Surface-enhanced Raman Scattering Sensor Research Articles

GaN-Based Substrates as Surface-Enhanced Raman Scattering Sensors for Penicillin G: Does the Size of the Analyte Molecule Matter?

GaN-Based Substrates as Surface-Enhanced Raman Scattering Sensors for Penicillin G: Does the Size of the Analyte Molecule Matter?

Nano-architected titania/gold@GO nanosheets for sonocatalytic degradation of azo dyes in textile wastewater

Environmental pollution is creating serious risks to both human health and the atmosphere which has been a major threat on a global scale. Therefore, it is necessary to focus on the evolution of the environment and trace contaminants for effective and reliable detection and degradation methods. Photochemical methods such as Surface-Enhanced Raman Scattering (SERS) and sono-catalytic degradation can be used to accelerate the detection and degradation of toxic dyes. In the present work, a Gold/Titania/Graphene oxide nanocomposite (ATG) was investigated as a capable dual substrate for SERS sensing and sono-catalytic degradation of pollutants. The nanosize distribution (6–12 nm) of ATG was synthesized by a solvothermal route. X-ray diffraction pattern illustrates the anatase phase of the titanium dioxide. Sonocatalytic degradation was aided using Raman spectroscopy. The effectiveness of ATG as a sono-catalytic substrate and SERS sensor was first evaluated using commercial dyes, such as malachite green and Bismarck brown. Furthermore, research has been conducted on the harmful elements in textile effluents (TE). The NN and C-N bands found in the SERS spectra of TE indicates the presence of carcinogenic azo-dye impurities. The enhancement factor was observed to be 5.77×1012 with the limit of detection (LOD) as 6.0×10−12M. Additionally, the sono-catalysis of ATG was evaluated for the elimination of these dye pollutants in TE. Following sono-catalysis by ATG, a high degradation rate constant of approximately 8.44 ×10−3/min was noted in TE with 89 % of degradation efficiency. The enhanced SERS detection, sono-catalytic degradation of synthetic dyes and effluent stem from the combined action of’ plasmonic characteristics of Au NPs, anatase TiO2, and the π-π stacking characteristic of GO.

Benchtop Fabricated Nano-Roughened Microstructured Electrodes for Electrochemical and Surface-Enhanced Raman Scattering Sensing.

Tailoring a material's surface with hierarchical structures from the micro- to the nanoscale is key for fabricating highly sensitive detection platforms. To achieve this, the fabrication method should be simple, inexpensive, and yield materials with a high density of surface features. Here, using benchtop fabrication techniques, gold surfaces with hierarchically structured roughness are generated for sensing applications. Hierarchical gold electrodes are prepared on pre-stressed polystyrene substrates via electroless deposition and amperometric pulsing. Electrodes fabricated using 1mm H[AuCl₄] and roughened with 80 pulses revealed the highest electroactive surface area. These electrodes are used for enzyme-free detection of glucose in the presence of bovine serum albumin and achieved a limit of detection of 0.36mm, below glucose concentrations in human blood. The surfaces nanoroughened with 100 pulses also showed excellent surface-enhanced Raman scattering (SERS) response for the detection of rhodamine 6G, with an enhancement factor of ≈2×106 compared to detection in solution, and for the detection of a self-assembled monolayer of thiophenol, with an enhancement factor of ≈30 compared to the response from microstructured gold surfaces. It is envisioned that the simplicity and low fabrication cost of these gold-roughened structures will expedite the development of electrochemical and SERS sensing devices.

Gold Nano-colloids impregnated in Langmuir-Blodgett Film of MoS2 flakes as SERS active platform: Fabrication and its application in Malathion detection

The current work focuses on fabrication of Langmuir-Blodgett (LB) films of MoS2 flakes with impregnated gold nano particles (AuNPs) as a noble Surface enhanced Raman Scattering (SERS) active hetero structure. The hot spots created over the heterostructures work as a potent agent for localization of electromagnetic field resulting in high enhancement of Raman Signals. The LB film of MoS2 flakes with and without the AuNPs were thoroughly characterized in our present work. The efficacy of Au–MoS2 substrate as a SERS sensing platform was investigated up to ultrasensitive concentrations using Raman probe molecules. Moreover, the reproducibility and homogeneity of the substrate was also tested with Raman mapping. The as prepared SERS sensing platform was engaged further for detection of Malathion at trace concentrations. The tests to check on service time was also performed. In the contemporary exploration the fabricated substrate reveals its accuracy and effectivity as a SERS sensor. Thus, in future this substrate can be a novel “Nano-Lab on Chip” device for ultrasensitive detections of chemical and bio-chemical composites.

Construction of the Au Nanoparticle/Graphene Oxide/Au Nanotube (AuNP/GO/AuNT) Sandwich Membrane for Surface-Enhanced Raman Scattering Sensing.

Au nanotube-based composite membrane served as surface-enhanced Raman scattering (SERS) substrate with an ultralarge aspect ratio possesses an excellent flexibility and widely tunable surface plasmon resonance, and by introducing graphene oxide (GO) as a spacer layer, the SERS enhancement of the composite membrane is obviously better than those from the individual blocks of the Au nanotubes (AuNTS) membrane and the Au nanoparticle/graphene oxide (AuNP/GO) membrane. Such a "sandwich" (AuNP/GO/AuNT) structured membrane has a high SERS sensitivity and a wide tunability by controlling the size of Au nanoparticles and the thickness of graphene oxide, and the detection limits of the AuNP/GO/AuNT substrate for R6G and NBA are as low as 10-12 and 10-7 M, respectively; the large enhancement is attributed to the adsorption and chemical mechanism of graphene oxide and the physical mechanism of the Au nanoparticles and nanotubes (the electromagnetic field coupling between them).

Simply Developed Surface-Enhanced Raman Scattering (SERS) Sensors for Ultra-Sensitive Detection of Lindane Pesticide

Simply Developed Surface-Enhanced Raman Scattering (SERS) Sensors for Ultra-Sensitive Detection of Lindane Pesticide

A Three-Dimensional Hydrophobic Surface-Enhanced Raman Scattering Sensor via a Silver-Coated Polytetrafluoroethylene Membrane for the Direct Trace Detection of Molecules in Water.

We report a three-dimensional (3D) SERS substrate consisting of a silver nanoparticle (AgNP) coating on the skeleton-fiber surfaces of a polytetrafluoroethylene (PTFE) membrane. Simple thermal evaporation was employed to deposit Ag onto the PTFE membrane to produce grape-shaped AgNPs. The 3D-distributed AgNPs exhibit not only strong localized surface plasmon resonance (LSPR) but also strong hydrophobic performance. High-density hotspots via silver nano-grape structures and nanogaps, the large 3D interaction volume, and the large total surface area, in combination with the hydrophobic enrichment of the specimen, facilitate high-sensitivity sensing performance of such a SERS substrate for the direct detection of low-concentration molecules in water. An enhancement factor of up to 1.97 × 1010 was achieved in the direct detection of R6G molecules in water with a concentration of 10-13 mol/L. The lowest detection limit of 100 ppt was reached in the detection of melamine in water. Such a SERS sensor may have potential applications in food-safety control, environmental water pollution monitoring, and biomedical analysis.

Core-shell structure DA-CDs/AuNPs for the recognition of fenamidone by surface-enhanced Raman scattering

In this work, a facile synthesis method for dopamine carbon dots-based Au nanoparticles (DA-CDs/AuNPs) by seed gold method was reported as the surface enhanced Raman scattering (SERS) booster. DA-CDs with rich in surface functional groups was synthesized using dopamine, citric acid and ethylenediamine as precursors by a facile hydrothermal method, and can be used as the capping agents and reducing agents for the synthesis of DA-CDs/AuNPs. Due to the electromagnetic “hot spots” effect, DA-CDs/AuNPs with core–shell structure exhibited strong SERS activity. Based on the specific interaction of DA-CDs/AuNPs and fenamidone, a detection method of fenamidone was established with a low detection limit of 0.05 μg/mL. Finally, the SERS sensor was successfully applied to the detection of fenamidone in fruit with recoveries between 90.6 % and 98.7 %. The method here proposed can be reliably applied for fenamidone detection on fruits.

Simple and Inexpensive Fabrication of High Surface-Area Paper-Based Gold Electrodes for Electrochemical and Surface-Enhanced Raman Scattering Sensing.

Paper has emerged as an excellent alternative to create environmentally benign disposable electrochemical sensing devices. The critical step to fabricating electrochemical sensors is making paper conductive. In this work, paper-based electrodes with a high electroactive surface area (ESA) were fabricated using a simple electroless deposition technique. The polymerization time of a polydopamine adhesion layer and the gold salt concentration during the electroless deposition step were optimized to obtain uniformly conductive paper-based electrodes. The optimization of these fabrication parameters was key to obtaining the highest ESA possible. Roughening factors (Rf) of 7.2 and 2.3 were obtained when cyclic voltammetry was done in sulfuric acid and potassium ferricyanide, respectively, demonstrating a surface prone to fast electron transfer. As a proof of concept, mercury detection was done through anodic stripping, achieving a limit of quantification (LOQ) of 0.9 ppb. By changing the metal deposition conditions, the roughness of the metalized papers could also be tuned for their use as surface-enhanced Raman scattering (SERS) sensors. Metallized papers with the highest SERS signal for thiophenol detection yielded a LOQ of 10 ppb. We anticipate that this method of fabricating nanostructured paper-based electrodes can accelerate the development of simple, cost-effective, and highly sensitive electrochemical and SERS sensing platforms.

Bacterial cellulose loaded with silver nanoparticles as a flexible, stable and sensitive SERS-active substrate for detection of the shellfish toxin DTX-1.

Diarrheal shellfish toxins are considered one of the most lethal red tide algae toxins in the worldwide. In this work, we propose an Ag NPs-loaded bacterial cellulose membrane (BCM) surface-enhanced Raman scattering (SERS) sensor based on an aptamer (Apt) for the ultrasensitive detection of dinophysistoxin (DTX-1), a type of diarrheal shellfish toxin. During drying, Ag NPs can be further densified on "gel-like" BCM to form high-density SERS "hot spots". We developed the "Apt-SH@Ag NPs@BCM" SERS sensor and used the competition of DTX-1 and complementary base (Cob) in the process of base complementary pairing to achieve SERS detection of DTX-1, with a minimum detection limit of 9.5×10-10mol/L. Sample assays showed DTX-1 recovery rates ranging from 95.8% and 108.2% and the detection results were comparable to those obtained by LC-MS. Therefore, this work holds great potential for detecting of toxic substances in shellfish products, especially for the oyster (portuguese oyster) and mussel (blue mussel).

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.

SERS sensor with rapid and quantitative detection low back pain application

Thoracolumbar fascia (TLF) plays an important role in the biomechanics of the spine. TLF often causes low back pain (LBP), leading to limb movement disorders and numbness. At present, the clinical diagnosis mainly depends on doctors' clinical experience and magnetic resonance imaging. In order to make the diagnosis more convenient and accurate, we designed a “sandwich” biosensor based on surface-enhanced Raman scattering (SERS) to detect C-reactive protein (CRP) and serum amyloid A (SAA) in fascia. In this study, Ag nanocubes (AgNCs) were used as the substrate, so that the antibodies of CRP and SAA were modified on the substrate surface. Then substrate combined with antigen to form the bottom layer of the sandwich. 4-Mercaptobenzoic acid (4-MBA) and Nairn blue chloride (NBA) were used as signaling molecule probes. Hollow gold nanoparticles (HGNPs) modified with (EDC / NHS) enabled the attachment of antibodies to CRP and SAA to the surface of HGNPs. Eventually, the complex formed by the antigen-antibody reaction reacted with the sandwich substrate after the modification reaction to form the final “sandwich” structure. We successfully applied it to the specific detection of inflammatory markers in fascial tissue of TLF. The results showed that it had high stability and repeatability, which can bring some help for clinical work.

Near-Neighbor Electron Orbital Coupling Effect of Single-Atomic-Layer Au Cluster Intercalated Bilayer 2H-TaS2 for Surface Enhanced Raman Scattering Sensing.

It is difficult to perfectly analyze the enhancement mechanism of two-dimensional (2D) materials and their combination with precious metals as surface enhanced Raman scattering (SERS) substrates using chemical enhancement mechanisms. Here, we propose a new mentality based on the coupling effect of neighboring electron orbitals to elucidate the electromagnetic field enhancement mechanism of single-atom-layer Au clusters embedded in double-layer 2H-TaS2 for SRES sensing. The insertion of Au atoms into the 2H-TaS2 interlayer was verified by XRD, AFM, and HRTEM, and a SERS signal enhancement of 2 orders of magnitude was obtained compared to the pure 2H-TaS2. XPS and micro-UV/vis-NIR spectra indicate that the outer electrons of neighboring Au and 2H-TaS2 overlap and migrate from Au to 2H-TaS2. First-principles calculations suggest strong electronic coupling between Au and 2H-TaS2. This study offers insights into SERS enhancement in nonprecious metal compounds and guides the development of new SERS substrates.

SERS-Based Optical Nanobiosensors for the Detection of Alzheimer's Disease.

Alzheimer's disease (AD) is a leading cause of dementia, impacting millions worldwide. However, its complex neuropathologic features and heterogeneous pathophysiology present significant challenges for diagnosis and treatment. To address the urgent need for early AD diagnosis, this review focuses on surface-enhanced Raman scattering (SERS)-based biosensors, leveraging the excellent optical properties of nanomaterials to enhance detection performance. These highly sensitive and noninvasive biosensors offer opportunities for biomarker-driven clinical diagnostics and precision medicine. The review highlights various types of SERS-based biosensors targeting AD biomarkers, discussing their potential applications and contributions to AD diagnosis. Specific details about nanomaterials and targeted AD biomarkers are provided. Furthermore, the future research directions and challenges for improving AD marker detection using SERS sensors are outlined.

Advances in Surface-Enhanced Raman Scattering Sensors of Pollutants in Water Treatment.

Water scarcity is a world issue, and a solution to address it is the use of treated wastewater. Indeed, in these wastewaters, pollutants such as pharmaceuticals, pesticides, herbicides, and heavy ions can be present at high concentrations. Thus, several analytical techniques were initiated throughout recent years for the detection and quantification of pollutants in different types of water. Among them, the surface-enhanced Raman scattering (SERS) technique was examined due to its high sensitivity and its ability to provide details on the molecular structure. Herein, we summarize the most recent advances (2021-2023) on SERS sensors of pollutants in water treatment. In this context, we present the results obtained with the SERS sensors in terms of detection limits serving as assessment of SERS performances of these sensors for the detection of various pollutants.

High-Yield Gold Nanohydrangeas on Three-Dimensional Carbon Nanotube Foams for Surface-Enhanced Raman Scattering Sensors.

Recently, carbon nanomaterial-supported plasmonic nanocrystals used as high-performance surface-enhanced Raman scattering (SERS) substrates have attracted increasing attention due to their ultra-high sensitivity of detection. However, most of the work focuses on the design of 2-D planar substrates with traditional plasmonic structures, such as nanoparticles, nanorods, nanowires, and so forth. Here, we report a novel strategy for the preparation of high-yield Au nanohydrangeas on three-dimensional porous polydopamine (PDA)/polyvinyl alcohol (PVA)/carbon nanotube (CNT) foams. The structures and growth mechanisms of these specific Au nanocrystals are systematically investigated. PDA plays the role of both a reducing agent as well as an anchoring site for Au nanohydrangeas' growth. We also show that the ratio of surfactant KBr to the gold precursor (HAuCl4) is key to obtain these structures in a manner of high production. Moreover, the substrate of the CNT foam-Au nanohydrangea hybrid can be employed as SERS sensors and can detect the analytes down to 10-9 M.

Controlling Atomic-Scale Restructuring and Cleaning of Gold Nanogap Multilayers for Surface-Enhanced Raman Scattering Sensing.

We demonstrate the reliable creation of multiple layers of Au nanoparticles in random close-packed arrays with sub-nm gaps as a sensitive surface-enhanced Raman scattering substrate. Using oxygen plasma etching, all the original molecules creating the nanogaps can be removed and replaced with scaffolding ligands that deliver extremely consistent gap sizes below 1 nm. This allows precision tailoring of the chemical environment of the nanogaps which is crucial for practical Raman sensing applications. Because the resulting aggregate layers are easily accessible from opposite sides by fluids and by light, high-performance fluidic sensing cells are enabled. The ability to cyclically clean off analytes and reuse these films is shown, exemplified by sensing of toluene, volatile organic compounds, and paracetamol, among others.

Silver Nanocube-Decorated PVDF Membranes for SERS Substrates

In this study, we report that silver nanocubes (AgNCs) can be synthesized via the silver mirror reaction (SMR) within 1 min. To extend the reaction time, the sharp-edge AgNCs quickly denucleated and collapsed into small spherical Ag nanoparticles and became aggregates. Based on this discovery, we developed an easy-to-make membrane-based surface-enhanced Raman scattering (SERS) substrate with superior sensitivity and reproducibility. The entire fabrication process, including AgNC synthesis from SMR, membrane pretreatment, and AgNC deposition on the membrane by suction filtration, was completed within 30 min. The SERS intensity of R6G increased 48-fold after the pretreatment of the polyvinylidene difluoride (PVDF) membrane with methanol and NaCl aqueous solutions. The PVDF-based SERS substrate successfully verified attomolar (aM) sensitivity to R6G using 3 × 3 μL of an aqueous sample on a 3 × 3 mm2 substrate. To validate the practicality of the developed SERS substrate as a SERS sensor, it was applied to the detection of malachite green, cocaine, 2,6-pyridinedicarboxylic acid, and tetracycline, with limits of detection of 10 ppb, 1 ppm, 1 ppm, and 1 ppm, respectively. However, the SERS substrate maintained up to 80% sensitivity for only 3 days. Fortunately, a freshly prepared SERS substrate can be quickly fabricated on demand; thus, shelf-life or long-term stability is no longer a concern.

SERS Detection of the Anti-Epileptic Drug Perampanel in Human Saliva.

Surface-Enhanced Raman Scattering (SERS) can obtain the spectroscopic response of specific analytes. In controlled conditions, it is a powerful quantitative technique. However, often the sample and its SERS spectrum are complex. Pharmaceutical compounds in human biofluids with strong interfering signals from proteins and other biomolecules are a typical example. Among the techniques for drug dosage, SERS was reported to detect low drug concentrations, with analytical capability comparable to that of the assessed High-Performance Liquid Chromatography. Here, for the first time, we report the use of SERS for Therapeutic Drug Monitoring of the Anti-Epileptic Drug Perampanel (PER) in human saliva. We used inert substrates decorated with gold NPs deposited via Pulsed Laser Deposition as SERS sensors. We show that it is possible to detect PER in saliva via SERS after an optimized treatment of the saliva sample. Using a phase separation process, it is possible to extract all the diluted PER in saliva from the saliva phase to a chloroform phase. This allows us to detect PER in the saliva at initial concentrations of the order of 10-7 M, thus approaching those of clinical interest.

Machine-learning-assisted SERS nanosensor platform toward chemical fingerprinting of Baijiu flavors.

A novel fingerprinting platform for multiplex detection of flavor molecules in Baijiu was developed by using a surface-enhanced Raman scattering (SERS) nanosensor array in combination with machine learning. The SERS sensors were constructed by core-shell Fe3O4@Ag nanoparticles modified with molecules carrying end-groups of hydroxyl, pyridyl, methyl, and amino, respectively, which interacted with flavors and led to changes in the sensors' spectra. All the Raman spectra acquired from the nanosensor array contacting with the sample were concatenated into a single SERS super-spectrum, representing the flavor fingerprint which was recognized through machine learning. Principal component analysis, support vector machine, and partial least squares were utilized to build classification and quantitation models for predictive analyses. The SERS nanosensor array was successfully used for fingerprinting ten typical flavors in Baijiu including four esters, three alcohols, and three acids, with an accuracy of 100%, linear detection ranges over two orders of magnitude, and limits of detection ranging from 3.45 × 10-3mg/L of phenylethyl acetate to 1.21 × 10-2mg/L of ethyl hexanoate. It was also demonstrated that satisfactory accuracies (recoveries) ranging from 96.2 to 104% and relative standard deviations ranging from 0.65 to 2.78% were obtained for the simultaneous quantification of 3-methylbutyl acetate and phenylethyl acetate in eighteen Baijiu samples of three flavor types including sauce flavor, strong flavor, and light flavor. Compared with the existing detection techniques, this chemical fingerprinting platform is easy to use, highly sensitive, and can perform multiplex detection, which has great potential for practical applications.