Plasmonic nanoparticles (NPs) like silver (Ag) strongly absorb the incident light and produce enhanced localized electric field at the localized surface plasmon resonance (LSPR) frequency. Enormous theoretical and experimental research has focused on the plasmonic properties of the metallic nanoparticles with sizes greater than 10 nm. However, such studies on smaller sized NPs in the size range of 3 to 10 nm (quantum-sized regime) are sparse. In this size regime, the conduction band of the metal particles discretizes, thus altering plasmon properties of the NPs from classical to the quantum regime. In this study, plasmonic properties of the spherical Ag NPs in size range of 3 to 20 nm were investigated using both quantum and classical modeling to understand the importance of invoking quantum regime to accurately describing their properties in this size regime. Theoretical calculations using standard Mie theory were carried out to monitor the LSPR peak shift and electric field enhancement as a function of the size of the bare plasmonic nanoparticle and the refractive index (RI) of the surrounding medium. Comparisons were made with and without invoking quantum regime. Also, the optical properties of metallic NPs conjugated with a chemical ligand using multi-layered Mie theory were studied, and interesting trends were observed.
相似文献Metal nanoparticles (NPs) possessing localized surface plasmon resonance (LSPR) are of high interest for applications in optics, electronics, catalysis, and sensing. The practically important issue is the stability of the LSPR, which often limits the use of some metals due to their chemical reactivity leading to degradation of the NP functionality. In this work, copper NPs of two distinct sizes are produced by magnetron sputtering gas aggregation. This method ensures formation of the particles with high purity and monocrystallinity, enhancing the chemical inertness and providing a superior time stability of the plasmonic properties. Additionally, a simple UV-ozone treatment, which leads to the formation of an oxide shell around the copper NPs, is found to be an efficient method to prevent following gradual oxidation and assure the LSPR stability in ambient atmospheric conditions for periods over 100 days even for small (10–12 nm in diameter) NPs. The obtained results allow for significant improvement of the competitiveness of copper NPs with gold or silver nanostructures, which are traditionally used in plasmonics.
相似文献The localized surface plasmon resonance (LSPR) spectroscopy of Ag nanoparticles (NPs) is sensitive to the changes of the surrounding medium, which enables the NPs to serve as plasmonic nanosensors. In this paper, the refractive index (RI) sensitivity and figure of merit (FOM) of individual NPs and nanoarrays are investigated by employing the finite difference time domain (FDTD) method. The influence of shape and size are analyzed for individual NPs, and the influence of particle spacing is analyzed for nanoarrays. It is found that the NP with shorter size in incident direction or longer size in polarization direction exhibits better sensing performance. And when the aeff is between 20 and 60 nm, the larger NP exhibits higher sensitivity but lower FOM. The results of nanoarrays show that when particle spacing is large, the sensitivity of nanoarrays is large, and the sensitivity of nanoarrays decreases first and then increases as particle spacing decreases. In addition, the FOM of nanoarrays exhibits the similar trend.
相似文献In this paper, the light absorption in the active layer of polymer solar cells (OPV) by using plasmonic nanocrystals with a hexagonal lattice structure is investigated. To study the relationship between the performance of the OPV solar cell and its active layer, a three-dimensional model of its morphology is utilized. Therefore, the three-dimensional (3D) finite-difference time-domain method and Lumerical software were used to measure the field distribution and light absorption in the active layer in terms of wavelength. OPV solar cells with bilayer and bulk heterojunction structured cells were designed using hexagonal lattice crystals with plasmonic nanoparticles, as well as core–shell geometry to govern a design to optimize light trapping in the active layer. The parameters of shape, material, periodicity, size, and the thickness of the active layer as a function of wavelength in OPV solar cells have been investigated. A very thin active layer and an ultra-thin shell were used to achieve the highest increase in optical absorption. The strong alternating electromagnetic field around the core–shell plasmonic nanoparticles resulting from the localized surface plasmon resonance (LSPR) suggested by the Ag plasmonic nanocrystals increased the intrinsic optical absorption in the active layer poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM). Based on the photovoltaic results, the short circuit current ranged from 19.7 to 26.7 mA/cm2.
相似文献To improve quantum dot solar cell performance, it is crucial to make efficient use of the available incident sunlight to ensure that the absorption is maximized. The ability of metal nanoparticles to concentrate incident sunlight via plasmon resonance can enhance the overall absorption of photovoltaic cells due to the strong confinement that results from near-field coupling or far-field scattering plasmonic effects. Therefore, to simultaneously and synergistically utilize both plasmonic effects, the placement of different plasmonic nanostructures at the appropriate locations in the device structure is also critical. Here, we introduce two different plasmonic nanoparticles, Au and Ag, to a colloidal PbS quantum dot heterojunction at the top and bottom interface of the electrodes for further improvement of the absorption in the visible and near-infrared spectral regions. The Ag nanoparticles exhibit strong scattering whereas the Au nanoparticles exhibit an intense optical effect in the wavelength region where the absorption of light of the PbS quantum dot is strongest. It is found that these dual-plasmon layers provide significantly improved short-circuit current and power conversion efficiency without any form of trade-off in terms of the fill factor and open-circuit voltage, which may result from the indirect contact between the plasmonic nanoparticles and colloidal quantum dot films.
相似文献Noble metal nanoparticles (NPs) have attracted much attention due to their unique physical and chemical properties such as tunable surface plasmonics, high-efficiency electrochemical sensing, and enhanced fluorescence. We produced two biosensor chips consisting of Ag@Au bimetallic nanoparticles (BNPs) on a carbon thin film by simple RF-sputtering and RF-plasma-enhanced chemical vapor co-deposition. We deposited Au NPs with average size of 4 nm (Au1 NPs) or 11 nm (Au2 NPs) on a sensor chip consisting of Ag NPs with mean size of 15 nm, and we investigated the effect of shell size (Au NPs) on the chemical activities of the resulting Ag@Au1 BNPs and Ag@Au2 BNPs. We estimated the average size and morphology of Ag@Au BNPs by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. X-ray diffraction (XRD) patterns revealed that Ag NPs and Au NPs had face-centered cubic (FCC) structure. We studied aging of the biosensor chips consisting of Ag@Au BNPs by localized surface plasmon resonance (LSPR) spectroscopy for up to 3 months. UV–visible aging of the prepared samples indicated that Ag@Au1 BNPs, which corresponded to Ag NPs covered with smaller Au NPs, were more chemically active than Ag@Au2 BNPs. Furthermore, we evaluated changes in the LSPR absorption peaks of Ag@Au1 BNPs and bare Ag NPs in the presence of a DNA primer decamer at fM concentrations, to find that Ag@Au1 BNPs were more sensitive biosensor chips within a short response time as compared to bare Ag NPs.
相似文献In this work, a label-free and inexpensive method for the monitoring of water pollutants is demonstrated. We introduce a localized surface plasmon resonance (LSPR) based plasmonic capillary optical biosensor to detect microalgae cells. Here, the plasmonic capillary biosensor was prepared by decorating the inner walls of a glass capillary with gold nanoparticles that were employed for investigations. Since the gold nanoparticle has the potential to sense pollutants in water rapidly with high sensitivity and they are expected to perform a significant role in environmental monitoring. Our proposed plasmonic capillary sensor has a detection limit of 25 algal cells (Chlorella sp. CB4). Furthermore, the plasmonic capillary sensing platform significantly simplifies sensor fabrication and reduces the cost of the device. We believe that the presented plasmonic sensor could stand as a potential candidate for developing a cost-effective, label-free, and rapid sensing platform to detect microalgae pollutants present in the water at very low concentrations.
相似文献This paper focuses on the effective dielectric constant of water-based plasmonic nanofluid containing SiO2/Ag core/shell nanoparticles (NPs). Two effective models, based on S-parameter retrieval method and Maxwell-Garnett effective medium theory, are employed. The effective dielectric constants predicted by the two effective models are compared and the applicability is evaluated by comparing the reflectance and absorptance. Three influence factors, including volume fraction, core-shell ratio, and size of NPs, are considered. Results show both of the two effective models can predict reliable effective dielectric constants when the volume fraction, size, and core-shell ratio of nanoparticles are 5%, 25 nm, and 4:1 respectively. Only small deviations appear in the resonant region under this condition. With the increase of volume fraction, shell proportion, or size, deviations in the resonant region become larger for both of the two effective models. Therefore, the predicted effective dielectric constants are not suitable for the prediction of optical properties, because the resonant region is the key region of the solar conversion for plasmonic nanofluids. Hence, the parameters of NPs need to be changed to make the effective models applicable. Moreover, the effective model based on S-parameter retrieval can predict more reliable dielectric constant than the effective model based on Maxwell-Garnett theory.
相似文献We present an extensive study of the optical properties of Myrcia sylvatica essential oil with the goal of investigating the suitability of its material system for uses in organic photovoltaics. The methods of extraction, experimental analysis, and theoretical modeling are described in detail. The precise composition of the oil in our samples is determined via gas chromatography, mass spectrometry, and X-ray scattering techniques. The measurements indicate that, indeed, the material system of Myrcia sylvatica essential oil may be successfully employed for the design of organic photovoltaic devices. The optical absorption of the molecules that compose the oil are calculated using time-dependent density functional theory and used to explain the measured UV-Vis spectra of the oil. We show that it is sufficient to consider the α-bisabolol/cadalene pair, two of the main constituents of the oil, to obtain the main features of the UV-Vis spectra. This finding is of importance for future works that aim to use Myrcia sylvatica essential oil as a photovoltaic material.
相似文献The angle-variable tunable optical filter was strictly fabricated by two strategies of nanoimprint-coupled metal nanopatterning with improved cost-effectiveness and accessibility. The tunable optical properties and the performances of two strategies were experimentally examined and turned out to be well matched to numerical results. Tunable properties are obtained by three factors: size of fabricated Ag nanodisks, incident illumination angle, and fabrication strategies. The resonant extinction peak shifts were identified to show a large increase along with the increase in fabricated Ag disk size and increase in the incidence angle of illumination. When comparing a fabrication strategy, it was confirmed that the sample fabricated by the strip-off method has better stability on color changes with a consistent dependency on the incident angle. The presented strategies of fabrication are technically viable for obtaining well-defined plasmonic nanostructures so that it has the feasibility to apply for fascinating optical applications including display or tunable optical filters.
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