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The analysis of metals in aquatic organisms is of great importance due to the health problems they can cause to be consumed by human beings. In this study, the Laser-Induced Plasma Spectroscopy (LIBS) technique is evaluated as an alternative method to identify Cu in Crassostrea virginica oysters’ tissue. It focuses on the characterization of oysters caught a natural bank and the identification of different Cu concentrations. To carry out experimentation, oyster samples were collected in autumn (October 2017) and spring (May 2018) from San Andres Lagoon, Aldama, Tamaulipas. A single pulse Nd:YAG laser (1064 nm) was used, and tissue was contaminated with 0, 2, 10, 20, 50, and 100 μg/g of Cu. In tissue were identified atomic lines for Ca, Cr, Mg, Mn, Na, N, O, and H. However, the intensities of emission lines for autumn samples were greater than spring samples. Cu emission lines at 324.6, 327.1, 510.3, 515.1, and 521.5 nm were found for contaminated pills. The intensity of emission lines showed a linear increase with the concentration; whereby, they can be used as calibration curves to quantify Cu concentrations in oyster tissue.

In this work, ZnO films were deposited on titanium substrates by the sputtering technique for non-enzymatic glucose detection in an alkaline solution. The samples were grown using pulsed D.C. sputtering using a ZnO target; we remain constant the power at 100 W and varied the deposition time in order of obtain films with different thickness. The properties of the samples were analyzed by X-ray diffraction (XRD), optical transmission, scanning electron microscopy (SEM), and electrochemical techniques. The results shown that the thickness of the samples varied with the deposition time. The electrochemical response studied by cyclic voltammetry revealed that the sensor response increased when the ZnO film thickness decreased. The electrochemical biosensing device showed a sensitivity of 7.65 ?A cm-2mM-1 with a linear response range of 3.3 mM to 11.0 mM.

We report the synthesis of AlN hexagonal thin films by pulsed laser ablation, using Al target in nitrogen ambient over natively-oxidized Si (111) at 600°C. Composition and chemical state were determined by X-ray photoelectron spectroscopy (XPS); while structural properties were investigated using X-ray diffraction (XRD). High-resolution XPS spectra present a gradual shift to higher binding energies on the Al2ppeak when nitrogen pressure is incremented, indicating the formation of the AlN compound. At 30 mTorr nitrogen pressure, theAl2p peak corresponds to AlN, located at 73.1 eV, and the XRD pattern shows a hexagonal phase of AlN. The successful formation of the AlN compound is corroborated by UV-Vis reflectivity measurements.

ZnO: Al thin films were deposited by spray pyrolysis onto glass substrates with 0, 0.5, 1.0, 2.0, 5.0 and 10.0% [Al3+/Zn2+] ratios in the deposition solution. Films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, UV–vis transmittance, conductive atomic force microscopy and the sheet resistance was measured. Aluminum contents in the films increases with the Al3+/Zn2+ ratio in the bath while the film deposition rate decreases due to the lower Al3+ surface mobility. Films were crystalline and display a varied morphology that evolves from flakes to mixtures between flakes and pencils and finally between triangles and hexagonal columns with increasing Al contents. Al3+ inclusion at the different sites within the ZnO lattice is proposed to direct the crystal habit and therefore the observed morphology and film texture. The optical band gap evolution and carrier density are related by the Burstein-Moss effect. The results show that film texture influences carrier mobility: increased presence of (112) planes originate a mobility increase while a predominant (110) or (100) texture reduces it. By Current sensing Atomic Force Microscopy (CAFM) the local surface current distribution was related with the observed film texture.

In the last decade, the urgent need to environmental protection has promoted the development of new materials with potential applications to remediate air and polluted water. In this work, the effect of the TiO2 thin layer over MoS2 material in photocatalytic activity is reported. We prepared different heterostructures, using a combination of electrospinning, solvothermal, and spin-coating techniques. The properties of the samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRS), and X-ray photoelectron spectroscopy (XPS). The adsorption and photocatalytic activity were evaluated by discoloration of rhodamine B solution. The TiO2-MoS2/TiO2 heterostructure presented three optical absorption edges at 1.3 eV, 2.28 eV, and 3.23 eV. The high adsorption capacity of MoS2 was eliminated with the addition of TiO2 thin film. The samples show high photocatalytic activity in the visible-IR light spectrum.

A novel procedure based on the use of the Boltzmann equation to model the x parameter, the film deposition rate, and the optical band gap of BaxSr1−xTiO3 thin films is proposed. The BaxSr1−xTiO3 films were prepared by RF cosputtering from BaTiO3 and SrTiO3 targets changing the power applied to each magnetron to obtain different Ba/Sr contents. The method to calculate x consisted of fitting the angular shift of (110), (111), and (211) diffraction peaks observed as the density of substitutional Ba2+ increases in the solid solution when the applied RF power increases, followed by a scale transformation from applied power to x parameter using the Boltzmann equation. The Ba/Sr ratio was obtained from X-ray energy dispersive spectroscopy; the comparison with the X-ray diffraction derived composition shows a remarkable coincidence while the discrepancies offer a valuable diagnosis on the sputtering flux and phase composition. The proposed method allows a quick setup of the RF cosputtering system to control film composition providing a versatile tool to optimization of the process.

• The amorphous and crystalline fractions in raw corn pericarp were obtained by sequential extraction.

An estimation of climatological fields of incident solar energy in Tamaulipas State, northeastern Mexico, is presented. Monthly mean evolution of solar energy in 7 automatic meteorological stations distributed along the State shows that the maximum values generally exceed 500 ± 200 W m−2 during fall-winter (Nov–Feb), and 700 ± 200 W m−2 during spring-summer (May–Aug). An empirical model, which estimates the solar energy as function of other climatic variables (minimum temperature, maximum temperature, evaporation, and precipitation) recorded in 165 climatological conventional stations, is used to extend the climatological solar-energy estimate in the study area. The mean values of both measured and estimated solar energy are objectively mapped to fill the observation gaps and reduce the noise associated with inhomogeneous statistics and estimation errors. The highest values of solar energy ( ∼ 6.7 kW h m−2 during the summer and ∼ 4.0 kW h m−2 during the winter) are observed in the highlands, southwestern part of the State, whereas the lowest values ( ∼ 5.7 kW h m−2 during the summer and ∼ 2.8 kW h m−2 during the winter) are observed in the south-central part of the State.

The local electrical response in alkaline-doped CuInSe2 films prepared by single-step electrodeposition onto Cu substrates was studied by current-sensing atomic force microscopy. The CuInSe2 (CIS) films were prepared from single baths containing the dopant ions (Li, Na, K or Cs) and were studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and photocurrent response. Increased crystallinity and surface texturing as the ion size increased were observed, as well as an enhanced photocurrent response in Cs-doped CIS. Li- and Na-doped films had larger conductivity than the undoped film while the K- and Cs-doped samples displayed shorter currents and the current images indicated strong charge accumulation in the K- and Cs-doped films, forming surface capacitors. Corrected current-sensing AFM IV curves were adjusted with the Shockley equation.

The local electrical response in alkaline-doped CuInSe2 films prepared by single-step electrodeposition onto Cu substrates was studied by current-sensing atomic force microscopy. The CuInSe2 (CIS) films were prepared from single baths containing the dopant ions (Li, Na, K or Cs) and were studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and photocurrent response. Increased crystallinity and surface texturing as the ion size increased were observed, as well as an enhanced photocurrent response in Cs-doped CIS. Li- and Na-doped films had larger conductivity than the undoped film while the K- and Cs-doped samples displayed shorter currents and the current images indicated strong charge accumulation in the K- and Cs-doped films, forming surface capacitors. Corrected current-sensing AFM IV curves were adjusted with the Shockley equation.

CdS films were grown on glass substrates by the close spaced vapor transport technique (CSVT). We deposited two series of samples: a) with a substrate temperature of 150 °C (group A) and b) with a variation of substrate temperature between 200 °C and 550 °C, at intervals of 50 °C (group B). The samples of group A were annealed in N, atmosphere, from 200 °C to 400 °C, at intervals of 50 °C. All samples were measured by X-ray diffraction and optical transmission. X-ray diffraction patterns show that the films had a mixture, of cubic and hexagonal structure remained unchanged after the thermal annealing, the main phase present was cubic. The energy band gap shows a thermal stability. The substrate temperature has no effect over the crystal structure and band gap energy. Transmittance and X-ray measurements show a thermal stability of the crystal structure and band gap energy.

Polycrystalline CdSe thin films were grown on glass substrates by chemical bath deposition at 50 oC. The samples were annealed in air atmosphere at different temperatures and characterized by X-ray diffraction and Raman spectroscopy. It was found that the as-grown films have cubic structure. These samples maintain their cubic structure for annealing temperatures between 60 oC and 300 oC. For annealing temperatures higher than 300 oC we obtain a mixture of cubic and hexagonal phases. The analysis made by X-ray diffraction and Raman dispersion show that the samples annealed at temperatures under the phase-transition temperature increase their crystalline quality. In order to determinate the temperature for the complete transition of the cubic phase, we used the precipitated material obtained during the grown of the CdSe films. This material was annealed on air atmosphere between 300 °C and 500 °C with 50 ° intervals. The samples were measured by X-ray diffraction. The samples maintained the cubic structure if the annealing temperature is under 300 °C. For temperatures between 300 °C and 450 °C we found a mixture of cubic and hexagonal phase. For an annealing temperature of 500°C we obtain only the hexagonal phase. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

"El sistema CdS/CdTe posee un gran potencial en la producción de sistemas fotovoltaicos de alta eficiencia, dado que aún se está muy lejos de alcanzar la eficiencia de 30%, predicha teóricamente. Una de las limitaciones para aumentar la eficiencia de esta heteroestructura es la diferencia en estructura cristalográfica del CdTe y CdS, cúbica y hexagonal, respectivamente. Adicionalmente, la presencia de una región con composición gradual en la interfaz CdS/CdTe limita la uniformidad del campo eléctrico interfacial necesario para tener una separación de carga eficiente. Para tener un mejor conocimiento de la aleación CdSTe y eventualmente aportar resultados para incrementar la eficiencia actual hemos crecido películas delgadas de CdSxTe1¡x sobre substratos de vidrio utilizando la técnica de transporte de vapor en espacio reducido combinada con evaporación libre (CSVT-FE, por sus siglas en inglés) usando la coevaporación de CdTe y CdS. La incorporación del S fue controlada por medio de la temperatura de la fuente de CdS. Las muestras fueron caracterizadas utilizando difracción de rayos X, espectroscopías de análisis de la dispersión de energía de los rayos X y de transmisión óptica. Se encontró que las muestras tienen una estructura cúbica, para 0 < x < 1, con el parámetro de red siguiendo la aproximación de cristal virtual. El ancho de banda prohibida tiene un comportamiento cuadrático con el contenido de azufre, similar al reportado en la literatura. El comportamiento del ancho de la banda prohibida no fue afectado por la estructura cúbica de las películas CdSxTe1-x."