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ABSTRACT:The process of electrospinning is very suitable for obtaining fibers with a diameter on a nanometer scale. Such fibers can be spun from almost all kinds of known polymers, copolymers, and polymer blends. In this work, we present cellulose nanofibers obtained by the electrospinning process from spinning dopes containing cellulose dissolved in an N-methylmorpholine-N-oxide/water system. Under different electrospinning process conditions, cellulose fibers, a nonwoven fiber network, and a cellulose membrane were obtained. The fibers were examined with scanning electron microscopy. The diameters of the fibers were in the submicrometer range.

Cellulose fibers modified with silver nanoparticles were prepared using N-methylmorpholine-N-oxide as a direct solvent and analyzed in this study. Silver nanoparticles were generated as a product of AgNO 3 reduction by means of three methods under varying light conditions (daylight and darkroom). Influence of generating conditions on the size, the type and the number weighting of created nanoparticles was examined. Dynamic Light Scattering technique (DLS) was used for determination of those parameters. DLS analysis showed that the best method, i.e. the one that allowed the generation of the greatest number of silver nanoparticles with the smallest diameter and the smallest agglomerates, was incubation of cellulose pulp with AgNO 3 in a darkroom for 24 h. Mechanical and hydrophilic properties of all obtained fibers were also determined. Results showed that the method of silver nanoparticles generation did not influence significantly mechanical and hydrophilic properties of the modified fibers, because in all cases only small decreases of the studied parameters were observed.

In the present research, nanocomposite antibacterial cellulose fibers of Lyocell type modified with nanosilver particles and nanosilica were obtained. Nanosilver particles were generated by the chemical reduction of silver nitrate (AgNO 3 ) in 50% water solution of N-methylmorpholine N-oxide (NMMO), which was applied as a direct cellulose solvent for the production of Lyocell fibers. The main aim of this study has been to obtain antibacterial cellulose fibers modified with silver nanoparticles, which are entirely safe for contact with human tissue. Taking into account the potential medical applications of the obtained fibers, the antibacterial activity and cytotoxicity of silver nanoparticles enclosed in fibers were examined in human and mouse cells. Considering the size of the silver nanoparticles with nanosilica in NMMO and their physical properties, the time of generation was the subject of a thorough analysis. The basic physical properties of the nanoparticles introduced in the fibers were tested using the UV/VIS, DLS and TEM methods. The basic properties of the fibers, namely the mechanical and hydrophilic ones, and the average degree of polymerisation of the cellulose fibers were estimated. The conditions of the synthesis of nanoparticles in NMMO with nanosilica were optimised. The results have confirmed that fibers with high-quality antibacterial properties, safe for human tissue and suitable for medical purposes, could be obtained.

UV-active cellulose fibers were obtained by dry-wet method spinning an 8 % by weight acellulose solution in N-methylomorpholine-N-oxide (NMMO) modified by europium-doped gadolinium oxyfluoride Gd 4 O 3 F 6 :Eu 3? containing 5 mol (%) of the dopant. Photoluminescent nanoparticles were introduced in the in powder form into a polymer matrix during the process of cellulose dissolution in NMMO. The dependencies of emission intensity on excitation energy and the concentration of Gd 4 O 3-F 6 :Eu 3? nanoparticles in the final cellulosic products were examined by photoluminescence spectroscopy (excitation and emission). The fiber structure was studied by X-ray powder diffraction analysis. The size and dispersity of the nanoparticles in the polymer matrix were evaluated using scanning electron microscopy and X-ray microanalysis. The influence of different concentration particles (in the range from 0.5 to 5 % by weight) on the mechanical properties of the fibers, such as tenacity and elongation at break, were determined.

ABSTRACT:The sol-gel method is one of the most suitable ways for producing glasses, glass films, glass fibers, and glass nanoparticles. The relatively mild reaction conditions and simplicity of the sol-gel method make it an excellent tool for producing substances with precisely tailored properties. This technique opens the possibility for the synthesis of various new compounds, including pH sensors, ion sensors, bioactive nanoparticles, dyes carriers, and so forth. An attempt was made to combine the sol-gel technique with the advanced technology in the production of cellulose fibers in order to obtain fibers with new and unique properties. Cellulose fibers were prepared with N-methylmorpholine-Noxide as the direct solvent. The obtained fibers contained up to 30% (w/w) silicon dioxide nanoparticles. In order to observe the influence of the modifier on the fibers, their mechanical properties were examined. Modified fibers were also examined by means of thermogravimetry, wide-angle X-ray scattering, and 29 Si-NMR solid-state spectroscopy.

The objective of the presented research was to determine the influence of cellulose coating, obtained from the cellulose solution in N-Methylmorpholine N-oxide (NMMO), on the structural and mechanical properties of paper. The effect of heating time of paper samples coated with cellulose dissolved in NMMO was also investigated. Depending on the heating time of the coating, a continuous or porous layer was obtained. Coating without any heating stage yielded a continuous cellulose layer of hydrophobic properties (higher contact angle in comparison to base paper), and paper of higher smoothness and increased tear resistance. Analysis of the paper samples showed that cellulose coating not only changed the surface properties of paper, but also significantly improved paper strength properties, such as the tensile index, elongation, bursting strength index and double folds number. Despite the process' limitations (e.g. necessity of removing the NMMO), this method can be considered as a novel approach for paper property modification.

This paper describes a method for manufacturing luminescent cellulose fibers. Good optical properties of cellulose fibers under UV-C illumination were achieved by incorporating ZrO 2 (0.5 mol% of Eu 3? ) stabilized by Y 2 O 3 (7 mol%) into the fiber structure's particles. Fibers were obtained from 8 wt% cellulose solution in N-methylmorpholine N-oxide (NMMO) with the addition of a luminescent modifier in the range between 0.5 and 10 wt%. The physicochemical and mechanical parameters and the structure of these fibers were examined.