We show that many complex gold nanostructures such as the water chestnut, dog bone, nanobar, and octahedron, which are not easily accessible via a direct seed-growth synthesis approach, can be prepared via overgrowth of the same gold nanorods by varying pH and Ag concentrations in the growth solution. Overgrown nanostructures’ shapes were determined by the rate of gold atom deposition, which is faster at higher pH. In the presence of AgNO 3 , codeposition of gold and silver atoms affects the shapes of overgrown nanostructures, particularly at high pH.

End-to-end dimers of gold nanorods are predicted to be excellent substrates for surface-enhanced spectroscopy. However, the synthesis of solution-stable end-to-end dimers remains challenging. We exploit the pH-dependent configurational change of polyelectrolytes to initiate and terminate the gold nanorod assembly formation to produce endto-end linked dimers in high yield. The gold nanorods are first overcoated with a polyelectrolyte, and the end-to-end attachment is initiated by adding a thiol linker in acidic medium. The assembly formation is then terminated at the dimer stage by changing the pH of the medium by the addition of an appropriate amount of 1,4-diazabicyclo[2.2.2]octane (DABCO).The nanorod dimers synthesized here are stable in solution for a week without any additional surface encapsulation.

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End-to-end assemblies of anisotropic plasmonic nanostructures with small nanogaps are of great interest as they create strong hot spots for enhancing weak fluorescence and/or scattering of molecules.

Pt and its alloys are commonly used as catalysts for electrochemical methanol oxidation reaction (MOR), owing to their high efficiencies. However, the high cost and instability of these catalysts due to poisoning from intermediates restrict their large-scale applications. Here we study plasmonic porous Au–Ag nanoparticles toward electrochemical and photoelectrochemical MOR. We synthesized Au–Ag@Au nanostructures that consist of the Au nanorod core and Au–Ag shell, where nanopores were created via selectively etching Ag atoms. The porous Au–Ag@Au nanostructures demonstrated significantly better MOR activity compared to their nonporous counterpart. Importantly, the presence of pores drastically suppressed the poisoning from the intermediate species, leading to a large improvement of their electrochemical stability. Furthermore, the porous Au–Ag@Au constructs showed strong enhancement of their catalytic activity under visible as well as near-infrared (NIR) excitations with generation of photocurrents of 1.23 and 0.45 mA mg–1 cm2, and with incident photon to current conversion efficiencies of 1.43 and 0.34% for visible and NIR wavelengths, respectively. Generation of photocurrents was shown to be predominantly due to the plasmonic hot-hole-assisted MOR.