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. Author manuscript; available in PMC: 2008 Sep 19.
Published in final edited form as: J Am Chem Soc. 2007 Mar 3;129(12):3524–3526. doi: 10.1021/ja068452k

Figure 1.

Figure 1

(A) TEM images of polymer nanoparticles (PNPs) (∼56 nm) containing active perylene diimide dye and spiropyran dye. (B) 50-nm polymer nanoparticles (7.0 nM) fluoresce intense red while exciting at 420 nm; red-fluorescence gradually diminishes with concomitant increase in green fluorescence upon exposure to visible light (λ > 515 nm) at 8-10 × 10-9 Einstein. (C) Plot of a single cycle, in which the particle fluorescence switches from green to red in ∼30 sec under UV light 2.8 × 10-9 Einstein. (D) Plot of a single reverse cycle, in which the particle fluorescence switches from red to green. Particle size and concentration is same as (B). (E) Fluorescence switching between red color and green color was achieved while alternating UV and visible light illumination followed by fluorescence measurements at 420 nm, respectively. The UV light illumination period is 2 min and visible light illumination period is 20 min while all other parameters are same as B, C, and D.