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Herein, a transparent and reproducible substrate, fabricated using polydimethylsiloxane (PDMS) laminated with self-assembled Ag nanoparticles (Ag NPs), was employed as a universal surface-enhanced Raman scattering (SERS) substrate for the detection of targets with various matrices. The Ag NPs were assembled in a two-dimensional manner via a self-assembly technique. Due to the electrostatic interaction between the Ag NPs, the reproducibility of the assembly was ensured by the fixed density of the assembled Ag NPs at saturated assembly states. The assembled pattern and plasmon resonance of the Ag NPs were well preserved during the molding and curing of PDMS. As a result, the Ag NP laminated PDMS film exhibited a SERS effect to the adsorbed p-aminothiophenol comparable to that of the assembled Ag NPs on a glass slide. Extra SERS enhancement was achieved by construction of a Ag (PDMS)/molecule/Ag (glass) configuration due to the electromagnetic coupling between the Ag NPs. The Raman scattering of 4-mercaptobenzoic acid and benzotriazole modified on the surfaces of a smooth Au electrode and copper foil, respectively, was detected with the aid of the Ag NP-laminated PDMS film. Furthermore, malachite green dispersed in a KBr solid matrix was quantitatively determined with a detection limit of 0.5 μg/g. It is suggested that the SERS enhancement and consequential SERS detection sensitivity of the target molecules may be further maximized by adjusting the distance between the target molecules and the Ag NPs laminated on the PDMS film. [ABSTRACT FROM AUTHOR]

We show that tris base (TB), a widely used buffer substance, can act as a reducing agent to synthesize multi-branched gold nanoparticles (mb-AuNPs) from tetrachloroauric acid in a one-step process. The method is simple, fast, and inexpensive and produces mb-AuNPs that are virtually monodisperse, have a size of about 90 nm and typically >6 branches. Their UV-vis absorption peaks can be fine-tuned from the visible to the near-infrared (NIR) region by controlling the concentration of TB. The mb-AuNPs represent an efficient substrate for surface-enhanced Raman scattering (SERS), with an enhancement factor of 1.2 × 10. They were applied as substrates for SERS-based imaging of kidney cells. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple method to remove PVP for high performance and reusable SERS substrate. • Cleaned AgNPs interface effectively enhanced the plasma resonance of the local surface (LSPR). • Residual PVP has basically no influence on detection of the molecular which absorbed stronger than PVP. The silver nanoparticles have been frequently used in SERS detection, for their unique optical properties and sensitive surface Raman enhancement properties. However, as the preparation of silver nanoparticles will use polyvinylpyrrolidone (PVP) to achieve the effect of reducing agent and surfactant, the surface of the prepared silver nanoparticles will be wrapped by PVP, forming an insulating layer and an ill-defined AgNPs interface, which limits the plasmonic coupling between the laminates of AgNPs. This paper reported a simple method to remove PVP for high performance and reusable SERS substrate, and the residue of PVP was studied after clean centrifugal by ethanol or water. When the number of cleaning times reached 10, there was basically no residual of PVP. The cleaned AgNPs interface effectively enhanced the plasma resonance of the local surface (LSPR) and greatly improved the SERS activity of the substrate. Moreover, probe molecules (R6G) are introduced to study the influence of single molecule PVP on subsequent detection. Through the competitive relationship between the two, it can be concluded that residual PVP has basically no influence on detection of the molecular which absorbed stronger than PVP, and the remaining PVP can be ignored. [ABSTRACT FROM AUTHOR]

• AgNPs/MIL-101(Fe) nanocomposites is used as a Raman enhanced substrate to detect R6G. The results show that the substrate has better stability and uniformity. Its R6G Raman assignment peak position RSD = 7.55%, enhancement factor EF = 2.09 × 109. • AgNPs/MIL-101(Fe) nanocomposites as a Raman enhanced substrate can detect the lowest concentration of paraquat at 10−12 mol/L, and the Raman signal is relatively stable in different acid-base environments. Recently, in the research of Surface-enhanced Raman scattering (SERS) technology, it is found that the preparation of enhanced substrate is particularly important. In this work, the most commonly used methods were used to synthesize AgNPs and MIL-101(Fe), and AgNPs/MIL-101(Fe) nanocomposite was obtained through self-assembly of the two substances. Four different probe molecules were detected with the self-assembled substrate and compared with the results of same probe molecules with AgNPs and MIL-101(Fe) as SERS substrate separately, it was found that AgNPs/ MIL-101 (Fe) nanocomposites had a strong enhancing effect as SERS substrate. The Enhancement Factor (EF) value of 10−6 mol/L Rhodamine 6G (R6G) was calculated as 2.09 × 109, and the Raman intensities of the peak relative standard deviation (RSD) of R6G Raman attribution was calculated as 7.55%. The time stability of the material was studied and it was found that the reduced Raman signal and poor reproducibility were due to the AgNPs placement time. AgNPs/ MIL-101 (Fe) nanocomposites were used as SERS substrate to detect Paraquat with a minimum concentration of 10−12 mol/L. The signal values of Paraquat Raman detected at 10−6 mol/L in different pH environments were relatively stable. [ABSTRACT FROM AUTHOR]