Revista de Ciencias Tecnológicas

Optical and Methanol Sensing Properties of Al-doped ZnO Thin Film

Sumitra Pandey, Samundra Marasini, Rishi Ram Ghimire — Wed, 20 Nov 2024 00:00:00 +0000

The study investigates the optical and electrical properties of undoped and aluminum (Al)-doped zinc oxide (ZnO) films, focusing on their performance as gas sensors and their potential applications. Optical analysis, conducted using UV-visible spectrophotometry, reveals that 1% Al-doped ZnO films exhibit the highest transmittance of 91%, indicating superior optical clarity and suitability for applications like solar cell electrodes. In contrast, 3% Al-doped ZnO films show significantly lower transmittance due to increased light scattering and photon absorption. The bandgap of ZnO films decreases with higher Al doping concentrations, from 3.3 eV for undoped ZnO to 3.15 eV for 3% Al-doped ZnO, suggesting enhanced electrical conductivity due to reduced bandgap. The extinction coefficient data demonstrate that 2% Al-doped ZnO has the highest extinction coefficient, reflecting improved light absorption and scattering properties. Electrical characterization through I-V curves indicates that 1% Al-doped ZnO films have higher current (121 µA) compared to undoped (431 µA) and higher doping concentrations, attributed to enhanced carrier concentration and mobility. Sensitivity tests show that 2.5% Al-doped ZnO films exhibit the highest sensitivity to methanol vapor, with a significant reduction in resistance compared to 0.5% Al-doped ZnO films. Resistance measurements with varying methanol volumes reveal a rapid decrease upon gas introduction, stabilizing and then increasing as the gas is removed. Sensitivity analysis indicates that 100 µL methanol provides the highest sensitivity (97%) at 60°C, while 2% Al-doped ZnO films show consistent sensitivity at 60 °C and 100 °C, but not at 80 °C.

Electrochemical generation of hydrogen using industrial ammonia water and recycled graphite electrodes

Wed, 04 Dec 2024 00:00:00 +0000

The pursuit of fuels that do not emit greenhouse gases has made the use of hydrogen in the steel industry increasingly necessary. This study represents an ecological commitment, wherein both researchers and the company aim to generate hydrogen for use in the steel production process. An acrylic cell, ammoniacal solution, and power source were used in the experimental setup, which consists of three parts: first, the evaluation of hydrogen generation by varying the applied voltage and electrolysis duration; second, the replacement of ammoniacal water with a synthetic ammonia solution to understand system behaviour and minimize the effects of solution components unrelated to ammonia; and third, the substitution of graphite electrodes with steel electrodes to assess their impact on the electrolytic process. Hydrogen quantification was carried out indirectly using a Venturi tube, which captured the generated gases, and through a copper sulphate solution (producing precipitates) to stoichiometrically determine the mass of produced hydrogen. The results of evaluating time, current density, and solution concentration defined an optimal electrolysis time of 30 minutes, a current density of 100 A/m², and indicated that the initial ammonia concentration in the solutions influences the results. The best results corresponded to 1.130 g of H₂ in a solution with an initial concentration of 2.6 g/l NH₃. In conclusion, this study determined optimal processing conditions, established the effect of initial ammonia concentration on the electrochemical generation of hydrogen, observed a decrease in ammonia concentration across all solutions, and successfully calculated the generated gas mass through indirect hydrogen quantification.

Structural and functional prediction of DNA glycosylases as well as their phylogenetic relationship by bioinformatic methods

Estrella Alexandra, Marco Antonio Popoca Cuaya — Mon, 28 Oct 2024 00:00:00 +0000

Nitrogenous bases are a component of DNA nucleotides and can be altered by both external and internal factors. The base excision repair (BER) mechanism is responsible for removing damaged bases through the action of various enzymes. In this study, we performed an in-silico analysis of the gene and protein sequences of glycosylases responsible for eliminating altered bases: MPG, OGG1, NEIL1, MUTYH, and NTHL1, which participate in the BER mechanism of Homo sapiens. We used various bioinformatics tools to characterize the guanine and cytosine (G≡C) content of the genes, the secondary and tertiary structures of the glycosylases, protein motifs, and the phylogenetic relationships between the glycosylases. Gene and amino acid sequences were downloaded from GenBank, and the online software tools GENSCAN, Gor4, Phyre2, InterPro, and MEGA were used. The G≡C content percentages obtained were 63.80%, 63.50%, 61.33%, 60.48%, and 59.20% for MPG, NTHL1, NEIL1, MUTYH, and OGG1, respectively. Secondary structure analysis of the proteins showed that NTHL1 has the highest percentage (43.42%) of alpha helix, OGG1 has the highest percentage (16.23%) of extended chain structure, and NEIL1 has the highest percentage of random coil (57.69%). Additionally, we performed the prediction of tertiary structure and domains in proteins, where the HhH domain was observed in OGG1, MUTYH, and NTHL1. The phylogenetic tree revealed the evolutionary relationships among the studied genes, with the OGG1 gene being the common ancestor. These findings are important for understanding the molecular structure of glycosylases and provide valuable information that can be utilized in both experimental and biotechnological studies, as well as in understanding the evolutionary function of DNA repair and in the design of therapeutic strategies involving glycosylases.