Publications

Abstract The ohmic heating also known as direct Joule heating, is an advanced thermal processing method, mainly used in the food industry to rapidly increase the temperature for either cooking or sterilization purposes. Its use in organic synthesis, in the heating of chemical reactors, is an emerging method that shows great potential, the development of which has started recently. This Concept article focuses on the use of ohmic heating as a new tool for organic synthesis. It presents the fundamentals of ohmic heating and makes a qualitative and quantitative comparison with other common heating methods. A brief description of the ohmic reactor prototype in operation is presented as well as recent examples of its use in organic synthesis at laboratory scale, thus showing the current state of the research. The advantages and limitations of this heating method, as well as its main current applications are also discussed. Finally, the prospects and potential implications of ohmic heating in future research in chemical synthesis are proposed.

Abstract Microwave synthetized sulfur and nitrogen co-doped carbon dots responded selectively to nitric oxide (NO) at pH 7. Citric acid, urea and sodium thiosulfate in the proportion of 1:1:3 were used respectively as carbon, nitrogen and sulfur sources in the carbon dots microwave synthesis. For this synthesis, the three compounds were diluted in 15 mL of water and exposed for 5 min to a microwave radiation of 700 W. It is observed that the main factor contributing to the increased sensitivity and selectivity response to NO at pH 7 is the sodium thiosulfate used as sulfur source. A linear response range from 1 to 25 mu M with a sensitivity of 16 mu M-1 and a detection limit of 0.3 mu M were obtained. The NO quantification capability was assessed in standard and in fortified serum solutions.

Abstract The heat capacity and thermal behavior trend along the 1-alkyl-3-methylimidazolium hexafluorophosphate [C(n)C(1)im][PF6] (with n = 2-10,12) ionic liquids series, is used to explore the effect of the alkyl chain length in the nanostructuration. The heat capacities of the studied ILs were measured with an uncertainty better than +/- 0.15% and are in excellent agreement with the available data in the literature. An odd-even effect for the specific and volumic heat capacities of the [C(n)C(1)im][PF6] series was found. The observed odd-even effect in the liquid heat capacity was rationalized considering the preferential orientation of the terminal -CH3 group. The higher specific/volumic heat capacities shown for the [C(n)C(1)im][PF6] and [C(8)C(1)im][PF6] are an indication of an additional conformational disorder increase in the liquid phase that could be related with a weaker alkyl chain interdigitation capability of the even number chain ILs. The melting temperatures and consequent Delta H-1(s)m(0) and Delta S-1(s)m(0) trend along the alkyl series present a V-shape profile that is explained based on the analysis of the balance between the initial decrease of the electrostatic interaction potential and the increase of the van der Waals interactions with the increasing size of the alkyl side chain of the cation, The inhibition of crystallization for intermediate alkyl chain size (from [C(n)C(1)im][PF6] to [C(8)C(1)im][PF6]) seems to arise from the overlapping of the hypothetical cold crystallization temperature by the melting temperature. Above the critical alkyl size, CAS, a regular increase in the entropy and enthalpy profiles presents a similar shape than the observed in other alkane series and is a strong support of the intensification of the ILs nanostructuration.

Abstract Cyclic peptides (CPs) belong to an interesting class of peptides that have been widely studied over the past decades. This class of peptides has been applied in different fields, such as the pharmaceutical industry (due to their antibacterial or antitumor activity), agricultural applications (as fungicides), diagnostics, and vaccines.One of the main sources of inspiration for designing CPs is Nature itself. Different approaches to the design of CPs have been used, depending on the application for which they are prepared. Indeed, understanding the mechanisms of action of CPs will contribute to an improved rational design of new CPs with different applications. In this chapter, we show the presence of the CPs and their derivatives in Nature, and provide its accepted classification. Methods for designing new CPs as well as the respective experimental approaches are also discussed. Finally, some of the main important applications of these systems are reviewed.

Abstract In this study, following a systematic approach, we used aquatic species (bacteria Vibrio fischeri and microalgae Raphidocelis subcapitata) and different human cell lines (Caco-2, HepG2, SV-80 and HaCaT) representing different tissues and exposure pathways, to investigate how two organic stabilizers (PVA and DMSO) used for NMs dispersion influence their physicochemical properties, the persistence of metals in suspension and the toxicity/ecotoxicity of two metallic NMs (nano-Ag and nano-Cu). Although the stabilizers are expected to contribute to improve the dispersion and stability of NMs, the results obtained clearly showed that no similar changes in toxicity and morphological properties of the nano-Ag can be expected after its stabilization with PVA. Thus, regarding human cell lines, the reduction in the average size of the PVA-nano-Ag was followed by a reduction or maintenance of its toxicity, but the opposite was observed for the aquatic species tested since an increase in the average size enhanced its toxicity. As far as nano-Cu is considered DMSO contributed for a better dispersion of this nanomaterial, however this was not translated in a similar toxicity/ecotoxicity modification. In summary, even for nano-Cu, for which few or no data exists regarding its toxicity after stabilization with organic compounds, it was confirmed with consistent data, that the toxicity of metallic NMs is a complex combination of average size, chemical composition, solubilization or persistence in suspension of the metallic forms, interaction with test medium components and sensitivity of test species and cell lines. The combination of all of these factors makes the toxicity of metallic NMs unpredictable and points for the need of an extensive evaluation of each new formulation.

Abstract In this work we developed a new force field model (FFM) for propylene glycol (PG) based on the OPLS all-atom potential. The OPLS potential was refined using quantum chemical calculations, taking into account the densities and self-diffusion coefficients. The validation of this new FFM was carried out based on a wide range of physicochemical properties, such as density, enthalpy of vaporization, self-diffusion coefficients, isothermal compressibility, surface tension, and shear viscosity. The molecular dynamics (MD) simulations were performed over a large range of temperatures (293.15-373.15 K). The comparison with other force field models, such as OPLS, CHARMM27, and GAFF, revealed a large improvement of the results, allowing a better agreement with experimental data. Specific structural properties (radial distribution functions, hydrogen bonding and spatial distribution functions) were then analyzed in order to support the adequacy of the proposed FFM. Pure propylene glycol forms a continuous phase, displaying no microstructures. It is shown that the developed FFM gives rise to suitable results not only for pure propylene glycol but also for mixtures by testing its behavior for a 50 mol % aqueous propylene glycol solution. Furthermore, it is demonstrated that the addition of water to the PG phase produces a homogeneous solution and that the hydration interactions prevail over the propylene glycol self-association interactions.

Abstract The detection of dissolved carbon dioxide (dCO(2)) is made possible through a colorimetric effect that occurs in a sensitive membrane. The reaction with dCO(2) changes the pH of the membrane causing a small difference in its colour which results in a characteristic absorbance spectrum band near 435 nm. A sensing platform based on this effect was developed and tested in gaseous and in aqueous environments. It is a combination of a bundle of large core fibre optics (with diameters above 200 mu m) with light emission diodes (LEDs) in the visible range of the spectrum, a silicon photodetector and a polymer membrane sensitive to CO2. A variation in the absorption of 3 / %VV was obtained in the range from 0 to 1.6 % of gaseous CO2 with an estimated response time below 60 seconds.

Abstract The present work aimed to evaluate the effects of exogenous application of 24-epibrassinolide (24-EBL) in the physiological and biochemical responses of Solanum nigrum L exposed to nickel (Ni). After the seedling stage, 24-EBL treated and untreated plants were grown hydroponically for 28 days in the presence of 100 mu M NiSO4 center dot 6H(2)O. The exposure of S. nigrum to high levels of Ni resulted in a decrease of biometric parameters in both shoots and roots, with a partial recovery of both fresh weight and length in the 24-EBL pre-treated plants. Higher levels of Ni were found in roots, regardless of the pre-treatment with the brassinolide. Older leaves of Ni-exposed plants exhibited cell death symptoms, manifested in the form of chlorotic and necrotic spots. A decrease in photosynthetic pigments, soluble protein and relative RuBisCO contents were also observed in Ni-treated plants, however Ni-mediated toxicity was partially reverted by 24-EBL pre-treatment. Lipid peroxidation was chosen as a stress biomarker and malondialdehyde (MDA) levels did not change neither in roots nor in shoots. Soluble proline levels increased in response to Ni in both organs, but the pre-treatment with the phytohormone seems to mitigate the differences observed from the control shoots and roots. When ROS accumulation is concerned, generally Ni-exposed plants exhibited decreases in O-2(center dot)- and H2O2 levels regardless of being or not treated with 24-EBL. The Ni treatment led to a positive response of the plant's enzymatic antioxidant system. In shoots of Ni-stressed plants, an enhanced activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX), accompanied by a decline of catalase (CAT) activity were observed. In roots, increases in SOD and CAT activities were detected in response to Ni, whilst APX was not. 24-EBL pre-treatment caused a decline in APX and CAT activities, while SOD activity was positively affected. Reverse transcriptase-PCR analysis revealed that mRNA transcript levels do not correlate with total enzymatic activity for SOD, CAT and APX, suggesting that these enzymes are regulated posttranscriptionally. Overall, the results suggested that Ni did not induce a severe oxidative stress in S. nigrum, yet the exogenous application of the brassinolide enhanced the plant tolerance to Ni.

Abstract We report the application of two poly[Ni(salen)]-type electroactive polymer films as new electrochromic materials. The two films, poly[Ni(3-Mesalen)] (poly[1]) and poly[Ni(3-MesaltMe)] (poly[2]), were successfully electrodeposited onto ITO/PET flexible substrates, and their voltammetric characterization revealed that poly[1] showed similar redox profiles in LiClO4/CH3CN and LiClO4/propylene carbonate (PC), while poly[2] showed solvent-dependent electrochemical responses. Both films showed multielectrochromic behavior, exhibiting yellow, green, and russet colors according to their oxidation state, and promising electrochromic properties with high electrochemical stability in LiClO4/PC supporting electrolyte. In particular, poly[1] exhibited a very good electrochemical stability, changing color between yellow and green (lambda = 750 nm) during 9000 redox cycles, with a charge loss of 34.3%, an optical contrast of Delta T = 26.2%, and an optical density of Delta OD = 0.49, with a coloration efficiency of ? = 75.55 cm(2) C-1. On the other hand, poly[2] showed good optical contrast for the color change from green to russet (Delta T = 58.5%), although with moderate electrochemical stability. Finally, poly[1] was used to fabricate a solid-state electrochromic device using lateral configuration with two figures of merit: a simple shape (typology 1) and a butterfly shape (typology 2); typology 1 showed the best performance with optical contrast Delta T = 88.7% (at lambda = 750 nm), coloration efficiency eta = 130.4 cm(2) C-1, and charge loss of 37.0% upon 3000 redox cycles.