Highly Sensitive and Reproducible SERS Performance from Uniform Film Assembled by Magnetic Noble Metal Composite Microspheres

Abstract

To realize highly sensitive and reproducible SERS performance, a new route was put forward to construct uniform SERS film by using magnetic composite microspheres. In the experiment, monodisperse Fe3O4@SiO2@Ag microspheres with hierarchical surface were developed and used as building block of SERS substrate, which not only realized fast capturing analyte through dispersion and collection under external magnet but also could be built into uniform film through magnetically induced self-assembly. By using R6G as probe molecule, the as-obtained uniform film exhibited great improvement on SERS performance in both sensitivity and reproducibility when compared with nonuniform film, demonstrating the perfect integration of high sensitivity of hierarchal noble metal microspheres and high reproducibility of ordered microspheres array. Furthermore, the as-obtained product was used to detect pesticide thiram and also exhibited excellent SERS performance for trace detection.

Polyethyleneimine-mediated seed growth approach for synthesis of silver-shell silica-core nanocomposites and their application as a versatile SERS platform

“…Fig. 6c shows the SERS spectra of thiram in ethanol, with concentrations ranging from 1.0 Â 10 À5 M to 1.0 Â 10 À10 M with SiO 2 @PEI@Ag NPs (300 nm core) as SERS substrate; the intensity of the Raman peaks of thiram located at 932, 1148, 1383, and 1508 cm À1 were observed at concentrations as low as 10 À8 M. The most prominent peak around 1385 cm À1 was observed at concentrations as low as 10 À9 M. All of the major vibrational modes of thiram observed are consistent with previous reports, 39 as categorized in Table S1. † The detection limit of thiram in the experiment (10 À9 M) is lower than the maximum residue limit of 7 ppm (0.03 mM) in fruit, as prescribed by the U.S. EPA.…”

Quantitative SERS by hot spot normalization – surface enhanced Rayleigh band intensity as an alternative evaluation parameter for SERS substrate performance

“…In addition to SERS intensity, reproducibility is another important factor that dictates SERS substrate performance. 30–32 Accordingly, the variation of I Rayleigh across a Raman map before analytes were added was recorded and compared with the variation in the Raman signal across a SERS map after 4-MBA addition. I Rayleigh is expected to be a predictive factor of both SERS substrate efficiency as well as homogeneity.…”

Increasing local field by interfacial coupling in nanobowl arrays

“…As a dielectric gap, the thin SiO 2 layer could be used to tune the stretching, C-C stretching of the aromatic ring, C-H in-plane bending, C-H out-of-plane bending and C-C-C in-plane bending modes, respectively. 36,37 Compared to the peak intensities between different substrates, signicantly, the highest Raman peak intensities can be clearly observed for the Ag 40 nm/SiO 2 2 nm/Ag 40 nm arrays (Fig. 5c).…”