Publications

Abstract Micro/nanomotors represent a burgeoning field of research featuring small devices capable of autonomous movement in liquid environments through catalytic reactions and/or external stimuli. This review delves into recent advancements in light-driven semiconductor-based micro/nanomotors (LDSM), focusing on optimized syntheses, enhanced motion mechanisms, and emerging applications in the environmental and biomedical domains. The survey commences with a theoretical introduction to micromotors and their propulsion mechanisms, followed by an exploration of commonly studied LDSM, emphasizing their advantages. Critical properties affecting propulsion, such as surface features, morphology, and size, are presented alongside discussions on external conditions related to light sources and intensity, which are crucial for optimizing the propulsion speed. Each property is accompanied by a theoretical background and conclusions drawn up to 2018. The review further investigates recent adaptations of LDSM, uncovering underlying mechanisms and associated benefits. A brief discussion is included on potential synergistic effects between different external conditions, aiming to enhance efficiency-a relatively underexplored topic. In conclusion, the review outlines emerging applications in biomedicine and environmental monitoring/remediation resulting from recent LDSM research, highlighting the growing significance of this field. The comprehensive exploration of LDSM advancements provides valuable insights for researchers and practitioners seeking to leverage these innovative micro/nanomotors in diverse applications.

Abstract Purpose Pejao Mining Complex locates in Castelo de Paiva municipality and, until its closure in 1994, was one of the most important coal mines in the Douro Coalfield. This work aims to study the presence, quantify, and evaluate the dissemination of mercury (Hg), a potentially toxic element (PTE) of major public health concern by the World Health Organization (WHO), from a waste pile affected by coal fires.Materials and methods Samples from areas affected and unaffected by the combustion and from surrounding soil were collected from Fojo waste pile region. First, the Hg pseudo-total concentration was estimated for all collected samples by soil microwave-assisted digestion with aqua regia (USEPA 3051A). Then, a sequential extraction procedure (SEP), the USEPA 3200, was applied for Hg fractionation and speciation aiming to evaluate Hg mobility and bioavailability to surrounding ecosystems.Results and discussion The results obtained showed a Hg enrichment in soil samples when compared to Portuguese and international reference values for soils. Relatively to the Hg availability and mobility, although it predominates in the semi-mobile fraction, the waste pile materials exposed to combustion showed a concerning increase of Hg levels in the mobile fraction that contains the more labile Hg species, being a major source of environmental contamination by Hg.Conclusions This study allowed to conclude that combustion of mining residues increased Hg mobility, toxicity, and bioavailability, increasing the contamination potential of the coal waste pile. The methodology applied in this work can be replicated in other abandoned mines to monitor, control, and/or mitigate the Hg environmental impact in the surrounding soils and waters.

Abstract The occurrence of drought in soils, particularly in those contaminated by metals, poses a current threat to crops, as these factors can interact and induce unique stress responses. Therefore, this study mainly focused on understanding the crosstalk between drought and copper (Cu) stress in the physiology of the barley (Hordeum vulgare L.) plant. Using a bifactorial experimental design, seedlings were grown in a natural soil under the following treatments: plants continuously irrigated in uncontaminated soil for 14 days (control); plants continuously irrigated in Cu-contaminated soil (115 mg Cu kg-1) for 14 days (Cu); plants only irrigated during the initials 7 days of growth in uncontaminated soil (drought); plants co-exposed to Cu and drought (combined). After 14 days of growth, the results revealed that drought prevented Cu bioaccumulation in barley roots, which were still severely affected by the metal, both individually and in combination with the water deficit. Furthermore, individual and combined exposure to these stressors resulted in impaired photosynthetic performance in barley plants. Despite the increased activation of enzymatic and non-enzymatic antioxidant defence mechanisms, particularly in the green organs, the plants co-exposed to both stress factors still showed higher oxidative damage, severely impacting biomass production.

Abstract Throughout their life cycle, plants are subjected to a variety of environmental constraints, including abiotic stresses. The present study aimed at characterizing the responses of the two tomato cultivars Gold Nugget (GN) and Purple Calabash (PC) exposed to a combination of nickel (Ni) and drought. The following hypotheses were pursued: (i) the activation of responses to one stressor eases further adjustments to a second stressor; and (ii) the two tomato cultivars are differentially susceptible to drought and heavy metal-stress. Besides biometrical evaluations, the distribution of Ni in tissues and the redox homeostasis in both cultivars were compared in response to Ni-stress, polyethylene glycol (PEG)-induced drought, and to their combination. Regarding single stresses, Ni caused more harmful effects to plants than PEG-induced drought, in terms of growth inhibition and production of reactive oxygen species. Ni was mostly accumulated in the roots. The GN cultivar promptly activated antioxidant defenses under Ni-stress, while, in PC, such antioxidants were more strongly induced under combined stress. Stress co-exposure led to a drastic proline accumulation, resembling a signal of stress sensitivity. Overall, the GN cultivar seemed to be less susceptible to the combined stress than PC, as it could activate stronger antioxidant defenses under single Ni toxicity, possibly easing further adjustments demanded by the later co-exposure to drought. This study showed that the two cultivars of the same species had different levels of perception and responsiveness to Ni-induced stress, which translated into different susceptibilities to the combined exposure to PEG-induced drought. [GRAPHICS] .

Abstract Currently, copper is approved as an active substance among plant protection products and is considered effective against more than 50 different diseases in different crops, conventional and organic. Tomato has been cultivated for centuries, but many fungal diseases still affect it, making it necessary to control them through antifungal agents, such as copper, making it the primary form of fungal control in organic farming systems (OFS). The objective of this work was to determine whether exogenous copper applications can affect AOX mechanisms and nitrogen use efficiency in tomato plant grown in OFS. For this purpose, plants were sprayed with 'Bordeaux' mixture (SP). In addition, two sets of plants were each treated with 8 mg/L copper in the root substrate (S). Subsequently, one of these groups was also sprayed with a solution of 'Bordeaux' mixture (SSP). Leaves and roots were used to determine NR, GS and GDH activities, as well as proline, H2O2 and AsA levels. The data gathered show that even small amounts of copper in the rhizosphere and copper spraying can lead to stress responses in tomato, with increases in total ascorbate of up to 70% and a decrease in GS activity down to 49%, suggesting that excess copper application could be potentially harmful in horticultural production by OFS.

Abstract In the last 60 years, auxinic herbicides like 2,4-dichlorophenoxyacetic acid (2,4-D) have been among the widest and successful herbicides used in agriculture because it is a selective herbicide that kills dicots and mimics the natural plant phytohormone indol-3-acetic acid (IAA) at the molecular level. In spite of industry attempts to reformulate 2,4-D-based herbicides and reduce their off-target movement, damage has been reported on sensitive plants, like tomato, at low ratesdi. Therefore, it is important to study the responses of such species to such conditions so that yield losses can be avoided or, at least, reduced. It is known that ethylene, abscisic acid (ABA) and reactive oxygen species (ROS) play a central role in 2,4-D toxicity, leading to numerous unbeneficial changes in plant tissues. Yet, how glutathione-related defense-and/or stress-related genes' expressions are affected needs to be more studied. In this study, tomato plants (Solanum lycopersicum L.) were used to determine the expression and participation of the different GST phi class gene family members, plus the plans' antioxidant system, in response to 2,4-D. When tomato plants were root-treated with 2.26 mM 2,4-D for 48 h, H2O2 and O2 & BULL; levels increased in shoots. Contrarily, in roots, 2,4-D did not provoke clear symptoms of oxidative stress, as lipid peroxidation, H2O2 and O2 & BULL; levels decreased. Despite the difference in ROS levels observed in both organs, the exposure of tomato plants to 2,4-D lead to the activation of key antioxidant enzymes in both organs, apart from superoxide dismutase (SOD), whose activity increased only in roots, while ascorbate peroxidase (APX) and catalase (CAT) activities increased in both. Also, tomato plants responded to 2.26 mM 2,4-D by increasing Ascorbate (AsA) levels in both organs while an increase in Glutathione (GSH) was only observed in shoots. The herbicide increased both the synthesis and the regeneration of GSH, as well as its usage to conjugate 2,4-D, as shoot & gamma;-glutamyl-cysteinyl synthetase (& gamma;-ECS), glutathione reductase (GR) and glutathione S-transferase (GST) activities increased. Shoot GST increased activity was due to an increased expression of SlGSTF4 and SlGSTF5, while no SlGSTFs increased their expression in roots. Shoots and roots of tomato plants were differentially affected by 2.26 mM 2,4-D, with 2,4-D detoxification occurring predominantly in leaves, with the specific participation of the GST phi class members SlGSTF4 and SlGSTF5. Also, this study reinforces the notion that the cultivation of tomato in 2,4-D-contaminated soils may result in yield reduction.

Abstract A novel, straightforward, and environmentally friendly direct coupling procedure to immobilize carbohydrates on solid supports is presented. A characterization study showed that all amino groups on solid supports participated in the linkage with a carbohydrate unit, implicating that the surface load can be easily adjusted by tuning the amination coverage of the surface. Most importantly, the integrity of the cyclic conformation of the linked sugar unit was demonstrated, a feature that is critical for most of the possible applications of carbohydrate-functionalized surfaces. Furthermore, carbohydrate-immobilized submicron particles synthesized by the direct coupling method, on which lectin profiling experiments were conducted, validated the successfulness of our simplistic approach.

Abstract The objective of this work was the exploration of low calcination temperature ranges (< 350 degrees C) to obtain molecularly imprinted microspheres (MIM) with a high crystallinity as anatase, in cooperation of an acidic pretreatment aiming at the preservation of the hollow shape and also of the selective binding sites. It was confirmed the possibility of obtaining bilirubin-imprinted crystalline TiO2 microspheres (highly crystalline anatase, as confirmed by XRD) exhibiting higher photocatalytic efficiency associated especially with the hollow shape and calcination at lower temperatures (200 degrees C or 250 degrees C). It was with the calcination temperature of 250 degrees C that the highest photocatalytic efficiency was obtained, under UV irradiation, associated with the highest adsorption selectivity (alpha(K) = 19) and degradation selectivity (alpha(k) = 2.7) observed for the degradation of the template against a closely related analogue compound.

Abstract Optosensing chitosan-based membranes have been applied for the detection of heavy metals, especially in drinking water. The novelty of this study is based on the use of sulphated polysaccharides, in such optosensing membranes, aiming at an improved analytical performance. The sulphated polysaccharides, such as ulvan, fucoidan and chondroitin sulfate, were extracted from by-products and wastes of marine-related activities. The membranes were developed for the analysis of aluminum. The variation in the visible absorbance of the sensor membranes after the contact between the chromophore and the aluminum cation was studied. The membranes containing sulphated polysaccharides showed improved signals when compared to the chitosan-only membrane. As for the detection limits for the membranes containing ulvan, fucoidan and chondroitin sulfate, 0.17 mg L-1, 0.21 mg L-1 and 0.36 mg L-1 were obtained, respectively. The values were much lower than that obtained for the chitosan-only membrane, 0.52 mg L-1, which shows the improvement obtained from the sulphated polysaccharides. The results were obtained with the presence of CTAB in analysis solution, which forms a ternary complex with the aluminum cation and the chromophore. This resulted in an hyperchromic and batochromic shift in the absorption band. When in the presence of this surfactant, the membranes showed lower detection limits and higher selectivity.

Abstract The possibility of generating organically modified hollow TiO2 microspheres via a simple sol-gel synthesis was demonstrated for the first time in this work. A mixture of titania precursors, including an organically modified precursor, was used to obtain methyl-modified hollow TiO2 microspheres selective for bilirubin by the molecular imprinting technique (Methyl-HTM-MIM). Methyl-HTM-MIM were prepared by a sol-gel method using titanium (IV) isopropoxide (TTIP), and methyltitanium triisopropoxide (MTTIP) as precursors. Two ratios of titania precursors were tested (1/6 and 1/30 mol(MTTIP)/mol(TTIP)). With the characterization results obtained by the SEM and ATR-FTIR techniques, it was possible to establish that only the 1/30 mol(MTTIP)/mol(TTIP) ratio allowed for the preparation of hollow spheres with a reasonably homogeneous methylated-TiO2 shell. It was possible to obtain a certain degree of organization of the hybrid network, which increased with calcination temperatures. By adjusting isothermal adsorption models, imprinting parameters were determined, indicating that the new methylated microspheres presented greater selectivity for bilirubin than the totally inorganic hollow TiO2 microspheres. The effectiveness of the molecular imprinting technique was proven for the first time in an organically modified titania material, with imprinting factor values greater than 1.4, corresponding to a significant increase in the maximum adsorption capacity of the template represented by the molecularly imprinted microspheres. In summary, the results obtained with the new methyl-HTM-MIM open the possibility of exploring the application of these microspheres for selective sorption (separation or sensing, for example) or perhaps even for selective photocatalysis, particularly for the degradation of organic compounds.