Presence Of Plasmonic Nanostructure Research Articles

Plasmon-enhanced chiral absorption through electric dipole–electric quadrupole interaction

Enantioselective interactions of chiral molecules include distinct absorptions to opposite-handed circularly polarized light, known as chiral absorption. Traditionally, chiral absorption has been primarily attributed to electric dipole (ED) and magnetic dipole (MD) interaction with molecular chirality. However, this approach falls short for large molecules that support high-order multipolar components, such as electric quadrupole (EQ) moment. Here, we introduce a theoretical model to study the chiral absorption of large molecules in the presence of plasmonic nanostructures. This model considers both ED–MD interaction and ED–EQ interaction enhanced by a resonant structure. We numerically study such interactions of the chiral molecular solution in the vicinity of an achiral plasmonic nano-resonator. Our results show the distinct spectral information of the chiral medium on- and off-resonance of the resonator.

Designing novel plasmonic architectures for highly efficient CIGS solar cells

CIGS solar cells is one of the best thin film solar cells which have efficiency up to 22.6 %. In the recent decades, a lot of attention has been drawn to the methods of increasing solar cells efficiencies. One of the emerging technology for enhancing thin film solar cell efficiencies are using plasmonic effects in the visible or infrared part of the electromagnetic spectrum. Therefore, the primary goal of this study is to use plasmonic nanostructures in the active layer to enhance the absorption and consequently the efficiency of a thin film CIGS solar cell with a 1000 nm thickness. Different factors such as type of material, size and surface occupied with nanostructure can be effect on CIGS solar cell performance. In this research, the solar cell has been optically and electrically characterized in the presence of plasmonic nanostructure by simulations. The efficiency was determined by characteristics parameters such as absorption, quantum efficiency, electron-hole generation rate, current–voltage curve and power-voltage curve. Based on our simulations, the maximum efficiency of 25.61 % was achieved using gold nanocubic structures with dimensions of 100 nm, Occupied Factor of 0.16, positioned at the top of the active layer. This increase is due to increase in optical path of length of scattered light and consequently its absorption in the active layer. Moreover, enhancing carrier generation, decreasing recombination and improving carrier separation can be occurred due to localized surface plasmon resonance and the near-field distribution effect, which effectively scatter light into the active layer.

Applications of surface-enhanced Raman spectroscopy based on portable Raman spectrometers: A review of recent developments.

Recently, the surface-enhanced Raman spectroscopy (SERS) technique emerges as a potential promising analytical tool for rapid, sensitive, and selective detection which can provide unique information about the substances in the presence of plasmonic nanostructures via finger-printing SERS spectra. The progress in nanostructure SERS substrates and portable Raman spectrometers will promote this novel detection technique to play an important role in the future rapid on-site assay. In this review, we summarized the latest research on SERS detection technique combined based on nanostructure SERS-active substrates with portable Raman spectrometers and their potential on-site detection applications in environment pollutants, agricultural pollutants, biomedical analysis, and other newly emerging fields (focusing particularly on the last 5years of research). The future perspective of SERS for on-site analysis is also discussed.

Nanotechnology in food and water security: on-site detection of agricultural pollutants through surface-enhanced Raman spectroscopy.

Agricultural pollutants are harmful components threatening human health, wildlife, the environment, and the ecosystem. To avoid their exposure, developing prevention and detection systems with high sensitivity and selectivity is required. Most conventional methods, including molecular and chromatographic techniques, cannot be adopted for outdoor on-site detection even though they can provide sensitive and selective detection. Thus, detection platforms that can provide on-site detection via miniaturized and high throughput systems should be developed. As an alternative method, surface-enhanced Raman scattering (SERS) provides unique information about the substances in the presence of plasmonic nanostructures, and it can be portable with the use of portable detection systems and spectrometers. In this study, on-site detection of agricultural pollutants through SERS is reviewed. Three different types of agricultural pollutants were pointed out. On-site detection of biological pollutants, including bacteria and viruses, is reviewed as the first type of pollutant. As a second type, the detection of pesticides, antibiotics, and additives are focused on as chemical pollutants. The third group includes the detection of microplastics and also nanoparticles from the environment.

Enhanced solar absorption of gold plasmon assisted TiO2-based water splitting composite

We report on the effect of thermal annealing on the microstructure, optical properties and wettability of TiO2-based water-splitting (WS) composite using full solar spectrum as source of energy. The WS material used in this study is composed of three layers (SiO2, Al2O3 and TiO2) on top of which a distribution of Localized Surface Plasmon Resonance structures such as gold are formed to obtain a multilayer composite material. The fabricated samples are then annealed at 450−1100°C temperatures range under atmospheric conditions. The crystal structure and chemical composition are determined using X-ray Diffractometer, Scanning Electron Microscope, Energy Dispersive Spectroscopy, High Resolution Scanning and Transmission Electron Microscope. UV–Vis spectroscopy is used to study the influence of thermal annealing on optical absorption. Besides, wettability alteration is assessed using both in-situ (Environmental Scanning Electron Microscope) and ex-situ (sessile drop technique). Our findings reveal that thermal annealing leads to the transformation of amorphous TiO2 to its more stable phase anatase. This transformation enhances significantly the optical properties and increases the hydrophilicity of the material surface making it suitable for WS activity. More importantly, the presence of plasmonic nanostructures allow the material to extend its photoactivity from UV region to full solar spectrum. The gold nanocrystals were also found to prefer the <111> orientation during their evolving and growth after thermal annealing. This specific compact orientation is also reported to increase the efficiency of WS.

Plasmonic nanostructure induced simultaneous slow and fast light propagation in a slab doped by four-level quantum dots

The transmission and reflection properties of a pulse through a slab doped with quantum dots near a plasmonic nanostructure are investigated theoretically. It is found that by adjusting the distance between plasmonic nanostructure and dual quantum dots which is varied from 8.8 nanometer (nm) to 14.4 nanometer (nm) the transmission and reflection spectra for incident pulse through the slab can be modified. Furthermore, it is found that in the presence of plasmonic nanostructure, the reflected and transmitted pulses are completely phase dependent. Therefore, the group velocity of the reflected and transmitted pulses can be switched from slow to fast light by changing the phase difference of two laser fields.

Goos-Hänchen shifts in a four-level quantum system near plasmonic nanostructure

Goos-Hänchen (GH) shifts of the reflected and transmitted probe beams through a cavity with a four-level quantum system and plasmonic nanostructure is investigated. It is realized that for different values of distance between plasmonic nanostructure and quantum system, the negative and positive GH shifts of the reflected and transmitted probe beams can be controlled. In addition, it is found that the relative phase of applied fields in the presence of plasmonic nanostructure can be used as an important parameter for controlling the GH shifts in reflected and transmitted light through the cavity. Moreover, the distance effect between four-level quantum system and plasmonic nanostructure has also been discussed on lateral shifts of reflected and transmitted light.

Optical bistability and multistability in a four-level quantum system in the presence of plasmonic nanostructure

In this paper, the effect of plasmonic nanostructure on behavior of optical bistability and multistability in a four-level quantum system embedded in a unidirectional ring cavity has been studied. It is found that the distance between plasmonic nanostructures and a four-level quantum system is varied from 4.4nm to 14.4nm and has an essential role for controlling the threshold of optical bistability and multistability. Moreover, obtained results show that the group velocity of pulse propagation through the medium is strongly depended on the distance between the plasmonic nanostructure and the four-level quantum system.

New tools for rapid clinical and bioagent diagnostics: microwaves and plasmonic nanostructures

In this timely review, we summarize recent work on ultra-fast and sensitive bioassays based on microwave heating, and provide our current interpretation of the role of the combined use of microwave energy and plasmonic nanostructures for applications in rapid clinical and bioagent diagnostics. The incorporation of microwave heating into plasmonic nanostructure-based bioassays brings new advancements to diagnostic tests. A temperature gradient, created by the selective heating of water in the presence of plasmonic nanostructures, results in an increased mass transfer of target biomolecules towards the biorecognition partners placed on the plasmonic nanostructures, enabling diagnostic tests to be completed in less than a minute, and in some cases only a few seconds, by further microwave heating. The diagnostic tests can also be run in complex biological samples, such as human serum and whole blood.