The fabrication of asymmetric monometallic nanocrystals with novel properties for plasmonics,
nanophotonics and
nanoelectronics. Asymmetric monometallic plasmonic nanocrystals are of both fundamental synthetic challenge and practical significance. In an example, a
thiol-ligand mediated growth strategy that enables the synthesis of unprecedented Au
Nanorod-Au
Nanoparticle (AuNR-AuNP) dimers from pre-synthesized AuNR seeds. Using high-resolution
electron microscopy and
tomography,
crystal structure and three-dimensional morphology of the
dimer, as well as the growth pathway of the AuNP on the AuNR seed, was investigated for this example. The
dimer exhibits an extraordinary
broadband optical
extinction spectrum spanning the UV, visible, and near
infrared regions (300-1300 nm). This unexpected property makes the AuNR-AuNP
dimer example useful for many nanophotonic applications. In two experiments, the dimer example was tested as a surface-enhanced
Raman scattering (SERS) substrate and a
solar light harvester for
photothermal conversion, in comparison with the mixture of AuNR and AuNP. In the SERS experiment, the dimer example showed an enhancement factor about 10 times higher than that of the mixture, when the
excitation wavelength (660 nm) was off the two
surface plasmon resonance (SPR) bands of the mixture. In the
photothermal conversion experiment under simulated
sunlight illumination, the dimer example exhibited an
energy conversion efficiency about 1.4 times as high as that of the mixture.