Phenothiazine and triphenylamine-based fluorescent Schiff bases for the dual application of white light generation and H2O2 sensing

Abstract

Two Schiff bases based on triphenylamine and phenothiazine, namely DTPA-SB and DPTZ-SB, respectively, were synthesized via facile organic transformations. The mixing of these two molecules with rhodamine B dye (Rh-B) resulted in efficient white light generation in the solution state as well as in the ionic liquid medium of [Bmim][Cl] with the Commission Internationale de l’Eclairage (CIE) coordinates of (0.33, 0.35) and (0.34, 0.35), respectively. Notably, the generation of white light in the ionic liquid medium has been reported for the first time. Several mechanistic studies, namely fluorescence titration, spectral overlap, Förster distance calculation and DFT studies, established that the mechanism of WLE is Förster resonance energy transfer with simultaneous emission. On a parallel note, DTPA-SB showed an excellent fluorescence sensing response towards 30% H₂O₂ with a remarkable limit of detection (LOD) of 8.4 × 10⁻⁷ M, while DPTZ-SB exhibited a slight decrease in the emission intensity with a LOD of 1.96 × 10⁻⁷ M. Both DTPA-SB and DPTZ-SB were specifically selective for 30% H₂O₂ without interference from fifteen other chemical species. Since DTPA-SB exhibited significant response towards hydrogen peroxide detection, a paper-based fluorescent sensor device was fabricated by embedding DTPA-SB on the filter paper with a LOD of 2.3 × 10⁻⁹ M. Additionally, a smartphone color-scanning app was tuned with the paper-based sensors to perform scanometric tests. A paper-based device for hydrogen peroxide sensing by applying a simple fluorescent Schiff base is reported herein for the first time.