Home > Chemical > Technology > Molecular Spectroscopy > Amplifying Fluorescence Polymers (AFP)

Chemical sensors have been developed based on amplified fluorescence quenching of solid-state conjugated polymer films (AFP). These sensors consists of a glass capillary tube whose interior is coated with a polymer film comprised of a conjugated backbone with pentiptycene groups. In operation, the AFP polymer is excited to a fluorescent state using a light source external to the capillary tube. An air pump is then used to draw the sample through the capillary; compounds containing nitroaromatic groups (TNT, RDX, etc.) bind to the polymer, causing fluorescence to be quenched. The change in fluorescence is read as a change in response at a photometer positioned axially to the capillary. In conventional fluorescent-based sensors, the signal arises due to 1:1 analyte to chromophore binding.  In AFP, because the polymer chains are electronically conjugated, binding at any point along the polymer chain results in complete quenching of all sites on the polymer. The result is that a single analyte molecule activates multiple chromophores.  The effective amplification in response by this technique over monomeric quenching is estimated to be from 100X to 1000X. It is primarily used in vapor sensing applications such as detection landmines and other explosive devices. AFP technology is relatively new.  As such, it is employed in a limited number of sensor devices, nearly all handheld in configuration.