Plant fibers are sustainable sources of materials for many industries, and can be obtained from a variety of plants. Cellulose is the main constituent of plant-based fibers, and its properties give the characteristics of the fibers obtained. Detailed characterization of cellulosic fibers is often performed after lengthy extraction procedures, while fast screening might bring the benefit of quick qualitative assessment of unprocessed stems. The aim of this research was to define some marker spectral regions that could serve for fast, preliminary qualitative characterization of unprocessed stems from some textile plants through a practical and minimally invasive method without lengthy extraction procedures. This could serve as a screening method for sorting raw materials by providing an accurate overall fingerprint of chemical composition. For this purpose, we conducted comparative Fourier Transform Infrared Spectroscopy (FT-IR) prospecting for quality markers in stems of flax (Linum usitatissimum L.), velvet leaf (Abutilon theophrasti Medik.), hemp (Cannabis sativa L.) and jute (Corchorus olitorius L.). Analysis confirmed the presence of major components in the stems of the studied plants. Fingerprint regions for cellulose signals were attributed to bands at 1420–1428 cm⁻¹ assigned to the crystalline region and 896–898 cm⁻¹ assigned to the amorphous region of cellulose. The optimization of characterization methods for raw materials is important and can find immediate practical applications.

Plasticized poly(lactic acid) (PLA) samples with embedded Cu-doped ZnO powder functionalized with Ag nanoparticles composites were prepared by melt blending processing technique. The effect of ZnO:Cu/Ag nanoparticles on the properties of plasticized PLA was investigated in terms of structural (by Attenuated total reflectance – Fourier Transform Infrared – ATR-FT-IR, X–Ray Diffraction analysis – XRD) and morphological (using Scanning Electron Microscopy – SEM and Transmission Electron Microscopy – TEM examination) modifications, thermal (Differential Scanning Calorimetry – DSC), mechanical (transmittance, tensile strength), barrier antimicrobial properties and also in respect to migration of Cu, Zn an Ag nanoparticles into food simulants. It was found that the increase of nanoparticle content (from 0.5 to 1.5 wt%) of PLA formulations leads to the increase of the degree of crystallinity of PLA. The overall migration of all samples into three food simulants was below 10 mg·dm–2, accepted value according to EU Regulation No 10/2011 for plastic materials and articles intended to come into contact with food. Based on the obtained results it can conclude that the optimum composition is PLA/ZnO:Cu/Ag 0.5, this bionanocomposite offering suitable mechanical and thermal properties, good barrier properties to ultraviolet light, water vapour, oxygen and carbon dioxide, antibacterial activity and low migration amount of nanoparticles into food simulants