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The solid-electrolyte interphase (SEI) plays crucial roles for the reversible operation of lithium metal batteries. However, fundamental understanding of the mechanisms of SEI formation and evolution is still limited. Herein, we develop a depth-sensitive plasmon-enhanced Raman spectroscopy (DS-PERS) method to enable in-situ and nondestructive characterization of the nanostructure and chemistry of SEI, based on synergistic enhancements of localized surface plasmons from nanostructured Cu, shell-isolated Au nanoparticles and Li deposits at different depths. We monitor the sequential formation of SEI in both ether-based and carbonate-based dual-salt electrolytes on a Cu current collector and then on freshly deposited Li, with dramatic chemical reconstruction. The molecular-level insights from the DS-PERS study unravel the profound influences of Li in modifying SEI formation and in turn the roles of SEI in regulating the Li-ion desolvation and the subsequent Li deposition at SEI-coupled interfaces. Last, we develop a cycling protocol that promotes a favorable direct SEI formation route, which significantly enhances the performance of anode-free Li metal batteries. The solid-electrolyte interphase is crucial for most batteries, but its characterization is challenging. Here, authors develop a depth-sensitive plasmon-enhanced Raman spectroscopy method to enable in-situ and nondestructive resolving of its structure and chemistry as well as formation mechanisms. [ABSTRACT FROM AUTHOR]

We have developed an electrostatic interaction based biosensor for thrombin detection using surface-enhanced Raman spectroscopy (SERS). This method utilized the electrostatic interaction between capture (thrombin aptamer) and probe (crystal violet, CV) molecules. The specific interaction between thrombin and aptamer could weaken the electrostatic barrier effect from the negative charged aptamer SAMs to the diffusion process of the positively charged CV from the bulk solution to the Au nanoparticle surface. Therefore, the more the bound thrombin, the more the CV molecules near the Au nanoparticle surface and the stronger the observed Raman signal of CV, provided the Raman detections were set at the same time point for each case. This procedure presented a highly specific selectivity and a linear detection of thrombin in the range from 0.1 nM to 10 nM with a detection limit of about 20 pM and realized the thrombin detection in human blood serum solution directly. The electrostatic interaction based technique provides an easy and fast-responding optical platform for a 'signal-on' detection of proteins, which might be applicable for the real time assay of proteins.

The adsorption and electrooxidation of CO molecules at well‐defined Pt(hkl) single‐crystal electrode surfaces is a key step towards addressing catalyst poisoning mechanisms in fuel cells. Herein, we employed in situ electrochemical shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) coupled with theoretical calculation to investigate CO electrooxidation on Pt(hkl) surfaces in acidic solution. We obtained the Raman signal of top‐ and bridge‐site adsorbed CO* molecules on Pt(111) and Pt(100). In contrast, on Pt(110) surfaces only top‐site adsorbed CO* was detected during the entire electrooxidation process. Direct spectroscopic evidence for OH* and COOH* species forming on Pt(100) and Pt(111) surfaces was afforded and confirmed subsequently via isotope substitution experiments and DFT calculations. In summary, the formation and adsorption of OH* and COOH* species plays a vital role in expediting the electrooxidation process, which relates with the pre‐oxidation peak of CO electrooxidation. This work deepens knowledge of the CO electrooxidation process and provides new perspectives for the design of anti‐poisoning and highly effective catalysts. [ABSTRACT FROM AUTHOR]

Deep‐learning‐based spectral identification received intensive interests benefiting from the availability of large scale spectral databases. However, for the identification of spectroscopic data such as Raman, the massive experimental data remained challenging, impeding the application of deep neural networks. Here, we describe a new approach with a transfer‐learning model pretrained on a standard Raman spectral database for the identification of Raman spectra data of organic compounds that are not included in the database and with limited data. Our results show that, with transfer learning, classification accuracy improvement of our convolutional neural network reaches 4.1% and that of our fully connected deep neural network reaches 5.0%. By investigating the influence of the source datasets, we find that our transfer learning method is able to incorporate both relevant and seemingly irrelevant source datasets for pretraining, and the relevant source dataset brings better classification accuracy than that of the seemingly irrelevant source dataset. This study demonstrates that the transfer learning technique has great potential in the effective identification of Raman spectra when the number of Raman data is limited. [ABSTRACT FROM AUTHOR]

Pyridine adsorbed on the group-VIIIA transition metal and the coinage metal (IB) electrode surfaces is employed as a model system to explore the metal-dependent nature of surface bonding. The periodic trends of the surface-enhanced Raman spectra are interpreted with the density-functional theory calculation results of bond geometries, bond energies, vibrational frequencies, and the force constants. On the basis of the normal-mode analysis the vibrational frequency shifts of the pyridine internal modes with the total symmetry are discussed in detail from the coupling between these internal modes and the N-M bonds. We show that the spectral properties of the ring breath mode (ν[SUB1]) and the ring asymmetric deformation mode (ν[SUB6a]) are sensitive to the interaction between metal and pyridine molecule. Although the frequency shift of the ν[SUB1] mode is generally regarded as an indicator of the bonding strength, we find that the frequency shift of the ν[SUB6a] mode has a nearly linear dependence on the force constant of the N-M bond; and thus conclude that ν[SUB6a] is a better indicator than ν[SUB1] for the strength of pyridine binding with the metals. [ABSTRACT FROM AUTHOR]

Abstract: Taking the fingerprint characteristics of Raman spectroscopy, the dimerization of p‐nitrothiophenol (PNTP) to 4‐nitrophenyl disulfide in air was investigated, which could be accelerated by the external laser illumination. The dimerization was qualitatively confirmed by both mass spectroscopy experimentally and by Raman spectrum simulated calculations theoretically and quantitatively analyzed by Raman spectroscopy in a simple and quick manner. On the basis of the inductively coupled plasma optical mass spectrometry analysis, the dimerization was possibly ignited by the trace metal residues as catalyst in the PNTP. This study clearly shows that it is very important to strictly and preciously control the experimental conditions of Raman measurement and other laser‐based spectroscopies to avoid any wrong conclusion during the characterization or identification. Different to the plasmon‐induced photochemical reactions, we reported the photochemical reaction of PNTP to 4‐nitrophenyl disulfide, which is free of the plasmoic effect from the metal nanostrucutres. On the other hand, the photochemical dimerization reaction may provide a new and important guideline for the formation of thiols to disulfides. [ABSTRACT FROM AUTHOR]