DOI: 10.1002/elan.201400517 Electrochemical Sensor Based on Gold Nanoparticles Stabilized in Poly(Allylamine hydrochloride) for Determination of Vanillin Tânia Regina Silva, [a] Daniela Brondani,* [b] Eduardo Zapp, [a] and Iolanda Cruz Vieira* [a] 1 Introduction Advances in science and technology at the nanoscale have attracted considerable attention in recent years, par- ticularly with respect to the metal nanoparticles (MNPs), due to their unique characteristics, such as high active sur- face area, catalytic activity, controllable size, and optical and electrochemical properties, which make them useful in catalytic reactions and electroanalytical applications [1–4]. However, MNPs are thermodynamically unstable and have a natural tendency to aggregate and grow, lead- ing to a decrease in the surface area per atom and to the loss of interesting size-dependent properties [1, 5–7]. To avoid aggregation, different materials have been used as stabilizing agents, for example, polymers [8–10], ionic liq- uids [11, 12] and surfactants [13, 14]. The use of polymers has been shown to be an interesting alternative in the sta- bilization of MNPs, offering the advantages of compatibil- ity and the enhancement of long-term stability [9, 10]. Nanomaterials, such as graphene [15–17] and MNPs (AuPd alloy NPs [15], AuAg alloy NPs [18] and AgNPs [16]) have been explored as promising materials in the development of electrochemical sensors for the determi- nation of vanillin. The analytical performance of these sensors is notably improved when nanomaterials are used in their construction, due to their high catalytic activity associated with high electrical conductivity. In addition, these materials, especially MNPs, have a high charge transfer capacity, which makes them suitable for achiev- ing higher sensitivity and lower detection limits [1, 3, 5]. Vanillin (4-hydroxy-3-methoxybenzaldehyde) is the major chemical constituent of vanilla. Due to its flavor and aroma, vanillin is of great commercial importance, being widely employed in confectionery, perfumery, bev- erages, and food and pharmaceutical products. In addi- tion, vanillin has antioxidant and antimicrobial properties, making it an interesting molecule for research studies [19–22]. Several analytical methods, such as UV spectro- photometry [23], high-performance liquid chromatogra- phy (HPLC) [24–27], gas chromatography (GC) [28, 29], and capillary electrophoresis (CE) [30, 31], have been em- ployed for the determination of vanillin. However, many of these methods generally involve time consuming steps for the pre-treatment and analysis of the samples, which are associated with high costs. In recent years, electro- chemical sensors have attracted the attention of many re- searchers, since they offer potential advantages for the determination of vanillin, such as simple operation, fast response, high sensitivity and low cost [15–18]. In this study, gold nanoparticles stabilized in poly(allyl- amine hydrochloride) (AuNP-PAH) were synthesized, characterized and successfully applied in the development of a new sensor for the determination of vanillin. Various characterization studies were performed and the influ- ence of different experimental conditions was investigat- ed, aiming to obtain the best performance of the pro- posed sensor. The optimized method was then applied to determine vanillin in different commercial samples (vanil- la sugar, biscuit, ice cream and vanilla essence) by square-wave voltammetry (SWV). [a] T. R. Silva, E. Zapp, I. Cruz Vieira Department of Chemistry, Federal University of Santa Catarina 88040-900, Florianópolis, SC, Brazil Phone: + 55 48 3721 6844; Fax: + 55 48 3721 6850 *e-mail: iolanda.vieira@ufsc.br [b] D. Brondani Federal University of Santa Catarina 89065-300, Blumenau, SC, Brazil *e-mail: danielabrondani@hotmail.com Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/elan.201400517. Abstract : Gold nanoparticles stabilized in poly(allylamine hydrochloride) (AuNP-PAH) were synthesized, character- ized and applied in the development of a new sensor for the determination of vanillin by square-wave voltamme- try. Under optimized conditions, the calibration curve showed a linear range for vanillin of 0.90 to 15.0 mmol L 1 , with a limit of detection of 55 nmol L 1 . The sensor demonstrated acceptable selectivity and stabil- ity, as well as good intra-day and inter-day repeatability and electrode-to-electrode repeatability (with relative standard deviations of 3.5, 4.5 and 3.9 %, respectively). The sensor was successfully applied in the determination of vanillin in different commercial samples. Keywords: Electrochemical sensor · Vanillin · Gold nanoparticles · Poly(allylamine hydrochloride) www.electroanalysis.wiley-vch.de  2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2015, 27, 465 – 472 465 Full Paper