1：Experimental Design and Method Selection:

The study utilized the sol-gel method for synthesizing ZnO nanoparticles, followed by surface modification with chitosan and niacinamide. Characterization techniques included FT-IR, XRD, SEM, TEM, TGA, and zeta potential analysis.

2：Sample Selection and Data Sources:

ZnO nanoparticles were synthesized from zinc acetate and oxalic acid dihydrate. Chitosan and niacinamide were used for surface modification.

3：List of Experimental Equipment and Materials:

Equipment included Fourier transform infrared spectroscopy (Bruker), X-ray diffractometer (Rigaku Corporation), field-emission scanning electron microscopy (Hitachi), biotransmission electron microscopy (Hitachi), thermogravimetric analyzer (PerkinElmer), and dynamic light scattering-zeta potential analyzer (Zetasizer Nano ZS90). Materials included zinc acetate dihydrate, oxalic acid dihydrate, niacinamide, and medium molecular weight chitosan.

4：0). Materials included zinc acetate dihydrate, oxalic acid dihydrate, niacinamide, and medium molecular weight chitosan. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: ZnO nanoparticles were synthesized, followed by surface modification with chitosan and niacinamide. The composites were characterized, and their UV protection and skin lightening effects were evaluated.

5：Data Analysis Methods:

Data from characterization techniques were analyzed to confirm the synthesis and coating of ZnO nanoparticles. UV protection and skin lightening effects were evaluated through transmission, reflectance, SPF measurements, and tyrosinase inhibition assays.