Persona: Rojas Cervantes, María Luisa
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Rojas Cervantes
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Publicación Rheological Properties of Different Graphene Nanomaterials in Biological Media(MDPI, 2022-05-18) Cerpa Naranjo, Arisbel; Pérez Piñeiro, Javier; Navajas Chocarro, Pablo; Lado Touriño, Isabel; Barrios Bermúdez, Niurka; Moreno, Rodrigo; Rojas Cervantes, María LuisaCarbon nanomaterials have received increased attention in the last few years due to their potential applications in several areas. In medicine, for example, these nanomaterials could be used as contrast agents, drug transporters, and tissue regenerators or in gene therapy. This makes it necessary to know the behavior of carbon nanomaterials in biological media to assure good fluidity and the absence of deleterious effects on human health. In this work, the rheological characterization of different graphene nanomaterials in fetal bovine serum and other fluids, such as bovine serum albumin and water, is studied using rotational and microfluidic chip rheometry. Graphene oxide, graphene nanoplatelets, and expanded graphene oxide at concentrations between 1 and 3 mg/mL and temperatures in the 25–40 ◦C range were used. The suspensions were also characterized by transmission and scanning electron microscopy and atomic force microscopy, and the results show a high tendency to aggregation and reveals that there is a protein–nanomaterial interaction. Although rotational rheometry is customarily used, it cannot provide reliable measurements in low viscosity samples, showing an apparent shear thickening, whereas capillary viscometers need transparent samples; therefore, microfluidic technology appears to be a suitable method to measure low viscosity, non-transparent Newtonian fluids, as it is able to determine small variations in viscosity. No significant changes in viscosity are found within the solid concentration range studied but it decreases between 1.1 and 0.6 mPa·s when the temperature raises from 25 to 40 ◦C.Publicación Fe-Cu Doped Multiwalled Carbon Nanotubes for Fenton-like Degradation of Paracetamol Under Mild Conditions(MDPI, 2020-04-14) Barrios Bermúdez, Niurka; González Avendaño, Marta; Cerpa Naranjo, Arisbel; Rojas Cervantes, María LuisaA series of carbon nanotubes doped with Fe and/or Cu, Fe100−xCux/CNT (x = 0, 25, 50, 75 and 100) has been prepared by an easy method of wetness impregnation of commercial multiwalled carbon nanotubes previously oxidized with nitric acid. The wide characterization of the solids by different techniques demonstrates that the incorporation of Fe and Cu to the CNTs has been successfully produced. Fe100−xCux/CNT samples were tested as catalysts in the removal of paracetamol from aqueous solution by a combined process of adsorption and Fenton-like oxidation. Under mild conditions, 25 ◦C and natural pH of solution, i.e., nearly neutral, values of oxidation of paracetamol between 90.2% and 98.3% were achieved after 5 h of reaction in most of cases. Furthermore, with the samples containing higher amounts of copper, i.e., Cu100/CNT and Fe25Cu75/CNT, only 2 h were necessary to produce depletion values of 73.2% and 87.8%, respectively. The influence of pH and dosage of H2O2 on the performance has also been studied. A synergic effect between both Cu+/Cu2+ and Fe2+/Fe3+ in Fenton-like reaction was observed. These results demonstrate that Fe100−xCux/CNT are powerful Fenton-like catalyst for degradation of paracetamol from aqueous solution and they could be extended to the removal of other organic pollutants.Publicación Efficient Methylene Blue Degradation by Activation of Peroxymonosulfate over Co(II) and/or Fe(II) Impregnated Montmorillonites(MDPI, 2024-07-27) Barrios Bermúdez, Niurka; Cerpa Naranjo, Arisbel; Rojas Cervantes, María Luisa; https://orcid.org/0000-0003-4932-544X; https://orcid.org/0000-0002-4767-880XTwo commercial montmorillonites, namely montmorillonite K10 (MK10) and montmorillonite pillared with aluminum (MPil) were impregnated with cobalt(II) and/or iron(II) acetates by incipient wetness impregnation and used to activate peroxymonosulfate (PMS) for the degradation of methylene blue (MB) dye in water. Various characterization techniques, including ICP-MS, XRD, SEM and TEM with EDX, and N2 physisorption, confirmed the successful impregnation process. The removal of the dye resulted from a combined effect of adsorption and PMS activation through Co3+/Co2+ redox couples. The MK10 series exhibited a higher degree of dye adsorption compared to the MPil series, leading to enhanced dye decomposition and superior catalytic performance in the former. The influence of catalyst mass, dye concentration, and initial pH was investigated. SO4•− radicals were found as the dominant reactive oxygen species. Co2+-impregnated montmorillonites showed better performance than their Fe2+-impregnated counterparts, with MK10-Co achieving complete MB removal in just 20 min. High degradation values of MB were achieved using lower PMS/MB ratios and amount of catalyst than others reported in the literature, showing the efficiency of cobalt-impregnated montmorillonites. Moreover, the catalysts maintained excellent catalytic activity after three reaction cycles.Publicación Amino-Functionalized Multiwall Carbon Nanotubes as Efficient Basic Catalysts for the Formation of γ-Lactams: Synthesis of N-1-Heptenyl-2-pyrrolidinone(MDPI, 2022) Barrios Bermúdez, Niurka; Cerpa Naranjo, Arisbel; Rojas Cervantes, María LuisaIn this work, we prepared a series of N-functionalized carbon nanotubes by means of a process of acylation-amidation of commercial multiwall carbon nanotubes that were previously pre-oxidized with nitric acid. Three different amines, butylamine, N,N-dimethyl ethylenediamine, and ethylenediamine, were used in the process. The characterization of samples by several techniques probed the incorporation of nitrogen atoms to the carbon nanotubes, especially in the case of ethylenediamine. The solids were tested as catalysts in the synthesis of N-1-heptenyl-2-pyrrolidinone, included in the group of a γ-lactams, compounds that show important biological properties. The most active catalyst was that prepared with butylamine, which exhibited the highest SBET and Vpore values and contained an amount of nitrogen that was intermediate between that of the other two catalysts. A yield of 60% to N-1-heptenyl-2-pyrrolidinone was achieved after 3 h at 120 ◦C under free-solvent conditions. This catalyst could be used in four consecutive cycles without significant activity loss.Publicación Comparison of the quality attributes of carrot juice pasteurized by ohmic heating and conventional heat treatment(Elsevier, 2021-06) Negri Rodríguez, Livia N.; Arias, Ricardo; Soteras, Trinidad; Sancho, Ana; Pesquero, Natalia; Rossetti, Luciana; Tacca, Hernán; Aimaretti, Nora; Rojas Cervantes, María Luisa; Szerman, NataliaThis study aimed to evaluate the effect of pasteurization of carrot juice by heat treatment (80 ◦C–7 min) and ohmic heating (OH) on its physicochemical and chromatic parameters, enzymatic and microbiological inactivation, volatile compounds, antioxidant capacity, carotene content, and sensory characteristics, compared to control juice (CJ). Both treatments allowed obtaining microbiologically stable and safe carrot juice and achieved 99% peroxidase inactivation levels. Significant differences were obtained in L* parameter, polyphenoloxidase activity and total antioxidant capacity, compared to HT-treated and CJ. The OH-treated juice presented greater color preference (p < 0.05) by semi-trained panelists and a high level of acceptance among consumers (corresponding to “like extremely”). The results allow concluding that OH could be an alternative to conventional HT for the pasteurization of carrot juice, providing benefits in its sensory perception.