(Invited) Facile Nickel Phosphate Nano/Micro Structure As the High-Performance Electrode for Non-Enzymatic Glucose and pH Sensors

Abstract

The commonly used glass pH probe is sensitive, stable, and lasts for a relatively long period of time but it is not a practical sensor for pH measurements in all environments, particularly in wearable ambulatory settings [1]. Similarly, measuring glucose level from external skin sweat is very difficult in terms of applicability. A wide range of nanostructured metal oxide based (IrO2, Ni(OH)2, CuO, ZnO, etc.)) pH and glucose sensors were proposed [2-5]. In general they have good electrical conductivity, fast responses to changes in pH and can achieve equilibrium with the analyte solution without being dissolved. However, there are issues with these probes depending on the metal and the fabrication technique that are more sensitive to redox reagents and temperature which can be a problem for its long range applications. Furthermore, stability, repeatability and bio-fouling are the prominent issues in these pH electrodes, which are needed to be resolved. And they are non-stoichiometric, which means that consistent fabrication of electrodes may be problematic. Hence, the developments of multi-analyte sensor that can measure both pH and/or glucose with low cost material are being needed in particular for human sweat based sensor fabrication. Thereby, in this work we investigate a nanostructured Ni3(PO4)2·8H2O based non-enzymatic glucose/ pH sensor, which shows an exceptional sensitivity (24.39 mA mM–1cm–2) with a low detection limit of 97 nM (S/N = 3) towards glucose. As a pH sensor, the electrode based on nickel phosphate on nickel foam is capable of detecting human sweat pH ranging from 4 to 7 [6]. This nanoporous three dimensional transition metal phosphate shows excellent electrochemical performance and thus should provide a novel material design philosophy for bifunctional electrocatalysts for glucose and pH sensing. Acknowledgment The authors acknowledge financial support from Science Foundation Ireland under the Technology Innovation and Development Award no. 14/TIDA/2455. This work has received funding from the European Union’s Horizon 2020 research and innovation programme project SmartVista, under grant agreement No. 825114. Reference Jones L, Atkins P, Chemistry: Molecules, Matter, and Change. TPB, 2004.Huang, W.-D.; Cao, H.; Deb, S.; Chiao, M.; Chiao, J.-C. A, Flexible pH Sensor Based on the Iridium Oxide Sensing Film. Sens. Actuators, A 2011, 169, pp. 1−11.Natan, M. J.; Belanger, D.; Carpenter, M. K.; Wrighton, M. S. pH-Sensitive Nickel(II) Hydroxide-Based Microelectrochemical Tran-sistors. J. Phys. Chem. 1987, 91, pp. 1834−1842.Zaman, S.; Asif, M.; Zainelabdin, A.; Amin, G.; Nur, O.; Willander, M. CuO Nanoflowers as an Electrochemical pH Sensor and the Effect of pH on the Growth. J. Electroanal. Chem. 2011, 662, pp. 421−425.Zhang, Q.; Liu, W.; Sun, C.; Zhang, H.; Pang, W.; Zhang, D.; Duan, X. On-Chip Surface Modified Nanostructured ZnO as Functional pH Sensors. Nanotechnology 2015, 26(35), pp. 355202.Padmanathan, N.; Shao, H ; Razeeb, K. M., Multifunctional Nickel Phosphate Nano/Microflakes 3D Electrode for Electrochemical Energy Storage, Nonenzymatic Glucose, and Sweat pH Sensors. ACS Appl. Mater. Interfaces, 2018, 10 (10), pp. 8599–8610.