Au–Ag Nanoparticles with Controllable Morphologies for the Surface-Enhanced Raman Scattering Detection of Trace Thiram

Surface enhanced Raman scattering (SERS) is a technique that utilizes the surface electric field of metal nanostructures to amplify Raman signals and promote the analysis and detection of trace molecules. In order to harness the potential of flexible SERS substrates, this work proposes a simple and cost-effective method for preparing a large-area (circular, 7.5 cm in diameter, with a 38 cm 2 area) three-dimensional (3D) flexible SERS substrate. We first prepared a bowl-shaped nanoarray of polydimethylsiloxane (PDMS) by utilizing a polystyrene microsphere (PS) as sacrificial templates and then loaded a monolayer of gold nanoparticles (AuNPs) on it, finally a high-strength 3D AuNPs/PDMS flexible SERS substrate is obtained successfully. There are two key steps here, which are using plasma etching to regulate the gap between PS spheres and using the thermal demolding method to facilitate the separation of PS and PDMS. The ultralarge area AuNPs/PDMS substrate exhibits high SERS detection sensitivity and good uniformity. The SERS substrate possesses the advantage of multifunctional detection. The proposed substrate demonstrated detections of up to 10 −9 , 10 −7 , and 10 −8 M concentrations of rhodamine 6G (R6G), vitamin C, and thiram molecules, respectively. The detection results meet international standards. Electromagnetic simulations using the finite difference time domain reveal that the SERS enhancement originates from the surface plasmon resonance and coupling effects of AuNPs. This large-area 3D flexible SERS substrate not only enhances detection efficiency by enabling the detection of a greater number of samples or sample regions but also provides a new approach for detecting vitamin C and pesticide residues. It may also be used in electronic skin sensors, in situ pesticide residue detection, on-scene evidence collection in criminal investigations, and so on.

Section: Resultssupporting

confidence: 79%

Flexible Large-Area Surface Enhanced Raman Scattering Substrate Based on Bowl-Shaped Arrays of Au Nanoparticles on PDMS

Mi,

Yuan,

Hao

et al. 2024

“…The surface-enhanced Raman substrate is a prime example in the field of functional materials fabrication. Surface-enhanced Raman spectroscopy (SERS) is a technique that enhances the Raman scattering signals of target molecules on specially prepared noble metal substrates, mainly Au and Ag. − The surface enhancement effect, high sensitivity, real-time performance, and nondestructive nature of SERS technology make it an effective TNT detection method. , Nowadays, various methods utilizing SERS technology have been developed for TNT detection. Researchers have created SERS substrates using 2D materials and precious metal particle composites by the in situ growth of Au nanoclusters on MG fibers .…”

Section: Introductionmentioning

confidence: 99%

Meso-Au/BN Nanosensor for Trinitrotoluene Based on Fluorescence Resonance Energy Transfer and Surface-Enhanced Raman Spectroscopy Mechanisms

Wang,

Xiang,

Ren

et al. 2024

It is a considerable challenge to develop surface-enhanced Raman spectroscopy sensors with high sensitivity but a lack of selective recognition performance for target species in the applied field. Here, a strategy for fabricating a meso-Au/BN nanoparticle (NP) sensor through a synthesized mesoporous Au NPs' surface modified by BN quantum dots (QDs) and 2-mercaptoethylamine (MEA) through electrostatic attraction and covalent bonding between a sulfur atom in the thiol group and an Au atom, respectively, was implemented to selectively recognize and sensitively detect 2,4,6-trinitrotoluene (TNT). TNT interacted with MEA on the meso-Au NP surface to form a TNT−MEA complex through the electrostatic affinity interaction between the electron-deficient nitro groups and the electron-rich amino group at the fluorescence-tagged sites, approaching the BN QDs on the meso-Au NPs' surface at spatial proximity, leading to the suppression of the fluorescence intensity of BN QDs via the fluorescence resonance energy transfer mechanism, forming the selective recognition of TNT. Additionally, the meso-Au/BN NP sensor enhanced the Raman signal of TNT by the localized surface plasmon resonance hotspots of the meso-Au NP surface, achieving highly sensitive detection of TNT. The limit of detection for TNT was 10 −9 mol•L −1 . Comparing TNT, 2,4-dinitrotoluene, 2,4,6-trinitrophenol, and 2,4-dinitrophenol, the meso-Au/BN NP sensor exhibited much more selective recognition and sensitive detection of TNT than other aromatic compounds. The method can be widely applied in the selective recognition and trace detection of biological molecules, metal ions, and organic pollutants.

“…Consequently, the design of metal nanocrystals capable of generating intense EM fields is of paramount importance. The plasmon-induced EM enhancement of these metal nanocrystals is significantly influenced by their shape, size, and morphology. − Many types of metal structures have been synthesized to facilitate efficient SERS detection, encompassing nanosphere, nanorods, nanotriangles, nanowire, and so on. − However, the high EM field intensity of these metal nanocrystals is predominantly located at the high-curvature surface due to the lightning rod effect; many flat surfaces on this structure have limited EM enhancement under light excitation, thereby leading to low SERS efficiency. Many efficient means have been proposed to optimize the EM enhancement of metal structures, including the growth of metal nanoparticles with rough surface, − the fabrication of branched gold nanostars, − and the construction of multilayered and hollow structures. , These approaches offer valuable insights for the design of metal nanocrystals with substantial EM enhancement and enhanced SERS sensitivity.…”

Section: Introductionmentioning

confidence: 99%

Uniform and Dense Hotspots in Au Rough-Nanocube Monolayer for Sensitive and Reproducible SERS Detection

Zhou,

Liu,

Yao

et al. 2024

Plasmonic metal nanocrystals show great potential in surface-enhanced Raman spectroscopy (SERS) detection. However, the fabrication of metal substrates with uniform and dense hotspots for sensitive and reproducible SERS remains a challenge. This study demonstrates a steerable approach to prepare a monolayer composed of Au rough nanocubes (RNCs) derived from Au nanocubes (NCs), which exhibits efficient and reproducible SERS activity for detecting organic pollutants and pesticide residues. The structure-adjustable Au RNCs are prepared by growing Au nanoparticles on Au NCs via a PbS-assisted surface modification. The as-prepared Au RNCs show better SERS activity on detecting dye molecules compared to the initial Au NCs. This improvement is attributed to the dense hotspots generated by the plasmon coupling between the Au NCs and the Au nanoparticles. Subsequently, a uniform Au RNC monolayer is fabricated using an interfacial self-assembly method, thereby exhibiting further improved SERS activity due to the electromagnetic enhancement between the adjacent nanoparticles. The Au RNC monolayer has excellent signal reproducibility with a relative standard deviation of 4.13% on detecting crystal violet owing to the large-area and uniform hotspots. Additionally, the Au RNC monolayer demonstrates excellent SERS efficiency in detecting residual thiram on fruits (10 −11 M, analytical enhancement factor of 1.24 × 10 8 at 1371 cm −1 ), melamine in milk, and dye in wastewater. These capabilities demonstrate the immense potential of the Au RNC monolayer for applications in food safety and environmental monitoring.