The optical properties of TBPBB for the selective detection of ClO -were investigated in a THF-H2O mixture. The UV-vis absorption spectra of TBPBB exhibited a blue shift upon the addition of ClO -accompanied by a colour change from purple to yellow (Fig. ). Titration experiments revealed systematic changes in the UV-vis absorption spectra with increasing concentration of ClO -, including the identification of three isoabsorbent points (337 nm, 383 nm, and 464 nm in Fig. as green circled). Additionally, there was a significant enhancement in fluorescence intensity, which was more pronounced compared to other analytes (Fig. ), with a blue shift in the emission band (gradually from 670 nm to 620 nm) and a strong linear correlation with ClO -concentration (R 2 = 0.989), boasting a low LOD of 26 nmol L -1 (Fig. ). These findings emphasized TBPBB's potential as a highly sensitive and selective probe for detecting ClO -in both absorption and fluorescence modes .