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Keywords:

  • Semiconductors;
  • Quantum dots;
  • Nanoparticle assembly;
  • Optical properties;
  • Hierarchical structure

Abstract

Abstract. The synthesis of PbSe nanostructured gels via a sol-gel nanoparticle assembly method, followed by CO2-supercritical drying to make aerogels, is reported. Effective thiolate-capping of PbSe nanoparticles and the eventual controlled removal of the thiolates led to formation of a gel as opposed to a colloidal precipitate. Spherical PbSe nanoparticles were prepared by a precapping method, while cube-shaped nanoparticles were made by a post-capping procedure. Morphologically, spherical nanoparticles assembled into a colloidal (pearl-necklace) gel network, whereas cube-shaped nanoparticles formed a hierarchical gel network. Band-gap measurements show that both spherical and cube-shaped PbSe gels are blue shifted with respect to bulk PbSe, consistent with quantum confinement. Aerogels exhibit higher surface areas than xerogels indicating the higher degree of porosity and lower density of the former, and this is reflected in a greater extent of quantum confinement in aerogels relative to xerogels.