Size controlled gold tip growth onto II-VI nanorodsElectronic supplementary information (ESI) available: XPS data, TEM analysis, fitting parameters for kinetic model, PL spectra and XRD Scherrer analysis. See DOI: 10.1039/c0jm01689f

Gold tip size and multiplicity are controlled in hybrid gold-semiconductor nanorods (CdS-Au, CdSe-Au and CdTe-Au) in fast reaction times of less than 2 minutes by optimising precursor type, concentration and temperature. Controllable gold tips up to as large as 40 nm on a rod diameter of 7 nm are reported with the tip size shown to be directly related to the redox potentials of the dangling atoms on the nanorod and the gold chloride precursors (mono- or trivalent). The preference for symmetric (both ends) over asymmetric (single end) is achieved by simply elevating the reaction temperature to 80 °C without changing the reaction time. TEM and XRD analyses were preformed to verify both the gold nanoparticle size and crystallinity of the hybrid nanostructures. Increased quenching of nanorod emission is observed as the size of the gold tip increases suggesting optimisation of charge transfer between the semiconductor and the metal. Here we report size controlled gold tip growth up to six times the nanorod diameter of CdS, CdSe and CdTe nanorods. The gold tip size is controlled by a variation in gold concentration.