Surface-enhanced Raman Scattering Substrates Research Articles

Fabrication of polydimethylsiloxane (PDMS)-Based Flexible Surface-Enhanced Raman Scattering (SERS) Substrate for Ultrasensitive Detection.

This article presents a fabrication method for a flexible substrate designed for Surface-Enhanced Raman Scattering (SERS). Silver nanoparticles (AgNPs) were synthesized through a complexation reaction involving silver nitrate (AgNO3) and ammonia, followed by reduction using glucose. The resulting AgNPs exhibited a uniform size distribution ranging from 20 nm to 50 nm. Subsequently, 3-aminopropyl triethoxysilane (APTES) was employed to modify a PDMS substrate that had been surface-treated with oxygen plasma. This process facilitated the self-assembly of AgNPs onto the substrate. A systematic evaluation of the impact of various experimental conditions on substrate performance led to the development of a SERS substrate with excellent performance and an Enhanced Factor (EF). Utilizing this substrate, impressive detection limits of 10-10 M for R6G (Rhodamine 6G) and 10-8 M for Thiram were achieved. The substrate was successfully employed for detecting pesticide residues on apples, yielding highly satisfactory results. The flexible SERS substrate demonstrates great potential for real-world applications, including detection in complex scenarios.

Recent Development and Applications of Stretchable SERS Substrates.

Surface-enhanced Raman scattering (SERS) is a cutting-edge technique for highly sensitive analysis of chemicals and molecules. Traditional SERS-active nanostructures are constructed on rigid substrates where the nanogaps providing hot-spots of Raman signals are fixed, and sample loading is unsatisfactory due to the unconformable attachment of substrates on irregular sample surfaces. A flexible SERS substrate enables conformable sample loading and, thus, highly sensitive Raman detection but still with limited detection capabilities. Stretchable SERS substrates with flexible sample loading structures and controllable hot-spot size provide a new strategy for improving the sample loading efficiency and SERS detection sensitivity. This review summarizes and discusses recent development and applications of the newly conceptual stretchable SERS substrates. A roadmap of the development of SERS substrates is reviewed, and fabrication techniques of stretchable SERS substrates are summarized, followed by an exhibition of the applications of these stretchable SERS substrates. Finally, challenges and perspectives of the stretchable SERS substrates are presented. This review provides an overview of the development of SERS substrates and sheds light on the design, fabrication, and application of stretchable SERS systems.

Challenges in surface‐enhanced Raman scattering signal for ethephon detection: Theoretical and experimental approaches

AbstractEthephon, a widely used growth regulator in fruits and vegetables, requires careful monitoring because of its toxicity. However, as far as we know, only two works are found in the literature regarding surface‐enhanced Raman scattering (SERS) ethephon detection. Indeed, obtaining the SERS signal revealed to be challenging. Therefore, we have evaluated the SERS signal of ethephon using theoretical (as density functional theory and charge‐assisted fragment interaction) and experimental approaches, addressing this limited literature knowledge. Theoretical Raman spectra with Ag or Au atoms at reactive sites exhibited enhanced ethephon SERS signal via AgCl bonding, consistent with the experimental data. Multiple experimental procedures were employed to obtain the SERS signal, including pH variations, salt addition, excitation laser lines, time dependency, and different SERS substrates (Ag colloid and Ag island films). Salt addition (NaCl) improved SERS signal, correlating with Ag colloid aggregation. Analysis in Ag colloid showed the pH 7.0 as optimal for ethephon detection, using freshly prepared Ag colloid + ethephon dispersion with ethephon powder being directly dissolved into Ag colloid. Only the AgCl band intensity improved with time. Ag colloid (wet medium — 633 nm laser line) outperformed Ag island films (dry medium — 785 nm laser line).

Exploring Reliable and Efficient Plasmonic Nanopatterning for Surface- and Tip-Enhanced Raman Spectroscopies.

Surface-enhanced Raman scattering (SERS) is of growing interest for a wide range of applications, especially for biomedical analysis, thanks to its sensitivity, specificity, and multiplexing capabilities. A crucial role for successful applications of SERS is played by the development of reproducible, efficient, and facile procedures for the fabrication of metal nanostructures (SERS substrates). Even more challenging is to extend the fabrication techniques of plasmonic nano-textures to atomic force microscope (AFM) probes to carry out tip-enhanced Raman spectroscopy (TERS) experiments, in which spatial resolution below the diffraction limit is added to the peculiarities of SERS. In this short review, we describe recent studies performed by our group during the last ten years in which novel nanofabrication techniques have been successfully applied to SERS and TERS experiments for studying bio-systems and molecular species of environmental interest.

Food Safety Issues in the Oltrepò Pavese Area: A SERS Sensing Perspective.

Handly and easy-to-use optical instrumentation is very important for food safety monitoring, as it provides the possibility to assess law and health compliances at every stage of the food chain. In particular, the Surface-enhanced Raman Scattering (SERS) method appears highly promising because the intrinsic drawback of Raman spectroscopy, i.e., the natural weakness of the effect and, in turn, of the signal, is overcome thanks to the peculiar interaction between laser light and plasmonic excitations at the SERS substrate. This fact paved the way for the widespread use of SERS sensing not only for food safety but also for biomedicine, pharmaceutical process analysis, forensic science, cultural heritage and more. However, the current technological maturity of the SERS technique does not find a counterpart in the recognition of SERS as a routine method in compliance protocols. This is mainly due to the very scattered landscape of SERS substrates designed and tailored specifically for the targeted analyte. In fact, a very large variety of SERS substrates were proposed for molecular sensing in different environments and matrices. This review presents the advantages and perspectives of SERS sensing in food safety. The focus of the survey is limited to specific analytes of interest for producers, consumers and stakeholders in Oltrepò Pavese, a definite regional area that is located within the district of Pavia in the northern part of Italy. Our attention has been addressed to (i) glyphosate in rice fields, (ii) histamine in a world-famous local product (wine), (iii) tetracycline, an antibiotic often detected in waste sludges that can be dangerous, for instance in maize crops and (iv) Sudan dyes-used as adulterants-in the production of saffron and other spices, which represent niche crops for Oltrepò. The review aims to highlight the SERS performance for each analyte, with a discussion of the different methods used to prepare SERS substrates and the different reported limits of detection.

Exploiting Purine as an Internal Standard for SERS Quantification of Purine Derivative Molecules Released by Bacteria.

Surface-enhanced Raman scattering (SERS) is a highly sensitive technique used in diverse biomedical applications including rapid antibiotic susceptibility testing (AST). However, signal fluctuation in SERS, particularly the widespread of signals measured from different batches of SERS substrates, compromises its reliability and introduces potential errors in SERS-AST. In this study, we investigate the use of purine as an internal standard (IS) to recalibrate SERS signals and quantify the concentrations of two important purine derivatives, adenine and hypoxanthine, which are the most important biomarkers used in SERS-AST. Our findings demonstrate that purine IS effectively mitigates SERS signal fluctuations and enables accurate prediction of adenine and hypoxanthine concentrations across a wide range (5 orders of magnitude). Calibrations with purine as an IS outperform those without, exhibiting a 10-fold increase in predictive accuracy. Additionally, the calibration curve obtained from the first batch of SERS substrates remains effective for 64 additional substrates fabricated over a half-year period. Measurements of adenine and hypoxanthine concentrations in bacterial supernatants using SERS with purine IS closely align with the liquid chromatography-mass spectrometry results. The use of purine as an IS offers a simple and robust platform to enhance the speed and accuracy of SERS-AST, while also paving the way for in situ SERS quantification of purine derivatives released by bacteria under various stress conditions.

Au-Coated ZnO Surface-Enhanced Raman Scattering (SERS) Substrates: Synthesis, Characterization, and Applications in Exosome Detection.

Developing a biomolecular detection method that minimizes photodamage while preserving an environment suitable for biological constituents to maintain their physiological state is expected to drive new diagnostic and mechanistic breakthroughs. In addition, ultra-sensitive diagnostic platforms are needed for rapid and point-of-care technologies for various diseases. Considering this, surface-enhanced Raman scattering (SERS) is proposed as a non-destructive and sensitive approach to address the limitations of fluorescence, electrochemical, and other optical detection techniques. However, to advance the applications of SERS, novel approaches that can enhance the signal of substrate materials are needed to improve reproducibility and costs associated with manufacture and scale-up. Due to their physical properties and synthesis, semiconductor-based nanostructures have gained increasing recognition as SERS substrates; however, low signal enhancements have offset their widespread adoption. To address this limitation and assess the potential for use in biological applications, zinc oxide (ZnO) was coated with different concentrations (0.01-0.1 M) of gold (Au) precursor. When crystal violet (CV) was used as a model target with the synthesized substrates, the highest enhancement was obtained with ZnO coated with 0.05 M Au precursor. This substrate was subsequently applied to differentiate exosomes derived from three cell types to provide insight into their molecular diversity. We anticipate this work will serve as a platform for colloidal hybrid SERS substrates in future bio-sensing applications.

Flexible, foldable and transparent SERS film with high sensitivity and signal homogeneity via silver ion exchange and in-situ reduction

The adhesion between metal plasma and substrate was the key of surface-enhanced Raman scattering (SERS) technology. The preparation of ideal SERS substrate with multiple advantages such as high sensitivity and good signal reproducibility was still the focus of research. A flexible foldable and transparent fluorinated polyimide/silver NPs (FPI@Ag) SERS film was fabricated by the ion exchange and in-situ reduction method in this work. The effects of KOH hydrolysis time, AgNO3 ion exchange time and concentration, the type and concentration of reducing agents on the SERS performance of the FPI@Ag film were systematically discussed. As a result, the hydrolysis time of KOH affected the thickness of the metallic silver layer, the concentration of AgNO3 affected the size and spacing of Ag NPs, and the Raman signal of was remarkably enhanced when borane dimethylamine complex (DMAB) was used as reducing agent. When the detection limit of 4-Aminothiophenol was as low as 1 × 10−11 mol·L−1, the obvious Raman characteristic peak still appeared. The enhancement factor (EF) was up to 9.4 × 107. The linear quantification range was achieved in the range from 10−3–10−11 mol·L−1, R2 = 0.9987. In addition, we also performed multi-cycle bending and torsion test on the FPI@Ag film, and obtained stable Raman signals. The prepared FPI@Ag film can be attached to the surface of uneven samples, which can be used for on-site Raman detection and analysis.

Cell Membrane-Anchored SERS Biosensor for the Monitoring of Cell-Secreted MMP-9 during Cell-Cell Communication.

Matrix metalloproteinase-9 (MMP-9), a proteolytic enzyme, degrades the extracellular matrix and plays a key role in cell communication. However, the real-time monitoring of cell-secreted MMP-9 during cell-cell communication remains a challenge. Herein, we developed a cell-based membrane-anchored surface-enhanced Raman scattering (SERS) biosensor using a Au@4-mercaptobenzonitrile (4-MBN) @Ag@peptide nanoprobe for the monitoring of cell-secreted MMP-9 during cell communication. The multifunctional nanoprobe was created with Au@4-MBN@Ag acting as an interference-free SERS substrate with high enhancement in which the peptide not only serves to anchor the cell membrane but also provides MMP-9-activatable cleaved peptide chains. MMP-9-mediated cleavage resulted in the detachment of the Au@4-MBN@Ag nanoparticles from the cell membrane, thereby decreasing the SERS signals of cancer cells. The cell membrane-anchored SERS biosensor enables the real-time monitoring of cell-secreted MMP-9 during the interaction of MCF-7 and HUVEC cells. This study successfully demonstrates the dynamic change of cell-secreted MMP-9 during the communication between MCF-7 cells and HUVEC cells. The proposed nanoprobe was also utilized to precisely evaluate the breast and hepatoma cancer cell aggressiveness. This study provides a novel strategy for real-time monitoring of MMP-9 secretion during cell communication, which is promising for the investigation of the mechanisms underlying different tumor processes.

Detection of pesticide residues on flexible and transparent fluorinated polyimide film based on surface-enhanced Raman spectroscopy technology

BackgroundExcessive pesticide residues will seriously endanger human health. The complexity and lag of the current popular analytical methods hinder the timeliness of food safety analysis. Surface-enhanced Raman scattering (SERS) was an ultra-sensitive vibration spectroscopy technology with the advantages of less time cost, non-destructive and semi-quantitative detection, which has attracted much attention in the rapid field detection of pesticide residue. It was clear that we need an efficient and convenient substrate for pesticide residue detection based on SRES technology, which needs to be portable, flexible, transparent and easy to detect irregular object surfaces. ResultsA novel SERS sensor was designed to detect single and multi-component pesticide residues on irregular fruit and vegetable surfaces by in-situ growth of silver nanoparticles on a flexible and transparent fluorinated polyimide (FPI) substrate. Among them, Ag NPs were synthesized by liquid phase reduction method (AgNO3-PVP and NaBH4). The results showed that the detection limit of 1–4 BDT was down to 10−10 mol L−1, the enhancement factor (EF) was up to 1.57 × 107, and relative standard deviation (RSD) was 7.49 %. By this method, tricyclazole solution at a concentration of 0.01 mg L−1 was still detectable by the FPI@Ag SERS substrate. The linear quantification was achieved in the range from 100 mg L−1 to 0.01 mg L−1. Two mixed pesticides, tricyclazole and imazalil, were also successfully distinguished. SignificanceThis represents the formation of a flexible, foldable and transparent substrate for rapid on-site detection. Results can be obtained in <5 min by attaching the substrate to the substance to be tested. And the SERS substrate prepared with high sensitivity, stability, portable and convenient analysis, which provided new ideas for efficient and rapid household food safety detection.

Quantitation of surface-enhanced Raman spectroscopy based on deep learning networks

Surface-enhanced Raman scattering (SERS) is a highly sensitive detection method that is widely applied in numerous fields. However, the distribution of SERS "hotspots" and their sensitive response at the nanoscale render the reproducibility and quantitative analysis of SERS spectra difficult. In this study, an analytical method based on deep learning was applied for the quantitative detection of SERS spectra. Using Ag/TiO2 composite nanofilms as SERS substrates, the SERS spectra of Rhodamine 6G (R6G) at concentrations of 10−3, 10−4, 10−5, and 10−6 mol/L were employed as the datasets for quantitative analysis. Using the normalized SERS spectral dataset, the deep learning network autonomously searched for features related to quantitative detection under complex conditions with less dependence on Raman peak intensities and without additional preprocessing, which afforded deep-learning-based SERS quantitative detection with excellent reproducibility and feasibility. SERS spectra of stable physical condition were extracted for statistical analysis, and the trained neural network model adequately predicted the trend of variations in the concentration. Using R6G as the probe molecule, a superior recognition result with an accuracy of 98.1 % for the concentrations of 10−3, 10−4, 10−5, and 10−6 mol/L was obtained using a convolutional neural network on the test set. Therefore, this method provides a feasible new strategy to overcome the quantitative detection limitations of current SERS analysis methods.

Preparation and SERS applications of Ta2O5 composite nanostructures.

Noble metal and semiconductor composite substrates possess high sensitivity, excellent stability, good biocompatibility, and selective enhancement, making them an important research direction in the field of surface-enhanced Raman scattering (SERS). Ta2O5, as a semiconductor material with high thermal stability, corrosion resistance, outstanding optical properties, and catalytic performance, has great potential in SERS research. This study aims to design and fabricate a composite SERS substrate based on Ta2O5 nanostructures, achieving optimal detection performance by combining the urchin-like structure of Ta2O5 with silver nanoparticles (Ag NPs). The urchin-like Ta2O5 nanostructures were prepared using a hydrothermal reaction method. The bandgap was modulated through structure design and the self-doping technique, the charge transfer efficiency and surface plasmon resonance effects were improved, thereby achieving better SERS performance. The composite substrate enables highly sensitive quantitative detection. This composite SERS substrate combines the electromagnetic enhancement mechanism (EM) and chemical enhancement mechanism (CM), achieving ultra-low detection limits of 10-13 M for R6G. Within the concentration range above 10-12 M, there is a good linear relationship between concentration and peak intensity, demonstrating excellent quantitative analysis capabilities. Furthermore, this composite SERS substrate is capable of precise detection of analytes such as crystal violet (CV) and methylene blue (MB), holding broad application prospects in areas such as food safety and environmental monitoring.

Flexible silver ring SERS substrate array fabrication by vortex evaporation method and its application for high sensitive detection of sulfonamides residues in water

Flexible surface-enhanced Raman scattering (SERS) substrates have driven much attention in Raman detection of environmental pollutants due to their unique advantage of sensitivity, low-cost and fast sampling. However, it is still a high challenge for fabricating flexible SERS substrate with high reproducibility and sensitivity. In this study, we developed a novel silver nanoparticle assembly method based on vortex evaporation method to batch assemble multiple silver ring (SR) SERS substrate array on a parafilm. The flexible SR SERS substrates were uniformly covered with active silver nano-islands, which significantly improved the Raman signal intensity of the targets by 126 folds and showed 5 times Raman enhancement compared with the common SERS substrate by direct evaporation method, and also represented the unique bending response properties of flexible substrate. The Raman detection for sulfonamide residues in water with SR SERS substrate represented high sensitivity, which limits of detection for Sulfapyridine and Sulfacloropyridazine were 9.46 and 9.3 × 10−8 mol/L, respectively. The quantitative relationships were obtained in wide linear range of 4 orders with good accuracy and stability. The flexible SR SERS substrate array can be large-scale prepared with good repeatability, stability, and low-cost, which has promising applications for trace contaminants detection in water environment.

Metal–Organic Frameworks–Based Surface–Enhanced Raman Scattering Substrates for Gas Sensing

Gas sensing holds great significance in environment monitoring, real–time security alerts and clinical diagnosis, which require sensing technology to distinguish various target molecules with extreme sensitivity and selectivity. Surface–enhanced Raman spectroscopy (SERS) has great potential in gas sensing for its single molecule sensitivity and fingerprint specificity. However, different from molecule sensing in solutions, SERS detection of gas often suffers from low sensitivity as gas molecules usually display a low Raman cross–section and poor affinity on traditional noble metal nanoparticle (NMNP)–based substrates. Therefore, much effort has been made to solve these problems. Fortunately, the appearance of metal–organic frameworks (MOFs) has shed new light on this direction. Due to the unique functional characteristics of MOFs, such as controllable pore size/shape, structural diversity and large specific surface area, SERS substrates based on MOFs can achieve high sensitivity, excellent selectivity and good stability. Although several reviews on MOF–based SERS substrates have been reported, few focus on gas sensing, which is a great challenge. Here, we mainly review the latest research progress on SERS substrates based on different MOFs. Sensitive and active SERS substrates can be prepared according to the unique advantages of MOFs with different metal centers. Then, we focus on composite SERS substrates based on different MOFs and NMNPs and summarize the application of composite SERS substrates in gas sensing. Finally, the future difficulties and potential possibilities of SERS substrates based on MOFs and NMNPs for gas sensing are discussed.

Dialdehyde starch-enclosed silver nanoparticles substrate with controlled-release “hotspots” for ultrasensitive SERS detection of thiabendazole

Pesticide residues have long been a major concern for food safety. In this study, a dialdehyde starch-encapsulated silver nanoparticles composite with controlled-release “hotspots” was developed as a surface-enhanced Raman scattering (SERS) substrate. At room temperature, most of the Ag NPs were encapsulated in dialdehyde starch, which is beneficial for improving stability, and when heated to the gelatinization point, Ag NPs are completely released and abundant hot spots are formed. We demonstrated sensitive detection of thiabendazole (TBZ) in or on the surface of an apple by means of two ways, i.e., detecting the analyte in solution after pretreatment and in-situ detecting the analyte by using a flexible paper-based substrate. The results showed that the detection limits of TBZ by the two ways were 0.052 ppm and 0.051 ppm respectively, and the recoveries of TBZ range from 96.80 % to 105.46 %. Overall, this SERS substrate shows great potential for pesticide residue detection in food.

Detection of 4-aminothiophenol with core-shell structured Ag@ZnS as a surface enhanced Raman scattering substrate

4-Aminothiophenol (4-ATP, a toxic pesticide intermediate) residues in waste water endanger water ecology and human health. Therefore, the development of reliable surface-enhanced Raman scattering (SERS) substrate is a promising strategy for monitoring and preventing 4-ATP pollution. In this work, a core-shell structured Ag@ZnS hybrid, consisting of Ag nano-core and ZnS nano-shell, was fabricated and employed as a SERS substrate to detect 4-ATP. Owing to the specific core-shell structure, epy as-prepared Ag@ZnS substrate is stable against oxidation and spontaneous agglomeration of Ag NPs, enjoying good stability and uniform hot spots. Moreover, the formation of heterostructure between Ag-core and ZnS-shell offered a remarkable chemical enhancement for the Raman signals. The optimized Ag@ZnS substrate showed high sensitivity for rhodamine 6 G (R6G, 10−9 M) and methylene blue (10−8 M) probes, as well as 4-ATP (10−8 M) target analyte. Likewise, the superior reproducibility (RSD<5.50 %, n = 16) and good stability (79.5 % of initial strength after 28 days) for 4-ATP makes this substrate a good candidate for actual determination of trace 4-ATP. This work proposes a strategy to fabricate a reliable SERS substrate with high sensitivity and superior reproducibility, and the designed Ag@ZnS substrate may be applicable to monitor 4-ATP residues in wastewater.

Enzyme-Assisted Metabolically Coated Bimetallic Thalassiosira pseudonana Nanosilica as a Surface-Enhanced Raman Scattering Substrate for Specific Screening of Prostate Cancer Individuals

Enzyme-Assisted Metabolically Coated Bimetallic <i>Thalassiosira pseudonana</i> Nanosilica as a Surface-Enhanced Raman Scattering Substrate for Specific Screening of Prostate Cancer Individuals

Highly sensitive SERS platform on isotropic ionic liquid-based liposome

An ionic liquid (IL)-based liposome, consisting of an imidazolyl head and two undecene tails (N, Ń-bis(10-undecenyl)-2-methylimidazolium bromide, [MimV11, V11]Br), was prepared through self-assembly and used as a carrier to create an isotropic surface-enhanced Raman scattering (SERS) platform. The bridging of IL terminals was employed to enable the co-assembly in both hotspot formation and the induced localization of analytes. Specifically, gold nanoparticles (Au NPs) were grown and stabilized on the surface using the anion exchangeability and coordination effect of IL. Besides, the confinement effect of the isotropic surface spatially arranges the Au NPs in an array-like pattern, which not only facilitates the formation of hotspot-rich planes but also provides a uniform electrostatic driving force for molecular loading. This contributes to the improvements in detection sensitivity and reproducibility of the SERS signal. On this basis, the co-assembled platform presented an ideal enhancement factor (3.04 × 107) and a low detection limit (10-12 M) for methyl orange (MO). Additionally, the detection performance, adsorption orientation, and their influencing factors were investigated. The results showed that the adsorption of MO on the liposome exhibited two typical orientations, lying-type, and standing-type. It was mainly regulated by the resonance structures of MO and the steric effect of the SERS substrate. The isotropic co-assembly strategy achieves ultrasensitive trace detection and draws a fascinating application prospect for this hotspot-motivated and hot region-located SERS detection mode.

Engineering Branched Au@Ag Nanostar Plasmonic Array for Coupling Electromagnetic Enhancement and SERS Trace Detection of Polystyrene in Aquatic Environments

Micro/nanoplastics are widespread in the environment and may cause severe damage to creatures and human beings. Micro/nanoplastic pollution has become a global focus issue; hence, the rapid and accurate detection of micro/nanoplastics is an essential step to ensure health. Herein, we report a surface-enhanced Raman scattering (SERS) technique to sensitively and quantitatively identify micro/nanoplastics in environmental water samples. A three-dimensional hierarchical Au@Ag nanostar (NSs) was synthesized and employed as an efficient SERS substrate. The “lightning rod effect” generated by tip branches of the nanostars and the coupling effect of the neighboring branches of the nanostar array enabled the ultra-trace detection of crystal violet (CV) down to 10−9 M, even with a portable Raman device. Moreover, the hydrophobic property of the SERS substrate endowed it with a desirable enrichment effect, which meant an increase in the concentration or quantity of the micro/nanoplastic particles. And thereafter, the SERS sensor achieved a highly sensitive detection of polystyrene (PS) particle standard solution at a low concentration of 25 μg/mL or 2.5 μg/mL. Importantly, the detected concentration and the SERS intensity followed a nearly linear relationship, indicating the capability of quantitative analysis of micro/nanoplastics. In addition, the SERS sensor was successfully extended to detect PS particles in environmental water samples, including tap water, sea water, and soil water, and the detection concentration was determined to be 25 μg/mL, 2.5 μg/mL, and 25 μg/mL, respectively. The present Au@AgNSs array substrate with a two-order magnitude signal amplification further exhibited significant advantages in the label-free analysis of micro/nanoplastics in real water samples.

Sensitive and high laser damage threshold substrates for surface-enhanced Raman scattering based on gold and silver nanoparticles.

Surface-enhanced Raman scattering (SERS) is a sensitive and fast technique for sensing applications such as chemical trace analysis. However, a successful, high-throughput practical implementation necessitates the availability of simple-to-use and economical SERS substrates. In this work, we present a robust, reproducible, flexible and yet cost-effective SERS substrate suited for the sensitive detection of analytes at near-infrared (NIR) excitation wavelengths. The fabrication is based on a simple dropcast deposition of silver or gold nanomaterials on an aluminium foil support, making the design suitable for mass production. The fabricated SERS substrates can withstand very high average Raman laser power of up to 400mW in the NIR wavelength range while maintaining a linear signal response of the analyte. This enables a combined high signal enhancement potential provided by (i) the field enhancement via the localized surface plasmon resonance introduced by the noble metal nanomaterials and (ii) additional enhancement proportional to an increase of the applicable Raman laser power without causing the thermal decomposition of the analyte. The application of the SERS substrates for the trace detection of melamine and rhodamine 6G is demonstrated, which shows limits of detection smaller than 0.1ppm and analytical enhancement factors on the order of 104 as compared to bare aluminium foil.