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Composite up-conversion luminescent films containing a nanocellulose and SrF2:Ho particles

Fedorov, P. P., Luginina, A. A., Kuznetsov, S. V., Voronov, V. V., Lyapin, A. A., Ermakov, A. S., Pominova, D. V., Yapryntsev, A. D., Ivanov, V. K., Pynenkov, A. A., Nishchev, K. N.
Cellulose 2019 v.26 no.4 pp. 2403-2423
acid hydrolysis, cellulose, cellulose nanofibers, composite films, crystal structure, dispersions, evaporation, luminescence, mixing, nanocomposites, nanocrystals, nanoparticles, optical properties, photonics, polymerization, raw materials, solvents, sulfates, sulfuric acid, ultrasonic treatment, wood pulp
The synthesis of up-conversion luminescent composite films based on a nanocellulose matrix containing Sr₁₋ₓHoₓF₂₊ₓ particles was proposed. The combination of sulfuric acid hydrolysis and ultrasonication allowed us to synthesize a series of stable nanocellulose dispersions from various raw materials (powdered sulphate bleached wood pulp, Blue Ribbon filter paper, and microcrystalline cellulose Avicel). The size distribution of cellulose nanoparticles in the aqueous dispersions was determined. Cellulose nanocrystals (CNC) and/or cellulose nanofibrils (CNF) dispersions were used to fabricate thin films by solution casting followed by solvent evaporation under ambient conditions. The size and shape of cellulose nanoparticles, surface morphology, crystallinity index of nanocellulose, polymerization degree, and optical properties were studied. By mixing aqueous dispersions of CNC with up-conversion Sr₁₋ₓHoₓF₂₊ₓ particles, homogeneous suspensions were obtained. Finally, a solution casting technique was used to prepare CNC/Sr₁₋ₓHoₓF₂₊ₓ and CNC/CNF/Sr₁₋ₓHoₓF₂₊ₓ nanocomposite films. CNC/CNF dispersions were utilized for the production of flexible, durable, transparent composite films. The synthesized nanocomposites demonstrated intense red luminescence upon Ho³⁺ excitation by 1912 nm laser radiation. The obtained up-conversion luminescent composite films can be considered as a promising material for photonics, in particular for near-IR laser radiation visualization, luminescent labeling and luminescent sensorics.