Long Electrical Stability on Dual Acceptor p-Type ZnO:Ag,N Thin Films.

p-type Ag-N dual acceptor doped ZnO thin films with long electrical stability were deposited by DC magnetron reactive co-sputtering technique. After deposition, the films were annealed at 400 °C for one hour in a nitrogen-controlled atmosphere. The deposited films were amorphous. However, after annealing, they crystallize in the typical hexagonal wurtzite structure of ZnO. The Ag-N dual acceptors were incorporated substitutionally in the structure of zinc oxide, and achieving that; the three samples presented the p-type conductivity in the ZnO. Initial electrical properties showed a low resistivity of from 1 to 10-3 Ω·cm, Hall mobility of tens cm2/V·s, and a hole concentration from 1017 to 1019 cm-3. The electrical stability analysis reveals that the p-type conductivity of the ZnO:Ag,N films is very stable and does not revert to n-type, even after 36 months of aging. These results reveal the feasibility of using these films for applications in short-wavelength or transparent optoelectronic devices.

Growth of Nanocolumnar TiO2 Bilayer by Direct Current Reactive Magnetron Sputtering in Glancing-Angle Deposition Configuration for High-Quality Electron Transport Layer.

The electron transport layer (ETL) plays a crucial role in solar cell technology, particularly in perovskite solar cells (PSCs), where nanostructured TiO2 films have been investigated as superior ETLs compared to compact TiO2. In this study, we explored the nanocolumnar growth of TiO2 in the anatase phase for bilayer thin films by DC reactive magnetron sputtering (MS) technique and glancing-angle deposition (GLAD). For the growth of the compact TiO2 layer, it was found that the crystalline quality of the films is strongly dependent on the sputtering power, and the samples deposited at 120 and 140 W are those with the best crystalline quality. However, for the nanocolumnar layer, the reactive atmosphere composition determined the best crystalline properties. By optimizing the growth parameters, the formation of TiO2 nanocolumns with a cross-sectional diameter ranging from 50 to 75 nm was achieved. The average thickness of the films exceeded 12.71 ± 0.5 µm. All nanostructured films were grown at a constant GLAD angle of 70°, and after deposition, the measured inclination angle of the nanocolumns is very close to this, having values between 68 and 80°. Furthermore, a correlation was observed between the quality of the initial layer and the enhanced growth of the TiO2 nanocolumns. All bilayer films are highly transparent, allowing light to pass through up to 90%, and present a band gap with values between 3.7 and 3.8 eV. This article offers the experimental parameters for the fabrication of a nanocolumnar TiO2 using the magnetron sputtering technique and the glancing-angle deposition configuration.

Biosynthesis of silver nanoparticles by Fusarium scirpi and its potential as antimicrobial agent against uropathogenic Escherichia coli biofilms.

The ability of Uropathogenic Escherichia coli (UPEC) to form biofilms, can be considered an important factor that contributes to the prevalence of Urinary Tract Infections (UTIs) due to the inaccessibility of the antibiotics into the highly complex structure of the biofilm. Moreover, with the appearance of antibiotic multiresistant UPEC strains, the alternatives of treatment of UTIs are less. Silver nanoparticles (AgNPs) can be useful in the treatment of the UPEC infections due to its physicochemical properties that confer them antibacterial activity against both planktonic and biofilm structured cells. A diversity of biological methods for synthesis of AgNPs with antimicrobial activity has been widely investigated during the last decades, between these methods; the fungal-biosynthesis of AgNPs highlights as an ecofriendly, scalable and low cost method. In this study, biogenic AgNPs were synthesized with extracellular metabolites secreted by the soil fungal strain Fusarium scirpi (Ag0.5-5) by an ecofriendly, simple and efficient method. The antimicrobial activity of the biosynthesized AgNPs against UPEC was evaluated. The Minimal Inhibitory Concentration (MIC) of biogenic AgNPs over planktonic UPEC cells was 25 mg/mL, whereas a sub-MIC concentration (7.5 mg/L) was sufficient to inhibit the UPEC-biofilm formation about a 97%, or produce the disruption of an 80% of mature UPEC-biofilms demonstrating the potential of fungal-derived AgNPs to prevent UPEC infections.

Characterization of six types of Mexican Onyx.

Optical, chemical, and radiation shielding characteristics of 6 types of Mexican onyx from the semi-desert of Zacatecas have been determined. Onyx samples are Yellow, Blue, Brown, Orange, Red and Green. Characterization was carried out using Energy dispersed X-Ray fluorescence, Visible Ultraviolet Spectrometry and Infrared Spectroscopy. With these techniques it was possible to study the chemical, physical and optical characteristics of the Mexican Onyx; from where the elemental composition was obtained, the absorption peaks, the vibrational modes and the optical band gap. As well as the interactions of these materials with radiation was studied. From this last study we obtained the Mass interaction coefficient for the coherent and incoherent dispersion, the photoelectric effect, the Compton scattering and the pair production, in the atomic nucleus and the electron field. For all types of onyx the total mass attenuation coefficients are alike showing a resonance due to K-shell of Ca. Mexican onyx has a good shielding features to photons of energy less than 100 keV because the most probable event is the photoelectric effect.

Thermoluminescent properties of ZnS:Mn nanocrystalline powders.

Thermoluminescent ZnS nanocrystals doped with Mn(2+) ions were synthesized by chemical co-precipitation method. From X-ray diffraction studies it was observed that the synthesized nanoparticles have cubic zinc blende structure with average sizes of about 40-50nm. Morphology was analyzed by TEM. Photoluminescence studies showed two transitions, one of them close to 396nm and other close to 598nm, which is enhanced with increasing dopant concentration, this behavior was also observed in the cathodoluminescence spectrum. The thermoluminescence gamma dose-response has linear behavior over dose range 5-100mGy, the glow curve structure shows two glow peaks at 436K and at 518K that were taken into account to calculate the kinetic parameters using the Computerized Glow Curve Deconvolution procedure.