Perovskite nickelates as electric-field sensors in salt water

• Published in: Nature (London) 2018-01, Vol.553 (7686), p.68-72
• Main Authors: Zhang, Zhen, Schwanz, Derek, Narayanan, Badri, Kotiuga, Michele, Dura, Joseph A., Cherukara, Mathew, Zhou, Hua, Freeland, John W., Li, Jiarui, Sutarto, Ronny, He, Feizhou, Wu, Chongzhao, Zhu, Jiaxin, Sun, Yifei, Ramadoss, Koushik, Nonnenmann, Stephen S., Yu, Nanfang, Comin, Riccardo, Rabe, Karin M., Sankaranarayanan, Subramanian K. R. S., Ramanathan, Shriram
• Format: Article
• Language: English
• Subjects: 119/118; 140/125; 639/301/1005/1009; 639/638/298/917; 639/766/94; Ambient temperature; Biomonitoring; Dynamic stability; Electric fields; Electric properties; Electrodes; Environmental monitoring; Harsh environments; Humanities and Social Sciences; letter; Marine environment; Materials; MATERIALS SCIENCE; multidisciplinary; Nickel compounds; Offshore structures; Optical properties; Perovskite; pH effects; pH sensors; Phase transitions; Protons; Saline water; Salinity; Salts; Science; Seawater; Sensors; Signal monitoring; Thermistors; Thin films; Water
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature25008

Application of an electric field changes the transport and optical properties of samarium nickelate submerged in water, making it a suitable passive sensor of weak electric fields in salt water. Detecting a buzz in the water Detecting and measuring electric fields in salt water requires materials that do not corrode across a wide range of acidities, temperatures and salt concentrations, yet are not completely inert so that measurable property changes occur in response to electrical signals. Now, Shriram Ramanathan and colleagues show that, in the presence of an electric field, proton insertion into samarium nickelate (SmNiO 3 ) from water (with reduction of Ni) is accompanied by drastic changes in the transport and optical properties of the material. This enables very weak electric fields to be detected, owing to the change in resistivity of SmNiO 3 . Because it is also stable against salt water and in acidic and basic conditions, the authors propose that SmNiO 3 could be used as a passive sensor for weak electric and bioelectric signals in oceanic environments. Designing materials to function in harsh environments, such as conductive aqueous media, is a problem of broad interest to a range of technologies, including energy, ocean monitoring and biological applications 1 , 2 , 3 , 4 . The main challenge is to retain the stability and morphology of the material as it interacts dynamically with the surrounding environment. Materials that respond to mild stimuli through collective phase transitions and amplify signals could open up new avenues for sensing. Here we present the discovery of an electric-field-driven, water-mediated reversible phase change in a perovskite-structured nickelate, SmNiO 3 5 , 6 , 7 . This prototypical strongly correlated quantum material is stable in salt water, does not corrode, and allows exchange of protons with the surrounding water at ambient temperature, with the concurrent modification in electrical resistance and optical properties being capable of multi-modal readout. Besides operating both as thermistors and pH sensors, devices made of this material can detect sub-volt electric potentials in salt water. We postulate that such devices could be used in oceanic environments for monitoring electrical signals from various maritime vessels and sea creatures.