Visual Detection of Iodide Ion by Total Internal Reflection of Single Oxygen Microbubble

Facile and rapid detection of iodide ion (I–) has a substantial impact on nuclear chemistry, environmental monitoring, and other fields. Here, we report a new method for visual detection of I– at the single-microbubble level. This assay utilizes the total internal reflection of single O2 microbubble at the O2 microbubble–glass interface to produce the evanescent wave, which is imaged by a dark-field microscope. The diameter of the single O2 microbubble in the H2O2 aqueous solution increases after introduction of I–, thanks to its catalytic ability toward H2O2 decomposition. With this assay, I– is quantitatively determined based on the diameter change of the single O2 microbubble, along with micromolar level sensitivity, and the corresponding dynamic ranges from 0.08 to 1 mM. Impressively, this visual assay possesses high selectivity owing to the specific catalytic activity of I–, and it is successfully applied for detection of real water samples, showing satisfactory recovery rates. Our study opens up a single O2 microbubble analytical platform with a high spatial resolution because of the small size of the microbubble, which holds great promise in chemical and environmental applications.