Electrochimica Acta 83 (2012) 311–320 Contents lists available at SciVerse ScienceDirect Electrochimica Acta jou rn al hom epa ge: www.elsevier.com/locate/electacta One-pot approach to modify nanostructured gold surfaces through in situ dithiocarbamate linkages I. Almeida a , V.C. Ferreira a , M.F. Montemor b,1 , L.M. Abrantes a,1 , A.S. Viana a,∗,1 a Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal b ICEMS, DEQB, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal a r t i c l e i n f o Article history: Received 14 March 2012 Received in revised form 6 August 2012 Accepted 6 August 2012 Available online 13 August 2012 Keywords: In situ dithiocarbamate modification Gold nanoparticles Epinephrine Tryptophan Glucose oxidase a b s t r a c t This work describes a simple methodology to bio-functionalize flat Au(1 1 1) electrodes through the one- step reaction between gold nanoparticles (AuNPs), carbon disulfide and a secondary amine (epinephrine) and an aminoacid (tryptophan). The process relies on the in situ dithiocarbamate formation between carbon disulphide and amine groups and also on the strong linkage between sulfur and gold. The redox behavior of modified gold with epinephrine or tryptophan, prepared from both ethanolic and aqueous solutions confirms their covalent immobilization and reveals a significant increase of their amount on the electrode due to the presence of AuNPs. Electrochemical reductive desorption in basic solution provided qualitative information on the amount of sulfur linked the gold surface and complements the redox studies. The co-immobilization of an enzyme (glucose oxidase, GOx) and gold nanoparticles, using carbon disulfide has been also tested. The presence of GOx on modified Au(1 1 1) electrodes has been confirmed by electrochemical detection of the catalytic oxidation of glucose in the presence of a redox mediator and through the evaluation of H 2 O 2 reduction, formed during the catalytic reaction. XPS analysis, topographic and phase imaging by atomic force microscopy (AFM) further confirmed surface modification by AuNPs and also their functionalization. The successful one-step amine adsorption, in the presence of AuNPs, from aqueous solutions reveals the potential of this method in the construction of nanostructured biosensing interfaces. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Gold nanoparticles have been extensively and successfully used to build tridimensional biosensing interfaces with improved biorecognition sensitivity [1–3]. The large surface/volume ratio allied to the unique optical/electronic properties of nanoparti- cles is the motors for the increased research in this field. Due to these characteristics AuNPs have a strong adsorption capability and high catalytic efficiencies, and are used as electron transfer mediators to amplify the rate of electron transfer between enzymes and electrodes in biosensors [4–9]. Commonly, the preparation of nanostructured electrodes for catalysis or biosensor applications comprehends several steps, namely (i) gold surface modification with thiols or dithiols derivatives [10]; (ii) incubation with AuNPs; (iii) reaction with a second sulfur derivative containing a suitable terminal group to establish a covalent bond with the catalyst or biomolecule [11,12]; and (iv) one more intermediate activation ∗ Corresponding author. Tel.: +351 21750000; fax: +351 217500088. E-mail address: anaviana@fc.ul.pt (A.S. Viana). 1 ISE member. step with for example EDC/NHS is also required for covalent binding [13]. Recently, the authors have reported [14] that a simple one-pot methodology in the presence of CS 2 could be used for the direct immobilization of glucose oxidase on flat Au(1 1 1) surfaces, with preservation of its biological activity. These results were comple- mented and supported by the efficient one-step immobilization of either a primary (dopamine) or a secondary (epinephrine) amine, and also an aminoacid (tryptophan). Several studies have demon- strated that in situ formation of a dithiocarbamate through the prompt reaction between carbon disulfide and amines (mainly secondary) [15–18] could be useful for the formation of stable self- assembled monolayers with similar properties of those of thiol derivatives on gold [10]. The main structural feature of dithiocar- bamates monolayers is the electron resonance between nitrogen, carbon and sulfur [19,20], which is claimed to be responsible for a strong interaction with the gold substrate, due to an appropriate overlapping of metal and adsorbate molecular orbitals. In addition, it was also demonstrated that in situ dithiocarbamates could be also formed on colloidal gold [15,21,22] and electrodeposited gold nanoparticles [23]. The novelty of the work described here regarding previous studies with thiolated SAMs, or with in situ dithiocarbamates on 0013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2012.08.021