PNNL

Abstract

A method for signal amplification in the detection of vapors with luminescence-based sensors is described. Amplification involves energy transfer between two or more fluorescent chromophores in a carefully selected polymer matrix. A quantitative model has been derived that can be applied to any luminescence sensors comprising donor-acceptor pairs, and it can be generalized to multichromophore systems with n-chromophores leading to n-fold signal amplification. Signal amplification has been demonstrated experimentally in the fluorescent sensing of dimethl methlphosphonate (DMMP) using two dyes, 3- aminofluoraten (AM) and Nile Red (NR), in a hydrogen bond acidic polymer matrix. The selected polymer matrix quenches the fluorescence of both dyes and shifts dye emission and absorption spectra relative to more inert matrices. Upon DMMP sorption, the AM fluorescence shifts to the red at the same time the NR absorption shifts to the blue, resulting in more band overlap and increased energy transfer between chromophores. In addition, emission of both chromophores is enhanced. Using an excitation wavelength tuned to the AM dye, absolute signal magnitude upon DMMP exposure in two-dye film was an order of magnitude greater than using single-dye NR containing film. The ratio of response signal under vapor exposure to the signal prior to exposure was 250 for the two-dye film compared to 15 single dye films. The two-dye approach to signal amplification also significantly increases selectivity relative to potentially interfering vapors. Experimental results to date, favor a reabsorption mechanism over a Forster radiationless direct energy transfer mechanism.