Voltammetric Sensor Based on Molecularly Imprinted Chitosan-Carbon Nanotubes Decorated with Gold Nanoparticles Nanocomposite Deposited on Boron-Doped Diamond Electrodes for Catechol Detection

Abstract

Phenolic compounds such as catechol are present in a wide variety of foods and beverages; they are of great importance due to their antioxidant properties. This research presents the development of a sensitive and biocompatible molecular imprinted sensor for the electrochemical detection of catechol, based on natural biopolymer-electroactive nanocomposites. Gold nanoparticle (AuNP)-decorated multiwalled carbon nanotubes (MWCNT) have been encapsulated in a polymeric chitosan (CS) matrix. This chitosan nanocomposite has been used to develop a molecular imprinted polymers (MIP) in the presence of catechol on a boron-doped diamond (BDD) electrode. The structure of the decorated MWCNT has been studied by TEM, whereas the characterization of the sensor surface has been imaged by AFM, demonstrating the satisfactory adsorption of the film and the adequate coverage of the decorated carbon nanotubes on the electrode surface. The electrochemical response of the sensor has been analyzed by cyclic voltammetry (CV) where excellent reproducibility and repeatability to catechol detection in the range of 0 to 1 mM has been found, with a detection limit of 3.7 × 10^-5 M. Finally, the developed sensor was used to detect catechol in a real wine sample.

Keywords: BDD electrode; catechol; chitosan; electrochemical sensor; molecular imprinted polymer.

Figure 1

TEM images of multi-walled CNT/AuNP composite in (a) 0.5 µm and (b) 50 nm scale.

Figure 2

AFM image of the molecularly imprinted CS-MWCNT/AuNP nanocomposite modified BDD electrode. White semicircles show examples of the semicircular globular structures found.

Figure 3

Voltammetric responses of the MIP CS-MWCNT/AuNP nanocomposite modified BDD electrode in 10⁻³ M catechol in 0.1 M, pH 7.4 PBS solution with increased concentrations of MWCNT/AuNP composite, 10% in black, 20% in red, 40% in blue and 50% in green.

Figure 4

Voltammetric responses of (a) MIP CS-MWCNT/AuNP nanocomposite/BDD sensor in black, NIP CS-MWCNT/AuNP nanocomposite/BDD sensor in red and bare electrode in blue, in 10⁻⁴ M catechol in 0.1 M, pH 7.4 PBS solution and (b) MIP CS-MWCNT/AuNP nanocomposite/BDD to increased concentration of catechol (0.075, 0.1, 0.25, 0.5, 0.75, and 1 mM) in 0.1 M, pH 7.4 PBS solution.

Figure 5

Calibration curves of MIP CS-MWCNT/AuNP nanocomposite/BDD sensor in black and NIP CS-MWCNT/AuNP nanocomposite/BDD sensor in red in 0.1 M, pH 7.4 PBS solution for increased concentration of catechol (0.075, 0.1, 0.25, 0.5, 0.75, and 1 mM) for (a) three sensors prepared under the same conditions and (b) the same sensor measured three times.

Figure 6

(a) Percentage of CV anodic peak value offered by MIP CS-MWCNT/AuNP nanocomposite/BDD sensor in black and NIP CS-MWCNT/AuNP nanocomposite/BDD sensor in red for the detection of catechol 10⁻³ M containing different interfering phenols in 10⁻³ M prepared in 0.1 M, pH 7.4 PBS solution and (b) Voltammetric responses of MIP CS-MWCNT/AuNP nanocomposite/BDD sensor for the detection of catechol 10⁻³ M containing catechol (black), 4-tert-butylcatechol (red), 4-aminothiophenol (dark blue), bisphenol A (green), 2-nitrophenol(purple), and 4-nitrophenol (aqua blue) 10⁻³ M prepared in 0.1M, pH 7.4 PBS solution.

Figure 7

(a) Voltammetric responses of MIP CS-MWCNT/AuNP nanocomposite/BDD sensor in 10% diluted wine solution in 0.1 M, pH 7.4 PBS solution, for increased concentration of catechol (0, 0.075, 0.1, 0.25, 0.5, 0.75, and 1 mM). (b) Calibration curve for standard additions of catechol in a diluted wine sample (10% diluted in 0.1 M, pH 7.4 PBS solution), using the CS-MIP/BDD sensor.