Examinando por Autor "Sanz, Raúl"

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Amino functionalized mesostructured SBA-15 silica for CO2 capture: Exploring the relation between the adsorption capacity and the distribution of amino groups by TEM
(Elsevier, 2012) Sanz, Raúl; Calleja, Guillermo; Arencibia, Amaya; Sanz-Pérez, Eloy S.
The distribution of amino groups on amino-functionalized SBA-15 materials for CO2 adsorption was studied by Transmission Electron Microscopy (TEM) in combination with a staining technique using RuO4 in order to analyse the influence of the aminated organic chains location on the CO2 adsorption properties. Mesostructured aminofunctionalized SBA-15 materials were obtained by co-condensation, grafting and impregnation using aminopropyl, AP (N), ethylene-diamine, ED (NN), diethylenetriamine, DT (NNN) and polyethyleneimine, PEI, as functionalizing agents. CO2 adsorption isotherms of functionalized samples at 45 ºC showed that both the adsorption capacity (mg CO2/g ads) and the efficiency of amino groups (mol CO2/mol N) depend on the functionalization technique and the amount of organic compound used. While samples synthesized by co-condensation showed negligible CO2 uptake and efficiency, adsorbents prepared by grafting and impregnation presented significant CO2 adsorption capacities but a dissimilar efficiency. Key differences in the location of aminated chains explained the performance of CO2 capture for every adsorbent, being grafted samples the adsorbents where amino groups were better distributed, favouring the CO2 diffusion trough the whole structure.
Coating of Ca(OH)2/gamma-Al2O3 pellets with mesoporous Al2O3 and its application in thermochemical heat storage for CSP plants
(Elsevier, 2020-08-22) Valverde-Pizarro, Claudia; Briones, Laura; Sanz, Eloy; Escola, José María; Sanz, Raúl; González-Aguilar, José; Romero, Manuel
Thermochemical heat storage using the Ca(OH)2 dehydration/hydration reaction for CSP plants requires the development of advanced materials that avoids the breakage shown by conventional CaO pellets. In this work, spherical cores made up of pelletized 60 wt. % Ca(OH)2 and 40 % γ-Al2O3 powders were coated with different mesoporous alumina coverings by means of a dip-coating route, in order to enhance its structural integrity for dehydration/hydration cycles. Three strategies of preparation were devised using as coatings alumina gels containing cetyltrimethylammonium bromide as surfactant in neutral (A2 CS) and acid pH (A4 CS) and without surfactant in neutral medium (A3 CS). In both A2 CS and A4 CS materials, denser alumina coatings were attained originating higher crushing strengths, pointing out the positive role played by the surfactant in the gel makeup. SEM images indicated that A2 presented small alumina grains (0.3 – 3 µm) highly dispersed over their surface, while over A4 CS, long sheets were appreciated. All the materials exhibited high hydration capacities after 10 cycles (> 80%, > 800 kJ/kg) at 250 ºC, but only A2 CS hold its structural integrity that was preserved even after 20 cycles without loss of its hydration capacity.
Cytostatic and Cytotoxic Effects of Hollow-Shell Mesoporous Silica Nanoparticles Containing Magnetic Iron Oxide
(MDPI, 2021-09-21) Pérez Garnes, Manuel; Morales, Victoria; Sanz, Raúl; García Muñoz, Rafael
Among the different types of nanoparticles used in biomedical applications, Fe nanoparticles and mesoporous siliceous materials have been extensively investigated because of their possible theranostic applications. Here, we present hollow-shell mesoporous silica nanoparticles that encapsulate iron oxide and that are prepared using a drug-structure-directing agent concept (DSDA), composed of the model drug tryptophan modified by carbon aliphatic hydrocarbon chains. The modified tryptophan can behave as an organic template that allows directing the hollow-shell mesoporous silica framework, as a result of its micellisation and subsequent assembly of the silica around it. The one-pot synthesis procedure facilitates the incorporation of hydrophobically stabilised iron oxide nanoparticles into the hollow internal silica cavities, with the model drug tryptophan in the shell pores, thus enabling the incorporation of different functionalities into the all-in-one nanoparticles named mesoporous silica nanoparticles containing magnetic iron oxide (Fe3O4@MSNs). Additionally, the drug loading capability and the release of tryptophan from the silica nanoparticles were examined, as well as the cytostaticity and cytotoxicity of the Fe3O4@MSNs in different colon cancer cell lines. The results indicate that Fe3O4@MSNs have great potential for drug loading and drug delivery into specific target cells, thereby overcoming the limitations associated with conventional drug formulations, which are unable to selectively reach the sites of interest.
Designing nanocarriers to overcome the limitations in conventional drug administration for Parkinson’s disease
(Medknow Publications, 2022-08) García-Muñoz, Rafael; McConnell, Joseph; Morales, Victoria; Sanz, Raúl
Neurodegenerative diseases (NDs) have become one of the leading causes of death and disability worldwide, and cause enormous pain and suffering for both patients and their families. Some of the most common NDs include Alzheimer’s disease, Parkinson’s disease (PD) and Huntington’s disease, among others (Feng, 2020). PD is a widespread neurodegenerative disease that affects more than 10 million people worldwide (No author listed, 2021). The direct cause of the disease is unknown, but it is characterized by the selective degeneration of dopaminergic neurons in the midbrain in the substantia nigra. This leads to the depletion of dopamine (3,4-dihydroxyphenethylamine, DA) in the striatum of patients, in addition to the existence of abnormal α-synuclein in nerve cells and the development of toxic protein aggregates in neurons called Lewy bodies, which causes muscle stiffness, slowness of movements and tremors. It is believed that a combination of genetic and environmental factors may be the cause of PD, but the exact reason for the disease is not yet fully understood. In the treatment of neurological diseases, particularly in PD, NPs can play a remarkable role mainly due to their distinctive thermal, magnetic, and physicochemical properties, such as shape, small size, large specific surface area, hydrophobicity, high loading capacity of different moieties and drugs, chemistry and surface charge, and coating and easy functionalization. The latter allows modifying the NPs surface area with various functional molecules, and therefore introducing the capability that NPs reach target sites by means of active targeting strategies for enhanced uptake in specific cells. Therefore, NPs can help DA or alternative therapies to ensure that they: are not metabolized with uncontrolled effects, do not interfere with other organ function, have lasting effects as a consequence of the slow release in a continuous and sustained way, and are even able to cross the BBB to reach the target sites and escape the reticuloendothelial system, thus reducing drug administration and, therefore, reducing side effects (both adverse and otherwise).
Development of stable porous silica-coated Ca(OH)2/γ-Al2O3 pellets for dehydration/hydration cycles with application in thermochemical heat storage
(Elsevier, 2022) Briones, Laura; Valverde Pizarro, Claudia; Barras García, Inés; Tajuelo, C.; Sanz Pérez, Eloy; Sanz, Raúl; Escola, Jose M.; González-Aguilar, José
Thermochemical heat storage based on the CaO + H2O ↔ Ca(OH)2 system is extremely promising in CSP plants that can reach medium to high temperatures, such as those equipped with tower and heliostats. However, the attrition of pure CaO pellets is a major drawback that hampers an actual commercial development. This work proposes the dip-coating of mixed Ca(OH)2/γ-Al2O3 spherical and cylindrical pellets with dense silica and AlMCM-41 (mesoporous silica) gels. The original hardness of pure Ca(OH)2 pellets (<2 N) can be increased up to 31 N using 40 wt% alumina as binder and applying a silica coating. Both gels formed a hard calcium silicate layer upon calcination that helped keeping the structural integrity of the samples after dehydration/hydration cycles. The samples were tested in 10 consecutive cycles at dehydration and hydration temperatures of 600 ◦C and 250–425 ◦C, respectively. Cylindrical pieces displayed higher hardness values and hydration yields compared to the spherical counterparts. Interestingly, porous silica-coated cylindrical pellets achieved a remarkable hydration yield of 85% and presented a hardness value of 8 N after cycling. This was due to its porous nature and the composition of the coating, formed by thin sheets and small grains, which allowed preserving the outer porous structure of the pellet.
Experimental evaluation and energy analysis of a two-step water splitting thermochemical cycle for solar hydrogen production based on La0.8Sr0.2CoO3-δ perovskite
(Elsevier, 2022) Orfila, María; Linares, María; Pérez, Antonio; Barras García, Inés; Molina Gil, Raúl; Marugán, Javier; Botas, Juan Ángel; Sanz, Raúl
A study of the hydrogen production by thermochemical water splitting with a commercial perovskite La0.8Sr0.2CoO3-d(denoted as LSC) under different temperature conditions is presented. The experiments revealed that high operational temperatures for the thermal reduction step (>1000 C) implied a decrease in the hydrogen production with each consecutive cycle due to the formation of segregated phases of Co3O4. On the other hand, the experiments at lower thermal reduction operational temperatures indicated that the material had a stable behaviour with a hydrogen production of 15.8 cm3 STP/gmaterial$cycle during 20 consecutive cycles at 1000 C, being negligible at 800 C. This results comparable or even higher than the maximum values reported in literature for other perovskites (9.80 e10.50 STP/gmaterial$cycle), but at considerable lower temperatures in the reduction step of the thermochemical cycle for the water splitting (1000 vs 1300e1400 C). The LSC keeps the perovskite type structure after each thermochemical cycle, ensuring a stable and constant H2 production. An energy and exergy evaluation of the cycle led to values of solar to fuel efficiency and exergy efficiency of 0.67 and 0.36 (as a percentage of 1), respectively, which are higher than those reported for other metal oxides redox pairs commonly found in the literature, being the reduction temperature remarkably lower. These facts point out to the LSC perovskite as a promising material for full-scale applications of solar hydrogen production with good cyclability and compatible with current concentrating solar power technology.
Hydrogen production by isothermal thermochemical cycles using La0.8Ca0.2MeO3±δ (Me = Co, Ni, Fe and Cu) perovskites
(Elsevier, 2023) Pérez, Alejandro; Orfila, María; Linares, María; Sanz, Raúl; Marugán, Javier; Molina, Raúl; Botas, Juan A.
Solar-driven thermochemical water splitting has the potential to transform concentrated solar energy into green hydrogen and other solar fuels. In this work, La0.8Ca0.2MeO3±d (Me ¼ Co, Ni, Fe and Cu) perovskites have been synthesised by a modified Pechini method and evaluated as materials for hydrogen production by two step thermochemical water splitting cycles. Performing the thermal reduction at temperatures of 1200 and 1000 C, while the oxidation is done at 800 C, allows a remarkable and stable hydrogen production after 5 consecutive cycles. However, the perovskites suffer changes in the structure after each redox cycle, with potential effects in the long-term cyclic operation. On the contrary, the isothermal thermochemical cycles at 800 C produce a stable amount of hydrogen with each consecutive cycle maintaining the perovskite structure. This hydrogen production ranges from 3.60 cm3 STP/gmaterial$cycle for the material with the lowest productivity (La0.8Ca0.2FeO3±d) to 5.02 cm3 STP/gmaterial$cycle for the one with the highest activity (La0.8Ca0.2NiO3±d). Particularly the Ni-based material shows the highest H2 productivity accompanied by very good material stability after 15 consecutive cycles, being possible to combine with current solar thermal facilities based on concentrated solar power technologies like plants with central receivers.
Kidney-Protector Lipidic Cilastatin Derivatives as Structure-Directing Agents for the Synthesis of Mesoporous Silica Nanoparticles for Drug Delivery
(MDPI (Multidisciplinary Digital Publishing Institute), 2021-07-26) Martínez Erro, Samuel; Navas, Francisco; Romaní Cubells, Eva; Fernández García, Paloma; Morales, Victoria; Sanz, Raúl; García Muñoz, Rafael Á.
Mesoporous silica nanomaterials have emerged as promising vehicles in controlled drug delivery systems due to their ability to selectively transport, protect, and release pharmaceuticals in a controlled and sustained manner. One drawback of these drug delivery systems is their preparation procedure that usually requires several steps including the removal of the structure-directing agent (surfactant) and the later loading of the drug into the porous structure. Herein, we describe the preparation of mesoporous silica nanoparticles, as drug delivery systems from structure-directing agents based on the kidney-protector drug cilastatin in a simple, fast, and one-step process. The concept of drug-structure-directing agent (DSDA) allows the use of lipidic derivatives of cilastatin to direct the successful formation of mesoporous silica nanoparticles (MSNs). The inherent pharmacological activity of the surfactant DSDA cilastatin-based template permits that the MSNs can be directly employed as drug delivery nanocarriers, without the need of extra steps. MSNs thus synthesized have shown good sphericity and remarkable textural properties. The size of the nanoparticles can be adjusted by simply selecting the stirring speed, time, and aging temperature during the synthesis procedure. Moreover, the release experiments performed on these materials afforded a slow and sustained drug release over several days, which illustrates the MSNs potential utility as drug delivery system for the cilastatin cargo kidney protector. While most nanotechnology strategies focused on combating the different illnesses this methodology emphasizes on reducing the kidney toxicity associated to cancer chemotherapy.
L‑arginine‑containing mesoporous silica nanoparticles embedded in dental adhesive (Arg@MSN@DAdh) for targeting cariogenic bacteria
(BioMed Central, 2022-12-01) López Ruíz, Marta; Navas, Francisco; Fernández García, Paloma; Martínez Erro, Samuel; Fuentes, María Victoria; Giráldez, isabeI; Ceballos, Laura; Ferrer Luque, Carmen María; Ruíz Linares, Matilde; Morales, Victoria; Sanz, Raúl; García Muñoz, Rafael Á.
Dental caries is the major biofilm-mediated oral disease in the world. The main treatment to restore caries lesions consists of the use of adhesive resin composites due to their good properties. However, the progressive degradation of the adhesive in the medium term makes possible the proliferation of cariogenic bacteria allowing secondary caries to emerge. In this study, a dental adhesive incorporating a drug delivery system based on L-arginine-containing mesoporous silica nanoparticles (MSNs) was used to release this essential amino acid as a source of basicity to neutralize the harmful acidic conditions that mediate the development of dental secondary caries. The in vitro and bacterial culture experiments proved that L-arginine was released in a sustained way from MSNs and diffused out from the dental adhesive, effectively contributing to the reduction of the bacterial strains Streptococcus mutans and Lactobacillus casei. Furthermore, the mechanical and bonding properties of the dental adhesive did not change significantly after the incorporation of L-arginine-containing MSNs. These results are yielding glimmers of promise for the costeffective prevention of secondary caries.
L-Dopa release from mesoporous silica nanoparticles engineered through the concept of drug-structure-directing agents for Parkinson’s disease
(Royal Society of Chemistry, 2021-04-26) Morales, Victoria; McConnell, Joseph; Pérez-Garnes, Manuel; Almendro, Nuria; Sanz, Raúl; García-Muñoz, Rafael
Parkinson’s disease (PD) is a progressive neurodegenerative disease, the 2nd most common after Alzheimer’s disease, the main effect of which is the loss of dopaminergic neurons. Levodopa or L-Dopa is an amino acid used in the treatment of PD that acts as the immediate precursor to dopamine. However, over time the efficacy of the medication gradually decreases requiring modified delivery methods. One of the major challenges for the medication to work is to achieve a gradual continuous supply of L-Dopa to the brain to minimise symptoms. Herein, mesoporous silica nanoparticles (MSNs) were engineered through the concept of drug-structure-directing agents (DSDAs) with inherent therapeutic activity. The DSDA used was L-Dopa drug modified by amidation with fatty acids to buildanionic surfactants that were able to form micelles as templates for the assembly of inorganic precursors to form the silica framework. This templating route produced MSNs with tunable sizes ranging from 100 nm to 1 mm and with different shapes: spherical, with either solid structures with radial mesopores and porous shells, or hollow-shells with inside large void cavities; and elongated, characterized by long hollows covered by mesoporous shells. The concept of using DSDAs to synthesize drug nanocarriers can be used to avoid the surfactant removal and subsequent drug loading steps involved in the synthesis of conventional MSNs. We hypothesized that the L-Dopa released from MSN materials is mediated by the size and solubility of the DSDAs, and the surface chemical interactions between the DSDAs and MSN hosts. Different pHs (acidic and neutral) simulating gastrointestinal tract conditions were tested, and the results showed hardly any release for gastric conditions at pH 1.2, avoiding the premature release in the stomach typical of conventional MSNs, while for intestinal conditions of pH 7.4, the release of L-Dopa occurred in a continuous and sustained manner, which is well suited to the drug’s application and delivery route, and matches well with achieving a sustained L-Dopa delivery to relief symptoms. This could open up new uses for MSNs synthesized by this approach to treat PD.
Magnetically modified-mitoxantrone mesoporous organosilica drugs: an emergent multimodal nanochemotherapy for breast cancer
(Springer Nature, 2024-04-14) Romaní Cubells , Eva; Martínez Erro, Samuel; Morales, Victoria; Chocarro Calvo, Ana; García Martinez, Jose M.; Sanz, Raúl; García Jimenez, Custodia; García Muñoz, Rafael
Background Chemotherapy, the mainstay treatment for metastatic cancer, presents serious side effects due to off-target exposure. In addition to the negative impact on patients’ quality of life, side effects limit the dose that can be administered and thus the efficacy of the drug. Encapsulation of chemotherapeutic drugs in nanocarriers is a promising strategy to mitigate these issues. However, avoiding premature drug release from the nanocarriers and selectively targeting the tumour remains a challenge. Results In this study, we present a pioneering method for drug integration into nanoparticles known as mesoporous organosilica drugs (MODs), a distinctive variant of periodic mesoporous organosilica nanoparticles (PMOs) in which the drug is an inherent component of the silica nanoparticle structure. This groundbreaking approach involves the chemical modification of drugs to produce bis-organosilane prodrugs, which act as silica precursors for MOD synthesis. Mitoxantrone (MTO), a drug used to treat metastatic breast cancer, was selected for the development of MTO@MOD nanomedicines, which demonstrated a significant reduction in breast cancer cell viability. Several MODs with different amounts of MTO were synthesised and found to be efficient nanoplatforms for the sustained delivery of MTO after biodegradation. In addition, Fe3O4 NPs were incorporated into the MODs to generate magnetic MODs to actively target the tumour and further enhance drug efficacy. Importantly, magnetic MTO@MODs underwent a Fenton reaction, which increased cancer cell death twofold compared to non-magnetic MODs. Conclusions A new PMO-based material, MOD nanomedicines, was synthesised using the chemotherapeutic drug MTO as a silica precursor. MTO@MOD nanomedicines demonstrated their efficacy in significantly reducing the viability of breast cancer cells. In addition, we incorporated Fe3O4 into MODs to generate magnetic MODs for active tumour targeting and enhanced drug efficacy by ROS generation. These findings pave the way for the designing of silica-based multitherapeutic nanomedicines for cancer treatment with improved drug delivery, reduced side effects and enhanced efficacy.
Mesostructured SiO2-doped TiO2 with enhanced thermal stability prepared by a soft-templating sol-gel route
(ELSEVIER, 2008) Calleja, Guillermo; Serrano, David P.; Sanz, Raúl; Pizarro, Patricia
Mesostructured SiO2-TiO2 mixed oxides have been prepared by a soft-templating sol-gel route, using a non-ionic triblock copolymer as structure directing agent. Tetraethylorthosilicate (TEOS) and titanium tetraisopropoxide (TTIP) have been employed as Si and Ti sources, respectively. Using a prehydrolysis TEOS step allows mixed oxides to be produced with a homogeneous porosity and with no phase segregation, in a wide range of Si/Ti compositions. Both the hydrolysis molar ratio and the silicon content have been found to be important factors determining the final properties of these materials. For instance, mixed oxides containing low silicon concentrations exhibit N2 physisorption isotherms typical of mesoporous materials, although with an important contribution of microporosity. On the other hand, increasing the hydrolysis molar ratio makes more difficult to reach a total dispersion of SiO2 through the TiO2 matrix. Even with low SiO2 loadings, the thermal stability is effectively enhanced, when compared to the equivalent pure TiO2 materials, as a consequence of a delay in the titania crystallization to anatase. Thus, after calcination at 300 ºC for 3 h, mixed oxides containing low Si/Ti ratios (¿ 20) show BET surface area in the range 290-346 m2/g, while pure TiO2 materials largely collapse under the same treatment and their BET surface area drop strongly to values around 125 m2/g. This synthesis route, therefore, provides mesoporous TiO2-rich materials with enhanced stability and textural properties, which is of high interest for applications as catalysts and supports.
Mitoxantrone-Derivative Drug Structure-Directing Agent for the Synthesis of Magnetic Mesoporous Silica Nanoparticles for Breast Cancer Treatment
(American Chemical Society, 2024-05-20) Romaní-Cubells, Eva; Martinez-Erro, Samuel; Morales, Victoria; Grieken, Rafael van; García Muñoz, Rafael A.; Sanz, Raúl
Cancer causes hundreds of thousands of deaths worldwide each year. Chemotherapy, the treatment of choice for invasive cancers, presents severe side effects related to off-target exposure that limit its dosage and, thus, its efficacy. Nanomedicine has emerged as a potential tool to overcome these problems. Among the nanocarriers, mesoporous silica nanoparticles (MSNs) have attracted much attention due to their high surface area (up to 1000 m2 g–1), the versatility in size and pore diameter, and their ease of functionalization. However, drug leakage from the MSNs usually occurs before the nanocarriers reach their target, reducing drug efficacy and causing adverse effects. Our group has developed a promising method to increase drug loading capacity while preventing premature drug release. This strategy consists of the use of a drug structure-directing agent (DSDA) that plays a dual role, acting as a pharmacological prodrug and as a template for the synthesis of MSNs. Here, we successfully synthesized a DSDA from the anticancer drug mitoxantrone (MTO), which is used in clinical practice for the treatment of metastatic breast cancer, and used it to synthesize magnetic MSNs whose porosity was fully filled with the MTO prodrug (magnetic MTO-C12@MSNs). The release behavior was pH-dependent, showing negligible drug release at physiological pH and a significant increase at the pH of the tumoral microenvironment. Finally, the efficacy of magnetic MTO-C12@MSNs in reducing breast cancer cell viability was confirmed, demonstrating the potential of this material as an efficient drug delivery system to target breast cancer tumors while avoiding side effects.
Promising Anticancer Prodrugs Based on Pt(IV) Complexes with Bisorganosilane Ligands in Axial Positions
(American Chemical Society, 2024-04-09) Navas, Francisco; Chocarro Calvo, Ana; Iglesias Hernández, Patricia; Fernández García, Paloma; Morales, Victoria; García Martínez, José Manuel; Sanz, Raúl; De la Vieja, Antonio; García Jiménez, Custodia; García Muñoz, Rafael Á.
We report two novel prodrug Pt(IV) complexes with bis-organosilane ligands in axial positions: cis-dichloro(diamine)-trans-[3-(triethoxysilyl)propylcarbamate]- platinum(IV) (Pt(IV)-biSi-1) and cis-dichloro(diisopropylamine)-trans-[3-(triethoxysilyl) propyl carbamate]platinum(IV) (Pt(IV)-biSi-2). Pt(IV)-biSi-2 demonstrated enhanced in vitro cytotoxicity against colon cancer cells (HCT 116 and HT-29) compared with cisplatin and Pt(IV)-biSi-1. Notably, Pt(IV)-biSi-2 exhibited higher cytotoxicity toward cancer cells and lower toxicity on nontumorigenic intestinal cells (HIEC6). In preclinical mouse models of colorectal cancer, Pt(IV)-biSi-2 outperformed cisplatin in reducing tumor growth at lower concentrations, with reduced side effects. Mechanistically, Pt(IV)- biSi-2 induced permanent DNA damage independent of p53 levels. DNA damage such as double-strand breaks marked by histone gH2Ax was permanent after treatment with Pt(IV)-biSi-2, in contrast to cisplatin's transient effects. Pt(IV)-biSi-2's faster reduction to Pt(II) species upon exposure to biological reductants supports its superior biological response. These findings unveil a novel strategy for designing Pt(IV) anticancer prodrugs with enhanced activity and specificity, offering therapeutic opportunities beyond conventional Pt drugs.
Reticulated porous structures of La0.8Al0.2NiO3-δ perovskite for enhanced green hydrogen production by thermochemical water splitting
(Elsevier, 2024-12) Pérez, Alejandro; Orfila, María; Díaz, Elisa; Linares, María; Sanz, Raúl; Marugán, Javier; Molina, Raúl; Botas, Juan A.
The preparation and optimisation of La0.8Al0.2NiO3-δ (LANi82) perovskite shaped as reticulated porous ceramic (RPC) structures for H2 production by thermochemical water splitting is presented for the first time. The perovskite was first synthesised in powder form following a modified Pechini method. The redox properties of the LANi82 were first tested under N2/air flow in a thermogravimetric analyser. After that, the sponge replica method for preparing RPCs was optimised in terms of slurry composition and final thermal treatment to obtain a LANi82-RPC structure with porosity and strength appropriate to enhance heat and mass transfer in further solar reactors. The optimised LANi82-RPC material showed an outstanding hydrogen production of 8.3 cm3 STP/gmaterial·cycle at isothermal conditions (800 °C). This production was increased up to 11.5 cm3 STP/gmaterial·cycle if the thermal reduction was performed at 1000 °C. Additionally, a stable activity with almost constant H2 production in consecutive cycles was obtained for the optimised LANi82-RPC in both cases. The structure of the reticulated porous materials, with open macroporosity and wide interconnected channels, enhances heat and mass transfer, leading to higher hydrogen productions of the LANi82-RPC as compared to the materials as powder form in the same experimental set-up. These facts reinforce the favourable prospects of LANi82-RPC for large-scale hydrogen production, improving the coupling to current solar thermal concentration technologies developed, such as concentrated solar power tower
Surface-functionalization of mesoporous SBA-15 silica materials for controlled release of methylprednisolone sodium hemisuccinate: Influence of functionality type and strategies of incorporation
(Elsevier, 2017-03-01) Ortiz-Bustos, Josefa; Martín, Antonio; Morales, Victoria; Sanz, Raúl; García-Muñoz, Rafael Á.
Mesoporous SBA-15 silica materials functionalized with several organic moieties, that include different polarities and hydrophobicities, were investigated as matrices for controlled drug delivery. The functionalities were incorporated into SBA-15 using two methods: direct synthesis or co-condensation route and post-synthesis grafting. Methylprednisolone sodium hemisuccinate, a synthetic pharmaceutical compound used as anti-inflammatory and immunosuppressant, was loaded onto the pristine and functionalized mesoporous SBA-15 silica materials. The influence of the type of organic moieties as well as their incorporation method onto the inorganic silica framework has been evaluated. The results show that SBA-15 functionalized with aminopropyl trimethoxysilane groups has the largest capacity of drug adsorption, clearly higher than the provided by materials functionalized with other groups, independently of the synthesis route. Additionally, materials synthesized by the co-condensation approach show a lower degree of drug retention than the same material synthesized by grafting technique. This fact is attributed to the distinct localization of the functionality, more accessible in the case of the grafting procedure, and hence suggesting that stronger interactions among the SBA-15 functionalized surfaces and the model drug are established. To ascertain whether other organosilanes containing amino groups can provide more effective loading and controlled drug delivery, at neutral and acidic conditions (pH of 7.4 and 4.6, respectively), it was also investigated the incorporation by grafting of several amino organic moieties onto the SBA-15 silica materials. It was concluded that as the number of amino groups incorporated into SBA-15 material increased, not only the drug loading capacity was higher, but the functionalized silica material vehicles slowed down the drug delivery. Finally, it was confirmed that cell viability was largely unaffected by amino-functionalized mesoporous SBA-15 silica materials after 72 h of incubation time.
SYNTHESIS OF HIERARCHICAL TS-1 ZEOLITE FROM SILANIZED SEEDS
(ELSEVIER, 2010) Serrano, D.P.; Sanz, Raúl; Pizarro, Patricia; Moreno, Inés
Hierarchical TS-1 zeolites with a bimodal pore architecture, consisting of the typical MFI micropores and an additional mesoporosity, have been synthesized by grafting an organosilane compound to the zeolitic seeds previously prepared from two different raw materials: a liquid gel and an amorphous SiO2-TiO2 xerogel. These hierarchical TS-1 zeolites show an excellent catalytic behavior in olefin epoxidation reactions employing organic hydroperoxides as oxidants due to the presence of the secondary mesoporosity, which makes possible the access and interaction of bulky molecules with the Ti active sites
The key role played by mesoporous alumina as binder for obtaining ultra-hard CaO based pellets for thermochemical heat storage leveraging the CaO/CaCO3 cycle
(Elsevier, 2024-03-07) Castro-Yáñez, David; Erans, María; Peral, Ángel; Sanz, Raúl; González-Aguilar, José; Romero, Manuel; Briones, Laura; Sanz-Pérez, Eloy Santiago; Escola, José María
The synthesis of CaO-based pellets with high energy storage and suitable mechanical resistance after prolonged cycling is pivotal for the successful implementation of the Calcium looping (CaL) technology for energy storage in CSP plants. In this work, CaO-based spherical pellets (CAA) were prepared made up of 60 wt % Ca(OH)2 and varying ratios (0–40 wt %) of commercial γ-Al2O3 and mesoporous γ-Al2O3 (m-Al2O3). They were tested in TG in several CO2 carbonation/decarbonation cycles (15 and 50 for selected pellets) and their respective average crushing strengths measured. After 15 cycles, the optimum pellet CAA 20-20 (60 wt % Ca(OH)2/20 wt % γ-Al2O3/20 wt % m-Al2O3) exhibits a remarkable energy storage density of 1030 kJ/kg with a superb crushing strength of ~29 N. This was ascribed to the enhanced formation of the calcium aluminate mayenite (Ca12Al14O33), since the high BET surface area (384 m2 g􀀀 1) of mesoporous γ-Al2O3 promotes the interaction with calcium oxide. Additionally, CAA 20-20 showed meaningful porosity that favored CO2 mass transport. Interestingly, after 50 cycles, the optimum CAA 20-20 pellet maintained a high carbonation yield (0.46), representing an 84 % of the initial value and corresponding to an energy storage density of ~873 kJ/kg. Additionally, the optimum CAA 20-20 pellet was coated with an external layer of Al-MCM-41 silica that augmented its crushing strength up to 37 N, with a concurrent slight abatement in the carbonation yield and energy storage density after 50 cycles (0.43 and ~824 kJ/kg). Consequently, both uncoated and coated CAA 20-20 pellet are promising for the successful implementation of CaL in CSP plants.