Calixarene-encapsulated nanoparticles: Synthesis, stabilization, and self-assembly

Abstract

Calixarenes are highly versatile agents for encapsulating and stabilizing inorganic and metal nanoparticles (NPs), adding new dimensions to their already famous roles in supramolecular encapsulation. Calixarenes are excellent templates for metal NP synthesis, and offer a modular approach for controlling nucleation and growth processes with stoichiometric control over particle size. NP encapsulation is readily achieved by designing calixarene headgroups for multidendate chemisorption, an approach that can be applied toward particle sizes from 2 to nearly 200 nm in diameter. As NP size increases, longer-range colloidal forces dominate over short-range supramolecular interactions, requiring a different approach to dispersion stability and subsequent self-assembly. Again, calixarenes are outstanding surfactants for stabilizing NPs in organic solvents, by virtue of their anisotropic display of multiple tailgroups. Discussed here are the myriad roles that calixarenes play in metal NP synthesis, encapsulation, and self-assembly, ultimately leading to collective physical properties not observed from the unit NPs themselves.