Broadband Plasmonic Enhancement Research Articles

Broadband Plasmonic Enhancement of High-Efficiency Dye-Sensitized Solar Cells by Incorporating Au@Ag@SiO2 Core-Shell Nanocuboids.

The introduction of plasmonic additives is a promising approach to boost the efficiency of the dye-sensitized solar cell (DSSC) since they may improve the light harvesting of a solar cell. Herein, we design broadband and strong plasmonic absorption Au@Ag@SiO2 nanocuboids (GSS NCs) as nanophotonic inclusions to achieve plasmon-enhanced DSSCs. These multiple-resonance absorptions arising from GSS NCs can be readily adjusted by altering their structures to complementarily match the absorption spectra of the dyes, especially in weak absorption zones. By subtly regulating the position of nanophotonic inclusions in the photoanodes, not only the plasmonic near-field enhancement but also far-field light scattering could be adequately developed to promote the light harvest and thus the efficiency of DSSCs. The resulting solar cells yield an average efficiency of 10.34%, with a champion value of 10.58%. The electromagnetic simulations are consistent with the experimental observations, further corroborating the synergistic effect of plasmonic improvement in these DSSCs.

Facile one-pot synthesis of multi-shaped silver nanoparticles with tunable ultra-broadband absorption for efficient light harvesting in dye-sensitized solar cells

We report a facile one-pot synthesis of the multi-shaped anisotropic plasmonic Ag nanostructures (Mx-AgNPs) and demonstrated for the broadband plasmonic enhancement in dye-sensitized solar cells (DSSCs). The UV–Vis spectra obtained during the synthesis of AgNPs revealed the fine-tuning of the surface plasmon resonance (SPR) peak and the occurrence of broadband multiple SPR peak with an increase in reaction time. The TEM images confirm the collective presence of different shapes/sizes of the Ag nanoparticles (including sphere, oval, polygon, triangular, rod and some irregular morphologies). The resultant ultra-broadband LSPR from the Mx-AgNPs were utilized to improve the total light absorption coefficient of N719 dye. We observed that the photoanode film incorporated with of Mx-AgNPs enhances light harvesting of the dye up to 60% over an entire visible region. The effects of Mx-AgNPs in the photoanode film on the efficiency and the spectral response of the DSSCs were further evaluated experimentally. Substantial improvement with the considerable broadening in the spectral response was observed in the ‘incident photon- to current conversion efficiency’ (IPCE) spectra for the plasmonic DSSCs. The ‘power conversion efficiency’ (PCE) for the best performing plasmonic DSSCs found to improve by ~ 30% for the plasmonic DSSCs. The observed improvement in the efficiency was mainly attributed to the significant enhancement of the light harvesting capacity of the DSSCs resulted by ultra-broadband surface plasmon resonance of the Mx-AgNPs.

Plasmonic Nanowires for Wide Wavelength Range Molecular Sensing.

In this paper, we propose the use of a standing nanowires array, constituted by plasmonic active gold wires grown on iron disks, and partially immersed in a supporting alumina matrix, for surface-enhanced Raman spectroscopy applications. The galvanic process was used to fabricate nanowires in pores of anodized alumina template, making this device cost-effective. This fabrication method allows for the selection of size, diameter, and spatial arrangement of nanowires. The proposed device, thanks to a detailed design analysis, demonstrates a broadband plasmonic enhancement effect useful for many standard excitation wavelengths in the visible and NIR. The trigonal pores arrangement gives an efficiency weakly dependent on polarization. The devices, tested with 633 and 830 nm laser lines, show a significant Raman enhancement factor, up to around 6 × 104, with respect to the flat gold surface, used as a reference for the measurements of the investigated molecules.

Nanoantenna-Enhanced Infrared Spectroscopic Chemical Imaging.

Spectroscopic infrared chemical imaging is ideally suited for label-free and spatially resolved characterization of molecular species, but often suffers from low infrared absorption cross sections. Here, we overcome this limitation by utilizing confined electromagnetic near-fields of resonantly excited plasmonic nanoantennas, which enhance the molecular absorption by orders of magnitude. In the experiments, we evaporate microstructured chemical patterns of C60 and pentacene with nanometer thickness on top of homogeneous arrays of tailored nanoantennas. Broadband mid-infrared spectra containing plasmonic and vibrational information were acquired with diffraction-limited resolution using a two-dimensional focal plane array detector. Evaluating the enhanced infrared absorption at the respective frequencies, spatially resolved chemical images were obtained. In these chemical images, the microstructured chemical patterns are only visible if nanoantennas are used. This confirms the superior performance of our approach over conventional spectroscopic infrared imaging. In addition to the improved sensitivity, our technique provides chemical selectivity, which would not be available with plasmonic imaging that is based on refractive index sensing. To extend the accessible spectral bandwidth of nanoantenna-enhanced spectroscopic imaging, we employed nanostructures with dual-band resonances, providing broadband plasmonic enhancement and sensitivity. Our results demonstrate the potential of nanoantenna-enhanced spectroscopic infrared chemical imaging for spatially resolved characterization of organic layers with thicknesses of several nanometers. This is of potential interest for medical applications which are currently hampered by state-of-art infrared techniques, e.g., for distinguishing cancerous from healthy tissues.

Plasmonic Catalytic Layer for Visible-Light Enhanced Methanol Oxidation Reaction

Methanol oxidation reaction (MOR) has been an important topic in electrochemical fuel cells [1]. However, the slow kinetics of MOR brings the bottleneck that directly limits the efficiency of direct methanol fuel cells (DMFCs). Traditionally, platinum (Pt) based alloys, e.g. PtRu, PtAu, PtCu, and etc., are used as the catalysts for MOR [2]. Aiming at enhancing the MOR, titanium dioxide and other semiconductors have also been introduced to the anodic design of DMFCs [3]. Many nano-composite have been proposed as the catalysts for MOR, including Pt-TiO2 [4], Pt-ZnO [5], Pt-WO3 [6] and etc.. In another field of physical chemistry, plasmonic catalysis has been a rising field in photochemistry for more than one decade [7]. Noble metals, e.g., gold (Au), silver (Ag), Pt are common candidates for plasmonic catalysis. Besides, nano-composites , e.g., Ag-SiO2, Au-TiO2, Au-SiO2, and etc., have also attracted enormous attentions. By utilizing metallic nanostructures and/or metal-semiconductor nano-composites, visible light can be harvested and transformed into chemical energy to trigger or enhance chemical reactions, e.g. water splitting [8], hydrogen dissociation [9], steam reforming of ethanol [10], degradation of ammonium [11]. In this paper, self-supported metallic nano-dendrites are proposed as plasmonc catalytic layer for visible-light enhanced methanol oxidation reaction. Besides, an extra facile fluoride assisted galvanic replacement was proposed to prepare self-supported Ag and Ag nano-dendrites on Si base. These structures can be achieved by simply immersing Si wafers into the mixture of AgNO3 (or HAuCl4) and buffered oxide etchant (BOE) under ambient conditions within 5 minutes [12, 13]. The prepared Au (or Ag) nano-dendrites were used to boost methanol oxidation reaction under visible-light illumination (AM 1.5G). Obvious photo-enhancement on the oxidation current (28%) was achieved on Au nano-dendrites. A comparative study was conducted by measuring the photo-enhancement under various illumination wavelengths. The best photo-response was found at 700 nm. Moreover, the self-supported Au nano-dendrites with various pore sizes and branch sizes not only provide high aspect surface area but also enable a broadband plasmonic enhancement. In summary, we proposed a cost-effective and facile approach to prepare Ag and Au dendrites on Si base under ambient conditions. Both Ag and Au nano-dendrites show promising potential in plasmon enhanced methanol oxidation reaction. We expect these structures may soon find application in photo-electrochemical cells.

Au/Ag core–shell nanocuboids for high-efficiency organic solar cells with broadband plasmonic enhancement

We introduced Au@Ag core–shell nanocuboids with broadband plasmonic enhancement in organic photovoltaics, which show multimode localized surface plasmon resonance that can be tuned to match the light absorption spectra of the devices by changing the geometric size.

Photonic-Plasmonic Scattering Resonances in Deterministic Aperiodic Structures

In this paper, we combine experimental dark-field scattering spectroscopy and accurate electrodynamics calculations to investigate the scattering properties of two-dimensional plasmonic lattices based on the concept of aperiodic order. In particular, by discussing visible light scattering from periodic, Fibonacci, Thue-Morse and Rudin-Shapiro lattices fabricated by electron-beam lithography on transparent quartz substrates, we demonstrate that deterministic aperiodic Au nanoparticle arrays give rise to broad plasmonic resonances spanning the entire visible spectrum. In addition, we show that far-field diffractive coupling is responsible for the formation of characteristic photonic-plasmonic scattering modes in aperiodic arrays of metal nanoparticles. Accurate scattering simulations based on the generalized Mie theory approach support our experimental results. The possibility of engineering complex metal nanoparticle arrays with distinctive plasmonic resonances extending across the entire visible spectrum can have a significant impact on the design and fabrication of novel nanodevices based on broadband plasmonic enhancement.