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10.3390/catal11091130 2 Hernández R., Hernández-Reséndiz J.R., Cruz-Ramírez M., Velázquez-Castillo R., Escobar-Alarcón L., Ortiz-Frade L., Esquivel K. Au-TiO2 synthesized by a microwave- and sonochemistry-assisted sol-gel method: Characterization and application as photocatalyst. 10.3390/catal10050574 6 Fernández-Perales M., Rozalen M., Sánchez-Polo M., Rivera-Utrilla J., López-Ramón M.V., Álvarez M.A. Solar degradation of sulfamethazine using rGO/Bi composite photocatalysts. The sonochemistry-synthesized photocatalysts displayed the most promising results, with improved PC removal, and a catalyst gold content of 0.7 wt.% was found to be optimal for this process. Over recent years, public concerns have arisen about environmental pollution by so-called emerging organic pollutants (EOPs) in water sources and factory effluents, because of their potentially adverse effects on human health and aquatic ecosystems. [Extracted from the article]

The objective of this study was to summarize the results obtained in a wide research project carried out for more than 15 years on the catalytic activity of different catalysts (activated carbon, metal–carbon xerogels/aerogels, iron-doped silica xerogels, ruthenium metal complexes, reduced graphene oxide-metal oxide composites, and zeolites) in the photooxidation (by using UV or solar radiation) and ozonation of water pollutants, including herbicides, naphthalenesulfonic acids, sodium para-chlorobenzoate, nitroimidazoles, tetracyclines, parabens, sulfamethazine, sodium diatrizoate, cytarabine, and surfactants. All catalysts were synthesized and then texturally, chemically, and electronically characterized using numerous experimental techniques, including N2 and CO2 adsorption, mercury porosimetry, thermogravimetric analysis, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, diffuse reflectance UV–vis spectroscopy, photoluminescence analysis, and transmission electron microscopy. The behavior of these materials as photocatalysts and ozonation catalysts was related to their characteristics, and the catalytic mechanisms in these advanced oxidation processes were explored. Investigations were conducted into the effects on pollutant degradation, total organic carbon reduction, and water toxicity of operational variables and the presence of different chemical species in ultrapure, surface, ground, and wastewaters. Finally, a review is provided of the most recent and relevant published studies on photocatalysis and catalyzed ozonation in water treatments using similar catalysts to those examined in our project. [ABSTRACT FROM AUTHOR]

Copper ferrites containing Cu+ ions can be highly active heterogeneous Fenton catalysts due to synergic effects between Fe and Cu ions. Therefore, a method of copper ferrite nanosphere (CFNS) synthesis was selected that also permits the formation of cuprite, obtaining a CFNS composite that was subsequently calcined up to 400 °C. Composites were tested as Fenton catalysts in the mineralization of phenol (PHE), p-nitrophenol (PNP) and p-aminophenol (PAP). Catalysts were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and magnetic measurements. Degradation of all phenols was practically complete at 95% total organic carbon (TOC) removal. Catalytic activity increased in the order PHE < PNP < PAP and decreased when the calcination temperature was raised; this order depended on the electronic effects of the substituents of phenols. The as-prepared CFNS showed the highest catalytic activity due to the presence of cubic copper ferrite and cuprite. The Cu+ surface concentration decreased after calcination at 200 °C, diminishing the catalytic activity. Cuprite alone showed a lower activity than the CFNS composite and the homogeneous Fenton reaction had almost no influence on its overall activity. CFNS activity decreased with its reutilization due to the disappearance of the cuprite phase. Degradation pathways are proposed for the phenols. [ABSTRACT FROM AUTHOR]

A study was conducted on the behavior as Fenton catalysts of three commercial mixed iron oxides: copper ferrite, magnetite, and ilmenite, using H 2 O 2 for the degradation and mineralization of gallic acid (GA) at temperatures between 15 and 35 °C and pH of 4.3. Investigation of the activity of the catalysts was complemented by study of the metal ion leaching under reaction conditions. GA was completely mineralized with the three mixed iron oxides in the following order of catalytic activity: CuFe 2 O 4 > Fe 3 O 4 > FeTiO 3 , and the ferrites could be quickly and completely separated after the reaction by a magnetic field. According to these results, there appears to be a synergic effect between Cu and Fe ions placed in octahedral sites, and Cu ions may be the main active sites for HO radical generation. The efficiency of H 2 O 2 utilization followed the inverse order of the catalytic activity of the mixed iron oxides, likely because the excess hydroxyl radicals generated during the reaction were quenched by hydrogen peroxide, yielding the less reactive hydroperoxide radicals. A very large amount of Cu and Fe ions leached from copper ferrite and decreased at higher reaction temperatures. These leached ions also acted as homogeneous Fenton catalysts in GA degradation and mineralization. A much lower amount of Fe ions was leached from magnetite and ilmenite in comparison to copper ferrite. From the perspective of long-term applications, magnetite with intermediate catalytic activity but with higher efficiency and much lower Fe ion leaching in comparison to copper ferrite may be more appropriate for GA removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon nitride (gCN) was synthesised with different barbituric acid (BA) contents. • gCN photocatalytic response was improved by merging copolymerisation and exfoliation. • More N-vacancies and surface defects increased charge transfer and light absorption. • Positive-shifted VB potential in gCNex-1.6BA material allows a direct RhB oxidation. • BA reduced the bandgap and created mid-gap states for enhanced production of ROS. Graphitic carbon nitride (gCN) photocatalysts were synthesised by copolymerisation of dicyandiamide precursor and different barbituric acid (BA) shares, followed by thermal exfoliation. The morphological, textural, structural, photo- and electrochemical properties of the obtained materials were studied to identify the effect of BA on the material exfoliation. Moreover, its influence on photocatalytic efficiency was investigated by the degradation of a model contaminant (rhodamine B – RhB) under simulated solar irradiation. The results indicated that incorporating carbonyl-based networks of BA into the aromatic moieties of the gCN structure contributed to a higher degree of exfoliation. Furthermore, this endowed the copolymerised materials with a larger surface area since there was a more disordered nanosheet formation and increased porosity. The best-performing catalyst was the 1.6 wt% BA-modified material, owing to the higher density of nitrogen vacancies detected in the exfoliated gCN material. This density of vacancies yielded a larger quantity of active sites at gCN sheet edges, a more rapid electronic transfer and inhibited photo-induced electron/hole pairs recombination. The newly integrated electronic properties, induced by the copolymerisation synthesis with 1.6 wt% of BA, improved the photocatalytic degradation of the RhB by direct oxidation with photogenerated positive holes and more abundant oxy-radicals. The presence of the BA copolymer during gCN synthesis also permitted, after thermal exfoliation, exceptionally lower energy mid-gap positions to occur, which is highly beneficial for an accelerated oxidation mechanism. [ABSTRACT FROM AUTHOR]

The incorporation of organic groups into sol-gel silica materials is known to have a noticeable impact on the properties and structure of the resulting xerogels due to the combination of the properties inherent to the organic fragments (functionality and flexibility) with the mechanical and structural stability of the inorganic matrix. However, the reduction of the inorganic content in the materials could be detrimental to their thermal stability properties, limiting the range of their potential applications. Therefore, this work aims to evaluate the thermal stability of hybrid inorganic-organic silica xerogels prepared from mixtures of tetraethoxysilane and organochlorinated triethoxysilane precursors. To this end, a series of four materials with a molar percentage of organochlorinated precursor fixed at 10%, but differing in the type of organic group (chloroalkyls varying in the alkyl-chain length and chlorophenyl), has been selected as model case study. The gases and vapors released during the thermal decomposition of the samples under N 2 atmosphere have been analyzed and their components determined and quantified using a thermogravimetric analyzer coupled to a Fourier-transform infrared spectrophotometer and to a gas chromatography-mass spectrometry unit. These analyses have allowed to identify up to three different thermal events for the pyrolysis of the organochlorinated xerogel materials and to elucidate the reaction pathways associated with such processes. These mechanisms have been found to be strongly dependent on the specific nature of the organic group. [Display omitted] • Determination of the thermal stability of different organochlorinated silica xerogels with adsorptive properties. • Identification of functional groups present in thermal decomposition vapors by FT-IR. • Thermal decomposition process in harmony with the observed MS signal. • Identification of pyrolytic compounds by gas chromatography. • Decomposition mechanisms of xerogels consistent with the compounds obtained by chromatography. [ABSTRACT FROM AUTHOR]

The properties of hybrid silica xerogels obtained by the sol-gel method are highly dependent on the precursor and the synthesis conditions. This study examines the influence of organic substituents of the precursor on the sol-gel process and determines the structure of the final materials in xerogels containing tetraethyl orthosilicate (TEOS) and alkyltriethoxysilane or chloroalkyltriethoxysilane at different molar percentages (RTEOS and ClRTEOS, R = methyl [M], ethyl [E], or propyl [P]). The intermolecular forces exerted by the organic moiety and the chlorine atom of the precursors were elucidated by comparing the sol-gel process between alkyl and chloroalkyl series. The microstructure of the resulting xerogels was explored in a structural theoretical study using Fourier transformed infrared spectroscopy and deconvolution methods, revealing the distribution of (SiO)4 and (SiO)6 rings in the silicon matrix of the hybrid xerogels. The results demonstrate that the alkyl chain and the chlorine atom of the precursor in these materials determines their inductive and steric effects on the sol-gel process and, therefore, their gelation times. Furthermore, the distribution of (SiO)4 and (SiO)6 rings was found to be consistent with the data from the X-ray diffraction spectra, which confirm that the local periodicity associated with four-fold rings increases with higher percentage of precursor. Both the sol-gel process and the ordered domains formed determine the final structure of these hybrid materials and, therefore, their properties and potential applications. [ABSTRACT FROM AUTHOR]

Hybrid silica xerogels combine the properties of organic and inorganic components in the same material, making them highly promising and versatile candidates for multiple applications. They can be tailored for specific purposes through chemical modifications, and the consequent changes in their structures warrant in-depth investigation. We describe the synthesis of three new series of organochlorinated xerogels prepared by co-condensation of tetraethyl orthosilicate (TEOS) and chloroalkyltriethoxysilane (ClRTEOS; R = methyl [M], ethyl [E], or propyl [P]) at different molar ratios. The influence of the precursors on the morphological and textural properties of the xerogels was studied using 29Si NMR (Nuclear Magnetic Resonance), FTIR (Fourier-Transform Infrared Spectroscopy), N2, and CO2 adsorption, XRD (X-ray Diffraction), and FE-SEM (Field-Emission Scanning Electron Microscopy). The structure and morphology of these materials are closely related to the nature and amount of the precursor, and their microporosity increases proportionally to the molar percentage of ClRTEOS. In addition, the influence of the chlorine atom was investigated through comparison with their non-chlorinated analogues (RTEOS, R = M, E, or P) prepared in previous studies. The results showed that a smaller amount of precursor was needed to detect ordered domains (ladders and T8 cages) in the local structure. The possibility of coupling self-organization with tailored porosity opens the way to novel applications for this type of organically modified silicates. [ABSTRACT FROM AUTHOR]

A series of reduced graphene oxide-TiO2 composites (rGO-TiO2) were prepared by hydrothermal treatment using graphite and titanium isopropoxide as raw materials. The structural, surface, electronic, and optical properties of the prepared composites were extensively characterized by N2 adsorption, FTIR, XRD, XPS, Raman spectroscopy, and DRS. GO was found to be effectively reduced and TiO2 to be in pure anatase phase in all composites obtained. Finally, experiments were performed to evaluate the effectiveness of these new materials as photocatalysts in the degradation of ethylparaben (EtP) by UV radiation. According to the band-gap energies obtained (ranging between 3.09 eV for 4% rGO-TiO2 to 2.55 eV for 30% rGO-TiO2), the rGO-TiO2 composites behave as semiconductor materials. The photocatalytic activity is highest with a rGO content of 7 wt % (7% rGO-TiO2), being higher than observed for pure TiO2 (Eg = 3.20 eV) and achieving 98.6% EtP degradation after only 40 min of treatment. However, the degradation yield decreases with higher percentages of rGO. Comparison with rGO-P25 composites showed that a better photocatalytic performance in EtP degradation is obtained with synthesized TiO2 (rGO-TiO2), probably due to the presence of the rutile phase (14.1 wt %) in commercial P25. [ABSTRACT FROM AUTHOR]

This work provides insight into the correlation between the luminescent response of a water-vapour optical fibre sensor and the textural properties of its lanthanide-doped silica coating. To this end, a library of 16 silica xerogels derived from combinations between 2 lanthanide dopants (EuIII, TbIII) and 8 antenna ligands was synthesised and characterised by photoluminescence spectroscopy and N 2 and CO 2 adsorption-desorption isotherms, among others. Based on the best luminescent response and most-suited porous texture, the material doped with TbIII and 2,2′-(4-(2-Ethoxyethoxy)pyridine-2,6-diyl)bis(4,5-dihydrooxazole) was selected to construct the probe. A film of this material was affixed to a commercial silica fibre by dip-coating and the resulting sensor was tested in a climatic chamber with relative humidity ranging from 20 to 90% to obtain normalised time-response and calibration curves at three temperatures. The response was linear up to certain water-vapour concentrations, beyond which abruptly changed to polynomial, acting against the sensor resolution. The adsorption mechanism was elucidated by comparing the isosteric enthalpies of adsorption calculated from the sensor calibration curves to those determined from the monolith water-vapour isotherms, revealing that capillary condensation in the membrane mesopores was the key phenomenon leading to the response deviating from linearity. • Luminescent silica xerogel as the chemical membrane for a fibre optic sensor. • Luminescent xerogel with remarkable Stokes Shift and photostability for sensing. • Relationship between silica coating textural parameters and sensor response. • Relationship between isosteric enthalpy of adsorption and sensor response. • Measurement mechanism explanation in a water vapour fibre optic sensor. [ABSTRACT FROM AUTHOR]

Abstract: Activated carbon cloth was shown to be a good support for the growth and differentiation of mesenchymal stem cells (MSCs). By using this approach, we improved the cell culture procedure and reduced the laboratory time required to obtain a very large number of MSCs suitable for utilization or differentiation. [Copyright &y& Elsevier]

Heterogeneous photocatalysts for water decontamination were obtained by the optimized synthesis of bismuth-functionalized reduced graphene oxide (rGO/Bi) using the Hummer method and microwave treatment. Sulfamethazine (SMZ) was used as model pollutant to evaluate the photocatalytic efficacy. Photocatalysts were characterized by VP-SEM, HRTEM, XDR, XPS, RAMAN, and FTIR analyses, which confirmed the effective reduction of GO to rGO and the presence of bismuth as a crystalline phase of Bi2O3 polydispersed on the surface. Their performance was influenced by the rGO/Bi ratio, microwave temperature, and treatment time. The as-obtained 5%rGO/Bi composite had the highest photocatalytic activity for SMZ degradation under visible light irradiation (λ > 400 nm), achieving 100% degradation after only 2 h of treatment. The degradation yield decreased with higher percentages of rGO. Accordingly, the rGO/Bi catalysts efficiently removed SMZ, showing a high photocatalytic activity, and remained unchanged after three treatment cycles; furthermore, cytotoxicity tests demonstrated the nontoxicity of the aqueous medium after SMZ degradation. These findings support the potential value of these novel composites as photocatalysts to selectively remove pollutants in water treatment plants. [ABSTRACT FROM AUTHOR]