Fabrication of color-tunable luminescent silica nanotubes loaded with functional dyes using a sol-gel cocondensation method.

Luminescent silica nanotubes SNT-2 (loaded with coumarion laser dye 2) and SNT-3 (loaded with anthracene laser dye 3) were prepared by sol-gel cocondensation of functional dyes and TEOS in a cholesterol-based organogel system. The emission colors of silica nanotubes were tuned by using different functional dyes. Interestingly, there is a great difference in PL spectrum of silica nanotubes loaded with functional dyes between ethanol and the solid state. In ethanol, a green light emission of SNT-2 and a bluish green light emission of SNT-3 were observed at 486 and 465 nm, respectively, because of the anchoring state between the dye and the tube, whereas in the solid state, strong blue light emissions of SNT-2 and SNT-3 were observed at 482 and 483 nm, respectively, because of the intense emission of the silica nanotube (SNT) itself rather than that of 2 and 3.