Temperature-jump and microspectroscopy technique for a study of mass transfer in a porous microparticle system

我们已经开发了荧光显微光谱技术结合激光温度（T）跳跃的方法来分析的化学和物理过程的微粒。使用Nd^<3+>：YAG激光拉曼位移器，在光学显微镜下将1200 nm（13 ns）的光束聚焦（光斑尺寸为1.20 μm）到水中。通过该技术，可以诱导大于ΔT〜 7 K的T跳跃，并分析了聚焦区域时间分辨率为10^8 s的荧光响应。利用连续Nd^<3+>：YVO_4激光器，又发展了一种T跃变大于ΔT = 10 K（2 × 3 μm），时间分辨为1 ms的技术。这些技术被应用到相转变和微粒形成的聚（N-异丙基丙烯酰胺）水溶液的相分离。在溶液中可直接测定相变时间为10 μs。在粒径为50 nm的微粒中，相变时间大于10 ms。香豆素101在孔径为12 nm的ODS硅胶中的粒内扩散可以用连续激光T跳技术测量。作为综合测量，使用单个微粒注射和吸收显微光谱，通过快速浓度或pH变化分析颗粒内扩散。在（dp）=12 nm的ODS硅胶中，与dp =3 ~ 30 nm的硅胶类似，颗粒内扩散受孔扩散的限制。而在d_p= 0.1nm的甲壳素衍生物微球中，粒内扩散的速率控制步骤为表面扩散。我们的结论是，微粒系统中的传质的微观机制成功地阐明了本技术的潜在应用。

We have developed fluorescence microspectroscopy techniques combined with laser temperature (T)-jump methods to analyzed chemical and physical processes for microparticles. Using a Nd^<3+>: YAG laser-Raman shifter, a light beam of 1200 nm (13 ns) was focused (spot size of〜20 μm) into water under an optical microscope. By the technique, T-jump greater than ΔT〜7K could be induced and fluorescence responses with temporal resolution of 10^8 s in the focused area were analyzed. Using a CW Nd^<3+>: YVO_4 laser, furthermore, another technique of T-jump greater than ΔT〜10 K (2〜3 μm) and temporal resolution of 1 ms was developed. These techniques were applied to phase transition and the microparticle formation by the phase separation of an aqueous poly (N-isopropylacrylamide) solution. The phase transition time could be directly determined to be 10 μs in solution. In 50 nm-sized pores of a microparticle, the phase transition time was greater than 10 ms. Intraparticle diffusion of coumarin 101 in ODS silica gel possessing pore diameter (d_p) of 12 nm could be measured by the CW laser T-jump technique. As comprehensive measurements, using single microparticle injection and absorption microspectroscopy, intraparticle diffusion was analyzed by quick concentration or pH change. Intraparticle diffusion in ODS silica gel with (d_p)=12 nm was limited by pore diffusion, analogous to that in silica gel with d_p=3〜30 nm. In a chitin derivative microsphere with d_p=〜1 nm, on the other hand, the rate-determining step of the intraparticle diffusion was surface diffusion. We conclude that the microscopic mechanisms of mass transfer in microparticle systems are successfully elucidated by potential applications of the present techniques.