DOI: 10.1002/elan.201900432 EffectsofHumidity,TemperatureandBismuth ElectrodepositiononElectroanalyticalPerformancesof Nafion-coatedPrintedElectrodesforCd 2 + andPb 2 + Detection Noemi Colozza, [a] Ilaria Cacciotti, [b] Danila Moscone, [a] and Fabiana Arduini* [a] Abstract: The synergistic use of Nafion polymeric mem- brane and in situ electrodeposited bismuth film is a worthwhile strategy to develop electrochemical sensors for the detection of Cd 2 + and Pb 2 + . However, Nafion thin films morphological and conductivity properties have a strong dependence on the environmental conditions, such as relative humidity and temperature, while the bismuth in situ electroplating can affect the repeatability of measurements. With the aim to overcome these draw- backs, the effects of the storage environmental conditions were investigated to improve the morphological stability and electroanalytical performances of Nafion film-based sensor for the detection of Cd 2 + and Pb 2 + . Nafion-coated graphite-based screen-printed electrodes were stored at different humidity and temperature conditions and char- acterised by using square wave anodic stripping voltam- metry, cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. Signifi- cant differences were observed at the varying of humidity conditions, with an enhancement of sensor electrochem- ical performances at lower humidity. Furthermore, differ- ent approaches for bismuth in situ electrodeposition on Nafion-coated screen-printed electrodes were compared by using overlap or removal approach. This study disclosed considerable differences in the electrochemical performances and morphology of the resulting bismuth- sensor, obtaining an enhancement of the working stability for the removal approach. Keywords: heavy metals · lead · cadmium · stripping analysis · in situ electroplated 1Introduction The combined use of Nafion and bismuth for the design of sensitive and sustainable electrochemical sensors for heavy metals detection has gained increasing attention during the last decades. Indeed, the need to replace the mercury-based sensors has boosted the research in the development of more eco-friendly sensors. In literature, a variety of studies have demonstrated the suitability of combining the advantages of electrochemical sensors, such as their cost-effectiveness and their easiness to use, with the properties of Nafion and bismuth, delivering analytical devices which can represent a worthy alterna- tive to reference methods (e.g. inductively coupled plasma mass spectrometry) for heavy metal detection, thanks to competitive detection limits. In details, Nafion is a sulfonated tetrafluoroethylen- based copolymer, which can be used to modify the surface of an electrochemical sensors to improve its mechanical resistance and to provide protection from fouling by organic compounds and surfactants [1–3]. It is known as a benchmark material among the solid polymer electrolytes with proton exchange capacity [4,5], and is typically employed for fuel cells. Although the most robust applications of Nafion involve its use in the form of a free-standing membrane (thickness > 25 μm), the possibil- ity of using thin films (usually with a thickness between 100 nm and 1 μm) is also of great interest, particularly for electrochemical applications. However, it is well known that the Nafion thin films physical properties and polymeric structure are strongly influenced by the environmental conditions [6–9]. In particular, the Nafion proton conductivity is remarkably affected by the environmental conditions to which it is exposed, such as temperature [10] and relative humidity (RH%) [9–13]. These RH%-dependent properties should rely on the peculiar Nafion polymeric structure and its strong tendency for water uptake. Basing on the Cluster- Network model, proposed by Gierke et al. [14], Nafion structure is characterised by a network of water nano- channels which branch out among ionic domains [12,13,15]. The ionic domains are normally deprotonated [a] N. Colozza, D. Moscone, F. Arduini Department of Chemical Science and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy E-mail: fabiana.arduini@uniroma2.it [b] I. Cacciotti Department of Engineering, University of Rome “Niccolò Cusano”, Via Don Carlo Gnocchi 3, 00166, Rome, Italy Supporting information for this article is available on the WWW under https://doi.org/10.1002/elan.201900432 Full Paper www.electroanalysis.wiley-vch.de © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2019, 31, 1 – 14 1 These are not the final page numbers! ��