Poly(N-isopropylacrylamide)ゲル内のRhodamine 101のアンチストークス蛍光(商船・理工学)

概要

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Anti-Stokes fluorescence of poly(N-isopropylacrylamide)(PNIPA) gels in an aqueous solution of rhodamine 101dye was investigated in terms of the application of the fluorescence to an optical switch. The peak of the fluorescence is about 730 cm^<-1> higher in energy than the exciting photon (He-Ne laser at 632.8 nm). The spectrum intensity of the gel is higher than that of the solution. The spectrum intensity of the highly swollen gel below 〜25℃ shows the same temperature dependence as the solution. The dependence is described by the Boltzmann distribution function for the energy difference ΔE= 1400 cm^<-1>. As approaching the volume phase transition temperature, the intensity increases in faster than expected by the Boltzmann distribution. This implies that shrinking of the gel, namely, an increase in density of the polymer network, approaching the temperature causes an increase in the density of the dye due to hydrophobic interactions acting between the dye molecules and the PNIPA networks. Dynamics of the fluorescence intensity caused by temperature change was investigated. The response in the intensity consists of two parts, one is a faster response associating with the Boltzmann distribution, and another is slower one associating with the change in the gel volume. The results suggest a new application of the gel to an on-off fluorescence switch.
神戸大学の論文
2005-07-31