Plasmon-enhanced Upconversion Research Articles

Plasmon-Enhanced Upconversion Fluorescence and Its Application

Plasmon-Enhanced Upconversion Fluorescence and Its Application

Integrated plasmonic and upconversion starlike Y2O3:Er/Au@TiO2 composite for enhanced photon harvesting in dye-sensitized solar cells

A plasmon-enhanced upconversion composite Y2O3:Er/Au@TiO2 (SYE/A@T) with a three-dimensional starlike morphology is prepared and then mixed with submicron TiO2 (200 nm) to form a multifunctional scattering layer in TiO2-based dye-sensitized solar cells (DSSCs). In such starlike micronsized upconverter, Au nanoparticle-assisted plasmon effect can intensify the upconversion emission of Y2O3:Er, and simultaneously TiO2 coating can improve the charge transport within SYE/A@T. Therefore, the SYE/A@T shows extended light-absorbing range to near-infrared region and improved light-scattering ability, leading to an improved photovoltaic performance of DSSCs. With the optimum mixing ratio, a conversion efficiency of 8.62% is attained, which is a significant improvement of 27.6% compared with the cell without adding SYE/A@T. Our work provides a feasible strategy to prepare an upconversion composite with plasmon-enhanced emission and enable this composite to accommodate the DSSCs system and improve the conversion efficiency of DSSCs.

Silver nanowires as receiving-radiating nanoantennas in plasmon-enhanced up-conversion processes.

We demonstrate efficient coupling between plasmons in a single silver nanowire and nanocrystals doped with rare earth ions, α-NaYF4:Er(3+)/Yb(3+). Plasmonic interaction results in a sevenfold increase of the up-converted emission of nanocrystals located in the vicinity of the nanowires as well as much faster luminescence decays. The enhancement of the emission can be precisely controlled by the polarization of the excitation laser and is significantly stronger for polarization parallel to the nanowire antennas. Imaging of angular-resolved emission patterns in the Fourier plane reveals plasmon-mediated luminescence, where the up-converted radiation is emitted via the nanowire antennas as leakage radiation.

Plasmon-Enhanced Upconversion.

Upconversion, the conversion of photons from lower to higher energies, is a process that promises applications ranging from high-efficiency photovoltaic and photocatalytic cells to background-free bioimaging and therapeutic probes. Existing upconverting materials, however, remain too inefficient for viable implementation. In this Perspective, we describe the significant improvements in upconversion efficiency that can be achieved using plasmon resonances. As collective oscillations of free electrons, plasmon resonances can be used to enhance both the incident electromagnetic field intensity and the radiative emission rates. To date, this approach has shown upconversion enhancements up to 450×. We discuss both theoretical underpinnings and experimental demonstrations of plasmon-enhanced upconversion, examining the roles of upconverter quantum yield, plasmonic geometry, and plasmon spectral overlap. We also discuss nonoptical consequences of including metal nanostructures near upconverting emitters. The rapidly expanding field of plasmon-enhanced upconversion provides novel fundamental insight into nanoscale light-matter interactions while improving prospects for technological relevance.

Plasmon-enhanced upconversion luminescence in single nanophosphor-nanorod heterodimers formed through template-assisted self-assembly.

We demonstrate plasmonic enhancement of upconversion luminescence in individual nanocrystal heterodimers formed by template-assisted self-assembly. Lithographically defined, shape-selective templates were used to deterministically coassemble single Au nanorods in proximity to single hexagonal (β-phase) NaYF4:Yb(3+),Er(3+) upconversion nanophosphors. By tailoring the dimensions of the rods to spectrally tune their longitudinal surface plasmon resonance to match the 977 nm excitation wavelength of the phosphors and by spatially localizing the phosphors in the intense near-fields surrounding the rod tips, several-fold luminescence enhancements were achieved. The enhancement effects exhibited a strong dependence on the excitation light's polarization relative to the rod axis. In addition, greater enhancement was observed at lower excitation power densities due to the nonlinear behavior of the upconversion process. The template-based coassembly scheme utilized here for plasmonic coupling offers a versatile platform for improving our understanding of optical interactions among individual chemically prepared nanocrystal components.

Plasmon-Enhanced Nanoparticles in Photoelectrochemical Water Splitting

We report a near-infrared-driven photoelectrochemical water splitting using ZnO nanorod-array decorated with CdTe quantum dots and plasmon-enhanced upconversion nanoparticles. The plasmon enhanced the intensity of the upconversion emission, which improved the photocurrent and the gas evolution rate of the photoelectrochemical reaction greatly. We will demonstrate a process of utilizing NIR to drive the photoelectrochemical water splitting reaction. The Au-UCNs can significantly enhance the upconversion emission intensity by plasmonic effect (Fig. 1). Thus, the enhancement of photocurrent and gas evolution was achieved. The results offer a convincing demonstration that energy can be converted from NIR to chemical fuel. We believe that our strategy is fundamental to the design of solar energy devices and should become an accepted technique for solar energy utilization at the NIR and IR regions. We also etched the p-type silicon wafer to fabricate microwire array as photocathode for the artificial photosynthetic water splitting under solar irradiation. After the decoration of siliver nanoparticles, the photocurrent of silicon microwire array can be increased up to ~38 mA/cm2 under applying -1.0 V bias (Fig. 2).

Plasmon-Enhanced Upconversion Fluorescence in Er3+:Ag Phosphate Glass: the Effect of Heat Treatment

The melt quenching method is used to prepare erbium-doped silver nanoparticle (NP) embedded phosphate glass. The effect of annealing on the glass on the formation of silver NPs produced by the reduction of silver (Ag+ →Ag°) is studied. The glass samples are characterized by x-ray diffraction, UV-vis-NIR absorption, photoluminescence spectroscopy and transmission electron microscopy (TEM) imaging. The absorption spectra reveal not only the peaks due to Er3+ ions, but also the surface plasmon resonance band of silver NPs located around ∼442 nm. The TEM imaging shows the homogeneous distribution of silver NPs of almost spherical shape with an average diameter of ∼5 nm. Upconversion luminescence spectra show two major emissions at 550 and 638 nm, originating from the 4S3/2 and 4F9/2 energy levels of the Er3+ ions, respectively. The enhancement in the luminescence intensity of both the green and red bands is found to be due to the effective local field of the silver NPs as well as the energy transfer from the nanoclusters, comprised of centers with silver ions bound to silver atoms in dimers or trimers to Er3+ ions, whereas quenching occurred due to the energy transfer from erbium ions to silver NPs (Er3+ →Ag°).

Plasmon-enhanced near-infrared-active materials in photoelectrochemical water splitting

We report the near-infrared-driven photoelectrochemical water splitting using a ZnO nanorod-array decorated with CdTe quantum dots and plasmon-enhanced upconversion nanoparticles. The plasmon enhanced the intensity of the upconversion emission, which improved the photocurrent and the gas evolution rate of the photoelectrochemical reaction greatly.

Advanced Optical Materials reaches the next level

Welcome back to Advanced Optical Materials. In this last issue of 2012 we present again a broad spectrum of topics including a review article from Andrea Alù on cloaking via scattering cancellation and research articles on nanoscopy, photonic crystals, plasmonic antennas, and chiral structures to name only a few. All papers in this current issue were submitted directly to Advanced Optical Materials, which shows the high popularity of the section among our authors. This growing interest is a great sign for the future of Advanced Optical Materials Looking back to the previous issues, we observe also a high interest by our readers in the exciting work published in this dynamic research field. The most popular topics from the last issue (see Table 1) include plasmon-enhanced upconversion luminescence studied by Steven Chou and co-workers from Princeton University, closely followed by a vapor sensing application of optical waveguides. On third position a new large-area fabrication method of split-ring resonators has been demonstrated by the team of Harald Giessen (University of Stuttgart). Plasmonic effects are also presented on 4th and 5th position: investigating homogeneous near-field enhancements in a ring-shaped nanostructure, as well as a fundamental study of the plasmon modes in Au–Ag nanorods by Jianfang Wang (Hong Kong). After the great success of the Advanced Optical Materials section, we have been pushing to launch Advanced Optical Materials as a new, independent journal in January 2013. As an independent journal, Advanced Optical Materials will continue as a forum for high-quality research in the field of optical materials. As with all the journals in the “Advanced family”, we will form Advanced Optical Materials into a top-tier platform to share the latest develops in optical materials, incorporating thorough, impartial peer review and wide dissemination and maximum discoverability. You would like to see your work published in one of the first issues of the new Advanced Optical Materials journal? Please submit your paper through our online submission site and select Advanced Optical Materials from the drop-down list on www.manuscriptxpress.org/osm/. You can find more information about the journal and author guidelines on www.advopticalmat.de. We look forward to reading your next manuscript, and we'll be back in January for the next installment of cutting-edge discoveries in light-matter interactions as an independent journal issue. To be informed about the latest news regarding Advanced Optical Materials please sign up for our newsletter at www.advopticalmat.de, [email protected] on Twitter, and look out for news articles on optical topics on www.materialsviews.com. Please feel free to send us an Email ([email protected]) or meet us at the SPIE Photonics West meeting in San Francisco, February 2013. We thank you, our loyal readers, for your continued support and hope to maintain your interest in the future issues of Advanced Optical Materials.

Large Enhancement of Upconversion Luminescence of NaYF4:Yb3+/Er3+ Nanocrystal by 3D Plasmonic Nano‐Antennas

Plasmon-enhanced upconversion luminescence of NaYF4: Yb3+/Er3+ co-doped nanocrystals is investigated using a 3D plasmonic antenna architecture: a disk-coupled dots-on-pillar antenna array (D2PA). By tuning and optimizing the resonance frequency of the D2PA structure for upconversion luminescence, a 310-fold luminescence enhancement and an 8-fold reduction of the luminescence decay time are observed.

Plasmon-enhanced upconversion fluorescence in NaYF4:Yb/Er/Gd nanorods coated with Au nanoparticles or nanoshells

We investigate plasmon-enhanced upconversion (UC) fluorescence in Yb3+-Er3+-Gd+3 codoped sodium yttrium fluoride (NaYF4:Yb/Er/Gd) nanorods using gold nanoparticles or nanoshells. A simple method was proposed for the preparation of core/shell NaYF4/Au structures, with dispersed Au nanoparticles or uniform Au coating on the surface of the UC nanorod. Pure hexagonal-phase NaYF4:Yb/Er/Gd nanorods were synthesized via a liquid-solid reaction in oleic acid and ethanol solvent. A one-step approach was introduced to modify the hydrophobic surfaces of the as-deposited NaYF4:Yb/Er/Gd nanorods. After this surface modification, Au nanoparticles or nanoshells were successfully attached on the surfaces of NaYF4:Yb/Er/Gd nanorods. The as-deposited UC nanorods showed a strong UC emission in green and red bands under 980 nm laser excitation. The attachment of Au nanoparticles onto NaYF4:Yb/Er/Gd nanorods resulted in a more than three-fold increase in UC emissions, whereas the formation of continuous and compact Au shells around the nanorods suppressed the emissions. The related interaction mechanisms of the UC emission of NaYF4:Yb/Er/Gd nanorods with plasmon modes in Au nanostructures are analyzed and discussed.

Highly plasmon-enhanced upconversion emissions from Au@β-NaYF4:Yb,Tm hybrid nanostructures

Unselectively enhanced multicolour upconversion (UC) emissions and low pumping threshold were achieved in Au@β-NaYF(4):Yb,Tm hybrid nanostructures. This demonstrates that the plasmon field enhancement effect is the main reason for the improved UC emission efficiency.

Plasmon-Enhanced Upconversion in Single NaYF4:Yb3+/Er3+ Codoped Nanocrystals

In this Letter we report the plasmon-enhanced upconversion in single NaYF(4) nanocrystals codoped with Yb(3+)/Er(3+). Single nanocrystals and gold nanospheres are investigated and assembled in a combined confocal and atomic force microscope setup. The nanocrystals show strong upconversion emission in the green and red under excitation with a continuous wave laser in the near-infrared at 973 nm. By the use of the atomic force microscope, we couple single nanocrystals with gold spheres (30 and 60 nm in diameter) to obtain enhanced upconversion emission. An overall enhancement factor of 3.8 is reached. A comparison of time-resolved measurements on the bare nanocrystal and the coupled nanocrystal-gold sphere systems unveil that faster excitation as well as faster emission occurs in the nanocrystals.