Excellent Surface-enhanced Raman Scattering Research Articles

Micro-nano hierarchical urchin-like ZnO/Ag hollow sphere for SERS detection and photodegradation of antibiotics

Abstract Hollow urchin-like substrates have been widely interested in the field of surface-enhanced Raman scattering (SERS) and photocatalysis. However, most reported studies are simple nanoscale urchin-like substrate with limited light trapping range and complicated preparation process. In this paper, a simple and effective controllable synthesis strategy based on micro-nano hierarchical urchin-like ZnO/Ag hollow spheres was prepared. Compared with the 2D structure and solid spheres, the 3D urchin-like ZnO/Ag hollow sphere has higher laser utilization and more exposed specific surface area due to its special hollow structure, which resulted in excellent SERS and photocatalytic performance, and successfully realize the detection and photodegradation of antibiotics. The limited of detection of metronidazole can reach as low as 10−9 M, and degradation rate achieve 89 % within 120 min. The experimental and theoretical results confirm that the ZnO/Ag hollow spheres can be used in the development of ZnO heterostructure for the detection and degradation of antibiotics, which open new avenues for the development of novel ZnO-based substrate in SERS sensing and catalytic application to address environmental challenges.

Ag nanoparticle in situ decorated on Ti3C2Tx with excellent SERS and EIS immunoassay performance for beta-human chorionic gonadotropin.

Two-dimensional transition metal carbides, nitrides, and carbonitrides (MXene), with excellent optical and electrical properties, are promising substrates for surface-enhanced Raman scattering (SERS) and electrochemical sensors. Therefore, a unique 3D-decorated structure containing silver (Ag) nanoparticles and Ti3C2Tx was designed as the substrates of SERS and electrochemical impedance spectroscopy (EIS) immunosensors. The Ag/Ti3C2Tx composite significantly increases Raman intensity, which is attributed to the synergistic effect of Ti3C2Tx and Ag nanoparticles. Based on the SERS performance of the Ag/Ti3C2Tx composite, the magnetic properties of Fe3O4 and the specificity of antigen-antibody, a sandwich-structured SERS immunosensor is constructed, which can effectively detect trace amounts of beta-human chorionic gonadotropin (β-hCG). The SERS immunosensor exhibits a wide linear range of 5.0 × 10-6-1.0 mIU mL-1, and a low detection limit of 9.0 × 10-7 mIU mL-1. Meanwhile, the Ag/Ti3C2Tx-based EIS immunosensor is constructed for the portable detection of β-hCG, which exhibits a wide linear range of 5.0 × 10-2-1.0 × 102 mIU mL-1, a low detection limit of 9.5 × 10-3 mIU mL-1. Moreover, two immunosensors can be used to detect actual serum samples withsatisfactory recovery (98.5-102.2%). This work could guide the design of low-cost, sensitive, flexible, and portable biosensors. The SERS and EIS substrates composited with Ti3C2Tx and Ag nanoparticles enable excellent performance for detecting β-hCG.

Synthesis of sea urchin-shaped Au nanocrystals by double-strand diblock oligonucleotides for surface-enhanced Raman scattering and catalytic application

It is of great significance to construct specially designed gold nanocrystals (AuNCs) with precisely controllable size and morphology to achieve an excellent physicochemical performance. In this work, sea urchin-shaped AuNCs with tunable plasmonic property were successfully synthesized by the hybridized double-strand poly adenine (dsPolyA) DNA-directed self-assembly technique. Hybridized dsPolyA as the directing template had suitable rigidity and upright conformation, which benefited the controllable formation of these anisotropic multi-branched AuNCs with the assistance of surfactant. The effects of essential conditions influencing the synthesis and precise morphology control were investigated in detail. COMSOL simulation was used to evaluate their electromagnetic field distribution according to their morphologies, and the result suggested that sea urchin-shaped AuNCs had abundant ‘hot spots’ for surface-enhanced Raman scattering (SERS) detection due to their regular nanoprotuberance structure. Finally, sea urchin-shaped AuNCs with excellent SERS and catalytic performance were applied for the quantitative analysis of food colorant and catalytic degradation of potential pollutants. The SERS enhancement factor of sea urchin-shaped AuNCs was up to 5.27 × 106, and the catalytic degradation rate for 4-NP by these AuNCs was up to −0.13min−1.

Synthesis of GO/Au/Ag Nanocomposite with Excellent Surface Enhanced Raman Scattering Effect

In this work, a nanocomposite (GO/Au/Ag) containing graphene oxide (GO) and Au/Ag nanoparticles was fabricated by in situ reduction for improved manipulation of their SERS effect. The uniform dispersion of Au/Ag nanoparticles were successfully generated on GO. Rhodamine 6G (R6G) as a Raman probe was used to investigate the SERS effect. Owing to the synergistic effect of the high localized surface plasmon resonance of Au/Ag, and chemical enhancement of GOs, the Raman intensities of R6G on GO/Au/Ag is several times as high as that on Au/Ag or GO/Au. GO/Au/Ag nanocomposites showed excellent Raman enhancement and appeared to be a kind of valuable material with potential application in SERS detection.

Multifunctional Reduced Graphene Oxide Wrapped Circular Au Nanoplatelets: Enhanced Photoluminescence, Excellent Surface-Enhanced Raman Scattering, Photocatalytic Water Splitting, and Non-Enzymatic Biosensor

Herein, we demonstrate the synthesis and multifunctional properties of reduced graphene oxide (RGO)-wrapped Au nanoplatelets. We have characterized the sample by field emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), energy-dispersive X-ray spectroscopy (EDS), high-angle annular dark-field scanning transmission electron microscopy (STEM-HAADF), electron energy-loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS) studies. It has been shown that the RGO wraps a large number of 2D circular Au nanoplatelets (diameter ∼15 nm). We have examined the optical property of the sample using Raman, UV–vis, and PL spectroscopic techniques. Large enhancement in intensity of Raman spectra was observed due to the surface enhanced Raman scattering (SERS) resulting from the Au nanoplatelets. The collective sway of surface plasmon resonance and fluorescence resonance energy transfer effect owing to Au gives rise to giant enhancement in intensity of phot...

Facile fabrication of ternary TiO2-gold nanoparticle-graphene oxide nanocomposites for recyclable surface enhanced Raman scattering

A bi-functional ternary nanocomposite was developed by decorating TiO2 and gold nanoparticles on the reduced graphene oxide nanosheets (TiO2-Au-rGO) for recyclable surface enhanced Raman scattering (SERS) detection. TiO2-Au-rGO nanocomposites have been shown to demonstrate the superior SERS performances, which can be used for highly sensitive detection of rhodamine 6 G with a limit of detection of 1.2 × 10−10 M. Subsequently, the surface can be cleaned automatically by the photocatalytic degradation of the adsorbed analytes into inorganic small molecules under visible light irradiation. This can be attributed to the excellent photocatalytic degradation ability, leading to a recyclable SERS application. After being used four times, their excellent SERS and catalytic performances can still be retained. These results suggest that the TiO2-Au-rGO nanocomposites can provide a new strategy for fabricating recyclable SERS substrates, which are highly desirable for SERS practical application.

Excellent Surface Enhanced Raman Scattering of SiO2 Fiber Membrane Embedded with Ag Nanoparticles

Uniformly distributed Ag nanoparticles supported on SiO2 fiber membrane materials were successfully synthesized using electrospinning and pyrolysis. In this study, the electrostatic spinning solution is composed mainly of polyvinyl pyrrolidone, ethyl silicate (TEOS) and AgNO3. The structural and morphological studies of the materials after calcination were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM) and thermogravimetric analysis–differential scanning calorimetry (TG–DSC). The results indicated that the samples had a rough surface structure. The load on the nanofibers was silver (Ag) metal, and the number and grain size of Ag nanoparticles increased as the relative amounts of AgNO3 increased. Furthermore, the surface enhanced Raman scattering (SERS) activity of the Ag/SiO2 was investigated using the common antibiotic enrofloxacin as a probe. It was found that the amorphous silica fiber with uniform loading of Ag nanoparticles exhibited a strong SERS enhancement effect. Due to the analytical performance, the predicted potential for SERS detection of trace antibiotics is excellent.

Surface modified graphene oxide nanosheets by gold ion implantation as a substrate for surface enhanced Raman scattering

Graphene oxide (GO) nanosheets are the nanoscale building blocks for stabilization of metal nanoparticles with new hybrid nanocomposite properties. Here, we report on GO nanosheets implanted with low energy gold (Au) ion induced reactive sites for nucleation and intercalation of Au particles in a few layers of GO nanosheets. The nucleation and intercalation mechanisms were dependent on the doses of implanted Au ions in GO nanosheets. Atomic force microscopy (AFM) and Raman analysis of Au ion implanted GO nanostructure showed surface roughening and altered surface chemical states in GO nanostructure. We also observed that Au ion implantation induced reduction of GO surface as confirmed by X-ray diffraction (XRD) analysis and enhanced current-voltage (I-V) characteristics. Our study also indicated that the Au implanted-GO nanocomposites exhibited excellent surface enhanced Raman scattering (SERS) effects which can be used as an excellent SERS substrate.

Hollow Gold Nanoprism as Highly Efficient “Single” Nanotransducer for Surface-Enhanced Raman Scattering Applications

In this Article, we report the optical properties of anisotropic hollow nanostructure, hollow gold nanoprism (HGN, an equilateral triangular gold nanoprism with a circular cavity) and its application as a highly active “nonaggregated” surface-enhanced Raman scattering (SERS) substrate. Small colloidal HGNs are prepared using sacrificial galvanic replacement method. Our study reveals that HGNs are highly stable nanostructure in solution and robust against salt or ligand induced aggregation. We find that the LSPR spectra of the HGNs can be tuned by controlling their aspect ratios. Excellent SERS were detected from the J-aggregates of pseudoisocyanine dye, adsorbed on the HGN surface. Interestingly, strong SERS is obtained without the need of any aggregation of the nanoparticles. Numerical simulations reveal that a single HGN can not only harvest large local electromagnetic fields but also offer large sensing volume due to efficient plasmon hybridization, due to the presence of the cavity. This large sensing...

Biomimetic synthesis of highly biocompatible gold nanoparticles with amino acid-dithiocarbamate as a precursor for SERS imaging

Amino acid-dithiocarbamate (amino acid-DTC) was developed as both the reductant and ligand stabilizer for biomimetic synthesis of gold nanoparticles (AuNPs), which served as an excellent surface-enhanced Raman scattering (SERS) contrast nanoprobe for cell imaging. Glycine (Gly), glutamic acid (Glu), and histidine (His) with different isoelectric points were chosen as representative amino acid candidates to synthesize corresponding amino acid-DTC compounds through mixing with carbon disulfide (CS2), respectively. The pyrogenic decomposition of amino acid-DTC initiated the reduction synthesis of AuNPs, and the strong coordinating dithiocarbamate group of amino acid-DTC served as a stabilizer that grafted onto the surface of the AuNPs, which rendered the as-prepared nanoparticles a negative surface charge and high colloidal stability. MTT cell viability assay demonstrated that the biomimetic AuNPs possessed neglectful toxicity to the human hepatoma cell, which guaranteed them good biocompatibility for biomedical application. Meanwhile, the biomimetic AuNPs showed a strong SERS effect with an enhancement factor of 9.8 × 105 for the sensing of Rhodamine 6G, and two distinct Raman peaks located at 1363 and 1509 cm−1 could be clearly observed in the cell-imaging experiments. Therefore, biomimetic AuNPs can be explored as an excellent SERS contrast nanoprobe for biomedical imaging, and the amino acid-DTC mediated synthesis of the AuNPs has a great potential in bio-engineering and biomedical imaging applications.

Fabrication of silver nanoparticles decorated anodic aluminum oxide as the SERS substrate for the detection of pesticide thiram

An efficient surface-enhanced Raman scattering (SERS) substrate is developed based on silver nanoparticles decorated anodic aluminum oxide (Ag/AAO). The AAO templates were fabricated using a two-step anodization approach, and silver nanoparticles (AgNPs) were obtained by thermal decomposition of Ag nitrate in AAO. The structure of Ag/AAO hybrid substrate is characterized by scanning electron microscopy (SEM). The results show that the as-prepared SERS substrates consist of high-density AgNPs with sizes of tens of nanometers. The AgNPs are adsorbed on the surface of AAO template in the form of network structure which is called “hot spot”. The SERS enhancement ability of the nanostructure is verified using thiram as probing molecules. The limit of detection is as low as 1×10−9 mol/L. The results indicate that the as-prepared substrate possesses excellent SERS sensitivity, high stability and uniformity enhancement.

Ultrasensitive and reproducible surface-enhanced Raman scattering detection via an optimized adsorption process and filter-based substrate

Wih a view to improve the surface-enhanced Raman scattering (SERS) properties, including the sensitivity and uniformity, a simple and practical pretreatment method via optimizing the adsorption process of probe molecules and the morphology of SERS-active nanostructures was studied. Excellent SERS performances were obtained using this method such as high sensitivity (5 × 10−14 M rhodamine 6G, 1 × 10−8 M melamine), remarkable uniformity (∼9% relative standard deviation (RSD)) and reproducibility (∼10% RSD). Uniform and repeatable silver nanoparticle arrays were fabricated by an optimized filter-based method, which guaranteed the reliability of SERS detection. The SERS intensity was greatly improved by adjusting the adsorption capacity of the noble metal nanostructures, which has a linear relationship with the pH value of silver solution below 10. An accurate and reliable enhancement factor (EF) of 3.28 × 108 was calculated through the quantification of the adsorbed probe molecules. It is worth noting that the lifetime of the substrates prepared by this method could be prolonged to two months, which was definitely longer than other ordinary silver SERS substrates. The pretreatment method not only provided perfect SERS properties, but also made SERS a practical analysis tool because of its good homogeneity and ultralow detection limit.

Synthesis of Highly Ordered Silver Nanowire Arrays with SERS Activity

The highly ordered silver nanowire arrays were fabricated successfully by an easily produced and handled approach with the assistance of nanoporous anodized aluminum oxide(AAO) template. The silver nanowires with uniform diameters are highly ordered and parallel to each other. A broad UV-visible absorption band with a center at 401nm of silver nanowire arrays were detected. Optimized surface enhanced Raman scattering(SERS) signals of crystal violet molecules(CV) were recorded. It was found that the substrate exhibits strong enhancement properties due to the surface plasma resonance(SPR) of highly ordered silver nanowire arrays. The enhancement factor was calculated as 3.5×106. In addition, the results offered a simple technique in preparing highly ordered nanowire arrays which can be used as negative-refractive-index material as well as excellent SERS substrate.

Dilution Effect on Surface Enhanced Raman Scattering for Polybenzimidazole Adsorbed from Solutions

Abstract The concentration dependence of surface enhanced Raman scattering (SERS) of adsorbed polybenzimidazole on surfaces of silver has been investigated. It has been found that the spectral qualities are inversely proportional to the concentration of solutions applied. Excellent SERS spectral enhancement could be achieved for the sample applied from wt-0.03% solution. This phenomenon was termed as “dilution effect” on SERS spectrum of polymers. The observed phenomena are in accordance with Qian's proposal for the existence for coil shrinkage in dilute solution.

Surface Enhanced Raman Scattering Evidence for Existence of a Critical Concentration for Coil Shrinking in Poly(L-Histidine) Solutions

Abstract The concentration dependence of surface enhanced Raman scattering (SERS) of adsorbed poly-(L-histidine) on surfaces of silver has been investigated. It has been found that the spectral qualities are inversely proportional to the concentrations of solutions applied. Excellent SERS spectral enhancement could be achieved for the sample applied from wt-0.02% solution. This phenomenon was termed as “dilution effect” on SERS spectrum of polymers. The observed phenomena are in accordance with Qian's proposal for the existence of coil shrinkage in dilute solution.

Dilution Effect on Surface Enhanced Raman Scattering for Organic Disulfide Adsorbed from Solutions

Abstract The concentration dependence of surface enhanced Raman scattering (SERS) of adsorbed 4-aminophenyl disulfide on surfaces of silver and gold has been investigated. It has been found that the spectral qualities are inversely proportional to the concentration of solutions applied. Excellent SERS spectral enhancement and perpendicular orientation could be achieved for the sample applied from 4 × 10−6 M solution rather than that from 0.001 M solution. This phenomenon was termed as “dilution effect” on SEES spectrum.