We report a turn-on sensor framework with enhanced vapor sensitivity by increasing the sensor's response dynamic range via rational design of the sensor formulation. Using a fluorescent dye as the reporter, our approach begins by reducing sensor background fluorescence through the use of selected quenchers. Analyte interaction induces the onset of emission by interrupting the quenching interaction, thereby turning on the sensor. We demonstrate over an order of magnitude increase in vapor sensitivity for dimethyl methylphosphonate (a Sarin simulant) detection using a sensor containing inorganic oxides as a quencher for Nile Red dye. This approach was also used to develop a new sensor with improved sensitivity for methyl benzoate (a hydrolysis byproduct of cocaine, used to train drug-sniffing dogs). By generalization, additional candidate quenchers for Nile Red were identified based on Lewis acid/base interactions. This framework can be applied in parallel with other amplification strategies including mass transport incentive, one-analyte-to-multiple-reporter schemes or signal lasing to further increase sensor response amplitude.
