We report on our systematic study of light trapping effects using Ag/ZnO BRs for nc-Si:H solar cells. The texture of Ag and ZnO was optimized to achieve enhancement in photocurrent. The light trapping effect on photocurrent enhancement in solar cells was carefully investigated. Comparing to single-junction solar cells deposited on flat stainless steel substrates, the gain in Jsc by using Ag/ZnO BRs is 57% for nc-Si:H solar cells. This gain in Jsc is much higher than what has been achieved by advanced light trapping approaches using photonic structures or plasmonic light trapping reported in the literature. We achieved a Jsc of 29-30 mA/cm2 in a nc-Si:H single-junction solar cell with an intrinsic layer thickness of ∼2.5 μm. We compared the quantum efficiency of single-junction cells to the classical limit of fully randomized scattering and found that there is a 6-7 mA/cm2 difference between the measured Jsc and the classical limit, in which 3-4 mA/cm2 is in the long wavelength region. However, by taking into consideration the losses from reflection of the top contact, absorption in the doped layers, and imperfect reflection in the BRs, the difference disappears. This implies we have reached the practical limit if the scattering from randomly textured substrates is the only mechanism of light trapping. Therefore, we believe future research for improving photocurrent should be directed toward reducing (i) reflection loss by the top contact, the absorption in ZnO and at the Ag/ZnO interface, and (ii) p layer absorption.

Zinc oxide (ZnO) nanowires (NW) are grown on both silicon and sapphire substrates using conventional chemical vapor deposition (CVD) system. As-grown nanostructures are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) as well as energy dispersive spectroscopy (EDS) and the results confirm high-quality c-axis growth of single-crystalline zinc oxide nanowires. Nanowire are dispersed in solvent and then placed between micro-patterned gold electrodes fabricated on silicon wafers using low cost and scalable dielectrophoresis (DEP) process for fabrication of oxygen and humidity sensors. These sensors are characterized in a vacuum chamber connected to a semiconductor analyzer. Current-voltage characteristics of each device are systematically investigated under different hydrostatic pressure of various gaseous environments such as nitrogen, argon, dry and humid air. It is observed that the electrical conductivity of the nanowires is significantly dependent on the number of oxygen and water molecules adsorbed to the surface of the metal oxide nanowire. These results are critical for development of low cost metal oxide sensors for high performance ubiquitous environmental sensors of oxygen and humidity.

This article discusses recent scientific research performed by the author in understanding the composition of archaeological purple pigments and dyes from molluskan sources, which were primarily used for the dyeing of royal and priestly textiles, as also cited in the Bible. Towards this end, the high-performance liquid chromatography (HPLC) method has been applied to the qualitative and quantitative multi-component fingerprinting of purple pigments extracted from various Muricidae mollusks inhabiting the Mediterranean waters. The results show that the colorants in these purple pigments belong to three chemical groups: the indigoids (of major importance), the indirubinoids, and the isatinoids. Application of this analytical method to purple pigments and dyes on archaeological artifacts from the ancient Near and Middle East has lead to a number of breakthroughs and discoveries made by this laboratory. These include the following: decipherment of the optimal method by which the ancients practiced purple-dyeing by completely natural means; first HPLC analysis of a raw unprocessed purple archaeological snail pigment and the resulting identification of a dibrominated indirubin in this pigment; discovery of the purple pigment as the sole paint pigment on a 2,500 royal marble jar from the Persian King Darius I; and the discovery that a 2,000 year old miniscule fabric found atop the Judean Desert palatial fortress of Masada belonged to the royal purple mantle of King Herod I and is the first Biblical Argaman dye found in ancient Israel.

The main challenge associated with the synthesis of pure bismuth ferrite (BFO) is the extremely high stability of parasitic or secondary phase Bi-oxides, which contaminates the single ferrite phase and affects the corresponding functional properties. Therefore, any attempt to determine the optimum synthesis conditions conducive to the inhibition of the formation of those impurity phases becomes indispensable. Accordingly, the present work addresses the systematic evaluation of the type of solvent and synthesis parameters to exclusively produce the BFO structure. Nanocrystalline BFO powders were synthesized after thermal treatment of the solid intermediates formed in ethylene glycol and acetic acid media. The experimental work also considered the effect of the excess of Bi species with respect to the BiFeO3stoichiometry and the annealing of the intermediates at different temperatures. The structure formation was confirmed by XRD analysis and magnetic properties were studied by VSM. X-ray diffraction analyses confirmed that powders exhibiting single phase BFO structure were produced after annealing the intermediate which was formed in acetic acid for one hour at 700°C. The average crystallite size and lattice parameter were calculated to be approximately 40 nm and 5.36 Å, respectively. It was also found that the synthesis under 7% of Bi-stoichiometric excess inhibited the formation of the parasitic phases after annealing the intermediate produced in ethylene glycol medium. The saturation magnetization of the powders annealed at 700°C were 0.15 emu/g and 0.17 emu/g when the BFO intermediates were formed in ethylene glycol and acetic acid media, respectively. The corresponding coercivity values were 6 Oe and 21 Oe.

The Santa Mónica Church is one of the most representative buildings in Guadalajara, Mexico as it is the finest Solomonic Baroque temple in the city. The church was built in the XVIII century with different types of volcanic tuffs, which have been studied from the macroscopic level to the structural level with the aim to determine the deterioration degree of the church’s tuffs.

Textural, morphological and structural properties of Tuff were characterized using X-ray powder diffraction (XRD), infrared spectroscopy (FT-IR ATR) and 29Si and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR), nitrogen adsorption-desorption techniques, scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), compressive strength tests were also performed.

Characterization data has provided a comprehensive view of the alterations on the volcanic tuff of Santa Mónica Church. Then the study focused on proposing the best strategy for the understanding and conservation of Churches and other buildings in Guadalajara which have been built with the same stone. Currently, siliceous materials doped with aluminum are being tested as consolidate.

Following the generic strategy of creating core-shell structured nanoparticles reported by our group previously [1] and exploring its applications, an aerosol route combined with iron carbonyl decomposition was developed to encapsulate strong oxidizer within mild oxidizer particles. This modified method enables the application of hygroscopic nano-energetic materials by stabilizing them within a water-insoluble shell. Fe2O3/I2O5 composite oxidizers have been created. Some of the results obtained from combustion tests show that the composite system significantly outperforms the single metal oxide (Fe2O3) system in both pressurization rate and peak pressure. The time-resolved mass spectrometry shows that a significant amount of O2 and I2 are released from the composite oxidizers. These preliminary results suggest a supplement to the previous strategy of obtaining the core-shell structured composite oxidizers and the method still needs to be further optimized.

We measure the mechanical response of optical multilayer dielectric (MLD) diffraction gratings, geometries which are constrained in only one transverse direction but free in the other, using nanoindentation. The results are explained using a stress-strain model, which reveals a uniaxial yield stress of 4.1- 4.6 GPa and predicts a similar dependence of yield stress on loads for both fully-elastic and fully-plastic solutions. Following R. Hill’s model of an expanding cavity under internal pressure, we show that the indentation response of the high-aspect ratio “pillar” geometry can be expressed in terms of uniaxial yield stress rather than material hardness.

Chemical-technology investigation was carried out for 95 belt sets from the burials of 8th−11thcenturies. In its course three groups of burials were separated on the basis of archaeology-statistical features; the Group 3 was identified as status one. All the groups contain belt sets made from the cooper-based alloys which include silver (6.98−92.87%) and amalgam. The major scheme of the belt sets (Groups 1, 2, 3) production is casting in moulds with print of used plaques; there are belt sets in Groups 1 and 2 which were made in different way (lost wax casting, casting in moulds with print of special matrix, forging). Chemical and technology parameters of the belt sets from the elite burials of the Group 3 are similar to the parameters of the belt sets discovered in the common burials of the Groups 1 and 2. There are a number of burials in the Group 1 the belt sets of which according to their chemical-technology characteristics could be attributing to the “award”.

The assessment of the main changes expected for spent nuclear fuel from its discharge to its deposition in a deep geological repository is of the outmost relevance to establish the initial conditions of the disposal. In this work, a literature review and a critical discussion of the main processes that will affect the structure and the inventory of the spent nuclear fuel during its interim dry storage is presented. Once the irradiation period is finished, the following changes are observed: i) the fuel pellet is fragmented due to the temperature gradient established during the irradiation stage. On average between 10-15 fragments are observed per pellet. ii) the initial gap existing between the pellet and the cladding decreases or disappears depending on the burnup. iii) a radial zonation is observed in the microstructure of the pellet. For burnup over 40MWd/KgU, the rim develops a porosity increase due to the high local burnup and the low temperature in the periphery. The rim also presents small bubbles of fission gases. This high burnup structure implies a degradation of the thermic conductivity in the pellet, that leads to a temperature increase in the center of the pellet with a subsequent migration of the fission gases and other impurities to the grain boundaries. The implications that all these changes may have on the spent fuel behaviour is presented and discussed.

Thermotropic polymers are thermally treated in air at temperatures T a , where ΔT =T a - T s→n =40°C, and T s→n is the solid-to-nematic transition. Samples are extruded thin films of a series of thermotropic random copolyesters termed B-N, COTBP and RD1000. The thermal treatment produces a second endotherm without changing T s→n for B-N and RD1000. However, for COTBP T s→n is significantly increased. Regardless of the complex thermal behavior exhibited by the thermotropes, the thermal treatment produces a significant increase in Young's modulus, more than 30% for B-N and over 100% for COTBP. The increase in mechanical modulus is correlated with a thermally-induced fiber-like morphology.

In this work, the synthesis of carbon nanotubes/hematite hybrids was investigated. The hybrids were produced by solvothermal method and a systematic study exploring different reaction parameters such as treatment duration, temperature and solvent was performed. Results from different characterization techniques demonstrate that the CNTs were effectively decorated with hematite (α-Fe2O3). The size and concentration of the NPs varies with the reaction parameters and the smallest obtained NPs have ∼100 nm diameter. It was demonstrated that translucent and homogeneous thin films made of the resulting hybrid material can be deposited on indium-tin oxide substrates by electrophoretic deposition or by vaccum filtration.

The electrochemiluminescence (ECL) and surface plasmon resonance (SPR) based immunosensors for measuring a trace level of disease markers are shown. It is well known that thiols form a self-assembled monolayer on a metal surface, and this has been widely used to modify metal surfaces. We employed this characteristic for a highly sensitive immunosensors by obtaining a surface pre-concentration of thiol molecules formed by the enzymatic reaction of labeled antibody.

Focused ion beam (FIB) milling of diamonds has been investigated in various ways to create desired structures on diamonds, but not much research has been reported on the effects of crystal orientation, i.e. {100}, {110} and {111} of diamonds on FIB milling. In our previous work, it was noted that focused ion beam milling may develop preferred etched directions related to the crystal orientation of crystalline diamonds. In order to further investigate the phenomenon, a focused beam of 30 kV Ga+ ions was utilized to generate various patterns on different crystallographic planes of single crystalline diamonds. The morphology of milled patterns has been monitored with various ion currents to find the relationship between crystal orientations of diamonds and their impacts on FIB milled patterns. The work showed significant differences in deformation among different crystal orientations of the single crystal diamond, and the largest area of milling in {111} crystallographic planes.

Exchanging the original organic ligands of colloidal CdSe quantum dots (QDs) with metal chalcogenide SnS4 ligands resulted in absorption peak redshifts and complete photoluminescence quenching in QD solids. The ITO/QDs/Al structure with SnS4-capped QDs showed much higher electrical conductivity and reduced space-charge limited current. These results are indicative of carrier delocalization as well as enhanced inter-QD electronic coupling caused by the inorganic ligands. The SnS4-capped QDs were able to retain strong excitonic absorption. The photocurrent spectral response of the all-inorganic QD film resembled its absorption spectra, and was three orders of magnitude stronger than that of QDs with organic ligands. It was found that mild annealing at ∼ 200 o C transformed the SnS4-capped QD film into to a more conductive assembly, degrading its absorption and photocurrent generation. These findings suggest that colloidal QDs with metal chalcogenide ligands are better suited for solar energy conversion and photodetection than use in light-emitting devices as luminophores.

Coinage metals nanoparticles have been widely used in last decade for enhancing the Raman signal of a variety of compounds. Several preparation methods have been proposed, including chemical reduction of gold or silver salts with sodium citrate, hydroxylamine or sodium borohydride, microwave-assisted reduction with glucose, Tollens mirror, electrodeposition, vacuum evaporation and pulsed-laser deposition.

In this work, gold and silver nanoparticles were prepared by chemical reduction with sodium citrate and hydroxilmanine, characterized by UV-Vis spectroscopy and High Resolution Transmission Electronic Microscopy and tested as SERS substrate. Carminic acid, cochineal, axiote, muitle and zacatlaxcalli SERS spectra were recorded at different pH. Natural dyes samples were prepared by extraction from its natural sources, following traditional recipes. Although differs for each dye, best results were achieved by performing SERS experiments at pH neutral to basic.

Organic magnetoresistance (OMAR) of single-crystalline (SC) pentacene (C22H14) and perfluoropentacene (C22F14) was studied using field-effect transistor structures. The gate voltage effect showed that the OMAR originates from photo-induced current and requires both electrons and holes in the transport channel. The temperature dependence showed the maximum magnetoresistance (MR) ratio up to -6% under light irradiation at approximately 200 K and magnetic field of 80 mT. The charge carrier mobility and the exciton diffusion length were not important factors to determine the MR ratios. The interaction between triplet excitons and traps was thought to govern the OMAR behaviors.

We report 3D finite element simulations analyzing scaling effects on the performance of single Silicon Germanium thermoelectric generator with 170 μm tall metal contacts. Temperature dependent material parameters are included to accurately model device performance. Power density was extracted for a range of widths, heights, and operating temperature. Depending upon cross sectional area of the SiGe leg and operating temperature, height can be optimized for maximum power density.

Plasma surface activation and antibacterial properties of nanocomposites of polypropylene/silver nanoparticles (PP/nAg) and nylon-6/silver nanoparticles (Ny6/nAg) were investigated. The nanocomposites were prepared by melt blending assisted by ultrasound, while surface activation was achieved by means of argon plasma. To evaluate the antimicrobial properties of the nanocomposites, pathogen microorganisms such as Pseudomonas aeruginosa and Aspergillus niger were tested. Scanning Electron Microscopy (SEM) analyses showed a uniform dispersion of nanoparticles within the polymer matrix, though the presence of some agglomerates was also appreciated. On the other hand, surface topography by Atomic Force Microscopy (AFM) suggested that ions from the argon plasma generated ion collisions with the surface of the nanocomposites removing or etching polymer from surface and improving silver nanoparticles exposure, increasing their antimicrobial properties as corroborated by antimicrobial analyses. Nanocomposites exposed to argon plasma presented higher antimicrobial properties than the ones not exposed. These results indicated that plasma treatment increased the contact area of the nanoparticles with the microorganisms and enhanced the antimicrobial properties of nanocomposites. The results also showed that PP/nAg nanocomposites presented higher bacterial inhibition than Ny6/nAg nanocomposites, indicating that the chemical structure of the polymer also plays a big role in the final performance of the composite.