In this research work, the photocatalytic capacity shown by the nanoparticles of the CaTiO₃ system was evaluated to degrade two pollutants of emerging concern, namely methyl orange (MO)—considered an organic contaminating substance of the textile industry that is non-biodegradable when dissolved in water—and levofloxacin (LVF), an antibiotic widely used in the treatment of infectious diseases that is released mostly to the environment in its original chemical form. The synthesis process used to obtain these powders was the polymeric precursor method (Pechini), at a temperature of 700 °C for 6 h. The characterization of the obtained oxide nanoparticles of interest revealed the presence of a majority perovskite-type phase with an orthorhombic $\mathrm{P}\mathrm{b}\mathrm{n}\mathrm{m}$ structure and a minority rutile-type $\mathrm{T}\mathrm{i}{\mathrm{O}}_2$ phase, with a $\mathrm{P}42/\mathrm{m}\mathrm{n}\mathrm{m}$ structure and a primary particle size $<100\mathrm{n}\mathrm{m}$. The adsorption–desorption isotherms of the synthesized solids had H3-type hysteresis loops, characteristic of mesoporous solids, with a BET surface area of $10.01{\mathrm{m}}^2/\mathrm{g}$. The Raman and FTIR spectroscopy results made it possible to identify the characteristic vibrations of the synthesized system and the characteristic deformations of the perovskite structure, reiterating the results obtained from the XRD analysis. Furthermore, a bandgap energy of $~3.4\mathrm{e}\mathrm{V}$ and characteristic emissions in the violet (437 nm/2.8 eV) and orange (611 nm/2.03 eV) were determined for excitation lengths of 250 nm and 325 nm, respectively, showing that these systems have a strong emission in the visible light region and allowing their use in photocatalytic activity to be potentialized. The powders obtained were studied for their photocatalytic capacity to degrade methyl orange (MO) and levofloxacin (LVF), dissolved in water. To quantify the coloring concentration, UV–visible spectroscopy was used considering the variation in the intensity of the characteristic of the greatest absorption, which correlated with the change in the concentration of the contaminant in the solution. The results showed that after irradiation with ultraviolet light, the degradation of the contaminants MO and LVF was 79.4% and 98.1% with concentrations of 5 g/L and 10 g/L, respectively.

The influence of the incorporation of nanoparticles of titanium oxide (TiO₂) at a concentration between 1000 and 50,000 ppm on the physicochemical and mechanical properties of a polymer matrix formed from a binary mixture of chitosan (CS) and polyvinyl alcohol (PVA) at a ratio of 80:20 and the possibility of its use as a solid polymeric electrolyte were evaluated. With the mixture of the precursors, a membrane was formed with the solvent evaporation technique (casting). It was found that the incorporation of the nanoparticles affected the moisture absorption of the material; the samples with the highest concentrations displayed predominantly hydrophobic behavior, while the samples with the lowest content displayed absorption values of 90%. Additionally, thermogravimetric analysis (TGA) showed relatively low dehydration in the materials that contained low concentrations of filler; moreover, differential scanning calorimetry (DSC) showed that the nanoparticles did not significantly affect the thermal transitions (Tg and Tm) of the compound. The ionic conductivity of the compound with a relatively low concentration of 1000 ppm TiO₂ nanoparticles was determined by complex impedance spectroscopy. The membranes doped with a 4 M KOH solution demonstrated an increase in conductivity of two orders of magnitude, reaching values of 10⁻⁶ S·cm⁻¹ at room temperature in previously dried samples, compared to that of the undoped samples, while their activation energy was reduced by 50% with respect to that of the undoped samples. The voltage–current test in a proton exchange membrane fuel cell (PEMFC) indicated an energy efficiency of 17% and an open circuit voltage of 1.0 V for the undoped compound, and these results were comparable to those obtained for the commercial membrane product Nafion^® 117 in evaluations performed under conditions of 90% moisture saturation. However, the tests indicated a low current density in the undoped compound.

The impacts on the morphological, electrical and hardness properties of thermoplastic polyurethane (TPU) plates using multi-walled carbon nanotubes (MWCNTs) as reinforcing fillers have been investigated, using MWCNT loadings between 1 and 7 wt%. Plates of the TPU/MWCNT nanocomposites were fabricated by compression molding from extruded pellets. An X-ray diffraction analysis showed that the incorporation of MWCNTs into the TPU polymer matrix increases the ordered range of the soft and hard segments. SEM images revealed that the fabrication route used here helped to obtain TPU/MWCNT nanocomposites with a uniform dispersion of the nanotubes inside the TPU matrix and promoted the creation of a conductive network that favors the electronic conduction of the composite. The potential of the impedance spectroscopy technique has been used to determine that the TPU/MWCNT plates exhibited two conduction mechanisms, percolation and tunneling conduction of electrons, and their conductivity values increase as the MWCNT loading increases. Finally, although the fabrication route induced a hardness reduction with respect to the pure TPU, the addition of MWCNT increased the Shore A hardness behavior of the TPU plates.

Thermoplastic polyurethane (TPU) doped with multi-walled carbon nanotubes (MWCNTs) at 1, 3, 5, and 7 wt% has been studied. The effect of MWCNTs on thermal, viscoelastic, and electric properties in the TPU matrix was characterized by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and by impedance spectroscopy. The results show that the thermal, electrical, and viscoelastic properties, such as the glass transition temperature, shifted towards high temperatures. The melting temperature decreased, and the conductivity and the storage modulus increased by 61.5 % and 58.3 %. The previously observed behavior on the films is due to the increase in the mass percentage of carbon nanotubes (CNTs) in the TPU matrix. Also, it can be said that the CNTs were homogeneously dispersed in the TPU matrix, preventing the movement of the polymer chains, and generating channels or connections that increase the conductivity and improve the thermal properties of the material.

Gold nanostructures (AuNSs) were used to fabricate surface-enhanced Raman spectroscopy (SERS) substrates. These AuNSs were produced using the solid-state dewetting method from thin films. The fragmentation process was studied at 300 °C, with durations of thermal treatment of 1, 3, 6, and 12 h. These SERS substrates were then employed to detect Rhodamine B (RhB) as the model analyte, simulating a contaminant in the water at a concentration of 5 ppm. The morphology of the AuNSs was examined using SEM, which revealed a spheroidal shape that began to coalesce at 12 h. The size of the AuNSs was estimated to range from 22 ± 7 to 24 ± 6 nm, depending on the annealing time. The localized surface plasmon resonance of the AuNSs was determined using absorption spectroscopy, showing a shift as the annealing time increased. The SERS signals of RhB adsorbed on the AuNS substrates were validated by performing a 10 × 10 point map scan over each sample surface (1, 3, 6, and 12 h), and a comparative analysis showed no significant differences in the positions of the bands; however, variations in intensity enhancement ranged from 5 to 123 times at 6 and 1 h, respectively.