Sol−Gel Assembly of CdSe Nanoparticles to Form Porous Aerogel Networks

A detailed study of CdSe aerogels prepared by oxidative aggregation of primary nanoparticles (prepared at room temperature and high temperature conditions, >250 °C), followed by CO₂ supercritical drying, is described. The resultant materials are mesoporous, with an interconnected network of colloidal nanoparticles, and exhibit BET surface areas up to 224 m²/g and BJH average pore diameters in the range of 16−32 nm. Powder X-ray diffraction studies indicate that these materials retain the crystal structure of the primary nanoparticles, with a slight increase in primary particle size upon gelation and aerogel formation. Optical band gap measurements and photoluminescence studies show that the as-prepared aerogels retain the quantum-confined optical properties of the nanoparticle building blocks despite being connected into a 3-D network. The specific optical characteristics of the aerogel can be further modified by surface ligand exchange at the wet-gel stage, without destroying the gel network.