Narrow Results

Facile, controllable and efficient SERS substrate preparation has always been the focus project in the SERS field, especially the solid-state nanoarray substrate. Herein, a simple and convenient method for preparing a series of homogeneous Ag-stepped nanocone arrays (Ag-SNCAs) using polymer nanocompression printing is presented. By analyzing the 1162cm${}^{-1}$ characteristic peak of crystal violet (CV), the relative standard deviation (RSD) of the Raman intensity was only 4.71%. The detection limit of malachite green (MG) reached 0.001ppm, and it also has good SERS detection results for drug molecules such as melamine, methadone, morphine, methamphetamine and thiabendazole. This work provides a large area uniform and controllable preparation method of sharp cone nanostructure array, which has important application in plasmonic photocatalysis and deep light field regulations.

In this work, Ag nanoparticles were deposited in the TiO${}_{2-X}$ nanotube films through magnetron sputtering to form Ag-TiO${}_{2-X}$ nanocomposite. Scanning electron microscopy (SEM) was used to study microstructure and surface morphology. Rhodamine B (RhB) was deposited on the surface of Ag-TiO${}_{2-X}$ substrate for Raman spectroscopy test. The size of Ag nanoparticles can be controlled by changing the magnetron sputtering time. The result indicated that sputtering for 30 s obtained the highest Raman enhancement.

We present a theoretical mechanism for electric field enhancement with SERS of InAs particles of subwavelength apertures under THz excitation. The distribution of electric field confirms that there is a strong enhancement in the InAs particles at THz frequencies. The InAs with a Drude-like behavior in THz range, which is similar to metals at optical frequencies, leads to different SERS when the parameters of these two particles change. The SERS enhancement factor can reach $10^{11}$ under the certain conditions.

Flexible surface enhanced Raman scattering (SERS) substrate was prepared by modification of sandpaper with silver nanoparticles. Under 633 nm excitation wavelength, the SERS enhancement effect of sandpapers which were treated with silver nanoparticles were evaluated by collecting Raman signals of probed molecules. The results demonstrate that the SERS enhancement effect of white (12,000 meshes) is better than that of pink (8000 meshes) sandpaper under the same condition; when the concentration of probe molecules is $10^{-4}$ mol/L, white sandpaper has the best SERS enhancement; the Raman scattering spectrum has better signal when the silver sol is 15 $\mu \mathrm{\text{L}}$.

To explore the strong coupling between the combined plasmonic mode supported by the metal nanoparticle and the anapole mode of the dielectric nanoparticle, a hybrid metal–dielectric nanoparticle consisting of the combination of silicon and silica together with the gold dimer is designed and analyzed by the finite element method (FEM). Theoretical simulation reveals that the enhanced electric field enhancement reaches 640 and unidirectional scattering with almost zero backscattering at multiple wavelengths is achieved in the far-field region. Moreover, the calculated Purcell factor of 12,193 and sensitivity of 610nm/RIU of the composite nanoparticle are much higher than those of the single-metal or dielectric nanoparticles. In the end, the impact of different structural parameters on the sensitivity, figure of merit and quality factor is analyzed and described, and the maximum sensitivity, Figure of merit and quality factor are found to be 2360nm/RIU, 18.4 RIU${}^{-1}$ and 19.8 RIU${}^{-1}$. The results reveal a new strategy to develop devices for surface-enhancement Raman scattering (SERS), quantum emitters, and sensors.

Bimetallic nanostructure of noble metals is an alternative material that can provide the tenability of plasmonic performance. In this study, the plasmonic silver–titanium nanoisland (Ag–Ti NI) films deposited on a silicon wafer and glass slide substrates were prepared by magnetron co-sputtering of high-purity Ag target (99.99%) operated at 100 W-DC source, and Ti target (99.99%) operated at 50–250 W-DC pulsed source. The surface morphologies of the prepared films revealed a noncontinuous island Ag–Ti according to the formation of thin film growth based on the Volmer–Weber model. An increase in the sputtering power of the Ti target caused an evident increase in the Ag–Ti NIs diameter. The localized surface plasmon resonance (LSPR) was evaluated by UV–Vis–NIR spectrophotometry. The LSPR peak shift disappears with an increase of the sputtering power of the Ti target.In addition, the results confirmed that the surface-enhanced Raman scattering (SERS) activity of the bimetallic Ag–Ti NIs significantly improved in performance and stability, which is promising for the application in analytical chemistry.

In this paper, we investigate the impact of rice-starch stabilization of gold nanoparticles (AuNPs) on their catalytic and surface-enhanced Raman spectroscopy (SERS) activities. A typical green synthesis protocol was used to prepare AuNPs with rice-starch functioning as the reductant and the stabilizer. The localized surface plasmon resonance (LSPR) of the starch-stabilized AuNPs is pH-sensitive and got red-shifted with the medium’s pH. The average size of the AuNPs formed decreased with the amount of rice-starch up to a certain level. TEM result shows that the polymeric behavior of starch extract may help synthesize the Au nanorod morphologies. AuNPs stabilized by different amounts of rice-starch were applied as the catalysts for the model $p$-nitrophenol reduction reaction. For all AuNP catalysts used, the reaction followed pseudo-first-order kinetics. The catalyst turnover frequencies increased up to a certain level of starch functionalization. Further increase in starch led to a fall in the activity of AuNPs catalyst. The evidence on rate kinetics, induction times, activation energies, and turnover frequencies is combined to explain this phenomenon in terms of starch content. The SERS response of these AuNPs as substrates has also been investigated for methylene blue as the target molecules. AuNP substrates with an excess amount of starch weaken the SERS response and it can be ascribed to decreased light scattering efficiency of NPs as well as reduced interactions of methylene blue molecules with the NP surface.

We study synthesis and SERS activity of glass-embedded ion-exchanged silver nanoparticles formed by two different methods. Silver-sodium ion-exchange process with heat treatment was utilized on commercial microscope slides, while masked ion-exchange technique was performed on glass Corning 0211. The distribution of particles was studied by absorption spectroscopy and atomic force microscopy. After etching the glass surface to expose the particles, SERS performance of these particles was investigated with micro-Raman spectroscopy using Rhodamine 6G as the analyte.

An Overview of Biopharma Industry in China – Featuring Mr. Ling Zhen, Head of Greater China, Quintiles.

L'Oréal Singapore Awards 2015 For Women In Science National Fellowships.

The International Peptide Symposium Held in Singapore for the First Time.

Inspirations from 2015 FWIS L'Oréal Winners.

Emerging Opportunities in Myanmar's Diagnostic Imaging and In Vitro Diagnostics.

Nobel Laureate Cooperates with Infinitus to Explore the Potential Roles of TCM in Immune Regulation.

XW Labs Announces Exclusive Licensing Agreement with University of Pittsburgh to Develop Novel Mitochondria-Targeting Compounds.

Genetically-Engineered Malaria Vaccine May be Used in Liver Cancer Immunotherapy.

Magellan Diagnostics and PDXWildlife Partner to Identify Lead Exposure in Giant Pandas.

China Able to Detect 300 Known Pathogens within 72 Hours.

BioVentrix Announces the 1st Revivent TC™ TransCatheter Commercial Procedure to Treat Ischemic Cardiomyopathy in China.

New Superbug Could Be Epidemic.

Functional Circuits Regulate Activity of Serotonergic Neurons.

SERS Helps to Evaluate DHA Effect on Cancer Cells.

China Building World’s Largest Multifunctional Nano Research Facility.

Chinese Researchers Reveal a New Antiviral Defense Mechanism in Rice.

We report on the plasmonic properties of silver-coated dielectric nanocylinders arranged according to an unconventional geometrical representation called Pascal's triangle. We performed numerical simulations to calculate the extinction spectrum and identify the collective optical modes in the geometry. For resonant excitation at 410 nm, we found pronounced field localization (50 nm) at the center of the Pascal triangle. Further, we studied the near-field intensity as a function of experimentally-relevant variables such as excitation wavelength, angle of incidence and dielectric constant of the core material. Our analysis revealed pronounced difference between near-field intensities for resonant and non-resonant excitation wavelength at various angle of incident radiation; and an increment in near-field intensity at excitation wavelengths greater than 600 nm, with increase in dielectric constant of core material. Our study has relevance in development of substrates with tunable electromagnetic hot-spots for on-chip plasmonics.

Gold nanostructures were fabricated in porous SiO₂/Si ion-track templates by the wet chemical deposition from a solution of Au(I) sulfite complex. Their morphological features were analyzed, and features of the deposition processes were determined. A mechanism describing the selective formation of gold nanostructures in the pores of SiO₂ was proposed. The present approach allows us to control shape and size of Au nanostructures those which can be used as plasmonic active surfaces for SERS detecting of small amounts of biological and chemical substances.

Copper nanostructures demonstrating an activity in the surface-enhanced Raman scattering (SERS) spectroscopy were formed via electrochemical deposition of copper on porous aluminum oxide (PAO) and protected from oxidation by surface coverage with polyethylene glycol (PEG) and silver. The SERS measurements of 10${}^{-6}$-M 4-mercaptophenylboronic acid (MPBA) molecules adsorbed on fresh Cu-coated samples, Cu–PEG and Cu–PEG–Ag nanocomposites after 5, 10, 15, 60, 180 and 300min of storage in air indicated the effectiveness of the proposed approach in protection from oxidation.

Four new meso-tetraphenylporphyrin derivatives were prepared, singly and doubly substituted with thiocarbamate and thioacetate groups. These compounds were subsequently attached to gold nanoparticles suspended in chloroform. Very different kinetics of the attachment were revealed; the process was much faster for the thiocarbamate derivatives. Spectral, photophysical, and scanning electron microscopy studies revealed large differences in the morphology of the gold–porphyrin systems. The porphyrins with one linker attach to single nanoparticles, whereas the dual linker derivatives induce formation of aggregates, characterized by readily detectable Raman signals. A "hot-spot" type structure is proposed for the latter, with the porphyrin bridging two gold nanoparticles.

Silver nanoparticles (NPs) films with different nominal thicknesses were deposited on the anodic aluminum oxide (AAO) templates with pore diameter about 200 nm by thermal evaporation. These NPs films were used as the surface enhanced Raman scattering (SERS) active substrates. The microstructure and surface morphology of the films were studied by X-ray diffraction and scanning electron microscopy, respectively. The SERS activity of the films was investigated by Raman scattering of adsorbed rhodamine 6G (R6G) at different concentrations. The results revealed that the average diameter of Ag NPs in different samples is 58 nm, 75 nm, 93 nm and 108 nm, respectively. Ag NPs film on AAO template is very suitable as a SERS active substrate and can detect R6G molecules with a concentration of 10^-8 M. The intensity of the SERS spectra is related to both the Ag NPs size and interparticle distance. The sample with an average particle diameter of 93 nm has the highest SERS enhancement factor (1.3 × 10⁶).

A series of monodisperse Ag nanoparticles (Ag NPs), whose size can be tuned between 2 nm and 34 nm, have been successfully synthesized in one pot by controlling the growth time. The standard deviation of the small-size Ag NPs is 12% while that of the large-size ones is 15%. During the synthesis process, sodium borohydride and sodium dodecyl sulfate were used as reducing agent and surfactant, respectively, and the effect of the synthesis parameters on the size-tuning range and the size distribution of Ag NPs was studied to get the optimum growth condition. Moreover, surface enhanced Raman scattering (SERS) spectra were analyzed to explore the synthesis mechanism of Ag NPs.

High-ordered particle-in-bowl (PIB) arrays are developed in this paper for surface enhanced Raman spectroscopy (SERS). A heterogeneous shadow mask, composing of the chrome (Cr) layer and colloid residues, is used to fabricate the silicon (Si) template from where the PIB arrays finally lift-off. The finite difference time domain (FDTD) method is employed to investigate the Raman enhancement mechanism of this PIB architecture. The electromagnetic (EM) field tends to concentrate in the gap between the bowl and the particle forming the "hot spots". The enhancement factor (EF) of the EM field is about 70 with an excitation wavelength of 785 nm. The Raman measurements validate the EM calculation of the PIB arrays. The EF is about 1.12 × 10⁷ using Rodamine 6G (R6G) as probe molecule. The proposed PIB array is high-ordered in morphology and ultra-sensitive in Raman measurement, providing an ideal substrate for SERS-based bio-chemical sensing, disease diagnosis and analytical chemistry.

A precipitation–reduction synthesis method for silver nanoparticles (Ag NPs) was developed. Molten ε-caprolactam (CL) was used not only as solvent but also as reducing agent and stabilizer. At first, Ag₂O NPs was prepared by precipitation reaction of silver nitrate (AgNO₃) and sodium hydroxide (NaOH) using molten CL as solvent at 100°C. Then, Ag₂O NPs was in situ reduced into Ag NPs by molten CL at 120°C. Techniques of X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to monitor the synthesis process. With the increase of reduction time, monodispersed Ag₂O NPs (ca. 3.7 nm) were integrated and larger Ag NPs (10–90 nm) were formed. Fourier transform infrared (FT-IR) results showed that the surface of Ag NPs was capped with about 0.9 wt.% of CL molecules. Surface enhanced Raman scattering (SERS) effect of Ag NPs was investigated using Rhodamine 6G as a probe molecule.

Bimetallic silver–gold composites are currently among the most studied substrates for detection based on surface-enhanced Raman scattering (SERS). Here, we developed Au–Ag composite films as high sensitivity, large-scale, chemically stable and reproducible SERS substrates. Au–Ag composite films were fabricated by chemical etching of Ag–Au alloy leaves with HAuCl₄ aqueous solutions. Along with galvanic replacement reaction and dealloying, films with distinct microstructural features exhibit dramatic improvement in the SERS intensity. Especially, the Au–Ag composite films with legible nano-ridges fabricated by alloy leaves of 9 carat present the strongest SERS enhancement. The superior SERS enhancement is attributed to the confluence effect of enhanced local surface plasmon fields and electromagnetic coupling within nanogaps, sharp edges and corners. In addition, results showed that features of the films mightily depend on the initial proportions of Ag–Au alloys.