Highly Sensitive Amperometric Detection of Hydrogen Peroxide in Saliva Based on N-Doped Graphene Nanoribbons and MnO2 Modified Carbon Paste Electrodes

Abstract

Four different graphene-based nanomaterials (htGO, N-htGO, htGONR, and N-htGONR) were synthesized, characterized, and used as a modifier of carbon paste electrode (CPE) in order to produce a reliable, precise, and highly sensitive non-enzymatic amperometric hydrogen peroxide sensor for complex matrices. CPE, with their robustness, reliability, and ease of modification, present a convenient starting point for the development of new sensors. Modification of CPE was optimized by systematically changing the type and concentration of materials in the modifier and studying the prepared electrode surface by cyclic voltammetry. N-htGONR in combination with manganese dioxide (1:1 ratio) proved to be the most appropriate material for detection of hydrogen peroxide in pharmaceutical and saliva matrices. The developed sensor exhibited a wide linear range (1.0-300 µM) and an excellent limit of detection (0.08 µM) and reproducibility, as well as high sensitivity and stability. The sensor was successfully applied to real sample analysis, where the recovery values for a commercially obtained pharmaceutical product were between 94.3% and 98.0%. Saliva samples of a user of the pharmaceutical product were also successfully analyzed.

Keywords: amperometry; electrochemical sensor; graphene; graphene nanoribbons; hydrogen peroxide.

Figure 1

SEM images of (a) htGO (KS6L), (b) N-doped htGO (KS6L), (c) htGONR (M-grade), and (d) N-doped htGONR (M-grade) materials.

Figure 2

Cyclic voltammograms for measurements with bare CPE, CPE/htGO/MnO₂/Nafion, CPE/N-htGO/MnO₂/Nafion, CPE/htGONR/MnO₂/Nafion, and CPE/N-htGONR/MnO₂/Nafion in 0.1 M PB solution (pH 7.4) containing 5 mM [Fe(CN)₆]^3–/4–.

Figure 3

Cyclic voltammograms (a) and Nyquist plots (b) for measurements with bare CPE, CPE/Nafion, CPE/N-htGONR, CPE/MnO₂, and CPE/N-htGONR/MnO₂/Nafion in 0.1 M PB solution (pH 7.4) containing 5 mM [Fe(CN)₆]^3–/4–.

Figure 4

(a) Amperogram and (b) calibration curve obtained by adding five times 1 µM, five times 5 µM, seven times 10 µM and ten times 20 µM aliquots of H₂O₂ standard solution (in 0.1 M PB with pH 7.4). Operating potential was 0.65 V. The insert of Figure 4 (b) shows five additions of 1 µM aliquots, used to calculate LOD.

Figure 5

(a) Average current change for 5 µM H₂O₂ additions for each of the prepared electrodes in reproducibility study. (b) Percentage of the sensor’s retained initial response after 0–15 days in durability study.