Au‐Nanoparticle‐Array/Aligned‐Ag‐Nanowire‐Based Flexible Dual Plasmonic Substrate for Sensitive Surface‐Enhanced Raman Scattering Detection

Abstract

The hot spot density is increased with the result that the Raman signals of molecules absorbed on the noble metallic nanostructures can be significantly enhanced. The noble metal Ag is an ideal candidate for electromagnetic enhancement in SERS because of its excellent SPR. However, the low stability of Ag is the largest challenge for electromagnetic enhancement, as it can be easily oxidized upon exposure to air, which reduces the detection limit of SERS. The noble metal Au exhibits a high stability and good biocompatibility although its SERS activity is inferior to that of Ag. [7] Thus, dual plasmonic structures combined with Ag and Au as SERS substrates are expected to improve the stability and sensitivity of SERS.Generally, dual plasmonic structures combined with Ag and Au are achieved by the galvanic replacement reaction of Ag with Au 3+ . The random distribution and inconsistent size of Au nanoparticles (AuNPs) on the Ag surface hinder the control of the adjacent gap. As a result, their SERS sensitivity is not effectively improved. In particular, the AuNPs on the surface of Ag nanowires (AgNWs) obtained by the galvanic replacement reaction weaken the propagating surface plasmon resonance (PSPR) effect of AgNWs, which is unfavorable for a high SERS sensitivity. [8] When rigid dual plasmonic SERS substrates are applied on uneven and irregular detecting surfaces, the dual plasmonic structures are destroyed, leading to decreased SERS sensitivity and reproducibility. By contrast, dual plasmonic structures incorporated into flexible substrates have excellent mechanical properties, antidamage characteristic, portability, and tailorability, which enable the detection of target molecules on an uneven and irregular surface. [9] Therefore, the development of strategies for the fabrication of dual plasmonic structures and introduction of flexible substrates are important for the development of sensitive and reproducible SERS detection.In this study, we demonstrate a flexible dual plasmonic SERS (FDPS) substrate with high SERS sensitivity and reproducibility, which is composed of aligned AgNWs and AuNP arrays separated by a thin polyurethane (PU) layer. The FDPS substrate achieved a high SERS activity with a detection limitThe fabrication of flexible surface-enhanced Raman scattering (SERS) substrates for sensitive detection on uneven or irregular surfaces is challenging. In this study, a flexible dual plasmonic SERS (FDPS) substrate rationally constructed using Au nanoparticle (AuNP) arrays/aligned Ag nanowires (AgNWs) and elastic polyurethane (PU) is demonstrated. It exhibits high sensitivity (detection limit of 10 −8 m for melamine and 10 −10 m for malachite green) and excellent reproducibility. The well-designed structure of AuNP arrays/aligned AgNWs fabricated using block copolymer self-assembly and oil-water-air interfacial self-assembly successfully enhances the electromagnetic field through plasmonic coupling. In addition, the FDPS substrate retains a high SERS sensitivity after exposure to air at room temperat...

Flexible and Highly Sensitive Sandwich-Structured PDMS with Silver Nanowires and Laser-Induced Graphene for Rapid Residue Detection

“…Furthermore, the unwrapped Ag NWs@PDMS only relied on the adhesion of the PDMS layer to maintain the Ag layer, and the surface layer was easily damaged and wrinkled (Figure S2C). Compared with the Ag NW-based SERS substrates reported in the current literature (Table ), the sandwich-structured Ag NWs@LIG@PDMS had a detection limit far superior to those reports in most literature. − , Figure S5 shows the SERS spectrum of 10 –6 M R6G adsorbed on Ag NWs@LIG@PDMS and the Raman spectrum of 10 –2 M R6G aqueous solution. So the commonly used enhancement factor (EF) value was obtained as 9.96 × 10 6 through the detailed calculation of Supporting Information S1 .…”

“…So the commonly used enhancement factor (EF) value was obtained as 9.96 × 10 6 through the detailed calculation of Supporting Information S1 . Compared with other literature, the prepared substrate has relatively high enhancement factors. − , …”

Recent Development and Applications of Stretchable SERS Substrates

“…The membrane substrate exhibits high sensitivity, high enhancement factor (2.03 × 10 9 ), low detection limit (3.41 × 10 −11 M), and superior multi-detection capabilities including good homogeneity and reproducibility (<7.32%). Tang et al [116] constructed a flexible dual-plasma SERS substrate for the detection of residuals of triclosan in food samples. Due to the enhanced electromagnetic field from the plasma coupling of the AuNP arrays and aligned AgNWs, the substrate exhibits good sensitivity and reproducibility in a variety of situations, including 100 cycles of stretching, bending, and twisting, with a detection limit for melamine as low as 10 −8 M. From the above examples, one can see that stretchable SERS substrates have been powerful tools in monitoring the misuse of food additives or illegal additions, especially where non-destructive, real-time, and in situ detection is needed.…”