1：Experimental Design and Method Selection:

The study uses a hydrothermal synthesis for BiFeO3 nanoparticles and an electrical poling method assisted by an organic-inorganic composite film to polarize the nanoparticles. Methods include XRD, TEM, SEM, UV-vis spectroscopy, time-resolved PL, photoinduced silver deposition, photoelectrochemical measurements, and radical-trapping experiments to characterize and evaluate the samples.

2：Sample Selection and Data Sources:

BiFeO3 nanoparticles are synthesized and poled under different electric fields (e.g., 220, 420, 540, 690 kV/cm). Data is collected from laboratory experiments using standard chemical reagents and equipment.

3：List of Experimental Equipment and Materials:

Equipment includes Rigaku D/Max-2000 diffractometer, JSM-7800F FESEM, JSM-2100F/HR TEM, UV-3100 Shimadzu spectrophotometer, Edinburgh FLS1000 PL system, ESCALAB 250XI XPS, CHI750E electrochemical analyzer, 500 W Xenon lamp, Teflon-lined stainless steel autoclave, and various chemicals like Bi(NO3)3·5H2O, Fe(NO3)3·9H2O, KOH, PMMA, ethyl acetate, acetone, RhB, MO, AgNO3, IPA, TEOA, BQ, Na2SO4, KCl.

4：Experimental Procedures and Operational Workflow:

Synthesis involves hydrothermal reaction at 180°C for 48 hours. Poling uses PMMA composite film on Cu substrate with DC voltage in silicone oil bath. Characterization includes structural, morphological, optical, and electrochemical analyses. Photocatalytic tests involve dye degradation under visible light, with measurements every 15 minutes.

5：Data Analysis Methods:

Data is analyzed using standard techniques for XRD peak indexing, SEM/TEM imaging, UV-vis reflectance for bandgap calculation, PL decay fitting, photocurrent and EIS measurements, and first-order kinetics for degradation rates.