Topological materials, well-known for their exotic surface states that have intrigued physicists for years, are offering new surprises in areas of electrochemistry and biosensing. A new study, led by Yingjie Zhang, assistant professor of Materials Science and Engineering at the University of Illinois at Urbana-Champaign, demonstrated the use of bismuth telluride (Bi2Te3), a topological insulator, for ultrasensitive electrochemical detection of hydrogen peroxide (H2O2).
Hydrogen peroxide is an important chemical regulating various biological metabolisms such as cellular signaling, oxidative stress, aging, and cancer growth. The intracellular concentration of hydrogen peroxide, in the typical range of 10 nanomolar to 1 micromolar, is a critical indicator of human health conditions. "While enzyme-based electrochemical sensors have been developed and clinically used for H2O2 detection, they have high cost and low chemical and thermal stability," said Zhang. "We want something cheaper and more robust".
Electrochemical sensing inherently depends on the interfacial charge transfer between the electrode and the liquid solution. The highly delocalized surface states of topological insulators attracted the attention of the Zhang lab, as a candidate for initializing facile charge transfer. “We chose to use Bi2Te3, a well-known topological insulator, to fabricate electrochemical sensors," said Fujia Zhao, a graduate student and lead author on this work. "These devices showed exceptionally high performance, producing high currents in response to trace amounts of H2O2." The detection limit, a critical figure of merit of biosensors, reaches ~16 nanomolar, a lower limit highly desired for human health monitoring.
Figure: Schematic of the electrochemical sensor (left) and its response to trace amounts of hydrogen peroxide (right).
Going beyond the demonstration of high performance, the Zhang lab also performed detailed analysis on the fundamental mechanisms behind the high sensitivity. They used a series of electrochemical techniques, including cyclic voltammetry, electrochemical impedance spectroscopy, and microkinetic simulations, to examine the interfacial charge transfer kinetics. Through these investigations, they observed a very low charge transfer barrier at the Bi2Te3 – aqueous solution interface, which can likely be attributed to the high carrier mobility and strong delocalization at the topological surface states. “Such properties are commonly seen in many topological materials, and we expect a wider application of these materials in electrochemistry,” said Shan Zhou, a postdoctoral research associate and co-author of this work. “We are excited about these results, and are exploring these series of materials for clinical applications,” Zhang said.
The paper “Ultrasensitive Detection of Hydrogen Peroxide Using Bi2Te3 Electrochemical Sensors” can be found here: