Electrochemical sensing platform with gold nanoparticles capped by PDDA for benzyl alcohol determination

Abstract

An electrochemical sensor has been developed, by modifying screen-printed carbon devices (SPCE) with photochemically synthesized gold nanoparticles (AuNP), to determine benzyl alcohol, a preservative widely used in the cosmetic industry. To obtain the AuNP with the best properties for electrochemical sensing applications, the photochemical synthesis was optimized using chemometric tools. A response surface methodology based on central composite design was used to optimize the synthesis conditions, as irradiation time, and the concentrations of metal precursor and the capping/reducing agent (poly(diallyldimethylammonium) chloride, PDDA). The anodic current of benzyl alcohol on SPCE modified with the AuNP was used as response of the system. The best electrochemical responses were obtained using the AuNP generated by irradiating for 18 min a 7.20 [Formula: see text] 10^-4 mol L^-1 AuCl₄^--1.7% PDDA solution. The AuNP were characterized by transmission electron microscopy, cyclic voltammetry and dynamic light scattering. The nanocomposite-based sensor formed by the optimal AuNP (AuNP@PDDA/SPCE) was used to determine benzyl alcohol by linear sweep voltammetry in 0.10 mol L^-1 KOH. The anodic current at + 0.017 ± 0.003 V (vs. AgCl) was used as analytical signal. Detection limit obtained under these conditions was 2.8 µg mL^-1. The AuNP@PDDA/SPCE was applied to determine benzyl alcohol in cosmetic samples.

Keywords: Benzyl alcohol; Central composite design; Electrochemical sensor; Gold nanoparticles; Linear sweep voltammetry; Response surface methodology.

Fig. 1

A Absorption spectra of a 5.00 $\times$ 10⁻⁴ mol L⁻¹ AuCl₄⁻ in 0.75% PDDA solution under different conditions:  non irradiated and at room temperature;  heated at 86 °C in the darkness; after irradiation for 1 min at  86 °C and  32 °C. B Absorption spectra of a 5.00 $\times$ 10⁻⁴ mol L⁻¹ AuCl₄⁻ aqueous solution  before and  after 15 min of irradiation and spectra of a 5.00 $\times$ 10⁻⁴ mol L⁻¹ AuCl₄⁻ 0.75% PDDA solution  before and  after 15 min of irradiation

Fig. 2

Characterization of the AuNP@PDDA suspension: (A) TEM image. (B) Size distribution from TEM image and gaussian fit (n = 40, in a surface area of 0.24 µm²). (C) Size distribution obtained from DLS measurements. (D) Cyclic voltammograms obtained in the AuNP@PDDA-based sensor in 0.50 mol L⁻¹ H₂SO₄ at 0.100 V s⁻¹

Fig. 3

Linear sweep voltammograms of a 20.0 µg mL⁻¹ benzyl alcohol in 0.10 mol L⁻¹ KOH solution on SPCE (―), PDDA/SPCE  (overlapped signals) and AuNP@PDDA/SPCE  . Electrochemical response of AuNP@PDDA/SPCE in 0.10 mol L⁻¹ KOH . Scan rate: 0.100 V s⁻¹

Fig. 4

(A) Linear sweep voltammograms and (B) calibration plot (n = 3) of benzyl alcohol on AuNP@PDDA/SPCE. Supporting electrolyte: 0.10 mol L⁻¹ KOH. Scan rate: 0.100 V s⁻¹