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The reaction between titanium tetrachloride and benzyl alcohol in the presence of enediol ligands such as dopamine and 4- tert -butylcatechol provides a simple nonaqueous route to in situ surface functionalization of titania nanoparticles. The as-prepared precipitates are resoluble either in water or in organic solvents, depending on the ligand used. The surface chemistry of the 4- tert -butylcatechol-functionalized particles dissolved in dimethylformamide was analyzed by 1 H NMR measurements revealing the presence of adsorbed 4- tert -butylcatechol, in addition to benzyl alcohol and water. Although the reaction temperatures of 70 or 80 °C are relatively low, XRD and HRTEM investigations give evidence that the as-synthesized nanoparticles are highly crystalline. Ultracentrifugation analysis of dopamine-functionalized titania nanoparticles dissolved in water shows a particle size distribution of approximately 3.5−8 nm with the peak maximum at 5.5 nm. Furthermore, the UV−vis detector system of the ultracentrifuge allows the measurement of the absorption spectra dependent on the particle size, showing an unusual red shift with decreasing particle size.
Niederberger et al. (2004) studied this question.