Fluorescence detection of nitrogen dioxide with perylene/PMMA thin films

Thin films of polymethylmethacrylate (PMMA) doped with perylene provide sel ective, robust and easily prepared optical sensor films for NO2 gas with su itable response times for materials aging applications. The materials are r eadily formed as 200 nm thin spin cast films on glass from chlorobenzene so lution. The fluorescence emission of the films (lambda (max) = 442 nm) is q uenched upon exposure to NO2 gas through an irreversible reaction forming n on-fluorescent nitroperylene. Infrared, UV-VIS and fluorescence spectroscop ies confirmed the presence of the nitro adduct in the films. In other atmos pheres examined, such as air and 1000 ppm concentrations of SO2, CO, Cl-2 a nd NH3, the films exhibited no loss of fluorescence intensity over a period of days to weeks. Response curves were obtained for 1000. 100 and 10 ppm N O? at room temperature with equilibration times varying from hours to weeks . The response curves were fit using a numerical solution to the coupled di ffusion and a nonlinear chemical reaction problem assuming that the situati on is reaction limiting. The forward reaction constant fitted to experiment al data was k(f) similar to 0.06 (ppm min)(-1). (C) 2001 Elsevier Science B .V. All rights reserved.