EFFECT OF SOLVENT ON SURFACE ENHANCED RAMAN SCATTERING SPECTRA OF COLLOIDAL SILVER

The effect of solvent on surface enhanced Raman scattering [SERS) of colloidal silver has been studied. Experiments show that the intensity of SERS is related to the polarity and molecular constitution of the solvent. The influence of solvent is due to the change of the adsorption quantity and adsorption intensity.

TiO_2/Ag composite nanowires for a recyclable surface enhanced Raman scattering substrate

Multifunctional TiO2/Ag composite nanowires are fabricated with a hydrothermal method by precipitating Ag nanoparticles （NPs） on the surfaces of TiO2 nanowires. This hierarchical one-dimensional （1D） nanostructure can be used as a surface enhanced Raman scattering （SERS） substrate with high sensitivity, for detecting the rhodamine 6G （R6G） in a wide range of low concentrations （from 1 × 10 6 M to 1 × 10-12 M）. In addition, the substrate can be self-cleaned under the irradiation of ultraviolet （UV） light due to the superior photocatalytic capacity of the TiO2/Ag composite nanostructure, making the recycled use of SERS substrates closer to reality. With both the evident SERS performance and high efficiency of photocatalytic capacity, such TiOz/Ag composite nanowires demonstrate considerable potential in the chemical sensing of organic pollutants.

STUDY ON PHOTO-INDUCED ORIENTATION OF A NOVEL PHOTO-ALIGNMENT FILM WITH SURFACE ENHANCED RAMAN SCATTERING (SERS) SPECTROSCOPY

Surface enhanced Raman scattering (SERS) spectroscopy was first utilized to study the photo-orientation behaviour of the photoreactive groups on a novel photo-alignment film surface and elucidate the generation mechanism of pretilt angle. The novel photo-alignment film was prepared by spin-coating a solution of ladderlike polysiloxane (LPS) bearing dual photoreactive group on an ITO surface and by irradiation with linear-polarized ultraviolet (LPUV) light A Si—H terminal compound (M) containing an identical photosensitive part has been used to fabricate a model film for SERS investigation.

SURFACE ENHANCED RAMAN SCATTERING OF C_(60) FILMS ON VARIOUS ACTIVE SUBSTRATES

In this paper,we report the study of surface-enhanced Raman Scattering of C_(60)films on roughed Ag,Cu and glass surface.The experiment results indicate that the C_(60)films on Ag substrate possess large enhance effect.An explanation of the enhancement with roughed glass surface is proposed based on waveguide Raman Scattering.

Peroxidase-like single Fe atoms anchored on Ti_(3)C_(2)T_(x)MXene as surface enhanced Raman scattering substrate for the simultaneous discrimination of multiple antioxidants

Single-atom nanozymes(SAzymes)are emerging as promising alternatives to mimic natural enzyme,which is due to high atomic utilization efficiency,well-defined geometric,and unique electronic structure.Herein,Fe single atoms supported on Ti_(3)C_(2)T_(x)(Fe-SA/Ti_(3)C_(2)T_(x))with intrinsic peroxidase activity is developed,further constructing a sensitive Raman sensor array for sensing of five antioxidants.Fe-SA/Ti_(3)C_(2)T_(x)shows excellent peroxidase-like performance in catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine(TMB)with colorimetric reactions.X-ray adsorption fine structure(XAFS)reveals that the electron transport between the Ti_(3)C_(2)T_(x)and Fe atoms occurs along Fe-O-Ti ligands,meanwhile the density functional theory(DFT)calculations confirm the spontaneous dissociation of H_(2)O_(2)and the formation of OH radicals.Furthermore,the peroxidase-like Fe-SA/Ti_(3)C_(2)T_(x)was used as surface enhanced Raman scattering(SERS)substrate of oxidized TMB(TMB+)and achieved satisfied signal amplification performance.Using the blocking effects of free radical reactions,one-off identification of 5 antioxidants,including ascorbic acid(AA),uric acid(UA),glutathione(GSH),melatonin(Mel),and tea polyphenols(TPP),could be realized with this high identifiable catalytic property.This principle could realize 100%distinguish accuracy combined with linear discriminant analysis(LDA)and heat map data analysis.A wide detection concentration ranges from 10^(-8)to 10^(-3)M for five antioxidants was also achieved.

Butterfly-wing hierarchical metallic glassy nanostructure for surface enhanced Raman scattering

The surface-enhanced Raman spectroscopy(SERS)is a technique for the detection of analytes on the surface with an ultrahigh sensitivity down to the atomic-scale,yet the fabrication of SERS materials such as nanoparticles or arrays of coinage metals often involve multiple complex steps with the high cost and pollution,largely limiting the application of SERS.Here,we report a complex hierarchical metallic glassy(MG)nanostructure by simply replicating the surface microstructure of butterfly wings through vapor deposition technique.The MG nanostructure displays an excellent SERS effect and moreover,a superhydrophobicity and self-cleaning behavior.The SERS effect of the MG nanostructure is attributed to the intrinsic nanoscale structural heterogeneities on the MG surface,which provides a large number of hotspots for the localized electromagnetic field enhancement affirmed by the finite-difference time-domain(FDTD)simulation.Our works show that the MG could be a new potential SERS material with low cost and good durability,well extending the functional application of this kind of material.

Surface-enhanced Raman scattering properties of highly ordered self-assemblies of gold nanorods with different aspect ratios

Gold nanorods with aspect ratios of from 1 （particles） to 31.6 were synthesized by the seed-mediated method and packed in a highly ordered structure on a large scale on silicon substrates through capillary force induced self-assembly behaviour during solvent evaporation. The gold nanorod surface exhibits a strong enhancing effect on Raman scattering spectroscopy. The enhancement of Raman scattering for two model molecules （2-naphthalenethiol and rhodamine 6C） is about 5-6 orders of magnitude. By changing the aspect ratio of the Au nanorods, we found that the enhancement factors decreased with the increase of aspect ratios. The observed Raman scattering enhancement is strong and should be ascribed to the surface plasmon coupling between closely packed nanorods, which may result in huge local electromagnetic field enhancements in those confined junctions.

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 6 G 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.

Multiple plasmon couplings in 3D hybrid Au-nanoparticles-decorated Ag nanocone arrays boosting highly sensitive surface enhanced Raman scattering

Plasmon coupling is an essential strategy to realize strong local electromagnetic(EM)field which is crucial for high-performance plasmonic devices.In this work,multiple plasmon couplings are demonstrated in three-dimensional(3D)hybrid plasmonic systems composed of polydimethylsiloxane-supported ordered silver nanocone(AgNC)arrays decorated with high-density gold nanoparticles(AuNPs)which are fabricated by a template-assisted physical vapor deposition process.Strong interparticle coupling,particle-film coupling,inter-cone coupling,and particle-cone coupling are revealed by numerical simulations in such composite nanostructures,which produce intense and high-density EM hot spots,boosting highly sensitive and reproducible surface enhanced Raman scattering(SERS)detection with an enhancement factor of-1.74×10^(8).Furthermore,a linear correlation between logarithmic Raman intensity and logarithmic concentration of probe molecules is observed in a large concentration range.These results offer new ideas to develop novel plasmonic devices,and provide alternative strategy to realize flexible and high-performance SERS sensors for trace molecule detection and quantitative analysis.

Monitoring the penetration and accumulation of gold nanoparticles in rat skin ex vivo using surface-enhanced Raman scattering spectroscopy

Contamination by accidental cutaneous contact with the commercial products and the air pol-hutants raised a considerable health and safety issue.This study aimed to trace the dynamics of the 20 nm gold nanopartide(GNP)penetration and accumulation in rat skin tissues using a surface-enhanced Raman scattering(SERS)techmique.After the topical application of GNPs on rat skin surface,the SERS spectra were recorded for every 15 pum to an overall depth of 75 pum from skin surface for 150 min.The processes of GNP penetration in rat skin were accompanied by aggregation of GNPs,which affected SERS spectra.The results revealed that 20 nm GNPs can penetrate through stratum corneum layer,viable epidermis layer,and then into dermis layer.This study demonstrated for the first time the potential of SERS spectroscopy to monitor the penetration and accumulation of GNPs in rat skin.

Preparation of SiO_2@Au nanorod array as novel surface enhanced Raman substrate for trace pollutants detection

An effective surface enhanced Raman scattering（SERS） substrate is designed and fabricated by synthesis of Si O2 nanorods array via glancing angle deposition, followed by coating Au nanoparticles onto Si O2 surface in order to create numerous ＂hot spots＂. The detecting sensitivity of such substrate could be optimized by simply adjusting the deposition time of Au. Thus, it can be used for detection of Rhodamine 6G at concentration as low as 10^-9M. Furthermore, our SERS substrate is applied to detect 5 μg/g polychlorinated biphenyls in soil sample, which proves its potential for trace environmental pollutants detection.

Hole arrayed metal-insulator-metal structure for surface enhanced Raman scattering by self-assembling polystyrene spheres

A fabrication process based on the self-assembling polystyrene spheres is proposed to obtain hole arrayed metal-insulator-metal （HA-MIM） structure for surface enhanced Raman scattering （SERS）. The localized field enhancement aroused by the gap resonance in the HA-MIM structure is analyzed by finite-different time domain （FDTD） method. With reference to the theory result, the structure is experimentally fabricated and the Raman scattering spectrum of rhodamine 6G （R6G） is measured by a miniaturized Raman spectrometer. The results shows that the enhancement factor is 3.85 times higher than the control sample with single layered metal hole array. The fabrication process to obtain the HA-MIM SERS substrate is reproducible, fast, large area and low cost.

Influence of local environment on the intensity of the localized surface plasmon polariton of Ag nanoparticles

A combined Ag nanoparticle with an insulating or conductive layer structure has been designed tor molecular detection using surface enhanced Raman scattering microscopy. Optical absorption studies revealed localized surface plasmon resonance, which shows regular red shift with increasing environmental dielectric constant. With the combined structure of surface enhanced Raman scattering substrates and rhodamine 6C as a test molecule, the results in this paper show that the absorption has a linear relationship with the local electromagnetic field for insulating substrates, and the electrical property of the substrate has a non-negligible effect on the intensity of the local electromagnetic field and hence the Raman enhancement.

Surface Plasmon Resonance Sensors Based on Polymer Optical Fiber

Surface Plasmon Resonance （SPR） is a powerful technique for directly sensing in biological studies, chemical detection and environmental pollution monitoring. In this paper, we present polymer optical fiber application in SPR sensors, including wavelength interrogation surface enhanced Raman scattering SPR sensor and surface enhanced Raman scattering （SERS） probe. Long-period fiber gratings are fabricated on single mode polymer optical fiber （POF） with 120 μm period and 50% duty cycle. The polarization characteristic of this kind of birefringent grating is studied. Theoretical analysis shows it will be advantageous in SPR sensing applications.

High enhancement factor of Au nano triangular prism structure for surface enhanced coherent anti-Stokes Raman scattering

Coherent anti-Stokes Raman scattering spectroscopy（CARS） is a well-known detecting tool in biosensing and nonlinear spectroscopy. It can provide a non-invasive alternative without the need for exogenous labels,while the enhancement factor for surface plasmon resonances（SPR） are extensively used to increase the local field close to the oscillators and which can obtain high enhancement. In this work, we investigate the enhancement factor of our structure for surface-enhanced coherent anti-Stokes Raman scattering. The absorption spectrum of the structure has been studied, a wide range of absorption has been realized. The enhancement can be as high as 10^（16） over standard CARS. Our design is very useful for improving the enhancement factor of surface-enhanced coherent anti-Stokes Raman scattering.

Construction of Au@Metal-organic framework for sensitive determination of creatinine in urine

Creatinine level in urine is an important biomarker for renal function diseases,such as renal failure,glomerulonephritis,and chronic nephritis.The Au@MIL-101(Fe)was prepared by in situ growth of Au nanoparticles in MIL-101(Fe)as a selective SERS substrate.The Au@MIL-101(Fe)offers the great local surface plasmon resonance(SPR)effect due to gold nanoparticles aggre-gation inside metal-organic frameworks.The framework structure could enrich trace target samples and drag them into SPR hot spots.The optimal Au@MIL-101(Fe)composite substrate is used for analyzing creatinine in urine and the limit of detection is down to 0.1μmol/L and a linear relationship is ranging from 1μmol/L to 100μmol/L.

THE RING OPENING REACTION OF AN EPOXY COMPOUND ON THE TOP OF CHEMISORBED CYSTAMINE STUDIED BY THE SERS TECHNIQUE

Metal foils for Raman scattering were prepared by HNO_3 etching method. These foils werefound to exhibit a strong SERS effect and excellent thermal stability. SERS spectra of cystaminehave been taken to illustrate the usefulness of this sample preparation method in the studies ofchemisorption. The ring opening reactions of an epoxy compound have been observed on the topof chemisorbed cystamine on silver foils.

STUDY ON THE CONCENTRATION DEPENDENCE OF ORIENTATION OF POLYSTYRENE ON SILVER BY THE SERS TECHNIQUE

Polystyrene films were adsorbed onto a silver surface from dichloromethane solutions with concentrations of 0.1 to 12 wt%, and then studied by the surface enhanced Raman technique. A critical concentration for coil interpenetration was observed.

CHEMICALLY DEPOSITED SILVER FILM USED AS A SERS-ACTIVE OVER-COATING LAYER FOR POLYMER FILM

When colloidal silver particles were chemically deposited onto polymer film as an over-coating layer, surface-enhanced Raman scattering (SERS) spectra could be collected for the surface analysis. SERS measurements of liquid crystal film were successfully performed without disturbing the surface morphology.

Synthesis and Raman Performance Enhancement of Multilayer AuAg Heterostructures with Magnetic Resonance

Significant amplification of surface enhanced Raman scattering(SERS)signals can be achieved mainly by the electric field enhancement in metal core-shell nanostructures,and the enhanced magnetic field is rarely studied.In this study,we prepared multi-gap Au/AgAu core-shell hybrid nanostructures by using gold nanocup as the core.The overgrowth processes to grow one,two,and three layers of AgAu hybrid nanoshells can produce Au/AgAu^(1),Au/AgAu^(2),and Au/AgAu^(3) heteronanostructures.The strong plasmon coupling between the core and shell leads to significant electromagnetic field enhancement.Under the synergistic effect of electromagnetic plasmon resonance and plasmon coupling,Au/AgAu core-shell hybrid nanostructures exhibit excellent SERS signals.We also investigate the effect of the interstitial position of the rhodamine B(RhB)molecule on Raman enhancement in Au/AgAu~3 heteronanostructures.This study can provide new ideas for the synthesis of multi-gap Raman signal amplifiers based on magnetic plasmon coupling.