PEDOT: PSS/AuNPs-Based Composite as Voltammetric Sensor for the Detection of Pirimicarb

Abstract

An electrochemical sensor for the pesticide Pirimicarb (PMC) has been developed. A screen-printed electrode (SPCE) was used and modified with the conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) and gold nanoparticles (AuNPs) to enhance electrochemical proprieties. Electrode characterizations were performed using scattering electron microscopy (SEM) and cyclic voltammetry (CV). With the SPCE/PEDOT:PSS/AuNPs modified electrode, a new peak at 1.0 V appeared in the presence of PMC related to the PMC oxidation. To elucidate the mechanism of PMC oxidation, Gas Chromatography-Mass Spectrometry (GC-MS), where two major peaks were identified, evidencing that the device can both detect and degrade PMC by an electro-oxidation process. Exploring this peak signal, it was possible the sensor development, performing detection from 93.81-750 µmol L^-1, limits of quantification (LOQ) and detection (LOD) of 93.91 µmol L^-1 and 28.34 µmol L^-1, respectively. Thus, it was possible to study and optimization of PMC degradation, moreover, to perform detection at low concentrations and with good selectivity against different interferents using a low-cost printed electrode based on graphite modified with conductive polymer and AuNPs.

Keywords: PEDOT:PSS; composites; conductive polymers; electrochemical sensor; modified electrode; pirimicarb.

Figure 1

Chemical structure of pirimicarb.

Figure 2

Representative secondary electron SEM images were obtained from (a) PEDOT:PSS and (b) PEDOT:PSS/AuNPs modified electrode. Magnification = 40 kx, voltage = 15 kV. (c) EDS spectra of PEDOT:PSS/AuNPs modified electrode.

Figure 3

(a) CV at 20 mV s⁻¹ of PEDOT:PSS and PEDOT:PSS/AuNPs SPCE modified electrodes in acetate buffer. CVs of (b) PEDOT:PSS and (c) PEDOT:PSS/AuNPs in the absence and the presence of 500 µmol L⁻¹ PMC at 20 mV s⁻¹. Electrolyte = Acetate buffer pH 5.0.

Figure 4

(a) Chromatogram of the PMC solution after the electrochemical oxidation by PEDOT:PSS/AuNPs modified electrode. Mass spectra of (b) pirimicarb and (c) degradation product carbamic acid, dimethyl-, 2-(formylmethylamino)-5,6-dimethyl-4-pyrimidinyl ester.

Figure 5

LSV response of (a) PEDOT:PSS and (b) PEDOT:PSS/AuNPs in the presence of different PMC concentrations in acetate buffer pH 5. Scan rate = 20 mV s⁻¹. The (c) analytical curves for PMC detection in triplicate.