Publications

Abstract The present work reports an experimental study aiming to determine several thermodynamic properties of fusion and sublimation of the chromophore N,Ndimethyl-4-nitroaniline. This compound is commonly used as a reference in studies focused on the non-linear optical (NLO) characteristics of chromophores. Using the Knudsen mass-loss effusion method, the vapor pressures of the crystalline phase of N,N-dimethyl-4-nitroaniline were measured over the temperature range between 341.1 K and 363.5 K. The standard molar enthalpy, entropy, and Gibbs energy of sublimation were calculated from the experimental results, at 298.15 K, and compared with those given in the literature. Differential scanning calorimetry was used to determine the temperature and enthalpy of fusion, as well as the isobaric heat capacities of the crystalline compound under study. Additionally, the enthalpic and entropic contributions to N,N-dimethyl-4-nitroaniline’s volatility were assessed, and it was determined that is greatly conditioned by enthalpic factors.

Abstract This work reports an experimental study aiming to determine the thermodynamic properties of five chlorinated compounds with environmental impact. The vapor pressures of the crystalline phases of three isomers of dichlorobenzoic acid (2,4-, 2,5-, and 2,6-) and 2,6-dichlorobenzonitrile were measured at several temperatures using the Knudsen effusion technique. Another technique (a static method based on capacitance diaphragm manometers) allowed the measurement of the vapor pressures of both the crystalline and liquid phases of 2,4-dichlorobenzonitrile between 303.0 and 380.0 K. This latter technique also enabled the measurement of sublimation vapor pressures of 2,6-dichlorobenzonitrile over a larger range interval of temperatures, T = 328.7 and 391.8 K. The standard molar enthalpy, entropy, and Gibbs energy of sublimation (for all the compounds studied) and vaporization (for 2,4-dichlorobenzonitrile) were derived, at reference temperatures, from the experimental vapor pressure results. The temperatures and enthalpies of fusion and the isobaric heat capacities of the five crystalline-substituted benzenes were determined using differential scanning calorimetry. The contributions of the three substituents (-COOH, -CN, and -Cl) to the sublimation thermodynamic properties of the compounds studied were discussed.

Abstract Objective. To evaluate how the tasks carried out by the students in the scope of the PVC educational citizen science project for monitoring the quality of coastal waters contributed to raising their awareness of the problems of marine litter, in particular, the pollution of the ocean by plastics and microplastics, and the importance of chemistry in society. Methods. The project stage here presented consisted of six asynchronous tasks, conducted with digital mediation through the Moodle platform. The project took place in the 2018/2019 school year and involved 442 students and nine chemistry teachers from a middle school in the northern coastal region of Portugal. Data on the impact on students' awareness of the contexts considered were collected from the outputs the students produced in each task. The data were analyzed using the content analysis technique. Discussion. From this analysis emerged indicators of the PVC project's positive contribution to raising students' awareness of the pollution of marine environments by (micro)plastics, as well as raising awareness of the role of chemistry in society. The students expressed positive opinions toward this science and recognized its links with other areas of science and technology. Conclusion. Thus, it was found that citizen science projects significantly promote students' awareness of chemical-environmental subjects by exploring current and relevant contexts.

Abstract In the laboratory, data acquisition systems are important, as they allow us to easily and precisely collect data. In this sense, Arduino emerges as an automatic data acquisition device with great potential, due to its low cost and high versatility. In this work, we describe the development of an experimental apparatus, with automatic data acquisition using Arduino, to determine the variation of the solubility of potassium nitrate in water as a function of temperature. Ten chemistry teachers in initial training were involved in developing and validating that alternative experimental procedure for secondary school. Pre-service chemistry teachers determined the solubility of the aforementioned salt at different temperatures, using both a method for the study of the solubility of salts that does not resort to automatic data acquisition as well as the alternative method proposed in this work. The experimental solubility curves of potassium nitrate were plotted for both situations. The experimental results obtained by both methods are similar and very close to the values reported in the literature. Moreover, chemistry teachers in initial training recognize that the proposed method can promote the development of secondary students' skills such as greater mastery in assembling electrical circuits and in the use of technological devices or software for automatic data acquisition and processing. Thus, the results suggest the feasibility of the developed experimental method for its implementation in an educational context with secondary students and prove it to be an asset for the education of students, when compared to the traditionally used method.

Abstract Scientific research in the field of veterinary pharmacology has provided new opportuni-ties for the development of modified release dosage forms, with the aim to improve therapeutic efficacy and reduce animal stress. The formulation of classical drug molecules with advanced bio-materials has become a new approach to increasing drug bioavailability and improving the therapeutic outcome. The main reasons for the development of modified drug delivery systems for animal use are the need to reduce the animal stress caused by the handling and administration of the drug and reduce the cost in financial and chronological terms. This review discusses the most common delivery systems used in veterinary and the difficulties encountered in innovating therapeutic options in the field. © 2023 Bentham Science Publishers.

Abstract As available tools for crop disease management are scarce, new, effective, and eco-friendly solutions are needed. So, this study aimed at assessing the antibacterial activity of a dried leaf Eucalyptus globulus Labill. aqueous extract (DLE) against Pseudomonas syringae pv. tomato (Pst), Xanthomonas euvesicatoria (Xeu), and Clavibacter michiganensis michiganensis (Cmm). For this, the inhibitory activity of different concentrations of DLE (0, 15, 30, 45, 60, 75, 90, 105, 120, 135, and 250 g L-1) was monitored against the type strains of Pst, Xeu, and Cmm through the obtention of their growth curves. After 48 h, results showed that the pathogen growth was strongly inhibited by DLE, with Xeu the most susceptible species (15 g L-1 MIC and IC50), followed by Pst (30 g L-1 MIC and IC50), and Cmm (45 and 35 g L-1 MIC and IC50, respectively). Additionally, using the resazurin assay, it was possible to verify that DLE considerably impaired cell viability by more than 86%, 85%, and 69% after Pst, Xeu, and Cmm were incubated with DLE concentrations equal to or higher than their MIC, respectively. However, only the treatment with DLE at 120 g L-1 did not induce any hypersensitive response in all pathogens when treated bacterial suspensions were infiltrated onto tobacco leaves. Overall, DLE can represent a great strategy for the prophylactic treatment of tomato-associated bacterial diseases or reduce the application of environmentally toxic approaches.