The chemical properties of engine oil are part of the main parameters to evaluate its condition since oxidation starts chemical reactions that alter its operating conditions. In this work, the chemical properties of engine oil were analyzed based on the standard ASTM E2412 by FT-IR spectroscopy to evaluate the lubricating oil condition. Furthermore, a sensor based on the position of the localized surface plasmon resonance (LSPR) band of silver nanoparticles (AgNP), synthesized by the laser-assisted photoreduction method, was developed. This plasmonic sensor can detect changes in the permittivity of the oil, caused by the modification of the chemical properties of the lubricant. The response of the sensor during the study of degraded oil resulted in a notorious displacement to higher wavelengths of the LSPR band as mileage increases. The results of FT-IR analysis were correlated with the measurements of the proposed sensor presenting linear trends with good correlation (R² > 0.9491).

Cadmium-derived materials are highly demanded for optoelectronics applications, and the scientific community has widely worked in different ways to develop them. In this research, the optimization of CdCO₃ films using a chemical bath deposition (CBD) method at different deposition times (10, 11, and 12 h) is reported. The intention to optimize CdCO₃ films is in order to propose it as a precursor to produce different types of cadmium-derived semiconductors such as CdSe, CdTe, and CdO. The obtained films were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, optical absorption by diffuse reflectance, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The results provide evidence that CdCO₃ films were effectively synthesized, featuring a rhombohedral crystalline structure with a preferential plane (104), and crystallite sizes were 65, 69, and 87 nm for the deposited samples at 10, 11, and 12 h, respectively. Surface morphology analysis revealed microstructures around 3–5 $\mathsf{\mu }\mathrm{m}$, with a deltoid shape, agglomerated and distributed randomly for all samples. The bandgap obtained was 3.78 eV for all samples.

Complete optoelectronic devices present major difficulties to be built by aqueous chemical deposition. In this work, a ITO/CdS/PbSe heterostructure was developed, depositing CdS over an ITO-coated substrate via a chemical bath deposition (CBD) technique. The next step involved the growth of a plumbonacrite film over CdS via CBD, where the film acted as a precursor film to be converted to PbSe via ion exchange. The characterization of each material involved in the heterostructure were as follows: the CdS thin films presented a hexagonal crystalline structure and bandgap of 2.42 eV; PbSe had a cubic structure and a bandgap of 0.34 eV. I vs. V measurements allowed the observation of the electrical behavior, which showed a change from an ohmic to diode response by applying a thermal annealing at 150 °C for 5 min. The forward bias of the diode response was in the order of 0.8 V, and the current-voltage characteristics were analyzed by using the modified Shockley model, obtaining an ideality factor of 2.47, being similar to a Schottky diode. Therefore, the reported process to synthesize an ITO/CdS/PbSe heterostructure by aqueous chemical methods was successful and could be used to develop optoelectronic devices.

This study reports a facile, phyto-mediated synthesis of ZnO nanoparticles utilizing the Ocimum basilicum var. purpurascens extract. The high phenolic (1807.28 ± 57.38 µmol GAE/g) and flavonoid (33.17 ± 3.50 µmol QE/g) contents of the extract successfully induced the formation of the crystalline hexagonal wurtzite phase under mild reaction conditions, circumventing the conventional requirement for the initial high-temperature calcination. The structural, morphological, and optical evolution of the nanoparticles was systematically evaluated from their as-synthesized state to the thermal annealing temperatures of 700 °C to 900 °C. X-ray diffraction analysis confirmed an increase in crystallite size from 21.5 nm to 55.6 nm, while scanning electron microscopy revealed a corresponding growth in average particle size from 143.33 nm to 261.50 nm due to thermal sintering. Furthermore, FTIR and EDS verified the degradation of organic capping agents and a progressive stoichiometric refinement, with the high-temperature samples approaching theoretical elemental purity (18.22% normalized oxygen mass). Optical characterization demonstrated a red-shift in the band gap energy from 3.28 eV to 3.21 eV, alongside a significant increase in visible diffuse reflectance progressing from a baseline of 30–60% to values exceeding 95% upon the removal of the biochemical components. These findings validate the OBPE-mediated protocol as a sustainable, thermodynamically advantageous route for producing structurally and optically tunable ZnO nanomaterials for advanced applications.