Silicon nanoparticles (SiNPs) are attracting attention for applications in various fields, from energy storage to bio-imaging. One of their main advantages is good photoluminescence (PL) properties combined with the relatively high bio-compatibility. Here, we fabricated SiNPs by the laser ablation of silicon single crystal in de-ionized water, employing simultaneously the picosecond pulse laser (150 ps, 1064 nm, 7 mJ/pulse) and a continuous wave (CW) laser (532 nm, 270 mW). TEM analysis (bright field TEM, HRTEM, HAADF, EDS) clearly shows that the introduction of the CW laser significantly increases the crystallinity of the produced nanoparticles, which may be crucial for many optical and electronic applications. The obtained SiNPs exhibit good blue photoluminescence properties, and the introduction of the CW laser into the fabrication process leads to the considerable increases in the photoluminescence. Additionally, we conducted a detailed analysis on the aging-time dependence and the excitation wavelength-dependent PL. The results indicate that the blue photoluminescence may be ascribed to quantum confinement effect, interface related states, and defect in the O-containing layer (shell) of the nanoparticles. We demonstrate that the relative share of these mechanisms in overall PL is significantly affected by the introduction of the CW laser to the pulse laser ablation and it may improve the applicability of the Si nanoparticles produced to a wide variety of fields.

The ecological aspect of substituting synthetic materials with natural materials is of great interest nowadays. This paper examines the percentage of lignocellulose-based fillers that can be added to a synthetic polymer matrix to ensure the resulting biocomposite maintains its dielectric properties. Biocomposites were made from isotactic polypropylene (iPP) and various proportions (20%, 30%, and 40%) of oats, rye, wheat, and barley bran and granules from corn cobs using a Brabender plastograph and a hydraulic hot press. From a morphological analysis, it was noted that the particles were well incorporated into the polymer matrix. The frequency-dependent behavior of the dielectric properties was analyzed across a frequency range from 30 Hz to 60 kHz at a room temperature of 23 °C and 35% relative humidity. The obtained results showed that the incorporation of biomasses into the iPP matrix increased the values of the dielectric properties across the entire measured frequency range. The samples with wheat showed the most stable values of the dielectric parameters with frequency changes, for all three concentrations. A linear regression analysis showed a very high coefficient of determination (R² = 0.997) between the effective dielectric permeability and filler concentration at 30 Hz for the samples with wheat. Furthermore, the biocomposite iPP/20% wheat showed a desirable balance of dielectric properties for electronic applications. The results showed that biocomposites obtained by adding cheap lignocellulose-based biomass, such as bran or granules from corn cobs, to a synthetic polymer matrix have a great potential for use as electrically insulating materials because their dielectric parameters are comparable to those of standard insulating materials.