Subsequently, for more understanding of the role of hydrogen ion concentration, FET modelling is employed to obtain an equation between the conductance and pH of a solution, where the suggested structure of ISFET RG7112 is shown in Figure 2 with

source and drain as contacts. Ultimately, different pH values can be modelled by the pH of a solution (see the following equation). This means that G with pH can be shown as a function of pH values: (7) where the pH sensing factor ( ) is assumed and P H is the pH value. In the non-saturation region, the ISFET conductance model is shown as a function of gate voltage and the ideal conductance-voltage relation to the graphene channel of the ISFET device from Equations 5 and 7: (8) So, the G-V g characteristics of both the model and experimental data of graphene-based ISFET for changing the pH level in solution from 6 to 7 are plotted in Figure 7. Figure 7 G – V g characteristics of proposed conductance model with experimental data[42]. For solutions with (a) pH = 5 and (b) pH = 6. By comparing the suggested ISFET modelling based on the proposed parameter model with experimental data in Figure 7, similar PI3K inhibitor trends can be considered. In order to show all figures without overlapping,

each pH value has been plotted respectively in Figure  7 a,b. In addition, a detailed comparison between observed new

models per pH is illustrated in Figure 7, which demonstrates acceptable agreement with experimental data. In the suggested model, different pH values is demonstrated in the form of parameter which is in agreement with the reported data, as shown in Table 1. Table 1 Different pH values with Ƥ parameter Ƥ parameter values pH values 0.039105 5 0.035142 6 0.034918 7 0.034662 8 0.034437 9 0.034209 Pregnenolone 10 Therefore, based on the iteration method in Table 1, the electro-active ions absorbed by the surface of the ISFET channel as a pH sensing factor ( ) can be suggested by the following equations: (9) (10) According to the saturation region of the proposed conductance model belonging to the ISFET device, Equation 11 is acceptable for both the saturation behavior and experimental data from [42]: (11) From extracted data, α and β parameters are calculated, where α = 2.7318 and β = 4.5044. Consequently, based on the proposed model of the ISFET device, the conductance versus gate voltage is modified as (12) As can be seen in Figure 8, the theoretical G-V g characteristics of graphene-based ISFET for pH Vactosertib changes from 8 to 10 are plotted. Figure 8 G – V g characteristics of the proposed conductance model with experimental data. For solutions with (a) pH = 8, (b) pH = 9, and (c) pH = 10.