Supplementary Materialsao8b01153_si_001. method, as the Raman transmission could be dramatically improved just as much as 1010 to 1011 situations in a few plasmonic nanostructure,4 that allows to detect also a unitary molecule.4?7 Weighed against the conventional methods such as for example fluorescence, electrochemistry, and high-functionality liquid chromatography, SERS keeps significant advantages.8?12 For instance, higher quality on multiplex samples seeing that SERS provides fingerprint signatures of analytes endowing with better anti-interference level of resistance. Generally, SERS improvement is certainly ascribed to electromagnetic and chemical substance improvement, and the previous contributes to the majority of SERS improvement. The electromagnetic improvement is certainly localized at the hotspots caused by the coupling of the localized surface area plasmon resonance (LSPR) on the top or in the junctions of plasmonic nanoparticles.13?16 Optimizing the framework of plasmonic nanoparticles including size, form, surface area morphology, and composition is important in enhancing the reproducibility and sensitivity of SERS assays. The normal approach is by using the mark molecule to induce the aggregation of nanoparticles forming numerous hotspots in alternative.8,17 However, complications still remain because of the random and poor reproducibility of the hotspots, leading to insufficient quantitative SERS data and wide distribution of improvement factors.13 Furthermore, the operational and instrumental factors likewise have a profound impact on the Raman transmission.17 Therefore, to date, buy Iressa it really is still an excellent challenge to understand quantitative SERS analysis.18?20 In previous research, researchers have attemptedto use internal criteria to attain sensitivity and reproducibility simultaneously.21?26 However, the inner standard molecules buy Iressa could be influenced by the microenvironment of the answer and compete for the top adsorption, resulting in the fluctuation of the strength and frequency.1,27,28 Lately, a fresh structure predicated on coreCmoleculeCshell nanoparticles provides captured great attention.4,29,30 The inside gap between your core and the shell provides controllable hotspots and uniformity for SERS enhancement.4,31 The Raman molecules inside the gap could generate a highly stable, strong, and quantitative SERS signal. In particular, DNA, polymer-functionalized spherical Au nanoparticles, and galvanic replacement reaction have been reported to synthesize these nanostructures with nanometer interior gaps, exhibiting strong and stable SERS signals.4,29,30,32,33 For example, it was shown that galvanic alternative reaction between silver and gold facilitates the formation of gold nanorods (GNRs) with uniform interior nanogaps with a stable, strong, and reproducible SERS signals.32 Other methods such as small molecule-interlayered plasmonic structure and SiO2 interlayered gold structures also have Gpr20 been used to synthesize nanostructures with interior gaps.34?36 The standard molecule inside the gap between the core and shell was in a safe environment without perturbation from outside, and the surface of the shell was free without competitive adsorption. However, for these structures, they still have some shortcomings, such as laborious synthetic methods and long planning times. More importantly, all of these structures reported so far have smooth surfaces. It has been demonstrated that the most important element affecting SERS intensity is the shape of the nanoparticles.37 The designs with tips and edges can localize the plasmonic near field and create hotspots around the edges.38?40 The plasmonic nanostructures with more tips and edges will provide higher sensitivity in SERS analysis.41,42 Up to now, there has been no method to synthesize such spiked plasmonic nanorods with an interior gap, without the need to use DNA templates, for direct quantitative SERS analysis. Herein, an efficient method to prepare plasmonic substrates with spiked surfaces and interior gaps by employing a polydopamine internal shell is definitely reported. This structure is very reliable and suitable for quantitative SERS analysis, as the spiked surface provides a higher surface enhancement in a variety of samples. We used 4-mercaptopyridine (4-mp) as an internal standard in the nanogap (Scheme 1). This is a label-free method with high sensitivity and was successfully tested to detect polycyclic aromatic hydrocarbons (PAHs) quantitatively. The limit of detection is definitely up to 0.3 M. Finite-difference time-domain (FDTD) simulation is also used to confirm these results. Open in a separate window Scheme 1 Schematic Illustration of the Synthesis buy Iressa of the Plasmonic CoreCShell Structure, Based on GNRs, for Quantitative SERS Analysis.