Search

Highlights • SERS is an extremely useful method to detect adsorbed molecules which are covalently bonded to the metallic Ag-NP. • SERS signal of bpy was enhanced by the Ag-NP embedded in the novel niobium phosphate substrate, allowing the detection at the concentration of 10–6 M. • Niobium phosphate containing Ag-NP on their surface is a useful sensor substrate for SERS applications. Abstract Surface-enhanced Raman scattering (SERS) is one of the most sensitive methods for the detection of adsorbed molecules on the nanostructured coinage-metal surface. The enhancements in the order of 104–106 are routinely observed. Such an effect makes SERS spectroscopy a technique applicable to the study the adsorption of analytes in the submonolayer regime. Novel SERS sensors require novel substrates with high activity for great sensibility detection of different molecules applied in many fields, such as detections of narcotics, explosives, and molecules with biological interest. In this work, silver nanoparticles embedded in niobium lead-pyrophosphate glasses (Pb 2 P 2 O 7 -Nb 2 O 5 -Na 2 O) were prepared by ion exchange process, where silver ions were introduced into glass surface by Ag+/Na+ ion exchange (NaNO 3 :AgNO 3 batch), and reduced to metallic silver by heat treatment at glass transition temperature (ca. 480 °C). The new substrate was characterized by Raman spectroscopy, optical absorption, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Its application in SERS was demonstrated by studying the adsorption of 2,2-bipyridine (bpy) on the glass surface, which has marker bands for the coordination of the adsorbate with silver atoms. The optimal surface features in terms of SERS enhancement were also discussed and the sensing ability of this new substrate was demonstrated. [ABSTRACT FROM AUTHOR]

A systematic study was carried out demonstrating that surface concentration is the key factor that must be controlled to overcome the reproducibility problems that has long been haunting surface enhanced Raman spectroscopy (SERS), converting it in a quantitative analytic tool without using any internal standard. The 1,10-phenanthroline molecule (phen) used as model compound can assume different orientations on the surface as a function of surface concentration, but a linear response as a function of concentration was realized in a well-defined range of gold nanoparticles (AuNPs) and phen concentration ratios, allowing to fully explore the very high sensitivity of SERS technique. A detection at a low concentration (5.0 × 10−8 mol dm−3) was achieved controlling the surface concentration in the optimum range where the signals of the species of analytic interest are maximized whilst the signals of all other species are minimized. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering spectroscopy method coupled with colloidal gold was used to detect and characterize phosalone pesticide in pakchoi. Theoretical and experimental Raman spectra were compared to analyze and identify the assignment of vibrations. Pakchoi samples containing phosalone pesticide residues were prepared and extracted for Raman spectra acquirement and gas chromatography-mass spectrometry measurement. A statistical regression analysis method was applied for the detection of phosalone residues. This analytical method was validated by predicted recovery and the paired-samplesTtest with five unknown samples. This study demonstrates that surface-enhanced Raman scattering (SERS) method is capable of detecting phosalone residues in pakchoi quickly and accurately. [ABSTRACT FROM AUTHOR]

In this work the adsorption of the antibiotics levofloxacin (LV), tetracycline (TC) and benzylpenicillin (BP) on the surface of silver nanoparticles (AgNP) have been investigated through both surface-enhanced Raman scattering (SERS) and UV–VIS–NIR spectroscopies. The SERS spectra were obtained using 1064 nm exciting radiation. Theoretical models for the antibiotic molecules were obtained from DFT calculations, and used in the vibrational assignment. The adsorption geometries were proposed based on the changes in the spectral patterns. The LV compound adsorbs through carboxylate group, TC compound interacts with silver atoms through carbonyl from intermediate ring, and BP compound adsorbs by carbonyl moieties from carboxylate and acyclic amide. [ABSTRACT FROM AUTHOR]

Recyclable and sensitive surface-enhanced Raman scattering (SERS) sensors for the detection of a variety of organic pollutants were fabricated from 3D hierarchical ZnO-Ag hybrids, which were synthesized by an efficient and green approach. The ZnO nanostructure could be controlled by applying a facile organic-chemical-assisted hydrothermal method. The obtained structures were then decorated with different-sized Ag nanoparticles (Ag NPs) on their side surfaces and top ends to construct 3D hierarchical ZnO-Ag nanocomposites for use as multifunctional SERS substrates. The obtained SERS sensor manifested a high sensitivity to rhodamine 6G (R6G) at a low concentration of 1 × 10-13 M and a detection limit as low as 5 × 10-9 M for the organic herbicide 4-chlorophenol (4-CP). Moreover, because of the good, stable photocatalytic properties of this exotic 3D hierarchical structure, the ZnO-Ag hybrids could self-clean under UV irradiation; this allowed repeatable SERS detection of many organic pollutants over more than three cycles with tolerable intensity attenuation. Finally, the unique repeatable detection of the organic dye R6G and the persistent organic pollutant (POP) 2,4-dichlorophenoxyacetic acid (2,4-D) demonstrates a new route to eliminate the single-use problem of traditional SERS substrates and suggests promising applications of such materials as real-time online sensors for organic pollutant detection. [ABSTRACT FROM AUTHOR]

In-situ monitoring of silver nanoparticle formation was studied in thin films of polyvinyl alcohol and silver nitrate. We proposed the observation of surface-enhanced Raman spectroscopy (SERS) as a novel and simple technique to record the growth of silver nanoparticles in polyvinyl alcohol thin films. Observed enhancement in the Raman bands of polyvinyl alcohol is explained through the localized surface plasmon resonance of silver nanoparticles. Influence of temperature generated by silver nanoparticles on the formation of nanoparticles is also discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au nanoparticles modified with antibody, carrying rifampicin to infected macrophages. • Antibiotic drug delivery led to the combat of BCG bacteria infecting macrophages. • The uptake of gold nanocarrier in macrophage was monitored by SERS spectroscopy. • Anti-folic acid was anchored on gold surface bonding to previous adsorbed folic acid. • Antibody modifying gold surface interacted with macrophages by non-specific portions. Gold nanoparticles (AuNP) modified with antibody and rifampicin (RP) were tested against Mycobacterium bovis Bacillus Calmette-Guérin (BCG), which previously generated in vitro infection of macrophages from mice. Such a drug delivery system works as nanocarrier for RP and presented lower toxicity for macrophages cells than each separated component. Surface-enhanced Raman scattering (SERS) spectroscopy and fluorescence microscopy were used as analytical tools for the characterization of the internalization of gold nanocarriers into macrophage cells. The effective antibiotic action of RP, when combined with gold nanocarrier, was confirmed by dead-live assay of BCG bacteria lysed from macrophages after incubation. Such results indicate the delivery of RP to BCG bacteria, which were infecting macrophages, occurred with remarkable efficiency. It was rationalized based on the strategy used for the adsorption of antibody molecules on gold surface. [ABSTRACT FROM AUTHOR]

For many disease states, positive outcomes are directly linked to early diagnosis, where therapeutic intervention would be most effective. Recently, trends in disease diagnosis have focused on the development of label-free sensing techniques that are sensitive to low analyte concentrations found in the physiological environment. Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy that allows for label-free, highly sensitive, and selective detection of analytes through the amplification of localized electric fields on the surface of a plasmonic material when excited with monochromatic light. This results in enhancement of the Raman scattering signal, which allows for the detection of low concentration analytes, giving rise to the use of SERS as a diagnostic tool for disease. Here, we present a review of recent developments in the field of in vivo and in vitro SERS biosensing for a range of disease states including neurological disease, diabetes, cardiovascular disease, cancer, and viral disease. [ABSTRACT FROM AUTHOR]

We present a novel fragmented-film surface-enhanced Raman scattering (SERS) substrate produced by nanosphere lithography and direct peel-off for SERS efficacy enhancement. The 2D hexagonally close-packed polystyrene nanospheres on the polydimethylsilozane (PDMS) substrate are covered with silver film and then directly peeled off using sticky tape. During the peel-off process, the pulling force induces the stretch and contraction of the PDMS substrate and causes fracture of the 2D triangular silver film. Under laser excitation, a stronger localized electric field is induced in the smaller cracks and enhances the SERS intensity. The origin of this SERS enhancement is confirmed by numerical simulation using the finite element method and substrate annealing to smoothen the cracks. For the case using nanospheres with a diameter of 740 nm, an enhancement factor 6.5 × 106 can be achieved. The proposed fragmented-film SERS substrate gains 1.8 and 2.6 times larger Raman intensity at the 1358 cm−1 SERS peak than those using pyramidal silver islands and silver nanoshell array. The proposed SERS substrate has the features of easy fabrication, low production cost, short fabrication time and high enhancement factor. [ABSTRACT FROM AUTHOR]

Nearly monodisperse Au nanorods (NRs) with different aspect ratios were separated from home-synthesized polydisperse samples using a gradient centrifugation method. The morphology, size and its distribution, and photo-absorption property were analyzed by transmission electron microscopy, atomic force microscopy and UV–visible spectroscopy. Subsequently, using colloidal Au NRs (36.2 nm ×10.7 nm) with 97.4% yield after centrifugation and Au nanospheres (NSs) (22.9 ± 1.0 nm in diameter) with 97.6% yield as Au substrates, surface-enhanced Raman scattering (SERS) spectra of 2,4-dichlorophenoxyacetic acid (2,4-D) were recorded using laser excitation at 632.8 nm. Results show that surface enhancement factors (EF) for Au NRs and NSs are 6.2 × 105 and 5.7 × 104 using 1.0 × 10−6 M 2,4-D, respectively, illustrating that EF value is a factor of ∼10 greater for Au NRs substrates than for Au NSs substrates. As a result, large EF are a mainly result of chemical enhancement mechanisms. Thus, it is expected that Au NPs can find a comprehensive SERS application in the trace detection of pesticide residues. [ABSTRACT FROM AUTHOR]