I am working on Metal Organic Frameworks for electrochemical sensing of organic pollutants. For this, I am preparing MOF solution (1mg/ml ethanol) and dropcast on GCE, air dry then drop cast nafion solution and further air dry. But compared to bare electrode the peak current of analyte (organic pollutant ) decreases or in most of cases peak disappears. Second problem, I am facing is the continuous decrease in peak current of MOF oxidation reduction peaks in successive CV run. Please suggest possible solution for this.
Just one clarification, is the presence of nafion the difference between the modified and non-modified electrode? Indeed nafion is good to improve the ionic conductivity but nafion id a polymer whose amount should be carefully adjusted: too much will lead to the decrease of the available surface and consequently to the measured current. If your experiment is carried out is solution and your material is directly in contact with the electrolyte I do not see a reason for it to be used. The situation is different if you are using a gas diffusion electrode. In the case you really have to use nafion, try to vary the amount to find the optimum. It will always be a tradeoff between improoved ionic conductivity and surface poisoning/coverage.
Concerning the fading of the redox peaks, did you try to decrease the upper and lower potential limits? It sounds to me like a material degradation which could occur during oxidation as well as reduction. Try to vary the upper and lower potential limits (change one parameter at the time, not the both of them). Is it also possible that the material itself get poisoned/deactivated by the byproducts of the pollutants decomposition or by other impurities which get adsorbed during the cathodic scan and that you do not remove during the anodic scan (halide absorption is a typical case for Pt-based catalysts)?
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