Advances in Surface-Enhanced Raman Scattering Sensors of Pollutants in Water Treatment.

Water scarcity is a world issue, and a solution to address it is the use of treated wastewater. Indeed, in these wastewaters, pollutants such as pharmaceuticals, pesticides, herbicides, and heavy ions can be present at high concentrations. Thus, several analytical techniques were initiated throughout recent years for the detection and quantification of pollutants in different types of water.

Fermi level shifts of gold nanospheres on ZnO film upon UV irradiation.

Here, Fermi level shifts of gold nanospheres on zinc oxide (ZnO) film upon UV irradiation are studied. These Fermi level shifts are obtained by recording extinction spectra of gold nanospheres characterized by their plasmon resonance and are due to the presence of additional electrons stored in gold nanospheres and coming from ZnO film upon UV irradiation. It is demonstrated that the blueshift of the plasmon resonance of the Au nanospheres upon UV irradiation points out the transfer of electrons from ZnO film to Au nanospheres.

Gold Nanocolumnar Templates for Effective Chemical Sensing by Surface-Enhanced Raman Scattering.

Herein, we investigate the chemical sensing by surface-enhanced Raman scattering regarding two templates of gold nanocolumns (vertical and tilted) manufactured by glancing angle deposition with magnetron sputtering. We selected this fabrication technique due to its advantages in terms of low-cost production and ease of implementation. These gold nanocolumnar structures allow producing a high density of strongly confined electric field spots within the nanogaps between the neighboring nanocolumns.

Latest Advances in Metasurfaces for SERS and SEIRA Sensors as Well as Photocatalysis.

Metasurfaces can enable the confinement of electromagnetic fields on huge surfaces and zones, and they can thus be applied to biochemical sensing by using surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA). Indeed, these metasurfaces have been examined for SERS and SEIRA sensing thanks to the presence of a wide density of hotspots and confined optical modes within their structures. Moreover, some metasurfaces allow an accurate enhancement of the excitation and emission processes for the SERS effect by supporting resonances at frequencies of these processes.

Assembled Au/ZnO Nano-Urchins for SERS Sensing of the Pesticide Thiram.

In this paper, we are relating a significant improvement of the SERS effect achieved with assembled Au/ZnO nano-urchins. This improvement is realized thanks to an excellent capacity of adsorption (denoted ) for thiram molecules on these plasmonic nano-urchins, which is a key point to be taken into account for obtaining a SERS spectrum. Moreover, this outlook may be employed for different types of plasmonic substrates and for a wide number of molecules.

Oxygen Vacancy Dynamics in Highly Crystalline Zinc Oxide Film Investigated by PIERS Effect.

Surface-enhanced Raman spectroscopy (SERS) is commonly employed as an analysis or detection tool of biological and chemical molecules. Recently, an alternative section of the SERS field has appeared, called photo-induced enhanced Raman spectroscopy (PIERS). This PIERS effect is based on the production of the oxygen vacancies (V0) in metal-oxide semiconductor thin-film (or other structures) by irradiation with UV light, thus enabling a Raman signal enhancement of chemical molecules through charge transfer processes between this photo-irradiated semiconductor film (or other structures) and these chemical molecules via metallic nanoparticles deposited on this photo-irradiated substrate.

SERS Amplification in Au/Si Asymmetric Dimer Array Coupled to Efficient Adsorption of Thiophenol Molecules.

Maximizing the surface-enhanced Raman scattering (SERS) is a significant effort focused on the substrate design. In this paper, we are reporting on an important enhancement in the SERS signal that has been reached with a hybrid asymmetric dimer array on gold film coupled to the efficient adsorption of thiophenol molecules on this array. Indeed, the key factor for the SERS effect is the adsorption efficiency of chemical molecules on the surface of plasmonic nanostructures, which is measured by the value of the adsorption constant usually named .

Application of Novel Plasmonic Nanomaterials on SERS.

During these past two decades, the fabrication of ultrasensitive surface-enhanced Raman scattering (SERS) substrates has explosed by using novel plasmonic materials such bimetallic materials (e [...

Recent advances in plasmonic nanocavities for single-molecule spectroscopy.

Plasmonic nanocavities are able to engineer and confine electromagnetic fields to subwavelength volumes. In the past decade, they have enabled a large set of applications, in particular for sensing, optical trapping, and the investigation of physical and chemical phenomena at a few or single-molecule levels. This extreme sensitivity is possible thanks to the highly confined local field intensity enhancement, which depends on the geometry of plasmonic nanocavities.

Highly crystalline ZnO film decorated with gold nanospheres for PIERS chemical sensing.

In this paper, we report on the study of a novel type of substrate based on a highly crystalline ZnO film photo-irradiated using UV for enhancing the Raman signal. This effect is called photo-induced enhanced Raman spectroscopy (PIERS). This PIERS substrate is composed of a photo-irradiated thin ZnO film on which gold nanoparticles are deposited and allows large photo-induced SERS enhancement to be obtained for the chemical detection of small molecules compared to normal SERS signals.

Latest Novelties on Plasmonic and Non-Plasmonic Nanomaterials for SERS Sensing.

An explosion in the production of substrates for surface enhanced Raman scattering (SERS) has occurred using novel designs of plasmonic nanostructures (e.g., nanoparticle self-assembly), new plasmonic materials such as bimetallic nanomaterials (e.

The Prevailing Role of Hotspots in Plasmon-Enhanced Sum-Frequency Generation Spectroscopy.

The plasmonic amplification of nonlinear vibrational sum frequency spectroscopy (SFG) at the surfaces of gold nanoparticles is systematically investigated by tuning the incident visible wavelength. The SFG spectra of dodecanethiol-coated gold nanoparticles chemically deposited on silicon are recorded for 20 visible wavelengths. The vibrational intensities of thiol methyl stretches extracted from the experimental measurements vary with the visible color of the SFG process and show amplification by coupling to plasmon excitation.

Hybrid Au/Si Disk-Shaped Nanoresonators on Gold Film for Amplified SERS Chemical Sensing.

We present here the amplification of the surface-enhanced Raman scattering (SERS) signal of nanodisks on a gold film for SERS sensing of small molecules (thiophenol) with an excellent sensitivity. The enhancement is achieved by adding a silicon underlayer for the composition of the nanodisks. We experimentally investigated the sensitivity of the suggested Au/Si disk-shaped nanoresonators for chemical sensing by SERS.

A hybrid metal-dielectric zero mode waveguide for enhanced single molecule detection.

We fabricated hybrid metal-dielectric nanoslots and measured their optical response at three different wavelengths. The nanostructure is fabricated on a bilayer film formed by the sequential deposition of silicon and gold on a transparent substrate. The optical characterization is done via fluorescence spectroscopy measurements.

Plasmonics and its Applications.

Plasmonics is a quickly developing subject that combines fundamental research and applications ranging from areas such as physics to engineering, chemistry, biology, medicine, food sciences, and the environmental sciences. Plasmonics appeared in the 1950s with the discovery of surface plasmon polaritons. Then, plasmonics went through a novel impulsion in mid-1970s when the surface-enhanced Raman scattering was discovered.

Sum-Frequency Generation Spectroscopy of Plasmonic Nanomaterials: A Review.

We report on the recent scientific research contribution of non-linear optics based on Sum-Frequency Generation (SFG) spectroscopy as a surface probe of the plasmonic properties of materials. In this review, we present a general introduction to the fundamentals of SFG spectroscopy, a well-established optical surface probe used in various domains of physical chemistry, when applied to plasmonic materials. The interest of using SFG spectroscopy as a complementary tool to surface-enhanced Raman spectroscopy in order to probe the surface chemistry of metallic nanoparticles is illustrated by taking advantage of the optical amplification induced by the coupling to the localized surface plasmon resonance.

Light Concentration by Metal-Dielectric Micro-Resonators for SERS Sensing.

Metal-dielectric micro/nano-composites have surface plasmon resonances in visible and near-infrared domains. Excitation of coupled metal-dielectric resonances is also important. These different resonances can allow enhancement of the electromagnetic field at a subwavelength scale.

Al/Si Nanopillars as Very Sensitive SERS Substrates.

In this paper, we present a fast fabrication of Al/Si nanopillars for an ultrasensitive SERS detection of chemical molecules. The fabrication process is only composed of two steps: use of a native oxide layer as a physical etch mask followed by evaporation of an aluminum layer. A random arrangement of well-defined Al/Si nanopillars is obtained on a large-area wafer of Si.

Hybrid Metal-Dielectric Nano-Aperture Antenna for Surface Enhanced Fluorescence.

A hybrid metal-dielectric nano-aperture antenna is proposed for surface-enhanced fluorescence applications. The nano-apertures that formed in the composite thin film consist of silicon and gold layers. These were numerically investigated in detail.

True thermal antenna with hyperbolic metamaterials.

A thermal antenna is an electromagnetic source that emits in its surrounding a spatially coherent field in the infrared frequency range. Usually, its emission pattern changes with the wavelength so that the heat flux it radiates is weakly directive. Here, we show that a class of hyperbolic materials of type II possess a Brewster angle, which is weakly dependent on the wavelength, so that they can radiate like a true thermal antenna with a highly directional and p-polarized heat flux.

Directional surface enhanced Raman scattering on gold nano-gratings.

Directional plasmon excitation and surface enhanced Raman scattering (SERS) emission were demonstrated for 1D and 2D gold nanostructure arrays deposited on a flat gold layer. The extinction spectrum of both arrays exhibits intense resonance bands that are redshifted when the incident angle is increased. Systematic extinction analysis of different grating periods revealed that this band can be assigned to a propagated surface plasmon of the flat gold surface that fulfills the Bragg condition of the arrays (Bragg mode).

Generalized analytical model based on harmonic coupling for hybrid plasmonic modes: comparison with numerical and experimental results.

Metal nanoparticle arrays have proved useful for different applications due to their ability to enhance electromagnetic fields within a few tens of nanometers. This field enhancement results from the excitation of various plasmonic modes at certain resonance frequencies. In this article, we have studied an array of metallic nanocylinders placed on a thin metallic film.

Soft UV nanoimprint lithography-designed highly sensitive substrates for SERS detection.

We report on the use of soft UV nanoimprint lithography (UV-NIL) for the development of reproducible, millimeter-sized, and sensitive substrates for SERS detection. The used geometry for plasmonic nanostructures is the cylinder. Gold nanocylinders (GNCs) showed to be very sensitive and specific sensing surfaces.

Integration of short gold nanoparticles chain on SOI waveguide toward compact integrated bio-sensors.

We demonstrate the integration of short metal nanoparticle chains (L ≈700 nm) supporting localized surface plasmons in Silicon On Insulator (SOI) waveguides at telecom wavelengths. Nanoparticles are deposited on the waveguide top and excited through the evanescent field of the TE waveguide modes. Finite difference time domain calculations and waveguide transmission measurements reveal that almost all the TE mode energy can be transferred to nanoparticle chains at resonance.

Iron oxide magnetic nanoparticles used as probing agents to study the nanostructure of mixed self-assembled monolayers.

Self-assembled monolayers (SAMs) of organic molecules are of exceptional technological importance since they represent a convenient, flexible, and simple system for tuning the chemical and physical properties of surfaces. The fine control of surface properties is directly dependent on the structure of mixed SAMs which is difficult to characterize at the nanoscale with usual techniques such as scanning probe microscopies. In this study, we report on a general method to investigate at the nanoscale the structure of molecular patterns which consist in SAMs of two components.