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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., (© 2023. The Author(s).)

Traditional "sandwich" structure immunoassay is mainly based on the self-assembly of "antibody on solid substrate-antigen-antibody with nanotags" architectures, and the sensitivity of this strategy is critically depended on the surface enhanced Raman scattering (SERS) activities and stability of nanotags. Therefore, the rational design and fabrication on the SERS nanotags attracts the common interests to the bio-related detecting and imaging. Herein, silica encapsulated Au with mercaptobenzoic acid (MBA) core-shell nanoparticles (Au-MBA@SiO 2 ) are fabricated instead of the traditional naked Au or Ag nanoparticles for the SERS-based immunoassay on human and mouse IgG antigens. The MBA molecules facilitate the formation of continuous pinhole-free silica shell and are also used as SERS labels. The silica shell is employed to protect MBA labels and to isolate Au core from the ambient solution for blocking the aggregation. This shell also played the similar role to BSA in inhibiting the nonspecific bindings, which allowed the procedures for constructing "sandwich" structures to be simplified. All of these merits of the Au-MBA@SiO 2 brought the high performance in the related immunoassay. Benefiting from the introduction of silica shell to encapsulate MBA labels, the detection sensitivity was improved by about 1-2 orders of magnitude by comparing with the traditional approach based on naked Au-MBA nanoparticles. This kind of label-embedded core-shell nanoparticles could be developed as the versatile nanotags for the bioanalysis and bioimaging., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A facile approach has been developed to fabricate multifunctional Fe3O4@AuAg alloy core-shell nanoparticles, owning the magnetism of the core and the surface enhanced Raman spectroscopy (SERS) activities of the alloy shell. By changing the amount of HAuCl4 and AgNO3, Fe3O4@AuAg alloy nanoparticles with different component ratios of Au and Ag were successfully prepared. The surface plasmon resonance of the composition was linearly tuned in a wide range by varying the molar fraction of Ag and Au, suggesting the formation of AuAg alloy shell. SERS and magnetic enrichment effects were investigated by using thiophenol (TP) as the probe molecule. The SERS intensity was strongly dependent on the molar ratios of Au and Ag and the excitation line. Enrichment for the molecules with low concentration and on line SERS monitoring experiments were performed through combining the magnetism of the core and the SERS effect of the alloy shell. The results revealed that the magnetic enrichment efficiency was dramatically increased due to the strong magnetism of Fe3O4 core. In addition, the Fe3O4@AuAg nanoparticles were also used in the microfluidic chip to continuously detect different flowing solution in the channel. The detection time and amount of analyte were successfully decreased., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Magnetic Fe2O3/Au core/shell nanoparticles can be particularly used in biological separation, but the development of an appropriate technique including a production process for higher efficient separation and the subsequent immunoassay for lower level still represent a great challenge. In this article, Fe2O3/Au core/shell nanoparticles with different Au ratios were prepared by reducing HAuCl4 on the surface of gamma-Fe2O3 nanoparticles. Scanning electron microscopy (SEM) images and surface-enhanced Raman spectroscopy (SERS) spectra clearly show that the surfaces of Fe2O3 nanoparticles were covered by Au. SERS signals of pyridine (Py) have been obtained on the Fe2O3/Au nanoparticles, and it has been found that the SERS intensity enhanced with the increase of iterative additions of HAuCl4. The antigens in test solution have been effectively separated by the magnetic Fe2O3/Au core/shell nanoparticles, and subsequent rapid detection was examined by immunoassay analysis based on SERS. The result demonstrates that the magnetic bioseparation program used by this magnetic Fe2O3/Au core/shell nanoparticles could separate almost all of the antigens in test solution. The ease of operation and good separation efficiency of this effective method has shown a potential application for magnetic Fe2O3/Au core/shell nanoparticles in bioseparation.

Ag-Au alloy seeds were prepared by the simultaneous reduction of Ag and Au salts. The seeds were grown via NH2OH x HCl-growth method to obtain novel Ag-Au alloy nanoparticles with diameters of 40-60 nm. The nanoseeds and novel nanoparticles were characterized by UV-Vis spectroscopy and TEM respectively. The observation of one surface plasma resonance absorption band, the redshift in their frequencies, and the uniform color of the nanoparticles shown in TEM images indicated the formation of alloy structure for both the nanoseeds and the novel nanoparticles. By using thiophenol (TP) as probe molecules, SERS studies were performed on the novel nanoparticles. The absorption bands of the nanoparticles red shifted with the addition of TP, and new bands were detected in the near infrared region, which were attributed to the aggregation of TP covered nanoparticles. With the excitation line of 632. 8 nm, the SERS intensity of TP on Au was most largely enhanced, and that on alloy nanoparticles were increased as X(Au) increased.

Layered core-shell bimetallic silver-gold nanoparticles were prepared by coating Au layers over Ag seeds by a seed-growth method. The composition of Ag100-xAux particles can vary from x=0 to 30. TEM and SEM images clearly show that the bimetallic nanoparticles are of core-shell structure with some pinholes on the surface. Strong surface-enhanced Raman (SER) signals of thiophenol and p-aminothiophenol have been obtained with these colloids. It was found that the SERS activity of aggregated colloids critically depends on the molar ratio of Ag to Au. With the increase of the Au molar fraction, the SERS activity enhances first and then weakens, with the maximal intensity being 10 times stronger than that of Ag colloids. The AgcoreAushell nanoparticles were then labeled with monoclonal antibodies and SERS probes and used for immunoassay analysis. In the proposed system, antibodies immobilized on a solid substrate can interact with the corresponding antigens to form a composite substrate, which can capture reporter-labeled AgcoreAushell nanoparticles modified with the same antibodies. The immunoreaction between the antibodies and antigens was demonstrated by the detection of characteristic Raman bands of the probe molecules. AgcoreAushell bimetallic nanoparticles, as a new SERS active and biocompatible substrate, will be expected to improve the detection sensitivity of immunoassay.

Abstract: A facile approach was developed to prepare novel multifunctional Fe2O3/Au/Ag nanostructures integrated with isolated functions involving magnetic and optical properties. The Fe2O3/Au/Ag hybrid nanoparticles with different thicknesses of Ag shell were prepared by adjusting the amount of the AgNO3. Surface structures were varied from the rough with pinhole to smooth and pinhole free surfaces with increasing amounts of AgNO3. The surface plasmon resonance was tuned in a very wide region from that of Au to Ag. Surface enhanced Raman scattering (SERS) effects were also investigated, employing thiophenol (TP) and aminothiophenol (PATP) as probe molecules. It was revealed that the SERS intensity was strongly depended on the molar ratio of Ag and Au. With an increase in the Ag molar fractions, SERS signals were enhanced to the maximum due to the surface plasmon resonance of the pinhole structure. The magnetic enrichment for on line SERS monitoring the molecules with low concentration was performed based on the magnetic core and the SERS activity of the bimetallic shells. This enrichment procedure improved efficiently the limits of the SERS detection. It was shown that the multicomponent nanoparticles have potential applications in the fields of optical devices and magnetic separation. [Copyright &y& Elsevier]