(Invited) Metal Nanoparticles Modified Nitrogen Containing Carbon Film Electrodes for Chemical Sensing

Abstract

Electrocatalytic performance of metal nanoparticles (NPs) has been studied to apply for electrochemical devices such as fuel cells and electrochemical sensors. We have developed metal NPs embedded carbon film electrodes by co-sputtering of metal and carbon [1]. Various kinds of metals including Pt, Pd, Au, Ni, Cu and their alloys can be fabricated in the carbon film by using unbalanced magnetron (UBM) sputtering and applied for detecting hydrogen peroxide, glucose [1], heavy metals [2,3] and sugar markers [4, 5]. The electrocatalytic activity of metal NPs can be modulated by changing electronegativity of substrate such as carbon electrodes. Here, we proposed Ni NPs electrodeposited on nitrogen containing carbon film electrodes. Method The carbon films were prepared by unbalanced magnetron sputtering equipment and then treated by N2 plasma. The surface of the films were characterized by XPS. Then NiNP was electrodeposited onto both plasma treated and untreated carbon films by changing the deposition potentials. The fabricated electrodes were potential cycled to sufficiently form surface Ni(OH)2 on the surface of NiNPs, then applied for measuring sugar oxidation such as glucose and oligosaccharide in alkaline solutions with different pH. Results and Discussion The nitrogen containing carbon film electrode show unique electrochemical performances including reduction of overpotentials for oxygen reduction and oxidation of some biochemicals such as NADH and L-ascorbic acid [6]. The films also show excellent biocompatibility to suppress the fouling of proteins during electrochemical measurements [7]. When we deposited NiNPs onto the nitrogen containing carbon film, the size of NiNPs became smaller by decreasing potential from -1000 to -1300 mV. Since the size of NiNPs at N2 plasma treated surface is larger than that at pure carbon film, we adjusted the potential to obtain similar NiNPs size on both N2 plasma treated and untreated carbon surfaces. After deposition, both electrodes were potential cycled between 0 and 0.70 V (vs Ag/AgCl) to form surface Ni(OH)2 , which is confirmed by HR-TEM, and HAADF-STEM-EDS images. The redox reaction peaks of Ni(OH)2 oxidation and NiOOH reduction is almost identical when the scan rate is slow (1 mV/s). However, the oxidation and reduction peaks shifted positive and negative directions, respectively at Ni(OH)2 modified untreated carbon film with increasing potential scan rate up to 100 mV/s. In contrast, peak separation increase at Ni(OH)2 modified N2 plasma treated carbon film is greatly suppressed suggesting fast redox reaction similar to at Ni(OH)2. We applied both NiNPs deposited plasma treated and untreated carbon film electrodes for electrocatalytic oxidation of glucose and maltopentaose (G5) in alkaline media. Higher electrocatalytic oxidation currents of glucose was observed at NiNPs on nitrogen containing carbon film compared with those at NiNPs on untreated carbon film particularly in higher glucose concentration region (> 1mM). Moreover, the electrocatalytic current was started to increase sharply at +0.28 V at the Ni@Ni(OH)2-NP/N-C, while that at Ni@Ni(OH)2-NP/C was started to increased gradually at +0.34 V. These results could be due to the slightly formed NiOOH at the low potential region which cannot be detected as current change.And 60 mV potential difference could be interpreted as electrostatic interaction between G5 and electrode surface. In conclusion, the electrocatalytic activity of NiNPs can be enhanced by modifying NiNPs on the N2 plasma treated carbon films, which shows enhanced current and lower onset potential for electrocatalytically oxidation of G5. References [1] T. You, O. Niwa, M. Tomita, S. Hirono,” Characterization of platinum nanoparticle- embedded carbon film electrode and its detection of hydrogen peroxide”, Anal. Chem .,75 (2003) 2080. [2] D. Kato, T. Kamata, D. Kato, H. Yanagisawa, O. Niwa, “Au nanoparticle-embeded carbon films for electrochemical As3+ detection with high sensitivity and stability”, Anal. Chem ., 88 (2016) 2944. [3] S. Shiba, S. Takahashi, T. Kamata, H. Hachiya, D. Kato, O. Niwa, “Selective Au Electrodeposition on Au Nanoparticles Embedded in Carbon Film Electrode for Se(IV) Detection” Sensors and Materials ., 31 (2019) 1135. [4] S. Shiba, D. Kato, T. Kamata, O. Niwa,” Co-sputter deposited Nickel-Copper bimetallic nanoalloy embedded carbon films for electrocatalytic biomarker detection”, Nanoscale , 8 (2016) 12887. [5] S. Shiba, R. Maruyama, T. Kamata, D. Kato, O. Niwa, “Chromatographic determination of sugar probes used for gastrointestinal permeability test by employing nickel-copper nanoalloy embedded in carbon film electrodes”, Electroanalysis , 30 (2018) 1407. [6] T. Kamata, D. Kato, O. Niwa,”Electrochemical performance at sputter-deposited nanocarbon film with different surface nitrogencontaining groups”, Nanoscale, 11 (2019) 10239. [7] S. Ohta, S.Shiba, T. Yajima, T. Kamata, D. Kata, O. Niwa, “Gas-phase Treatment Methods for Chemical Termination of Sputtered Nanocarbon Film Electrodes to Suppress Surface Fouling by Proteins”, J. Photopolym. Sci. Tech., 32 (2019) 523