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In order to deepen the understanding of the role of transition metal oxides in electron transfer at the electrochemical interface, the performance of ZnxNi1-xFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) nanomaterials in electrochemical sensing is studied. Nanomaterials are synthesized by simple autocombustion synthesis procedure. Field-emission scanning electron microscopy characterization shows that the particles have a size between 30 and 70 nm with an average crystallite size between 24 and 35 nm. The bandgap energies of the nanomaterials, as estimated by UV-vis experiments, are in the 2.32-2.56 eV range. The valence band maximum is evaluated using X-ray photoelectron spectroscopy and the position of the conduction band minimum is estimated. The ZnFe2O4 sensor has the best performances: highest rate constant (13.1 & PLUSMN; 2.8 ms(-1)), lowest peak-to-peak separation (386 & PLUSMN; 2 mV), and highest sensitivity (37.75 & PLUSMN; 0.17 & mu;A mM(-1)). Its limit of detection (7.94 & PLUSMN; 0.04 & mu;M) is second best, and its sensitivity is more than twice the sensitivity of the bare sensor (16.7 & PLUSMN; 0.9 & mu;A mM(-1)). Nanomaterials energy bands mapping with the experimental redox potentials is performed to predict the electron transfer at the electrochemical interface, and the importance of surface states/defects is highlighted in the electron transfer mechanism.
Nicola Marzari, Iurii Timrov, Artur Braun, Matteo Cococcioni, Xinyu Zhang, Daniele Passerone, Piyush Agrawal
Marco Grioni, Helmuth Berger, Alberto Crepaldi, Daniela Pacilè