Detection Of Rhodamine 6G Research Articles

Application of Delafossite AgFeO2 Nanoparticles as SERS Substrate and Antimicrobial Agent

AbstractWe have used simple chemical route to synthesize delafossite silver ferrite (AgFeO2) nanoparticles (NPs). AgFeO2 NPs were utilized as Raman substrate for detection of Rhodamine 6G (R6G) molecules. AgFeO2 NPs substrate show excellent Surface‐enhanced Raman Scattering (SERS) activity, which enables ultrasensitive detection of R6G with a concentration down to 1 picomolar (1 pM) with an enhancement factor (EF) of 1.6×1010. The observed SERS signal enhancement in this AgFeO2 NPs system is attributed to a combination of electromagnetic (EM) enhancement, charge ‐ transfer (CT) effect between R6G analyte molecules and AgFeO2 NPs surface and Resonance Raman (RR) effect. Further, AgFeO2 NPs were used to study its antibacterial activity against certain different pathogenic bacteria. The antibacterial studies showed that the AgFeO2 NPs possesses potential inhibitory effect against both Gram‐negative and Gram‐positive bacteria. In addition, AgFeO2 NPs was found cytotoxic to yeast cells. The stable aqueous colloids of AgFeO2 NPs may find potential applications in the biomedical field as a sensing platform for the trace level detection of analyte molecules and antimicrobial agent.

Fabrication of hybrid Pd@Ag core-shell and fully alloyed bi-metallic AgPd NPs and SERS enhancement of Rhodamine 6G by a unique mixture approach with graphene quantum dots

In this work, an innovative and simple growth approach of two-step solid state dewetting (SSD) has been introduced for the fabrication of bimetallic and core-shell nanoparticle (NP) configurations. A significant surface-enhanced Raman spectroscopy (SERS) enhancement on the hybrid Pd@Ag core-shell NP substrate is systematically demonstrated by a unique hybrid approach of mixing the graphene quantum dots (GQDs) and Rhodamine 6G (R6G). Due to the substantially increased electromagnetic hotspots in the hybrid Pd@Ag core-shell NP configuration and also the charge transfer enhancement by the addition of GQDs through the chemical enhancement mechanism, over 100 times of SERS signal enhancement is observed for the detection of R6G. The hybrid Pd@Ag core-shell NPs with the background Ag NPs and fully alloyed bi-metallic AgPd NPs without the background Ag NPs are demonstrated on sapphire (0001). The bimetallic and core-shell NPs demonstrate much enhanced localized surface plasmon resonance (LSPR) and thus significantly improved SERS responses. In specific, the hybrid Pd@Ag core-shell NPs demonstrate a gradual blue-shift and narrowing of LSPR peaks while the fully alloyed bi-metallic AgPd NPs show a continuing redshift and broadening of LSPR peaks.

Green preparation of silver nanofilms as SERS-active substrates for Rhodamine 6G detection

A green and reliable seed-mediated electroless deposition method using the Sargentgloryvine stem extract as reducing and capping agent is explored to prepare silver nanofilms (Ag NFs) as surface-enhanced Raman scattering (SERS) active substrates. The average particle size of Ag NFs can be facilely controlled only by adjusting the amount of AgNO3 in the growth solution. Furthermore, the SERS properties of Ag NFs are established experimentally and their Raman enhancement mechanism is revealed by means of the scanning electron microscopy and the finite-difference time-domain simulation. It is found that high surface coverage and slight surface agglomeration of Ag NFs are beneficial for the amplification of Raman signal. Optimized Ag NFs display superior sensitivity towards Rhodamine 6G molecules and good reproducibility, indicating potential applications in SERS-based detection and analysis. Meanwhile, the proposed method to obtain Ag NFs provide a promising route for the preparation of other metal nanofilm.

Multiscale structure enabled effective plasmon coupling and molecular enriching for SERS detection

Surface enhanced Raman scattering (SERS), as a molecular-specific spectroscopy method using plasmonic nanostructures to significantly enhance Raman spectroscopy, has broad application prospects in various fileds. In our work, the Ag/CuO nanowires (NWs)/pyramidal PDMS multiscale structure were rationally fabricated as a multi-dimensional plasmon coupling SERS substrate with molecular enrichment effect. CuO NWs were grown in the pyramid cavity by alkaline etching and formed micro-nano multiscale strucure. The Ag film was decorated on the nano-micro multiscale structure by physical vapor deposition method, endowing the SERS activity. The subwavelength-size Ag/CuO NWs can also provide a rough enough surface to separate the droplets from the air, reduce the surface energy, and achieve a hydrophobic effect. To demonstrate the SERS activity, the proposed multiscale micro-nano structure has been successfully applied to sensitively detect Rhodamine 6G (R6G) at low concentration. Interestingly, we also demonstrate that the Ag/CuO NWs/pyramidal PDMS multiscale structure has excellent molecular adsorption for practical application detection. We successfully achieve the detection for the mixture of R6G, Crystal Violet (CV) and Congo Red (CR) molecule under turbid and different PH environment, which demonstrates its great potential for in-situ detection of chemical dye molecules in complex environments.

Fabrication of Al/Al2O3/Ag SERS substrate by the corrosion method to detect ketoprofen

In this work, we studied and fabricated SERS substrate (surface-enhanced Raman scattering) substrates based on Al/Al2O3/Ag to detect ketoprofen solution at low concentrations. Silver nanoparticles were decorated on Al2O3/Al substrate due to a displacement reaction. By changing the volume ratios of hexadecyltrimethylammonium bromide (CTAB) to AgNO3 and annealing temperature, the SERS substrates were fabricated with the large effective surface area, high density of ``hot-spots. The structure and surface morphology of these SERS substrates were investigated by measurements such as surface image recorded with scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy at a point (EDS pointing), and X-ray diffraction analysis (XRD). The results showed that in the experimental condition of the ratio volume 1:1 between CTAB 0.01M and AgNO3 0.02M solutions, and the displacement reaction time of 30 minutes, annealed samples at 100oC in 2 hours were formed Al/Al2O3/Ag SERS platforms with nanostructure leaf-shaped. The Ag NPs with sizes of 10 - 50 nm were distributed homogeneously on the surface. The Raman signal of the sample showed that Al/Al2O3/Ag SERS substrates could detect rhodamine 6G (R6G) at a very low concentration at 10-11M, analytical enhancement factor (EF) of ~ 8x108. From that, this SERS substrate could be used to detect a ketoprofen solution at a concentration as low as 10 ppm with the enhancement factor of ~ 1.5x106.

Fabrication of Highly Ordered Ag/TiO

Silver nanoparticles deposited on a titania nanopore array (Ag/TiO2 NPA) has been designed as a surface-enhanced Raman scattering (SERS) substrate for sensitive and recycling application of organic molecule detection. A TiO2 NPA was fabricated by a surface oxidization reaction of a titanium sheet by a double anodization process. A Ag/TiO2 NPA was then formed by depositing silver nanoparticles onto the TiO2 NPA by a cycling chemical reduction deposition process. The Ag/TiO2 NPA has a uniform mono-layer dispersion of Ag nanoparticles with a size of 30–50 nm on TiO2 nanopores with a diameter of 100–110 nm. The Ag/TiO2 NPA SERS substrate could facilitate interfacial adsorption of Rhodamine 6G (R6G), which achieves a sensitive detection limit of 10−8 M R6G through SERS spectrum measurement. The Ag/TiO2 NPA SERS substrate achieves an analytical enhancement factor value of 2.6 × 105. The Ag/TiO2 NRA could promote the UV light-excited photocatalytic degradation reaction of R6G adsorbed on its surface which gives rise to a refreshed Ag/TiO2 NRA under UV irradiation for 60 min and accordingly behave as a self-cleaning and recycling SERS substrate. The Ag/TiO2 NPA exhibits a much higher R6G degradation reaction rate constant (0.05764 min−1) than the TiO2 NPA (0.02600 min−1), indicating its superior photocatalytic activity and self-cleaning activity. The refreshed Ag/TiO2 NPA was able to be recycled for the Raman detection of R6G, maintaining a high stability, reproducibility, and cyclability. The highly ordered Ag/TiO2 NPA with well controlled Ag nanoparticle dispersion and TiO2 nanopore shape could act as a suitable SERS substrate for recycling and self-cleaning application for stable and sensitive molecule detection.

High-performance SERS substrate based on perovskite quantum dot–graphene/nano-Au composites for ultrasensitive detection of rhodamine 6G and p-nitrophenol

The designed PQD–G/Au nanocomposite shows high performance for ultrasensitive detection of R6G and PNP, attributed to the synergistic effect of the EM enhancement of Au nanostructures and CM enhancement of PQD–G heterostructures.

Ultrasensitive and reusable SERS probe for the detection of synthetic dyes in food industry through hybrid flower-shaped ZnO@Ag nanostructures

A reliable and accurate sensing of synthetic dyes in foodstuffs is highly significant to prevent health risks. Recently, various heterogeneous structures are used predominantly to explore the distinguished enhancement action of surface-enhanced Raman scattering (SERS) for ultrasensitive detection of multiple food colorants. Herein, we construct a semiconductor/noble-metal heterostructure by deposition of Ag nanoparticles (NPs) on flower-like ZnO microcrystals using a facile photoreduction method. The synergistic effect of flower-like ZnO@Ag nanostructures offers high SERS activity for detection of rhodamine 6G (R6G), sunset yellow (SY), and tartrazine (TZ) with an ultra-low detection limit of 10−12 M, 10−10 M, and 10−11 M, respectively. The flower-like ZnO@Ag nanostructures possess an excellent analytical enhancement factor, sensitivity, and uniformity, towards sensing multiple food colorants. Moreover, the self-reviving ability of the proposed flower-like ZnO@Ag nanostructures is demonstrated by UV-irradiation process and shows its excellent reusability on a single substrate for multiple SERS detection. This work demonstrates the promising use of semiconductor/noble-metal heterostructure with excellent reusability in real-time applications and food safety monitoring.

Hierarchical Particle-In-Quasicavity Architecture for Ultratrace In Situ Raman Sensing and Its Application in Real-Time Monitoring of Toxic Pollutants.

Unstable detection environment is one of the biggest interferences for in situ surface-enhanced Raman spectroscopy (SERS) using in real-time monitoring of toxic pollutants, leading to unreliable results. To address this problem, we have designed and prepared a cavity-based particle-in-quasicavity (PIQC) architecture composed of hierarchical ZnO/Ag nanosheets and nanoprotrusions for improving the in situ SERS performance under a liquid environment. Benefitting from the special cascaded optical field mode, the PIQC ZnO/Ag exhibits excellent in situ SERS detectability, with 10-18 M of limit of detection for rhodamine 6G and 12.8% of signal relative standard deviation value. Furthermore, by means of a microfluidic chip, this PIQC structure is proved to have the quantitative analysis feasibility and realizes real-time monitoring of the 3,3',4,4'-tetrachlorobiphenyl, a representative global environmental hazard, under the flowing environment. The strategy in this paper provides a brand new idea to promote the application of in situ SERS in contaminant monitoring and is also instructive for light control in other optical fields.

Vertically-Oriented WS2 Nanosheets with a Few Layers and Its Raman Enhancements.

Vertically-oriented two-dimensional (2D) tungsten disulfide (WS2) nanosheets were successfully grown on a Si substrate at a temperature range between and 550 °C via the direct chemical reaction between WCl6 and S in the gas phase. The growth process was carefully optimized by adjusting temperature, the locations of reactants and substrate, and carrier gas flow. Additionally, vertically-oriented 2D WS2 nanosheets with a few layers were tested as a surface-enhanced Raman scattering substrate for detecting rhodamine 6G (R6G) molecules where enhancement occurs from chemical enhancement by charge transfer transition from semiconductor). Raman spectra of R6G molecules adsorbed on vertically-oriented 2D WS2 nanosheets exhibited strong Raman enhancement effects up to 9.2 times greater than that on the exfoliated WS2 monolayer flake sample. From our results, we suggest that the WS2 nanosheets can be an effective surface-enhanced Raman scattering substrate for detecting target molecules.

In-situ deposition of silver nanoparticles on silver nanoflowers for ultrasensitive and simultaneous SERS detection of organic pollutants

Recently, a great deal of research has been stepped forward to implement real-time detection of multiple targets using surface-enhanced Raman spectroscopy (SERS). Herein, a novel incorporation of silver nanoparticles (AgNPs) on silver nanoflowers (AgNFs) via the in-situ process offers high SERS enhancement by its unique plasmonic resonance. The electromagnetic mechanism of AgNFs incorporated with AgNPs generates numerous hotspots from abundant nanogaps on nanoflowers and between nanoparticles for ultrasensitive detection of probe molecules. The increment in the SERS signal is demonstrated by depositing the probe molecules, rhodamine 6G (R6G) and Congo Red (CR), on the proposed nanostructure. The proposed AgNF@AgNP nanostructure provides stronger SERS activity than the individual AgNPs and Ag NFs, and possesses superior detection ability towards R6G (10−14 M) and CR (10−9 M) with excellent uniformity (<10.27%) and analytical enhancement factor (AEF) (1012 for R6G and 107 for CR). Moreover, the simultaneous SERS detection of R6G and CR has been demonstrated with trace-level detection of CR at 10−8 M and R6G at 10−13 M. The AgNF@AgNP nanostructure with dense hotspots offers remarkable SERS activity, and becomes as a potential tool to analyze organic molecules from environment for real-world applications.

The influence of oxygen content on the borrowing SERS activity of tin oxides/noble metal composites

Surface enhanced Raman spectroscopy (SERS), as a powerful tool that its sensitive to detect organics hazardous pollutants and analyze the plasmon-driven catalysis reaction with its fingerprint characteristics. And the SERS property of substrate can be effectively enhanced with charge-transferring between the substrate and analyte by utilizing the borrowing SERS activity strategy. Considering the transition metal elements represent multiple valence states, the synergistic interaction of noble metal/transition metal oxides heterostructures can be further modulated with oxygen contents variation of transition metal oxides. In this work, we report the fabrication of high specific area Sn3O4 hollow hierarchical nanostructures with a simple hydrothermal method, which have mixed-valence of Sn2+ and Sn4+. And the composites were prepared with Au coating and the SERS properties of the nanostructures were investigated by detection of rhodamine 6G. The effect of the oxygen content of the transition metal oxides on their SERS performance was analyzed with annealing process. It was found that a high oxygen atomic ratio induced by heat treatment increased the SERS effect of the Au-coated nanostructures for R6G molecules. This property may prove to be very useful in the future research on the borrowing SERS activity of composites of noble metals and metal oxides.

Monolayer ZnS@Ag Nanospheres SERS Substrate for Highly Sensitive Dye Molecules Detection

Surface-enhanced Raman scattering (SERS) substrates with low cost, high sensitivity and good reproducibility are still challenging in practical application. Herein, we propose a facile method to prepare monolayer ZnS@Ag nanospheres (NSs) by sputtering Ag nanoparticles (NPs) on the surfaces of the monolayer ZnS NSs produced by self-assembly. The monolayer ZnS@Ag NSs have rough surface and nanoscale gaps, which can produce large SERS effect. The dye molecules, Rhodamine 6G (R6G) and Rhodamine B (RhB), were used as probe to evaluate the SERS performance on the monolayer ZnS@Ag NSs. It was found that the monolayer ZnS@Ag NSs showed the high SERS sensitivity in the detection of R6G and RhB, the limit of detection (LOD) down to 9.12×10−13 M and 8.55×10−11 M, respectively. The corresponding enhancement factors (EF) are 3.01×108 and 8.2×106, respectively. Furthermore, the ordered structure makes the monolayer ZnS@Ag NSs substrate with high signal reproducibility and stability, and the relative standard deviation (RSD) values are less than 15%. Therefore, the monolayer ZnS@Ag NSs is a candidate for detecting organic dyes in the environment.

PVP‐mediated galvanic replacement growth of AgNPs on copper foil for SERS sensing

Herein, the authors present a simple and cost-effective silver nanoparticles (AgNPs)-based surface-enhanced Raman scattering (SERS) sensor based on galvanic displacement reaction using AgNO3 and copper foil as precursors. With the mediation of polyvinyl pyrrolidone (PVP), AgNPs grow in-situ on the surface of copper foil at room temperature. AgNPs-based SERS sensor was prepared with optimised AgNO3 concentration of 50 mM, the mass ratio of AgNO3 to PVP of 2:1 and characterised using scanning electron microscopy and X-ray diffraction. As-fabricated SERS sensor exhibited a high Raman signal enhancement factor of 3.5 × 105 in the detection of Rhodamine 6G (R6G). Furthermore, a decent linear relationship for methyl parathion sensing was obtained in the range from 1 × 10−6 to 1 × 10−4 M, with an actual detection limit of 1 × 10−6 M. Recoveries of methyl parathion-spiked lake water samples ranging from 93.64 to 106.16% were obtained, suggesting the feasibility of the SERS sensor. These features demonstrated that the AgNPs-based SERS sensor can potentially be used in sensing a trace amount of chemicals in surface water for environmental protection.

Plasmonic filters based on MoS2@Au/Ag hybrids: Controllable separation, preconcentration, and sensitive SERS detection

In this study, plasmonic filters formed by MoS2@Au/Ag hybrids are proposed as a multifunctional analytical platform for controllable separation, preconcentration, and surface enhanced Raman spectra (SERS) detection of a complex mixture of molecules. We mainly detected the mixtures of crystal violet (CV) and congo red (CR), and Rhodamine 6G (R6G) and fluorescein isothiocyanate (FITC) molecules. Firstly, we obtained layered MoS2 films, which are indispensable for the chemical absorption and the formation of dense Au nanoparticles. Secondly, the electric field distribution of Au/Ag hybrids was simulated using COMSOL. The calculated enhancement factor (EF) was 5.49 × 106, which proves that dense “hotspots” were generated. Thirdly, the experimentally obtained limit of detection of R6G and FITC was 10−11 and 10−12 M, respectively. Notably, controllable separation and concentration of the mixture were realized by electrostatic interactions, which could be used to detect each designated molecule in the mixture. Overall, the proposed filters based on MoS2@Au/Ag hybrids exhibit immense potential as a paper-based separation, preconcentration, and sensitive SERS substrate for biological and chemical detection.

Plasmonic Cellulose Nanofibers as Water-Dispersible Surface-Enhanced Raman Scattering Substrates

A water-dispersible surface-enhanced Raman scattering (SERS) substrate is developed to provide rapid and reproducible measurement of solution-borne analytes. Cellulose nanomaterials are generally dispersible in water and are known to act as a reducing agent and support for the synthesis of metal nanoparticles. In this work, cellulose nanofibers (CNF) are decorated with Ag nanoparticles to yield plasmonic cellulose nanofibers (Ag-CNF). The chemical reduction of the Ag onto the CNF is explored and characterized. Conditions are optimized in terms of the SERS intensity of a probe species. A process is introduced to produce colloidally stable bundles of the hybrid nanomaterial that contain closely spaced Ag nanoparticles which serve as SERS hot spots. This water-dispersible substrate offers high reproducibility and rapid analysis of analytes that both chemisorb and physisorb to the Ag nanoparticles. Ag-CNF are used to detect rhodamine 6G and malachite green within 2 min. Malachite green is measured at a limit of detection of 80 pM.

One-Step Synthesis of Gold Nanoparticles Using Liquid Crystal Molecules for Surface-Enhanced Raman Scattering Detection

Gold nanoparticles have received widespread attention as surface-enhanced Raman scattering (SERS) detection active substrates. In this work, we used the nematic liquid crystal molecule N-(4-methoxybenzylidene)-4-butylaniline (MBBA) at room temperature to synthesize liquid crystal (LC)-Au nanoparticles in one step without adding any other reducing agents or stabilizers. Gold nanoparticles synthesized by this method have good sensitivity and stability as a SERS substrate. The nanoparticles can detect Rhodamine 6G (R6G) molecules with a concentration as low as 10−8 M, and the SERS signal does not decrease significantly in 30 days. Using this synthesis principle, we grew gold nanoparticles in a capillary in one step. We expect the proposed method to result in a highly efficient and portable SERS substrate after subsequent improvements.

Ultra-sensitive, reusable, and superhydrophobic Ag/ZnO/Ag 3D hybrid surface enhanced Raman scattering substrate for hemoglobin detection

The small Raman scattering cross section of hemoglobin (Hb) molecules limits its application using a Raman spectroscopy based optical biosensor. Label-free surface enhanced Raman scattering (SERS) detection and degradation of Hb have been achieved using 3D reusable superhydrophobic SERS substrates based on a Ag/ZnO/Ag hybrid structure. The fabrication process follows the decoration of thermally evaporated non-spherical like Ag nanoparticles on hydrothermally grown ZnO nanorods on a catalytic ultra-thin Ag film. From SERS point of view, these 3D SERS substrates exhibit four important characteristics such as a higher surface to volume ratio, surface plasmon resonance in the broad wavelength region of the visible spectrum, a strong electric field at the Ag–ZnO interface due to the formation of a Schottky barrier, and the superhydrophobic surface. The SERS substrates not only performed an outstanding Raman enhancement effect due to the above factors but also displayed multiple recyclabilities owing to their excellent self-cleaning property via a UV light assisted photocatalytic degradation process. The quantitative SERS analysis has been performed by a linear regression method and resulted in 10−13.42M and 10−7.24M limit of detection for Rhodamine 6G (Rh6G) and Hb molecules, respectively, with an enhancement factor of 6 × 1011. The effect of the 3D hybrid structure toward higher SERS activity has been compared with that of 2D SERS substrates, and the SERS mapping of Rh6G molecules proves good homogeneity of the 3D SERS substrates. These ultra-sensitive 3D SERS substrates with reusable capability open the possibility of their use toward biosensors for the early detection of diseases.

Tailoring a novel Au nanodot arrays on graphene substrate for a highly active Surface-Enhanced Raman Scattering (SERS)

In this work, gold nanodots (Au NDs) were arrayed on the thin graphene (GR) layer, prepared by chemical vapor deposition, by focused ion beam technique. Following, GR/Au NDs substrates was evaluated of Surface-Enhanced Raman Scattering (SERS) by using rhodamine 6G (R6G) as a molecular probe. As expected, GR/Au NDs significantly enhanced the SERS signals. The limit of detection for R6G was as low as 10−12 M and the Raman enhancement factor was as large as 108 times. GR/Au NDs SERS-active substrate showed a promising technique to enhance the trace detection and quantitative detection of organic contaminants.

Electrokinetically-Driven Assembly of Gold Colloids into Nanostructures for Surface-Enhanced Raman Scattering.

Surface-enhanced Raman scattering (SERS) enables the highly sensitive detection of (bio)chemical analytes in fluid samples; however, its application requires nanostructured gold/silver substrates, which presents a significant technical challenge. Here, we develop and apply a novel method for producing gold nanostructures for SERS application via the alternating current (AC) electrokinetic assembly of gold nanoparticles into two intricate and frequency-dependent structures: (1) nanowires, and (2) branched “nanotrees”, that create extended sensing surfaces. We find that the growth of these nanostructures depends strongly on the parameters of the applied AC electric field (frequency and voltage) and ionic composition, specifically the electrical conductivity of the fluid. We demonstrate the sensing capabilities of these gold nanostructures via the chemical detection of rhodamine 6G, a Raman dye, and thiram, a toxic pesticide. Finally, we demonstrate how these SERS-active nanostructures can also be used as a concentration amplification device that can electrokinetically attract and specifically capture an analyte (here, streptavidin) onto the detection site.