Background: Carbon-based nanomaterials, especially carbon nitride (C3N4) has attracted tremendous interest in biosensor applications. Meanwhile, the mechanism of redox protein sensing and related electrocatalytic reactions can provide a valid basis for understanding the process of biological redox reaction.

Objective: The aim of this paper is to construct a new electrochemical enzyme sensor to achieve direct electron transfer of myoglobin (Mb) on CILE surface and display electrocatalytic reduction activity to catalyze trichloroacetic acid (TCA) and H2O2.

Methods: The working electrode was fabricated based on ionic liquid modified Carbon Paste Electrode (CILE) and C3N4 nanosheets were modified on the CILE surface, then Mb solution was fixed on C3N4/CILE surface and immobilized by using Nafion film. The as-prepared biosensor displayed satisfactory electrocatalytic ability towards the reduction of TCA and H2O2 in an optimum pH 7.0 buffer solution.

Results: The results indicated that C3N4 modified electrode retained the activity of the enzyme and displayed quasi-reversible redox behavior in an optimum pH 7.0 buffer solution. The electrochemical parameters of the immobilized Mb on the electrode surface were further calculated with the results of the electron transfer number (n) as 1.27, the charge transfer coefficient (α) as 0.53 and the electrontransfer rate constant (ks) as 3.32 s-1, respectively. The Nafion/Mb/C3N4/CILE displayed outstanding electrocatalytic reduction activity to catalyze trichloroacetic acid and H2O2.

Conclusion: The Nafion/Mb/C3N4/CILE displayed outstanding electrocatalytic reduction, which demonstrated the promising applications of C3N4 nanosheet in the field electrochemical biosensing.

背景：碳基纳米材料，尤其是氮化碳（C3N4）在生物传感器应用中引起了巨大兴趣。同时，氧化还原蛋白的感应机理及相关的电催化反应可为理解生物氧化还原反应的过程提供有效的依据。

目的：构建一种新型的电化学酶传感器，以实现肌红蛋白（Mb）在CILE表面上的直接电子转移，并表现出电催化还原活性，以催化三氯乙酸（TCA）和H2O2。

方法：以离子液体修饰的碳糊电极（CILE）为基础制备工作电极，在CILE表面修饰C3N4纳米片，然后将Mb溶液固定在C3N4 / CILE表面，并用Nafion膜固定。所制备的生物传感器在最佳pH 7.0缓冲溶液中显示出令人满意的电催化能力，可降低TCA和H2O2。

结果：结果表明，在最佳pH 7.0缓冲溶液中，C3N4修饰的电极保留了酶的活性，并显示出可逆的氧化还原行为。进一步计算出固定在电极表面的Mb的电化学参数，电子传递数（n）为1.27，电荷传递系数（α）为0.53，电子传递速率常数（ks）为3.32 s-1 ， 分别。Nafion / Mb / C3N4 / CILE具有出色的电催化还原活性，可催化三氯乙酸和H2O2。

结论：Nafion / Mb / C3N4 / CILE具有出色的电催化还原性能，这表明C3N4纳米片在电化学生物传感领域中具有广阔的应用前景。