Fine-Tuning the Homometallic Interface of Au-on-Au Nanorods and Their Photothermal Therapy in the NIR-II Window.

The localized surface plasmon resonance (LSPR) of plasmonic nanomaterials is highly dependent on their structures. Going beyond simple shape and size, further structural diversification demands the growth of non-wetting domains. Now, two new dimensions of synthetic controls in Au-on-Au homometallic nanohybrids are presented: the number of the Au islands and the emerging shapes. By controlling the interfacial energy and growth kinetics, a series of Au-on-AuNR hybrid structures are successfully obtained, with the newly grown Au domains being sphere and branched wire (nanocoral). The structural variety allowed the LSPR to be fine-tuned in full spectrum range, making them excellent candidates for plasmonic applications. The nanocorals exhibit black-body absorption and outstanding photothermal conversion capability in NIR-II window. In vitro and in vivo experiments verified them as excellent photothermal therapy and photoacoustic imaging agents.

Site-specific growth of gold nanoparticles on Bismuth Selenide hexagonal nanoplates.

Highly site-specific growth of gold nanoparticles (AuNPs) on Bismuth Selenide (Bi2Se3) hexagonal nanoplates was achieved by fine-tuning the growth kinetics of Au through controlling the coordination number of the Au ion in MBIA-Au3+ complex. With increasing concentration of MBIA, the increased amount and the coordination number of the MBIA-Au3+ complex results in the decrease of the reduction rate of Au. The slowed growth kinetics of Au allowed the recognition of the sites with different surface energy on the anisotropic Bi2Se3 hexagonal nanoplates. As a result, the site-specific growth of AuNPs at the corner, the edge, and the surface of the Bi2Se3 nanoplates were successfully achieved. This way of growth kinetic control was proven to be effective in constructing well-defined heterostructures with precise site-specificity and high purity of the product. This is helpful for the rational design and controlled synthesis of sophisticated hybrid nanostructures and would eventually promote their applications in various fields.

Continuous tuning the wetting growth of Au on Se nanoparticles.

We show that the wetting growth of Au on Se seed nanoparticles can be continuously tuned through manipulating the growth kinetics - the reduction rate of HAuCl4 and the inhibiting effect of DPI-SH ligand. As a result, a series of Se-Au hybrids and anisotropic Au semi-shell structures with different sizes were successfully obtained. With the structural variations, the absorptions of Se-Au hybrids and LSPRs of the Au semi-shells can be continuously tuned within the Visible-NIR spectral range. Our work provides convenient while efficient means for tailoring the Au-based heterostructures and the anisotropic Au nanostructures.

Designing caps for colloidal Au nanoparticles.

The plasmonic property of a nanostructure is highly dependent on its morphology, but there are few methods for appending a domain as the "functional group" or modifier. As a means of modulating plasmonic properties, we create and modulate Au hats on Au nanoparticles, including mortarboards, beret hats, helmets, crowns, antler hats and antenna hats. The structural control arises from the active surface growth as a result of dynamic competition between ligand absorption and metal deposition. It allows the continuous tuning of hat morphologies, from the facet-controlled growth of mortarboards, to the spreading-favored growth of beret hats and helmets, and to the vertical growth of pillars in crowns, antler hats and antenna hats. Among these plasmonic nanostructures, the mortarboards show excellent SERS enhancement of 8.1 × 105, which is among the best in colloidal nanostructures; and the antler hats show the photothermal conversion efficiency of 66.2%, which compares favorably with the literature reports.