Ratiometric fluorescent chemosensor based on the block copolymer of poly(N‐isopropylacrylamide)‐b‐poly(N‐vinylcarbazole) containing rhodamine 6G and 1,8‐naphthalimide moieties

Abstract

AbstractWe have synthesized an amphiphilic block copolymer poly(N‐isopropylacrylamide)‐b‐poly(N‐vinylcarbazole) containing 1,8‐naphthalimide and spirolactam rhodamine 6G moieties via reversible addition‐fragmentation chain transfer radical polymerization. The photoluminescence (PL) spectrum of the poly(N‐vinylcarbazole) block well matches the absorption spectrum of the 1,8‐naphthalimide moiety and the enhanced emission with a peak at 510 nm from the 1,8‐naphthalimide moiety is found in the block copolymer film for excitation at 330 nm. The 560‐nm emission from the rhodamine 6G moiety is observed as the block copolymer film sprayed by Britton‐Robinson (B‐R) buffers or Fe3+ aqueous solutions for excitation at 330 and 400 nm. The PL intensity at 560 nm is markedly increased for the pH value of the B‐R buffer lower than 3.0 or the Fe3+ concentration in water higher than 5 × 10−4 M. The 560‐nm PL intensity is much higher for the block copolymer film photoexcited at 330 nm than that photoexcited at 400 nm due to double‐step resonance energy transfer. The PL intensity ratio of 560 to 510 nm (I560/I510) is dependent on the resonance energy transfer from 1,8‐naphthalimide to rhodamine 6G, which is sensitive to the concentrations of H+ and Fe3+ ions in water.