Cu²⁺-Induced Micellar Charge Selective Fluorescence Response of Acridine Orange: Effect of Micellar Charge, pH, and Mechanism

Abstract

Photophysical properties of cationic Acridine Orange (AO) have been studied in different micellar environments [anionic SDS (sodium dodecyl sulfate), nonionic TX (TritonX-100), and cationic CTAB (cetyl trimethyl ammonium bromide)] at different pH, in the presence of a metal ion (Cu(2+)). At pH ∼ 8, addition of Cu(2+) results in AO fluorescence quenching in the presence of SDS micelle, enhancement of the same in the presence of TX micelle, and remaining unaltered in the presence of CTAB micelle. At pH ∼ 2, addition of Cu(2+) results in AO fluorescence quenching only in the presence of SDS micelle, and it remains mostly unaffected in the presence of TX and CTAB. Availability of Cu(2+) toward AO and binding of Cu(2+) with AO at the charged micellar interface are responsible for this pH-dependent Cu(2+)-mediated micellar charge selective fluorescence pattern.