High Enhancement Factor Research Articles

Polydopamine-Mediated Ag and ZnO as an Active and Recyclable SERS Substrate for Rhodamine B with Significantly Improved Enhancement Factor and Efficient Photocatalytic Degradation

We demonstrate the development of an active multicomponent Ag/PDA/ZnO@GMF surface-enhanced Raman scattering (SERS) substrate via introducing bio-inspired polydopamine (PDA) in between a noble metal (AgNPs) and ZnO nanorods. The insertion of PDA enabled efficient charge redistribution between metal and semiconductor through their aromatic cores. The substrate exhibited a high enhancement factor (EF) of 1010 for the organic pollutant dye Rhodamine B (RhB). Subsequent exposure of a RhB-loaded substrate to an external UV light source developed an efficient pathway for RhB degradation and replenished the substrate for multiple usage cycles with remarkable photostability. Thus, enhanced performance of the substrate in terms of light-harvesting capability and high charge-separation efficiency was observed. In addition, the much larger surface area of the branched ZnO nanostructures served as a template for PDA assisted synthesis and controlled deposition of AgNPs, which further improved the SERS effect. Our work seeks to understand the contributions of the noble metal and semiconductor components and the synergistic effects of combining them with a facile charge transport medium to enable the fabrication of highly efficient SERS substrates for use in industrial and environmental applications.

Three-dimensional nanorod array for label-free surface-enhanced Raman spectroscopy analysis of microRNA pneumoconiosis biomarkers

Novel approaches are required to overcome the challenges associated with conventional microRNA (miRNA) detection methods and realize the early diagnosis of diseases. This work describes a novel label-free surface-enhanced Raman spectroscopy (SERS) method for the detection of the miRNA biomarkers for pneumoconiosis on a three-dimensional Au-coated ZnO nanorod array (Au-ZnO NRA). The Au-ZnO NRA substrate, which was fabricated via a modified seeding method combined with ion sputtering, provided a high enhancement factor and good spatial uniformity of the signal. With the Au-ZnO NRA, the SERS spectra of miRNAs were obtained in 30 s without labeling at room temperature. Density functional theory calculations were performed to understand the structural fingerprints of the miRNAs. Principal component analysis was carried out to identify the pneumoconiosis biomarkers based on their fingerprint SERS signals. Dual-logarithm linear relationships between the SERS intensity and the miRNA concentration were proposed for quantitative analysis. The label-free SERS method has limits of detection on the femtomolar level, which is much lower than the concentrations of the miRNA biomarkers for pneumoconiosis in lung fibroblasts.

Synthesis, physico-chemical characterization and field emission behaviour of 3D chrysanthemum like pristine ReS2, and ReS2-rGO nanocomposite

3D chrysanthemum like pristine ReS2 and nanocomposite of ReS2 with reduced graphene oxide (rGO) have been synthesized using facile one step hydrothermal method, followed by physico-chemical characterizations to reveal their phase, structural and electronic properties. Efforts have been made to reveal the influence of process parameters on morphology and growth of the as-synthesized products. From application point of view, field emission (FE) behavior of pristine ReS2 and ReS2-rGO nanocomposite emitters has been investigated at base pressure of 1 × 10–8 torr. The ReS2 and ReS2-rGO nanocomposite emitters showed values of turn-on field (corresponding to emission current density of 1μA cm−2) as 2.10 and 1.66 V μm−1, and field enhancement factor (β) as ∼965 and 1176, Furthermore, the ReS2-rGO nanocomposite emitter delivered maximum emission current density of ∼1472 μA cm−2 at applied field of 3.1 V μm−1. Both the emitters exhibited good emission current stability at pre-set value ∼5 μA over more than 3 h duration. The superior FE properties of the ReS2-rGO nanocomposite emitter are attributed to optimized morphology offering high field enhancement factor coupled with modulation of electronic properties reflected as lowering of the work function. The value of work function of ReS2-rGO nanocomposite, measured using a retarding field analyzer, is found to be 4.29, lower than that of the pristine sample (4.49 eV). The results signify that functionality of pristine nanostructures is greatly improved via formation of nanocomposites and desirable nanocomposites possessing unique morphology can be synthesized under optimized experimental conditions using a facile and inexpensive hydrothermal route.

Quantitative SERS sensor based on self-assembled Au@Ag heterogeneous nanocuboids monolayer with high enhancement factor for practical quantitative detection.

Accurate and rapid quantitative detection of pesticide and pollutant levels in the actual sample can aid in protecting food security, environmental security, and human health. A high Raman enhancement factor and good repeatability of the surface-enhanced Raman spectroscopy (SERS) substrates are favorable to quantitative analysis. Herein, a quantitative SERS sensor based on constructed self-assembled plasmonic Au@Ag heterogeneous nanocuboids (Au@Ag NCs) monolayer was developed. The sensor was used to quantitatively detect the trace pesticides extracted from pear surfaces and pollutants in fishpond water. Densely packed Au@Ag NCs fabricated into large-scale monolayer films were chemically functionalized using 4-methyl-thiobenzoic acid (4-MBA) at the organic/aqueous interface, in which plentiful nanogaps contribute to increase hotspots. Their sharp corners and edges make the sensor have high SERS performance through providing abundant "hot spots." The obtained optically SERS-based sensor with uniform liquid-state interfacial nanoparticle arrays appeared to have nice SERS performance and uniformity using crystal violet (CV) as a probe molecule. In particular, the proposed SERS sensor was applied for quantitative detection of thiabendazole (TBZ) extracted from pear surfaces and malachite green (MG) in fishpond water down to levels of 0.0105nM and 0.87nM for SERS assay respectively. As a result, our proposed SERS quantitative detection strategy is quite preferred to on-site analysis and supervision of contaminant in food samples.

Three-dimensional SERS sensor based on the sandwiched G@AgNPs@G/PDMS film

Three-dimensional (3D) SERS substrate with the denser “hotspots” is synthesized by the constriction of PDMS film decorated with sandwiched graphene@AgNPs@graphene (G@AgNPs@G) nanostructure. Graphene layers above and below the AgNPs are used to absorb molecules onto the “hotspots”, and prevent the oxidation of AgNPs in our design. PDMS films can be easily shrunk for 3D structures, causing advantages in enhancement ability and light-matter interaction. Benefiting from the above advantages, a detection limit of 10−14 M (CV) and enhancement factor (EF) of 3.9 × 109 were obtained in our experiment. Theoretical analyses (FDTD) were also used to study the enhancement mechanism. For practical purposes, in-situ detection of MG molecules on the fish surface and the label-free detection of DNA base of adenine (A) and cytosine (C) were also studied. The high enhancement factor, great sensitivity, reliability, and stability of substrate reasonably proved that it can be used as an excellent SERS substrate for biomolecular detection.

Flexible hydrophobic filter paper-based SERS substrate using silver nanocubes for sensitive and rapid detection of adenine

Flexible paper-based surface enhanced Raman spectroscopy (SERS) substrate has attracted great attention in the sensitive detection of analytes in recent years. However, due to its inherent hydrophilic surface, the nanoparticles will not be concentrated very well on the surface of the paper. This reduces the reproducibility and sensitivity of the paper-based substrate. Herein, we demonstrate flexible hydrophobic paper-based substrate using silver nanocubes loaded on polymethylhydrosiloxane modified filter paper (AgNCs@SiO2/PMHS modified filter paper) to realize high sensitivity and reproducibility. The hydrophobic filter paper was obtained by dip-soaking the filter paper into PMHS solution, resulting in increased contact angle to ~112.5°. The AgNCs@SiO2/PMHS modified paper substrate shows high analytical enhancement factor (AEF) of 6.55 × 106, which is 2.2-fold enhancement compared to AgNCs@SiO2/normal paper substrate, and a low detection limit of 0.1 nM rhodamine 6G and 0.89 nM adenine. The high SERS enhancement factor and sensitivity is attributed to the high hotspots density created in the hydrophobic surface as a result of the excellent uniformity and superior sample collection efficiency compared to the normal filter paper-based substrate. Besides, the substrate shows excellent spot-to-spot and substrate-to-substrate reproducibility, with relative standard deviation (RSD) of 6.05% and 9.22%, respectively. Moreover, the AgNCs@SiO2/PMHS modified filter paper substrate achieved good stability; the Raman signal intensity only drops by 25.88% after 3 months of exposure to air. Therefore, this flexible hydrophobic AgNCs@SiO2/PMHS modified filter paper substrate with low cost fabrication and label-free SERS detection is a promising SERS platform for analytical and biological sensing applications.

Comparative indexes, fuel characterization and thermogravimetric- Fourier transform infrared spectrometer-mass spectrogram (TG-FTIR-MS) analysis of microalga Nannochloropsis Oceanica under oxidative and inert torrefaction

The torrefaction performances of microalga Nannochloropsis Oceanica under oxidative and inert atmospheres are characterized and compared with each other based on several operating parameters. By conducting several comparative indexes, the results suggest that oxidative torrefaction is more capable of upgrading microalgae due to its relatively lower solid yield and energy input, as well as relatively higher enhancement factor and upgrading energy index. Compared to inert torrefaction, the indexes indicate that oxidative torrefaction at 250 °C for 30 min has higher energy yield (1.02 times) and energy efficiency (2.2 times) but whereas lower energy input (0.4 times). With increasing torrefaction severity, the pyrolysis curve gradually becomes smooth and shift to a high-temperature zone. The peak temperatures of torrefied microalgae present an increasing trend, especially in the oxidative atmosphere. After oxidative torrefaction, microalgal solid biofuel is upgraded as peat and lignite, from the viewpoint of elemental composition. Furthermore, oxidative torrefaction is more suitable than inert torrefaction for producing bio-oil which mainly contains dianhydromannitol, neophytadiene, and palmitoleic acid. The TG-FTIR-MS results uncover the pyrolysis characteristics and reactivity of torrefied microalgae, and elucidate that oxidative torrefied microalgae is more reactive.

Massively Parallel Arrays of Size-Controlled Metallic Nanogaps with Gap-Widths Down to the Sub-3-nm Level.

Metallic nanogaps (MNGs) are fundamental components of nanoscale photonic and electronic devices. However, the lack of reproducible, high-yield fabrication methods with nanometric control over the gap-size has hindered practical applications. A patterning technique based on molecular self-assembly and physical peeling is reported here that allows the gap-width to be tuned from more than 30nm to less than 3nm. The ability of the technique to define sub-3-nm gaps between dissimilar metals permits the easy fabrication of molecular rectifiers, in which conductive molecules bridge metals with differing work functions. A method is further described for fabricating massively parallel nanogap arrays containing hundreds of millions of ring-shaped nanogaps, in which nanometric size control is maintained over large patterning areas of up to a square centimeter. The arrays exhibit strong plasmonic resonances under visible light illumination and act as high-performance substrates for surface-enhanced Raman spectroscopy, with high enhancement factors of up to 3 × 108 relative to thin gold films. The methods described here extend the range of metallic nanostructures that can be fabricated over large areas, and are likely to find many applications in molecular electronics, plasmonics, and biosensing.

Development of derivatization/air‐assisted liquid‐liquid microextraction procedure for analyzing short‐chain fatty acids; assessment of the analytes in fruit juice samples

AbstractAn air‐assisted liquid‐liquid microextraction method has been developed by gas chromatography‐flame ionization detection for the extraction, derivatization, and determination of five short chain fatty acids including acetic acid, propionic acid, butyric acid, valeric acid, and caproic acid from different fruit juices. In this method, butyl chloroformate was used as extraction solvent and derivatization agent, simultaneously. For this purpose, sample solution was adjusted at pH 8 and then mixed with picoline (as a catalyst). Next, a few microliters of butyl chloroformate was added to the solution and after performing predetermined extraction cycles, the obtained cloudy solution was centrifuged. An aliquot of the sedimented phase was injected into the determination system. Low limits of detection (3.23–9.63 ng/mL) and quantification (10.8–32.4 ng/mL) were obtained. The method had a proper repeatability (relative standard deviations ≤ 7.38%) for intra‐ (n = 6) and interday (n = 5) precisions at a concentration of 50 ng/mL (each analyte). High enrichment factors (360–415), extraction recoveries (72–93%), and enhancement factors (1126–1852) were obtained. The developed method was successfully used in determination of the analytes in the studied samples.

Enhanced sensitivity to ultralight bosonic dark matter in the spectra of the linear radical SrOH

Coupling between Standard Model particles and theoretically well-motivated ultralight dark matter (UDM) candidates can lead to time variation of fundamental constants including the proton-to-electron mass ratio $\mu\equiv m_{p}/m_{e}\approx1836$. The presence of nearly-degenerate vibrational energy levels of different character in polyatomic molecules can result in significantly enhanced relative energy shifts in molecular spectra originating from $\partial_{t}\mu$, relaxing experimental complexity required for high-sensitivity measurements. We analyze the amplification of UDM effects in the spectrum of laser-cooled strontium monohydroxide (SrOH). SrOH is the first and, so far, the only polyatomic molecule to be directly laser cooled to sub-millikelvin temperatures, opening the possibility of long experimental coherence times. Because of the high enhancement factors ($\left|Q_{\mu}\right|\approx10^{3}$), measurements of the $\tilde{X}\left(200\right)\leftrightarrow\tilde{X}\left(03^{1}0\right)$ rovibrational transitions of SrOH in the microwave regime can result in $\sim10^{-17}$ fractional uncertainty in $\delta\mu/\mu$ with one day of integration. Furthermore, ultracold SrOH provides a promising platform for suppressing systematic errors. More complex SrOR radicals with additional vibrational modes arising from larger ligands R could lead to even greater enhancement factors.

Rapid and sensitive SERS detection of melamine in milk using Ag nanocube array substrate coupled with multivariate analysis

In this study, a facile Ag nanocube (NC) array substrate was fabricated for rapid SERS detection of melamine in milk. This easily-prepared substrate exhibited high Raman enhancement factor (~1.02 × 105) and good reproducibility with ~10.75% spot-to-spot variation in Raman intensity. Our proposed method can detect melamine as low as 0.01 ppm in standard solutions and 0.5 ppm in real milk samples after a simple one-step solvent extraction. Two multivariate analysis tools including partial least squares and support vector machines (SVM) were explored to develop reliable regression models for quantitative SERS analysis of melamine. By comparison, SVM regression models exhibited better predictive performance, especially in liquid milk, with root mean square error (RMSE) of calibration = 5.5783, coefficient of determination (R2) of calibration = 0.9807, RMSE of prediction = 1.9636, and R2 of prediction = 0.9736. Hence, this study offers a rapid and sensitive detection of adulterant melamine in milk samples.

Highly efficient SERS substrates with different Ag interparticle nanogaps based on hyperbolic metamaterials

Surface-enhanced Raman scattering (SERS) substrates based on Hyperbolic metamaterials (HMM) have received tremendous attention due to the presence of confined optical modes, i.e., the surface plasmon polaritons (SPP) and bulk plasmon polaritons (BPP). In the present study, a multilayer HMM SERS substrate was fabricated, comprising a monolayer of silver nanoparticles (Ag NPs) and Au-Al2O3 films. Our study demonstrates that the Ag NPs layer excited SPP and BPP, and the localized surface plasmon (LSP) resonance of the Ag NPs layer coupled with BPP, creating a strong electromagnetic field at the interparticle gaps of the Ag NPs. Interestingly, increasing the multilayer stacking of HMM will strengthen the SERS activity until a certain threshold. On the top of HMM, the interparticle gaps of the Ag NPs were adjusted to enhance the SERS characteristics and the maximum EF appeared at the gap of 10 nm. Performing theoretical simulations as well as experiments, the ultra-sensitivity, good reproducibility, reusability, and high enhancement factor of the proposed SERS substrate were assessed. Lastly, the ultralow limits of detection for melamine in milk were 10−7 M, satisfying the needs for successful implementation in the food safety field.

Development of a green in-situ derivatization and deep eutectic solvent-based dispersive liquid–liquid microextraction method for analysis of short-chain fatty acids in beverage samples optimized by response surface methodology

An in-situ dispersive liquid–liquid microextraction and derivatization method based on deep eutectic solvent has been developed for the analysis of five short chain fatty acids (as model compounds) in different beverage samples prior to their determination by gas chromatography-flame ionization detection. In this method, 2-butanol was used as dispersive solvent derivatization reagent. For this purpose, the sample solution is transferred into a test tube and after dissolving sodium chloride in the solution, a suitable volume of HCl solution is added as catalyst. Thus, a mixture of 2-butanol and ethyl methyl ammonium chloride-carvacrol deep eutectic solvent (as an extraction solvent) is prepared and the mixture is quickly injected into the solution. The analytes are derivatized and extracted into the fine droplets of extracting agent, simultaneously. After centrifugation, an aliquot of the sedimented phase is injected into the separation system. Low limits of detection (0.89–6.6 µg L-1) and quantification (3.1–22.3 µg L-1) were obtained. Good repeatabilities with relative standard deviations ≤9.2% were obtained at the selected three concentrations. Also high enrichment factors, extraction recoveries, and enhancement factors were obtained within the ranges of 223–270, 76–92%, and 1074–1845, respectively. The developed method was successfully used in determination of the analytes in different beverage samples.

Ultrasensitive SERS platform made via femtosecond laser micromachining for biomedical applications

Surface-enhanced Raman spectroscopy (SERS) is a research method in which a lack of cost-effective, versatile platforms with high enhancement factor (EF) is still a major obstacle to its widespread use. The platforms should be also easy to manufacture, stable in time (for weeks or even for months) and manufactured with a highly reproducible method.We demonstrate SERS platforms based on silicon modified on the surface by laser ablation and covered with SERS-active metal. The substrates were fabricated by a femtosecond laser, thus the method is simple, very fast and creates highly uniform SERS platforms in a large number. The platform was tested with para-mercaptobenzoic acid (p-MBA) in terms of sensitivity and reproducibility. The calculated EF was at the level of 108 and the standard deviation (SD) gives 7% for 10−6 M solution of p-MBA based on the intensity of the band at 1073 cm−1. Optimized SERS substrate also exhibits excellent stability for up to six months.We also give the proof-of-concept of using our platform and, for the first time, the SERS analysis of the most important human opportunistic fungal pathogen Candida spp. (Candida glabrata, Candida albicans SN148 and C. albicans BWP17). Finally, the chemometric analysis in the form of Principal Component Analysis (PCA) allowed to strain differentiation of Candida spp., and to distinguish the studied Candida species from Gram-positive bacterial samples with Staphylococcus aureus. Our results demonstrate that the proposed SERS platform is a perfect substrate for detection, identification and differentiation between fungal and bacterial pathogens using SERS technique.

Using the near field optical trapping effect of a dielectric metasurface to improve SERS enhancement for virus detection

In this paper, we report the effect of optical trapping on the enhancement factor for Raman spectroscopy, using a dielectric metasurface. It was found that a higher enhancement factor (up to 275%) can be obtained in a substrate immersed in water, where particles are freee to move, compared to a dried substrate, where the particles (radius r=9 nm, refractive index n=1.58) are fixed on the surface. The highest enhancement is obtained at low concentrations because, this case, the particles are trapped preferentially in the regions of highest electric field (hotspots). For high concentrations, it was observed that the hotspots become saturated with particles and that additional particles are forced to occupy regions of lower field. The dielectric metasurface offers low optical absorption compared to conventional gold substrates. This aspect can be important for temperature-sensitive applications. The method shows potential for applications in crystal nucleation, where high solute supersaturation can be achieved near the high-field regions of the metasurface. The high sensitivity for SERS (surface-enhanced Raman spectroscopy) at low analyte concentrations makes the proposed method highly promising for detection of small biological particles, such as proteins or viruses.

SERS Based Lateral Flow Immunoassay for Point-of-Care Detection of SARS-CoV-2 in Clinical Samples.

The current scenario, an ongoing pandemic of COVID-19, places a dreadful burden on the healthcare system worldwide. Subsequently, there is a need for a rapid, user-friendly, and inexpensive on-site monitoring system for diagnosis. The early and rapid diagnosis of SARS-CoV-2 plays an important role in combating the outbreak. Although conventional methods such as PCR, RT-PCR, and ELISA, etc., offer a gold-standard solution to manage the pandemic, they cannot be implemented as a point-of-care (POC) testing arrangement. Moreover, surface-enhanced Raman spectroscopy (SERS) having a high enhancement factor provides quantitative results with high specificity, sensitivity, and multiplex detection ability but lacks in POC setup. In contrast, POC devices such as lateral flow immunoassay (LFIA) offer rapid, simple-to-use, cost-effective, reliable platform. However, LFIA has limitations in quantitative and sensitive analyses of SARS-CoV-2 detection. To resolve these concerns, herein we discuss a unique modality that is an integration of SERS with LFIA for quantitative analyses of SARS-CoV-2. The miniaturization ability of SERS-based devices makes them promising in biosensor application and has the potential to make a better alternative of conventional diagnostic methods. This review also demonstrates the commercially available and FDA/ICMR approved LFIA kits for on-site diagnosis of SARS-CoV-2.

Synthesis of Diamond@SiO2@Ag composite materials for high SERS effect

Among various carbon materials, diamond stands out due to excellent physical and chemical properties. In this work, we designed Dia@SiO2@Ag composites combining diamond micropowder and Ag nanoparticles by a simple chemical method and obtained stable substrate for surface enhanced Raman scattering (SERS) owing to its high surface-to-volume ratio, low density, as well as close bond between diamond and Ag. As-prepared Dia@SiO2@Ag presented high activity to detect crystal violet and rhodamine 6G molecules, which was demonstrated by significantly enhanced SERS spectra and high enhancement factor values (108-109). Moreover, Dia@SiO2@Ag also showed desired sensitivity, which was investigated by detection limit. Therefore, our study provided more theoretical support and broadened the functional applications of diamond, particularly in Raman detection.

Au/SiO2-Nanolaminated Plasmonic Nanoantennas as Refractive-Index-Insensitive and Transparent Surface-Enhanced Raman Spectroscopy Substrates

Surface-enhanced Raman spectroscopy (SERS) has become a powerful technique for ultrasensitive biochemical detection providing molecular fingerprint information. Due to the strong dependence of surface plasmon resonance wavelength on plasmonic nanostructures’ surrounding refractive index (RI), SERS enhancement factors (EFs) at hotspots are sensitive to changes in background RI, which is detrimental to quantitative SERS biochemical analysis in real-world applications with spatially and temporally varying RI matrices. This work reports on a tapered-shape nanolaminate plasmonic nanoantenna (TNLNA) platform that supports multiple, spatially overlapped, hybridized magnetoelectric localized surface plasmon modes revealing high SERS EFs (>107) and an insensitivity to background RI variations (between 1.30 and 1.60). Furthermore, we demonstrate that the uniform arrays of TNLNAs can be manufactured on flexible transparent polymer films to achieve backside-excitable and reversible SERS measurements for in situ label-free glucose monitoring on a skin phantom.

Surface-enhanced Raman scattering sensors for biomedical and molecular detection applications in space.

The detection of molecular traces in the environment is a technical problem that is critical in pollutant control procedures at all stages of spacecraft assembly, in space flight, as well as in other technological processes such as food production, medical diagnostics, environmental control, warfare. However, in the aerospace industry, it is necessary to detect molecular traces of contaminants with extreme sensitivity, as even concentrations as low as part-per-billion (ppb) can be critical during long missions. The high sensitivity of the Volatile Organic Compounds (VOCs) detection within the air can be a challenge because of the poor affinity of VOC’s to the metal surface of the sensor substrate. In this work, we present a surface‐enhanced Raman scattering (SERS) spectroscopy technique as a highly sensitive and selective molecular sensor for gas trace detection not sensitive to molecules adsorbtion on sensing element. The developed hybrid SERS platform for molecular trace detection is supported by the hybrid nanoplasmonic porous silicon membrane in conjunction with micropump to achieve the trace level detection of VOCs in the environment. The combination of silicon membrane, made by electrochemical etching of the microchannels in the silicon chip, with chemical deposition of the silver nanoparticles inside the channels, produce a porous Ag nanoparticles membrane with a high density of plasmonic nanostructures (“hot spots”). The micropump integrated with the SERS sensor, pump the air with VOC’s molecules through the plasmonic membrane “hot spots” to increase the probability of interaction of VOC’s molecules with SERS substrate and to increase the enhancement factor. The sensor chip structure was designed, gas flow in the sensor was simulated, and the sensor was fabricated using 3D printing. The limit of detection of hydrazine with concentration level 10–12 M from solution and the vapor phase 0.1 ppm was demonstrated. The anisole vapors with concentration 0.5 ppb spectra in the air were recorded. Our results demonstrate that plasmonic membrane can be used as a high enhancement factor SERS sensor for many pollutants molecules detection with the nanomolar sensitivity and can be applied in the design of sensors for space applications, environment control, biomedical diagnostic.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12567-021-00356-6.

Photochemical decoration of silver nanoparticles on silver vanadate nanorods as an efficient SERS probe for ultrasensitive detection of chloramphenicol residue in real samples

Aquaculture and farming industries have been seriously threatened by the illegal use of antibiotics as feed-additives to benefit the animal growth. Although various conventional chemical sensing approaches have been widely explored for the trace-level detection of antibiotics, the effective and accurate monitoring techniques are still highly demanded. Herein, we propose a novel surface-enhanced Raman scattering (SERS) substrate with the heterogeneous integration of silver nanoparticles (Ag NPs) on silver vanadate nanorods (β-AgVO3 NRs) for the ultrasensitive detection of popular antibiotic, chloramphenicol (CAP). The photochemical decoration of Ag NPs on the surface of β-AgVO3 NRs remarkably enhances the Raman signal intensity of CAP molecules by the synergistic action of the mechanisms of electromagnetic and chemical enhancement. The structural features of Ag-NPs@β-AgVO3-NRs favor the formation of hotspots at the interface between NPs and NRs by enhanced surface area and numerous active sites for the interaction with CAP molecules. The SERS measurement of CAP molecules on the Ag-NPs@β-AgVO3-NRs shows a trace-level limit of detection (10−10 M), high uniformity (5.29%), good reproducibility (3.89%), and high analytical enhancement factor (2.05 × 108). The proposed SERS substrate possesses excellent detection ability in monitoring real samples like tap water, milk and eye drops.