A general strategy to facilely design ratiometric electrochemical sensors in electrolyte solution by directly using a bare electrode for dual-signal sensing of analytes

In this paper, we have described a general strategy to facilely design ratiometric electrochemical sensors in electrolyte solutions, directly using a bare electrode for dual-signal sensing of analytes. Two types of substances (methylene blue/MB, doxorubicin/DOX) with different electrochemical signal peaks were added into electrolyte solutions (phosphate buffered saline, NaCl), where one was the analyte (DOX) and the other was used as a reference (MB). A linear plotting of DOX concentration [DOX] versus ratiometric electrochemical signal peak intensity (I-DOX/I-MB) was achieved, with a good linear coefficient and low detection limit of DOX (0.4 nM). Experimental results implied that this ratiometric electrochemical sensor (ECS) of DOX enabled highly selective and sensitive detection of DOX in real samples, with high detection recoveries. In comparison with previous reports about ratiometric ECS, this as-proposed strategy can directly fabricate a ratiometric ECS in electrolyte solution (not on electrode), only using a bare electrode for dual-signal sensing of analytes. This strategy is not only novel and facile, but also flexible and general, as adequately confirmed in experiments, which would facilitate a further development in the facile fabrication and efficient applications of electrochemical sensors.