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This study explores the use of in situ electrochemical process to regenerate granular activated carbon (GAC) loaded with carbendazim (CBZ) and simultaneously oxidize the contaminant. The experiment optimized the flow rate ($Q$ Q), current density ($j$ j), cathodic or anodic chamber, and electrolyte type to achieve the best results. The study found that using GAC in the cathodic chamber and NaCl as a supporting electrolyte, with a $j$ j = 0.5 mA cm−2, and $Q$ Q = 100 L h−1, led to a 64% regeneration with an energy consumption of 0.15 kWh kg−1, which is at least 16× lower than those found in the literature for electrochemical, microwave and thermal processes. Consecutive regeneration tests revealed a decrease in GAC adsorptive capacity over time due to blockage by transformation products, and mainly by oxidation-induced changes in pore structure, as confirmed in dissolved organic carbon (DOC), scanning electron microscopy (SEM), and surface area results. The results also showed that in all tested conditions, residual CBZ was not found in the electrolyte solution. Overall, electrochemical regeneration proved to be an energy-efficient method for extending the lifespan of GAC and minimizing disposal in landfills. [ABSTRACT FROM AUTHOR]

In this study, we report on the optical and magnetic properties of Co-doped ZnO nanoparticles with increasing Co-content (CoxZn1-xO; x=0.000, 0.005, 0.010, 0.030, 0.050, 0.070, and 0.100) synthesized by the combustion reaction method. The X-ray diffraction patterns and the Raman spectra of all samples indicated the formation of the ZnO hexagonal wurtzite phase (space group C4 6V). The Raman data also show the formation of a secondary Co3O4 phase, which is barely seen in the X-ray spectra. Photoacoustic spectroscopy and electron paramagnetic resonance confirm the presence of the two phases (CoxZn1-xO and Co3O4). Vibrating sample magnetometer measurements performed at room temperature exhibited hysteresis loops, indicating the presence of long-range magnetic ordering in the samples. Analysis of the magnetization as a function of magnetic field and temperature shows that the ferromagnetism in the as-synthesized samples comes from small Cometallic inclusions, with an estimated radius of about 4.8 nm and blocking temperature around 595 K. [ABSTRACT FROM AUTHOR]

In this work, we present a coupled experimental and theoretical first-principles investigation on one of the more promising oxide-diluted magnetic semiconductors, the Sn1−xCoxO2 nanoparticle system, in order to see the effect of cobalt doping on the physical and chemical properties. Our findings suggest that progressive surface enrichment with dopant ions plays an essential role in the monotonous quenching of the surface disorder modes. That weakening is associated with the passivation of the oxygen vacancies as the Co excess at the surface becomes larger. Room-temperature 119Sn Mössbauer spectroscopy data analysis revealed the occurrence of a distribution of isomer shifts, related to the different non-equivalent surroundings of Sn4+ ions and the coexistence of Sn2+/Sn4+ at the particle surfaces provoked by the inhomogeneous distribution of Co ions, in agreement with the X-ray photoelectron spectroscopy measurements. Magnetic measurements revealed a paramagnetic behavior of the Co ions dispersed in the rutile-type matrix with antiferromagnetic correlations, which become stronger as the Co content is increased. Theoretical calculations show that a defect with two Co mediated by a nearby oxygen vacancy is the most likely defect. The predicted effects of this defect complex are in accordance with the experimental results. [ABSTRACT FROM AUTHOR]

The effects of optically exciting n-type and p-type one-side modulation-doped InGaAs/GaAs quantum well structures were investigated by scanning the photoluminescence intensity profile on the sample’s surface. An undoped quantum well was used as reference. Photoluminescence and carrier diffusion length measurements were carried out at increasing optical excitation densities. We found that the excitation density dependence of the carrier diffusion length in doped samples is quite different from that of the undoped sample. This difference is discussed in terms of the reduction of band bending/band-gap renormalization and carrier lifetime change due to the reduction of the two-dimensional carries gas density inside the quantum well upon intense laser illumination. [ABSTRACT FROM AUTHOR]

A systematic study is presented of continuous wave (cw) photoluminescence (PL) of self-assembled quantum dots (QDs) grown on GaAs (001) by molecular-beam epitaxy as a function of excitation intensity and QD density. The sample used in this work was grown under nonisotropic indium flux that resulted in a QD density gradient across the sample surface ranging from 0 to 1.8 × 10[sup 11] cm[sup -2]. The carrier kinetics in the sample is described by a set of coupled rate equations through which the cw PL data from the GaAs barrier, wetting layer (WL), and QDs were simulated as a function of the excitation intensity and QD density. By comparing the PL data with our simulations we infer that carrier capture into the QD occurs directly from GaAs barrier. Auger and phonon-assisted carrier capture from the WL were found to give negligible contribution. With an increase of the QD density we observe an increase of the nonradiative recombination rates of the barrier and at the WL, which we tentatively correlate with the increase of surface and interface recombination rates. Furthermore, we noticed that the variation of the coefficients used in our model in order to simulate the experimental results over the entire QD density range studied is strongly correlated with the changes in sample morphology. In particular, the behavior of the capture rate as a function of the QD density allowed us to determine a QD capture cross section from the GaAs barrier equal to 1.5 × 10[sup -11] cm². [ABSTRACT FROM AUTHOR]

Provides information on a study that examined the crystallization process of amorphous GaSb films prepared by flash evaporation via Raman scattering. Experimental procedure; Results and discussion on the study; Conclusions.

Focuses on a study which performed comparative Raman measurements of gallium and nitrogen epitaxial layers. Observation on the hexagonal and cubic layers of gallium and nitrogen; Discussion of the hexagonal frequencies of gallium; Lattice dynamics of zincblende and wurtzite crystals.

Raman spectroscopy is used to investigate magnetite nanoparticles pre-coated with oleoylsarcosine and dispersed as stable water-based (WB) and hydrocarbon-based (HB) magnetic fluids (MF's). The Raman spectra obtained from the MF samples and from liquid water were compared and the data discussed in terms of the suppression of the symmetrical hydroxyl (OH) vibrational modes. The effective grafting coefficient of the oleoylsarcosine in the WB-MF, with respect to the HB-MF, was estimated through the OH-stretching Raman modes of the OH-group chemisorbed at the nanoparticle surface. It was found that the OH-grafting coefficient in the HB-MF sample is about 3 times lower than the grafting coefficient in the WB-MF sample. Index Terms--Ferrites, magnetic fluids, nanocrystalline materials, Raman spectroscopy.

Samples of ZnxMg1-xFe2O4 (0⩽x⩽1) synthesized by the combustion reaction method were investigated by x-ray diffraction, Mössbauer spectroscopy, and Raman spectroscopy. All the samples are found to have a cubic spinel structure and the lattice parameter increases linearly with increasing Zn-content (x). The Mössbauer data showed that the replacement of Mg2+ ions for Zn2+ ions changes substantially the hyperfine parameter. Moreover, it was verified the presence of Fe3+ ions both in A and B sites. The Raman spectra showed five predicted Raman bands for the spinel structure and it was observed the splitting of the A1g Raman mode into tree branches, where each one have been attributed to peaks belonging to each ion (Zn, Mg, and Fe) in the tetrahedral positions. [ABSTRACT FROM AUTHOR]

CoxFe3-xO4-based (x=0.05–1.6) nanoparticles prepared by combustion reaction were investigated using x-ray diffraction, Raman spectroscopy, and Mössbauer spectroscopy. The Mössbauer data revealed Co2+ in both tetrahedral (site A) and octahedral (site B) sites of the cubic ferrite structure. For x≤0.4 the experimental data indicated the synthesis of a core-shell structure, with hematite as the shell and cobalt ferrite as the core of the nanoparticle. Differences in crystalline structure between the two phases support the evidences we found of a highly stressed core-shell interface, leading to symmetry reduction of the tetrahedral and octahedral sites. [ABSTRACT FROM AUTHOR]

CoxFe3-xO4-based (x=0.05–1.6) nanoparticles prepared by combustion reaction were investigated using x-ray diffraction, Raman spectroscopy, and Mössbauer spectroscopy. The Mössbauer data revealed Co2+ in both tetrahedral (site A) and octahedral (site B) sites of the cubic ferrite structure. For x≤0.4 the experimental data indicated the synthesis of a core-shell structure, with hematite as the shell and cobalt ferrite as the core of the nanoparticle. Differences in crystalline structure between the two phases support the evidences we found of a highly stressed core-shell interface, leading to symmetry reduction of the tetrahedral and octahedral sites. [ABSTRACT FROM AUTHOR]