a highly - sensitive , rapid response fluorescent probe is based on the affinity of a polymer matrix for an analyte of interest . the probe includes a polymer matrix and a dye immobilized in the matrix . the polymer matrix has an affinity for an analyte of interest and the dye has little or no sensitivity to the analyte of interest when excited by an excitation source in a free state but has significant sensitivity to the analyte of interest when excited by the excitation source when immobilized in the matrix . sensors incorporating the polymer / fluorophore probes of the present invention have the sensitivity and rapid response needed for detection of chemical agent and biological materials . sensors using the probes provide sensitivity to sarin at several hundred parts per trillion in one second or less . that is a notable advance over state - of - the - art detectors that require preconcentration steps , which in turn restrict response times to one minute or more . a wide - range of near - infrared excitable fluorophores are used as sensitive probes for analytes not detectable when the fluorophores are outside the polymer matrix . the present sensors provide early warning of the presence of toxic chemicals , provides for on - line analysis of trace materials in chemical and biological processing operations and biomedical processing operations , and provides for effective biomedical and environmental monitoring .