Laser-induced periodic surface structures (LIPSS) have gained significant attention due to their ability to modify the surface morphology of materials at the micro-nanoscale and show great promise for surface functionalization applications. In this study, we specifically investigate the formation of LIPSS in silicon substrates and explore their impact on surface-enhanced Raman spectroscopy (SERS) applications. This study reveals a stepwise progression of LIPSS formation in silicon, involving three distinct stages of LIPSS: (1) integrated low-spatial-frequency LIPSS (LSFL) and high-spatial-frequency LIPSS (HSFL), (2) principally LSFL and, (3) LSFL at the edge of the irradiated spot, elucidating the complex interplay between laser fluence, pulse number, and resulting surface morphology. Furthermore, from an application standpoint, these high-quality multi-scale periodic patterns lead to the next step of texturing the entire silicon surface with homogeneous LIPSS for SERS application. The potential of LIPSS-fabricated silicon substrates for enhancing SERS performance is investigated using thiophenol as a test molecule. The results indicate that the Au-coated combination of LSFL and HSFL substrates showcased the highest enhancement factor (EF) of $1.38\times {10}^6$. This pronounced enhancement is attributed to the synergistic effects of localized surface plasmon resonance (LSPR) and surface plasmon polaritons (SPPs), intricately linked to HSFL and LSFL characteristics. These findings contribute to our understanding of LIPSS formation in silicon and their applications in surface functionalization and SERS, paving the way for sensing platforms.

Laser micromachining has attracted considerable interest because of its wide range of applications across nearly all manufacturing sectors and mostly in semiconductors such as silicon. However, modern micro-manufacturing demands progressive product miniaturization, high accuracy, and high-precision material removal. For this purpose, a fundamental study of the interaction between ultrashort laser pulses and silicon will be valuable for studying ablation characteristics and ablation performance. The femtosecond laser pulse interaction with the silicon is divided into five parts: (a) the interaction of laser light with the carriers, (b) variation of the carrier density and carrier temperature, (c) energy exchange between carriers and lattice, (d) thermomechanical response of the material, and (e) ablation. The evolution of the carrier density and carrier-lattice energy coupling equation is solved simultaneously to determine the optimum value of the ablation width and ablation depth of femtosecond laser pulses on the silicon. The first time, 2D axial symmetry thermal and non-thermal ablation profiles were compared with the experimental result at fluence ranging from 0.75 to 9 J cm⁻² at the wavelength of 515 nm and 180 fs laser on the silicon sample. A comparative study of damage thresholds from experiments and simulations is presented. The concordance between model calculations and experimental data demonstrates that fs laser ablation is thermal in nature in low fluence regime, whereas it is non- thermal in a high-fluence regime. Fundamental information such as the time evolution of the carrier density, carrier temperature evolution, and lattice temperature evolution can be obtained from the simulation results.

This paper addresses the growing concern surrounding microplastic pollution, particularly within the textile industry, and the associated potential health risks linked to the inhalation and ingestion of microplastic particles. Microplastics, defined as plastic particles smaller than five millimeters, are increasingly found not only in aquatic environments, but also in soils, air, and food. Although research on the health impacts of microplastics is still emerging, early studies indicate that these particles could contribute to health issues, including oxidative stress, inflammation, and cardiovascular diseases. Notably, individuals with higher concentrations of plastics in arterial plaques are more susceptible to heart attacks and strokes. In the textile industry, synthetic fibers such as polyester, nylon, and acrylic release microplastics into the air during production. The paper discusses a study conducted in a textile company that processes polyester yarns, where airborne microplastic concentrations were measured at various locations throughout the day. Particle sizes ranging from 0.3 nm to 10 nm were analyzed, revealing the presence of polyester polymers in the particulate matter. These findings underscore the widespread nature of microplastic pollution, particularly in industrial settings, and raise concerns about the health risks associated with prolonged exposure to airborne microplastics. While further research is necessary to fully understand the extent of these health impacts, preliminary data suggest a troubling link between microplastic inhalation and cardiovascular conditions.

Upon excitation at 796 nm, Nd(3+)-doped BaCl(2) single crystals show several upconverted fluorescence bands in the visible spectral range, with the most intense bands at 530, 590 and 660 nm, in addition to the typical fluorescence bands in the infrared spectral range. The power dependence of the infrared fluorescence and the two-photon upconversion fluorescence intensities as well as the corresponding radiative lifetimes have been investigated. No 'saturation' of the fluorescence intensities was observed upon increasing the excitation power.

Analytical routes for sampling and analysis of microplastic particles in the range of several 10 µm to 1000 µm are well established in environmental research. However, the current scientific efforts are targeting human health impact with an enhanced focus on nanoparticle analysis in drinking water, the food chain, and its disposition in the human body. A major challenge lies in the availability of cascade filter setups spanning several orders of magnitude down to 10 nm dimensions in a single filtration workflow allowing fast and reliable routines for size‐selective nano‐ and microplastic (NMP) particle analysis. In this work, we present a novel cascade filter system containing filters made of microporous Si (pore size >10 µm) and nanoporous Al₂O₃ (pore size 100 nm), thus realizing the corresponding NMP size selectivity. Inorganic filter materials are chosen due to their beneficial properties as substrates for NMP particle analysis, which are nonpolymer materials with high planarity for micro‐spectroscopy investigations. In our first experiments, we demonstrate the successful NMP size separation on Si and Al₂O₃ filter substrates. For this purpose, we implement a well‐defined NMP test material composed of a mixture of polyethylene terephthalate microplastic reference material and monodisperse nanoscale polystyrene particles. The NMP test material is applied in a laboratory filtration workflow for samples in liquid solution. Both filter stages are subsequently investigated with optical microscopy, electron microscopy (scanning electron microscopy), Raman spectroscopy, and scanning force microscopy (atomic force microscopy) to demonstrate their applicability as combined NMP particle analytic substrates. Here, we characterize the fundamental NMP properties such as particle shape, size, and spectroscopic fingerprints—optical and chemical—both qualitatively and quantitatively. Finally, requirements and limitations for a standardized NMP filtration and analytic workflow will be discussed.