Surface-enhanced Raman Scattering Signal Intensity Research Articles

3D Surface-Enhanced Raman Scattering Substrate Based on an Array of Self-Assembled Au@SiO2 Microspheres

A quasi-periodic array of 3D gold-nanoparticle-capped SiO2 microspheres (Au@SiO2) was designed and prepared with a facile approach to enhance the Raman signal intensity of adsorbed biomolecules. Through adjusting the thickness and annealing of Au thin films initially deposited on arrays of self-assembled SiO2 microspheres, we were able to control the diameter of Au nanoparticles and their interparticle spacing to produce two types of plasmonic near-field hot spots, locating at the gaps of such densely arranged Au nanoparticles on individual SiO2 microspheres and in the gap regions of neighboring SiO2 microspheres, respectively. Such double near-field enhancement mechanism leads to a surface-enhanced Raman scattering (SERS) enhancement factor up to 3 × 106 for Rhodamine 6G molecules. The SERS signal intensity was highly uniform with a relative standard deviation of 4.5%. This 3D SERS substrate has significant potential for various applications in the field of SERS detection of analytes and wearable biosensing.

Reversible Thermoelectric Regulation of Electromagnetic and Chemical Enhancement for Rapid SERS Detection.

Actively controlling surface-enhanced Raman scattering (SERS) performance plays a vital role in highly sensitive detection or in situ monitoring. Nevertheless, it is still challenging to achieve further modulation of electromagnetic enhancement and chemical enhancement simultaneously in SERS detection. In this study, a silver nanocavity structure with graphene as a spacer layer is coupled with thermoelectric semiconductor P-type gallium nitride (GaN) to form an electric-field-induced SERS (E-SERS) for dual enhancement. After applying the electric field, the intensity of SERS signals is further enhanced by over 10 times. The thermoelectric field enables fast and reproducible doping of graphene, thereby modulating its Fermi level over a wide range. The thermoelectric field also regulates the position of the plasmon resonance peak of the silver nanocavity structure, rendering synchronous dual electromagnetic and chemical regulation. Additionally, the method enables the trace detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A detailed theoretical analysis is performed based on the experimental results and finite-element calculations, paving the way for the fabrication of high-efficient E-SERS substrates.

Enzyme-free sensitive SERS biosensor for the detection of thalassemia-associated microRNA-210 using a cascade dual-signal amplification strategy

Backgroundβ-thalassemia is a blood disorder caused by autosomal mutations. Gene modulation therapy to activate the γ-globin gene to induce fetal hemoglobin (HbF) synthesis has become a new option for the treatment of β-thalassemia. MicroRNA-210 (miR-210) contributes to studying the mechanism regulating γ-globin gene expression and is a potential biomarker for rapid β-thalassemia screening. Traditional miRNA detection methods perform well but necessitate complex and time-consuming miRNA sample processing. Therefore, the development of a sensitive, accurate, and simple miRNA level monitoring method is essential. ResultsWe have developed a non-enzymatic surface-enhanced Raman scattering (SERS) biosensor utilizing a signal cascade amplification of catalytic hairpin assembly reaction (CHA) and proximity hybridization-induced hybridization chain reaction (HCR). Au@Ag NPs were used as the SERS substrate, and methylene blue (MB)- modified DNA hairpins were used as the SERS tags. The SERS assay involved two stages: implementing the CHA-HCR cascade signal amplification strategy and conducting SERS measurements on the resulting product. The HCR was started by the products of target-triggered CHA, which formed lengthy nicked double-stranded DNA (dsDNA) on the Au@Ag NPs surface to which numerous SERS tags were attached, leading to a significant increase in the SERS signal intensity. High specificity and sensitivity for miR-210 detection was achieved by monitoring MB SERS intensity changes. The suggested SERS biosensor has a low detection limit of 5.13 fM and is capable of detecting miR-210 at concentration between 10 fM and 1.0 nM. SignificanceThe biosensor can detect miR-210 levels in the erythrocytes of β-thalassemia patients, enabling rapid screening for β-thalassemia and suggesting a novel approach for investigating the regulation mechanism of miR-210 on γ-globin gene expression. In the meantime, this innovative technique has the potential to detect additional miRNAs and to become an important tool for the early diagnosis of diseases and for biomedical research.

Quantitative Sensing of Domoic Acid from Shellfish Using Biological Photonic Crystal Enhanced SERS Substrates.

Frequent monitoring of sea food, especially shellfish samples, for the presence of biotoxins serves not only as a valuable strategy to mitigate adulteration associated health risks, but could also be used to develop predictive models to understand algal explosion and toxin trends. Periodic toxin assessment is often restricted due to poor sensitivity, multifarious cleaning/extraction protocols and high operational costs of conventional detection methods. Through this work, a simplistic approach to quantitatively assess the presence of a representative marine neurotoxin, Domoic acid (DA), from spiked water and crab meat samples is presented. DA sensing was performed based on surface-enhanced Raman scattering (SERS) using silver nanoparticle enriched diatomaceous earth—a biological photonic crystal material in nature. Distinctive optical features of the quasi-ordered pore patterns in diatom skeleton with sporadic yet uniform functionalization of silver nanoparticles act as excellent SERS substrates with improved DA signals. Different concentrations of DA were tested on the substrates with the lowest detectable concentration being 1 ppm that falls well below the regulatory DA levels in seafood (>20 ppm). All the measurements were rapid and were performed within a measurement time of 1 min. Utilizing the measurement results, a standard calibration curve between SERS signal intensity and DA concentration was developed. The calibration curve was later utilized to predict the DA concentration from spiked Dungeness crab meat samples. SERS based quantitative assessment was further complemented with principal component analysis and partial least square regression studies. The tested methodology aims to bring forth a sensitive yet simple, economical and an extraction free routine to assess biotoxin presence in sea food samples onsite.

Combining thin-film microextraction and surface enhanced Raman spectroscopy to sensitively detect thiram based on 3D silver nanonetworks

By coupling thin-film microextraction (TFME) with surface enhanced Raman scattering (SERS), a facile method was developed for the determination of thiram in the complex matrix (orange juice or grape peel). The substrate of TFME was made by self-assembling silver sol on the silicon wafer to form a three-dimensional (3D) silver nanonetwork structure, without adding any template, which was used for TFME and SERS detection, respectively. The substrate exhibits high reproducibility with a relative standard deviation of about 7.32 % in spot and spot SERS intensity. The SERS signal intensity at a shift of 1384 cm−1 and the thiram concentration showed good linearity in the range of 0.01–5 µg/L and the linear correlation coefficient was 0.9912. The detection limit for thiram was found to be 0.01 µg/L. The TFME-SERS method was applied for the determination of thiram in fruit juice and the results were obtained very well. Therefore, this method is expected to play a role in the detection of trace pollutants.

Electrochemically assisted wide area Raman with standard curved surface quantification method

Reproducibility is still a great challenge for surface-enhanced Raman scattering (SERS), because the uncontrollable fabrication of SERS substrates or the uneven distribution of samples on the substrate result in the signal fluctuation with or between the substrates. Herein, a novel SERS quantitative method with good reproducibility was proposed. It is based on the basic principle that the SERS signal intensity is not only related to electromagnetic enhancement and the concentration of sample, but also related to the specific surface area of the substrate. The surface area information of the substrate is obtained through electrochemical technology, and then introduced into the standard curve with the linear relationship of concentration of sample and SERS intensity as a new variable to obtain a 3D standard curved surface, which effectively corrects the signal difference between the substrates, and combines the wide area Raman method to reduce the difference within the substrate, thereby improving the reproducibility of SERS quantitative detection. Using malachite green (MG) as the probe molecule and using cyclic voltammetry to calculate the substrate area fitted plane model (CV-standard curved surface), the root mean square error (RMSE) of the predicted result is 0.26 and the relative error (RE) is 0.25. It shows that the detection error significantly reduces comparing with the traditional standard curve method. Also, the proposed method can be used in other SERS quantitative detection and has potential application prospects.

Surface-enhanced Raman scattering of DNA bases using frozen silver nanoparticle dispersion as a platform.

Raman spectroscopy is a powerful method to characterize molecules in various media. Although surface-enhanced Raman scattering (SERS) is often employed to compensate for the intrinsically poor sensitivity of Raman spectroscopy, there remain serious tasks, such as simple preparations of SERS substrates, sensitivity control, and reproducible measurements. Here, we propose freezing as an efficient way to overcome these problems in SERS measurements using DNA bases as model targets. Solutes are expelled from ice crystals and concentrated in the liquid phase upon freezing. Silver nanoparticles (AgNPs) are also concentrated in the liquid phase to aggregate with Raman target analytes. The SERS signal intensity is maximized when the AgNP concentration exceeds the critical aggregation value. Freezing allows up to 5000 times enhancements of the SERS signal. Thus, an efficient SERS platform is prepared by simple freezing. The simultaneous detection of four DNA bases effectively eliminates variations of signal intensities and allows the reliable determination of concentrationratios.

Determination of spectinomycin by SERS based on BSA-protected AgNPs decorated with α-CD

A surface-enhanced Raman scattering (SERS) spectroscopic method with good selectivity and high sensitivity for the determination of spectinomycin (SPT) was established based on silver nanoparticles (AgNPs) coated by bovine serum albumin (BSA) and decorated with α-cyclodextrin (α-CD). The SERS characteristic peak of SPT at 485 cm−1 was selected for quantity analysis and the enhancement factor (EF) of the detection system was 1.95 × 107. The synthesis of α-CD/Ag@BSA NPs substrate was characterized by ultraviolet visible (UV–vis) spectroscopy and transmission electron microscope (TEM). The interaction between the substrate and the drug was demonstrated by UV–vis and fourier transform infrared (FT-IR) spectroscopy, which provided a theoretical basis for the determination of SPT by SERS. The effects of experimental parameters such as α-CD/Ag@BSA NPs solution volume, NaCl volume and mixing time on SERS signal intensity were investigated. Under the optimum conditions, the determination of SPT by SERS performed a good linear relationship in the 3.33 – 1000.00 nmol L−1 concentration range for SPT (ISERS = 131.52c + 26585.53, c: nmol L−1, r = 0.996). Limit of detection (LOD) for SPT was 2.01 nmol L−1 (S/N = 3). The effects of various interfering ions and similar drug on the determination system were studied. The SERS method was successfully applied to the determination of SPT in beef and lamb samples. The relative standard deviation (RSD) of SPT in the samples was 2.27% – 4.82% (n = 5), with recovery 96.04% – 104.90%.

Research on the Raman properties of NiFe/cicada wing composite SERS platform modified by silver nanoparticles

Composite structures have been widely concerned in the preparation of surface enhanced Raman scattering (SERS) substrates. In this paper, by solving the problem that the magnetic material was difficult to glow in magnetron sputtering, ferro-nickel (NiFe) alloy was deposited on the cicada wing (CW) and the NiFe/CW substrate was obtained. The results of sliver nanoparticles (Ag NPs) modified on the substrate were subsequently compared, and the SERS properties of the new Ag/NiFe/CW substrate were analyzed. Obviously, the intensity of SERS signals has been greatly improved after the modification of Ag NPs, and the substrate exhibits excellent reproducibility. The Ag NPs modified substrates were also applied to the detection of toxic crystal violet (CV) solution, which showed remarkable SERS activity. It has been proved that the strategy of modifying Ag NPs on the substrate to form a composite structure has great potential for improving the SERS performance of the substrate.

“Signal-on” SERS sensing platform for highly sensitive and selective Pb2+ detection based on catalytic hairpin assembly

In this work, a surface-enhanced Raman scattering (SERS) sensing strategy was proposed for the analysis of lead ion (Pb2+) with high sensitivity and specificity based on the high specificity of the catalytic nucleic acids (DNAzymes) to Pb2+ and the catalytic hairpin assembly (CHA) amplification. First, the Pb2+-DNAzyme initiated the reaction by target Pb2+ and released a linear DNA (rS1). Second, the hairpin DNA 1 (H1) was immobilized on the SERS substrate surface via Ag–S bond. Then, the rS1 could cyclically trigger the allosteric effects of CHA amplification and the H1 was opened and then the R6G-labeled hairpin probe 2 (H2) hybridized with H1 to form H1–H2 double-stranded and the released rS1 could initiate the next cycle of CHA reaction. This process made the Raman tag of R6G close to the surface of SERS substrate, and the intensity of SERS signal from R6G labels increase with the increase of concentration of target Pb2+. Benefiting from outstanding performances of the Pb2+-specific DNAzymes and enzyme-free CHA amplification system, this biosensor exhibits good sensitivity for Pb2+ with a limit of detection of 0.42 pM. More importantly, this developed detection platform could be employed for reliable analysis of Pb2+ in real environment system.

Thermal degradation in edible oils by surface enhanced Raman spectroscopy calibrated with iodine values

We present a facile surface enhanced Raman scattering (SERS) based methodology to study the thermal degradation of edible oils using a special gold sputtered SERS tattoo. The methodology is calibrated with Iodine values, which is an industrial standard. This analytical study aims to compare the safety of 7 edible oils rich in monounsaturated (MU), polyunsaturated (PU), and saturated (S) fatty acids (FA) against high temperature re-cooking as done in most restaurants, and street food joints. The changes in the SERS signal intensity (I) ratio of the saturated (@1440 cm-1), and unsaturated (@ 1265 cm−1) FA, I1265/I1440, was studied as a function of heating time, and temperature (T), around the ‘smoke point’. The SERS marker for thermal degradation, I1265/I1440, measuring the normalized unsaturated FA content in the oils decreased consistently, and significantly for the PUFA, and MUFA oils when heated above the ‘smoke point’, following the changes in the industrial standard ‘Iodine value’. Olive (MUFA), and Coconut (SFA) oil showed marginal, and no decrease, respectively, of the SERS marker over the temperature range studied. Based on the SERS marker, a parameter ζ, -the decrease of (I1265/I1440) value of the heated oil with respect to the as-purchased value, is defined that can compare the degradation of the edible oils under different thermal stressing. The Arrhenius fit of the SERS marker yielded similar activation energy of the thermal degradation to that obtained independently from Iodine value, and demonstrates the correctness of the presented methodology.

Optical and Surface-Enhanced Raman Scattering Properties of Black and Metallic Silver Micro/Nano Structures Fabricated on Cicada Wings by Silver Mirror Reaction.

Silver was deposited on cicada (Cryptotympana facialis) wings to fabricate black and metallic silver micro/nano structures on the wings (black-Ag wings and metallic-Ag wings) by the silver mirror reaction. The transparent cicada wings with close-packed nanopillar array structures were used as the substrates based on natural materials. As the silver mirror reaction proceeded, the color of the wing gradually changed from transparent to brown, then to black, and finally to metallic silver. A thin Ag film coated nanopillar array structure is seen in the black-Ag wing. The transmittance and reflectance of the black-Ag wing were nearly 0% and an average of about 4% in the wavelength range of 200-800 nm, respectively. Densely stacked colloidal Ag particles with an average diameter of 155 nm were observed on the surface of the metallic-Ag wing. The surface enhanced Raman scattering (SERS) signal intensities of Rhodamine 6G (R6G) dripped and dried on the black-Ag wing, thin Ag film sputtered on glass slides, and metallic-Ag wing increased in that order. In particular, the SERS signal intensities of R6G on metallic-Ag wing were greater than two orders of magnitude than those on the black-Ag wing and thin Ag film.

Dispersive liquid-liquid microextraction coupled with surface enhanced Raman scattering for the rapid detection of sodium benzoate

Medicine safety has become a large concern and prompts an urgent need to develop a rapid, simple and sensitive analytical method, which can monitor excessive preservatives in medicine. In this work, dispersive liquid-liquid microextraction (DLLME) was combined with surface enhanced Raman scattering (SERS) for a quick analysis of a kind of preservatives, sodium benzoate, in ibuprofen oral solution. The experimental parameters affecting DLLME were systematically investigated. Under the optimal conditions, the whole procedure, including DLLME and the SERS analysis, could be carried out within 10 min. A good linearity between the concentration of sodium benzoate ranging from 10 to 500 mg L−1 and the SERS signal intensity could be obtained, and the correlation coefficient (R2) 0.9986. The method detection limit was 0.56 mg L−1. The relative standard deviation was less than 6.33% for ten replicates at the same sample concentrations. The analytical results prove that the method is suitable for rapid determination of sodium benzoate in ibuprofen oral samples.

Interactions between Silica-Coated Gold Nanorod Substrates and Hydrophobic Analytes in Colloidal Surface-Enhanced Raman Spectroscopy

Surface-enhanced Raman scattering (SERS)-based detection of suspension phase analytes holds great promise for a variety of applications; however, plasmonic colloidal SERS substrates are not stable in many solution conditions unless they are protected by a stabilizing shell. Mesoporous silica shells on plasmonic nanoparticle cores have been demonstrated to perform well in a variety of liquid matrices. However, this silica shell can be seen as barrier from the perspective of the analyte, as the analyte molecules need to reach the plasmonic core after they pass through the shell. In this work, mesoporous silica-coated gold nanorods have been synthesized and characterized as aqueous colloidal SERS substrates systematically considering how SERS performance is impacted by three different factors: adsorbed molecules, the silica shell, and bulk solvent media. The results show that SERS signal intensities from the model hydrophobic analyte, trans-1,2-bis(4-pyridyl) ethylene (BPE), is enhanced when the pore size, h...

Facile synthesis of Fe3O4@Au core–shell nanocomposite as a recyclable magnetic surface enhanced Raman scattering substrate for thiram detection

The Fe3O4@Au core–shell nanocomposites, as the multifunctional magnetic surface enhanced Raman scattering (SERS) substrates, were fabricated successfully by the seeds growth method based on the Fe3O4–Au core-satellite nanocomposites. The SERS properties of the Fe3O4–Au core-satellite nanocomposites and the Fe3O4@Au core–shell nanocomposites were compared using 4-aminothiophenol (4-ATP) as the probe molecule. It was found that Fe3O4@Au core–shell nanocomposites showed better SERS performance than Fe3O4–Au core-satellite nanocomposites. The Au shell provided an effectively large surface area for forming sufficient plasmonic hot spots and capturing target molecules. The integration of magnetic core and plasmonic Au nanocrystals endowed the Fe3O4@Au core–shell nanocomposites with highly efficient magnetic separation and enrichment ability and abundant interparticle hot spots. The Fe3O4@Au core–shell nanocomposites could be easily recycled because of the intrinsic magnetism of the Fe3O4 cores and had good reproducibility of the SERS signals. For practical application, the Fe3O4@Au core–shell nanocomposites were also used to detect thiram. There was a good linear relationship between the SERS signal intensity and the concentration of thiram from 1 × 10−3 to 1 × 10−8 M and the limit of detection was 7.69 × 10−9 M. Moreover, residual thiram on apple peel was extracted and detected with a recovery rate range of 99.3%. The resulting substrate with high SERS activity, stability and strong magnetic responsivity makes the Fe3O4@Au core–shell nanocomposites a perfect choice for practical SERS detection applications.

One-step synthesis of gold nanoflowers of tunable size and absorption wavelength in the red & deep red range for SERS spectroscopy.

We describe a novel protocol for a one-step, seed-less, organic solvent- and surfactant-free synthesis of optically dense aqueous colloids of gold nanoflowers (AuNF), with tunable absorption wavelength between 620 and 800 nm. We demonstrate that simple variation of the ratio of two reagents allows the plasmonic band position to be tuned to any desired wavelength ± 5 nm, namely to those of the laser sources commonly used for SERS spectroscopy. The AuNF size distribution was sufficiently narrow, comparable to that known with seed-mediated synthesis. The AuNF have been validated as efficient aggregation-free substrates for surface-enhanced Raman scattering (SERS) spectroscopy using two common fluorescent dyes, Nile Blue and Crystal Violet, both thiol-free. Their fluorescence was quenched and SERS signal intensity was a linear function of the dye concentration, from nanomolar to micromolar range. Easy to prepare and to use, these AuNF appear as a particularly user-friendly and efficient way to obtain plasmonic substrates for SERS in the red and deep red spectral range.

Ratiometric SERS biosensor for sensitive and reproducible detection of microRNA based on mismatched catalytic hairpin assembly

MicroRNAs (miRNAs) serve as significant regulators in a variety of diseases and have been emerging as a class of promising biomarkers for early cancer diagnosis. Herein, an enzyme-free surface-enhanced Raman scattering (SERS) platform was proposed for sensitive and reliable detection of target miRNA-21 using a corrective internal standard (IS)-based ratiometric SERS probe coupled with mismatched catalytic hairpin assembly (CHA) amplification. The 4-aminothiophenol (4-ATP) was used as IS molecule and modified on the surface of silver nanoparticles decorated silicon wafer. In principle, the presence of miRNA-21 could cyclically trigger the allosteric effects of mismatched CHA amplification and the 3′-R6G labeled hairpin probe 1 (H1) was opened. Then, the hairpin probe 2 (H2) hybridized with H1 to form H1–H2 complex and the released miRNA-21 was free to participate in the next cycle of CHA reaction. Meanwhile, the H1–H2 complex could hybridize with the capture DNA on the SERS chip, making the Raman tag of R6G close to the surface of SERS substrate, and the intensity of SERS signal from R6G labels increase while that from 4-ATP remain relatively unchanged. Benefiting from outstanding performances of the ratiometric SERS strategy and enzyme-free CHA amplification system, this platform exhibits sensitivity toward miRNA-21 with a limit of detection of 3.5 fM and a broad dynamic range from 10 fM to 100 nM. More importantly, this proposed method presents an excellent reliable SERS analysis with the correction of IS. The developed strategy holds a potential alternative tool for miRNA detection in biomedical research and early clinical diagnosis.

Rapid detection of malachite green residues in fish using a surface-enhanced Raman scattering-active glass fiber paper prepared by in situ reduction method

Food safety issues, especially those related to drug residues, have caused concern in recent years. Malachite green (MG), which is frequently used as ectoparasiticide, fungicide, and antiseptic in fish farming, is poisonous and carcinogenic. Several technologies and methods have been developed to accurately detect MG, but they can be time-consuming and expensive. Herein, we prepared a glass fiber paper as a surface-enhanced Raman scattering substrate for rapid and convenient detection of MG residues in fish. Uniform silver nanoparticles were deposited on the glass fiber paper by two in situ reduction steps of silver nitrate. The Raman signal of MG was detected and recorded using a portable Raman spectrometer in 10 s. There was a good linear relationship between the surface-enhanced Raman scattering signal intensity and the concentration of MG between 1 × 10−7 and 1 × 10−5 mol/L and the limit of detection was 5 × 10−10 mol/L. Residual MG in fish samples was extracted and detected with a recovery rate range of 98.9–119.4%. This method provides a novel way to detect MG in fish.

Thin-film microextraction coupled to surface enhanced Raman scattering for the rapid detection of benzoic acid in carbonated beverages

Benzoic acid (BA) is widely used as an antimicrobial preservative in carbonated beverages. In this study, silica gel thin-film microextraction (TFME) coupled to surface enhanced Raman scattering (SERS) was applied for the rapid detection of BA in carbonated beverages. The TFME process was performed by placing small pieces of silica gel substrate in a simple homemade device, and then the content of BA was detected using SERS after colloidal gold was uniformly dropped onto the substrate. The obtained SERS signals of BA were strong and of high reproducibility. A good linearity between the concentration of BA and the SERS signal intensity at 994cm−1 in the range of 25–500μgmL−1 was obtained under optimal experimental conditions. The detection limit value was found to be 3.6μgmL−1 and the recovery of the spiked BA was in the range 85.0–103.0%. The developed method was successfully applied to detect BA in carbonated beverage samples as the results were consistent with those using high performance liquid chromatography, suggesting that it is a rapid, convenient and sensitive way to achieve BA detection in carbonated beverages.

Novel ratiometric surface-enhanced raman spectroscopy aptasensor for sensitive and reproducible sensing of Hg2+

It is important to precisely monitor mercury (II) ions (Hg2+) for environment protection and human health monitoring. Although many strategies have been developed in the past decades, there still remains a challenge for developing an ultrasensitive, simple and reliable approach to detect Hg2+. Herein, we report a ratiometric surface-enhanced Raman scattering (SERS) aptasensor by employing aptamer-modified Au@Ag core-shell nanoparticles (Au@Ag NPs) as highly functional sensing probes, allowing for ultrasensitive detection of Hg2+. In principle, the thiolated 5′-Cy3 labeled aptamer probe (Cy3-aptamer) is firstly immobilized on the SERS substrate surface and then hybridizes with the 5′-Rox labeled complementary DNA (cDNA) to form a rigid double-stranded DNA (dsDNA), in which the Cy3 and Rox Raman labels are used to produce the ratiometric Raman signals. In the presence of Hg2+, the aptamer DNA turns into the thymine (T)-Hg2+-T mediated hairpin structure, leading to the dissociation of dsDNA. As a result, the Rox labels are away from the Au@Ag NP SERS substrate while Cy3 labels are close to it. Therefore, the intensity of SERS signal from Cy3 labels increases while that from Rox labels decreases. The ratio between the Raman intensities of Cy3 labels and Rox labels is linear with Hg2+ concentrations in the range from 0.001 to 1.0nM, and the limit of detection is estimated to be 0.4pM. The proposed strategy provides a new rapid, simple and reliable approach for sensitive detection of Hg2+ and may create a universal methodology for developing analogous aptasensors for a wide range of other analytes determination.