Synthesis of Monodisperse Spherical Nanocrystals

Abstract

Much progress has been made over the past ten years on the synthesis of monodisperse spherical nanocrystals. Mechanistic studies have shown that monodisperse nanocrystals are produced when the burst of nucleation that enables separation of the nucleation and growth processes is combined with the subsequent diffusion-controlled growth process through which the crystal size is determined. Several chemical methods have been used to synthesize uniform nanocrystals of metals, metal oxides, and metal chalcogenides. Monodisperse nanocrystals of CdSe, Co, and other materials have been generated in surfactant solution by nucleation induced at high temperature, and subsequent aging and size selection. Monodisperse nanocrystals of many metals and metal oxides, including magnetic ferrites, have been synthesized directly by thermal decomposition of metal-surfactant complexes prepared from the metal precursors and surfactants. Nonhydrolytic sol-gel reactions have been used to synthesize various transition-metal-oxide nanocrystals. Monodisperse gold nanocrystals have been obtained from polydisperse samples by digestive-ripening processes. Uniform-sized nanocrystals of gold, silver, platinum, and palladium have been synthesized by polyol processes in which metal salts are reduced by alcohols in the presence of appropriate surfactants.

Driving oxygen coordinated ligand exchange at nanocrystal surfaces using trialkylsilylated chalcogenides

“…1 A central strategy used to achieve such control is the passivation of NC surfaces by hydrophobic ligands, such as oleic acid or octadecylphosphonic acid. 2 However, for many applications it is necessary to replace the generic hydrophobic ligands with specific functional ligands, e.g., in order to facilitate aqueous dispersion, 3 enable specific targeting 4 or 20 add complementary optoelectronic functionality. 5 It remains a significant challenge to find general and efficient mechanisms for such ligand exchange reactions.…”

Size, Shape, and Phase Control in Ultrathin CdSe Nanosheets

“…31 If the thickness is in direction and the lateral growth is along the [0001] and [11][12][13][14][15][16][17][18][19][20] axis, the calculated XRD shows sharp (002) and (110) peaks with increased intensity, while the (100) peak is broadened and less intense.…”

Controllable Cobalt Oxide/Au Hierarchically Nanostructured Electrode for Nonenzymatic Glucose Sensing

“…Lower temperatures produce larger HGNs that scatter more light and appear blue or green, while higher temperatures produce HGNs that appear purple or red. It was determined that temperature was directly proportional to the size of the cobalt sacrificial template produced, with higher temperatures producing smaller Co core (Pu and Song et al, unpublished) This is believed to be the result of the thermodynamic influence on nucleation which is controlled in part through the increase in surface free energy associated with the increase in reaction temperature [123,124].…”