Plasmon-enhanced Photoluminescence Research Articles

Scalable and continuous nanomaterial integration with transgenic fibers for enhanced photoluminescence

Plasmon-enhanced photoluminescence of fluorescent (mKate2) silk embedded with silver nanoparticles (AgNPs) as multifunctional photonic nanomaterials with flexibility and scalability.

Localized surface plasmon-enhanced photoluminescence of amorphous silicon quantum dots through plasmonic subwavelength crossed metallic gratings

We investigate experimentally the enhancing effect of plasmonic subwavelength crossed Ag gratings on photoluminescence (PL) from the amorphous silicon quantum dots (a-Si QDs) embedded in a central silicon-rich SiOx film of the Ag/SiOx:a-Si QDs/Ag sandwich nanostructures. The use of the crossed Ag grating structure as the top layer in the sandwich nanostructures results in a 2-fold increase in the PL peak intensity and a 1.34-fold increase in the integrated emission intensity compared with the use of a one-dimensional (1D) Ag grating top layer, and a 1.53-fold peak intensity increase compared with that of a SiOx:a-Si QDs/Ag structure without a Ag top layer. These significant PL enhancements can be attributed to the high light-extraction efficiency of the polarization-independent crossed metallic grating structure, the strong out-coupling of localized surface plasmons (LSPs), and the strong a-Si QD–LSP coupling.

Additional peak appearing in the one-photon luminescence of single gold nanorods.

We used a confocal laser microscope to investigate the one-photon photoluminescence (PL) of gold antennas. The PL spectra can be precisely fitted to a plasmon-enhanced PL model. For increasing the antenna length, the energy peak position decreases continuously until it reaches a value of 1.7-1.8 eV. For longer antennas and smaller plasmon energies, we observe an additional, persistent shoulder in the PL spectra, which we explain by a Gaussian-shaped peak at ΔX≈1.78-1.79 eV. We attribute this behavior to the opening of an additional decay path for electrons at the gold interband transition edge, which we observe only for long antennas.

Multi-Color Surface Plasmon-Enhanced Photoluminescence of Organic Dyes Using Annealed AgOx Thin Film

The multi-color surface plasmon-enhanced photoluminescence from various organic dye molecule thin films with different spectral bands is realized across the visible light regime by coating the dye on an annealed silver oxide (AgOx thin film). Using thermal annealing technique, we have transformed the AgOx thin film into a Ag nanostructure with localized surface plasmon resonance. The results provide a low-cost and efficient method to fabricate a large-area full-color organic light emission device with plasmonic enhancement.

Gold Photoluminescence Wavelength and Polarization Engineering

We demonstrate engineering of the spectral content and polarization of photoluminescence (PL) from arrayed gold nanoparticles atop a subwavelength-thin dielectric spacer and optically thick gold film, a configuration that supports gap-surface plasmon resonances (GSPRs). Choice of shapes and dimensions of gold nanoparticles influences the GSPR wavelength and polarization characteristics, thereby allowing us to enhance and spectrally mold the plasmon-assisted PL while simultaneously controlling its polarization. In order to understand the underlying physics behind the plasmon-enhanced PL, we develop a simple model that faithfully reproduces all features observed in our experiments showing also good quantitative agreement for the PL enhancement.

Plasmon-Enhanced Photoluminescence of an Amorphous Silicon Quantum Dot Light-Emitting Device by Localized Surface Plasmon Polaritons in Ag/SiOx:a-Si QDs/Ag Sandwich Nanostructures

We investigated experimentally the plasmon-enhanced photoluminescence of the amorphous silicon quantum dots (a-Si QDs) light-emitting devices (LEDs) with theAg/SiOx:a-Si QDs/Ag sandwich nanostructures, through the coupling between the a-Si QDs and localized surface plasmons polaritons (LSPPs) mode, by tuning a one-dimensional (1D) Ag grating on the top. The coupling of surface plasmons at the top and bottomAg/SiOx:a-Si QDs interfaces resulted in the localized surface plasmon polaritons (LSPPs) confined underneath the Ag lines, which exhibit the Fabry-Pérot resonance. From the Raman spectrum, it proves the existence of a-Si QDs embedded in Si-richSiOxfilm (SiOx:a-Si QDs) at a low annealing temperature (300°C) to prevent the possible diffusion of Ag atoms from Ag film. The photoluminescence (PL) spectra of a-Si QDs can be precisely tuned by a 1D Ag grating with different pitches and Ag line widths were investigated. An optimized Ag grating structure, with 500 nm pitch and 125 nm Ag line width, was found to achieve up to 4.8-fold PL enhancement at 526 nm and 2.46-fold PL integrated intensity compared to the a-Si QDs LEDs without Ag grating structure, due to the strong a-Si QDs-LSPPs coupling.

Plasmon-enhanced photoluminescence of Si-V centers in diamond from a nanoassembled metal–diamond hybrid structure

Using a facile top-down etching approach, a subwavelength-sized diamond pit structure infilled with semi-ellipsoidal gold nanoparticles was fabricated. The three-dimensional finite-difference time-domain simulations reveal strong localized surface plasmon resonance (LSPR) scattering and enhanced electric field exhibited by this hybrid nanoassembled metal–diamond-pit. Experimentally, with excitation at 633 and 830 nm close to the calculated LSPR wavelength, the photoluminescence (PL) intensities of the peak at 738 nm originating from the single photon source of silicon-vacancy centers in diamond were significantly enhanced by factors of ~100 and ~50, respectively, with respect to that from normal Si-doped diamond without the hybrid structure. By means of time-resolved PL measurements, the decay kinetic mechanisms of the plasmon-related PL enhancement were investigated and are discussed.

Photoluminescence of a single complex plasmonic nanoparticle

We report detailed investigations of the photoluminescence (PL) generated from an individual gold nanoflower, a highly branched plasmonic nanoparticle. Compared to nanostructures with simple shapes, such as spheres, nanorods, and bipyramids, nanoflowers exhibit more distinct features, i.e., the PL spectra and far-field emission patterns are strongly dependent on the wavelength and polarization of the excitation light. The experimental results are qualitatively explained using theoretical calculations. In addition, the intrinsic PL signal is highly dominated by localized surface plasmon resonances. The crucial role of plasmonic coupling in complex nanostructures during the plasmon-enhanced PL process is highlighted. The findings contribute to a deeper understanding of the PL properties of metallic nanoparticles. This study will be beneficial for several potential applications, including optical imaging and sensing in the fields of materials science and biology.

Enhanced plasmonic resonance energy transfer in mesoporous silica-encased gold nanorod for two-photon-activated photodynamic therapy.

The unique optical properties of gold nanorods (GNRs) have recently drawn considerable interest from those working in in vivo biomolecular sensing and bioimaging. Especially appealing in these applications is the plasmon-enhanced photoluminescence of GNRs induced by two-photon excitation at infrared wavelengths, owing to the significant penetration depth of infrared light in tissue. Unfortunately, many studies have also shown that often the intensity of pulsed coherent irradiation of GNRs needed results in irreversible deformation of GNRs, greatly reducing their two-photon luminescence (TPL) emission intensity. In this work we report the design, synthesis, and evaluation of mesoporous silica-encased gold nanorods (MS-GNRs) that incorporate photosensitizers (PSs) for two-photon-activated photodynamic therapy (TPA-PDT). The PSs, doped into the nano-channels of the mesoporous silica shell, can be efficiently excited via intra-particle plasmonic resonance energy transfer from the encased two-photon excited gold nanorod and further generates cytotoxic singlet oxygen for cancer eradication. In addition, due to the mechanical support provided by encapsulating mesoporous silica matrix against thermal deformation, the two-photon luminescence stability of GNRs was significantly improved; after 100 seconds of 800 nm repetitive laser pulse with the 30 times higher than average power for imaging acquisition, MS-GNR luminescence intensity exhibited ~260% better resistance to deformation than that of the uncoated gold nanorods. These results strongly suggest that MS-GNRs with embedded PSs might provide a promising photodynamic therapy for the treatment of deeply situated cancers via plasmonic resonance energy transfer.

Surface plasmon-enhanced photoluminescence of DCJTB by using silver nanoparticle arrays

It is demonstrated that photoluminescence of DCJTB can be enhanced by surface plasmons occurred in silver nanoparticle arrays on glass substrates fabricated by using nanosphere lithography (NSL) combined with reactive ion etching (RIE). By changing the size of the seed polystyrene nanosphere with fixed thickness of SiO(2) film as a buffer layer between silver nanoparticles and fluorescent dye, we systematically studied the interaction between surface plasmons in Ag nanostructures and fluorescent dye by measuring the photoluminescence and time-resolved photoluminescence (TRPL) of the samples. As compared with pure DCJTB, it is observed that PL enhancement as high as 9.4 times and life time shortening from 0.966 ns shortened to 0.63 ns can be achieved with polystyrene nanosphere 430 nm in diameter. The physical origin due to plasmonic excitation has been clarified from 3D finite element simulations, as well as the assistance of UV-visible reflectance spectrum.

Plasmon‐enhanced photoluminescence from TiO2:Sm3+:Au nanostructure

AbstractIn this paper, a novel plasmon‐enhanced photoluminescence (PL) hybrid system is presented based on metal–semiconductor nanostructure, in which TiO2:Sm3+ works as luminophor while the gold nanoparticle (NP) as the promoter of plasmon resonance. The plasmon‐enhanced PL is obtained by optimizing the plasmon resonance peak of gold NP employed in the system, and it is deduced that there is energy transfer from TiO2:Sm3+ to Au NPs during the process of light emitting. When the localized surface plasmon resonance (LSPR) spectra of Au NPs overlap with the PL spectra of TiO2:Sm3+, the Au NPs absorb the energy transferred from TiO2:Sm3+, and then the plasmonic mode confined around Au NPs can be excited to bring out the PL enhancement. magnified imageSchematic illustration of the process of plasmon‐enhanced emission. The different steps are (a) light emitting of TiO2:Sm3+, (b) energy transferred from TiO2:Sm3+ to the Au NPs, and (c) enhanced emitting of the hybrid system.

Competition between excitation and emission enhancements of quantum dots on disordered plasmonic nanostructures

Plasmon-enhanced fluorescence is attributable to two independent processes: 1) excitation enhancement due to an increased electric field near metallic nanostructures and 2) emission enhancement from a surface plasmon resonance-coupled excited state of fluorophores. Using semiconductor nanocrystals (quantum dots) on disordered plasmonic nanostructures and a mesoscopic imaging approach, we demonstrate that increased excitation can diminish the fluorescence emission enhancement efficiency. Thus, our experimental evidence on this competitive behavior has critical implications for better developing plasmon-enhanced photoluminescence.

Plasmon-assisted photoluminescence enhancement of SiC nanocrystals by proximal silver nanoparticles

Plasmon-enhanced photoluminescence has wide application potential in many areas, whereas the underlying mechanism is still in debate. We report the photoluminescence enhancement in SiC nanocrystal–Ag nanoparticle coupled system spaced by the poly(styrene sulfonic acid) sodium salt/poly(allylamine hydrochloride) polyelectrolyte bilayers. The integrated luminescence intensity can be improved by up to 17 times. Our analysis indicates that the strong coupling between the SiC nanocrystals and the surface plasmon oscillation of the silver nanoparticles is the major cause of the luminescence enhancement. These findings will help to understand the photoluminescence enhancement mechanism as well as widen the applications of the SiC nanocrystals in photonics and life sciences.

Plasmon-Enhanced Photoluminescence of SiC Quantum Dots for Cell Imaging Applications

Strong photoluminescence enhancement of chemically inert and biocompatible SiC quantum dots (QDs) ensured by their near-field coupling with multipolar localized plasmons is experimentally demonstrated. The main physical mechanisms responsible for this phenomenon are described with the use of three-dimensional FDTD simulations. Nano-Ag/SiNX/glass plasmonic substrates were shown to be efficiently used for significant luminescence enhancement of fibroblast cells labeled with the SiC QDs. The proposed approach allows a plasmon-induced enhancement of fluorescent cell imaging.

Plasmon-enhanced photoluminescence from bioconjugated gold nanoparticle and nanodiamond assembly

In this letter, we coupled nanodiamonds (NDs) with gold nanoparticles of different sizes using two complementary DNA sequences. After hybridizing the gold nanoparticles on the NDs, we observed the enhancement of the photoluminescence (PL) signals originating from the nitrogen-vacancy (N-V) center of the ND. The enhancement was attributed to the plasmon field created by the gold nanoparticles. The line shape of the enhanced PL spectra was also affected by the sizes of the attached nanoparticles due to their different resonant plasma frequencies. The signal enhancement can be used as an indexing tool for biosensing applications.

Surface plasmon-enhanced photoluminescence from a single quantum well

We have dramatically enhanced the photoluminescence intensity emitted from a single quantum well (typically by factors of 3–6) by covering the sample surface with a thin semitransparent metallic film. Using a photolithographically prepared gold grating, we show that this enhancement is due to the excitation of surface plasmons on the metal. By selectively turning off the surface plasmon excitation via sample or light polarization rotation, the enhancement can be suppressed.