Electrochemical sensing platform for the detection of methyl parathion applying highly biocompatible non-covalent functionalized phosphonium-based ionic liquid@MWCNTs hybrid to immobilize hemoglobin

A hydrophobic carboxyl functionalized phosphonium-based ionic liquid (IL) ((5-carboxypentyl) triphenylphosphonium bis (trifluoromethyl)sulfonyl) amide, TPP-HA[TFSI]) was synthesized through a simple hydrothermal approach. Based on the π-π and cation-π interactions with multi-wall carbon nanotubes (MWCNTs), a TPP-HA[TFSI]@MWCNTs hybrid was prepared to immobilize hemoglobin (Hb) to fabricate a simple and effective electrochemical sensing platform for the detection of methyl parathion (MP) in vegetables. Spectroscopic and electrochemical results show that TPP-HA[TFSI]@MWCNTs substrate synergistically provided a good biocompatible microenvironment for Hb, and the hydrophobicity of TPP-HA[TFSI] and the π-π interaction and hydrogen bonding between TPP-HA[TFSI]@MWCNTs, Hb and nafion (NF) were conducive to maintain the stability and integrity of the modified electrode interface. The TPP-HA[TFSI]@MWCNTs with large surface area and high conductivity promoted the exposure of the electroactive center of Hb and the direct electron transfer between Hb and the electrode, which effectively amplified the electrochemical signal and improved the sensitivity of MP detection. The constructed electrochemical sensing platform had a wider linear range (2-14 ng mL^-1) and a lower detection limit (0.62 ng mL^-1) for MP, and had acceptable repeatability, reproducibility, stability and anti-interference ability. This results indicated that the phosphonium-based ILs functionalized MWCNTs was an effective substrate for the immobilization of biological components, which have broad prospect in the construction of electrochemical sensing interfaces.