Surface plasmonics of nanomaterials has been one of the main research themes in nanoscience. Spherical and elongated nanoparticles show their corresponding unique optical features mainly depending on the physical dimensions. Here we successfully synthesized Au nanorings having Pt framework (Pt@Au nanorings) with high uniformity through wet-chemistry. The synthetic strategy consisted of serial reactions involving site-selective growth of Pt on the rim of Au nanoplates, subsequent etching of Au nanoplates, followed by regrowth of Au on the Pt rim. In this synthetic method, Au(3+) ions exhibited dual functionality as an etchant and a metal precursor. The resultant product, Pt@Au nanorings, exhibited unique localized surface plasmon resonance (LSPR) bands originating from the Au shell. The inner Pt skeleton turns out to be important to hold structural stability.

Herein, we report a general synthetic pathway to various shapes of three-dimensional (3D) gold nanoframes (NFs) embedded with a Pt skeleton for structural rigidity. The synthetic route comprises three steps: site-specific (edge and vertex) deposition of Pt, etching of inner Au, and regrowth of Au on the Pt framework. Site-specific reduction of Pt on Au nanoparticles (NPs) led to the high-quality of 3D Au NFs with good structural rigidity, which allowed the detailed characterization of the corresponding 3D metal NFs. The synthetic method described here will open new avenues toward many new kinds of 3D metal NFs.

In this report, we tune the surface plasmonic behavior of Au nanoplates depending on the morphology of the Pt shell in which Pt is considered as a less optically inactive element. We describe the synthesis of flat Au nanoplates coated with Pt via rim-preferential or uniform growth methods. Depending on the site-selective growth of Pt on core Au nanoplates, the aspect ratio of the resulting Au@Pt nanoplates was tunable and their corresponding surface plasmon resonance (SPR) bands were controlled accordingly. Although Pt is regarded as an optically weak component in visible and near infrared spectral windows, a Pt coating affects the SPR behavior of core Au nanoplates due to effective surface plasmon (SP) coupling between the Au core and the deposited Pt shell. We systematically investigated the optical properties of uniformly grown (Au@Pt(uni)) and rim-preferentially grown (Au@Pt(rim)) Au@Pt nanoplates by observing their SPR band shifts compared to SPR of Au nanoplates. Due to the structural rigidity conferred by the Pt coating, the Au@Pt nanoplates can be easily transferred to the investigated solvents.

Silver nanoparticles (NPs) ranging in size from 40 to 100 nm were prepared in high yield by using an improved seed-mediated method. The homogeneous Ag NPs were used as building blocks for 2D assembled Ag NP arrays by using an oil/water interface. A close-packed 2D array of Ag NPs was fabricated by using packing molecules (3-mercaptopropyltrimethoxysilane) to control the interparticle spacing. The homogeneous 2D Ag NP array exhibited a strong quadrupolar cooperative plasmon mode resonance and a dipolar red-shift relative to individual Ag NPs suspended in solution. A well-arranged 2D Ag NP array was embedded in polydimethylsiloxane film and, with biaxial stretching to control the interparticle distance, concomitant variations of the quadrupolar and dipolar couplings were observed. As the interparticle distance increased, the intensity of the quadrupolar cooperative plasmon mode resonance decreased and dipolar coupling completely disappeared. The local electric field of the 2D Ag NP array was calculated by using finite difference time domain simulation and qualitatively showed agreement with the experimental measurements.

Herein, we report ag eneral synthetic pathway to various shapes of three-dimensional (3D) gold nanoframes (NFs) embedded with aPtskeleton for structural rigidity.The synthetic route comprises three steps:s ite-specific (edge and vertex) deposition of Pt, etching of inner Au,and regrowth of Au on the Pt framework. Site-specific reduction of Pt on Au nanoparticles (NPs) led to the high-quality of 3D Au NFs with good structural rigidity,w hich allowed the detailed characterization of the corresponding 3D metal NFs.T he synthetic method described here will open new avenues towardm any new kinds of 3D metal NFs.Controlling the shape of noble-metal nanostructures has attracted enormous attention because it allows tailoring of their optical properties [1,2] enabling the nanostructures suitable for the applications,f or example,a sc atalysts, [3] biosensors, [4] substrates for surface-enhanced Raman scattering, [5] and photothermal therapy agents. [6] Among many metal nanostructures,A uN Fs [7][8][9][10] are particularly interesting compared to analogous solid NPs,b ecause their inner space can be utilized to enhance the permeability of chemicals and light, resulting in improved catalytic activity [11] and an enhanced electromagnetic field, [12] respectively.A uN Fs are commonly synthesized with limited success by the galvanic replacement reaction [13][14][15] between Ag NPs and Au ions.I nt he synthetic strategy,the morphology of Ag NPs dictates the final shape of the resultant Au NFs.However,itis still required to develop general synthetic pathways for NFs with agood controllability of composition, rim-thickness,size,and shape homogeneity. [16] Herein, we report the synthesis of 3D Au NFs (octahedral and cubic structures as proof-of-concept) and their corresponding optical properties.O ur results indicate that our proposed synthesis strategy is not limited to specific shapes. Additionally,t he Au NFs showed good stability under chemically harsh environments such as O 2 plasma treatment