The I-V change is due to the carrier concentration gradient of the injected carriers from
the PBS to the channel and vice versa. The channel carrier concentration can be modeled in the function of gate voltage variations as (5) where V GS1(with PBS) is the gate voltage in the presence of PBS, V PBS is the voltage due to the interaction of PBS with CNT in the solution, and V GS(without PBS) indicates the gate voltage in a bare channel. The effect of PBS in the I-V characteristics is modeled as (6) Before glucose and PBS is added, V GS(without PBS) is set to be 1.5 V. The V PBS is found to 0.6 V when the PBS concentration, F PBS = 1 mg/mL, is added into
the solution. Using Equations 5 and 6, the presented model provides a good consensus between the model and the experimental data as shown in Pirfenidone Figure 3. Figure 3 Comparison of the I – V simulation output and the experimental data [[24]]. PBS concentration F PBS = 1 mg/mL, V GS(without PBS) = 1.5, and learn more V PBS = 0.6 V. In the glucose sensing mechanism reported in [24], β-d-glucose oxidizes to d-glucono-δ-lactone and hydrogen peroxide (H2O2) as a result of the catalyst reaction of GOx. The hydrolyzation of d-glucose-δ-lactone and the electrooxidation of H2O2 under an applied gate voltage produce two hydrogen ions and two electrons which contribute to the additional carrier concentration in the SWCNT channel. On the whole, the glucose sensing mechanism can be summarized as follows: (7) (8) (9) The variation of the proximal ionic deposition and the direct electron transfer to the electrode surface modify the electrical conductance of the SWCNT. The direct electron transfer leads to a variation of the drain current in the SWCNT FET. Therefore, Equation 10 that incorporates the gate voltage change due to the additional electrons from the glucose interaction with Pregnenolone PBS is given as (10) By incorporating Equation 10, Equation 6 then
becomes (11) V Glucose is the glucose-based controlling parameters that highlight the effects of glucose concentration against gate voltages. In the proposed model, Equation 12 is obtained by analyzing the rise I D with gate voltages versus glucose concentration. Based on the iteration method demonstrated in [37], the concentration control parameter as a function of glucose concentration in a piecewise exponential model is expressed as (12) In other words, the I-V characteristics of the biosensor can also be controlled by changing the glucose concentration. To evaluate the proposed model, the drain voltage is varied from 0 to 0.7 V, which is similar to the measurement work, and F g is changed in the range of 2 to 50 mM [24].