Zinc oxide (ZnO) is a wide bandgap semiconductor of great scientific and technological interest due to its high exciton binding energy and outstanding structural and optical properties, making it an ideal material for applications in optoelectronics, sensors, and photocatalysis. This study presents the rapid synthesis of highly crystalline ZnO nanostructures using two alternative routes: (1) direct thermal decomposition of zinc acetate and (2) a physical-green route assisted by Mangifera indica extract. Both routes were subjected to identical calcination thermal conditions (400 °C for 2 h), allowing for an objective comparison of their effects on structural, vibrational, morphological, and optical characteristics. X-ray diffraction analyses confirmed the formation of a pure hexagonal wurtzite phase in both samples, highlighting a higher crystallinity index (91.6%) and a larger crystallite size (35 nm) in the sample synthesized using the physical-green route. Raman and FTIR spectra supported these findings, revealing greater structural order. Electron microscopy showed significant morphological differences, and UV-Vis analysis showed a red shift in the absorption peak, associated with a decrease in the optical bandgap (from 3.34 eV to 2.97 eV). These results demonstrate that the physical-green route promotes significant improvements in the structural and functional properties of ZnO, without requiring changes in processing temperature or the use of additional chemicals.

Obtaining wide energy-gap semiconductor ultra-thin films is an important aspect for their application in sulfide-based solar cells. By reducing the optical losses associated with light reflection and exhibiting absorption edge shifts towards short wavelengths, these layers can optimize the amount of photons interacting with the active photovoltaic material, which increases the conversion efficiency of the solar cell. Ultra-thin CdS films were prepared by a low-cost chemical synthesis and the impact of silver doping on the optical, structural, and morphological properties was evaluated. SEM micrographs revealed that the layers are ultra-thin, homogeneous and uniform, with a reduction in particle size with increasing doping concentration. X-ray diffraction data confirmed the crystallization of CdS in the hexagonal phase for all prepared samples. A low concentration contributed to the formation of Ag₂S in the monoclinic phase according to the diffractograms. The optical properties of the thin films revealed an absorption edge shift that increased the CdS band gap from 2.267 ± 0.007 to 2.353 ± 0.005 eV with increasing doping concentration, improving the spectral transmittance response. These results make these layers particularly useful for implementation in next-generation flexible photovoltaic devices.

In this investigation, thin films of indium-doped CdS and CdS were synthesized using the chemical bath deposition technique. These thin films were characterized by optical transmission, optical reflection, diffraction index and optical band gap. The optical spectra reveal that the optical transmission response increases with the concentrations of indium and the refractive index decreases. The CdS:In samples with 1cM, 2cM and 3cM the optical band gap is 2.50 eV, 2.74 eV, and 2.90 eV respectively.

We report an optical configuration to measure the concentration of ethanol (EtOH) using a light-guiding mechanism based on optical fibers in a Mach–Zehnder-type interferometric configuration. The proposed configuration takes advantage of the high sensitivity of fiber optic interferometers, allowing variations in EtOH concentration to be detected from shifts in the interference patterns. The interferometric configuration was implemented using a single-mode optical fiber curved into a balloon shape. During the experiment, some spectral stability and hysteresis tests were performed on the device, obtaining good results. During the characterization stage for measuring EtOH concentration in the 40–71% v/v range, performance parameters were evaluated, achieving EtOH concentration measurements in the 1500–1600 nm wavelength range. The sensitivity of the devices was evaluated in terms of the geometric parameters of the interferometric curved optical fibers, obtaining a maximum sensitivity of 0.1174 nm/% v/v. In this case, the transmitted optical signal analyzed at the end of the optical fiber allowed the identification of spectral shifts toward longer wavelengths with increasing EtOH concentration. In the study, the behavior of the spectral parameters of the interferometric curved optical fibers was analyzed as a function of the geometric parameters, highlighting their low cost, easy tuning control of minimum intensity peaks and good sensitivity.

This paper reports the design and manufacture of an easy-to-use and accessible teaching system by using 3D printing as a tool for the teaching of the capacitor charging and discharging phenomenon. The didactic system developed, is structured in modules-built piece by piece with 3D printing technology. They are made in a relatively low-cost polymer that could facilitate both teachers and students to improve the teaching-learning processes. This didactic system is reliable, easy to use and low cost. As a way to improve the functionality, the built system is complemented by the use of a free access software and a simple generator of signals that allows to simulate a virtual oscilloscope. This is an additional strategy that would allow the didactic system to enrich the study of the phenomena and eliminate the use of high cost devices that generally limit the experimentation developed traditionally in the teaching of physics. The practical application and implementation of 3D printing technology can be incorporated into a wide variety university subjects in the development of experiments in circuit theory, electricity and magnetism, among others, for its advantages in facilitating the comprehension and assimilation of difficult theoretical concepts and the learning of the physical tangibility of the phenomena under study.

Post-synthesis heat treatment provides a route for tuning the structural and optical response of TiO₂ without necessarily altering its particle architecture. In this study, TiO₂ nanostructures prepared by the sol–gel method were evaluated before and after a stepwise heat treatment from 250 to 400 °C using XRD/Rietveld, Raman spectroscopy, FE-SEM/EDS, statistical morphometry, and UV–Vis diffuse reflectance spectroscopy, with XPS performed on TiO₂-400. TiO₂-250 consisted of 96.76 ± 1.22 wt.% anatase and 3.24 ± 0.47 wt.% brookite, whereas anatase was the only crystalline phase detected in TiO₂-400 within the XRD detection limit. Concurrently, the coherent crystalline domain size increased from 44.3 ± 2.6 to 53.6 ± 1.9 nm, without a statistically significant increase in the equivalent circular diameter of the particles. The apparent optical band gap increased from 3.14 ± 0.03 to 3.25 ± 0.03 eV, while the Urbach energy decreased by approximately 48%, from 189.4 ± 1.1 to 98.0 ± 0.4 meV. These results show that moderate heat treatment is accompanied by polymorphic homogenization and predominantly intraparticle crystalline/electronic reorganization, together with narrowing of the band-tail distribution without appreciable external particle growth. Overall, the study establishes a multiscale correlation between phase evolution, coherent-domain growth, morphological stability, and optical-edge narrowing in sol–gel TiO₂ nanostructures.