In this paper we show the characterization of two kinds of quantum dots: hydrophilic and hydrophobic, with core and core/shell respectively, using spectroscopy techniques such as UV-Vis, fluorescence and Raman. We determined the quantum yield in the quantum dots using the quinine sulphate as standard. This salt is commonly used because of its quantum yield (56%) and stability. For the CdTe excitation, we used a wavelength of 549nm and for the CdSe/ZnS excitation a wavelength of 527nm. The results show that CdSe/ZnS (49%) has better fluorescence, better quantum dots, and confirm the fluorescence result. The quantum dots have shown a good fluorescence performance, so this property will be used to replace dyes, with the advantage that quantum dots are less toxic than some dyes like the rhodamine. In addition, in this work we show different techniques to find the quantum dots emission: fluorescence spectrum, synchronous spectrum and Raman spectrum.

This study deals with the laser stereolithography manufacturing feasibility of copper-nickel nanowire-loaded photosensitive resins. The addition of nanowires resulted in a novel resin suitable for additive manufacturing technologies based on layer-by-layer photopolymerization. The pure and nanowire-loaded resin samples were 3D printed in a similar way. Their morphological, mechanical, thermal, and chemical properties were characterized. X-ray computed tomography revealed that $0.06\mathrm{vol}\%$ of the composite resin was filled with nanowires forming randomly distributed aggregates. The increase of $57\%$ in the storage modulus and $50\%$ in the hardness when loading the resin with nanowire was attributed to the load transfer. Moreover, the decrease in the glass transition temperature from $57.9°\mathrm{C}$ to $52.8°\mathrm{C}$ in the polymeric matrix with nanowires evidenced a decrease in the cross-linking density, leading to a higher mobility of the polymer chains during glass transition. Consequently, this research demonstrates the successful dispersion and use of copper-nickel nanowires as a reinforcement material in a commercial resin for laser stereolithography.

Nowadays, nanomaterials in cement pastes are among the most important topics in the cement industry because they can be used for several applications. For this reason, this work presents a study about the influence of changing the molarity of dispersed multiple wall carbon nanotubes (MWCNTs) and varying the number of storage days on the mechanical properties of the cement paste. To achieve this objective, dispersions of 0.35% MWCNTs, varying the molarity of the surfactant as 10 mM, 20 mM, 40 mM, 60 mM, 80 mM, and 100 mM, were performed. The mixture of materials was developed using the sonication process; furthermore, materials were analyzed using UV-Vis, Z-potential, and Raman spectroscopy techniques. Materials with a molarity of 10 mM exhibited the best results, allowing them to also be stored for four weeks. Regarding the mechanical properties, an increase in the elastic modulus was observed when MWCNTs were included in the cement paste for all storage times. The elastic modulus and the maximum stress increased as the storage time increased.

Nanosecond-pulsed Nd:YAG laser ablation was investigated as a method for removing Al Ti-based hard coatings deposited on WC–Co hardmetal inserts. Systematic variation in laser parameters identified conditions for complete coating removal while preserving substrate integrity. The laser was operated at 532 nm, under a range of fluences (0.1–11.7 J/cm²), pulse delays (20–180 µs), and pulse numbers (1–300). LIBS qualitative monitoring enabled precise ablation progress by identifying Ti, Al, and O layers, and later the detection of Co and W signals. Scanning electron microscopy (SEM/EDS) and optical profilometry confirmed that 5–10 pulses at intermediate delays (60–80 µs, 4.8–7.1 J/cm²) provided complete removal of ~18 µm-thick coatings while maintaining substrate integrity. In contrast, higher energies and excessive pulses caused localized melting and surface irregularities. These results demonstrate that Nd:YAG laser ablation, especially when coupled with LIBS, offers a precise, fast, and environmentally alternative to conventional chemical stripping methods for the refurbishment and recycling of cutting tools.

Existe un incremento de publicaciones por conocer la problemática de la contaminación marina por microplásticos (MPs), donde ya se reconocen algunos de los efectos que pueden tener en el zooplancton. Este aumento de publicaciones requiere que se revisen lasmetodologías para unificar criterios de comparación, por lo que es de gran importancia unificar técnicas para las metodologías de extracción de los microplásticos ingeridos por el zooplancton para determinar la abundancia y las características de los MPs. A partir de una búsqueda enbases de datos, se escogieron cuatro técnicas específicas para la degradación de la materia orgánica representada por el zooplancton. Las técnicasfueron evaluadas en cuatro aspectos: 1) Eficiencia de la degradación de la materia orgánica, 2) Duración y condiciones de temperatura para elprocesamiento, 3) Efecto físico de la digestión sobre los microplásticos, 4) cuantificar los MPs a partir de la tasa de ingestión. Se emplearon cincuenta individuos para cada uno de los grupos más abundantes correspondientes a las familias Paracalanidae, Corycaeidae y Oncaeidae, y al filo Chaetognatha. Los resultados obtenidos mostraron que la mejor técnica fue la de Md Amin et al (2020) con modificaciones, en la que no se observaron alteraciones en la integridad de los MPs y la tasa de ingestión fue similar a la que se reporta para estos organismos.

A Colombian coal from La Loma, Cesar, Colombia, field was characterized by Fourier transform infrared photoacoustic spectroscopy. Spectral analysis was focused on the mid-infrared, where previous publications have shown remarkable changes in the coal structure. Instrumental parameters of the infrared spectrometer were investigated for optimal spectra acquisition. Optimal parameters are a mirror velocity of 0.16 cm/s, a number of scans of 512, and a resolution of 2 cm⁻¹. Results of Fourier transform infrared photoacoustic spectroscopy were compared with Fourier transform infrared attenuated total reflectance for validation. Both techniques can be implemented with a minimum sample preparation. Finally, vibrational modes of the functional groups were identified.