex, Eucalyptus grandis, Pinus pinaster, Quercus suber, Malus pumila, Prunus spinosa, Cydonia oblonga, Eriobotrya japonica, Juglans regia, Actinidia deliciosa, Citrus sinensis and Vitis vinifera) were investigated as potential low-cost and renewable adsorbents for removal of a commonly used pharmaceutical, fluoxetine. Preliminary adsorption experiments allowed to select the most promising adsorbents, Quercus ilex, Cydonia oblonga, Eucalyptus, Juglans regia and Vitis vinifera pruning material. They were characterized by proximate, elemental and mineral analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy, determination of specific surface area and pH at the point of zero charge. Batch and equilibrium studies were performed, and the influence of pH was evaluated. The equilibrium was reached in less than 15 min in all systems. The maximum adsorption capacity obtained was 6.41 mg/g for the Eucalyptus biochar, which also demonstrated a good behavior in continuous mode (packed column).

Inocêncio, S, Cordeiro T, Matos I, Florence Danède, Sotomayor JC, Fonseca IM, Correia NT, Corvo MC, Dionísio M.  2021.  Ibuprofen incorporated into unmodified and modified mesoporous silica: From matrix synthesis to drug release. Microporous and Mesoporous Materials. 310:110541. AbstractWebsite

Aiming to rationalize the release profile of an incorporated pharmaceutical drug in terms of its mobility, driven by guest-host interactions, the poorly water-soluble ibuprofen drug was loaded in a mesoporous inorganic silica matrix with unmodified (MCM-41) and modified surface (MCM-41sil) by post-synthesis silylation, both having pore sizes   3 nm. The single calorimetric detection of a broad glass transition step for both ibuprofen composites indicates full drug amorphization, confirmed by the only appearance of an amorphous halo in the powder XRD patterns. Moreover, a gradient profile is disclosed by the heat flux derivative plot in the glass transition, in coherence with the thermogravimetric profile that shows a multi-step decomposition trace for confined ibuprofen in these matrixes. While identical guest dynamics, as probed by dielectric relaxation spectroscopy, were found in both dehydrated composites, a significant molecular population with faster relaxation exists in the hydrated state for the drug inside the unmodified matrix. This was rationalized as the concurrence of true confinement effects, which manifest under nanometer dimensions, and greater water affinity of the unmodified matrix, forcing the drug molecules to be placed mostly in the pore core. Finite size effects are also felt in both dehydrated composites, however guest-host interactions give origin to a dominant population with slowed down mobility that governs the overall guest dynamics. In spite of an inferior number of active sites for drug adsorption in the silylated matrix, a faster ibuprofen delivery in phosphate buffer (pH = 6.8) was observed when the drug is released from unmodified MCM-41 in the hydrated state. Therefore, our results suggest that a relevant role is played by water molecules, which impair a strong guest adsorption in the host surface more efficiently than the limited surface modification, influence the higher ratio of a faster population in the pore core and facilitate the diffusion of the aqueous releasing media inside pores.

Ferreira, RC, Dias D, Fonseca I, Bernardo M, Pimenta JLCW, Lapa N, de Barros MASD.  2020.  Multi-component adsorption study by using bone char: modelling and removal mechanisms. Environmental Technology. :1-16.: Taylor & Francis AbstractWebsite
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Faria, P, Duarte P, Barbosa D, Ferreira I.  2017.  New composite of natural hydraulic lime mortar with graphene oxide. Construction and Building Materials. 156:1150-1157. AbstractWebsite

Recent studies show the incorporation of graphene oxide (GO) in cement composites. But these composites are frequently incompatible with original materials for building rehabilitation. To overcome this limitation, natural hydraulic lime mortars were used as matrix, and the influence of GO percentage and type of mixing was investigated. The influence on the microstructure, mechanical and physical properties was assessed. The best results were obtained with dispersed GO at concentrations of 0.05% and 0.1%. A slight improvement of mechanical and physical characteristics was achieved. This could lead to new mortars with improved properties that can be used for building rehabilitation.

Figueira, J, Loureiro J, Marques J, Bianchi C, Duarte P, Ruoho M, Tittonen I, Ferreira I.  2017.  Optimization of Cuprous Oxides Thin Films to be used as Thermoelectric Touch Detectors. ACS Applied Materials & Interfaces. 9:6520-6529., Number 7 AbstractWebsite

The electronic and optical properties of p-type copper oxides (CO) strongly depend on the production technique as it influences the obtained phases: cuprous oxide (Cu2O) or cupric oxide (CuO), the most common ones. Cu films deposited by thermal evaporation have been annealed in air atmosphere, with temperature between 225 and 375 °C and time between 1 and 4 h. The resultant CO films have been studied to understand the influence of processing parameters in the thermoelectric, electrical, optical, morphological, and structural properties. Films with a Cu2O single phase are formed when annealing at 225 °C, while CuO single phase films can be obtained at 375 °C. In between, both phases are obtained in proportions that depend on the film thickness and annealing time. The positive sign of the Seebeck coefficient (S), measured at room temperature (RT), confirms the p-type behavior of both oxides, showing values up to 1.2 mV·°C–1 and conductivity up to 2.9 (Ω·m)−1. A simple detector using Cu2O have been fabricated and tested with fast finger touch events.

Dias, D, Lapa N, Bernardo M, Godinho D, Fonseca I, Miranda M, Pinto F, Lemos F.  2017.  Properties of chars from the gasification and pyrolysis of rice waste streams towards their valorisation as adsorbent materials. Waste Management. 65:186-194. AbstractWebsite

Rice straw (RS), rice husk (RH) and polyethylene (PE) were blended and submitted to gasification and pyrolysis processes. The chars obtained were submitted to textural, chemical, and ecotoxic characterisations, towards their possible valorisation. Gasification chars were mainly composed of ashes (73.4–89.8wt%), while pyrolysis chars were mainly composed of carbon (53.0–57.6wt%). Silicon (Si) was the major mineral element in all chars followed by alkaline and alkaline-earth metal species (AAEMs). In the pyrolysis chars, titanium (Ti) was also a major element, as the feedstock blends contained high fractions of PE which was the main source of Ti. Gasification chars showed higher surface areas (26.9–62.9m2g−1) and some microporosity, attributed to porous silica. On the contrary, pyrolysis chars did not present a porous matrix, mainly due to their high volatile matter content. The gasification bed char produced with 100% RH, at 850°C, with O2 as gasification agent, was selected for further characterization. This char presented the higher potential to be valorised as adsorbent material (higher surface area, higher content of metal cations with exchangeable capacity, and lowest concentrations of toxic heavy metals). The char was submitted to an aqueous leaching test to assess the mobility of chemical species and the ecotoxic level for V. fischeri. It was observed that metallic elements were significantly retained in the char, which was attributed mainly to its alkaline character. This alkaline condition promoted some ecotoxicity level on the char eluate that was eliminated after the pH correction.

Godinho, D, Nogueira M, Bernardo M, Dias D, Lapa N, Fonseca I, Pinto F.  2019.  Recovery of Cr(III) by using chars from the co-gasification of agriculture and forestry wastes, Aug. Environmental Science and Pollution Research. 26:22723–22735., Number 22 AbstractWebsite

The aim of the present work was to assess the efficiency of biochars obtained from the co-gasification of blends of rice huskþinspace}+þinspace}corn cob (biochar 50CC) and rice huskþinspace}+þinspace}eucalyptus stumps (biochar 50ES), as potential renewable low-cost adsorbents for Cr(III) recovery from wastewaters. The two gasification biochars presented a weak porous structure (ABETþinspace}=þinspace}63–144 m2 g−1), but a strong alkaline character, promoted by a high content of mineral matter (59.8{%} w/w of ashes for 50CC biochar and 81.9{%} w/w for 50ES biochar). The biochars were used for Cr(III) recovery from synthetic solutions by varying the initial pH value (3, 4, and 5), liquid/solid (L/S) ratio (100–500 mL g−1), contact time (1–120 h), and initial Cr(III) concentration (10–150 mg L−1). High Cr(III) removal percentages (around 100{%}) were obtained for both biochars, due to Cr precipitation, at low L/S ratios (100 and 200 mL g−1), for the initial pH 5 and initial Cr concentration of 50 mg L−1. Under the experimental conditions in which other removal mechanisms rather than precipitation occurred, a higher removal percentage (49.9{%}) and the highest uptake capacity (6.87 mg g−1) were registered for 50CC biochar. In the equilibrium, 50ES biochar presented a Cr(III) removal percentage of 27{%} with a maximum uptake capacity of 2.58 mg g−1. The better performance on Cr(III) recovery for the biochar 50CC was attributed to its better textural properties, as well as its higher cation exchange capacity.

Cordeiro, T, Castiñeira C, Mendes D, Florence Danède, Sotomayor J, Fonseca IM, Gomes da Silva M, Paiva A, Barreiros S, Cardoso MM, Viciosa MT, Correia NT, Dionisio M.  2017.  Stabilizing Unstable Amorphous Menthol through Inclusion in Mesoporous Silica Hosts. Molecular Pharmaceutics. 14:3164-3177., Number 9 AbstractWebsite
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Bernardo, MMS, Madeira CAC, dos Santos Nunes NCL, Dias DACM, Godinho DMB, de Jesus Pinto MF, do Nascimento Matos IAM, Carvalho APB, de Figueiredo Ligeiro Fonseca IM.  2017.  Study of the removal mechanism of aquatic emergent pollutants by new bio-based chars, Oct. Environmental Science and Pollution Research. 24:22698–22708., Number 28 AbstractWebsite

This work is dedicated to study the potential application of char byproducts obtained in the gasification of rice husk (RG char) and rice husk blended with corn cob (RCG char) as removal agents of two emergent aquatic contaminants: tetracycline and caffeine. The chars presented high ash contents (59.5–81.5{%}), being their mineral content mainly composed of silicon (as silica) and potassium. The samples presented a strong basic character, which was related to its higher mineral oxides content. RCG char presented better textural properties with a higher apparent surface area (144 m2 g−1) and higher micropore content (V micro = 0.05 cm3 g−1). The alkaline character of both chars promoted high ecotoxicity levels on their aqueous eluates; however, the ecotoxic behaviour was eliminated after pH correction. Adsorption experiments showed that RG char presented higher uptake capacity for both tetracycline (12.9 mg g−1) and caffeine (8.0 mg g−1), indicating that textural properties did not play a major role in the adsorption process. For tetracycline, the underlying adsorption mechanism was complexation or ion exchange reactions with the mineral elements of chars. The higher affinity of RG char to caffeine was associated with the higher alkaline character presented by this char.

Lourenço, SC, Torres CAV, Nunes D, Duarte P, Freitas F, Reis MAM, Fortunato E, Moldão-Martins M, da Costa LB, Alves VD.  2017.  Using a bacterial fucose-rich polysaccharide as encapsulation material of bioactive compounds. International Journal of Biological Macromolecules. 104:1099-1106. AbstractWebsite

The potential of a bacterial exopolysaccharide named FucoPol, produced by the bacterium Enterobacter A47, as encapsulation matrix was explored. Spherical capsules with a smooth surface were produced by spray drying. The obtained microcapsules had average diameters ranging from 0.5 to 26.7μm and presented thin walls (thickness from 222 to 1094nm). The capsules were loaded with two bioactive compounds: gallic acid (GA) and oregano essential oil (OEO). Both bioactive materials were encapsulated in FucoPol particles, retaining their antioxidant activity after the drying process. Release studies showed that GA release in simulated gastric and intestinal fluids was faster than that of OEO, envisaging that the latter had established stronger interactions with the polymer matrix. These results suggest that FucoPol has a good potential for use as encapsulating material of bioactive compounds for application in several areas, including food, cosmetic or pharmaceutical products.

Bianchi, C, Ferreira LM, Loureiro J, Rodrigues A, Duarte P, Baptista AC, Ferreira IM.  2016.  Vanadium Pentoxide Alloyed with Graphite for Thin-Film Thermal Sensors, Mar. Journal of Electronic Materials. 45:1987–1991., Number 3 AbstractWebsite

The thermoelectric (TE) properties of vanadium pentoxide (V2O5) alloyed with graphite (G) were studied as a function of its incorporation percentage. Variable weight percentages of graphite powder (0–50{%}) were added to V2O5 powder and their mixtures were evaporated by a thermal evaporation technique to form thin films with a thickness in the range of 30–80 nm. In the infrared wavelength region, the transmittance of the obtained films increased as the G percentage was increased, while in the visible range, it decreased with G up to 10{%}. The TE properties were improved when G was in the range of 10–30{%}, while it decreased for the other percentages: Seebeck coefficient (S) changed from 0.6 mV/K to 0.9 mV/K and was zero with a G of 50{%}; the electrical conductivity varied slightly from 5 ($Ømega$m)−1 to 0.7 ($Ømega$m)−1 while the mobility improved from 0.07 cm2/V s to 1.5 cm2/V s and the respective carrier concentration was reduced, from 1 × 1018 cm−3 to 4 × 1016 cm−3. These films were applied as temperature sensors evaluating the thermovoltage as a function of thermal gradient between two electrodes, in which one was maintained at room temperature.