Electrochemical recognition of nitrophenol isomers by assembly of pillar[5]arenes mutifilms

The rational design of electrochemical methods for isomer recognition is a focus of research in the molecular recognition and separation fields. In this work, a novel, rapid, and convenient electrochemical approach for recognition of nitrophenol isomers was constructed based on the alternating layer-by-layer (LbL) assembly of water-soluble cationic and anionic pillar [5]arene on a carboxylic graphene (C-Gra) modified glass carbon electrode. The electrochemical recognition of nitrophenol isomers was investigated by differential pulse voltammetry (DPV). The electrochemical results reveal that both the peak currents of m -nitrophenol ( m -NP) and p -nitrophenol ( p -NP) increased with the increasing of the layer number of the assembled pillar [5]arene, whereas the peak current of o -nitrophenol ( o -NP) decreased with the increased layers, which demonstrated an efficient route for discriminating the nitrophenol isomers. The molecular recognition mechanism was studied by 1 H NMR spectra, which indicated that the m -NP and p -NP can be included in the cavity of the pillar [5]arene host. However, the o -NP could not enter into the host of pillar [5]arene, which was ascribed to the formation of intramolecular hydrogen bond of o -NP. The LbL assembly modified GCE was used for detecting p -NP and m -NP. A low detection limit of 0.33 μM (S/N = 3) and a linear response range of 1–90 μM for p -NP were obtained by using this method. And the detection limit of 0.16 μM (S/N = 3) and a linear response range of 0.5–70 μM for m -NP were obtained. This method of LbL assembly modified GCE has potential application in molecular recognition and separation.