Examinando por Autor "del Hierro, Isabel"

Mostrando 1 - 14 de 14

2D/2D NiTi-LDH/BiOBr photocatalyst with extraordinary NOx removal under visible light
(Elsevier, 2023) Oliva, M.A.; Ortíz-Bustos, Josefa; Cruz-Yusta, M.; Martin, F.; del Hierro, Isabel; Pérez, Yolanda; Pavlovic, I.; Sánchez, Luis
Many current studies are focused on the development of 2D/2D nanosystems based on non-traditional semiconductors as efficient visible light-active photocatalysts, due to their interesting structural and optical properties. Thus, the charge-separation in heterostructures can be enhanced by boosting the interfacial contact. In this work, robust 2D/2D NiTi/BiOBr composites have been prepared by incorporating a 2D layered BiOBr into NiTi-layered double hydroxides (LDH) for the subsequent study of their photocatalytic action in the control of NOx pollution. The successful formation of a type-II heterojunction between both semiconductors has been confirmed by several characterization techniques (including XPS, NMR and electrochemical studies), indicating an intimate contact interface that helps enhance the visible light photocatalytic performance of NiTi-LDH. In particular, the NiTi–LDH/BiOBr–0.6 heterojunction, with a more efficient separation of photoinduced carriers, showed exceptional NO removal efficiency under visible light and remarkable robustness for the recycling process.
Copper and sulphur co-doped titanium oxide nanoparticles with enhanced catalytic and photocatalytic properties
(RSC, 2020-07-29) Ortiz-Bustos, Josefa; Gómez-Ruiz, Santiago; Mazario, Jaime; Domine, Marcelo E.; del Hierro, Isabel; Pérez, Yolanda
Copper and sulphur co-doped titanium oxide nanoparticles have been prepared by the sol–gel method to develop versatile catalysts exhibiting enhanced catalytic and photocatalytic properties. Structural, morphological, chemical composition, and optical characterizations of the synthesized titanium oxide nanoparticles have been carried out in order to study the effect of incorporating copper and sulphur on the catalytic and photocatalytic activities of TiO2 nanoparticles. Optimal incorporation of copper and sulphur to the titanium dioxide nanoparticles promotes the photocatalytic degradation of ciprofloxacin in water under irradiation of UV or visible light. Complete degradation of ciprofloxacin was achieved after 120 min with the 0.4% Cu–0.5% S–TiO2 photocatalyst using UV and in 90 min applying visible light. Cu–S–TiO2 nanoparticles also exhibit high activity (94–98% conversion) and excellent recyclability (with no loss of activity after 14 runs) in selective oxidation of thioanisole using H2O2 as an oxidant.
Copper-functionalized nanostructured silica-based systems: Study of the antimicrobial applications and ROS generation against gram positive and gram negative bacteria
(Elsevier, 2019-11-19) Díaz-García, Diana; Ardiles, Perla R.; Díaz-Sánchez, Miguel; Mena-Palomo, Irene; del Hierro, Isabel; Prashar, Sanjiv; Rodríguez-Diéguez, Antonio; Paulina L., Páez; Gómez-Ruiz, Santiago
A series of copper-functionalized SBA-15 (Santa Barbara Amorphous) materials containing the ligands triethoxysilylpropylmaleamic acid (maleamic) or triethoxy-3-(2-imidazolin-1-yl)propylsilane (imidazoline) have been prepared. The nanostructured silica-based systems SBA-maleamic, SBA-imidazoline, SBA-maleamic-Cu and SBA-imidazoline-Cu were characterized by several methods observing that the functionalization took place mainly inside the pores of the mesoporous system. The antimicrobial behaviour of the synthesized materials against Staphylococcus aureus and Escherichia coli was tested observing a very potent activity of the copperfunctionalized systems (minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values for SBA-maleamic-Cu of ca. 31.25 μg/mL, which correspond with ca. 1.13 μg/mL of Cu). A study of the oxidative stress promoted by the synthesized materials showed that the SBA-maleamic-Cu and the SBAimidazoline- Cu were able to increase the reactive oxygen species (ROS) production in S. aureus by 427% and 373%, respectively, while this increase was slightly lower in E. coli (387 and 324%, respectively). Furthermore, an electrochemical study was carried out in order to determine if these materials interact with lysine or alanine to validate a potential antimicrobial mechanism based on the inhibition of the synthesis of the peptidoglycan of the bacterial wall. Finally, these studies were also performed to determine the potential interaction of the copper-containing materials with glutathione in order to assess if they are able to perturb the metabolism of this tripeptide.
Efficient visible-light-driven photocatalysis: simultaneous degradation of multiple pollutants with bismuth oxyhalide solid solutions
(Royal Society of Chemistry, 2024-06-24) Ortiz-Bustos, Josefa; Pérez del Pulgar, Helena; Gómez-Ruiz, Santiago; del Hierro, Isabel; Pérez, Yolanda
Visible-light-driven photocatalysis is considered as a sustainable and cost-effective method for water remediation. In aquatic environments, the coexistence of multiple contaminants, such as organic and inorganic compounds, poses a potential threat to both biological organisms and human health, complicating their removal. Despite the urgent need for the development of comprehensive solutions, the research on the concurrent and simultaneous removal of multiple pollutants remains limited primarily relies on photocatalysts based on heterojunctions. To address this issue, we have prepared BiOCl0.9I0.1 and BiOBr0.9I0.1 solid solutions, exhibiting well-tailored band gaps and energetics of the conduction and valence bands, using an easy chemical precipitation approach. These synthesized materials exhibited exceptional photocatalytic efficacy under visible light, effectively removing a complex mixture of contaminants, including ciprofloxacin (CIP), methylparaben (MP), and rhodamine B (RhB), from water. Particularly noteworthy was the outstanding performance of BiOCl0.9I0.1, which demonstrated a complete removal of RhB within 10 min, CIP within 40 min, and an 86% degradation of MP within 40 min. This superior performance can be attributed to the materials' exceptional optical and (photo)electrochemical properties. Furthermore, the synergistic or antagonistic effects coexisting contaminants, organic matter, and inorganic ions on the photodegradation process were also investigated. Additionally, the generation of reactive oxygen species (ROS), and the elucidation of the degradation pathways were examined providing valuable insights into the intricate interplay of environmental factors that may have an influence on the photocatalytic performance. Our study shows, therefore, the high potential of BiOCl0.9I0.1 and BiOBr0.9I0.1 as promising candidates for the simultaneous removal of diverse water pollutants, offering a robust and efficient approach towards advancing water purification technologies.
Enhanced adsorption–catalysis combination for the removal of sulphur from fuels using polyoxometalates supported on amphipathic hybrid mesoporous silica nanoparticles
(Royal Society of Chemistry, 2023) Ortíz-Bustos, Josefa; Pérez del Pulgar, Helena; Pérez, Yolanda; del Hierro, Isabel
Polyoxometalate (POM) mesoporous silica-based materials with a low POM loading have been designed with hydrophilic and hydrophobic properties. These materials act as powerful heterogeneous catalysts in oxidative desulfurization (ODS), owing to their ability to adsorb both H2O2 and sulphur-containing compounds from the model oil simultaneously. The formation of charge transfer salts through ion pair interaction with a choline functionality, available on the hybrid silica support, affords robust and recyclable heterogeneous catalysts for the ODS process under mild conditions (45 min and 40 °C). Besides, the nature of the polyoxometalate anions is highly dependent on the characteristics of the silica surface. The masking of silanol groups present on the silica surface using silylating agents, with diverse reactivity and steric hindrance, influences the silica surface–heteropolyanion interactions, as well as heteropolyanion–heteropolyanion interactions. In addition, it modifies the hydrophobic properties of the surface, which is a determining factor in the adsorption properties of non-polar dibenzothiophene (DBT) by the catalysts. Adsorption, an anterior step to the oxidation reaction, has been demonstrated to be key to the superior activity of POM-SiMe3-Chol-MSN, where the silanol groups have been capped by trimethylsilyl groups. For the first time, and to better understand POM–surface and POM–POM anion interactions, an extensive characterization of the materials has been performed using 13C, 31P, and 95Mo MAS NMR spectroscopy and solid-state electrochemical techniques, among others.
Heterogeneous oxidative desulfurization catalysed by titanium grafted mesoporous silica nanoparticles containing tethered hydrophobic ionic liquid: A dual activation mechanism
(Elsevier, 2019-10-25) Cruz, Paula; Granados, Elizabeth-Adriana; Fajardo, Mariano; del Hierro, Isabel; Pérez, Yolanda
In this study, heterogeneous catalysts containing ionic liquid and/or titanium have been prepared and used for oxidative desulfurization. For the synthesis of hybrid mesoporous silica nanoparticles (ILBF4-MSN), a grafting method has been employed with the ionic liquid 1-octyl-3-(3-(triethoxysilyl)propyl)-4,5-dihydro-1H-imidazol-3-ium tetrafluoroborate (ILBF4) which contains a long alkyl chain. Titanium hybrid mesoporous silica nanoparticles (ILBF4-x%TiCp2-MSN) and mesoporous silica nanoparticles containing titanium (TiCp2-MSN) have also been prepared using titanocene dichloride. The catalyst containing ionic liquid and titanium, ILBF4-3%TiCp2-MSN exhibited the highest desulfurization efficiency (99.1%) in model oil with high concentration of DBT and using H2O2 as oxidant. In addition, the effect of immobilization of the ionic liquid on titanium materials has been investigated by solid-state 13C, 47/49Ti and 19F NMR spectroscopy and solid state electrochemical techniques. The titanium species and ionic liquid play an important role in the oxidative desulfurization reaction since they might activate synergistically sulfur derivatives and enhance the process
Mesoporous SBA-15 Modified with Titanocene Complexes and Ionic liquids: Interactions with DNA and other Molecules of Biological Interest Studied by Solid State Electrochemical Techniques.
(Royal Society of Chemistry, 2018) del Hierro, Isabel; Gómez-Ruiz, Santiago; Pérez, Yolanda; Cruz, Paula; Prashar, Sanjiv; Fajardo, Mariano
The immobilization of two titanocene complexes on SBA-15 has been accomplished following post-synthetic procedures. The ionic liquid, 1-methyl-3-[(triethoxysilyl)propyl]imidazolium chloride, has also been incorporated into the titanium containing materials to determine its influence on the interaction with molecules of biological interest. Cyclic voltammetry has been used to study the influence of the ionic liquid on the mechanism of reduction of titanocene derivatives. The interaction of titanocene and titanocene/ ionic liquid-containing mesoporous silica SBA-15 materials, with molecules of biological interest associated with important processes of metallodrug action against cancer cells, has been studied. Thus, we have carried out hydrolysis experiments on the materials functionalized with titanocene derivatives in physiological media to determine their stability and the interaction with serum/transport proteins such as transferrin and BSA and with target molecules such as guanosine, single-stranded DNA and double-stranded DNA by means of solid state voltammetry techniques. A qualitative analysis of the data based on peak current and reduction potential value changes of the couple Ti(IV)/Ti(III) in the presence of biomolecules at physiological pH, has revealed that grafted titanocene complexes show higher affinity for serum/transport proteins than for nucleic acids, indicating that the transport steps to the cells may be easier than the subsequent attack on DNA.
Mesoporous silica nanoparticles functionalized with a dialkoxide diorganotin(IV) compound: In search of more selective systems against cancer cells
(Elsevier, 2020-03-09) Díaz-García, Diana; Sommerova, Lucia; Martisova, Andrea; Skoupilova, Hana; Prashar, Sanjiv; Vaculovic, Tomas; Kanicky, Viktor; del Hierro, Isabel; Hrstka, Roman; Gómez-Ruiz, Santiago
Mesoporous silica nanoparticles (MSN) have been functionalized with the polyamino ligand N1-(3-trimethoxysilylpropyl) diethylenetriamine to give the material MSN-DETATMS (M1). The reaction of M1 with the diphenyltin(IV) compound Sn1 [obtained previously from the reaction of (3-glycidyloxypropyl)trimethoxysilane and diphenyltin(IV) dichloride in the presence of two equivalents of sodium hydroxide] in a quantity to obtain a theoretical 10% wt Sn/SiO2, gave the material MSN-DETATMS-O2-SnPh2 (M2). Alternatively, M1 was reacted with folic acid to achieve the incorporation of the folate fragment via formation of an amido bond MSNDETATMS-FA (M3) and subsequently with Sn1 to give the tin-functionalized material MSN-DETATMS-FA-O2-SnPh2 (M4). M1‒M4 have been characterized by several methods such as infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), X-ray fluorescence (XRF), solid-state NMR spectroscopy, nitrogen adsorption-desorption isotherms, electrochemical methods, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). All the synthesized nanomaterials have been tested in vitro against a wide variety of cancer and noncancer cells in order to determine different aspects of their antitumour effects such as cell uptake, cell death, cell migration and cell invasion, to observe whether the incorporation of folate fragments may increase the cell uptake and selectivity towards cancer cells, thus increasing their potential applicability in future chemotherapeutic approaches.
Modulation of the mechanism of apoptosis in cancer cell lines by treatment with silica-based nanostructured materials functionalized with different metallodrugs
(Royal Society of Chemistry, 2018-08-10) Díaz-García, Diana; Cenariu, Diana; Pérez, Yolanda; Cruz, Paula; del Hierro, Isabel; Prashar, Sanjiv; Fischer-Fodor, Eva; Gómez-Ruiz, Santiago
The mesoporous silica-based material SBA-15 (Santa Barbara Amorphous-15) has been modified with the aminodiol ligand 3-[bis(2-hydroxyethyl)amino]propyltriethoxysilane (PADOH) to give the corresponding material SBA-PADOH. Subsequent functionalization with a diorganotin(IV) compound, SnPh2Cl2 (1), and with two titanocene derivatives, TiCp2Cl2 ([Ti(η5-C5H5)2Cl2] (2)) and TiCpCpPhNfCl2 ([Ti(η5-C5H5) (η5-C5H4CHPhNf)Cl2] (3) (Ph = C6H5; Nf = C10H7)), gave the materials SBA-PADO-SnPh2 (M1), SBA-PADO-TiCp2 (M2) and SBA-PADO-TiCpCp* (M3), respectively. SBA-PADOH and M1–M3 have been characterized by various techniques such as FT-IR, XRD, XRF, solid-state NMR, nitrogen adsorption– desorption isotherms, electrochemical methods, SEM and TEM, observing that the functionalization has mainly taken place inside the pores of the corresponding porous system. In addition, mechanistic aspects of the apoptosis triggered by the synthesized materials have been studied in vitro in tumour cell lines derived from three distinct types of cancer in order to elucidate their growth inhibition and interference with the expression of tumour necrosis factor alfa (TNF-α) and the first apoptosis signal receptor (Fas or tumour necrosis factor receptor 6). It was observed that the antiproliferative and proapoptotic capacity of the materials depends on their functionalization with the different cytotoxic prodrugs (organotin or titanocene derivatives). The study shows that M1–M3 influence the metabolic activity of the tumour cells and modulate the apoptotic pathways by different mechanisms, according to the active compound inside the material.
Photocatalytic oxidative desulfurization and degradation of organic pollutants under visible light using TiO2 nanoparticles modified with iron and sulphate ions
(Elsevier, 2022-03-01) Ortiz-Bustos, Josefa; del Hierro, Isabel; Pérez, Yolanda
The incorporation of iron and sulphate ions on TiO2 nanoparticles has been carried out in order to enhance catalytic performance in environmental remediation. The aim of this work is to design a multifunctional and visible-light active photocatalyst to remove pollutants from transportation fuels and water. The influence of doping with sulphur and iron on the physical, structural, optical, and electrochemical properties of TiO2 has been fully analyzed by a wide variety of techniques. Thus, the incorporation of a low amount of iron improves the photocatalytic performance, as in the case of 1.2%S-0.5%Fe–TiO2 photocatalyst, which shows the highest activity under visible light irradiation. The enhanced behaviour of the electron charge transfer of this photocatalyst has been confirmed by electrochemistry measurements including linear sweep voltammetry and electrochemical impedance spectroscopy. Also, the stability and recyclability of the best photocatalyst have been assessed
Structure, Stability, Electrochemical and catalytic properties of polyoxometalates 1 immobilized on choline-based hybrid mesoporous silica
(Elsevier, 2021) Ortíz-Bustos, Josefa; Pérez, Yolanda; del Hierro, Isabel
Polyoxometalate-based heterogeneous catalysts have been prepared by immobilization 12 of Keggin-type heteropolyacid on hybrid mesoporous silica nanoparticles with choline 13 hydroxide based ionic liquid. The immobilization process has been accomplished by a 14 simple acid-base reaction with phosphomolybdic acid. For comparison purposes, 15 additional supports (hybrid-SBA-15 and TiO2) have been also used in order to establish 16 the nature of the interactions between the heteropolyacid and the surface’s groups of 17 the support. To do this, electrochemical and 31P MAS-NMR studies have been carried 18 out finding the formation of moieties like (Chol)2[HPMo12O40] and/or (Chol)3[PMo12O40] 19 on the silica materials. Polyoxometalate-based heterogeneous catalysts have been 20 effectively tested for the oxidative desulfurization of DBT in model oil. Thus, complete 21 removal of sulphur (99.7 %) was achieved with polyoxometalate supported on the silica 22 after 2 h and using H2O2 as a green oxidant. Additionally, reusability and stability studies 23 of the most active catalyst have been performed.
Supported Choline Hydroxide (Ionic Liquid) on Mesoporous Silica as Heterogeneous Catalyst for Knoevenagel Condensation Reactions
(Elsevier, 2018) del Hierro, Isabel; Pérez, Yolanda; Fajardo, Mariano
In this work hybrid mesoporous SBA-15 and mesoporous silica microspheres functionalized with choline hydroxide ionic liquid have been prepared. A two-step process inspired by the industrial production of choline hydroxide has been developed to synthesize the hybrid SBA-15 material with choline hydroxide ionic liquid (Chol-SBA-15) and the hybrid SBA-15 material with choline hydroxide ionic liquid and hexamethyldisilizane as capping agent (Chol-HMDS-SBA-15). For the preparation of hybrid mesoporous silica microspheres (Chol- MSMs), a co-condensation method has been employed with an ionic liquid prepared by reaction of 3-(glycidyloxypropyl) trimethoxysilane and trimethylamine in aqueous media. The synthesized materials have been fully characterized by elemental analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), N2 adsorption-desorption, transmission electron microscopy (TEM) and 13C CP/MAS NMR spectroscopy. These materials have been tested successfully as catalysts in Knoevenagel condensation of benzaldehyde with RCH2C≡N (R=CN (malononitrile), CO2Et (ethyl cyanoacetate)). The catalyst Chol-MSMs showed high catalytic activity, 99% of conversion and 99% of selectivity towards ethyl 2-cyano-3-phenylacrylate in 2 h of reaction and using ethanol as solvent. In addition, their reusability without loss of activity has been demonstrated
Tuning of type-I and type-II mechanisms for visible light degradation in tris(styryl)benzene-sensitized TiO2 nanoparticles
(Elsevier, 2021-01) Ortiz-Bustos, Josefa; del Hierro, Isabel; Sánchez-Ruiz, Antonio; García-Martínez, Joaquín C.; Pérez, Yolanda
The visible light activation of TiO2 have been carried out by sensitization method using robust and metal-free tris(styryl)benzene (TSB) compounds as efficient sensitizers, which can be easily prepared. TSB compounds decorated with three carboxylic acid (3COOH) or aldehyde (3CHO) groups have been tightly incorporated to the surface of TiO2 nanoparticles through different chemical linkage. The synthesized materials have been deeply characterized by different spectroscopic and analytical techniques to investigate the effect of TSB sensitizers in the photocatalytic properties of TiO2. Comparative and exhaustive optical studies have been performed in solution between TSB compunds and sensitized TiO2 nanoparticles, computational studies have been also carried to shed light on the sensitization process. The results reveal different mechanisms of sensitization (Type I and Type II) between the 3CHO and 3COOH compounds and TiO2 nanoparticles. Thus, the influence of electronic injection mechanism (direct or indirect) has been studied and mechanisms have been proposed for photodegradation of dye pollutants under UV and visible irradiation. TiO2 nanoparticles sensitized with 3COOH (TiO2-3COOH) exhibited the best visible photocatalytic activity with a removal efficiency around 98% for methylene blue in 30 min and methyl orange after 60 min.
Versatile titanium dioxide nanoparticles prepared by surface-grown polymerization of polyethylenimine for photodegradation and catalytic CeC bond forming reactions
(Elsevier, 2019-07-11) Ortiz-Bustos, Josefa; Fajardo, Mariano; del Hierro, Isabel; Pérez, Yolanda
Crystalline TiO2 anatase nanoparticles have been synthesized by a sol-gel procedure with a certain ratio of brookite phase due to low calcination temperature. TiO2 NPs have been successfully functionalized with hyperbranched polyethylenimine polymer (PEI) by the surface polymerization of aziridine or with N1-(3-trimethoxysilylpropyl)-diethylenetriamine (DT) by surface silanization to form catalyst with notable basic and photocatalytic properties. The TiO2 NPs have been characterized by X-ray diffraction (XRD), adsorption-desorption isotherms, fourier-transform infrared spectroscopy (FT-IR), diffuse reflectance UV–vis spectroscopy (DRUV-vis), elemental analysis, thermogravimetric analysis, transmission electron microscopy (TEM), photoluminiscence spectroscopy (PL) and solid-state voltammetry. Functionalized TiO2 NPs have revealed to be efficient in the photodegradation of methylene blue in water and as basic heterogeneous catalysts carbon-carbon forming reactions as Knoevenagel condensation, multicomponent reactions and Biginelli reaction. PEI-TiO2 with mesoporous structure and narrow size pore distribution, fulfill the requirements imposed to an eco-friendly and cost-effective catalyst since it is easily synthesized and recyclable.