Reinvestigation on photoluminescence of 7-hydroxyflavone in aqueous medium: Proficient fluorescence enhancement

Abstract

Fluorescence properties of 7-hydroxyflavone (7HF) have been explored in different solvents and water mixtures with steady-state and time-resolved techniques. 7HF display weak fluorescence in protic and aprotic solvents. Successive addition of H2O fractions induces fluorescence turn-on response accompanied by the emergence of a new green wavelength band (∼527 nm) due to the formation of anionic species and suppression of normal and hydrogen-bonded species. Jobs and ratiometric plots demonstrated the nature of complexation and fluorescence enhancement of 7HF with H2O in different solvents. Lower limits of detection depict the superiority of 7HF over other H2O sensitive systems. Time-resolved experiments help in understanding the governing parameters involved in the 7HF:H2O complexation. Theoretical calculations have been performed to decipher the molecular geometry of 7HF in different environments, which supports the experimental interpretations to a large extent. Hence, the present study can potentially detect a wide range of water content in organic solvents. Additionally, a practical application using a mobile phone make the system quite useful in detecting H2O in real and commercial samples.