https://hdl.handle.net/10481/15007 2026-04-11T12:43:44Z https://hdl.handle.net/10481/111796 Removal of Parabens from Water by UV-Driven Advanced Oxidation Processes Álvarez, Miguel A.; Mota Ávila, Antonio José; Ruidíaz-Martínez, M.; Cruz-Quesada, G.; López-Ramón, M.V.; Rivera Utrilla, José; Sánchez Polo, Manuel This study analyzed the degradation by direct photolysis with UV radiation of three common-use parabens (methylparaben, MetP, ethylparaben, EtP, and butylparaben, ButP) that have been detected in different types of water. The effect of different operating variables on their degradation by UV radiation was determined. A correlation between the degradation rate constant and the energy difference between the LUMO and HOMO orbitals of the parabens was established. A further study objective was to establish the effectiveness of different advanced oxidation processes in EtP removal from water. Rate constant values increased in the order MetP < EtP < ButP and the highest photodegradation (96.3%) was obtained for ButP, which has the longest alkyl chain. The absence of organic and inorganic compounds in ultrapure water had a positive effect on the photodegradation rate and percentage EtP removal, which ranged from 0.005 min−1 and 37.9%, respectively, in wastewater, to 0.024 min−1 and 88.0% in ultrapure water at 90 min of irradiation. A better performance was observed with the UV/S2O82− system (95.4% removal and 59% mineralization of EtP) than the UV/H2O2 system (83% removal and 48% mineralization of EtP). We identified the degradation by-products of the different parabens and proposed various reaction mechanisms based on these, including esterification, radical hydroxylation, and decomposition processes. Finally, we established that the identified degradation by-products are not cytotoxic. https://hdl.handle.net/10481/111795 Chemical Composition, Enantioselective Profile, and Preliminary Screening of Biological Activities of the Essential Oil from Aerial Parts from Lasiocephalus ovatus Schltdl. Flores, Linda M.; Vinueza, Diego R.; Gilardoni, Gianluca; Mota Ávila, Antonio José; Malagón, Omar Traditionally, Lasiocephalus ovatus Schltdl. (Asteraceae) has been used as an aromatic medic inal plant, particularly in the treatment of kidney-related ailments. However, scientific evidence validating its chemical composition and bioactivity remains limited. According to our literature search, there are no previous studies on the in vitro antibacterial, antioxidant, or anti-inflammatoryactivities of the essential oil from the aerial parts of Lasiocephalus ovatus; therefore, this study provides the first experimental evidence of these biological activities for this species. An essential oil (EO) was steam-distilled from the aerial parts of L. ovatus, grown at 4410 m above sea level in the paramos of Chimborazo Province (Ecuador), and subsequently analyzed. The distillation yield was 0.21% (w/w) based on dry plant material. Gas chromatography was employed for qualitative (GC-MS) and quantitative (GC-FID) analyses, using two different capillary columns, coated with 5% phenyl methyl polysilox ane (non-polar) and polyethylene glycol (polar) stationary phases. Dual stationary phases were required to provide complementary selectivity, which reinforced the identification and quantification of compounds. The major components of the EO were silphinene (3.4–3.5%), δ-selinene (3.6–3.1%), β-cyclogermacrene (18.7–18.1%), kessane (4.5–4.2%), spathulenol (13.3–13.3%), viridiflorol (3.1–3.0%) and neophytadiene (4.8–4.4%), values referred to the non-polar and polar phase respectively. The enantioselective analysis revealed that (1S,5S) (−)-α-pinene, (1S,5S)-(+)-β-pinene and (R)-(−)-α-phellandrene were enantiomerically pure, whereasgermacreneDwaspresentasascalemicmixture. TheessentialoilofL.ovatusexhib ited a minimum inhibitory concentration (MIC) of 250 µg/mL against Staphylococcus aureus and 500 µg/mL against Escherichia coli. Its antibacterial activity is likely associated with the presence of bioactive sesquiterpenes such as silphinene, δ-selinene, and spathulenol, which are known for their membrane-disruptive properties. Regarding its antioxidant potential, the observed moderate radical scavenging activity (SC50 = of 375.7 µg/mL) can be attributed to its complex mixture, particularly to oxygenated terpenoids like viridi f lorol and spathulenol, which are recognized for their radical-neutralizing capacity. In the anti-inflammatory assay, the EO’s moderate potency (IC50 = 165.29 ± 4.75 µg/mL) is also consistent with the anti-inflammatory profile reported for several of its major con stituents, including spathulenol and viridiflorol. While significantly lower than that of aspirin (28.85 ± 7.66 µg/mL), this bioactivity is considerable within the context of a plant extract. Overall, the antibacterial, antioxidant, and anti-inflammatory effects are consistent with the EO’s terpene-rich composition, particularly oxygenated sesquiterpenes, while the enantiomeric distribution of chiral monoterpenes may further modulate bioactivity; consequently, future studies should include enantioselective quantification, broader antiox idant assays (e.g., ABTS, FRAP, ORAC, CUPRAC), cytotoxicity at active concentrations, and mechanistic and in vivo validation. https://hdl.handle.net/10481/111761 Noble-Metal-Free MOF-74-Derived Nanocarbons: Insights on Metal Composition and Doping Effects on the Electrocatalytic Activity Toward Oxygen Reactions Abdelkader Fernández, Víctor Karim; Fernandes, Diana M.; Balula, Salete S.; Cunha Silva, Luís; Pérez Mendoza, Manuel; López Garzón, F. Javier; Pereira, M. Fernando; Freire, Cristina The continuous and dramatic increase of global demand for energy resources makes it urgent to develop affordable nanostructured materials to act as efficient electrocatalysts (ECs) in the energy-related reactions. Metal–organic framework (MOF) template pyrolysis for the production of nanostructured carbon-based materials is a very promising methodology to produce carbon-based ECs. Herein, we report the preparation, characterization (XPS, CHNS analysis, ICP-OES, XRD, TEM, and SEM/EDS), and application as oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) ECs of a plethora of nanostructured carbon materials derived from RT-synthesized (RT, room temperature) MOF-74 with different metal compositions, Co, Ni and Co/Ni, and dopant heteroatoms, N–, S– and N/S-dual-doping. This has allowed the study of the aforementioned parameters’ influence on the OER and ORR electrocatalytic activity in alkaline medium. Highly synergetic effects have been detected in two cases: (1) when N/S-dual-doped carbon is produced from a monometallic Co-MOF-74 template, N,S–Co@C, and (2) when an undoped carbon is derived from bimetallic Co/Ni-MOF-74, Co/Ni@C. These two samples achieve OER performances with η10 = 0.41 and 0.44 V, respectively, along with Tafel slopes of 101 and 93 mV dec–1, being close to the state-of-art OER catalyst performance. In addition, ORR tests showed that the effect of heteroatom doping on ORR activity is always positive, regardless of metal composition. https://hdl.handle.net/10481/111760 Sidewall Chlorination of Carbon Nanotubes by Iodine Trichloride Abdelkader Fernández, Víctor Karim; Domingo García, María; Gutiérrez Valero, Mª Dolores; López Garzón, Rafael; Melguizo, Manuel; García Gallarín, Celeste; López Garzón, F. Javier; Pérez Mendoza, Manuel The halogenation of carbon nanotubes is of great interest, as it allows the modification of the tube properties or it can serve as primary functionalization for a subsequent covalent fixing. Large degrees of fluorination can be reached although chlorine fixing is preferred, if halogenation is used as primary functionalization, as it is a better leaving group. Here, we report an extensive chlorination of multiwalled carbon nanotubes (MWCNTs) by I2Cl6. The reaction has been studied in acetic acid (AC) and in carbon tetrachloride (TC). The influence of the solvent is critical, as the functionalization is not relevant when the reaction is carried out in AC, while it reaches up to 13 atom % when the solvent is TC. Moreover, chlorine functionalization occurs in defects and borders of the tubes when the solvent is AC, while chlorine is largely fixed on the tube walls when TC is the reaction solvent. These different results are due to iodine trichloride coming out in different chemical species depending on the solvent. The correlation of the TPD and XPS spectra has allowed assignment of the fixed chlorine atoms to five chemical environments. None of the samples show intercalation of chlorine as deduced from X-ray diffraction data. https://hdl.handle.net/10481/111759 Advanced Framework-Modified POM@ZIF-67 Nanocomposites as Enhanced Oxygen Evolution Reaction Electrocatalysts Abdelkader Fernández, Víctor Karim; Fernandes, Diana M.; Balula, Salete S.; Cunha Silva, Luís; Freire, Cristina The smart assembly of Co-containing polyoxometalates (POMs) and Co-based zeolitic imidazole frameworks (ZIF-67) is a promising tool to produce active electrocatalysts for the oxygen evolution reaction (OER). The encapsulation of SiW11Co inside ZIF-67 cavities via ‘in situ’ synthesis produced two novel POM@ZIF-67 nanocomposites with low and high POM loadings—SiW11Co@ZIF-67 and SiW11Co[h]@ZIF-67, respectively. Other materials involving the analogue tri-substituted silicotungstate, SiW9Co3@ZIF-67 and SiW9Co3[h]@ZIF-67, have been prepared for comparison reasons. Regardless of the POM substitution degree, we demonstrated that the bidirectional synergistic POM-ZIF-67 interaction found for the already reported material, SiW9Co3@ZIF-67, is applicable to the other first-time prepared nanocomposites. Remarkably, this synergy is radically enhanced in the case of the two high POM loading samples, with these nanostructured materials being very active OER electrocatalysts, exhibiting 150–160 mV decreased overpotentials and much faster kinetics (∼35% decreased Tafel slopes) in relation to pristine ZIF-67. Moreover, they reveal intrinsic OER activities higher than those developed by the expensive commercial references (RuO2 and IrO2 powders) especially in the case of SiW9Co3[h]@ZIF-67. This important electrocatalytic improvement can be related to the higher POM loadings achieved, as well as to the formation of an open defect-enriched phase wrapping the ‘standard’ ZIF-67 framework in these nanomaterials.