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.

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.

Hybrid metal-insulator-metal structures on Si nanowires array for surface enhanced Raman scattering

Surface enhanced Raman scattering(SERS)is an efficient technique to detect low concentration molecules.In this work,periodical silicon nanowires(Si NWs)integrated with metal-insulator-metal(MIM)layers are employed as SERS substrates.Laser interference lithography(LIL)combined with reactive ion etching(RIE)is used to fabricate large-area periodic nanostructures,followed by decorating the MIM layers.Compared to MIM disks array on Si surface,the SERS enhancement factor(EF)of the MIM structures on the Si NWs array can be increased up to 5 times,which is attributed to the enhanced electric field at the boundary of the MIM disks.Furthermore,high density of nanoparticles and nanogaps serving as hot spots on sidewall surfaces also contribute to the enhanced SERS signals.Via changing the thickness of the insulator layer,the plasmonic resonance can be tuned,which provides a new localized surface plasmon resonance(LSPR)characteristic for SERS applications.

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.

Molybdenum Nanoscrews:A Novel Non-coinage-Metal Substrate for Surface-Enhanced Raman Scattering

For the first time, Mo nanoscrew was cultivated as a novel non-coinage-metal substrate for surface-enhanced Raman scattering(SERS). It was found that the nanoscrew is composed of many small screw threads stacking along its length direction with small separations. Under external light excitation, strong electromagnetic coupling was initiated within the gaps, and many hot-spots formed on the surface of the nanoscrew, which was confirmed by high-resolution scanning near-field optical microscope measurements and numerical simulations using finite element method. These hotspots are responsible for the observed SERS activity of the nanoscrews. Raman mapping characterizations further revealed the excellent reproducibility of the SERS activity. Our findings may pave the way for design of low-cost and stable SERS substrates.

Raman and Surface-enhanced Raman Scattering of Chlorophenols

Raman spectrum is a powerful analytical tool for determining the chemical information of compounds. In this study, we obtained analytical results of chlorophenols（CPs） molecules including 4-chlorophenol（4-CP）, 2,6-dich- lorophenol（2,6-DCP） and 2,4,6-trichlorophenol（2,4,6-TCP） on the surface of Ag dendrites by surface-enhanced Raman scattering（SERS） spectra. SEM images indicate that the SERS substrate of Ag dendrites is composed of a large number of polygonal nanocrystallites, which self-assembled into a 3D hierarchical structure. It was found that there were distinct differences for those three molecules from Raman and SERS spectra. This indicates that SERS could be a new tool of detection technique regarding trace amounts of CPs.

Controllable Silver Plating on Silica for Surface-enhanced Raman Scattering

We proposed a facile and rapid method for preparing silica-silver core-shell（SSCS） substrates to use Ag electroless plating on SiO2@Au-seed particles.UV-Vis-NIR absorption spectrometer and SEM were employed to monitor the reaction process of the formation of Ag on the surfaces of silica beads,and the optical resonance of the substrate could shift from visible to NIR region.It has been found that surface-enhanced Raman scattering（SERS） enhancement changes with the electroless plating time and the SSCS substrate with the plating time of 90 s（90SSCS） shows the strongest SERS response under the laser excitation at 514.5 nm.Signals collected over multiple spots and substrate of rhodamine 6G（R6G） resulted in a relative standard deviation（RSD） of 9.75%.The calculated enhancement factor（EF） was approximately 105 ＂106.SSCS substrate exhibits high SERS performance,which is due to electromagnetic SERS enhancement with additional localization field within closely packed Ag nanoparticles decorated on the SiO2 nanoparticles.And this substrate presents tunable and broad localized surface plasmon resonance（LSPR）,so this method may open a new way for SERS studies with other laser excitation.

Quantitative and sensitive detection of prohibited fish drugs by surface-enhanced Raman scattering

Rapid and simple detections of two kinds of prohibited fish drugs, crystal violet （CV） and malachite green （MG）, were accomplished by surface-enhanced Raman scattering （SERS）. Based on the optimized Au/cicada wing, the detectable concentration of CV/MG can reach 10-7 M, and the linear logarithmic quantitative relationship curves between log/and logC allows for the determination of the unknown concentration of CV/MG solution. The detection of these two analytes in real environment was also achieved, demonstrating the application potential of SERS in the fast screening of the prohibited fish drugs, which is of great benefit for food safety and environmental monitoring.

Surface-enhanced resonance Raman scattering spectroscopy of single R6G molecules

Surface-enhanced resonance Raman scattering （SERRS） of Rhodamine 6G （R6G） adsorbed on colloidal silver clusters has been studied. Based on the great enhancement of the Raman signal and the quench of the fluorescence, the SERRS spectra of R6G were recorded for the samples of dye colloidal solution with different concentrations. Spectral inhomogeneity behaviours from single molecules in the dried sample films were observed with complementary evidences, such as spectral polarization, spectral diffusion, intensity fluctuation of vibrational lines and even ＂breathing＂ of the molecules. Sequential spectra observed from a liquid sample with an average of 0.3 dye molecules in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1 or 2 molecules. Difference between the SERRS spectra of R6G excited by linearly and circularly polarized light were experimentally measured.

Surface-enhanced Raman scattering on nanodiamond-derived carbon onions

Annealing nanodiamonds(ND) at high temperatures up to 1700 ℃ is a common method to synthesize carbon onions. The transformation from NDs to carbon onions is particularly interesting because of carbon onions' potential in the field of tribology and their application in ultra-charge/discharge devices. In this paper, a novel surface-enhanced Raman scattering technique that involves coating the sample with nanoscopic gold particles is proposed to characterize the NDs after different annealing treatments. Conventional Raman and surfaceenhanced Raman spectra were obtained, and the changes of peak parameters as the function of annealing temperature were evaluated. It was found that the widths of the D and the G peaks decreased with increasing annealing temperature, reflecting an improved order in the sp^2-hybridized carbon during the transformation from NDs to carbon onions. After annealing at 1700 ℃, the sp^2?carbon was highly ordered, indicating desirable electrical conductivity and lubricity. With increasing annealing temperature, the D peak showed a blue shift of almost30 cm^(-1), while the G peak merely shifted by 5 cm^(-1). For annealing temperatures above 1100 ℃, an increase of intensity ratio ID/IGwas observed. Compared to the uncoated area, red shifts of 0.5-2 cm^(-1) and of 5-9 cm^(-1) for the G and D peaks, respectively, were detected for the gold-coated area, which was due to the coupling of the plasmons and the phonons of the samples.

Preparation of nano-structured Ag solid materials and application to surface-enhanced Raman scattering

Silver nano-particles with average diameter of about 60 nm were compacted in a high-strength mold under different pressures at 523 K to produce nano-structured Ag solid materials. The structure and characteristic of the nano-structured Ag solid materials (NSS-Ag) were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectrometer. The NSS-Ag could be used as highly efficient surface-enhanced Raman scattering (SERS) active substrates. The common probe molecules Rhodamine 6G (R6G, 1×10-10 mol/L) were used to test the SERS activity on these substrates at very low concentrations. It is found that the SERS enhancement ability is dependent on the density of NSS-Ag. When the relative density of NSS-Ag is 83.87%, the materials reveal great SERS signal.

Selective synthesis of three-dimensional ZnO@Ag/SiO2@Ag nanorod arrays as surface-enhanced Raman scattering substrates with tunable interior dielectric layer

We describe the synthesis of three-dimensional(3D) multilayer ZnO@Ag/SiO2@Ag nanorod arrays by the physico–chemical method. The surface-enhanced Raman scattering(SERS) performance of the 3D multilayer Zn O@Ag/SiO2@Ag nanorod arrays is studied by varying the thickness of dielectric layer SiO2 and outer-layer noble Ag. The 3D Zn O@Ag/SiO2@Ag nanorod arrays create a huge number of SERS "hot spots" that mainly contribute to the high SERS sensitivity. The great enhancement of SERS results from the electron transfer between ZnO and Ag and different electromagnetic enhancements of Ag nanoparticles(NPs) with different thicknesses. Through the finite-difference time-domain(FDTD) theoretical simulation, the enhancement of SERS signal can be ascribed to a strong electric field enhancement produced in the 3D framework. The simplicity and generality of our method offer great advantages for further understanding the SERS mechanism induced by the surface plasmon resonance(SPR) effect.

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.

Comparison of Surface-enhanced Raman Scattering Spectra of Two Kinds of Silver Nanoplate Films

Surface-enhanced Raman scattering（SERS） spectra of different silver nanoplate selt-assembled tllmS at different excitation wavelengths were fairly compared. Shape conversion from silver nanoprisms to nanodisks on slides was in situ carried out. The SERS spectra of 4-mercaptopyridine（4-MPY） on these anisotropic silver nanopar- ticle self-assembled films present that strong enhancement appeared when the excitation line and the surface plasmon resonance（SPR） band of silver substrate overlapped. In this model, the influence of the crystal planes of silver na- noplates on SERS enhancement could be ignored because the basal planes were nearly unchanged in two kinds of silver nanoplate self-assembled films.

Surface-enhanced Raman scattering sensor based on fused biconical taper zone of optical fiber

In this paper, a novel surface-enhanced Raman scattering （SERS） sensor combined with fused biconical taper fiber （FBTF） and film coated with silver sols is proposed. This structure is designed to significantly increase the SERS active surface when the length of the taper is increased and the radius is reduced, since the penetration depth is inversely proportional to the taper radius and proportional to the taper length according to the fiber-optic evanescent-wave theory. Based on the SERS sensing principle, the feasibility of FBTF sensor is analyzed in this paper. As a result, the Raman spectrum of R6G is obtained from the fused biconical taper zone surface coating with the silver sols in our experiments. The detected concentration is up to 10-7mol/L.

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.

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.

An effective surface-enhanced Raman scattering template based on gold nanoparticle/silicon nanowire arrays

A large-scale Si nanowire array （SiNWA） is fabricated with gold （Au） nanoparticles by simple metal-assisted chemical etching and metal reduction processes. The three-dimensional nanostructured Au/SiNWA is evaluated as an active substrate for surface-enhanced Raman scattering （SERS）. The results show that the detection limit for rhodamine 6G is as low as 10-7 M, and the Raman enhancement factor is as large as 105 with a relative standard deviation of less than 25%. After the calibration of the Raman peak intensifies of rhodamine 6G and thiram, organic molecules could be quantitatively detected. These results indicate that Au/SiNWA is a promising SERS-active substrate for the detection of biomolecules present in low concentrations. Our findings are an important advance in SERS substrates to allow fast and quantitative detection of trace organic contaminants.

Perforated nanocap array: Facile fabrication process and efficient surface enhanced Raman scattering with fluorescence suppression

Recently, individual reduced-symmetry metal nanostructures and their plasmonic properties have been studied extensively. However, little attention has been paid to the approach to fabricating ordered reduced-symmetry metal nanostructure arrays. In this paper, a novel perforated silver nanocap array with high surface-enhanced Raman scattering （SERS） activity and fluorescence suppression is reported. The array is fabricated by electron beam evaporating Ag onto the perforated barrier layer side of a hard anodization （HA） anodic aluminum oxide （AAO） template. The morphology and optical property of the perforated silver nanocap array are characterized by an atomic force microscope （AFM）, a scanning electron microscope （SEM）, and absorption spectra. The results of SERS measurements reveal that the perforated silver nanocap array offers high SERS activity and fluorescence suppression compared with an imperforated silver nanocap array.

Ultraviolet-visible and Surface-enhanced Raman Scattering Spectroscopy Studies on Ruthenium Phthalocyanine Monolayer Films Formed on Terephthalonitrile-modified Silver Substrates

A self\|assembled monolayer film(SAM) of ruthenium phthalocyanine(RuPc) fabricated on a silver substrate premodified with an SAM of terephthalonitrile(TPN) was studied by means of surface\|enhanced Raman scattering(SERS) and ultraviolet\|visible(UV\|Vis) spectroscopies. TPN was used as a ligand to link RuPc since it can not only modify the silver substrate but also deliver the nitrile groups protruding from the silver surface. Therefore,we can explore the relationship between the structure and the orientation of RuPc and the TPN\|modified substrate. The UV\|Vis spectra indicate a strong interaction between RuPc and TPN in the composite film. The result is further confirmed by the SERS spectra of RuPc\|TPN SAM,in which the vibrational bands arising from both the RuPc and TPN moieties appear clearly,indicating that the RuPc is successfully assembled on the TPN film.