In our previous work , SPANI was prepared by direct sulfonation of emeraldine salt form of PANI with chlorosulfonic acid in an inert solvent. The material characterizations of SPANI were carried out using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). Detailed photophysical properties of SPANI in aqueous medium were investigated using steady state (absorption as well as fluorescence emission) and time-resolved (time-correlated single photon counting, TCSPC, set up for fluorescence lifetime measurement) spectroscopic techniques. The steady state absorption spectra of SPANI consist of a relatively sharp peak at 320 nm (3.88 eV), a shoulder at about 440 nm (2.82 eV) and a broad band at 650 nm (1.91 eV). These bands are attributed to π-π* transition due to the benzenoid unit, polaron transition and charge transfer exciton like transition due to the quinoid unit, respectively. The steady state fluorescence emission of SPANI in aqueous medium is due to the benzenoid unit upon photoexcitation by π-π* transition from ground singlet state to first excited singlet state (S0 → S1), and ranges from 350 nm to 525 nm (approximately).