## 3 Results and Discussion
### SEM and XRD Characterization  
For sample preparation, a drop of highly diluted CS solution synthesized according to Reaction (1) was deposited on an appropriate stub and dried at room temperature overnight. Morphological characterization was performed by SEM analysis. In Figure 3a it is possible to notice the dispersion and size distribution of particles obtained by CS. The image shows an average diameter of about 1\(\upmu\)m.  
The observed values were higher than those found by DLS, because DLS measurements were carried out in solution, thus preventing the particle agglomeration undergone in the drying process. Figure 3b shows a detail of the particles in an image with 10,000\(\times\) magnification. Besides the spherical shape, a characteristic lamellar structure is visible. In Figure 4, a SEM image of the sulfur particles produced by means of SDR is reported. The particles have a spherical shape and the size distribution is in agreement with the results obtained through DLS analysis. In particular, on the picture the diameter of a particle is reported equal to 82 nm. In Figure 5, two micrographs of the S-TiO\({}_{2}\) particles at different magnifications are presented. The core-shell particles have a spherical shape and are sufficiently dispersed.  
Figure 4: SEM image of the sulfur particles produced by means of SDR.  
Figure 3: (a) SEM image of the sulfur particles produced by means colloidal sulfur (CS) solution; (b) particles at 10,000\(\times\) magnification.  
The average size can be estimated by referring to the micrograph in Figure 5b. The image shows an average size of particles produced between 75 and 100 nm. Compared to the method of [PERSON] et al. [21] the process used produced particles, on average, 10 times smaller. In Figure 6 the selected area for the EDX study and the corresponding energy spectra are presented.  
Both peaks related to sulfur and titanium can be observed, thus confirming the coverage of the particles by TiO\({}_{2}\). However, a little bit of NaCl was also detected. The presence of Si peak is due to the silicon support on which the material has been placed for SEM-EDX analysis. The sulfur and titanium distribution is represented by EDX maps in Figure 7a,b respectively. Since the dots referring to titanium are sparser than those related to sulfur, it is possible to argue that, despite the core-shell configuration expected, a more homogeneous TiO\({}_{2}\) coating is desirable.  
Figure 5: (a) A SEM image of S-TiO\({}_{2}\) core–shell particles;(b) a detail of the same image reporting the size of a particle.  
Figure 6: Energy dispersive X-ray (EDX) spectra of S–TiO\({}_{2}\) structures related to the onset selected area (800 nm \(\times\) 500 nm).  
Figure 7: EDX maps for S (a) and Ti(b) for a sample of S–TiO\({}_{2}\).  
Figure 8 shows the diffractometric patterns of the S-TiO\({}_{2}\) samples. The Crystallographic Open Database (C.O.D.), an open-access collection of crystal structures of organic, inorganic, metal-organics compounds and minerals, has been used to identify the orthorombic sulfur phase (C.O.D. codes: 1537087). Moreover, since the spectrum of S-TiO\({}_{2}\)nanopowders presents peaks of low intensity, it is possible to deduce that the material is not highly crystalline, especially when compared with the results obtained by other authors [1; 37; 38]. Actually, the peaks of TiO\({}_{2}\) are absent, thus highlighting that the coating is amorphous. Someimpurities like NaCl are also present in both cases (C.O.D. codes: 9006376).