Drop-pipette 743 dropping electrode

We usually prepare an unsealed DSSC and measure its photovoltaic performance. A spacer film, such as polyethylene (15-30 pm thickness), is placed on the dye-coated 2 photoelectrode and then the electrolyte solution is dropped on the surface of the Ti02 photoelectrode using a pipette (one or two drops). The counterelectrode is placed over the 2 photoelectrode and then the two electrodes are clipped together with two binder clips. If a low-melting-point polymer film such... 

UMEs used in our laboratory were constructed by sealing of carbon fibre into low viscosity epoxy resin (see Fig. 32.4) [118]. This method is simple, rapid and no specialised instrumentation is required. Firstly, the fibres are cleaned with this aim. They are immersed in dilute nitric acid (10%), rinsed with distilled water, soaked in acetone, rinsed again with distilled water and dried in an oven at 70°C. A single fibre is then inserted into a 100- iL standard micropipette tip to a distance of 2 cm. A small drop of low-viscosity epoxy resin (A. R. Spurr, California) is carefully applied to the tip of the micropipette. Capillary action pulls the epoxy resin, producing an adequate sealing. The assembly is placed horizontally in a rack and cured at 70°C for 8h to ensure complete polymerization of the resin. After that, the electric contact between the carbon fibre and a metallic wire or rod is made by back-filling the pipette with mercury or conductive epoxy resin. Finally, the micropipette tip is totally filled with epoxy resin to avoid the mobility of the external connection. Then, the carbon fibre UME is ready. An optional protective sheath can be incorporated to prevent electrode damage. 

BIA was introduced by Wang and Taha in 1990 [38] as an alternative to perform quick analysis in a very simplified way. In this system, the sample (typical volume 10-100 pi) is injected exactly on the center of the electrode, positioned from the bottom of the cell. During the injection process, the transport of the analyte to the electrode surface is intense and this is the reason for the elevated currents registered in this technique. Utilizing motorized pipettes, the transport of analyte is very reproducible and the dispersion is controlled in time and space. The peak response is a transient form (similar to FIA), which grows very fast, attains in short time a steady-state signal (there the injection attained a constant velocity), and drops very rapidly to the base line (Figure 3.7a). 

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