Nano@micro: General method for entrapment of nanocrystals in sol-gel-derived composite hydrophobic silica spheres

Taleb Mokari, Hanan Sertchook, Assaf Aharoni, Yuval Ebenstein, David Avnir, Uri Banin

Research output: Contribution to journalArticlepeer-review

Abstract

A general method for entrapment of hydrophobically coated nanocrystals in micrometer and submicrometer composite silica spheres, nano@micro, was developed. The method employs two starting solutions-hydrophobic solvent containing the sol-gel precursor, a polymer, and the nanocrystals, and an emulsifying hydrophilic phase which catalyzes the sol-gel process. The use of a hydrophobic polymer, polystyrene, serves to encapsulate the nanocrystals inside the spheres while maintaining many of their original properties. The obtained nano@micro spheres were characterized structurally by transmission electron microscopy and scanning electron microscopy, chemically by energy dispersive X-ray spectroscopy, and optically by ensemble and single-particle fluorescence spectroscopy. It is possible to control the size of the microspheres from the 100 nm scale to the micrometer scale, with good monodispersivity and with good separation between the microspheres. The method is demonstrated for encapsulating a wide variety of nanocrystals, primarily semiconductors covering different spectral bands, and of different shapes including spheres and rods. The semiconductor nanocrystals impart widely tunable emission to the microspheres. A similar encapsulation technique was also applied to thiol-coated Au particles. The technique is generally applicable to other hydrophobic nanocrystal systems of magnetic, oxide, and other materials.

Original languageEnglish
Pages (from-to)258-263
Number of pages6
JournalChemistry of Materials
Volume17
Issue number2
DOIs
StatePublished - 25 Jan 2005
Externally publishedYes

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