TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The colloidal solution has a dynamic viscosity of 4-54 cP, preferably 8-15 cP at 20 degrees C and 325 Pa. The solvent precursor comprises a first solvent and a second solvent. The first solvent is totally or partially consumed by the chemical conversion of second solvent, and the second solvent is totally or partially converted by hydrolysis of a third solvent. The solvent of colloidal solution comprises the third solvent, and optionally first and/or second solvent. The viscosity is controlled by stopping the step of the chemical conversion. The method comprises contacting the titanium oxide precursor with a biphase solvent, and converting the biphase solvent into a monophase solvent comprising the titanium oxide nanoparticles. The first solvent is water. The second solvent comprises: propylene carbonate (preferred); an alcohol having a vicinal diol such as propylene glycol; a derivative of vicinal diol such as 2-chloro-propan-1-ol; a triol having a vicinal diol such as glycerol (1,2,3-propanetriol); and/or a glycol ether. A molar ratio of the water and the propylene carbonate is 0.1-1.5, preferably 0.5-0.8. The titanium oxide precursor has a concentration of 0.005-0.1 mol.l-1. The hydrolyzing step is carried out using a hydrochloric acid to obtain a hydrochloric acid product, which is useful for a compound of the precursor solvent or a compound formed during the hydrolysis of the precursor solvent. The colloidal nanoparticle solution of titanium oxide is exposed to UV rays to improve its solar radiation absorption properties. The titanium oxide nanoparticles are present in the form of anatase, and have a hydrodynamic diameter of 2-50 (preferably 50-180) nm. Preferred Process: The deposition step is carried out by printing or coating, preferably spin coating, jet coating and screen printing and/or by performing roll-to-roll contact or optionally performing patterning on the substrate. The deposition step is carried out a temperature of 50-500 degrees C. The device is constituted by a p-i-n or n-i-p photovoltaic cells, an organic transistor, or an electroluminescent diode. EXAMPLE - A titanium precursor having a structure of formula ((Ti8O12(H2O)24)Cl8.HCl.7H2O) was converted into titanium oxide nanoparticles at a temperature of 120 degrees C in presence of a binary solvent mixture comprised of propylene carbonate and water. During the reaction, 1,2 propane-diol (or propylene glycol) and a 2-chloro-1-propanol with water molecules were formed. A concentration of reagents and a proportion of the solvents (water/propylene carbonate) were adjusted to form stable colloidal titanium oxide-containing solution.