Bis(Salicylidene)-1,3-Propanediamine (Ni-Salpn)
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Electrochimica Acta 178 (2015) 80–91 Contents lists available at ScienceDirect Electrochimica Acta j ournal homepage: www.elsevier.com/locate/electacta Nickel-N,N’–bis(salicylidene)-1,3-propanediamine (Ni-Salpn) film-modified electrodes. Influence of electrodeposition conditions and of electrode material on electrochemical behaviour in aqueous solution a,b b c a Cibely S. Martin , Carla Gouveia-Caridade , Frank N. Crespilho , Carlos J.L. Constantino , b,∗ Christopher M.A. Brett a Departamento de Física, Química e Biologia, Faculdade de Ciências e Tecnologia, UNESP Univ Estadual Paulista, Presidente Prudente-SP, Brazil b Department of Chemistry, Faculty of Sciences and Technology, University of Coimbra, 3004-535 Coimbra, Portugal c Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos-SP, Brazil a r t i c l e i n f o a b s t r a c t Article history: Modified electrodes based on films of Schiff base complexes are excellent candidates for sensing appli- Received 11 June 2015 cations. The influence of the electrode material, glassy carbon, platinum, gold or indium tin oxide, Received in revised form 20 July 2015 on the electrodeposition of nickel-N,N’–bis(salicylidene)-1,3-propanediamine (Ni-Salpn) films in 1,2- Accepted 21 July 2015 dichloroethane (DCE) was investigated, and their electrochemical behaviour was evaluated by cyclic Available online 26 July 2015 voltammetry and electrochemical impedance spectroscopy. The effect of the electrodeposition poten- tial and electrodeposition time on the electrochemical behaviour of Ni-Salpn was examined using glassy Keywords: carbon as substrate. The film growth process was investigated using the electrochemical quartz crys- Ni-Salpn films Electrodeposition tal microbalance and UV-vis absorption spectroscopy and structural differences between the Ni-Salpn complex and the Ni-Salpn film were examined by micro-Raman spectroscopy. The results demonstrate Influence of electrode material EQCM that the electrodeposition mechanism is independent of the electrode material, but that the nature of UV-vis and Raman spectroscopy the substrate material influences the rate of film growth, the electrochemical behaviour and the stability of the film-modified electrodes in aqueous solution. Counteranion insertion during oxidation can break the bonds between the complexes in the stacked Ni-Salpn film structure and cause both mass loss and blockage of the redox metal centre activity, but these effects are small in thin films. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction metallic centres, leading to important applications in electrochem- ical sensors [4,13–15]. The properties of Schiff films depend on the Metal-Schiff complexes with tetradentate N2O2 ligands are electrodeposition conditions, such as structure of the monomer being widely studied as modifiers of electrodes by oxidative [16,17], electrodeposition mode [18,19], potential range, fixed electrodeposition on a variety of conducting surfaces [1–4]. The applied potential or current [19], the nature of the electrode mate- electrodeposition mechanism has been extensively discussed in rial [12], and solvent [5]. Thus, characterization in situ is very the literature by Goldsby et al. [5,6] and Audebert et al. [7–9], in important for understanding the electrochemical behaviour of the which radical-radical coupling was proposed. However, Vilas-Boas film formed and its interactions with the electrode surface as well et al. [10,11] and Dahm et al. [12] concluded that the mecha- as with species present in solution. nism is based on the interactions between the phenol ring and Among the metal-Schiff complexes, the nickel N,N’– the metallic centre with formation of Ni-phenyl stacks. Neverthe- bis(salicylidene)-1,3-propanediamine complex (Ni-Salpn) has less, in both hypotheses, the films are classified as conducting due been used as an antimicrobial agent [20] and as a chelating to the donor sites (metallic centre) and delocalized redox moi- agent in complexometric potentiometric titrations [21]. Ni-Salpn eties (-conjugated system), where electron transfer occurs at the was first electrodeposited by Ardasheva et al. [19] on platinum electrodes. Since then, no reports on electrodeposited Ni-Salpn are found in the literature; only a few studies concerning the ligand ∗ Salpn in other soluble metal complexes have been reported [22,23]. Corresponding author. Tel.: +351 239854470; fax: +351 239827703. To our knowledge, the influence of the electrode substrate material E-mail address: [email protected] (C.M.A. Brett). http://dx.doi.org/10.1016/j.electacta.2015.07.123 0013-4686/© 2015 Elsevier Ltd. All rights reserved. C.S. Martin et al. / Electrochimica Acta 178 (2015) 80–91 81 and electrodeposition parameters with a view to optimisation for Characterization by UV-vis absorption and micro-Raman spec- sensor applications has not been evaluated. troscopy was performed using modified ITO electrodes. UV-vis In this work, the electrodeposition of Ni-Salpn was carried out absorption spectroscopy was carried out using a Varian model in 1,2-dichlorethane (DCE) on four different types of electrode sub- Cary 50 spectrophotometer (Varian, USA), and Raman spectra were strate, i.e. glassy carbon, platinum, gold and indium tin oxide (ITO), obtained with a Renishaw model in-Via micro-Raman spectrograph in order to evaluate the influence of electrode material on the (Renishaw, UK), coupled to a Leica optical microscope. electrodeposition process as well as on the electrochemical and electrical properties of the film-modified electrodes in aqueous 2.3. Electrodeposition of Ni-Salpn films solution. The electrodeposition process and the electrochemical Ni-Salpn films were electrodeposited in both potentiodynamic behaviour of the Ni-Salpn films in aqueous solution were evalu- and potentiostatic modes on the various electrode materials. Poten- ated by cyclic voltammetry, a useful tool to investigate catalytic tiodynamic electrodeposition was carried out in a solution in DCE −1 −1 mechanisms and structure-reactivity relationships [24–26]. In containing 1 mmol L Ni-Salpn complex in 0.1 mol L TBAP by −1 addition, electrochemical impedance spectroscopy (EIS) was potential cycling between 0.0 and +1.4 V vs. Ag/AgCl at 50 mV s . used to investigate the electrical properties and electron transfer Potentiostatic electrodeposition was performed in a solution of the [27–29] resulting from Ni-Salpn/substrate and/or Ni-Salpn/solution same composition at a constant potential of +1.2 vs. Ag/AgCl for interface interactions. Characterization of film growth was carried 900 s. The influence of varying the electrodeposition conditions was out by the electrochemical quartz crystal microbalance (EQCM) assessed using a GC working electrode, where the Ni-Salpn films and UV-vis absorption spectroscopy. Micro-Raman spectroscopy were obtained at different electrodeposition potentials (+1.0, +1.1 was used to evaluate the structural or chemical changes between and +1.2 V vs. Ag/AgCl at 900 s), also varying the electrodeposition the Ni-Salpn complex and Ni-Salpn films. time (300, 600, 900 and 1200 s at +1.2 V vs. Ag/AgCl). All electrochemical measurements of the film-modified elec- trodes were carried out under a nitrogen atmosphere. 2. Experimental Gravimetric measurements during the electrodeposition pro- cess performed at +1.2 V vs. Ag/AgCl for 300 and 900 s, were done 2 2.1. Reagents and solutions using a gold-coated quartz crystal (AuQC–0.205 cm ) as electrode substrate. The Ni-Salpn complex (nickel-N,N’–bis(salicylidene)- UV-vis and micro-Raman characterization was done with an 1,3-propanediamine) was prepared from N,N’–bis(salicylidene)- ITO electrode modified with the Ni-Salpn film electrodeposited at 1,3-propanediamine ligand (Sigma-Aldrich) and nickel acetate a constant potential of +1.2 V vs. Ag/AgCl for a fixed time of 300 or (Sigma-Aldrich), as previously described in the literature [30]. The 900 s. −1 electrodeposition process was carried out using a 1.0 mmol L Ni-Salpn solution prepared in 1,2 -dichloroethane (DCE, Sigma- 2.4. Characterization of Ni-Salpn films in aqueous solution −1 Aldrich) containing 0.1 mol L tetrabutylammonium perchlorate (TBAP, Fluka) as supporting electrolyte. After each modification stage, the electrode modified with Ni- Electrochemical measurements of the modified electrodes were Salpn film was washed thoroughly with Millipore Milli-Q nanopure −1 done in 0.1 mol L potassium chloride (KCl, Fluka) aqueous solu- water and allowed to dry at room temperature for one hour. All tion, prepared with Millipore Milli-Q nanopure water (resistivity ≥ characterizations in aqueous solution were carried out using a −1 18 M cm). 0.1 mol L KCl solution. Cyclic voltammetry measurements were −1 done at 25 mV s in the potential range 0.1 to 0.8 V vs. Ag/AgCl. The potential cycling was also followed gravimetrically in the same 2.2. Instrumentation and methods experimental conditions. In addition, the modified electrodes were −1 characterized by EIS at OCP using 0.1 mol L KCl solution. 2 2 Glassy carbon, (GC - 0.28 cm ), platinum (Pt–0.0628 cm ), gold The influence of anion on electrochemical stability of thinner 2 2 (Au–0.00785 cm ) and indium tin oxide (ITO ∼ 1.0 cm ), were used film in aqueous solution was studied using various supporting elec- −1 + as working electrodes. All electrochemical experiments were per- trolytes of concentration 0.1 mol L with the same cation (Na ) and − − − 2− formed in a conventional three-electrode cell, using an Ag/AgCl different anions: Cl , NO3 , ClO4 , SO4 . (sat. KCl) electrode as reference and a platinum wire as counter electrode. 3. Results and Discussion Cyclic voltammetry experiments were carried out using an Ivium CompactStat.e potentiostat (Ivium Technologies, Utrecht, 3.1. Formation and voltammetric behaviour of Ni-Salpn films on Netherlands). Electrochemical impedance spectroscopy (EIS) different electrode materials experiments were carried out at open circuit potential (OCP) using a Solartron 1250 Frequency Response Analyser, coupled to a Ni-Salpn films were obtained by potential cycling in a solution −1 −1 Solartron 1286 Electrochemical Interface (Solartron Analytical, UK) of 1 mmol L Ni-Salpn in 0.1 mol L TBAP/DCE between 0.0 and −1 controlled by Zplot Software.