## 3 Results and Discussion
### Interfacial Parameters and Gibbs Adsorption Isotherm
#### 3.5.1 Surface Excess Concentration (\(\Gamma\))  
Surface excess concentration, \(\Gamma\), of the glucose-tyramine system was plotted against log C, as shown in Figure 6 and Table 1, which further supports our observed surface excess properties by specifying a gradual decrease in surface tension with the increase of temperature. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**m (mol-kg\({}^{-1}\))**} & \multicolumn{4}{c}{**T/(K)**} \\ \cline{2-5}  & **298.15** & **303.15** & **308.15** & **313.15** & **318.15** \\ \hline Glucose + aq. Taurine & \multicolumn{4}{c}{Surface excess concentration (\(\Gamma\)\(\times\)\(10^{-4}\)/mol m\({}^{-2}\))} \\
0.01 & 6.0341 \(\pm\) 0.023 & 5.6845 \(\pm\) 0.066 & 5.1978 \(\pm\) 0.011 & 4.8457 \(\pm\) 0.051 & 4.6561 \(\pm\) 0.038 \\
0.02 & 12.0683 \(\pm\) 0.022 & 11.3689 \(\pm\) 0.069 & 10.3956 \(\pm\) 0.020 & 9.6915 \(\pm\) 0.084 & 9.3122 \(\pm\) 0.093 \\
0.03 & 18.1024 \(\pm\) 0.024 & 17.0534 \(\pm\) 0.036 & 15.5931 \(\pm\) 0.051 & 14.5372 \(\pm\) 0.067 & 13.9683 \(\pm\)0.056 \\
0.04 & 24.1365 \(\pm\) 0.024 & 22.7379 \(\pm\) 0.030 & 20.7911 \(\pm\) 0.035 & 19.3829 \(\pm\) 0.030 & 18.6243 \(\pm\) 0.090 \\
0.05 & 30.1707 \(\pm\) 0.033 & 28.4224 \(\pm\) 0.091 & 25.9889 \(\pm\) 0.029 & 24.2287 \(\pm\) 0.061 & 23.2804 \(\pm\) 0.036 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Surface excess concentration (\(\Gamma\)\(\times\)\(10^{-4}\)/mol m\({}^{-2}\)) of aqueous taurine with D-glucose solutions at different temperatures. Figure 5: (**a**) Surface excess concentration (G) versus concentration plot of aqueous taurine with D-glucose at different temperatures, (**b**) Surface excess concentration (G) versus temperature (T) plot of aqueous taurine with D-glucose at different concentrations. It is clearly illustrated that at a concentration close to CMC, aggregation happened, which shows that adsorption tends to a limiting value, and therefore, the surface tension curve appears to be essentially linear. To study the interfacial properties of glucose in tyramine solutions, the surface tension of the linear portion (seen in Figure 4b) versus log C was fitted in the linear regression equation. From the value of slope (d\(\gamma\)/dlogC), the surface excess concentrations were evaluated by using the Gibbs adsorption isotherm (Equation (2) in Section 2.3). However, the concentration and temperature-dependent graphs of (\(\Gamma\)) are demonstrated in Figure 5a,b. Surface excess concentration decreases linearly with the increase of concentration, which indicates that at a low concentration, \(\Gamma\) is independent of temperature, whereas at a high concentration, \(\Gamma\) depends on temperature [4]. At a particular concentration, as temperature increases, the \(\Gamma\) value decreases, as shown in Figure 6. The reason for such behavior might be the high kinetic energy of the solute counterions. With the increase in temperature, kinetic energy increases because the holding capacity of the solute at the interface decreases, which leads to a decrease in the \(\Gamma\) values. Therefore, the surface tension of glucose in aqueous taurine also decreases because of the reduced force of attraction (IMF) between the molecules. For the tyramine system, the \(\Gamma\) values are shown in Table 1 and the illustrative plots are given in Figure 6. It is observed that as the temperature rises, there is a nearly consistent decrease in the \(\Gamma\) values. This is due to the expansion of monomers and hence, the smaller number of monomers located at the interface with increasing temperature. The positive isotherm of tyramine indicates its surfactant-like behavior, in which solutes mostly accumulate onto the surface [32]. As the concentration increases, the hydrophobic interactions increase in the case of the tyramine (because of the aromatic ring C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)-) group as compared to taurine (aliphatic chain). Similar behavior is observed in the work of [PERSON] et al.