Lasers electrochemistry applications

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. 

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. 

On-chip detection firstly relied on optical techniques, such as ultraviolet (UV) absorbance, fluorescence or laser-induced fluorescence (LIF).1,2 The latter technique in particular has a sensitivity in the (sub)micromolar range which is suitable for microfluidic applications. Besides optical techniques, electrical-based techniques are also widely used for on-chip detection due to their sensitivity, e.g. detection based on conductivity,3 electrochemistry,4 electrochemiluminescence,5 etc. The main advantage of these techniques is that they... 

Although Raman spectroscopy does not employ absorption of infrared radiation as its fundamental principle of operation, it is combined with other infrared spectroscopies into a joint section. Results obtained with various Raman spectroscopies as described below cover vibrational properties of molecules at interfaces complementing infrared spectroscopy in many cases. A general overview of applications of laser Raman spectroscopy (LRS) as applied to electrochemical interfaces has been provided [342]. Spatially offset Raman spectroscopy (SORS) enables spatially resolved Raman spectroscopic investigations of multilayered systems based on the collection of scattered light from spatial regions of the samples offset from the point of illumination [343]. So far this technique has only been applied in various fields outside electrochemistry [344]. Fourth-order coherent Raman spectroscopy has been developed and applied to solid/liquid interfaces [345] applications in electrochemical systems have not been reported so far. 

---