1：Experimental Design and Method Selection:

The study involved steady state and time-resolved fluorescence measurements of 7,8-BQ in a series of organic solvents with varying proticity, polarity, and pH. The effect of hydrogen bonding on protonation was explored in water and trifluoroethanol (TFE).

2：Sample Selection and Data Sources:

7,8-Benzoquinoline (7,8-BQ) was obtained from Sigma Aldrich, USA. Solvents used were of spectroscopic grade. Different pH solutions were prepared using buffer capsules, H2SO4, and NaOH.

3：List of Experimental Equipment and Materials:

Absorption spectra were recorded with Lambda-750, Perkin-Elmer UV/VIS/NIR spectrophotometer and UV–Visible Double beam Systronics Model No: 2203 spectrophotometer. Photoluminescence (PL) spectra were collected by Horiba Jobin Yvon Fluorolog-3. Fluorescence decay times were recorded with Edinburgh-199 time domain spectrometer and Delta Flex TCSPC spectrometer of Horiba Jobin Yvon IBH Ltd.

4：Fluorescence decay times were recorded with Edinburgh-199 time domain spectrometer and Delta Flex TCSPC spectrometer of Horiba Jobin Yvon IBH Ltd. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The concentration of the solutions used was 10-4 M. Steady state and time-resolved measurements were conducted at various pH levels and in different solvents. Decay curves were analyzed using FAST software and Horiba Delta Flex instrument software.

5：Data Analysis Methods:

Time-resolved fluorescence decay curves were analyzed by deconvoluting the observed decay with the instrument response function (IRF) to obtain the intensity decay function represented as a sum of discrete exponentials. Quantum yield was calculated using a reference method.