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Investigating the chemical nature of the adsorbed intermediate species on well-defined Cu single crystal substrates is crucial in understanding many electrocatalytic reactions. Herein, we systemati...

Plasmonic "hot spots" play a key role in surface-enhanced Raman scattering (SERS) enabling its ultrahigh surface sensitivity. Thus, precise prediction and control of the location of hot spots in surface nanostructures is of great importance. However, it is difficult to predict the exact location of hot spots due to complex plasmon competition and synergistic effects in three-dimensional (3D) multiparticle surface configurations. In this work, three types of Au@probe@SiO2 core-shell nanoparticles were prepared and a 3D hot spots matrix was assembled via a consecutive layer on layer deposition method. Combined with SERS, distinct probe molecules were integrated into different layers of the 3D multiparticle nanostructure allowing for the hot spots to be precisely located. Importantly, the hot spots could be controlled and relocated by applying different excitation wavelengths, which was verified by simulations and experimental results. This work proposes a new insight and provides a platform for precisely probing and controlling chemical reactions, which has profound implications in both surface analysis and surface plasmonics.

Controlling the size of nanoscale entities is important because many properties of nanomaterials are directly related to the size of the particles. Gold nanoparticles represent classic materials and are of particular interest due to their potential application in a variety of fields. In this study, hexanethiol-capped gold nanoparticles are synthesized via the Brust-Schiffrin method. Synthesized nanoparticles were characterized by various analytical techniques such as transmission electron microscopy, scanning tunneling microscopy (STM), UV-visible absorption spectroscopy and electrochemical techniques. We have varied the molar ratio of gold to the protecting agent (hexanethiol) to discover the effect of gold-to-hexanethiol ligand ratio on the size of gold particles. The clear correlation between particle size and molar ratio is found that the averaged particle size decreases from 4.28 ± 0.83 to 1.54 ± 0.67 nm as the gold-to-ligand molar ratio changes from 1:1 to 1:9. In contrast to a recent report that thiolated gold nanoparticles are under spontaneous disintegration when they are assembled on a gold substrate, our STM experiments proved that these gold nanoparticles can form a stable monolayer or multiple layers on the platinum electrode without observing disintegration within 72 h. Therefore, our STM experiments demonstrate that the disintegration behavior of gold nanoparticles is related to the type of ligands and the nature of substrate materials. In electrochemical experiments, these gold nanoparticles displayed an electrochemical quantized charging effect, making these nanoparticles useful in the device applications such as electrochemical or biological sensors.

The emerging field of plasmonics has promoted applications of optical technology, especially in plasmon-enhanced spectroscopy (PES). However, in plasmon-enhanced fluorescence (PEF), "metal loss" could significantly quench the fluorescence during the process, which dramatically limits its applications in analysis and high-resolution imaging. In this report, silver core silica shell-isolated nanoparticles (Ag@SiO2 NPs or SHINs) with a tunable thickness of shell are used to investigate the interactions between NPs and emitters by constructing coupling and noncoupling modes. The plasmonic coupling mode between Ag@SiO2 NPs and Ag film reveals an exceeding integrating spectral intensity enhancement of 330 and about 124 times that of the radiative emission rate acceleration for shell-isolated nanoparticle enhanced phosphorescence (SHINEP). The experimental findings are supported by theoretical calculations using the finite-element method (FEM). Hence, the SHINEP may provide a novel approach for understanding the interaction of plasmon and phosphorescence, and it holds great potential in surface detection analysis and singlet-oxygen-based clinical therapy.

A redox-active ionic liquid (IL), 1-butyl-1′-heptyl-4,4′-bipyridinium bis(trifluoromethanesulfonyl)imide, has been synthesized and its transport processes were investigated. The conductivity and viscosity of the IL, as well as the diffusion coefficients of its components were studied over a 50 °C wide temperature range: for the diffusivity studies, both the pulsed-gradient spin–echo (PGSE)–NMR technique and voltammetric measurements have been applied. The measured data are presented in the paper and are compared to each other. It was found that the diffusion coefficients determined by means of NMR and chronoamperometry measurements are, within the range of experimental error, equal—and they are (in accordance with other ionic liquid studies) higher than what the conductivity or viscosity measurements indicate. The results are interpreted in the light of the existing theories. The measured diffusion coefficients and bulk conductivities can be well interrelated based on the “ionicity” concept (that is, by t...

We have studied Au(55 nm)@SiO2 nanoparticles (NPs) on two low-index phases of gold and platinum single crystal electrodes in ClO4(-) and SO4(2-) ion-containing electrolytes by both electrochemical methods and in-situ shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS). We showed the blocking of the electrode with surfactants originating from the synthesis of as-prepared SHINERS NPs. We introduce an efficient procedure to overcome this problem, which provides a fundamental platform for the application of SHINERS in surface electrochemistry and beyond. Our method is based on a hydrogen evolution treatment of the SHINERS-NP-modified single-crystal surfaces. The reliability of our preparation strategy is demonstrated in electrochemical SHINERS experiments on the potential-controlled adsorption and phase formation of pyridine on Au(hkl) and Pt(hkl). We obtained high-quality Raman spectra on these well-defined and structurally carefully characterized single-crystal surfaces. The analysis of the characteristic A1 vibrational modes revealed perfect agreement with the interpretation of single-crystal voltammetric and chronoamperometric experiments. Our study demonstrates that the SHINERS protocol developed in this work qualifies this Raman method as a pioneering approach with unique opportunities for in situ structure and reactivity studies at well-defined electrochemical solid/liquid interfaces.