The present invention provides methods and compositions for detecting, identifying and measuring the abundance of chemical nerve agents. Methods and compositions of the present invention are capable of providing selective detection of phosphorous based nerve agents, such as nerve agents that are esters of methyl phosphonic acid derivatives incorporating a moderately good leaving group at the phosphorus. Selectivity in the present invention is provided by a sensor composition having an alpha (α) effect nucleophile group that undergoes specific nucleophilic substitution and rearrangement reactions with phosphorus based nerve agents having a tetrahederal phosphorous bound to oxygen. The present invention includes embodiments employing a sensor composition further comprising a reporter group covalently linked to the alpha effect nucleophile group allowing rapid optical readout of nerve agent detection events, including direct visual readout and optical readout via spectroscopic analysis.