Preparation and properties of methylcellulose/nanocellulose/??F^sub 2^:?? polymer-inorganic composite films for two-micron radiation visualizers

The series of polymer-inorganic composite films, containing methylcellulose with incorporated cellulose nanocrystals, and synthesized fluorite-type Ca1-xHoxF2+x nanoparticles or thermally treated particle Ca1-xHoxF2+x, were prepared by mixing aqueous dispersions of the aforementioned ingredients followed by film formation on polystyrene support and drying under air at room temperature and then at 85 °C. Fluorite-type Ca1-xHoxF2+x samples and corresponding films were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), dynamic light scattering (DLS), scanning (SEM) and transmission (TEM) electron microscopy. For the first time, the up-conversion luminescence of the Ho3+-containing composite films (5I7 energy level excitation) has been described for the visible spectrum range. The present paper also proposes a method for visualizing the near infrared (IR) laser radiation with the use of the prepared methylcellulose/nanocellulose/Ca1-xHoxF2+x composite films as well as discussion of the optimal compositions for the said films.