“Elastic” Property of Mesoporous Silica Shell: For Dynamic Surface Enhanced Raman Scattering Ability Monitoring of Growing Noble Metal Nanostructures via a Simplified Spatially Confined Growth Method

Abstract

ABSTRACT:The Raman enhancing ability of noble metal nanoparticles (NPs) is an important factor for surface enhanced Raman scattering (SERS) substrate screening, which is generally evaluated by simply mixing as-prepared NPs with Raman reporters for Raman signal measurements. This method usually leads to incredible results because of the NP surface coverage nonuniformity and reporter-induced NP aggregation. Moreover, it cannot realize in situ, continuous SERS characterization. Herein, we proposed a dynamic SERS monitoring strategy for NPs with precisely tuned structures based on a simplified spatially confined NP growth method. Gold nanorod (AuNR) seed NPs were coated with a mesoporous silica (mSiO 2 ) shell. The permeability of mSiO 2 for both reactive species and Raman reporters rendered the silver overcoating reaction and SERS indication of NP growth. Additionally, the mSiO 2 coating ensured monodisperse NP growth in a Raman reporter-rich reaction system. Moreover, "elastic" features of mSiO 2 were observed for the first time, which is crucial for holding the growing NP without breakage. This feature makes the mSiO 2 coating adhere to metal NPs throughout the growing process, providing a stable Raman reporter distribution microenvironment near the NPs and ensuring that the substrate's SERS ability comparison is accurate. Three types of NPs, i.e., core−shell Au@AgNR@mSiO 2 , Au@AuNR@mSiO 2 , and yolk−shell Au@void@AuNR@mSiO 2 NPs, were synthesized via core−shell overgrowth and galvanic replacement methods, showing the versatility of the approach. The living cell SERS labeling ability of Au@AgNR@mSiO 2 -based tags was also demonstrated. This strategy addresses the problems of multiple batch NP preparation, aggregation, and surface adsorption differentiation, which is a breakthrough for the dynamic comparison of SERS ability of metal NPs with precisely tuned structures and optical properties.

Reporter-Embedded SERS Tags from Gold Nanorod Seeds: Selective Immobilization of Reporter Molecules at the Tip of Nanorods

“…When the volume of AgNO 3 was increased to 100 μL, an anisotropic Ag coating occurred, leading to the tags with an orange slice-like shape ( Figure 2B). This anisotropic growth feature was consistent with Au/Ag NR growth from bare AuNR, 27,36 which indicated that the adsorbed Raman reporters did not influence the growth behavior of the silver shells. When the volume was increased to more than 300 μL, the tags became spherical and their size increased ( Figure 2C−E).…”

“…On the other hand, the silver shell of AuNR/Ag core/shell NPs evolved from homogeneous to special anisotropic coatings on AuNRs with increasing amounts of silver. 27 This would make the SERS signal evolution of the tags complicated. Moreover, AuNR was capped by a dense long-chain cetyltrimethylammonium bromide (CTAB) bilayer, which led to difficulties in Raman reporter adsorption.…”

Surface-enhanced Raman scattering on a silver film-modified Au nanoparticle-decorated SiO2 mask array

“…As shown in the literature, core@shell structures 12,13 and array substrates 14,15 have emerged as promising approaches for meeting these requirements of both effective enhancement and acceptable reproducibility. As shown in the literature, core@shell structures 12,13 and array substrates 14,15 have emerged as promising approaches for meeting these requirements of both effective enhancement and acceptable reproducibility.…”

Individually Silica‐Embedded Gold Nanorod Superlattice for High Thermal and Solvent Stability and Recyclable SERS Application

“…[1][2][3][4][5] This tunability of GNRs can be further enriched by collective plasmon coupling through the formation of periodic arrays of GNRs, [6,7] and thus provides potential applications such as sensors, [8][9][10][11][12][13] broadband absorbers, [14] plasmonic catalysts, [15] and other plasmonic devices. [1][2][3][4][5] This tunability of GNRs can be further enriched by collective plasmon coupling through the formation of periodic arrays of GNRs, [6,7] and thus provides potential applications such as sensors, [8][9][10][11][12][13] broadband absorbers, [14] plasmonic catalysts, [15] and other plasmonic devices.…”