Fluorescence yields of many organic dyes are enhanced via incorporation into DNA-surfactant complex which also extends the lifetime of the dyes. We have developed wavelength tunable lasers with hemicyanine dyes embedded in DNAcetyltrimethylammonium (DNA-CTMA). A couple of methods were applied to the dye doping, leading to different modes of interaction with DNA or its complex. Even though optical properties depended on the material structure reflecting preparation method, dyes showed good performance as laser media in various cases. Therefore, it is important to study the details of their interaction mechanism and the effects on their lasing performance. In order to investigate the interaction mode, three types of dyes were employed, that is, 4-[4-(dimethylamino)stylyl]-1-methylpyridinium iodide (DMASMPI or p-Hemi1), 2-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (o-Hemi1), and 2-(4- dimethylaminostyryl)-1-ethylquinolinium iodide (Quinaldine Red). Strong fluorescence enhancement and spectral shift of the dyes interacting with DNA in water suggested the importance of direct binding to DNA, while the dyes showed strongest fluorescence emission without significant spectral shift when interacting with DNA-CTMA in ethanol. The facts implied that multiple origins of fluorescence enhancement could be applicable to build up lasers. DNA-CTMA thin films incorporating the dyes were fabricated with several different methods aiming to control the interaction modes of the dye. p-Hemi1 doped thin films with 'immersion method' gave light amplification and laser oscillations in the range 590-620nm under optical pumping. The films operated more than 1 hour before the output stimulated emission diminished, showing strong durability of the dye in the complex.
Yuki Suzuki and Yutaka Kawabe, "Tunable lasers based on hemicyanines embedded in DNA complex," Proc. SPIE 9928, Nanobiosystems: Processing, Characterization, and Applications IX, 992809 (Presented at SPIE Nanoscience + Engineering: August 28, 2016; Published: 13 September 2016); https://doi.org/10.1117/12.2237432.
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