Novel fluorescent poly(2-(acetoacetoxy)ethyl methacrylate)(PAAEMA) latexes have been synthesized by miniemulsion polymerization employing a polymeric costabilizer. Nanoscale aggregates of macromolecules bearing beta-dicarbonyl are formed in the prepared latex particles. Ammonia and the beta-dicarbonyl aggregates assemble a supramolecular complex, which exhibits strong visible fluorescence under UV light. The formation of the complex is confirmed by the characteristic absorption peak located at about 275 nm in UV-Vis spectra. The absorption spectrum has been found to be applicable for ammonia detection. Atomic Force Microscopy (AFM) studies of surface morphology reveal that gas-sensing properties of the PAAEMA thin films involve the reversible absorption and desorption of ammonia. PAAEMA thin films are sensitive to ammonia gas and have a short response time of 80 s when exposed to 54 ppm of ammonia gas concentration. (C) 2011 Elsevier Inc. All rights reserved.