Refractometric sensing with fluorescent-core microcapillaries
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Abstract
A capillary-type fluorescent-core microcavity refractive index sensor based on whispering gallery mode (WGM) resonances is presented. The device consists of a glass microcapillary with a thin layer of fluorescent silicon quantum dots (QDs) coated on the channel surface. The high index of the QD layer confines the electric field near the capillary channel and causes the development of WGMs in the fluorescence spectrum. Refractometric sensing was achieved in these fluorescent-core microcapillaries (FCMs) by pumping aqueous sucrose solutions through the capillary while measuring the fluorescence WGMs with a spectrometer. A finite-difference frequency-domain model was developed and used to study the performance of the FCMs. While the observed refractometric sensitivity and detection limit of the current device were inferior to competing technologies, FCMs offer other practical advantages, such as straight-forward fabrication, robust samples, and minimal instrumental requirements, all of which make FCMs an appealing technology for integration with lab-on-a-chip devices.