Abstract
Highly Sensitive Potassium-Doped Polypyrrole/Carbon Nanotube (K/PPy/CNT) - based Enzyme Field Effect Transistor (ENFET) has been modelled for Cholesterol Detection. The device consists of P-type graphene as substrate, N-type graphene as source and drain regions, ZrO2 as gate insulator and K/PPy/CNT composite as sensing membrane on the top of ZrO2 layer. The modelling is done using the enzymatic reactions of the enzyme cholesterol oxidase on cholesterol substrate, diffusion phenomena of the main substrate (i.e. cholesterol) in phosphate buffer saline (PBS) as electrolyte, acid/base reactions of the product (H2O2) in the PBS solution (pH=7) and the pH detection properties of ISFET. The thickness of the enzyme layer here is in nm range which is very less compared to other ENFETs whose thickness is in μm range. The use of K doped CNT as sensing membrane has increased the sensitivity of the device at normal temperature and pH. As a result of this increased sensitivity, variations of the substrate and product concentrations are noticed even at nanometer range of the enzyme layer which results in change in pH of the ISFET. The potential variation with change in pH is depicted by the model given by Bousse. A good fit is obtained between the modelling and experimental results
Published Version
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