The Electrochemical Behavior of Gold Nanoparticle‐Tantalum(V) Phthalocyanine Composites: Applications Towards the Electroanalysis of Bisphenol A

Abstract

The formation of gold nanoparticle (AuNP) composites with tantalum phthalocyanines (TaPc) complexes {1a and 1b (Figure 1)} is reported. The TaPc‐AuNPs conjugates were characterised by atomic force microscopy (AFM) and transmission electron microscopy. The AFM analyses show that conjugates of TaPc with AuNPs are more aggregated when compared to AuNPs alone. The conjugates and TaPc complexes were immobilized on a gold electrode by drop and dry method and these were characterized by electrochemical impedance spectroscopy. The charge transfer behaviour of AuNPs was enhanced in the presence of TaPc complexes. All the modified electrodes showed electrocatalytic oxidation of bisphenol A. The limits of detection for complexes 1a and 1b were 4.78×10−10 and 2.76×10−10 mol L−1, respectively.

Comparative behavior of conjugates of tantalum phthalocyanines with gold nanoparticles or single walled carbon nanotubes towards bisphenol A electrocatalysis

“…Gracia et al [33] have reported the use of adsorbed AuNPs onto Au disk electrode where they observed no gold oxidation for AuNPs below 0.6 V on indium tin oxide (ITO) coated glass. Similarly, AuNPs do not show any gold oxidation on Au disk electrodes [9,34,35] below 0.6 V. The oxidation peak of AuNPs has been reported at 1.28 V (vs saturated calomel electrode) and the reduction peak at 0.81 V [33]. We reported the AuNP oxidation at 0.99 V in pH 7.4 buffer and the subsequent reduction at 0.36 V vs Ag|AgCl [9].…”

“…pH 12 phosphate buffer solutions were prepared from KH 2 PO 4 and Na 2 HPO 4 , and NaOH was used to adjust the pH. Gold nanoparticles (and AuNP-MPc conjugates) were synthesised as described recently [9]. The synthesis of 4 ( Fig.…”

“…To illustrate this, conjugates of AuNPs with MPcs will be employed for the electrocatalytic oxidation of bisphenol A (BPA) in this work. Alkylthio TaPc conjugates with AuNPs have been characterized [9]. In this work, tantalum phthalocyanine complex (3) substituted at the peripheral positions with an aryl substituent (2-mercaptopyridine, Scheme 1) will be conjugated to AuNPs, and its behavior compared with that of complex 4 substituted with alkyl substituents.…”

“…The aim is to compare AuNPs and SWCNTs towards reducing electrode passivation during the detection of BPA. The central metal Ta was chosen because of the possibility of multiple oxidation states, and the fact that electrocatalytic behavior of TaPc has been relatively unexplored [9]. This is due to the difficulty in the synthesis of these complexes.…”

“…However, the major drawback with the oxidation of phenolic type compounds on bare electrodes is the inevitable formation of dimers which passivate the electrode surface resulting in low oxidation currents [1]. We have recently reported [9] that TaPc derivatives and their conjugates with AuNPs showed catalytic activity towards BPA. We also reported on the use of nickel tetraamino phthalocyanine [Ni(II)-TAPc] for BPA detection, which showed extensive passivation of the electrode [22].…”