Reusable Surface-enhanced Raman Scattering Substrate Research Articles

Arrays of Ag-nanoparticles decorated TiO2 nanotubes as reusable three-dimensional surface-enhanced Raman scattering substrates for molecule detection.

Three-dimensional surface-enhanced Raman scattering (SERS) substrates usually provide more hot spots in the excitation light beam and higher sensitivity when compared with the two-dimensional counterpart. Here a simple approach is presented for the fabrication of arrays of Ag-nanoparticles decorated TiO2 nanotubes. Arrays of ZnO nanorods were fabricated in advance by a hydrothermal method. Then TiO2 nanotube arrays were achieved by immersing the arrays of ZnO nanorods in an aqueous solution of (NH4)2TiF6 for 1.5 h. Vertically aligned TiO2 nanotube arrays were modified with dense Ag nanoparticles by Ag mirror reaction. High density of Ag nanoparticles decorated on the fabricated TiO2 nanotubes provide plenty of hotspots for Raman enhancement. In addition, the fabricated array of Ag nanoparticles modified TiO2 nanotubes can serve as a reusable SERS substrate because of the photocatalytic activity of the TiO2 nanotubes. The SERS substrate adsorbed with analyte molecules can realize self-cleaning in deionized water after UV irradiation for 2.5 h. The sensitivity of the fabricated SERS substrate was investigated by the detection of organic dye molecules. The detectable concentration limits of rhodamine 6G (R6G), malachite green (MG) and methylene blue (MB) were found to be 10−12 M, 10−9 M and 10−8 M, respectively. The enhancement factor (EF) of the three-dimensional SERS substrate was estimated to be as high as ∼1.4×108. Therefore, the prepared Ag nanoparticles modified TiO2 nanotube arrays have promising potentials to be applied to rapid and trace SERS detection of organic chemicals.

Bio-inspired self-cleaning carbon cloth based on flower-like Ag nanoparticles and leaf-like MOF: A high-performance and reusable substrate for SERS detection of azo dyes in soft drinks

Surface-enhanced Raman scattering (SERS) enables azo dye monitoring become rapid and efficient. However, the high cost, low efficiency and poor recyclability of SERS substrate limit its practical application. Herein, we propose a facile strategy to develop self-cleaning carbon cloth as a high-performance and reusable SERS substrate through in-situ growth of leaf-like metal-organic framework (L-MOF) and one-step electro-deposition of flower-like Ag nanoparticles (CC-L-MOF@F-Ag) followed by chemical modification for SERS detection of congo red (CR), chrysoidine (CYD) and acid orange II (AO II) in soft drinks. Taking advantages of superhydrophobicity and SERS-active F-Ag, the prepared self-cleaning CC-L-MOF@F-Ag not only avoids the diffusion-random problem and further boosts sensitivity, but also yields excellent self-cleaning property through facile washing with water, endowing its good reusability and stability. Furthermore, this substrate can realize quantitative detection of CR, CYD and AO II with low limits of detection (0.013 μM for CR, 0.017 μM for CYD and 0.0067 μM for AO II) and wide linear detection range (0.1 – 1000 μM for CR, 0.1 – 1000 μM for CYD and 0.01 – 100 μM for AO II). Meanwhile, CR, CYD and AO II in six soft drinks were also successfully detected with satisfactory recoveries. This method provides a potential and cost-effective strategy to develop advanced SERS sensing device for effective monitoring azo dyes in soft drinks.

Surface enhanced Raman scattering characteristics of three-dimensional pyramid stereo composite substrate

Surface enhanced Raman scattering (SERS) is a highly sensitive spectroscopy technique, which is widely used in chemical reaction detecting, medical diagnostics, and food analysis. The construction of the substrate structure has a very important influence on enhancing the SERS signal of the probe molecule. In this paper, a three-dimensional (3D) pyramid stereo composite SERS substrate is prepared by using polymethyl methacrylate (PMMA) to encapsulate silver nanoparticles, which achieves high sensitivity detection of Rhodamine 6G (R6G) molecules. By adjusting the dispersion density of silver nanoparticles in the PMMA acetone solution, the effective oscillation of light in the pyramid valley is realized, which not only ensures the high-density "hot spot" effect of the 3D structure, but also avoids deforming the adsorption probe molecules caused by the metal-molecule interaction. It also effectively prevents the silver nanoparticles from being oxidized and provides a larger range of electromagnetic enhancement for probe molecules, resulting in a stable output of the enhanced Raman signal. This research result provides an effective strategy for designing a high performance and reusable SERS substrate, meanwhile, it has important guiding significance for further designing an SERS substrate with improved 3D structure in the future study.

A needle-like reusable surface-enhanced Raman scattering substrate, and its application to the determination of acetamiprid by combining SERS and thin-layer chromatography

A micro surface-enhanced Raman scattering (SERS) substrate has been fabricated by electrochemical deposition of dendrite-like gold on carbon fiber needles (Au-CFNs). Scanning electron microscopy and energy dispersive spectroscopy were used to confirm the presence of the gold nanostructure on the CFNs. This substrate has a Raman scattering enhancement factor as high as 3.3 × 10^7 when using rhodamine 6G as the reporter molecule. The high SERS sensitivity is attributed to the massive hotspots on gold bulges that enhance the local surface plasmon resonance. The Au-CFN substrate was reproduced 10 times after electrochemically wiping off the analytes from the needle-like electrode. The substrate has attractive features such as convenient sampling, low sample dosage, and minimal invasion. It was applied, in combination with thin-layer chromatography, for the determination of acetamiprid on vegetables. The result was more accurate because the sample information of both the surface and the bulk can be obtained at the same time after inserting the tip of this needle substrate into the TLC plate. The limit of detection for acetamiprid is 0.05μg⋅mL-1 and the linear range is 0.1-10μg⋅mL-1. Graphical abstract A reusable micro needle-like SERS substrate was fabricated and applied for pesticide residue analysis. The SERS signal of acetamiprid can be acquired on the tip of this micro needle-like Au-CFN substrate. This substrate can be reused for 10 times.

Electrochemical fabrication of pyramid-shape silver microstructure as effective and reusable SERS substrate

The high sensitivity and reproducibility are significant for the routine Surface-enhanced Raman Scattering (SERS) detection. Here, the pyramid-shape silver microstructures has been successfully synthesized using a facile electrochemical deposition method and the reaction with a two-indium tin oxides (ITO) electrode system is carried out by potentiostatic method, where only silver nitrate (AgNO3) and poly (methyl methacrylate) (PMMA) nanospheres are introduced to control the reaction process. Meanwhile, PMMA nanospheres as morphology controlled reagents are used to lead Ag units to grow in the form of pyramid-shape. The prepared pyramid-shape silver microstructures possesses high SERS activity with an average enhancement factor (EF) of 9.1 × 105, which is superior or close to some individual Ag or Au microstructures and Ag composite materials. In addition, an excellent reproducibility is achieved resulting from a relative standard deviation of 7.9%, 8.5%, 7.3%, and 8.7% measured by four Raman shifts of R6G at 612, 772, 1363, and 1650 cm−1, respectively, which is much lower than those of the commonly used SERS substrates. Importantly, the as-prepared pyramid-shape silver microstructures have been evolved as a sensitive SERS substrate for the detection of trace amounts of rhodamine 6G (R6G) and 3-mercaptopropionic acid (3MPA) down to nanomolar and millimolar concentration with excellent recyclability. Therefore, this work offers a simple way to prepare pyramid-shape silver microstructures as an effective SERS substrate and make the SERS more practicable.

Highly Sensitive, Uniform, and Reusable Surface-Enhanced Raman Scattering Substrate with TiO₂ Interlayer between Ag Nanoparticles and Reduced Graphene Oxide.

TiO2 nanoparticles and Ag nanoparticles were successively deposited on reduced graphene oxide (rGO) by a two-step solvothermal process to develop a reusable surface-enhanced Raman scattering (SERS) substrate with high sensitivity and uniformity owing to the 2-dimensional planar structure of rGO, the photocatalytic activity of TiO2, and the SERS function of Ag nanoparticles. The presence of TiO2 interlayer efficiently diminished the interference from the Raman intensities of D-band and G-band of rGO and hence enhanced the sensitivity significantly. As compared to Ag/rGO nanocomposite, the detection limit of 4-aminothiophenol (4-ATP) for Ag/TiO2/rGO nanocomposite could be lowered from 10(-10) to 10(-14) M, and its enhancement factor could be raised from 1.27 × 10(10) to 3.46 × 10(12). Meanwhile, good uniformity remained, the relative standard deviation (RSD) value was about 10%. Furthermore, by UV irradiation in water, the photocatalytic property of TiO2 could eliminate the Raman signal of 4-ATP efficiently and made this substrate reusable. After being reused five times, its excellent SERS performance was still retained. Thus, the Ag/TiO2/rGO nanocomposite developed in this work was a promising SERS substrate with good reusability and high sensitivity and uniformity.

Zinc oxide/silver nanoarrays as reusable SERS substrates with controllable ‘hot-spots’ for highly reproducible molecular sensing

HypothesisThe reproducible surface enhanced Raman scattering (SERS)-based sensing of an analyte relies on high quality SERS substrates that offer uniformity over large areas. Uniform ZnO nanoarrays are expected to offer an appropriate platform for SERS sensing. Moreover, since ZnO has good photocatalytic properties, controllable decoration of silver nanoparticles on ZnO nanoarrays may offer an additional opportunity to clean up SERS substrates after each sensing event. ExperimentsThis study employs a facile soft chemical synthesis strategy to fabricate Raman-active and recyclable ZnO/Ag nanorod arrays as reproducible SERS substrates. Arrays of ZnO nanorods were synthesized using hydrothermal method, which was followed by controllable decoration of ZnO with silver nanoparticles (AgNPs) using an electroless plating technique. FindingsThe uniform density of SERS-active ‘hot-spots’ on ZnO nanoarrays could be controlled on a large 1×1cm2 substrate. These ZnO/Ag nanoarrays showed high reproducibility (0.132 RSD) towards acquiring SERS spectra of rhodamine B (RB) at 30 random locations on a single substrate. The photocatalytic nature of ZnO/Ag semiconductor/metal hybrid endowed these substrates with reusability characteristics. By controlling metal loading on a semiconductor surface, photocatalytic activity and high SERS performance can be integrated within a single package to obtain high quality, reproducible, stable and recyclable SERS substrates.

Surface Enhanced Raman Scattering on Self-assembled Nano Silver Film Prepared by Electrolysis Method

We demonstrate surface enhanced Raman scattering (SERS) detection of self-assembled nano silver film using a low-cost electrolysis strategy at a proper voltage and silver nitrate concentration in electrolyte. The concentration dependence of SERS from crystal violet (CV) molecules adsorbed to silver film was systematically studied. Importantly, the SERS surface enhancement factor of such nano silver film was 603, which was measured by a portable Raman spectrometer. The minimum concentration of detectable CV molecules can be as low as 1011 mol/L. The nano silver film prepared by this electrolysis method is an active, stable, cost-effective, and reusable SERS substrate.

Surface-enhanced Raman scattering on nanoporous Au

Colloidal solutions of metal nanoparticles are currently among the most studied substrates for sensors based on surface-enhanced Raman scattering (SERS). However, such substrates often suffer from not being cost-effective, reusable, or stable. Here, we develop nanoporous Au as a highly active, tunable, stable, biocompatible, and reusable SERS substrate. Nanoporous Au is prepared by a facile process of free corrosion of AgAu alloys followed by annealing. Results show that nanofoams with average pore widths of ∼250nm exhibit the largest SERS signal for 632.8nm excitation. This is attributed to the electromagnetic SERS enhancement mechanism with additional field localization within pores.