## 3 Results and Discussion
The PPy-Chi-BaFe\({}_{2}\)O\({}_{4}\) sensing layer was separately immersed in the glucose, fructose, and sucrose solutions in the concentration of 15 ppm. The concentrations of glucose, fructose, and sucrose solution were measured before and after the experiment. The degree of adsorption was calculated from [37]:  
\[\Pi\ =\ 100\times\frac{C_{i}-C_{f}}{C_{i}} \tag{3}\]  
where \(C_{i}\) and \(C_{f}\) were the initial and final concentration of the sugar. Figure 6a1,a2,b1,b2,c1,c2 shows the UV-visible spectra of the glucose, fructose, and sucrose in the concentrations of 2 ppm (0.2 mg/dL), 6 ppm (0.6 mg/dL), 15 ppm (1.5 mg/dL), 20 ppm (2 mg/dL), and 50 ppm (5 mg/dL). The main peak occurred at about 280 nm for them. The intensity peaks were driven for each concentration of the glucose, fructose, and sucrose. Figure 6a3, b3, c3 shows the variation of peak intensity with each concentration of the sugar as a calibration curve. Figure 6a2,b2,c2 show the UV-vis spectra of the sugar solutions after they contacted with the sensing layer and the concentration of glucose, fructose, and sucrose after contact with the PPy-Chi-BaFe\({}_{2}\)O\({}_{4}\) sensing layer was achieved from the calibration curve. As a result, the concentration of glucose was lower than that of the other sugars, and it means that the affinity of the PPy-Chi-BaFe\({}_{2}\)O\({}_{4}\) nanocomposite layer to the adsorption of the glucose is much higher than that of the other sugars. The concentration value of the sugar and the degree of adsorption are listed in Table 2.  
Figure 5: The variation of the resonance angle shift with time-related to (**a**) glucose, (**b**) fructose, and (**c**) sucrose. (**d**) Variation of the resonance angle shift with the concentration of the sugar. \begin{table}
\begin{tabular}{c c c c} \hline
**Sample** & **C\({}_{\textbf{i}}\) (ppm)** & **C\({}_{\textbf{f}}\)(ppm)** & **Degree of Adsorption (II)** \\ \hline
**Glucose** & 15 (1.5 mg/dL) & 1.05 (0.105 mg/dL) & 93\% \\
**Fructose** & 15 (1.5 mg/dL) & 2.7 (0.27 mg/dL) & 82\% \\
**Sucrose** & 15 (1.5 mg/dL) & 3.6 (0.27 mg/dL) & 76\% \\ \hline \end{tabular}
\end{table} 
Table 2: The concentrations of the sugar before and after adsorption with the sensing layer and the degree of adsorption of the sensing layer. Figure 6: **(a1,a2)** The UV-vis spectra of the different concentration of glucose (**b1,b2**) The UV-vis spectra of the different concentration of fructose, (**c1,c2**) The UV-vis spectra of the different concentrations of sucrose. The calibration curve for (**a3**) glucose, (**b3**) fructose, and (**c3**) sucrose. Magnetic nanoparticles and chitosan can be used for sugar sensor application, because they contribute to transfer the electron between a receptor (sensing layer) and sugar [1; 2; 16]. The BaFe\({}_{2}\)O\({}_{4}\) NPs can enhance the electron transfer between glucose, fructose, and sucrose with the sensing layer. The molecule of glucose contains one hydroxyl group (OH) and one hydroxymethyl group (CH\({}_{2}\)OH) at the edge of the molecule plane, and the hydroxyl group can interact with the BaFe\({}_{2}\)O\({}_{4}\) -NPs in the sensing layer. The difference between glucose and fructose is in the number of hydroxyl groups at the edge of molecule planes so that fructose contains two hydroxymethyl groups (CH\({}_{2}\)OH) at the edge of molecule plane, and they cause the space moment between fructose and BaFe\({}_{2}\)O\({}_{4}\) NPs. Moreover, the number of hydroxyl groups (OH) in glucose is higher than those in fructose. Therefore, the tendency of glucose to exchange the electron with a sensing layer is higher than fructose [2; 38]. The molecule of sucrose is a combination of glucose and fructose, and it is very heavy and stable. Hence, the tendency of sucrose to exchange the electron with BaFe\({}_{2}\)O\({}_{4}\) NPs is very weak. Consequently, the degree of adsorption for glucose is higher than the degree of adsorption of fructose and sucrose.