Microemulsion (water-in-oil) methods enable the encapsulation of individual nanoparticles into SiO spheres. The major drawbacks of this method, when applied for silica encapsulation of anisotropic nanorods (NRs), are spatially unequal silica growth and long reaction times (24 h at least). In this work, various tetraalkoxysilanes [tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), and tetrapropyl orthosilicate (TPOS)] with different alkyl-chain lengths were used as silica precursors in attempt to tune the silanization behavior of CdSe/CdS NRs in a microemulsion system. We find enhanced spatial homogeneity of silica growth with decreasing alkyl-chain length of the tetraalkoxysilanes. In particular, by use of TMOS as the precursor, NRs can be fully encapsulated in a continuous thin (≤5 nm) silica shell within only 1 h reaction time. Surprisingly, the thin silica shell showed a superior shielding ability to acidic environment, even compared to the 30 nm thick shell prepared by use of TEOS. Our investigations suggest that the lower steric hindrance of TMOS compared to TEOS or TPOS strongly promotes homogeneous growth of the silica shells, while its increased hydrolysis rate decreases the porosity of these shells.
Gold
nanocrystals (AuNCs) were grown on the surface of silica-coated
CdSe-dot/CdS-rod core/shell NCs by reduction of Au3+ ions
in polyethylene glycol under ultrasonic irradiation. The polyethylene
glycol not only prevents the penetration of gold ions or precursor
molecules into the silica shell but also acts as the reducing agent
for Au3+ ions. The silica shell’s surface promotes
the heterogeneous nucleation of AuNCs, whereas the ultrasonic irradiation
accelerates and enhances the gold nucleation on the silica surface
and ensures the formation of AuNCs with a relatively narrow size distribution.
The plasmon–exciton interaction in these metal–semiconductor
hybrid systems leads to decreased fluorescence lifetimes and strongly
reduced fluorescence blinking of individual hybrid structures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.