Resonance structure of quantum-dot-coated microspheres for microfluidic sensing

摘要

Optical microspheres can support whispering gallery modes whose resonance wavelengths are sensitive to the external medium. By coating the microsphere with a fluorescent quantum dot (QD) layer, the structure can perform as a fluorescence sensor for local refractometric changes. In these proceedings, we focus on the methods for fabricating and measuring a QD-coated silica microsphere. By constructing a system that uses a square capillary into which a single microsphere is inserted, a simple refractometric sensor can be demonstrated. The WGM resonance shifts were measured in sensorgram format as small amounts of solvent were pumped into the capillary. This method enables the sphere to act as a single passive microfluidic sensor for refractive index changes in the analyte. We finally discuss the main experimental problems that currently plague the application of these QD-coated fluorescent structures for sensing applications.