Surface-enhanced Raman Scattering Signal Of Rhodamine 6G Research Articles

One-Pot Aqueous Synthesis of Icosahedral Au as Bifunctional Candidates for Enhanced Glucose Electrooxidation and Surface-Enhanced Raman Scattering.

Bifunctional candidates, which could provide catalytic and plasmonic properties simultaneously, could activate a promising development for biomedicine. Here, we kinetically controlled and synthesized a penta-twinned icosahedral Au (Ih Au) by a facile wet-chemical protocol without assistance of stabilizers. Benefiting from icosahedral morphology and kinetic synthesis process, the Ih Au nanoparticles (NPs) incorporate three key advantages: (i) ample active sites/"hot spots" and surface strain, (ii) good stability/chemical inertness and easy functionalization, and (iii) biological compatibility and a clean surface, which could promote their electrocatalysis and photonic capacity. Ih Au NPs, as bifunctional nanomaterials, exert excellent electrocatalytic and surface-enhanced Raman scattering (SERS) performances. Ih Au delivers the highest glucose electrooxidation (GEO) peak current density with 6.87 mA cm-2, which is 14 times larger than that of Turkevich Au (0.49 mA cm-2) under the same condition. Moreover, the SERS signals of rhodamine 6G (R6G) on Ih Au are much stronger than that on the other corresponding Au counterparts. Particularly, the SERS intensity of R6G on Ih Au increases by about four times compared to that on Au NPs. This study motivates the great prospect for combining Ih Au's bifunctionalities and indicates the potential of bifunctional nanomaterials in biologically implanted devices.

Dynamic reaction regulated surface-enhanced Raman scattering for detection of trace formaldehyde

A simple and reliable method was developed by combining redox reaction with surface-enhanced Raman scattering (SERS) for the indirect detection of formaldehyde (FA). Silver nanoparticles (AgNPs) can be generated from the reaction between the silver ammonia solution containing silver nanoclusters (AgNCs@Tollens) and FA, which can improve the SERS signal of rhodamine 6G (R6G). The detection principle was based on the enhancement of the SERS signal of R6G caused by the increase in the intensity of localized surface plasmon resonance (LSPR) upon the reduction of AgNCs@Tollens by FA. This method exhibits high sensitivity and selectivity for the detection of FA with a linear range from 5 μM to 160 μM and a limit of detection (LOD) of 2.5 μM. The proposed method was successfully used for the detection of FA released from furniture panels with a recovery rate of 95–100%.

Ultrasensitive and uniform surface-enhanced Raman scattering substrates for the methidathion detection

In this paper, we proposed a rapid method of detecting Methidathion pesticides by surface enhanced Raman scattering (SERS). In the method, Ag nanoparticles (AgNPs) are synthesized by the modified Tollens technique and deposited on glass slides to become simple detection arrays for SERS detection. The AgNPs synthesis used in this research is environmentally friendly and does not produce harmful substances to the environment. Through measuring/investigating the SERS signals of Rhodamine 6G under different concentrations, the preparation process and process parameters of the detection substrate are determined. The Methidathion detection limit reaches 0.1 ppm based on the substrates. This work lays a foundation for preparation of large-scale SERS detection arrays in the future.

Surface enhanced Raman scattering of gold nanoparticles aggregated by a gold-nanofilm-coated nanofiber

Aggregation of metal nanoparticles plays an important role in surface enhanced Raman scattering (SERS). Here, a strategy of dynamically aggregating/releasing gold nanoparticles is demonstrated using a gold-nanofilm-coated nanofiber, with the assistance of enhanced optical force and plasmonic photothermal effect. Strong SERS signals of rhodamine 6G are achieved at the hotspots formed in the inter-particle and film-particle nanogaps. The proposed SERS substrate was demonstrated to have a sensitivity of 10−12 M, reliable reproducibility, and good stability.

Accumulation and interparticle connections of triangular Ag-coated Au nanoprisms by oil-coating method for surface-enhanced Raman scattering applications

To examine the optical responses of surface-enhanced Raman scattering (SERS) for tuned plasmonic nanoparticles, triangular Ag-coated Au (Au@Ag) nanoprisms with different sizes were separately synthesized, which were well controlled in their size (edge-length) and localized surface plasmon resonance (LSPR) wavelength (69.0 ± 8.4 to 173.8 ± 25.6 nm in size and 662–943 nm in LSPR wavelength). The mechanism of Ag shell formation on the Au nanoprisms was also studied with scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS). The Au@Ag nanoprisms were immobilized by covering a colloidal solution containing the nanoprisms with silicone oil and evaporating the solvent in the oil (oil-coating method) so as to form a layer of accumulated plasmonic Au@Ag nanoprisms that had LSPR peak wavelengths tuned from 839 to 1182 nm. The accumulation conditions were analyzed by field-emission scanning electron microscopy (FE-SEM) and a Raman mapping technique. The Au@Ag nanoprisms under excitation at 632.8 nm exhibited higher SERS signals of rhodamine 6G, and SERS-mapped images of the novel immobilized films were obtained at different magnifications. It was concluded that accumulated Au@Ag nanoprisms undergoing tip-planar interconnections could produce enhanced local fields, resulting in higher SERS signals.

Rough SERS substrate based on gold coated porous silicon layer prepared on the silicon backside surface

We report in this paper a novel method to elaborate rough Surface Enhanced Raman Scattering (SERS) substrate. A single layer of porous silicon was formed on the silicon backside surface. Morphological characteristics of the porous silicon layer before and after gold deposition were influenced by the rough character (gold size). The reflectance measurements showed a dependence of the gold nano-grains size on the surface nature, through the Localized Surface Plasmon (LSP) band properties. SERS signal of Rhodamine 6G used as a model analyte, adsorbed on the rough porous silicon layer revealed a marked enhancement of its vibrational modes intensities.

High-Yield Synthesis of Hollow Octahedral Silver Nanocages with Controllable Pack Density and Their High-Performance Sers Application.

Nanoparticle-assembled octahedral Ag nanocages with sharp edges have been successfully synthesized through a Cu2 O-based template-assisted strategy. In the reaction system, Ag nanoparticles can be self-assembled on the surface of Cu2 O octahedrons, which is accomplished by the reduction of Ag+ by NaBH4 in the presence of sodium citrate as a capping agent. The hollow octahedral Ag nanocages are obtained after removing the inner Cu2 O cores with acetic acid. According to the scanning electron microscopy (SEM) and transmission electron microscopy characterization, the Ag nanocages are weaved by small nanoparticles, the rough surfaces are bestrewed with pores and sharp edges. It is found that the pack density of Ag nanoparticles strongly affects the surface enhanced Raman scattering (SERS) activities. The as-prepared 1.05-Ag cages with optimal pack density have suitable interparticle distance and suitable size of pores, which significantly enhance SERS signals. The SERS signals of rhodamine 6G (R6G) molecules can be detected at an ultralow concentration of 10-14 m when 1.05-Ag cages are used as substrates. In addition to sensitivity, 1.05-Ag cages also exhibit good reproducibility. It is expected that the ultrahigh sensitivity will endow the Ag nanocages to become a promising candidate as high-performance SERS-based chemical sensor.

Conversion of AgCl nanocubes to Ag/AgCl nanohybrids via solid–liquid reaction for surface‐enhanced Raman scattering detection

In this reported work, Ag/AgCl nanohybrids were synthesised through a facile solid–liquid reaction approach by reducing pre-grown AgCl nanocubes with a sodium borohydride (NaBH4) ethanol solution. The morphology of the AgCl nanocubes' precursor is kept very well after the reactions. The influence of the NaBH4 concentration and the injection speed of NaBH4 solution were studied. It is demonstrated that the prepared Ag/AgCl nanohybrids can serve as effective surface-enhanced Raman scattering (SERS) substrate. Rhodamine 6G (R6G) as the typical SERS analyte was applied to determine the effect of the Ag/AgCl substrate, and SERS signals of R6G were observed in a low concentration of 1 × 10−12 M. Furthermore, the Ag/AgCl substrate was applied to detect other analytes such as crystal violet and 4-mercaptobenzoic acid, which also show high sensitivity.

Large Area Au Decorated Multi-Walled CNTs Film for Surface Enhanced Raman Scattering

We reported on a study upon a Surface-enhanced Raman Scattering (SERS) substrate produced from a large area multi-walled carbon nanotube (MWCNT) films decorated with Au nanoparticles. The morphology and spectrum of the MWCNTs/Au composite structure was characterized with scanning electron microscopy and spectrophotometer. The SERS signals of Rhodamine 6G (R6G) absorbed on the substrate were improved, which could contribute to the enlarged surface area for adsorption of molecules and Localized Plasmon Resonance Effect. The results indicated that it is potential to produce sensitive SERS substrates via further fine-tuning of size, shape of the nanostructure.

Controlled Preparation of Uniform TiO2-Catalyzed Silver Nanoparticle Films for Surface-Enhanced Raman Scattering

Silver nanoparticle (AgNP) film is a kind of useful material in biochemical and biomedical fields as it can be used as a sensor based on its surface plasmon resonance for surface enhanced Raman scattering (SERS) analysis. In this work, a uniform AgNP film with controlled nanoparticle size, shape, and density have been prepared on TiO2 film in a AgNO3 solution by photocatalysis reduction method. The influences of TiO2 film thickness and morphology on the AgNP’s growth have been systemically studied. It is found that a thicker TiO2 film with nanocrystalline morphology leads to a higher AgNP’s growth rate, while a thinner TiO2 film with membrane morphology leads to a lower AgNP’s growth rate. Experimental SERS results show that the AgNP film prepared with different TiO2 films and ultraviolet light irradiation time exhibit different SERS signals of rhodamine 6G (10–6 M). Atomic force microscope and scanning electron microscope analysis reveal that the size effect is a key factor affecting the SERS of our prepared AgNP films, which has also been evaluated by finite-difference time-domain simulation. It is found that the larger the average AgNP’s size (≤λ/4) and roughness, the higher the Raman enhancement. The SERS mapping images exhibit a good uniform Raman enhanced results in our prepared TiO2-catalyzed AgNP film with a low relative standard deviation of approximately 10%.

Dealloying Ag–Al Alloy to Prepare Nanoporous Silver as a Substrate for Surface‐Enhanced Raman Scattering: Effects of Structural Evolution and Surface Modification

Sensitive detection of molecules by using the surface-enhanced Raman scattering (SERS) technique depends on the nanostructured metallic substrate and many efforts have been devoted to the preparation of SERS substrates with high sensitivity, stability, and reproducibility. Herein, we report on the fabrication of stable monolithic nanoporous silver (NPS) by chemical dealloying of Ag-Al precursor alloys with an emphasis on the effect of structural evolution on SERS signals. It was found that the dealloying conditions had great influence on the morphology (the ligament/pore size) and the crystallization status, which determined the SERS signal of rhodamine 6G on the NPS. NPS with small pores, low residual Al, and perfect crystallization gave high SERS signals. A high enhancement factor of 7.5 × 10(5) was observed on bare NPS obtained by dealloying Ag(30)Al(70) in 2.5 wt % HCl at room temperature followed by 15 min aging at around 85 °C. After coating Ag nanoparticles on the NPS surface, the enhancement factor increased to 1.6 × 10(8) owing to strong near-field coupling between the ligaments and nanoparticles.

Additional amplifications of SERSvia an optofluidic CD-based platform

In this paper, signal amplifications of surface-enhanced Raman scattering (SERS) are realized by an optofluidic compact disc (CD)-based preconcentration method for effective label-free environmental and biomolecular detections. The preconcentration of target molecules is accomplished through the accumulation of adsorbed molecules on SERS-active sites by repeating a 'filling-drying' cycle of the assay solution in the optofluidic CD platform. After 30 cycles, the clear and high SERS signal of rhodamine 6G of 1 nM is readily detected. In addition to the preconcentration-based signal amplification by the optofluidic SERS system on the CD platform, we introduce a controlled precipitation of gold nanoparticles by CuSO4 for SERS substrates. This method provides high-throughput, high-sensitive and large-area uniform SERS substrates on the optofluidic CD platform. The uniform SERS signals from different positions in spots of 3 mm2 on the different CDs gives us confidence in the reliability and stability of our SERS substrates.

Deposition of silver nanoleaf film onto chemical vapor deposited diamond substrate and its application in surface-enhanced Raman scattering

An approach for simultaneously synthesizing and immobilizing silver nanoleaves (SNLs) on γ-mercaptopropyltrimethyoxysilane (MPTS)-modified chemical vapor deposited (CVD) diamond film surface has been developed. As-grown diamond film surface was oxidized by exposing to UV irradiation in oxygen gas atmosphere, and then the oxygen-terminated diamond film was dipped into a methanol solution of MPTS to form a self-assembled MPTS monolayer on the diamond film surface. SNLs were then deposited on diamond film surfaces by an electroless process. The morphology of SNL film was characterized by scanning electron microscopy. The thickness of SNL layer deposited onto the CVD diamond substrate increased with increasing the deposition time and the formation mechanism of SNL films was also discussed. Their performance as surface-enhanced Raman scattering (SERS) substrates was evaluated by using rhodamine 6G (R6G) as the probe molecule. Compared with self-assembled silver nanoparticle film and silver film from the mirror reaction, the SERS signal of R6G was obviously improved on the SNL films.