1：Experimental Design and Method Selection:

The study involved synthesizing nanocellulose dispersions via sulfuric acid hydrolysis and ultrasonication, followed by film fabrication using solution casting. Up-conversion Sr1-xHoxF2+x particles were incorporated into the films.

2：Sample Selection and Data Sources:

Raw materials included microcrystalline cellulose (Avicel), powdered bleached woodkraft cellulose (PCC-

3：25), and filter paper (Blue Ribbon). Sr1-xHoxF2+x powders were prepared as described. List of Experimental Equipment and Materials:

Equipment included centrifuges (Eppendorf 5804), sonicators (UZG13-01/22), X-ray diffractometer (Bruker D8 Advance), DLS spectrometer (Photocor Complex), SEM (NVision 40), FTIR spectrometer (INFRALUM FT-08), spectrophotometer (Cary 5000), DSC (Netzsch DSC 404 F1), TG (Netzsch TG 209 F1), and luminescence spectrophotometer (Horiba FHR 1000). Materials included sulfuric acid, dialysis tubing, and various cellulose samples.

4：0). Materials included sulfuric acid, dialysis tubing, and various cellulose samples. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Hydrolysis was performed with sulfuric acid at specific concentrations and temperatures, followed by washing, centrifugation, dialysis, and sonication. Films were cast on Petri dishes and dried. Composite films were prepared by mixing nanocellulose dispersions with SrF2:Ho powders and sonicating.

5：Data Analysis Methods:

XRD for crystallinity index and coherent scattering domains, DLS for particle size distribution, viscosity method for polymerization degree, SEM/EDX for microstructure and composition, FTIR for functional groups, UV-Vis for transmission, DSC/TG for thermal properties, and luminescence spectroscopy for up-conversion properties.