ABSTRACT
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. Among them, the surface-enhanced Raman scattering (SERS) technique was examined due to its high sensitivity and its ability to provide details on the molecular structure. Herein, we summarize the most recent advances (2021-2023) on SERS sensors of pollutants in water treatment. In this context, we present the results obtained with the SERS sensors in terms of detection limits serving as assessment of SERS performances of these sensors for the detection of various pollutants.
ABSTRACT
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. Moreover, it is reported that the Fermi level shifts vary with UV irradiation time by approaching the conduction band of ZnO, and are estimated by an analogous model to the electronic structure of a semiconductor, which can be expressed as a function of the plasmon resonance blueshift of the Au nanospheres. Henceforward, these stored electrons and these Fermi level shifts can allow the improvement of the properties of photocatalytic reduction for the gold-semiconductor structures and can also be used for photo-induced enhanced Raman spectroscopy.
ABSTRACT
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. Thiophenol molecules were used as model analytes since they have the principal property to adsorb well on gold surfaces. Regarding chemical sensing, the vertical (tilted) nanocolumnar templates showed a detection threshold limit of 10 nM (20 nM), an enhancement factor of 9.8 × 108 (4.8 × 108), and a high quality of adsorption with an adsorption constant Kads of 2.0 × 106 M-1 (1.8 × 106 M-1) for thiophenol molecules.
ABSTRACT
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. Finally, the metasurfaces allow the enhancement of the absorption capacity of the solar light and the generation of a great number of catalytic active sites in order to more quickly produce the surface reactions. Here, we outline the latest advances in metasurfaces for SERS and SEIRA sensors as well as photocatalysis.
Subject(s)
Spectrum Analysis, Raman , VibrationABSTRACT
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 K) 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. We studied the capacity of the assembled Au/ZnO nano-urchins to be sensitive to the pesticide thiram, which adsorbs well on metals via the metal-sulfur bond. For the thiram detection, we found a limit concentration of 10 pM, a value of this capacity of adsorption (K) of 9.5 × 106 M-1 and a factor of analytical enhancement equal to 1.9 × 108.
ABSTRACT
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. The PIERS technique can enable studying the dynamics of the oxygen vacancies under ambient and operando conditions compared to conventional tools of analysis. In this paper, we present the results obtained on the formation and healing rates of surface oxygen vacancies (V0) in a highly crystalline ZnO film investigated by the PIERS effect, and we compare these results to the literature in order to study the effect of the crystallinity on these formation and healing rates of V0 in a ZnO film.
ABSTRACT
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 K. In addition, this approach can be applied to several SERS substrates allowing a prescriptive estimate of their relative performance as sensor and to probe the affinity of substrates for a target analyte. Moreover, this prescriptive estimate leads to higher predictability of SERS activity of molecules, which is also a key point for the development of sensors for a broad spectrum of analytes. We experimentally investigated the sensitivity of the Au/Si asymmetric dimer array on the gold film for SERS sensing of thiophenol molecules, which are well-known for their excellent adsorption on noble metals and serving as a proof-of-concept in our study. For this sensing, a detection limit of 10 pM was achieved as well as an adsorption constant K of 6 × 106 M-1. The enhancement factor of 5.2 × 1010 was found at the detection limit of 10 pM for thiophenol molecules.
ABSTRACT
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. Indeed, suitably designed structures providing engineered local optical fields lead to enhanced optical sensing based on different phenomena such as surface enhanced Raman scattering, fluorescence, and Förster resonance energy transfer. In this mini-review, we illustrate the most recent results on plasmonic nanocavities, with specific emphasis on the detection of single molecules.
ABSTRACT
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 [...].
ABSTRACT
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. This photo-induced SERS enhancement is due to increasing electron density of the gold nanoparticles and charge transfer mechanisms. Here, we achieve a high quality PIERS substrate, the signal of which exhibits weaker fluctuations and a similar or greater gain (up to 7.52) than those reported in the current literature. Henceforth, these PIERS substrates can be of great potential for industrial applications.
ABSTRACT
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.g., Au/Ag) and hybrid nanomaterials (e.g., metal/semiconductor), and new non-plasmonic nanomaterials. The novel plasmonic nanomaterials can enable a better charge transfer or a better confinement of the electric field inducing a SERS enhancement by adjusting, for instance, the size, shape, spatial organization, nanoparticle self-assembly, and nature of nanomaterials. The new non-plasmonic nanomaterials can favor a better charge transfer caused by atom defects, thus inducing a SERS enhancement. In last two years (2019-2020), great insights in the fields of design of plasmonic nanosystems based on the nanoparticle self-assembly and new plasmonic and non-plasmonic nanomaterials were realized. This mini-review is focused on the nanoparticle self-assembly, bimetallic nanoparticles, nanomaterials based on metal-zinc oxide, and other nanomaterials based on metal oxides and metal oxide-metal for SERS sensing.
ABSTRACT
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. We achieved values of enhancement factors of 5 × 10 7 - 6 × 10 7 for thiophenol sensing. Moreover, we remarked that the enhancement factor (EF) values reached experimentally behave qualitatively as those evaluated with the E 4 model.
ABSTRACT
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. Because the enhancement is maximal in the orange-red region rather than in the green, as expected from the dipolar model for surface plasmon resonances, it is attributed mostly to hotspots created in particle multimers, in spite of their low surface densities. A simple model accounting for the longitudinal surface plasmons of multimers allows the recovery of the experimental spectral dispersion.
ABSTRACT
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. We characterized the fluorescence enhancement, as well as the lifetime and the detection volume reduction for each wavelength. We observe that the hybrid metal-dielectric nanoslots behave as enhanced zero mode waveguides in the near-infrared spectral region. Their detection volume is such that they can perform enhanced single-molecule detection at tens of µM. We compared their behavior with that of a golden ZMW, and we demonstrated that the dielectric silicon layer improves both the optical performance and the stability of the device.
ABSTRACT
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. Nevertheless, it is in this last decade that a very significant explosion of plasmonics and its applications has occurred. Thus, this special issue reports a snapshot of current advances in these various areas of plasmonics and its applications presented in the format of several articles and reviews written by worldwide researchers of this topic.
ABSTRACT
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. A short review of the first developments of SFG applications in nanomaterials is presented to span the previous emergent literature on the subject. Afterwards, the emphasis is put on the recent developments and applications of the technique over the five last years in order to illustrate that SFG spectroscopy coupled to plasmonic nanomaterials is now mature enough to be considered a promising research field of non-linear plasmonics.
ABSTRACT
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. The hybrid nano-aperture shows a more uniform field distribution within the apertures and a higher antenna quantum yield than pure gold nano-apertures. The spectral features of the hybrid nano-apertures are independent of the aperture size. This shows a high enhancement effect in the near-infrared region. The nano-apertures with a dielectric gap were then demonstrated theoretically for larger enhancement effects. The hybrid nano-aperture is fully adaptable to large-scale availability and reproducible fabrication. The hybrid antenna will improve the effectiveness of surface-enhanced fluorescence for applications, including sensitive biosensing and fluorescence analysis.
ABSTRACT
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. A good uniformity of SERS signal is achieved on the whole wafer. Finally, we investigated experimentally the sensitivity of these Al/Si nanopillars for SERS sensing, and analytical enhancement factors in the range of 1.5 × 10 7 - 2.5 × 10 7 were found for the detection of thiophenol molecules. Additionally, 3D FDTD simulations were used to better understand optical properties of Al/Si nanopillars as well as the Raman enhancement.
ABSTRACT
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. Hybrid plasmonic structures act as optical antennae by concentrating large electromagnetic energy in micro- and nano-scales. Plasmonic structures are proposed for various applications such as optical filters, investigation of quantum electrodynamics effects, solar energy concentration, magnetic recording, nanolasing, medical imaging and biodetection, surface-enhanced Raman scattering (SERS), and optical super-resolution microscopy. We present the review of recent achievements in experimental and theoretical studies of metal-dielectric micro and nano antennae that are important for fundamental and applied research. The main impact is application of metal-dielectric optical antennae for the efficient SERS sensing.
ABSTRACT
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. The realization of these sources could open a new avenue in the field of thermal management in far-field regime.
