Electrosynthesized Polystyrene Sulphonate-Capped Zinc Oxide Nanoparticles as Electrode Modifiers for Sensing Devices

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Electrosynthesized Polystyrene Sulphonate-Capped Zinc Oxide Nanoparticles as Electrode Modifiers for Sensing Devices Maria C. Sportelli1, Diana Hötger2, Rosaria A. Picca1, Kyriaki Manoli1, Christine Kranz2, Boris Mizaikoff2, Luisa Torsi1, and Nicola Cioffi1 1 Dipartimento di Chimica, Università degli Studi di Bari “Aldo Moro”, Via E. Orabona 4, 70126 Bari, Italy. 2 Institut für Analytische und Bioanalytische Chemie, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany. ABSTRACT ZnO nanoparticles were prepared by a green electrochemical synthesis method applying low current densities followed by a thermal treatment. Sodium polystyrene sulphonate (PSS) was used as stabilizer in the electrolytic aqueous medium due to its biocompatibility and stability. The as-prepared nanocolloids were then annealed to improve their stability, and then converted via hydroxide species into stoichiometric oxide. Different calcination temperatures were studied. ZnO@PSS nanomaterials were deposited onto SiO2/Si substrates, in part in combination with an organic semiconductor layer to evaluate their influence on organic field effect transistors (OFETs). All nanomaterials and composite layers were characterized by morphological and spectroscopic techniques. Promising results regarding the use of ZnO@PSS in OFETs could be demonstrated. INTRODUCTION Zinc oxide nanoparticles (ZnO-NPs) may offer excellent prospects for designing a new generation of low-cost, flexible, multi-functional bioelectronic devices. The conjugation of the high surface area-to-volume ratio of ZnO-NPs with their affinity for biomolecules, electron communication ability, and chemical stability already rendered them a particularly promising material for biosensing applications [1,2]. Typical approaches for the synthesis of ZnO-NPs involve sol-gel [3] and hydrothermal methods [4], while electrochemical routes are less explored, although they may offer several advantages for fine-tuning of particle morphology, size, surface chemistry, etc. [5]. We have recently developed an electrochemical preparation routing of ZnO-NPs from aqueous media in the presence of several stabilizers including sodium polystyrene sulphonate (PSS). The thermal treatment of the nanocolloid at t ≥ 300°C allows the complete conversion into nanostructures having a ZnO stoichiometry. PSS was preferred to other anionic capping agents considering its widespread use in organic field effect transistors (OFETs) [6] and its biocompatibility. Moreover, its sulphonated moiety can be used for further functionalizing the ZnO@PSS nanophases via ionic interactions with cationic (bio)molecules. In this work, the as-prepared nanostructures were employed as electrode modifiers in OFETs showing improved electrical performances. A systematic analytical characterization by transmission electron microscopy (TEM), UV-Vis, IR, and X-ray photoelectron (XPS) spectroscopies was performed to investigate the physicochemical properties of ZnO@PSS NPs and the resulting composite layers.

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EXPERIMENT Materials Zn sheets (p