Effects of Strain and Kinetics on the H₂O₂-Assisted Reconstruction of Ag–Au–Ag Nanorods

Abstract

Morphology of Ag nanocrystals (NCs) is essential to the NC application in catalysis, optics, and as antibacterial agents. Therefore, it is important to develop synthetic methods and understand the evaluation of NC morphology in different chemical environments. In this study, we report interesting findings of the morphological change of fivefold-twinned Ag–Au–Ag nanorods (NRs) under the effect of H 2 O 2 both as an oxidant (etchant) and a reductant. At low H 2 O 2 concentration, the reconstruction of Ag–Au–Ag NRs was dominated by the growth along the longitudinal direction of NRs. With the increase of H 2 O 2 concentration, the reconstruction also occurs in the transverse direction, and a clear change in particle morphology was observed. We further systematically studied the mechanism of the reaction. The results showed that the transition of the morphology was a two-step process: (1) the etching of Ag on the seeds and (2) the reduction of Ag 2 O. In the second step, the reaction kinetics was highly affected by H 2 O 2 concentration. At low H 2 O 2 concentration, the growth mainly occurs along ⟨110⟩. However, at high H 2 O 2 concentration, the reduction of Ag was not facet-selective. Using the developed method, we can prepare various bimetallic NCs (high aspect ratio NRs with abundant pinholes, nanoplates, and other NCs). The effect of the reconstruction process on the surface-enhanced Raman scattering (SERS) performance of NCs was investigated.

Bifunctional SERS Paper Chips Based on Three-Layered Plasmonic Metal-Coated ZnO Nanoflowers for Fast Enrichment and Ultrasensitive Detection of Multiple Antibiotics

“…Nonetheless, the peak intensity still has 67% of the initial intensity after 30 days (Figure D). On the contrary, pure Ag colloids had only 40% of the initial intensity after 30 days in air . The above tests on sensitivity, uniformity, reproducibility, and stability demonstrate that the SERS paper chip exhibits great potential in practical applications.…”

“…Compared with individual plasmonic SERS substrates, the introduction of semiconductor oxides improves the SERS sensitivity from the charge transfer (CT) effect, as well as the EM effect. Meanwhile, semiconductor oxides have a stronger ability to adsorb analytes than plasmonic metals. − Moreover, since the nanogaps in SERS substrates can provide abundant “hotspots,” multilayered nanostructures with controllable nanogaps can generate the coupling of mutual polariton modes. − Hao et al reported that 5-fold-twinned Ag–Au–Ag nanorods (NRs) had an enhancement factor (EF) of 9.0 × 10 5 for SERS detection of 2-naphthalenethiol. Zha et al synthesized a Ag-multilayer-Au film with a limit of detection (LOD) of 10 –13 M for rhodamine 6G (R6G) detection.…”

“…19−21 Moreover, since the nanogaps in SERS substrates can provide abundant "hotspots," multilayered nanostructures with controllable nanogaps can generate the coupling of mutual polariton modes. 22−24 Hao et al 22 reported that 5-fold-twinned Ag− Au−Ag nanorods (NRs) had an enhancement factor (EF) of 9.0 × 10 5 for SERS detection of 2-naphthalenethiol. Zha et al 23 synthesized a Ag-multilayer-Au film with a limit of detection (LOD) of 10 −13 M for rhodamine 6G (R6G) detection.…”

Recent advances in solar‐driven CO2 reduction over g‐C3N4‐based photocatalysts

“…Compared with an individual component cocatalyst, the surface properties and electronic structure of alloy are tailored, which displays different CO 2 adsorption behavior and steers the d‐band centers of active sites, thus possessing great potential in improving the activity and selectivity of photocatalytic CRR 148,149 . For instance, as for PdCu alloy, Pd mainly works on water adsorption and activation, while Cu prefers to adsorb and activate CO 2 molecules in CRR 107 .…”

“…Compared with an individual component cocatalyst, the surface properties and electronic structure of alloy are tailored, which displays different CO 2 adsorption behavior and steers the d-band centers of active sites, thus possessing great potential in improving the activity and selectivity of photocatalytic CRR. 148,149 For instance, as for PdCu alloy, Pd mainly works on water adsorption and activation, while Cu prefers to adsorb and activate CO 2 107 As a result, when g-C 3 N 4 was integrated with PdCu alloy NPs through an in-situ approach, the resultant PdCu/g-C 3 N 4 composite exhibited 100% selection toward CO 2 to CH 4 conversion (Figure 19). In addition, it was found that the hydrogen amount adsorbed on Pd determines the CH 4 generation rate.…”