Understanding the Colloidal Stability of Nanoparticle–Ligand Complexes: Design, Synthesis, and Structure–Function Relationship Studies of Amphiphilic Small‐Molecule Ligands

For effective application of nanoparticles, their amenability to in‐solution processing must be addressed, and stable, homogeneous solvent conditions are required. Although organic ligands have been used as surface‐modifying reagents for nanoparticles to increase their colloidal stability and homogeneity in solution, the structure–function relationships of nanoparticle–ligand complexes remain elusive and controversial. Herein, a series of novel amphiphilic small‐molecule ligands were designed, synthesized, and applied as surface‐modifying reagents for aqueous, transparent TiO2 and ZrO2 nanoparticles. The colloidal stability of the resulting nanoparticle–ligand complexes was found to depend not only on the chain length, but also on the relative balance between hydrophobicity and hydrophilicity. The structure of the ligands can be fine‐tuned to achieve “flexible colloidal stability”, thus significantly increasing complex stability in a variety of organic solvents. It′s a small world: A series of novel amphiphilic small‐molecule ligands were designed, synthesized, and applied as surface‐modifying reagents for aqueous, transparent TiO2 and ZrO2 nanoparticles. The structures of the ligands can be fine‐tuned to achieve “flexible colloidal stability”, significantly increasing complex stability in a variety of organic solvents.