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Abstract: We describe a universal wet‐chemical shell‐by‐shell coating procedure resulting in colloidal titanium dioxide (TiO2) and iron oxide (Fe3O4) nanoparticles with dynamically and reversibly tunable surface energies. A strong covalent surface functionalization is accomplished by using long‐chained alkyl‐, triethylenglycol‐, and perfluoroalkylphosphonic acids, yielding highly stabilized core–shell nanoparticles with hydrophobic, hydrophilic, or superhydrophobic/fluorophilic surface characteristics. This covalent functionalization sequence is extended towards a second noncovalent attachment of tailor‐made nonionic amphiphilic molecules to the pristine coated core–shell nanoparticles via solvophobic (i.e. either hydrophobic, lipophobic, or fluorophobic) interactions. Thereby, orthogonal tuning of the surface energies of nanoparticles via noncovalent interactions is accomplished. As a result, this versatile bilayer coating process enables reversible control over the colloidal stability of the metal oxide nanoparticles in fluorocarbons, hydrocarbons, and water. [ABSTRACT FROM AUTHOR]

The facile assembly of shell-by-shell (SbS)-coated nanoparticles [TiO2PAC16]@shell 1- 7 (PAC16=hexadecylphosphonic acid), which are soluble in water and can be isolated as stable solids, is reported. In these functional architectures, an umpolung of dispersibility (organic apolar versus water) was accomplished by the noncovalent binding of ligands 1- 7 to titania nanoparticles [TiO2PAC16] containing a first covalent coating with PAC16. Ligands 1- 7 are amphiphilic and form the outer second shell of [TiO2PAC16]@shell 1- 7. The tailor-designed dendritic building blocks 3- 5 contain negative and positive charges in the same molecule, and ligands 6 and 7 contain a perylenetetracarboxylic acid dimide (PDI) core ( 6/ 7) as a photoactive reporter component. In the redox and photoactive system [TiO2PAC16]@shell 7, electronic communication between the inorganic core to the PDI ligands was observed. [ABSTRACT FROM AUTHOR]