Green to red tunable upconversion fluorescence from Bi–Er–Yb codoped zeolites

We investigate the infrared-to-visible upconversion (UC) fluorescence properties of Bi–Er–Yb codoped zeolites. It is revealed that the UC emissions can be well controlled by the Yb3+ concentration in zeolites. By the addition of Yb3+, the green and red emissions are enhanced about 5 and 243 times, respectively. On the other hand, the intensity ratio of red-to-green is increased from 0.26 to 12.2. The tunable emission is due to the energy back transfer from Yb3+ to Er3+. It is expected that the achieved intense single band red emission may have potential application for in vivo bioimaging.

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► Bi–Er–Yb codoped zeolites are prepared by an ion-exchange process.
► The upconversion properties of Bi–Er codoped zeolites for different Yb concentration.
► Intense single band red emission can be achieved for high Yb3+ concentration sample.
► The tunable emission is due to the energy back transfer from Yb3+ to Er3+.