Lyotropic Liquid Crystals as Nanoreactors for Nanoparticle Synthesis

A new methodology for the synthesis of nanoparticles using lyotropic liquid crystals as nanoreactors has been developed. The hydrophilic and hydrophobic domains of lyotropic phases have characteristic dimensions of 2−10 nm and thus can be used to confine reactants that are selectively soluble in only one domain to nanoscopic dimensions. Here, synthesis of Bi (a metal) and PbS (a compound semiconductor) nanoparticles is driven by bringing together reactants via the shear mixing of two liquid crystals, each containing dissolved reactants that are selectively soluble in one of the two phases, as proof-of-principle for this method. Modulating the phase of the lyotropic liquid crystals allows control over the geometry and interconnectivity of the nanoreactors, giving control over the diameter of nanoparticles produced. Decreasing concentration of precursors is shown to decrease particle size. It is also demonstrated that the nanoparticles produced are not agglomerated in the lyotropic liquid crystal during synthesis. The synthesized nanoparticles are characterized with TEM, electron diffraction, EDAX, and UV−Vis−NIR spectroscopy.