A fast and highly efficient strategy for discrimination and detection of three nitrophenol isomers

Novel catalysts of strongly coupled nickel-cobalt nitrides/carbon nanocage (NiCoN/C nanocages) with good water solubility and low cost are utilized to simultaneously catalytically reduce three nitrophenol isomers (2-NP, 3-NP and 4-NP) into corresponding aminophenol (2-AP, 3-AP and 4-AP) within nearly 5 min at room temperature . It is the first report that only one reagent (dopamine) can achieve fast discrimination of three nitrophenol isomers one by one. The reduced product of 3-NP (3-AP) can selectively form fluorescent substance with dopamine with maximum emission wavelength at 465 nm. The reduced product of 4-NP (4-AP) can selectively react with dopamine to form purple solution with absorption peak at 550 nm. It achieves fluorescent detection of 3-NP from 50 nM to 1.2 μM with the limit detections (LOD) of 17 nM for 3-NP, and colorimetric detection of 4-NP from 5 μM to 200 μM with LOD of 1.7 μM. It also realizes nitrophenol detection in tap water. When 0.30, 0.60, 1.00 μM 3-NP and 10, 50, 100 μM 4-NP are added to water samples, recoveries are 98.8–104.6% for 3-NP and 98.8–101.8% for 4-NP.