Publications

Abstract. Hydrothermic features in Galicia (northwest Spain) have been used since ancient times for therapeutic purposes. A characterization of these thermal waters was carried out in order to understand their behaviour based on inorganic pattern and water-rock interaction mechanisms. In this way 15 thermal water samples were collected in the same hydrographical system. The selected thermal water samples were classified using principal component analysis (PCA) and partial least squares (PLS) regression analysis in two groups according to their chemical composition: group I with the young water samples and group II with the samples with longest water-rock contact time. This classification agreed with the results obtained by the use of geothermometers and hydrogeochemical modelling, where the samples were classified into two categories according their residence time in the reservoir and their water-rock interaction.

Plasmonic circular dichroism (PCD) is a powerful approach for enhancing chiroptical effects at the nanoscale with promising applications such as optical information processing, sensing, and catalysis. However, a key challenge remains in achieving both strong and tunable optical responses. While most strategies use either intrinsically chiral nanoparticles (NPs) or achiral NPs arranged into chiral assemblies, combining both offers a promising route to amplify chiral optical responses. Here, 4-fold-twisted gold nanorods (cGNRs) were assembled by depletion-induced self-assembly (DISA) into chiral superstructures with tunable PCD properties. By reducing cGNR helicity via chemical etching, we study how building block helicity affects hierarchical structure formation. Whereas static helical supercrystals were obtained on substrates upon evaporation-induced self-assembly (EISA), DISA allowed us to dynamically modulate the interparticle distance in solution from 13 ± 1.2 nm to 6.9 ± 1.0 nm. The assembly/disassembly process was found to be fully reversible, thereby enabling a modulation of the <i>g</i>-factor by 2 orders of magnitude with a switching rate of approximately 1 h. Beyond achieving high dissymmetry factors of 0.2, our approach establishes a reconfigurable PCD platform that is free from ligand exchange constraints and compatible with different NP shapes. Though response times remain too slow for optical computing, these findings are relevant for the development of optical modulators and memory devices based on dynamic chiral metafluids.

A flow-through UV reactor has been implemented in an automated flow-injection/stopped-flow manifold, and used for on-line generation of Se volatile derivatives prior to detection by quartz furnace atomic absorption spectrometry. The presence of a low molecular weight organic acid (formic or acetic) in the carrier was a necessary requirement so that efficient vapour generation was achieved. Stopped-flow conditions were employed with the aim of increasing the time for which the sample zone was subjected to UV irradiation while it was transported to the detector. The simultaneous formation of H2 during the photochemical decomposition of formic acid facilitated the atomization of the Se derivatives in the quartz furnace, and therefore the addition of H2 to the carrier gas, which is necessary for efficient atomisation, could be eliminated. Nevertheless, the presence of H2 in the carrier gas (Ar) was required for efficient atomisation when using acetic acid as carrier. This manifold allowed a sample throughput of 26 h−1 with a detection limit of 0.5 ng mL−1 Se and a repeatability, expressed as relative standard deviation, of 4%. Effect of concomitants in the online generation of Se vapours with the new manifold was investigated. Chloride salts of alkaline and alkaline-earth elements did not interfere at concentrations up to 10 000 mg L−1, but nitrate salts caused a positive effect. Tolerance of typical hydride-forming elements such as As and Sn was much higher with UV vapour generation as compared to chemical hydride generation. The presence of Cu(II) was critical since interference effects are observed from 0.05 mg L−1, but tolerance of Ni(II) was greater with UV vapour generation.

Natural compounds and their derivatives could be used for developing potent therapeutics with significant activity against SARS-COV-2, providing a promising frontline in the fighting against COVID-19.