title: Au growth on semiconductor nanorods: photoinduced versus thermal growth mechanisms.
abstract: Gold growth on CdS nanorods and on seeded CdSe/CdS nanorods with and without illumination at different temperatures was studied. Two competing mechanisms were identified: thermal and light-induced growth. The thermal mechanism leads to growth of small gold particles at defects along the rod body and can be suppressed at lower temperatures. This control is attributed to a phase transition of the alkyl chains of the surface amine ligands to a static phase at lower temperatures, blocking the Au precursor's access to the nanorod surfaces. While a long-chain (C18) amine shows effective blocking at 293 K, a shorter chain (C12) amine shows the same result only at 273 K; however, in the case of a bulky trialkylamine, defect growth was observed even at 273 K. Light-induced growth leads to selective deposition of gold on one end of the rods. The tip was shown to grow on sulfur-rich facets of the nanorod, producing end-on and angled tip orientations. Growth under illumination with decreased temperature provides a highly selective synthesis of hybrid semiconductor nanorods with a single gold tip. Such anisotropic semiconductor-metal hybrids are of interest for self-assembly and photocatalysis and as building blocks in optoelectronic devices.
authors.affiliation: Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Gabi
authors.initials: G
authors.lastname: Menagen
authors.forename: Janet E
authors.initials: JE
authors.lastname: Macdonald
authors.forename: Yossi
authors.initials: Y
authors.lastname: Shemesh
authors.forename: Inna
authors.initials: I
authors.lastname: Popov
authors.forename: Uri
authors.initials: U
authors.lastname: Banin