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•Electrophoretic deposition of CaCO3 dispersed in isopropyl alcohol was performed.•Isopropyl alcohol is electrochemically decomposed to yield CO2.•The CO2 formed reacts with Ca2+ ions ...producing hierarchical CaCO3 structures.•The hierarchical structures formed could be promising for biomedical applications.
In this work, a combined electrophoretic/electrochemical deposition is reported for the formation of CaCO3 hierarchical structures. In a first step, CaCO3 microparticles with bar shape were synthesized under a microwave-assisted methodology. According to the characterization techniques, aragonite is the main polymorph in the sample, with a small amount of calcite. The as-obtained particles were dispersed in isopropyl alcohol (IPA) with calcium nitrate as charging agent for colloidal stabilization. Then, a voltage of 30 V was applied for 30 min between two aluminum plates at 5 mm of distance. Under these conditions, IPA is electrochemically decomposed in CO2 which then reacts with calcium ions forming new CaCO3 particles over the microparticles previously synthesized. The result is a hierarchical structure which could be promising for bone-tissue engineering and catalysis.
In the present work, the Bi
W
O
photocatalyst has been prepared by an easy and prompt co-precipitation route. From the structural characterization, we have stated that the formation of the Bi
W
O
is ...accompanied by a small amount of the Bi
WO
oxide, which gradually decreases by increasing the calcination temperature. The conduction and valence band edges of the Bi
W
O
semiconductor were experimentally estimated for the first time using the X-ray photoelectron (XPS) and diffuse reflectance (DRS) spectroscopies. The best photocatalytic performance was attained for the sample calcined at 700°C, which showed the highest production of hydroxyl radicals, superoxide ions as well as the highest photodegradation of the ciprofloxacin drug. In addition, by means of photoluminescence spectroscopy we propose that the effective separation of the photogenerated charge carriers in the sample calcined at 700°C produces a higher production of reactive oxygen species and thus a higher photoactivity under solar-like irradiation conditions.
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•Content and bioaccessibility of glucosinolates and micronutrients have been studied in Brassicaceae.•Bioaccessibility of the main glucosinolates in Brassicaceae presented medium ...values.•Indolic glucosinolates showed the highest bioaccessibility percentages.•Vegetable Brassicaceae crops are good dietary sources for Ca, Se, Ni and Zn.•This study demonstrates the high nutritional qualities of vegetable Brassicaceae crops.
Leaf samples from five Brassicaceae species (Brassica carinata, Brassica oleracea, Brassica rapa, Eruca vesicaria and Sinapis alba) were analyzed to determine their contents of glucosinolates and trace elements, and the bioaccessibility of these compounds.
Considerable variability in the total contents and glucosinolate profiles was observed in the Brassicaceae species, with the total amounts ranging from 8.5 µmol/g dw in Brassica oleracea to 32.9 µmol/g dw in Sinapis alba. Bioaccessibilities of the predominant glucosinolates were moderate, ranging from 13.1% for glucoraphanin to 43.2% for gluconapin, which is particularly relevant as they have been implicated in a variety of anti-carcinogenic mechanisms.
Trace element concentrations were: Se (28–160 µg/Kg dw); Cr (0.31–4.03 µg/g dw); Ni (0.19–1.53 µg/g dw); Fe (8.6–18.8 µg/g dw); Zn (20.8–41.5 µg/g dw); Ca (6.2–15.2 mg/g dw). Brassicaceae leaves were also moderate dietary sources of Se, Ni, Zn and Ca.
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•Growing cruciferous vegetables under conventional or organic conditions does not guarantee a higher content in beneficial compounds.•60–78 % of the glucosinolates initially present ...in the leaves of this plant species would be capable of reaching human enterocytes.•Ca, Cu, Se and Zn bioaccessibility in green tissues of cruciferous was also high.•Glucosinolates and trace elements bioaccessibility of cruciferous seeds were extremely low (below 1%).•Cruciferous could be included as a part of a balanced, healthy diet.
Green tissues and seeds from cruciferous vegetables growing in conventional and ecological conditions (Brassica carinata; Brassica rapa; Eruca vesicaria and Sinapis alba) were analyzed to determine their contents of glucosinolates, isotihiocyanates (ITCs) and inorganic micronutrients (Ca, Cr, Cu, Fe, Mn, Ni, Se and Zn), and the bioaccessibility of these compounds. Regarding total contents and bioaccessibility values of these compounds, no clear difference was found between the organic and conventional systems. Glucosinolates bioaccessibility present in green tissues were high, with values around 60–78%. In additon, it was quantified in bioaccessible fraction ITCs concentrations such as Allyl – ITC; 3 – Buten – 1 – yl – ITC and 4 – Penten – 1 – yl – ITC. Trace elements bioaccessibility in green tissues was also high for Ca (2.26–7.66 mg/g), Cu (0.60–2.78 µg/g), Se (9.93–74.71 µg/Kg) and Zn (12.98–20.15 µg/g). By contrast, the bioaccessibility of glucosinolates and trace elements in cruciferous seeds was extremely low. With the exception of Cu, these bioaccessibility percentages did not exceed 1% in most cases.
In the present work, we report the preparation of mesoporous graphitic-like carbon nitride (mpg-C3N4) using SBA-15 as hard template agent. The mpg-C3N4 exhibited a hypsochromic shift in the UV–vis ...absorption profile probably due to a lower degree of condensation of the tris-s-triazine units in its conjugate aromatic system. In addition, the mesoporous material demonstrated enhanced textural properties with a surface area estimated in 49.8 m2/g, which is one order of magnitude higher than the surface area of the bulk g-C3N4 sample. In this sense, the mpg-C3N4 shows a higher photocatalytic performance in the production of H2 through the water splitting process. Furthermore, the mpg-C3N4 was also used as fluorescent probe for the sensitive detection of Au3+ ions in aqueous solution. The fluorescence quenching was quantitatively analyzed by the Stern-Volmer equation using the evolution of the photoluminescence (PL) emission at 371 nm (λexc = 250 nm). The limit of detection (LOD) was estimated at 1.1 μM, which was lower than the estimated LOD using the bulk g-C3N4 sample (2.1 μM). To the best of our knowledge, this work reports for the first time the detection of Au3+ ions through fluorescence quenching using g-C3N4 samples with different textural properties.
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•Mesoporous g-C3N4 was prepared using SBA-15 as hard template agent.•The mesoporous material showed a high photocatalytic hydrogen production.•Mpg-C3N4 was used as a fluorescent probe for the sensitive detection of Au3+ ions.•This work reports for the first time the detection of Au3+ ions using g-C3N4.
We propose a dual-type mechanism which could explain the improved photoactivities in Er3+-doped TiO2 systems. On the one hand, Er3+ improved the electronic charge separation process, enhancing the ...UV-photo-assisted process.
An additional, small contribution of NIR photons in the overall mechanism due to an energy transfer process from erbium ions to TiO2. Display omitted
► By a simple hydrothermal method, we achieve the Er3+–TiO2 photoactive system. ► Synergetic mechanism involving photoluminescence and photocatalysis is evidenced. ► Er3+ aids to the charge separation increasing the efficiency of the photocatalyst. ► Er3+ provides extra UV photons from its luminescence upon NIR excitation. ► We show good performances for degradation of pollutants on gas and liquid phase.
Erbium-doped TiO2 materials are synthesized by means of a surfactant-free hydrothermal method having good photoactivities for the liquid-phase degradation of phenol and MB and the gas phase of toluene. From the structural and morphological characterization, it has been stated that the presence of Er3+ induces a progressive anatase cell expansion due to its incorporation in the TiO2 lattice. The best photocatalytic performance was attained for the samples with 2at% of Er3+ irrespective of the chemical degradation reaction essayed. From activity and optical studies under different irradiation excitation conditions, a dual-type mechanism is proposed to be at the origin of the photocatalytic activity enhancement. On one hand, the improvement observed under UV irradiation occurs by the effective charge separation promoted by Er3+ species which would act as electron scavenger. Besides, the up-conversion luminescence process of Er3+ allows profiting the NIR range of the lamp and transferring energy in the UV range to the TiO2. The dual action of Er ions located at anatase networks will open up a wide roadway for the developing of an integral solar active photocatalyst.
•By a simple hydrothermal method we achieve the BiVO4 photoactive monoclinic phase.•Preparation parameters effect on the photoactivity has been studied.•Photodegradation of MB is strongly affected by ...the crystallite size and morphology.•Photodegradation of RhB is closely affected by the ζ-potential of BiVO4.•Evolution of ζ-potential could be related with preferred facet exposition.
BiVO4 hierarchical structures were synthesized by means of a surfactant free hydrothermal method having good photoactivities for the degradation of Methylene Blue and Rhodamine B under UV–vis irradiation. From the structural and morphological characterization it has been stated that BiVO4 present the monoclinic crystalline phase with different morphologies depending on the pH value. For Methylene Blue the photodegradation rate is strongly affected by the crystallite size and higher (004) facet exposition. On the contrary, for Rhodamine B, the ζ-potential of the surface clearly determines the photocatalytic performance of BiVO4 catalyst.
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•Hybrid WO3/g-C3N4 photocatalysts were prepared by an ultrasonic process.•WO3/g-C3N4 significantly improves the photoactivity compared to pristine materials.•A discussion about ...oxidizing species is given on the system studied.
In this work, the WO3/g-C3N4 heterojunction system has been prepared through a sonochemical process at 37 kHz. The composites were characterized by powder X-ray diffraction, diffuse reflectance and Fourier transform infrared spectroscopies, scanning electron microscopy and nitrogen adsorption-desorption measurements. The photocatalytic activity of the coupled system was evaluated by the photodegradation of the Orange G dye and the ciprofloxacin antibiotic under solar-like irradiation conditions. In this regard, the sample with 5 wt.% WO3 exhibited the higher photoactive behavior than the single WO3 and g-C3N4 materials. The role of the photogenerated holes, hydrogen peroxide (H2O2), hydroxyl radicals and superoxide ions were examined by means of the radical scavengers KI, catalase, 2-propanol and benzoquinone, respectively. Furthermore, the reusability of the WO3/g-C3N4 system was tested through repetitive photodegradation tests where the photocatalyst exhibits a similar photoactive behavior after three cycles.
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► By a simple impregnation method we achieve the g-C3N4–TiO2 photoactive composite. ► Preparation parameters do not affect the structural and textural properties of TiO2. ► ...Photoactivity of TiO2 is strongly affected by the presence g-C3N4. ► The intimate junction of g-C3N4 with TiO2 leads to enhanced charge separation.
g-C3N4 and TiO2 hybrid structures are synthesized by means of a simple impregnation method having good photoactivities for the degradation of phenol under UV irradiation. From the wide structural and surface characterization we have stated that the presence of g-C3N4 notably affect the surface feature of TiO2 (surface area and pore size distribution). Enhanced photoactivities have been obtained for composites systems. The best result was obtained for 2wt% loading of g-C3N4 leading to a 70% of improvement with respect to bare TiO2 in the reaction rate. The effective charge carrier separation was proposed as the responsible of such improved photoactivity.
