New solid contact ammonium micropipette electrodes (ISE), well applicable in scanning electrochemical microscopy are reported. The solid contact was made of a PEDOT nanowire coated carbon fiber, lowered down close to the orifice, and dipped inside the cocktail being in the pipette tip. This configuration provided low electrical resistance and good potential stability. Submicron tip size, usual in case of micropipette ISE-s easily can be fabricated in this way. The applicability of the electrode in SECM has been proved in SG/TC mode imaging urease enzyme active spots in urea solutions.
Micropipette ion selective electrodes are very small, but fragile, short-life time sensors with very high resistance. Their high resistance is a draw back considering application in scanning electrochemical microscopy (SECM) and in life sciences. New, low resistance potassium micropipette electrodes were prepared, and applied. The electrode contains solid internal contact made of a carbon fiber lowered down all the way close to the orifice of the micropipette. The internal contact potential was kept constant by applying a doped, electrochemically prepared PEDOT coating on the fiber surface. The electrode performed well in in vivo experiments both in plant and animal tissue without capacitance neutralization and in SECM.
The diffusion coefficient of glucose in different media is an important parameter in life sciences, as well as in biotechnology and microbiology. In this work a simple, fast method is proposed that is based on the electrochemical time of flight principle. In most of the earlier time of flight experiments performed, a constant flight distance was applied. In the present work a scanning electrochemical microscope (SECM) was applied as a measuring tool. With use of the SECM, the flying distance could be changed with high precision, making measurements with several flight distances more accurate and reliable values could be obtained for solutions as well as for gels. The conventional voltammetric methods are not applicable for glucose detection. In our work electrocatalytic copper oxide coated copper microelectrodes and micro-sized amperometric enzyme sensors were used as detectors, while microdroplet-ejecting pneumatically driven micropipettes were used as a source.
The principle of a simple time of flight (TOF) diffusion coefficient measuring method is presented. It is based on the special capability of Scanning Electrochemical Microscopy (SECM). Its applicability has been investigated experimentally in comparison with conventional electrochemical methods. Complex irreversible electrode processes usually bring in uncertainty into electrochemical diffusion coefficient measurements. One of these, the electrochemical oxidation of saccharides in basic media at a copper electrode, was selected for the studies. Microsize copper electrodes used also as SECM tip, and conventional size copper electrodes were used. Diffusion coefficients of dglucose, d-arabinose, d-ribose, and d-galactose were measured. The results prove the advantages of the SECM-TOF method in the case investigated.
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