Plasmonic nanoparticles, such as Au, Ag, and Cu nanoparticles, can support the collective oscillation of free electrons in the metals excited by electromagnetic radiation, generating resonant extinction peaks and significantly enhanced electric near-fields as well as hot carriers. [1] The plasmonic properties of nanoparticles have enabled a vast range of applications, Ag nanorods receive intensive attention due to the excellent plasmonic properties. However, the difficulty in synthesis of monodisperse Ag nanorods with broad aspect ratios has limited their in-depth applications. Here, a seed-mediated method is reported for the synthesis of Ag nanorods with lengths from 65 to 5000 nm, corresponding to aspect ratios from 2 to 156. The plasmonic resonance is tuned from visible to mid-infrared wavelength. The synthesis protocol relies on robust Au seeds synthesized in N,N-dimethylformamide (DMF), which induces the one-dimensional (1D) growth of Ag atoms. To maintain symmetry breaking initiated by the Au seeds, the reduction rate of Ag + is decreased by adding hexadecyltrimethylammonium chloride (CTAC) to form AgCl particles. The optimized conditions to prevent the homogeneous nucleation of Ag nanoparticles and residue of AgCl particles in products are identified, under which the conversion efficiency of Ag ions to Ag nanorods is evaluated about 48%. More importantly, the anisotropic Ag nanorods are selfassembled into monolayers at interfaces with the long axis of Ag nanorods perpendicular or parallel to the interfaces, respectively. The as-fabricated monolayers exhibit uniform and reproducible surface-enhanced Raman scattering (SERS) activities. The optimal SERS performance is achieved from Ag nanorod monolayer with vertical orientation and the longest rod length.

Surface‐enhanced Raman spectroscopy (SERS) is a powerful surface analytical technique; however, its lack of material and morphological generality is a longtime limitation. The invention of shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) using silica shell‐encapsulated Au nanoparticles (NPs) overcomes these problems. Whereas, it is difficult to obtain a silica shell (less than 1 nm thick) without pinholes for generating extremely high SERS enhancements. Graphene is one of the most promising two‐dimensional materials, which has a single‐atom layer thickness. Moreover, graphene can provide additional SERS chemical enhancement. Herein, we prepared graphene‐coated Au (Au@G) NPs via chemical vapor deposition (CVD). The graphene shell thickness could be controlled from a few layers to multilayers, and the Au@G SERS activities were characterized using mercaptobenzoic acid (MBA) as a probe molecule. Both the pH and high‐temperature stabilities of the Au@G nanoparticles were characterized. Also, Pt‐on‐Au@G satellite structures were developed via a self‐assembly method. Whereby Au@G nanoparticles were coated with Pt nanocatalysts, and this bifunctional SERS substrate could be used to monitor in situ catalytic reaction mechanisms occurring on the Pt surface.

The Co-based electrocatalyst is among the most promising candidates for electrochemical oxidation of 5-hydroxymethylfurfural (HMF). However,the intrinsic active sites and detailed mechanism of this catalyst remains unclear. We combine experimental evidence and at heoretical study to show that electrogenerated Co 3+ and Co 4+ species act as chemical oxidants but with distinct roles in selective HMF oxidation. It is found that Co 3+ is only capable of oxidizing formyl group to produce carboxylatewhile Co 4+ is required for the initial oxidation of hydroxylgroup with significantly faster kinetics.A saresult, the product distribution shows explicit dependence on the Co oxidation states and selective production of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) and 2,5-furandicarboxylic acid (FDCA) are achieved by tuning the applied potential. This work offers essential mechanistic insight on Co-catalyzed organic oxidation reactions and might guide the design of more efficient electrocatalysts.