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Bimetallic Core Shelled Nanoparticles (Au@AgNPs) for Rapid Detection of Thiram and Dicyandiamide Contaminants in Liquid Milk Using SERS
摘要： Existing methods for contaminants detection in liquid milk are complex, requires chemicals and time-consuming experimental procedure. In this study, SERS based on bimetallic core shelled nanoparticles was employed for simultaneous and fast detection of thiram and dicyandiamide (DCD) in the milk. Spectra ranging from 400 to 1700 cm-1 were selected to examine thiram (0.5, 1, 2, 5 and 10 ppm) and DCD (20, 40, 80,160 and 320 ppm), by employing 28 nm gold cores and silver-shell thickness of 8 nm. A strong peak at 1379 cm-1 was ascribed to thiram with LOD of 0.21 ppm and R2 of 0.9896, whereas a band at 929 cm-1 was associated with DCD, delivering LOD of 14.88 ppm and R2 of 0.9956. The proposed method could achieve results within 34 min and this ecofriendly method can be further employed for simultaneous and rapid screening of other accidental contaminants in milk.
关键词： SERS,dicyandiamide,milk adulteration,thiram
更新于2025-09-23 15:19:57
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Silver nanosol SERS quantitative analysis of ultratrace biotin coupled N-doped carbon dots catalytic amplification with affinity reaction
摘要： Highly catalytic and stable N-doped carbon dots (N-CDs) were prepared rapidly by microwave procedure using glucose as precursor and ammonium sulfite as N-dopant. The reduction of AgNO3 by trisodium citrate (TCA) was slow to form nanosilver (AgNP), and the N-CDs exhibited strong catalysis of the AgNP reaction. The formed AgNPs were used as indicator in the presence of Vitoria blue B (VBB) molecule probe with a SERS peak at 1615 cm?1. With the increase of nanocatalyst N-CDs concentration, the AgNP reaction speed up, and the SERS peak of VBB enhanced linearly due to formation of more AgNPs as substrate. In the presence of avidin (Ad), the SERS peak weakened. Upon addition of biotin, the SERS peak enhanced due to turn on the indicator nanoreaction. The enhanced SERS signal had a good linear relationship with the biotin concentration in range of 0.0006–0.021 ng/mL, with a detection limit of 0.3 pg/mL.
关键词： Nanocatalysis,N-doped carbon dots,SERS,Affinity reaction,Biotin
更新于2025-09-23 15:19:57
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Signal amplification and quantification on lateral flow assays by laser excitation of plasmonic nanomaterials
摘要： Lateral flow assay (LFA) has become one of the most widely used point-of-care diagnostic methods due to its simplicity and low cost. While easy to use, LFA suffers from its low sensitivity and poor quantification, which largely limits its applications for early disease diagnosis and requires further testing to eliminate false-negative results. Over the past decade, signal enhancement strategies that took advantage of the laser excitation of plasmonic nanomaterials have pushed down the detection limit and enabled quantification of analytes. Significantly, these methods amplify the signal based on the current LFA design without modification. This review highlights these strategies of signal enhancement for LFA including surface enhanced Raman scattering (SERS), photothermal and photoacoustic methods. Perspectives on the rational design of the reader systems are provided. Future translation of the research toward clinical applications is also discussed.
关键词： gold nanoparticles,lateral flow assay,nanoparticle heating,signal amplification and quantification,SERS
更新于2025-09-23 15:19:57
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Plasmonic Coupling of AgNPs near Graphene Edges: A Cross-Section Strategy for High-Performance SERS Sensing
摘要： Fully exploiting plasmonic coupling of nanostructured metals is an effective method to promote surface-enhanced Raman scattering (SERS) performance for trace detection of molecules. Herein, we propose a cross-section strategy to maximize plasmonic coupling of silver nanoparticles (AgNPs) in graphene-based membrane. Specifically, AgNPs are isolated by water-dispersible graphene (W-Gr) and enriched in the vicinity of W-Gr edges when assembling into a macroscopic membrane, thus affording AgNPs on the cross section with uniform and proper gaps in the vertical plane to generate maximal plasmon coupling. Moreover, the superior sensitivity (5×10-13 M for R6G) to most reported graphene-metal structures and the long-term stability against aerobic oxidation jointly make the cross-section of AgNPs/W-Gr membrane a potential SERS substrate for trace-molecule detection. The revealed mechanism for AgNPs enrichment near edges highlights the importance of flow-directed assembly process of W-Gr. This work provides new insight into the interpretation and utilization of two-dimensional materials as building blocks in high-performance SERS sensing.
关键词： Cross-section strategy,AgNPs,SERS sensing,Plasmonic coupling,Graphene edges
更新于2025-09-23 15:19:57
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Sculpting Artificial Edges in Monolayer MoS <sub/>2</sub> for Controlled Formation of Surface-Enhanced Raman Hotspots
摘要： Hotspot engineering has the potential to transform the field of Surface-Enhanced Raman Spectroscopy (SERS) by enabling ultra-sensitive and reproducible detection of analytes. However, the ability to controllably generate SERS hotspots, with desired location and geometry, over large-area substrates, has remained elusive. In this study, we sculpt artificial edges in monolayer Molybdenum Disulfide (MoS2) by low-power focused laser-cutting. We find that when gold nanoparticles (AuNPs) are deposited on MoS2 by drop-casting, the AuNPs tend to accumulate predominantly along the artificial edges. First-principles density functional theory (DFT) calculations indicate strong binding of AuNPs with the artificial edges due to dangling bonds that are ubiquitous on the un-passivated (laser-cut) edges. The dense accumulation of AuNPs along the artificial edges intensifies plasmonic effects in these regions creating hot spots exclusively along the artificial edges. DFT further indicates that adsorption of AuNPs along the artificial edges prompts a transition from semiconducting to metallic behavior, which can further intensify the plasmonic effect along the artificial edges. These effects are observed exclusively for the sculpted (i.e., cut) edges and not observed for the MoS2 surface (away from the cut edges) or along the natural (passivated) edges of the MoS2 sheet. To demonstrate the practical utility of this concept, we use our substrate to detect Rhodamine B (RhB) with large SERS enhancement (~104) at the hotspots for RhB concentrations as low as ~10-10 M. The single-step laser etching process reported here can be used to controllably generate arrays of SERS hotspots. As such, this concept offers several advantages over previously reported SERS substrates that rely on electro-chemical deposition, e-beam lithography, nanoimprinting or photolithography. While we have focused our study on MoS2, this concept could in principle, be extended to a variety of 2D material platforms.
关键词： focused laser irradiation,MoS2,localized hotspots,artificial edges,SERS
更新于2025-09-23 15:19:57
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Ultrathin Hexagonal PbO Nanosheets Induced by Laser Ablation in Water for Chemically Trapping Surface-Enhanced Raman Spectroscopy Chips and Detection of Trace Gaseous H <sub/>2</sub> S
摘要： Lead oxide (PbO) nanosheets are of significance in design of functional devices. However, facile, green and fast fabrication of ultrathin and homogenous PbO nanosheets with chemically clean surface is still desirable. Herein, a simple and chemically clean route is developed for fabricating such nanosheets via laser ablation of a lead target in water for a short time and then ambient ageing. The obtained PbO nanosheets are (002)-oriented with microsize in planar dimension and ca. 15 nm in thickness. They are mostly hexagonal in shape. Experimental observations of the morphological evolution have revealed that the formation of such PbO nanosheets can be attributed to two processes: (i) laser ablation-induced formation of ultrafine Pb and PbO nanoparticles (NPs); (ii) PbO NPs’ aggregation and their oriented connection growth. Importantly, a composite surface enhanced Raman spectroscopy (SERS) chip is designed and fabricated, by covering a PbO nanosheets’ monolayer on a Au NPs’ film. Such composite SERS chip can be used for the fast and trace detection of gaseous H2S, in which the PbO nanosheets can effectively chemically trap H2S molecules, demonstrating a new application of these PbO nanosheets. The response of this chip to H2S can be detected within 10s and the detection limit is below 1 ppb. Also, this PbO nanosheet-based chip is reusable by heating after use. This study not only deepens understanding the NPs-based formation mechanism of nanosheets, but also provides the renewable SERS-chips for the highly efficient detection of trace gaseous H2S.
关键词： Ultrathin hexagonal PbO nanosheets,Chemically trapping-SERS chip,Trace detection of gaseous H2S,Reusable performance,Laser ablation in water
更新于2025-09-23 15:19:57
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Effects on surface-enhanced Raman scattering from copper nanoparticles synthesized by laser ablation
摘要： In this work, we report the synthesis of Cu nanoparticles (NPs) by laser ablation technique using 532 nm and 1064 nm wavelength in ethylene glycol. The optical and morphological studies of as-prepared NP colloids were characterized using UV–Visible absorption , photoluminescence spectrometers and transmission electron microscope (TEM) techniques. Cu NPs synthesized at 532 nm and 1064 nm were spherical with an average size of 3.2 ± 0.1 nm and 4.3 ± 0.1 nm respectively. Furthermore, surface-enhanced Raman scattering (SERS) studies were performed on methylene blue (MB) using Cu NPs as SERS platform. In addition, the effects of size, shape and localized surface plasmon resonance (LSPR) of Cu NPs as well as the Raman excitation wavelength used for SERS measurement were investigated and discussed to give insight into the factors affecting their SERS enhancement factor.
关键词： enhancement factor,SERS,optical properties,Cu NPs
更新于2025-09-23 15:19:57
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Photochemical Synthesis of Silver Nanodecahedrons under Blue LED Irradiation and Their SERS Activity
摘要： Silver nanodecahedrons were successfully synthesized by a photochemical method under irradiation of blue light-emitting diodes (LEDs). The formation of silver nanodecahedrons at different LED irradiation times (0–72 h) was thoroughly investigated by employing different characterization methods such as ultraviolet–visible spectroscopy (UV–Vis), transmission electron microscopy (TEM), and Raman spectroscopy. The results showed that silver nanodecahedrons (AgNDs) were formed from silver nanoseeds after 6 h of LED irradiation. The surface-enhanced Raman scattering (SERS) effects of the synthesized AgNDs were also studied in comparison with those of spherical silver nanoparticles in the detection of 4-mercapto benzoic acid. Silver nanodecahedrons with a size of 48 nm formed after 48 h of LED irradiation displayed stronger SERS properties than spherical nanoparticles because of electromagnetic enhancement. The formation mechanism of silver nanodecahedrons is also reported in our study. The results showed that multihedral silver nanoseeds favored the formation of silver nanodecahedrons.
关键词： LEDs,photochemical synthesis,SERS,silver nanodecahedron
更新于2025-09-23 15:19:57
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Actuated plasmonic nanohole arrays for sensing and optical spectroscopy applications
摘要： Herein, we report a new approach to rapidly actuate the plasmonic characteristics of thin gold films perforated with nanohole arrays that are coupled with arrays of gold nanoparticles. The near-field interaction between the localized and propagating surface plasmon modes supported by the structure was actively modulated by changing the distance between the nanoholes and nanoparticles and varying the refractive index symmetry of the structure. This approach was applied by using a thin responsive hydrogel cushion, which swelled and collapsed by a temperature stimulus. The detailed experimental study of the changes and interplay of localized and propagating surface plasmons was complemented by numerical simulations. We demonstrate that the interrogation and excitation of the optical resonance to these modes allow the label-free SPR observation of the binding of biomolecules, and is applicable for in situ SERS studies of low molecular weight molecules attached in the gap between the nanoholes and nanoparticles.
关键词： gold nanoparticles,responsive hydrogel,plasmonic nanohole arrays,surface plasmon resonance,SERS
更新于2025-09-23 15:19:57
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Metallic Core-Shell Photonic Crystals for Surface-Enhanced Raman Scattering (SERS)
摘要： Metallic core-shell substrate is specially used to serve ultrasensitive molecular detection down to concentration of micromolar level based on surface-enhanced Raman spectroscopy (SERS). Calculations show that the amorphous poly(methyl methacrylate) (PMMA) photonic crystals incorporated with metal nanoparticles which is either gold or silver nanoparticles can significantly increase the electromagnetic fields at the air dielectric interface, leading to remarkable Raman enhancement. Corresponding experiments and characterizations show the characteristic and performance of core-shell structures which present an excellent sensitivity, reproducibility and stability to act as SERS substrate.
关键词： Silver nanoparticles,Electromagnetic field,Poly(methyl methacrylate),SERS,Gold nanoparticles,Core-shell
更新于2025-09-23 15:19:57