## 3 Results and Discussion
### Solid-State Studies  
The dispersion of ZnSO\({}_{4}\) in SP was investigated by XRD analysis (Figure 3). Multiple sharp peaks are shown in the profile of ZnSO\({}_{4}\), implying its crystalline property. On the contrary, sharp peaks were hardly shown in the XRD pattern of SP, as reported in our previous study [14]. This may suggest the amorphous property of SP, which would coincide with our previous result [14]. The broad peak of SP at 70 \({}^{\circ}\)C, observed via differential scanning calorimetry, implies the transition of SP from a glassy to a rubbery state [14]. The intensity of sharp peaks in the ZnSO\({}_{4}\)/SP NC group, compared with that of ZnSO\({}_{4}\), was attenuated.  
The dispersion of ZnSO\({}_{4}\) in SP was verified by XPS analysis (Figure 4). Chemical compositions in the outer layers (generally top 0 to 10 nm) of tested materials can be determined via XPS analysis.  
Figure 3: XRD profiles of ZnSO\({}_{4}\), SP, and ZnSO\({}_{4}\)/SP NCs. Counts values according to 20 are plotted.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Formulation** & **Mean Diameter (nm)** & **Polydispersity Index** & **Zeta Potential (mV)** \\ \hline ZnSO\({}_{4}\)/SP NCs & \(75\pm 2\) & \(0.10\pm 0.01\) & \(-1.0\pm 1.3\) \\ \hline \end{tabular}
\end{table}
Table 1: Particle characterization of ZnSO\({}_{4}\)/SP NCs (\(n\geq 3\)).  
Figure 2: Particle characterization of ZnSO\({}_{4}\)/SP NCs dispersion. (**A**) Particle size distribution and (**B**) TEM images of ZnSO\({}_{4}\)/SP NCs in distilled water (DW), pH 1.2 medium, and pH 6.8 buffer are presented. The length of scale bar in the TEM image is 200 nm.  
As shown in Figure 4A, the atomic portion of Zn 2p in ZnSO\({}_{4}\) was 12.76%. The peaks of S 2p and O 1s also indicated the presence of an SO\({}_{4}\)\({}^{2-}\) ion. The atomic percentages of C 1s, N 1s, and O 1s in SP were 67.29%, 0.51%, and 32.20%, respectively (Figure 4B). In the ZnSO\({}_{4}\)/SP NC group (Figure 4C), the contents of Zn 2p and S 2p were reduced to 0.61% and 0.66%, respectively. A dramatic decrease in the atomic percentages of Zn 2p and S 2p in ZnSO\({}_{4}\)/SP NCs, compared with those in ZnSO\({}_{4}\), indicates the presence of SP molecules in ZnSO\({}_{4}\)/SP NCs. The C 1s composition of ZnSO\({}_{4}\)/SP NCs (73.21%) was close to that of SP (67.29%), rather than that of ZnSO\({}_{4}\) (28.81%). This means that SP may be located on the outer surface of ZnSO\({}_{4}\)/SP NCs. Cl 2p in ZnSO\({}_{4}\) can be regarded as impurities. Its absence in the profile of ZnSO\({}_{4}\)/SP NCs implies the incorporation of ZnSO\({}_{4}\) in NCs.  
Figure 4: XPS profiles of (**A**) ZnSO\({}_{4}\), (**B**) SP, and (**C**) ZnSO\({}_{4}\)/SP NCs. Counts/s according to binding energy is plotted. The atomic percentage is shown in the graph.  
The fabrication of ZnSO\({}_{4}\)/SP NCs was identified via FT-IR analysis (Figure 5). A free SO\({}_{4}\)\({}^{2-}\) ion has four fundamental vibrations (\(\
u_{1}\), \(\
u_{2}\), \(\
u_{3}\), and \(\
u_{4}\)), and corresponding peaks have been observed in the spectrum of ZnSO\({}_{4}\) as reported [25]. Additionally, the broad band at 3117 cm\({}^{-1}\) may be due to the stretching mode of the water molecules. The carbonyl bands in the spectrum of SP were shown between 1800 and 1400 cm\({}^{-1}\). The peak at 1732 cm\({}^{-1}\) indicates OCOCH\({}_{3}\) or the ester group, and the other peak at 1628 cm\({}^{-1}\) means CON or amide group. Although these two peaks are shown in the spectrum of ZnSO\({}_{4}\)/SP NCs, the wavenumber (cm\({}^{-1}\)) and transmittance (%) of those peaks were slightly altered. This implies the dispersion of ZnSO\({}_{4}\) in SP by the HME process.