Abstract
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.
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