Control of Silver Coating on Raman Label Incorporated Gold Nanoparticles Assembled Silica Nanoparticles

Abstract

Signal reproducibility in surface-enhanced Raman scattering (SERS) remains a challenge, limiting the scope of the quantitative applications of SERS. This drawback in quantitative SERS sensing can be overcome by incorporating internal standard chemicals between the core and shell structures of metal nanoparticles (NPs). Herein, we prepared a SERS-active core Raman labeling compound (RLC) shell material, based on Au–Ag NPs and assembled silica NPs (SiO2@Au@RLC@Ag NPs). Three types of RLCs were used as candidates for internal standards, including 4-mercaptobenzoic acid (4-MBA), 4-aminothiophenol (4-ATP) and 4-methylbenzenethiol (4-MBT), and their effects on the deposition of a silver shell were investigated. The formation of the Ag shell was strongly dependent on the concentration of the silver ion. The negative charge of SiO2@Au@RLCs facilitated the formation of an Ag shell. In various pH solutions, the size of the Ag NPs was larger at a low pH and smaller at a higher pH, due to a decrease in the reduction rate. The results provide a deeper understanding of features in silver deposition, to guide further research and development of a strong and reliable SERS probe based on SiO2@Au@RLC@Ag NPs.

4-Mercaptobenzoic Acid Labeled Gold-Silver-Alloy-Embedded Silica Nanoparticles as an Internal Standard Containing Nanostructures for Sensitive Quantitative Thiram Detection

“…150 nm in diameter) were first functionalized with amine groups by 3-aminopropyltriethoxysilane (APTS) to prepare aminated silica NPs, as shown in Figure 1 [42]. Simultaneously, colloidal Au NPs (3 nm) were prepared using tetrakis(hydroxymethyl)phosphonium chloride (THPC) and incubated with the aminated silica NPs by gentle shaking to prepare Au NPs embedded with SiO 2 (SiO 2 @Au NPs), according to the method reported by Pham et al [38,39,40,41]. Subsequently, 4-MBA was introduced on the surface of SiO 2 @Au NPs through the strong affinity between thiol groups and Au, and it was used as an internal standard.…”

“…Whereas the maximum peak of SiO 2 @Au was at ~520 nm when the Au NPs were immobilized on the surface of SiO 2 NPs, the suspension of SiO 2 @Au@4-MBA@Ag NPs showed a broadband from 320 to 800 nm. This indicated the generation of irregular structures in the Ag shell and the creation of hot-spot structures on the surface of SiO 2 @Au@4-MBA@Ag NPs, producing a continuous spectrum of resonant multimode [38,39,40,41].…”

“…Previously, our group reported Au-Ag alloys assembled silica NPs (SiO 2 @Au@Ag NPs) as a strong and reliable SERS probe with 4-mercaptobenzoic acid (4-MBA) as an internal standard located between the SiO 2 @Au core and the Ag shell. SiO 2 @Au@4-MBA@Ag NPs were synthesized by Au seed-mediated Ag growth on the surface of a silica template, followed by incorporating 4-MBA on the surfaces [38,39,40,41]. However, their application for SERS detection has not been completely investigated.…”

Silver Nano/Microparticles: Modification and Applications 2.0

“…Due to this importance of silver materials, the first version of “silver nano/microparticles: modification and applications” was successfully published last year with 10 outstanding papers [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. This version 2.0 of the Special Issue also provides original contributions detailing the synthesis, modification, and applications of silver materials.…”

Silver Nano/Microparticles: Modification and Applications

“…The properties of silver nanoparticles have been widely studied, including by surface-enhanced Raman scattering (SERS). Pham et al reported the control of the silver coating on Raman label-incorporated gold nanoparticles assembled as silica nanoparticles for developing a strong and reliable SERS probe for bio-applications [14]. A SERS-active core Raman labeling compound shell material based on Au–Ag nanoparticles and assembled on silica nanoparticles can be used to solve signal reproducibility issues in SERS.…”