1：Experimental Design and Method Selection:

The study used solution techniques to prepare PTCDI-C5 solutions with different molarities, concentrations, and solvents. Optical parameters were calculated using the single oscillator model (Wemple-DiDomenico equation) and other theoretical models for refractive index, absorption, and sensing properties.

2：Sample Selection and Data Sources:

PTCDI-C5 molecule, toluene, chlorobenzene, and chloroform solvents were purchased from Sigma-Aldrich Co. Solutions were prepared with specific concentrations (

3：347, 781, 34, 512, 269 mg/liter) and volume percents (06, 135, 405, 607, 911% V) in chlorobenzene, and with 436 mM in different solvents. List of Experimental Equipment and Materials:

AND-GR-200 Series Analytical Balance for weighing, cylindrical cuvettes (Hellma QS-100) of

4：5 mL volume and 10 mm optical path length, Shimadzu model UV-1800 Spectrophotometer for optical measurements. Experimental Procedures and Operational Workflow:

Solutions were prepared by dissolving weighed PTCDI-C5 in solvents, and optical measurements (absorbance, transmittance) were recorded in the wavelength range 1100-190 nm at room temperature.

5：Data Analysis Methods:

Data were analyzed using equations for refractive index, absorption coefficients, sensitivity, response, and optical band gaps (Tauc relation). Linear fitting and correlation coefficients were used for analysis.