Plasma polyacrylic acid and hollow TiO2 spheres modified with rhodamine B for sensitive electrochemical sensing Cu(ii)

Abstract

We report a novel nanocomposite of hollow TiO₂ microspheres and plasma polyacrylic acid (TiO₂@PPAA) modified with rhodamine B (TiO₂@PPAA-RhB). This nanocomposite was further used as an electrochemical sensor for the ultra-sensitive and selective detection of Cu²⁺ in water. A gold electrode was modified with hollow TiO₂ nanospheres, followed by the closely bonded layer of PPAA via plasma polymerization. Subsequently, the carboxyl groups of TiO₂@PPAA nanocomposites were activated to ester groups by N-hydroxysuccinimide/1-ethyl-3-(3-dimethylaminoprolyl) carbodiimide hydrochloride. The resultant activated ester groups reacted with the amino groups on rhodamine to form the amide groups, leading to the modification of TiO₂@PPAA nanocomposites with rhodamine. Considering the synergistic effect of strong electrostatic interaction between the carboxyl groups of PPAA and Cu²⁺, the direct adsorption of Cu²⁺ on the TiO₂ surface, and the coordination chemistry formed between Cu²⁺ and rhodamine, the developed electrochemical biosensor exhibited high sensitivity of Cu²⁺ detection, with a detection limit of 0.404 pM within the range of 0.001–10 nM of Cu²⁺. Therefore, the fabricated electrochemical sensor based on TiO₂@PPAA-RhB can be obtained via plasma polymerization and represents a highly promising tool for use in environmental monitoring.