Abstract
The recent development of SERS substrates based on irregular nanostructures for directly molecule recognition has aroused increasing attention. By combining the irregular flake-like nanostructures of mantis wings, high SERS performance of Ag nanofilms, and the chemical stability of Au nanoparticles (NPs), an ultra-sensitive and flexible SERS substrate based on Au NPs functionalized Ag nanofilms-mantis wings (Au-Ag-M.w.) hybrid system is successfully fabricated. When 4-aminothiophenol is selected as the probe molecule, the limit of detection (LOD) is as low as 10−13 M and the relative standard deviation (RSD) is lower than 7.15%. This novel SERS platform exhibits high SERS performance in terms of sensitivity, reproducibility and practicability mainly because there are high-density and multi-level “hot spots” in the appropriate nanogaps. Meanwhile, it also systematically compares the differences of the SERS performance of Cu and Ag decorated M.w. hybrids and how these differences can alter their response. Moreover, the proposed substrate is employed to rapidly detect the pesticide residues on apple peels and the LOD for cypermethrin is estimated at 10−10 mg/mL. Therefore, this novel SERS substrate has great potential in rapid sampling of pesticide residues on real samples and expands the investigation to other natural materials for fabricating various SERS platforms.
Highlights
Raman scattering spectroscopy is a rapid, nondestructive and qualitative analysis tool which can provide vibrational and rotational information of a molecule [1]
One is chemical enhancement (CM), and this enhancement mechanism is mainly based on the transfer effect of dynamic charge between the analytes and plasmonic nanostructures [8]; the other, electromagnetic enhancement mechanism (EM), originating from the sharp increase of local electromagnetic field at appropriate nanostructural junctions (“hot spots”) excited by localized surface plasmon resonance (LSPR), can provide Raman signal over several orders of magnitude higher than the CM [9]
The results revealed that high sensitivity (10−11 M for malachite green) and well reproducibility of Raman signals were due to the super-hydrophobicity and flexible surface
Summary
Raman scattering spectroscopy is a rapid, nondestructive and qualitative analysis tool which can provide vibrational and rotational information of a molecule [1]. Diverse technologies to achieve high-performance plasmonic nanoarrays have been reported, such as nanosphere lithography [21], electron-beam lithography [22], focused ion-beam lithography [23], laser direct writing [24], casting and solidification process [25] etc These nanostructures can provide abundant “hot spots” and excite a high LSPR effect, but the complex and time-consuming experimental processes, strict experimental conditions, low-throughput fabrication processes further limit the widespread application in real-life detection. In addition to high sensitivity, excellent Raman enhancement and super-hydrophobicity, these biomaterial-based SERS substrates possess another advantage in flexibility. They offer advantages over traditional rigid substrates in their flexibility and can sense analytes on the surface of non-planar geometries. The Au-Ag-M.w.-x described these Ag-M.w.-x substrates decorated with Au NPs
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