1：Experimental Design and Method Selection:

The study used a solvothermal method to synthesize Eu3+ and La3+ co-doped BiOCl ultrathin nanosheets, with characterization techniques including XRD, SEM, TEM, HRTEM, AFM, XPS, and fluorescence spectroscopy to analyze structure, morphology, and luminescence properties.

2：Sample Selection and Data Sources:

Samples were prepared with varying concentrations of La3+ ions (x = 0, 0.1, 0.15, 0.2, 0.3) in Bi1-0.1-xEu0.1LaxOCl, using analytical grade chemical reagents without further purification.

3：1, 15, 2, 3) in Bi1-1-xEu1LaxOCl, using analytical grade chemical reagents without further purification. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included D/Max2550 X-ray diffractometer (Rigaku), FE-SEM (S4800 Hitachi), TEM and HRTEM (JEM-2100 JEOL), AFM (Bruker-Nano N8 NEOS), XPS (ESCALAB MKII VG Scientific), fluorescence spectrometer (F-4600 Hitachi). Materials included Eu(NO3)3·6H2O, La(NO3)3·6H2O, Bi(NO3)3·5H2O, PVP, mannitol solution, NaCl, deionized water, ethanol.

4：Experimental Procedures and Operational Workflow:

Stoichiometric amounts of reagents were dissolved, mixed with NaCl solution, transferred to a Teflon-lined autoclave, heated at 160°C for 3h, cooled, washed, and dried. Characterization was performed as per standard protocols for each technique.

5：Data Analysis Methods:

XRD patterns were analyzed for phase identification, XPS spectra were deconvoluted using Gaussian fitting, luminescence spectra were recorded and compared, decay curves were fitted with bi-exponential functions, and CIE coordinates were calculated from emission data.