## 4 Conclusions  
MoS\({}_{2}\)/TiO\({}_{2}\) heterostructures, consisting of MoS\({}_{2}\) slabs with different stacking order covering TiO\({}_{2}\) nanosheets, have been synthesized following ex situ and in situ methods. Combining XRD, HRTEM, Raman, UV-visible, and FTIR data, the characteristics of MoS\({}_{2}\)/TiO\({}_{2}\) heterostructures obtained from ex situ and in situ preparations were compared, highlighting the role played by the synthesis processes in affecting morphology, structure, stacking order, and defectivity. In more detail, MoS\({}_{2}\) slabs as obtained by the in situ preparation appear to be thinner and more defective (i.e., basal plane interruptions, more curved structures decorating the anatase facets) with respect to the slabs obtained by the ex situ preparation, despite the higher MoS\({}_{2}\) concentration. In particular, the stacking number of 3 \(\pm\) 2 layers and basal sizes of 2-10 nm for MoS\({}_{2}\) particles on MoS\({}_{2}\)/TiO\({}_{2}\) nanosheets coming from the in situ method could be estimated, whereas the stacking number \(>\) 5-6 and lateral dimension of 20 nm for MoS\({}_{2}\) particles on MoS\({}_{2}\)/TiO\({}_{2}\) nanosheets obtained by the ex situ method can be found. From the HRTEM analysis of samples obtained by the in situ method, the presence of more curved MoS\({}_{2}\) slabs decorating the boundaries of the anatase nanosheets means that a relevant grafting of MoS\({}_{2}\) particles at the [001] and [101] anatase facelets occurs. From this, it comes out that that the sulfidation process affects the reactivity of the support matrix as well, which in turn plays a role in the MoS\({}_{2}\)/support interaction. The low dimensionality of the MoS\({}_{2}\) particles on MoS\({}_{2}\)/TiO\({}_{2}\) nanosheets synthesized via the in situ approach with respect to those obtained by the ex situ method, already explained in terms of quantum size effects, has been additionally confirmed from the UV-vis results. Lastly, from the FTIR spectra, the presence of new Mo\({}^{\rm x+}\) species on defective sites, masking the Ti\({}^{4+}\) sites, which are no longer available for interactions with CO, is a further confirmation that MoS\({}_{2}\) slabs are thinner, more defective, and uniformly distributed for the sample prepared by the in situ approach, whereas MoS\({}_{2}\) slabs obtained via the ex situ  
Figure 7: FTIR spectra, recorded at 77K, at the maximum coverage of CO (30 Torr) adsorbed on the surface of TiO\({}_{2}\) anatase nanosheet (n-sh) pretreated at 873 K (black curve), of MoS\({}_{2}\)/TiO\({}_{2}\) n-sh obtained by the ex situ method (blue curve), and of MoS\({}_{2}\)/TiO\({}_{2}\) n-sh obtained by the in situ approach (red curve). approach are more heterogeneously dispersed with a higher level of stacking and then lower reactivity. In conclusion, we state that the morphology and dispersion of hybrid composites can be tailored by designing suitable preparation and activation conditions, also considering the interface structure and then the charge control. [PERSON], [PERSON], [PERSON], and [PERSON] wrote and organized the manuscript; [PERSON], [PERSON] and [PERSON] performed experiments and characterizations; in particular, [PERSON] contributed to sample preparation; [PERSON], [PERSON] and [PERSON] provided a substantial contribution to the work; [PERSON] supervised the manuscript. All authors approved it for publication. All authors have read and agreed to the published version of the manuscript. This work was supported by MIUR (Ministero dell'Istruzione, dell'Universita e della Ricerca), INSTM Consorzio and NIS (Nanostructured Interfaces and Surfaces) Inter-Departmental Center of University of Torino. Not applicable. **Data Availability Statement**: \"MDPI Research Data Policies\" at [[https://www.mdpi.com/ethics](https://www.mdpi.com/ethics)]([https://www.mdpi.com/ethics](https://www.mdpi.com/ethics)). The authors thank the Laboratory of the Chemistry Department and, in particular, [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON].