Recent Advances in Bipolar Electrochemiluminescence for Analytical Application

Background: Bipolar electrode (BPE), as an immersed electrical conductor in the electrolyte, can be polarized into cathodic and anodic poles under a sufficient electric field without direct contact, which affords a unique way to promote asymmetrical reactions at two poles. Up to date, bipolar electrochemistry has been widely used in the preparation of Janus materials, the fabrication of sensing/screening platform, target focusing and microswimmers. However, the wireless feature of BPE makes monitoring the Faradaic current difficult. Electrochemiluminescence (ECL), the light emission via an electrochemical reaction, matches the feature of bipolar electrochemistry well and is widely adopted to achieve the record of the Faradaic current flowing through the BPE. The objective of the present review aims to demonstrate the most recent advances in analytical applications (2016-2020) in combination with the high sensitive ECL as the output. Methods: Due to the difficulty of the recording of the Faradaic current flowing the BPE, the ECL, as a simple, sensitive and detectable signal-out, has become a popular method for analytical application based on the BPE. This review mainly summarizes the recent research of BPE/ECL according to the configuration and sensing principle of BPE designed in the ECL analysis. Results: Various sensors based on the BPE/ECL have been proposed for the electroactive targets and the bio-relevant molecules without the electroactivity by different ingenious designs. Besides, the microelectrode array and ultra-microelectrode (UME) array have also been applied in the BPE/ECL field to achieve the high temporal-spatial resolution imaging of the sample molecules based on the BPE microelectrode array. Conclusion: The combination of BPE and ECL provides a simple, portable and versatile sensor strategy for various targets due to the unique advantages of BPE and ECL, and can be applied for the fast, accurate and point-of-care diagnostics of numerous diseases. Though the BPE/ECL analysis has many merits such as high-throughput, excellent sensitivity, and high spatial-temporal resolution, the sensitive and commercial ECL analysis based on the BPE is still difficult to realize and the analysis research of BPE/ECL is still in the early stage.