Luminescent Capillary-Based Whispering Gallery Mode Sensors: Crossing the Lasing Threshold

摘要

Silicon nanocrystals (Si NCs) present many advantages for sensor applications,rnincluding relatively bright and stable luminescence, low-to-negligiblerntoxicity, and high physical and chemical robustness. In this work, the effortsrnin creating capillary-based sensors from smooth films of oxide-embeddedrnSiNCs are summarized, and their responses to dye-doped polymer films arerncompared. The main method is to form sub-micrometer luminescent coatingsrnon microcapillary channel walls. The coating must have a high index ofrnrefraction so that it can support the luminescence whispering gallery modesrn(WGMs) which propagate through the film and extend into the channelrnmedium. Using Si NCs, a general refractometric sensing and the detection ofrnlayer-by-layer polyelectrolyte deposition on the capillary channel are demonstrated.rnThe Si NC sensors are exceptionally robust and can be cleaned andrnre-used multiple times. The main limitation of the method currently involvesrnthe relatively slow detection (requiring typically more than 20 s per collectedrnluminescence spectrum) due to the low light levels associated with the Si NCrnluminescence. Finally, our most recent work is discussed, which aims tornextend the luminescent capillary sensor into the lasing regime.