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.

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.

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.

Rapid Identification of Legionella Pathogenicity by Surface-Enhanced Raman Spectroscopy

Objective To establish Surface-enhanced Raman Spectroscopy（SERS） can be used as a rapid and reliable method to distinguish virulent strain and mild strain of L. pneumophila. Methods We isolated and characterized of bacterial strains from ATCC and water samples strains, while we analyzed data from SERS technology using gold nanoparticles as a base and cell infections were employed to rapidly detect L. pneumophila strains. Origin 8.0 was used to collect Raman spectra, smooth and homogenize data, and to contrast spectra. Principal component analysis（PCA） was conducted to discriminate differences between groups using the multivariate analysis package Py Chem 3.0.5. Results Our results indicated that the peaks of high virulence strains reached ≥4000. This criterion was verified by subsequent cell experiments. In addition, we also conducted SERS rapid identification on the virulence of several collected clinical strains and obtained accurate results. Conclusion The present study indicates that the established SERS protocol can be used as a rapid and reliable method to distinguish virulent and mildly virulent strains of L. pneumophila, which can be further used in clinical samples.

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.

DNA origami-templated assembly of plasmonic nanostructures with enhanced Raman scattering

DNA origami have been established as versatile templates to fabricate plasmonic nanostructures in predefined shapes and multiple dimensions. Limited to the size of DNA origami, which are approximate to 100 nm, it is hard to assemble more intricate plasmonic nanostructures in large scale. Herein, we used rectangular DNA origami as the template to anchor two 30-nm gold nanoparticles(Au NPs) which induced dimers nanostructures. Transmission electron microscopy(TEM) images showed the assembly of Au NPs with high yields. Using the linkers to organize the DNA origami templates into nanoribbons,chains of Au NPs were obtained, which was validated bythe TEM images. Furthermore, we observed a significant Raman signal enhancement from molecules covalently attached to the Au NP-dimers and Au NP-chains. Our method opens up the prospects of high-ordered plasmonic nanostructures with tailored optical properties.

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 nanopartides 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-partide nanogaps. The proposed SERS substrate was demonstrated to have a sensitivity of 10-12 M, reliable reproducibility, and good stability.

One-step Synthesis of Shape-controllable Gold Nanoparticles and Their Application in Surface-enhanced Raman Scattering

Gold nanoparticles （NPs） of various shapes were synthesized by a one-step method at ambient temperature in the presence of NaCl. 2-mercaptosuccinic acid （MSA） was used as both reducing agent and stabilizing agent. The shapes of gold NPs were controllable by simply tuning S/Au ratio （S is from MSA molecule, and S/Au ratio is controlled by tuning the volume of added MSA solution）, and triangle, polygonal and spherical nanoparticles were obtained. This result suggested a new way to consider the effects of MSA on the growth of nanoparticles, which showed that MSA is a strong capping agent and facilitates more uniform growth of nanoparticles in every dimension. And other important factors on nanoparticles growth including NaCl and temperature were discussed. Furthermore, a typical probe molecule, 4-aminothiophenol （4-ATP） was used to test the surface-enhanced Raman scattering （SERS） activity of these gold NPs and the results indicated good Raman activity on these substrates. And the enhancement factor （EF） at 1078 cm^- 1 （a1） was estimated to be as large as 6.3 × 10^4 and 5.5 × 10^4 for triangular plates and truncated particles, respectively.

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.

Green synthesis of MIL⁃101/Au composite particles and their sensitivity to Raman detection of thiram

Metal⁃organic framework(MOF)MIL⁃101 and surface plasmon polariton(SPP)supported gold nanoparti⁃cles(Au NPs)hybrid systems were developed as a highly sensitive and reproducible surface⁃enhanced Raman scat⁃tering(SERS)detection platform,in which a green electrostatic self⁃assembly technology was adopted to construct the substrate.In an aqueous solution,the electronegativity of the particles can be used to prepare the composite sub⁃strate without any surface modifier.Due to the enrichment capacity of MIL⁃101 and the electromagnetic enhance⁃ment from Au NPs,the well⁃designed MIL⁃101/Au composites possessed ultrahigh sensitivity with the detection limit of Rhodamine 6G(R6G)as low as 10^(-10) mol·L^(-1).Meanwhile,the substrate exhibits high stability,excellent reproduc⁃ibility,and recyclability.Additionally,the novel substrate can be explored for direct capture,and sensitively detect pesticide residues such as thiram.

Convective Assembly of Linear Gold Nanoparticle Arrays at the Micron Scale for Surface Enhanced Raman Scattering

A convective assembly technique at the micron scale analogous to the writing action of a ＂pipette pen＂ has been developed for the linear assembly of gold nanoparticle strips with micron scale width and millimeter scale length for surface enhanced Raman scattering （SERS）. The arrays with interparticle gaps smaller than 3 nm are hexagonally stacked in the vicinity of the pipette tip. Variable numbers of stacked layers and clean surfaces of the assembled nanoparticles are obtained by optimizing the velocity of the pipette tip. The SERS properties of tile assembled nanoparticle arrays rely on their stacking number and surface cleanliness.

Applications of magnetic nanoparticles in surface-enhanced Raman scattering(SERS)detection of environmental pollutants

Environmental pollution, a major problem worldwide, poses considerable threat to human health and ecological environment. Efficient and reliable detection technologies, which focus on the appearance of emerging environmental and trace pollutants, are urgently needed. Surface-enhanced Raman scattering(SERS) has become an attractive analytical tool for sensing trace targets in environmental field because of its inherent molecular fingerprint specificity and high sensitivity. In this review, we focused on the recent developments in the integration of magnetic nanoparticles(MNPs) with SERS for facilitating sensitive detection of environmental pollutants. An overview and classification of different types of MNPs for SERS detection were initially provided, enabling us to categorize the huge amount of literature that was available in the interdisciplinary research field of MNPs based SERS technology. Then, the basic working principles and applications of MNPs in SERS detection were presented. Subsequently, the detection technologies integrating MNPs with SERS that eventually were used for the detection of various environmental pollutions were reviewed. Finally, the advantages of MNP-basedSERS detection technology for environmental pollutants were concluded, and the current challenges and future outlook of this technology in practical applications were highlighted. The application of the MNPsbasedSERS techniques for environmental analysis will be significantly advanced with the great progresses of the nanotechnologies, optics, and materials.

Covalentimmobilization of oligoDNA on the surface of magnetic nanoparticles and surface-enhanced Raman scattering study

The DNA magnetic nanoparticles are poten-tially useful in isolating and purifying DNA or RNA, direct-ing-target-medicines, the development of DNA biosensors and biochips. Surface functionalized magnetic nanoparticles with monodispersed shape and size were prepared by coating nano-sized g-Fe2O3 with silica in reverse microemulsion, and then thiol-compounds were immobilized onto the magnetic nanoparticles. After immobilizing oligoDNA modified with thiol-disulfide on the surface of the fictionalized magnetic nanoparticles, we obtained DNA-magnetic nanoparticles. The efficiency of the single-linking probes loading at the surfaces of magnetic nanoparticles was examined via hy-bridization experiment. Surface-enhanced Raman scattering methods were also effectively applied to observing the immobilization and hybridization processes mentioned above. The results demonstrated oligoDNA being availably connected to the surface of the magnetic nanoparticles.

Detection of chlorpyrifos in apples using gold nanoparticles based on surface enhanced Raman spectroscopy

In this study,gold nanoparticles(AuNPs)were synthesized for rapid and sensitive characterization and quantification of chlorpyrifos in apples.Min-max signal adaptive zooming and second derivative transformation method were adopted to pre-process Raman spectral signal.The min-max signal adaptive zooming method showed a higher correlation coefficient than derivative transformation when developing linear calibration curve between chlorpyrifos pesticide and Raman spectral peak intensity.The present method had a high reproducibility with the relative standard deviation less than 15%.Regression models showed a good linear relationship(R=0.962)between intensity of characteristic spectral peaks(at 677 cm-1)and chlorpyrifos concentration on whole apples ranging from 0.13 mg/kg to 7.59 mg/kg.The application of surface enhancement Raman spectroscopy(SERS)detected chlorpyrifos pesticide to the detection limit of 0.13 mg/kg,which can be applied further for lower concentration in the future.The method presented in this study can provide a way-out for detection of pesticide residue in whole apple to trace amount.

A Sensitive Surface-enhanced Raman Scattering Method for Determination of Melamine with Aptamer-modified Nanosilver Probe

The small nanosilver was prepared by the sodium borohydride procedure. The aptamer was used to modify nanosilver to obtain a nanosilver-aptamer （AgssDNA） SERS probe for the determination of melamine. In pH 6.6 phosphate buffer solution and in the presence of NaCI, the AgssDNA probe specifically combined with melamine to release nanosilver particles that were aggregated to nanosilver clusters, which exhibited SERS effect at 240 cm-1. When melamine concentration increased, the nanosilver clusters increased, and the SERS intensity at 240 cm-1 in- creased. The increased SERS intensity AI240cm, is linear to melamine concentration in the range of 6.3--403.6 μg.L 1, with a detection limit of 1.2 μg L 1. This assay was applied to determination of melamine in milk, with sat- isfactory results. Keywords melamine, apatmer-modified nanosilver, aggregation, surface-enhanced Raman scattering

A facile route to the hierarchical assembly of Au nanoparticles on carbon nanotubes through Cu^(2＋) coordination for surface-enhanced Raman scattering

We report the hierarchical assembly of Au nanoparticles on carboxylized carbon nanotubes（c-CNTs）through Cu^（2＋） coordination. This route is facile and green, and can easily control the loading density of Au nanoparticles. The c-CNT matrix ensures uniform distribution of Au nanoparticles, which is particularly important for the enrichment of hot spots while preventing their serious agglomeration. Moreover, the cCNT matrix also contributes to the electromagnetic enhancement due to its surface plasmon resonance,and the chemical enhancement due to the adsorption of the target molecules. The resulting Au@c-CNT nanohybrids exhibit a remarkable synergy in SERS compared to neat Au nanoparticles.

Synthesis of magnetic polyphosphazene-Ag composite particles as surface enhanced Raman spectroscopy substrates for the detection of melamine

Magnetic polyphosphazene(MPZS) particles coated by Ag nanoparticles(MPZS-Ag) have been developed as surface enhanced Raman spectroscopy(SERS) substrates for sensitive detection of melamine in aqueous solutions and milk samples.5,5’-Dithiobis-(2-nitrobenzoic acid)(DTNB) was used as model analyte to test the SERS activity of the MPZS-Ag particles.The prepared MPZS-Ag particles possess both magnetic responsiveness and excellent SERS properties.SERS detection of different concentrations of melamine aqueous solutions and spiked milk samples were performed by the MPZS-Ag particles.The limit of detection(LOD) of the melamine in aqueous solutions was 10^-7 mol/L(0.0126 mg/L) and 0.6 mg/L in real milk samples using the MPZS-Ag particles as SERS substrates.The LOD of the melamine are much lower than the safety values of Food and Drug Administration and Codex Alimentarius Commission.These results indicate that the MPZS-Ag particles have promising application prospect for SERS analysis in food safety fields.

Fundamental studies on enhancement and blinking mechanism of surface-enhanced Raman scattering （SERS） and basic applications of SERS biological sensing

We review recent our results in the fundamental study of surface-enhanced Raman scattering （SERS） with emphasis on experiments that attempted to identify the enhancement and blinking mechanism using single Ag nanoparticle dimers attached to dye molecules. These results are quantitatively discussed in the framework of electromagnetic mechanism. We also review recent our results in basic SERS applications for biological sensing regarding detections of cell surface molecules and distinction of disease marker molecules under single cell and single molecule level.

Ag nanowire/nanoparticle-decorated MoS2 monolayers for surface-enhanced Raman scattering applications

Developing well-defined nanostructures with superior surface-enhanced Raman scattering （SERS） performance is a critical and highly desirable goal for the practical applications of SERS in sensing and analysis. Here, a SERS-active substrate was fabricated by decorating a MoS2 monolayer with Ag nanowire （NW） and nanoparticle （NP） structures, using a spin-coating method. Both experimental and theoretical results indicate that strong SERS signals of rhodamine 6G （R6G） molecules can be achieved at ＂hotspots＂ formed in the Ag NW-Ag NP-MoS2 hybrid structure, with an enhancement factor of 106. The SERS enhancement is found to be strongly polarization dependent. The fabricated SERS substrate also exhibits ultrasensitive detection capabilities with a detection limit of 10-11 M, as well as reliable reproducibility and good stability.

基于金纳米颗粒痕量沙丁胺醇的表面增强Raman散射光谱

用优化的Turkevich方法制备直径为50~60nm的金纳米颗粒,并通过表面增强Raman散射技术检测浓度为10^(-3)~10^(-5) mol/L的痕量沙丁胺醇分子.结果表明:最低检出限为5×10^(-5) mol/L,在100~750μmol/L范围内,Raman光谱强度与浓度具有较好的线性关系,相关系数R^2=0.996 57,但在更宽泛的浓度范围内不满足线性关系;基于金纳米颗粒表面增强Raman散射光谱方法可实时、快速检测痕量沙丁胺醇分子.