In Situ Ultrasound Irradiation for Regulating the Electrochemiluminescence Intensity and Layer

Electrochemiluminescence (ECL) hasmanifested a surface-confinedemitting character and a low light background occurring near the electrodesurface. However, the luminescence intensity and emitting layer arelimited by the slow mass diffusion rate and electrode fouling in astationary electrolyte. To address this problem, we developed an insitu strategy to flexibly regulate the ECL intensity and layer thicknessby introducing an ultrasound (US) probe to the ECL detector and microscope.Herein, we explored the ECL responses and the thickness of ECL layer(TEL) under US irradiation in different ECL routes and systems. ECLmicroscopy with an ultrasonic probe discovered that ultrasonic radiationenhanced the ECL intensity under the catalytic route, while an oppositetrend was observed under the oxidative-reduction route. Simulationresults demonstrated that US promoted the direct electrochemical oxidationof TPrA radicals by the electrode rather than oxidant Ru(bpy)(3) (3+), which made the TEL thinner than that in thecatalytic route under the same US condition. In situ US boosted theECL signal from 1.2 times to 4.7 times by improving the mass transportand weakening electrode fouling due to the cavitation role. It significantlyenhanced the ECL intensity beyond the diffusion-controlled ECL reactionrate. In addition, a synergistic sonochemical luminescence is validatedin the luminol system to enhance the whole luminescence because cavitationbubbles of US promoted the generation of reactive oxygen species.This in situ US strategy provides a new opportunity to understandECL mechanisms and a new tool in regulating TEL to meet the needsof ECL imaging.

Automated summary

This study developed an in situ strategy to regulate the intensity and layer thickness of electrochemiluminescence (ECL) by introducing an ultrasound probe. Ultrasonic radiation enhanced the ECL intensity under the catalytic route, while it had an opposite effect under the oxidative-reduction route. Ultrasound promoted the direct electrochemical oxidation of TPrA radicals, resulting in a thinner ECL layer. This in situ ultrasound strategy provides a new opportunity to understand ECL mechanisms and regulate ECL imaging.