Lasers spectroscopy-electrochemistry

Laser Trapping-Spectroscopy-Electrochemistry of Individual Microdroplets in Solution (Nakatoni, Chikami, and Kitamura). 

In this review, we describe a laser trapping-spectroscopy-electrochemistry technique as a novel methodology for studying single microdroplets in solution and, demonstrate recent progress in the research on electron transfer and mass transfer across a microdroplet/solution interface in special reference to a droplet size dependence of the process. 

Figure 3. Block diagram of a laser trapping-spectroscopy-electrochemistry system.

The laser trapping-spectroscopy-electrochemistry technique is unique in that simultaneous three-dimensional manipulation and spectroscopic/elec-trochemical measurements can be conducted for individual microdroplets in solution. Although the technique is highly useful for studying single microdroplets, its applicability and limitations have not been well documented until now. Therefore, before discussing detailed chemistry of single droplets in solution, we describe briefly the characteristics of the technique. 

In Sections III and IV, we described droplet size dependencies of the ET and MT rates across microdroplet/water interfaces. Such experiments on single droplets are possible by the laser trapping spectroscopy-electrochemistry technique alone. Besides these experiments, the technique is also highly useful in controlling a reaction efficiency in microdroplets [99,100]. In this section, we describe electrochemically induced dye formation reactions across microdroplet/water interface and demonstrate control of the dye formation reaction yield in micrometer dimension. The effects of microenvironments and additives (surfactant or stabilizer) on dye formation reactions are also described. 

Direct determination of the rate of the C- or Y-Dye formation reaction in the individual microdroplets has been made possible by potential application of the laser trapping-spectroscopy-electrochemistry technique. Furthermore, the dye formation reaction efficiency in each droplet could be controlled arbitrarily by the distance between the droplet and the electrode. Under the present experimental conditions (i.e., pH 10 and [SO] ] =20mM), the diffusion length of QDI within its lifetime is only several micrometers, so the distance dependence of the reaction is unique in the micrometer dimension. The present approach will therefore lead to a new methodology to control chemical reaction in micrometer-size volumes. 

The laser trapping-spectroscopy-electrochemistry technique, capable of single microdroplet measurements, is shown to be indispensable in elucida-... 

K. Nakatani, K. Chikama and N. Kitamura, Laser Trapping-Spectroscopy-Electrochemistry of Individual Microdroplets in Solution in Advances in Photochemistry, Vol. 25, Ed. D.C. Neckers, D.H. Volman and... 

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