Sol-gel synthesis of hybrid organic-inorganic monoliths doped with colloidal CdSe/ZnS core-shell nanocrystals

摘要

Colloidal CdSe/ZnS core-shell nanocrystals,with a narrow size distribution,were dispersed in a hybrid sol resulting formthe hydrolysis of tetraethylorthosilicate and 3-glycidoxypropyltrimethoxysilane (GLYMO).In orde to reduce the gleationtime and the exposure of the nanoparticles to air,several catalysts of the GLYMO epoxy ring opening were employed for the sol preparation,such as imidazole,methyl-imidazole,pyridine,benzylamine,propylamine. The role of the various catalysts was monitored by opticla absorption measurements in the near infrared region,by observing the evolution of the epoxy bands.Imidazole was found to provide the fastest gelation and the best results in erms of bubble disappearance from the gel structure. The vairation in the optical porperties of the semiconductor nanoparticles embedded in the matrix was monitored as a function of the gelation time and was compared to the opticla absorption and photoluminescence spectra of the nanoparticles dissolved in a chloroform solution. A decrease in the gelation-time results in a closer resemblance between theoptical properties of the CdSe/ZnS doped monoliths and those of the particles dissolved in the solvent,before incorporation in the matrix.The photoluminescence of the CdSe/ZnS nanocrystals is not bleached after they are trapped in the glassy matrix.