A mechanochemically synthesized porous organic polymer derived CQD/chitosan-graphene composite film electrode for electrochemiluminescence determination of dopamine

Abstract

Herein, we explore a new carbon source for preparation of carbon quantum dots (CQDs) with controllable composition using a porous organic polymer (POP) derived porous carbon via a nitric acid oxidation method. The POP used for the preparation of CQDs was synthesized by mechanochemical Friedel-Crafts alkylation under solvent free conditions. Using the as-prepared CQDs, we develop a simple and effective electrochemiluminescence (ECL) detection method for dopamine (DA) using a CQD/chitosan-graphene composite modified glassy carbon electrode (GCE). Both the electrochemical and ECL behaviors were studied in detail with ammonium persulfate as a coreactant. The complementary structure and synergistic function of the composite give the ECL sensor special properties. Apart from the high stability, it also presents good repeatability and high sensitivity to DA with a wide linear range from 0.06 to 1.6 μM. And a satisfactory detection limit of 0.028 μM (S/N = 3) was achieved for the prepared sensor. Furthermore, the ECL also shows high selectivity toward DA with an excellent interference resistance ability at a high concentration ratio of 100 (C _interference : C _DA = 100). In addition, the ECL sensor was successfully applied for effective detection and quantitative analysis of the actual dopamine in human body fluids for disease diagnosis and pathological studies.

Fig. 1. The typical route for the preparation of TPE-HCP and corresponding porous carbon (TPE-800) together with the synthesis of CQDs. (Red atom is oxygen and the grey is carbon).

Fig. 2. SEM and TEM of prepared samples: (a) SEM of TPE-HCP; (b) SEM of TPE-800; (c) high-resolution TEM of TPE-HCP; (d) high-resolution TEM of TPE-800; (e) TEM of single CQDs; (f) SEM of chitosan–graphene composite film; (g) SEM of CQDs/chitosan–graphene composite film; (h) EDS of a single CQD obtained form the high resolution TEM.

Fig. 3. Electrochemical impedance spectroscopy of bare or modified electrode: (a) EIS of bare glassy carbon electrode; (b) EIS of chitosan modified electrode; (c) EIS of chitosan–graphene modified electrode; (d) EIS of carbon quantum dots/chitosan–graphene modified electrode.

Fig. 4. Electrochemiluminescence and cyclic voltammetry behaviors of CQDs/chitosan–graphene composite modified electrode in 0.1 M PBS.

Fig. 5. ECL behaviors of bare or modified electrode: (a) ECL behavior of bare electrode, (b) ECL behavior of chitosan–graphene modified electrode; (c) ECL behavior of CQDs/chitosan–graphene modified electrode.

Fig. 6. Effect of dopamine concentration on ECL intensity of CQDs/CG composite electrode in 0.1 M PBS containing 0.1 M (NH₄)₂S₂O₈ and 0.1 M KCl and (a) 0.5, (b) 0.9, (c) 1.1 and (d) 1.2 μM dopamine at 50 mV s⁻¹. Inset: (A) calibration curve of dopamine detection; (B) ECL intensity change with the injection of dopamine.

Fig. 7. Interference study of the CQDs/chitosan–graphene composite modified electrode towards glucose, Na⁺, K⁺, ascorbic acid (AA) and uric acid (UA) in 0.1 M PBS containing 0.5 μM dopamine.

Fig. 8. The reproducibility of CQDs/chitosan–graphene composite modified electrode under continuous scanning for 8 circles in 0.1 M PBS containing 0.5 μM dopamine and 0.1 M KCl.