Control of the optical properties of quantum dots by surface coating with calix[n]arene carboxylic acids.

A new method for the control of the optical properties of quantum dots (QDs) has been developed using calix[n]arene carboxylic acids (1-3) as surface coating agents for QDs. The calixarene coating of CdSe/ZnS QDs was easily performed in tetrahydrofuran at room temperature. Deprotonation of the carboxyl groups of the calixarene derivatives surrounding the QDs resulted in highly fluorescent water-soluble QDs. The emission peak of the calixarene-coated QDs shifted to longer wavelengths depending on the oligomer size of the calix[n]arene derivative used for the surface coating. Although the red shift of the emission peak decreases with the increase in the particle size of QDs, this surface coating method is useful for the preparation of multi-colored water-soluble QDs from a single-colored hydrophobic QD.