ABSTRACT
Chemosensors comprise molecular-scale structures that recognize and signal the presence of analytes [1-6]. Most chemosensor designs are based on a “3R scheme”—recognize, relay, and report. As shown in Fig. 1, a noncovalent molec ular recognition event at the receptor site is communicated, by physical or chem ical means, to a reporter site, which produces a measurable signal. A rapid equilibrium between the analyte and receptor site affords the chemosensor a real-time response that varies with the concentration of analyte. Sensitivity and selectivity are the two most important parameters of any sensing application. For the chemosensor platforms of the type depicted in Fig. 1, the “lock and key” fit of analyte to the recognition site and the strength of this interaction (described by the association constant) are crucial determinants of the overall sensitivity and selectivity. The sensitivity of the chemosensor is further aug mented by the efficiency of the relay mechanism in communicating the bind ing event to a receptor site and by the ability of the receptor site to produce a signal.