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The structures and components of solid electrolyte interphase (SEI) are extremely important to influence the performance of full cells, which is determined by the formulation of electrolyte used. However, it is still challenging to control the formation of high‐quality SEI from structures to components. Herein, we designed bisfluoroacetamide (BFA) as the electrolyte additive for the construction of a gradient solid electrolyte interphase (SEI) structure that consists of a lithophilic surface with C−F bonds to uniformly capture Li ions and a LiF‐rich bottom layer to guide the rapid transportation of Li ions, endowing the homogeneous deposition of Li ions. Moreover, the BFA molecule changes the Li+ solvation structure by reducing free solvents in electrolyte to improve the antioxidant properties of electrolyte and prevent the extensive degradation of electrolyte on the cathode surface, which can make a superior cathode electrolyte interphase (CEI) with high‐content LiF.

Silver nanowire (Ag-NW) thin films have emerged as a promising next-generation transparent electrode. However, the current Ag-NW thin films are often plagued by high NW-NW contact resistance and poor long-term stability, which can be largely attributed to the ill-defined polyvinylpyrrolidone (PVP) surface ligands and nonideal Ag-PVP-Ag contact at NW-NW junctions. Herein, we report a room temperature direct welding and chemical protection strategy to greatly improve the conductivity and stability of the Ag-NW thin films. Specifically, we use a sodium borohydride (NaBH) treatment process to thoroughly remove the PVP ligands and produce a clean Ag-Ag interface that allows direct welding of NW-NW junctions at room temperature, thus greatly improving the conductivity of the Ag-NW films, outperforming those obtained by thermal or plasmonic thermal treatment. We further show that, by decorating the as-formed Ag-NW thin film with a dense, hydrophobic dodecanethiol layer, the stability of the Ag-NW film can be greatly improved by 150-times compared with that of PVP-wrapped ones. Our studies demonstrate that a proper surface ligand design can effectively improve the conductivity and stability of Ag-NW thin films, marking an important step toward their applications in electronic and optoelectronic devices.

We report the synthesis and characterization of gold core palladium shell (Au@Pd) nanoparticles with thicknesscontrolled shell as an improved transition-metal substrate for surface-enhanced Raman scattering (SERS). By changing the molar ratio of H 2 PdCl 4 to Au, the Pd shell thickness can be precisely controlled from a few nanometers down to ca. one monolayer. A series of characterizations were performed using transmission electron microscopy (TEM), UV-vis, SERS, and electrochemical techniques. The results confirmed the coreshell structure and the uniform and pinhole-free nature of the Pd shell, ensuring the properties of Pd without possible interference from Au. Consistent with theoretical prediction, the core-shell setting borrows high SERS activity from the Au core through the long-range electromagnetic enhancement in addition to the enhancement from the Pd shell itself. Moreover, their SERS activity can be optimized by the tunable shell thickness and core size. The nm-Au@Pd/Pd electrodes allow us to obtain good quality SER spectra of various molecules on Pd that were unable to be accessed with detail in the past. We believe that this borrowing strategy will be important for in-situ extracting of detailed vibrational information for adsorbates on catalytic Pd surfaces.

This discussion focuses on our recent approaches at aiming to optimize surface-enhanced Raman scattering (SERS) activity for transition metals (group VIII B elements), by intentionally fabricating desired surface nanostructures or synthesizing nanoparticles. The SERS activity of transition metals critically depends on the surface morphology of electrodes and on size, shape and aggregation form of nanoparticles. A correct surface roughening procedure for transition-metal electrodes is indispensable for fabricating cauliflower-like nanostructures that show a higher SERS activity. Two more methods have been explored to synthesize nanoparticles, i.e., cubic nanoparticles and gold-core palladium-shell nanostructures, respectively. Their SERS activities are considerably higher than those of normal spherical mono-metallic nanoparticles. To explain these observations, a preliminary theoretical calculation, using the three-dimensional finite difference time domain (3D-FDTD) method, was performed to evaluate the local electromagnetic field on transition metal surfaces. The result is in good agreement with the experimental data.

No abstract

In this paper, we propose a novel technique for the fabrication of active substrates of surface-enhanced Raman scattering (SERS). It was found that the silver particles themselves and the analyte-covered silver particles can be trapped at the air-water interface. In the presence of electrolyte, for example, KCl that is generally used to activate silver colloids for additional SERS enhancement, the trapped silver particles and clusters can attract each other spontaneously to form two-dimensional silver particle films. By this technique, the prerequisite aggregation of silver colloids for the SERS process is provided. At the same time, because the aggregation occurs only at the interface, problems of irreversible aggregation and instability of silver colloids can largely be overcome. The SERS enhancement ability of these silver particle films is larger by 1-2 orders than that of usual active substrates such as silver colloids and silver mirror. Their strong enhancement ability may arise from the unique two-dimensional structure itself.

Silver colloids are one of the extensively employed surface-enhanced Raman scattering (SERS) active substrates. To obtain the SERS effect, their aggregation upon addition of analyte is necessary. However, problems of instability and irreproducibility in the magnitude of the signal are caused by the formation of aggregates. Considering that the aggregation of silver colloids is essential to induce small silver clusters, in the present study, we develop a drying process to prepare silver particle films (silver clusters) that are supported directly on a glass slide. These silver particle films arise through the aggregation of silver colloids occurring in thin water films supported on a solid substrate. With the evaporation of water, silver clusters are left on the solid substrate. Thus, the assembly meets perfectly the requirement of aggregation of silver colloids and, at the same time, possesses the stability of solidlike SERS-active substrates. We can easily obtain excellent SERS spectra from these silver particle films. These substrates show great potential in practical applications such as ultrasensitive microanalysis with micro-Raman spectroscopy and are suitable for studying the optical properties of silver clusters. 4-Mercaptopyridine (4MPY) was used to test the utility of the proposed method and to compare it with the chemically deposited silver film (silver mirror) method. The intensity of SERS signals of 4MPY on the silver particle films is stronger by about 100 times than that of 4MPY on the silver mirror. In addition, the experimental results of SERS reveal that the activation agent, coadsorbed chloride ions, can further enhance the SERS signals from both the silver mirror and the silver colloids.