Catalytic Chemosensing Assay for Selective Detection of Methyl Parathion Organophosphate Pesticide.

Herein, a catalytic chemosensing assay (CCA), based on a bimetallic complex, [RuII (bpy)2 (CN)2 ]2 (CuI I)2 (bpy=2,2'-bipyridine), is described. This complex integrates a task-specific catalyst (CuI -catalyst) and a signaling unit ([RuII (bpy)2 (CN)2 ]) to specifically hydrolyze methyl parathion, a highly toxic organophosphate (OP) pesticide. The bimetallic complex catalyzed the hydrolysis of the phosphate ester to generate o,o-dimethyl thiophosphate (DTP) anion and 4-nitrophenolate. Intrinsically, 4-nitrophenolate absorbed UV/Vis light at λmax =400 nm, creating the first level of the chemosensing signal. DTP interacted with the original complex to displace the chromophore, [RuII (bpy)2 (CN)2 ], which was monitored by spectrofluorometry; this was classified as the second level of chemosensing signal. By integrating both spectroscopic and spectrofluorometric signals with a simple AND logic gate, only methyl parathion was able to provide a positive response. Other aromatic and aliphatic OP pesticides (diazinon, fenthion, meviphos, terbufos, and phosalone) and 4-nitrophenyl acetate provided negative responses. Furthermore, owing to the metal-catalyzed hydrolysis of methyl parathion, the CCA system led to the detoxification of the pesticide. The CCA system also demonstrated its catalytic chemosensing properties in the detection of methyl parathion in real samples, including tap water, river water, and underground water.