Naphthalimide-functionalized pH-responsive amphiphilic block copolymer nanoparticles

An amphiphilic block copolymer, poly(ethylene glycol)- b -poly( N -vinyl carbazole), functionalized with a 1,8-naphthalimide fluorescent signaling moiety containing a pH-responsive piperazinyl recognition unit (PEG- b -PVK- co -PNA), was synthesized via reversible addition-fragmentation chain transfer polymerization. The block copolymer demonstrates a low molar mass dispersity and spontaneously self-assembles into uniform nanoparticles in aqueous media, serving as a fluorescent sensor for detecting hydrogen ion. The emission from the PVK block is effectively quenched, whereas the 1,8-naphthalimide moiety exhibits a pronounced fluorescence enhancement at 505 nm due to Förster resonance energy transfer between the PVK donor and the 1,8-naphthalimide acceptor in the copolymer nanoparticles. The photoluminescence intensity at 505 nm displays a linear correlation with decreasing pH values in the range 3.0–6.5 for the copolymer nanoparticles in acidic medium, highlighting the block copolymer's potential for quantitative pH sensing in acidic environments. © 2025 Society of Chemical Industry.