The alloying effect and AgCl-directing growth for synthesizing a trimetallic nanoring with improved SERS

Abstract

We report the synthesis of high quality trimetallic Au/Ag/Pt nanorings (TAAPNs) by using Au/Ag alloy decahedra (AAAD) as templates. The alloying effect and AgCl-directing growth have been investigated in detail during the formation of TAAPN. It was found that the doping of Ag in AAAD changes the surrounding environment of Au atoms and decreases the oxidization reduction potential (ORP) of [AuCl(2)](-)/Au because of the alloying effect, resulting in the dissolved O(2) molecules that serve as an effective etchant for oxidizing Au to Au(I). Ascorbic acid (AA) and chloroplatinic acid (H(2)PtCl(6)) are weak acids which can accelerate the etching by increasing the concentration of H(+). The AgCl selectively absorbs on {100} of the decahedra and induces the preferential deposition of H(2)PtCl(6) here via their complexing interaction. AA reduces Pt(IV) and Ag(I) to atoms which grow on {100} facets. The formed Pt/Ag layer changes the etching direction from along [100] to [111] and generates the TAAPN. Besides, it has been noted that the TAAPNs exhibit good Surface Enhanced Raman Scattering (SERS) performance.

Protein-Protected Porous Bimetallic AgPt Nanoparticles with pH-Switchable Peroxidase/Catalase-Mimicking Activity

“…Similar results were obtained for other bimetallic and trimetallic NPs. 45,46 To address the structural change of the surface capping agent (BSA) during the Ag NP and AgPt NP formation, spectroscopic measurements were performed using circular dichroism (CD) and fluorescence spectroscopy. The CD spectra of native BSA (N-form, aqueous solution, pH 6.5) shows one spectroscopic band at 190 nm in the positive absorption side and two other bands at ca.…”

“…At such pH, the galvanic exchange reaction dominates, leading to the formation of porous NPs. Similar results were obtained for other bimetallic and trimetallic NPs. , …”

Multilayer Ag-Embedded Silica Nanostructure as a Surface-Enhanced Raman Scattering-Based Chemical Sensor with Dual-Function Internal Standards

“…NPs as a SERS substrate have been developed in several directions: by using various kinds of metals such as noble and transition metals, adjusting the size of metals, changing particles’ shapes such as nanocubes, nanorods, nanowires, nanorings, and nanocrescents, and by arranging metal NPs as dimer, trimer, and aggregates, and by fusion of metals such as alloys. − Among the various nanomaterials exhibiting SERS enhancement, Ag NP-embedded silica nanospheres have sufficient SERS signals to be detectable by only one single particle because of the hotspot structure. , These nanostructures, capable of effectively emitting and retaining the SERS signal, enable high sensitivity to target molecules for polycyclic aromatic hydrocarbons, flavonoids and the like. ,,− Also, these easy-to-synthesize template-based nanostructures produced uniform signals and could be scaled up. Moreover, the application of the ligand and shell to the structure showed sensor stability and long-term stability …”

Empirical structural design of core@shell Au@Ag nanoparticles for SERS applications

“…[4][5][6] The SERS activity of metallic NPs is strongly dependent on the NP sizes, shapes, and geometries. 7,8 Due to their superior plasmonic property and especially electromagnetic enhancement in the visible range, 9,10 Ag-based NPs have been the major workhorse in SERS studies. However, it remains an experimental challenge to synthesis Ag NPs with uniform sizes and shapes and in turn to correlate the SERS performance of the Ag NPs with their structural features.…”