•A new method for nanoparticles at low temperature and short reaction time.•The Saponin quillaja sp. can reduce Au+3 to Au (0), forming nanoparticles.•The AuNps, when impregnated with TiO2, show a ...strong photocatalytic activity for the reduction of CO2 to other products.
With Saponin quillaja sp usage as a reducing and stabilizing agent, it was possible to obtain Gold Nanoparticles (AuNPs) at low temperature in short reaction times. The nanoparticles obtained have different sizes and are a function of the synthesis temperature, presenting by Uv–vis spectrocopy the characteristic band at 540 nm of the surface plasmon of the Au nanoparticles. By electron diffraction it was determined that the phase they show is cubic centered on the face, in addition, the AuNps, when impregnated with TiO2, show a strong photocatalytic activity for the reduction of CO2 to other products.
•The change of the medium during the synthesis causes a change in the obtained morphology of TiO2.•The best symmetry of the TiO2 allows a better absorption of the H2O molecules.•The local electronic ...density is related in a strong way with the adsorption rate.
Nowadays emerge a need to obtain materials highly photoactive for different applications such as optoelectronics, contaminant removal or energy production, all of them are priority need to reach sustainable development. Nevertheless, this depends of several factors such as the synthesis method choice can affect the form and structure of final samples. In this report, we present the TiO2 synthesis in anatase phase at 400 °C with different morphologies due to interrelation between acid used during the synthesis and some kinds of glycinates generated. The probable mechanisms for formation of TiO2 nanoparticles and morphology control are discussed. The correspond characterization by means of Scanning Electron Microscopy and Transmission Electron Microscopy, XRD, superficial area reveals that physiochemical properties obtained improve the photocatalytic water splitting hydrogen production. The samples show best photoactivity when these adopt spherical morphology because of a change of electronic densities. On the other hand, DFT calculations were carried out on (TiO2)n n = 15–20 clusters to evaluate the water adsorption and to verify that systems with best symmetry are favored over irregular structures as well as to give a weakening tendency on O − H bonds of waters molecules attached to these semiconductor nanoparticles.
The obtaining of monocrystalline TiO2 nanofibers with high specific surface area synthesized by the electrospinning technique with controlled crystalline structure and morphology is reported. The ...nanofibers were annealed at 500, 700 and 900 °C in a controlled atmosphere in the presence of air for two hours to achieve crystalline phase transformation. By means of TEM, it was possible to clearly corroborate the presence of solid nanofibers with a well-defined shape, a smooth surface and without the presence of interconnections and defects called beads. The chemical stoichiometry of electrospun TiO2 nanofibers was estimated by EDS, finding that at low annealing temperatures excess of oxygen was detected and at high temperatures excess of titanium that originates oxygen vacancies. By Raman scattering was found that the TiO2 nanofibers showed a crystalline phase transformation from pure anatase, mixed anatase-rutile and pure rutile as the annealing temperature is increased, caused by the generation of oxygen vacancies, which was corroborated by X-ray diffraction. The band gap energy (Eg), obtained from optical absorption spectra, decreases as the temperature is increased, which is ranged in 2.42 ≤ Eg≤ 3.27 eV, caused by the anatase→rutile crystalline phase transformation. Photoluminescence shows that the radiative bands -present a gradual red shift as the temperature increases due to the Eg reduction. In addition, the photocatalytic properties of the annealed TiO2 nanofibers were evaluated in the decolouration of the Remazol Black B azo dye. Changes in absorption spectra were noticeable as the measurement time increases. Absorbance spectra showed a decrease in the intensity of the main absorption band at 589 nm, which gradually decreases until it completely disappears, indicating that the decomposition of the organic compound is complete, while physically there is an absence of color from the solution. The anatase crystalline phase was the one with the highest specific surface area and the highest photocatalytic activity.
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It shows the X-ray diffraction patterns of TiO2 nanofibers at different annealing temperatures: a) anatase crystalline phase (AT=500 °C), b) anatase-rutile mixed (AT=700 °C) and c) rutile phase.
•TiO2 nanofibres were successfully synthesized by electrospinning technique at 300 K.•Crystal phase transformation through high-temperature annealing of TiO2 nanofibres.•The spectrospun TiO2 crystalline phase transformation is caused by oxygen vacancies.
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•A new method of synthesis of gold nanoparticles at low temperature.•The extracts of the xerophytic plant can reduce Au(III) to Au (0) in a few minutes.•The NPsAu showed high ...stability with potential for biological applications.
Gold nanoparticles were synthetized in short time by a novel and easy method by using an aqueous extract from Agave potatorum. The UV–Vis data show a characteristic band at 540 nm, from the minute 2 of synthesis that intensifies through the reaction time advances, by X-Ray diffraction and Selected Area Electron Diffraction (SAED), it is demonstrated the polycrystallinity of the samples, exhibiting the specific features of metallic gold; the Transmission Electron Microscopy (TEM) results show pseudospherical nanoparticles with an average size of 14 nm corresponding to the synthesized samples at 10 min and 22 nm in the case of the synthesized samples at 20 min. The results suggest that the Agave extract works also as stabilizer.
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•A new method for nanoparticles at low temperature and short reaction time.•The cyanidine-O-3-glucoside can reduce Cu(II) from CuCl2 to Cu (0), forming nanoparticles.•The CuNPs showed ...strong inhibitory power on the growth of Gram (+) and Gram (−).
Cu nanoparticles (CuNPs) were biosynthesized by green nanotechnology and they showed a inhibitory power on the growth of Gram (+) and Gram (−). CuNPs synthesis (0) was performed at 65 °C from a solution of copper chloride and using as reducing cyanidine-O-3-glucoside, selectively obtained from the skin of red plum (Pronus domestic). Their characterization has shown typical UV–Vis bands, Cu nanoparticles refers to surface plasmon resonance (SPR) at 550 nm. Structural analysis by HRTEM evidence growth is in the (1 1 1) plane of the fcc phase of metallic Cu, with a size close to 10 nm, with a quasi-spherical morphology, due to the role as surfactant of the cyanidine-O-3-glucoside for the preparation of metal nanoparticles.
► The ultrasonic method is a sustainable route to prepare new materials. ► Crystalline NaTaO3 with monoclinic phase has been successfully synthesized. ► Physicochemical characterizations revealed ...nanoparticles and bad gap near 3.8eV. ► NaTaO3 is more photo-sensible compared with its counterpart obtained by solid-state.
NaTaO3 perovskite-like materials were synthesized using sodium acetate and tantalum ethoxide as precursors in an ultrasonic bath at room temperature. The pristine sample was thermally treated at 600°C and characterized using XRD, N2 physisorption, DRS, SEM and TEM techniques. The structural characterization by X-ray powder diffraction revealed that the crystallization of the NaTaO3 phase prepared at 600°C showed agglomerates sizes in the micrometric scale, as confirmed by scanning electron microscopy (SEM). On the other hand, well-defined NaTaO3 particles in the nanometric scale were determined using TEM. It was found that, for the treated sample, the band gap and BET area was 3.8eV and 9.5m2g−1, respectively. The annealed perovskite, deposited onto ITO glass, presented an important variation in the open circuit potential transient during UV light irradiation in neutral solution, compared with its counterpart prepared by solid-state method. These intrinsic properties, given by the preparation route, might be appropriate for increase its photocatalytic activity.
The photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under visible light exposure was studied using TiO2 and TiO2 doped with nitrogen (1% and 5%) that was prepared by the sol–gel ...(SG) and sonochemistry (SQ) methods. In fact, the sonochemical route represents a sustainable alternative for saving energy during the synthesis. The results show that the half-life time (t1/2) was 71 min for the 5% N–TiO2 photocatalyst prepared by the SQ. According to XRD results, semi-crystalline TiO2 was obtained using both synthetic routes at 400 °C. However, the presence of a dopant using the SG method causes an increase in the crystallinity of the TiO2 materials prepared, and the crystallinity of the SQ route is inhibited at higher nitrogen content. The XPS data showed the presence of nitrogen (398–401 eV) in synthesized TiO2. The results of the band gap energy (Eg) using a Kubelka–Munk transformation indicate that both methods of synthesis show higher absorbances when nitrogen was incorporated into the matrix of TiO2, leading to the decrease of Eg from 3.2 eV to 3.0 eV. The TEM analysis shows that the nanoparticles were obtained with sizing less than 40 nm, and the incorporation of nitrogen causes a decrease in the particle size. Finally, the surface properties are consistent with the observed crystallinity in the materials.
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► Two routes to incorporate urea as nitrogen precursor at TiO2 were studied. ► Nitrogen incorporation modifies the band gap energy at TiO2 structure. ► The doped materials are driven in visible light. ► Sonochemical enhances photodegradation in comparison with sol–gel method. ► 2,4-Dichlorophenoxyacetic is proposed as main degradation reaction.
In this work, gold nanoparticles (AuNPs) were synthesized from extracts of Agave potatorum leaves using three solvents with different polarities (water, ethanol, and hexane) for the extraction of ...phytochemicals from the biomass of Agave potatorum. The different biosynthesized nanoparticles were microstructurally characterized using UV–Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy lower secondary electrons (LEI-SEM), and X-ray diffraction (XRD). UV–Vis spectra analysis revealed clear surface plasmon resonance (SPR) signals close to 540 nm showing differentiation according to the metabolites present in the extract used, as well as TEM micrographs showing different average sizes of nanoparticles according to the extract used, and XRD results provided evidence of the metallic character of the synthesized nanoparticles. The results showed a strong relationship between synthesis times, crystallinity, and the metabolites in each extract.
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•A simple method to control the growth rate of synthesized Au NPs.•The solidarity of the extraction solvent allows the extraction of specific metabolites.•The combination of metabolites drives the rate of reduction from Au (III) to Au (0).
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•Hydrogen production by water splitting was reported using RuO2-Zr/Na2Ti6O13 as a photocatalyst.•2%Ru:Zr/Na2Ti6O13 shows a good activity and stability for hydrogen evolution.•The ...improvement on the catalytic activity of the impregnated materials suggested a synergistic effect between the Zr and RuO2, which acted like an electron trap.
Na2Ti6O13 and Zr/Na2Ti6O13 prepared by the sol–gel method and impregnated with different amounts of RuO2 (0.1–10wt%) were evaluated as photocatalysts for water splitting. The calcined materials at 800°C were characterized by X-ray diffraction (XRD) analysis, Raman spectroscopy, UV–vis spectroscopy with diffuse reflectance spectroscopy (DRS), N2 physisorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The physicochemical characterization confirmed that both materials had the tunnel structure. However, the Zr/Na2Ti6O13 sample revealed high Zr dispersion. The ideal amount of RuO2 to load the samples with was shown to be 2.0wt %, which produced hydrogen at a rate of 265μmolh−1. The apparent quantum yield efficiency was 21%. The improvement on the catalytic activity of the impregnated materials suggested a synergistic effect between the Zr and RuO2, which acted like an electron trap.
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