Synthesis of a Poly-l-Lysine/Black Phosphorus Hybrid for Biosensors

A simple, noncovalent modification strategy was proposed to synthesize poly-l-lysine-black phosphorus (pLL-BP) hybrid. BP nanoflakes were prepared with a water-phase exfoliation method. pLL can adhere to the surface of BP via hydrophobic interaction between butyl chains of pLL and the BP surface as well as the electrostatic interaction between the protonated amino groups on pLL and the negative charge on deprotonated P_xO_y groups remaining on BP. The as-synthesized pLL-BP hybrid turns out to be an ideal matrix for hemoglobin immobilization and direct electron transfer. Good conductivity and biocompatibility of BP maintain the native structure and the bioactivity of hemoglobin (Hb), facilitating the direct electron transfer between the electroactive center of Hb and electrode. The rate constant ( k_ET) for direct electron transfer of Hb@pLL-BP is calculated to be 11.24 s^-1. The constructed Hb-pLL-BP based enzymatic electrochemical biosensor displays excellent catalytic activity toward the reduction of oxygen and hydrogen peroxide. The electrochemical response toward H₂O₂ exhibits a linear dependence on hydrogen peroxide concentration ranging between 10 μM and 700 μM. The results demonstrate that the pLL-BP hybrid can act as a biocompatible building block for the construction of novel biofuel cells, bioelectronics, and biosensors.