Raman Microspectroscopy/Imaging Study on Phase-Vanishing Processes of Fluorous Biphase Systems in Microchannel-Microheater Chips

Abstract

Temperature-dependent phase-vanishing processes between perfluorohexane (FC-72) and n-heptane (C7H16, volume ratio of 1:1 and phase-vanishing temperature > 41˚C), were studied in a glass microchannel-microheater chip under solutionflow conditions. Without applying a voltage to the heater at 21˚C, the two liquids in the microchannel were separated into two streams at a solution flow rate (v) of 0.975 cm/s, while the phase boundary between FC-72 and C7H16 vanished in the downstream side of the heater at V = 4.5 V. Then, we conducted Raman intensity imaging during the phase vanishing processes in the microchannel by monitoring the band at 756 (FC-72) or 1456 cm -1 (C7H16). At V = 4.5 V and v = 0.975 cm/s, although no phase boundary between the two liquids in the microchannel was observed, the relevant Raman intensity images indicated the inhomogeneous nature of the solution, and distribution of C7H16 to the FC-72 phase along with solution flow was observed.

Coherent anti-Stokes Raman scattering microscopy for quantitative characterization of mixing and flow in microfluidics

“…Building on this success, microfluidic devices with integrated Raman microscopy have shown they can monitor thermal and chemical gradients, product formation, and conformational changes [4][5][6][7][8][9]. Within such devices, optical resolution of molecular kinetics is limited more by the optical sectioning than by the stability of the conditions within the microfluidic device.…”

A spectroscopic study on medium polarity in fluorous alcohol

“…Although applications of the fluorous chemistry to synthetic reactions and separation sciences are very active research areas as mentioned above, physico-chemical properties of an F solvent and molecular-level solubilization behaviors between F and non-F liquids are still controversial. As an example, we found recently that, although perfluorohexane and n-heptane are mixed homogeneously above 41 8C as observed by naked eyes or under an optical microscope, Raman spectroscopic imaging experiments of the mixture demonstrated that the two liquids were not mixed homogeneously at a molecular level [5].…”

Polymer Channel Chips as Versatile Tools in Microchemistry

“…Raman spectroscopy/imaging can be also conducted by an analogous experimental setup. 19,20 By using a picosecond laser as an incident light source and a single photon counting system as a detector, 21 one can also perform picosecond time-resolved emission spectroscopy by using a microchannel chip. 15 Besides our experimental approaches, Kitamori et al have reported thermal lens spectroscopy for in situ observations of the phenomena proceeding in glass microchannel chips.…”