## 2 Results and Discussion  
### TiO2 Primary Particles and Their Nanoclusters  
Sol-gel methods involving thermal condensation reactions have been well-developed and widely applied to synthesize metal oxide NPs. Among them, the non-hydrolytic approach can better control the nucleation and growth of NPs at relatively low temperature, avoiding potential problems in the control of the nanoparticle morphology, surface composition, _etc._[39,40]. In this work, we have applied a modified non-aqueous process to synthesize TiO2 primary NPs, as detailed in the Experimental section. Then, the obtained TiO2 primary NPs were precipitated using diethyl ether. After the mother liquor was decanted, the precipitated TiO2 primary NPs were thoroughly washed with pure ethanol to remove all residues and finally re-dispersed in ethanol with the help of sonication. The XRD analysis shown Figure 1a indicates that the obtained TiO2 is pure anatase. The state of the dispersion was investigated by both TEM imaging and DLS measurements. From the TEM picture shown in Figure 2a, the TiO2 primary NPs in the dispersion are agglomerated in the form of nano-clusters (NCs), with an average diameter, \(D_{p}\approx 200\) nm. This is consistent with the average hydrodynamic diameter given by DLS and equal to 230 nm. Figure 1: (**a**) XRD patterns of the synthesized TiO2 and MPS modified TiO2, where the standard differential peaks of anatase TiO2 (JCPDS No. 21-1272) is shown as vertical bars; (**b**) FT-IR spectra of the TiO2 NCs before and after surface modification with MPS. Although TiO\({}_{2}\) in the form of NCs is necessary in our work, the average diameter of 200 nm is too large, and also the morphology appears rather loose, as shown in Figure 2a. Thus, we need to reduce the size and tune the morphology of the TiO\({}_{2}\) NCs. This can be done by intense sonication or by the ITS treatment [41]. In this work, we forced the TiO\({}_{2}\) NCs dispersion to pass through the MC device three times at an inlet pressure of 340 bar, corresponding to an average shear rate of \(\dot{\gamma}=3.0\times 10^{6}\) s\({}^{-1}\). After such ITS treatment, the hydrodynamic diameter of the TiO\({}_{2}\) NCs in ethanol measured by the DLS becomes 30.2 nm, as shown in Figure 3a, substantially smaller than the initial value of 230 nm. The TEM images of the TiO\({}_{2}\) NCs after the ITS treatment are shown in Figure 2b, which, when compared with Figure 2a, confirms the substantial reduction in the NCs size, and also a significant increase in compactness. It should be mentioned that the stable status of the TiO\({}_{2}\) NCs in ethanol after the ITS treatment also results from surface positive charges. In particular, due to the acidic condition, the ethoxyl groups on the TiO\({}_{2}\) surface are partially hydrolyzed, providing to the TiO\({}_{2}\) NCs a positive \(\zeta\) potential (+29.4 mV), thus improving the stability [42]. Figure 3: **(a)** Particle size distribution estimated from DLS in the cases of TiO\({}_{2}\) NCs, MPS modified TiO\({}_{2}\) and TiO\({}_{2}\)/PS NSs, respectively; **(b)** the experimental droplet diameter (\(D_{p}\)) of the mini-emulsion at equilibrium at the TiO\({}_{2}\)/monomer mass ratio, 1:2, as a function of the overall concentration of Tween 20 (\(C_{\rm T20}\)). The continuous curve presents the amount of Tween 20 required to fully cover the surface of our mini-emulsion droplets, computed based on Equation (1). Figure 2: TEM images of the synthesized TiO\({}_{2}\) nanoparticles in the form of nanoclusters **(a)** before and **(b)** after the ITS treatment. The surface modification of the TiO\({}_{2}\) NCs in ethanol with 3-(trimethoxysilyl) propyl methacrylate (MPS) was carried out by adding excessive amount of MPS. Under the acidic conditions, as reported in the literature [43; 44; 45], the hydrolysis and condensation of organosilane are slow and controllable, and most of them are covalently bonded to the surface of nanoparticles. The TiO\({}_{2}\) retains its anatase type after MPS modification, as shown in Figure 1a.