- Computational Materials Physics, Nanoscience & Nanotechnology, Advanced Materials, Synthesis of nanoparticles, Shape and Control of Metallic Nanoparticles, Surface Science Phenomena (STM Imaging of Molecular Magnetic Systems, Electronic Transport In Molecules, and 6 moreSmall Supported Clusters on Metal Oxide Surfaces), Nanocatalysis, Platonic Solids, Surface Reconstruction, Synthesis and Characterization of nanomaterials, and Autopoiesisedit
2 Abstract: We present a study of a system composed of a scanning tunneling microscope (STM) tip coupled to an absorbed impurity on a host surface using the functional renormalization group (FRG). We include the effect of the STM tip as a... more
2 Abstract: We present a study of a system composed of a scanning tunneling microscope (STM) tip coupled to an absorbed impurity on a host surface using the functional renormalization group (FRG). We include the effect of the STM tip as a correction to the self-energy in addition to the usual contribution of the host surface in the wide band limit. We calculate the differential conductance curves at two dif- ferent lateral distances from the quantum impurity and find good qualitative agree- ment with STM experiments where the differential conductance curves evolve from an antiresonance to a Lorentzian shape.
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ABSTRACTIn this work we present the bases to perform investigation on the effects on the morphology and size of nanostructures of silver, owed to the modification of synthesis factors in a polyol process such as temperature,... more
ABSTRACTIn this work we present the bases to perform investigation on the effects on the morphology and size of nanostructures of silver, owed to the modification of synthesis factors in a polyol process such as temperature, concentration, time of reaction, injection speed and time of injection. It is claimed that control over Ag nanostructures shape could be improved and significant information about the synthesis process can be obtained. The design of experiments was done aimed to obtain useful information about how to yield as much as possible specific structures of interest.
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Pure Ca2Ba3(PO4)3Cl and rare earth ion (Eu(2+)/Ce(3+)/Dy(3+)/Tb(3+)) doped Ca2Ba3(PO4)3Cl phosphors with the apatite structure have been prepared via a Pechini-type sol-gel process. X-ray diffraction (XRD) and structure refinement,... more
Pure Ca2Ba3(PO4)3Cl and rare earth ion (Eu(2+)/Ce(3+)/Dy(3+)/Tb(3+)) doped Ca2Ba3(PO4)3Cl phosphors with the apatite structure have been prepared via a Pechini-type sol-gel process. X-ray diffraction (XRD) and structure refinement, photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, absolute quantum yield, as well as lifetimes were utilized to characterize samples. Under UV light excitation, the undoped Ca2Ba3(PO4)3Cl sample shows broad band photoluminescence centered near 480 nm after being reduced due to the defect structure. Eu(2+) and Ce(3+) ion doped Ca2Ba3(PO4)3Cl samples also show broad 5d → 4f transitions with cyan and blue colors and higher quantum yields (72% for Ca2Ba3(PO4)3Cl:0.04Eu(2+); 67% for Ca2Ba3(PO4)3Cl:0.016Ce(3+)). For Dy(3+) and Tb(3+) doped Ca2Ba3(PO4)3Cl samples, they give strong line emissions coming from 4f → 4f transitions. Moreover, the Ce(3+) ion can transfer its energy to the Tb(3+) ion in the Ca2Ba3(PO4)3Cl host, and the energy transfer mechanism has been demonstrated to be a resonant type, via a dipole-quadrupole interaction. However, under the low voltage electron beam excitation, Tb(3+) ion doped Ca2Ba3(PO4)3Cl samples present different luminescence properties compared with their PL spectra, which is ascribed to the different excitation mechanism. On the basis of the good PL and CL properties of the Ca2Ba3(PO4)3Cl:A (A = Ce(3+)/Eu(2+)/Tb(3+)/Dy(3+)), Ca2Ba3(PO4)3Cl might be promising for application in solid state lighting and field-emission displays.
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Research Interests: Materials Science, Nanoparticle, Nanoparticles, Chemical Physics, Medicine, and 10 moreComputer Simulation, Surface, TEM, Physical sciences, Shape and Structure of Nanoparticles, Binary clusters, Surface Reconstruction, Energy Stability of Metallic Nanoparticles, Enseñanza - Aprendizaje Ciencias Naturales Y Exactas, and Ciencias Fisicas
Mesoporous silica-based nanomaterials have been considered as potential carriers for drug delivery applications. Their main advantages are: i) tunable pore size, ii) high surface area, iii) functional surface chemistry and iv)... more
Mesoporous silica-based nanomaterials have been considered as potential carriers for drug delivery applications. Their main advantages are: i) tunable pore size, ii) high surface area, iii) functional surface chemistry and iv) biocompatibility. The internal and external domains of mesoporous silica allow encapsulating a wide variety of drugs and functionalizing its surface with specific molecules in the perspective of targeting medicine. In this work, we synthetized and characterized the silica-based mesostructures known as SBA-15 and MSF. We highlighted their pore size distribution, functional surface chemistry and loading capacity using valproic acid as probe. We observed that the SBA-15 sample has an average pore size of about 6 nm, while the modified MSF sample has an average pore size of 13 nm. These are encouraging results demonstrating that the use of swelling agents allows increasing the pore size distribution and thus the applicability of MSF as drug carries. The surface functionalization, using liposomes, was successfully achieved. This last may play a key role in the presence of living cells, enhancing the uptake. The more efficient material was the MSF, which encapsulated a higher VPA amount. Hence, the loading capacity was found pore size dependent. This work is the proof-of-concept of the use of MSF as biocompatible and effective drug delivery system.
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We report a facile approach to synthesise small Au–Ag alloyed nanoparticles using a new cali[8]arene derivative as a stabiliser.
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In this work we present a comparison of the properties of three tin selenide (SnSe) thin films synthesized by electrodeposition under air or nitrogen atmosphere. The films were synthesized at -0.7 V, -0.8 V, and -0.9 V vs. Ag/AgCl using a... more
In this work we present a comparison of the properties of three tin selenide (SnSe) thin films synthesized by electrodeposition under air or nitrogen atmosphere. The films were synthesized at -0.7 V, -0.8 V, and -0.9 V vs. Ag/AgCl using a fluorine doped tin oxide conductive glass as working electrode, a silver chloride electrode as reference electrode, and a platinum mesh as counter electrode. After the electrodeposition, films were heated at 55°C for 30 minutes in air atmosphere. Films without and with thermal treatment were characterized by UV-Visible Spectroscopy, Atomic Force Microscopy, and Raman Spectroscopy. Analyzing the results, it was found that the optimal conditions for the electrodeposition were at -0.8 V vs Ag/AgCl. Band gap values were in the range from 1.2 to 1.5 eV. Raman spectroscopy revealed characteristic vibrational modes of SnSe and SnSe2 materials. The analysis by Atomic Force Microscopy revealed grain size of 100-700 nm.
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Silver and gold nanoparticles were synthesized under environmentally-friendly reaction conditions by using a biodegradable copolymer and water as a solvent. The triblock copolymer Pluronic P103 was utilized as a stabilizing agent or soft... more
Silver and gold nanoparticles were synthesized under environmentally-friendly reaction conditions by using a biodegradable copolymer and water as a solvent. The triblock copolymer Pluronic P103 was utilized as a stabilizing agent or soft template to produce Ag and Au nanoparticles (NPs) of different sizes. Moreover, in the synthesis of Au NPs, the polymer acted as a reducing agent, decreasing the number of reagents used and consequently the residues produced, hence, rendering the procedure less complicated. It was observed that as the concentration of the polymer increased, the size of the metallic NPs augmented as well. However, AgNPs and AuNPs prepared with 1 and 10 wt% Pluronic P103, respectively, showed a significant decrease in particle size due to the presence of polymeric soft templates. The hybrid materials (metal/polymer) were characterized by UV-Vis spectroscopy, DLS, and TEM. The pre-synthesized nanoparticles were employed to decorate anatase-TiO2, and the composites were...
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To theoretically study the physicochemical properties of nanowires, it is necessary to build the corresponding atomic geometrical models. Here we present the geometrical characteristics of nanowires with fcc, hcp, and polycrystalline... more
To theoretically study the physicochemical properties of nanowires, it is necessary to build the corresponding atomic geometrical models. Here we present the geometrical characteristics of nanowires with fcc, hcp, and polycrystalline structures. We consider fcc and hcp wires grown along the (111) andz axis directions, respectively, with various diameters and lengths. In addition, since staking faults in these systems are very common, we analyze also the case of nanowires formed by stacked pieces having different crystalline structures and orientations, a fact that leads to the formation of several internal interfaces. By performing simulations of transmission electron microscopy (TEM) images and diffraction patterns of the nanowires considered here, we reveal how sensitive are the calculated images to the defocus condition as well as to the orientation of the wire with respect to the incident beam, a result that must be taken into account in order to better understand the measured d...
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Photothermal tumor ablation might be carried out with multibranched gold nanoparticles (MBAuNPs) having maximum absorbance (Amax) in the infrared region and functionalized with ligands that would bind them to the target tumor markers.... more
Photothermal tumor ablation might be carried out with multibranched gold nanoparticles (MBAuNPs) having maximum absorbance (Amax) in the infrared region and functionalized with ligands that would bind them to the target tumor markers. However, in nanomedicine applications, the nanostructures must reach their target tissues to be effective, but the corona of serum proteins they instantaneously acquire when administered by intravenous injection may affect their activity; for this reason, we decided to analyze the effect that exposing MBAuNPs to bovine serum albumin (BSA) and human serum (HS) have on their protein corona and physical properties. The synthesized spherical Au seeds stoichiometrically generate pinata-like MBAuNPs of 8–20 peaks potentially useful for photothermal tumor ablation since they induce hyperthermia of more than 4 °C in phantom gels mimicking the skin irradiated with an 808 nm laser at 0.75 W/cm2. The calculated surface area of MBAuNPs ranges from 24 984 nm2 to 40...
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Abstract The incorporation of Er 3+ ions in the CaTiO 3 structure provides an enhanced H 2 photoproduction due to the formation of long-lived charge-carriers in the semiconductor. Nitroblue tetrazolium reaction, photoluminescence and time... more
Abstract The incorporation of Er 3+ ions in the CaTiO 3 structure provides an enhanced H 2 photoproduction due to the formation of long-lived charge-carriers in the semiconductor. Nitroblue tetrazolium reaction, photoluminescence and time resolved microwave conductivity techniques were used to investigate the generation of the superoxide species and the lifetime of the charge-carriers. The improved photoactivity has been explained in terms of the dopant agent, finding that phenomena such as a higher concentration of the superoxide radicals, a more efficient separation of the photogenerated charge-carriers, and a slower recombination process take place in the Er 3 + doped CaTiO 3 compared to the undoped CaTiO 3 .
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Ag and CuO nanoparticles (NPs) synthesized on the surface of commercial TiO2 (P25) by radiolytic reduction were characterized by diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), high-angle annular dark-field... more
Ag and CuO nanoparticles (NPs) synthesized on the surface of commercial TiO2 (P25) by radiolytic reduction were characterized by diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). In the case of modification with silver and copper, results from HAADF-STEM, EDS, XPS, and XAS show that Ag@CuO nanoparticles (large silver cores decorated with small clusters of CuO) were obtained on TiO2–P25. The photocatalytic properties of bare and modified TiO2–P25 were studied for phenol photodegradation and for acetic acid oxidation under UV and visible irradiation. The mechanisms involved in photocatalysis were studied by time-resolved microwave conductivity (TRMC) and action spectra (AS). The electronic properties of the surface-modified TiO2–P25 were studied by TRMC to follow the cha...
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The local orbital magnetic moments Ldelta(i) at different layers i close to the surfaces of Fe, Co, and Ni are determined in the framework of a d-band Hamiltonian, which includes hybridizations, Coulomb interactions, and spin-orbit... more
The local orbital magnetic moments Ldelta(i) at different layers i close to the surfaces of Fe, Co, and Ni are determined in the framework of a d-band Hamiltonian, which includes hybridizations, Coulomb interactions, and spin-orbit coupling on the same electronic level. Different directions of the magnetization delta are considered in order to quantify the anisotropy in L. For each delta, the spin-polarized charge distribution and the local densities of states from which L is derived are calculated self-consistently. The role of the local atomic environment is investigated by performing calculations on the (001), (110), and (111) surfaces of the bcc, hcp, and fcc lattices. Ldelta(i) is significantly enhanced at surface atoms as compared to the corresponding bulk moment Ldelta(bulk). L depends strongly on the local coordination number and is generally larger the more open the surface is. For example, for the Fe(001) surface Lx(1)/Lx(bulk)=2.2 and for the Fe(110) surface Lx(1)/Lx(bulk)=1.3. Ldelta(i) decreases abruptly as we move from the uppermost layer (i=1) to the second layer (i=2). After some oscillations, convergence to Ldelta(bulk) is reached quite accurately for i>=6. The largest anisotropy in Ldelta(i) is found at the hcp (0001) surface of Co (L||-L⊥~=0.02muB). The orbital moments at pure surfaces are compared with results for deposited films by considering four layers of Co on Pd(111) as a representative example.
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To theoretically study the physicochemical properties of nanowires, it is necessary to build the corresponding atomic geometrical models. Here we present the geometrical characteristics of nanowires with fcc, hcp, and polycrystalline... more
To theoretically study the physicochemical properties of nanowires, it is necessary to build the corresponding atomic geometrical models. Here we present the geometrical characteristics of nanowires with fcc, hcp, and polycrystalline structures. We consider fcc and hcp wires grown along the (111) andz axis directions, respectively, with various diameters and lengths. In addition, since staking faults in these systems are
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Research Interests: Engineering, Physics, Chemistry, Technology, Synthesis of nanoparticles, and 11 moreMolecular Dynamics Simulation, Gold Nanoparticles, Nucleation, Nucleation and Growth, The, Shape and Structure of Nanoparticles, Optical properties of Au Nanoparticles, CHEMICAL SCIENCES, Room Temperature, Molecular Dynamic Simulation, and Molecular dynamic
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There is strong interest in studying changes in mechanical properties with reducing grain size. The rational is that consequent dislocation glide cannot be sustained, resulting in an increase in material strength. However, this comes with... more
There is strong interest in studying changes in mechanical properties with reducing grain size. The rational is that consequent dislocation glide cannot be sustained, resulting in an increase in material strength. However, this comes with the cost of a reduction in ductility. It has been shown that coherent twin boundaries in nanostructured Cu improve the ductility to 14% [Lu et al.,
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Modern nanoparticle research in the field of small metallic systems has confirmed that many nanoparticles take on some Platonic and Archimedean solids related shapes. A Platonic solid looks the same from any vertex, and intuitively they... more
Modern nanoparticle research in the field of small metallic systems has confirmed that many nanoparticles take on some Platonic and Archimedean solids related shapes. A Platonic solid looks the same from any vertex, and intuitively they appear as good candidates for atomic equilibrium shapes. A very clear example is the icosahedral ( I h ) particle that only shows {111} faces that contribute to produce a more rounded structure. Indeed, many studies report the I h as the most stable particle at the size range r≤20 Å for noble gases and for some metals. In this review, we report on the structure and shape of mono- and bimetallic nanoparticles in the wide size range from 1–300 nm. First, we present AuPd nanoparticles in the 1–2 nm size range that show dodecahedral atomic growth packing, one of the Platonic solid shapes that have not been identified before in this small size range for metallic particles. Next, with particles in the size range of 2–5 nm, we present an energetic surface r...
Research Interests: Materials Science, Synthesis and Characterization of nanomaterials, Computer Simulation, Mathematical Sciences, Noble Gases, and 8 morePhysical sciences, Simulation Methods, Surface Reconstruction, Nanoscale Materials and Devices, Spectroscopy and Geo Metrical Structure of Clusters, Molecular Dynamics and Other Simulation Methods, Simulation Model, and Molecular dynamic
Research Interests: Materials Engineering, Genetics, Materials Science, Genetic Algorithms, Carbon Nanotubes, and 10 moreCarbon Nanotube, Genetic Algorithm, Nanowires, Manufacturing Engineering, Global Optimization, Atomic Structure of Nanowires, Dimensional, New materials and manufacturing processes for aero engines, Atomic Structure, and Periodic Structure
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"Introduction: Nanotechnology is a leading interdisciplinary science that is emerging as a distinctive field of research. Its advances and applications will result in technical capabilities that will allow the... more
"Introduction: Nanotechnology is a leading interdisciplinary science that is emerging as a distinctive field of research. Its advances and applications will result in technical capabilities that will allow the development of novel nanomaterials with applications that will revolutionize the industry in many areas. It is now well established that dimensionality plays a critical role in determining the properties of materials, and its study has produced important results in chemistry and physics. Nanoparticles are one of the cornerstones of nanotechnology. Indeed, even though the research in this field has been underway for a long time, many present and future applications are based on nanoparticles. For instance, the electron tunneling through quantum dots has led to the possibility of fabricating single-electron transistors [4–9]. One concept particularly appealing is a new three-dimensional periodic table based on the possibility of generating artificial atoms from clusters of all of the elements [10]. This idea is based on the fact that several properties of nanoparticles show large fluctuations, which can be interpreted as electronic or shell-closing properties with the appearance of magic numbers. Therefore, it is conceivable to tailor artificial superatoms with given properties by controlling the number of shells on a nanoparticle. ... intro continues...."
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A compilation and an implementation of different methodologies to simulate NPT ensembles on finite systems is presented. In general, the methods discussed can be classified in two different groups depending on how the external pressure is... more
A compilation and an implementation of different methodologies to simulate NPT ensembles on finite systems is presented. In general, the methods discussed can be classified in two different groups depending on how the external pressure is applied to the system. The first approach is based on including the pressure with its conjugate thermodynamical variable, the volume, in the Lagrangian of
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ABSTRACT Gold and copper nanoparticles present atomic structures which are either icosahedral (Ih), decahedral (Dh) or octahedral (Oh), depending of the particle size. Some experimental results had previously reported the stabilization of... more
ABSTRACT Gold and copper nanoparticles present atomic structures which are either icosahedral (Ih), decahedral (Dh) or octahedral (Oh), depending of the particle size. Some experimental results had previously reported the stabilization of the Ih phase in AuCu and AuFe clusters, being this phase predominant at 25% copper concentration in both systems. Another result reports an fcc-like and core/shell structure under similar experimental conditions and/or similar systems. In the present work, we study the possible phase conformations and thermal behavior of AuCu binary clusters using classical molecular dynamics simulations with a Sutton and Chen inter-atomic potential, addressing under which conditions the different phases mentioned above take place. To discern between the structures of bimetallic systems, the following main factors are determinant: the cluster size N, the concentration and nature of the elements in the alloy, and the annealing temperature. We choose the particles in our study closed to the sizes reported experimentally, with the cubo-octahedral symmetry as starting point. We have changed the concentration of copper from 50 to 10%, simulating an annealing process around the temperature of 750 K. We have found optimum stability of the icosahedral phase at concentrations of copper around 75 and 25% in fair agreement with experimental reports, and a trend to adopt a quasi-spherical shape with a core/shell structure at high temperatures in the cluster, just before the melting temperature.
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Nanoparticle research disciplines—chemical synthesis, applied physics and devices based on their physical-chemical properties, and computational physics—have been very active fields for the last 15 years or so, because of the potential... more
Nanoparticle research disciplines—chemical synthesis, applied physics and devices based on their physical-chemical properties, and computational physics—have been very active fields for the last 15 years or so, because of the potential and current applications in medicine, catalysis, energy storage, environment and electronics applications. This wide spectrum of disciplines and their applications keep metallic nanoparticles as one of the most promising nanostructures and their research as one of the cornerstones of nanotechnology. In this contribution we present a comprehensive and extended geometrical description for the most common shapes and structures for metallic nanoparticles, as well as experimental results for these geometries with some variations given by truncations.
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In this research we are reporting the treatment of tequila vinasse by a coagulation-flocculation process coupled with heterogeneous photocatalysis using two types of titanium dioxide nanoparticles, i.e., 1) commercial nanoparticles, and... more
In this research we are reporting the treatment of tequila vinasse by a coagulation-flocculation process coupled with heterogeneous photocatalysis using two types of titanium dioxide nanoparticles, i.e., 1) commercial nanoparticles, and 2) nanoparticles synthesized by sol-gel. The efficiency in the elimination of phenol, which is one of the most harmful contaminants in tequila vinasse, was also included in the evaluation of the treatment process. The synthesized titanium dioxide nanoparticles were annealed in air at 400°C for 1 h and were characterized by X-ray diffraction, transmission electron microscopy, ultraviolet-visible and Raman spectroscopy. Anatase phase was observed in both samples, with a crystallite size of 22.5 and 9.8 nm for commercial and synthesized nanoparticles respectively. Tequila vinasse was characterized before and after the treatments by measuring physicochemical parameters such as pH, chemical oxygen demand (COD), color, total suspended solids (TSS), as well...
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In this work, we report the synthesis, characterization and photocatalytic evaluation of visible light active iron-nitrogen co-doped titanium dioxide (Fe 3+-TiO 2−x N x) nanostructured catalyst. Fe 3+-TiO 2−x N x was synthesized using two... more
In this work, we report the synthesis, characterization and photocatalytic evaluation of visible light active iron-nitrogen co-doped titanium dioxide (Fe 3+-TiO 2−x N x) nanostructured catalyst. Fe 3+-TiO 2−x N x was synthesized using two different chemical approaches: sol-gel (SG) and microwave (MW) methods. The materials were fully characterized using several techniques (SEM, UV–Vis diffuse reflectance DRS, X-ray diffraction XRD, and X-ray photoelectron spectroscopy XPS). The photocatalytic activity of the nanostructured materials synthesized by both methods was evaluated for the degradation of amoxicillin (AMX), streptomycin (STR) and diclofenac (DCF) in aqueous solution. Higher degradation efficiencies were encountered for the materials synthesized by the SG method, for instance, degradation efficiencies values of 58.61% (SG) and 46.12% (MW) were observed for AMX after 240 min of photocatalytic treatment under visible light at pH 3.5. With STR the following results removal efficiencies were obtained: 49.67% (SG) and 39.90% (MW) at pH 8. It was observed the increasing of degradation efficiencies values at longer treatment periods, i.e., after 300 min of photocatalytic treatment under visible light, AMX had a degradation efficiency value of 69.15% (MW) at pH 3.5, DCF 72.3% (MW) at pH 5, and STR 58.49% (MW) at pH 8.
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In this work, we report the synthesis, characterization and photocatalytic evaluation of visible light active iron-nitrogen co-doped titanium dioxide (Fe 3+-TiO 2−x N x) nanostructured catalyst. Fe 3+-TiO 2−x N x was synthesized using two... more
In this work, we report the synthesis, characterization and photocatalytic evaluation of visible light active iron-nitrogen co-doped titanium dioxide (Fe 3+-TiO 2−x N x) nanostructured catalyst. Fe 3+-TiO 2−x N x was synthesized using two different chemical approaches: sol-gel (SG) and microwave (MW) methods. The materials were fully characterized using several techniques (SEM, UV–Vis diffuse reflectance DRS, X-ray diffraction XRD, and X-ray photoelectron spectroscopy XPS). The photocatalytic activity of the nanostructured materials synthesized by both methods was evaluated for the degradation of amoxicillin (AMX), streptomycin (STR) and diclofenac (DCF) in aqueous solution. Higher degradation efficiencies were encountered for the materials synthesized by the SG method, for instance, degradation efficiencies values of 58.61% (SG) and 46.12% (MW) were observed for AMX after 240 min of photocatalytic treatment under visible light at pH 3.5. With STR the following results removal efficiencies were obtained: 49.67% (SG) and 39.90% (MW) at pH 8. It was observed the increasing of degradation efficiencies values at longer treatment periods, i.e., after 300 min of photocatalytic treatment under visible light, AMX had a degradation efficiency value of 69.15% (MW) at pH 3.5, DCF 72.3% (MW) at pH 5, and STR 58.49% (MW) at pH 8.