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

我们开发了荧光显微光谱技术与激光温度(T)跳跃方法相结合来分析微粒的化学和物理过程。在光学显微镜下，利用Nd3+和Gt；3+激光拉曼移位器，将一束12 0 nm(13 Ns)的光束聚焦到水中(光斑尺寸约2 0μm)。利用该技术可以产生大于ΔT~7K的T跳跃，并分析了焦域内时间分辨率为10^8 S的荧光响应。利用连续的Nd3+&Gt；：YVO4激光器，进一步发展了另一种T跳跃大于ΔT~10K(2~3μm)，时间分辨率为1ms的技术。这些技术被应用于聚(N-异丙基丙烯酰胺)水溶液的相分离相变和微粒的形成。在溶液中可直接测得S的相变时间为10μ。在50 nm大小的微孔中，相变时间大于10ms。用连续激光T跳跃技术测量了香豆素101在孔径为12 nm的ODS型硅胶中的粒子内扩散。作为综合测量手段，采用单微粒进样和吸收显微光谱分析，通过快速的浓度或pH变化来分析颗粒内扩散。当dp=12 nm时，与dp=3~30 nm的硅胶相似，颗粒内扩散受孔扩散的限制。另一方面，在d_p=~1 nm的甲壳素衍生物微球中，颗粒内扩散的速率控制步骤是表面扩散。我们的结论是，通过本技术的潜在应用，成功地阐明了微粒子系统中传质的微观机制。

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.