Xiong-Rui Su

Plasmon-mediated radiative energy transfer across a silver nanowire array via resonant transmission and subwavelength imaging.

Efficient plasmon-mediated excitation energy transfer between the CdSe/ZnS semiconductor quantum dots (QDs) across the silver nanowire array up to 560 nm in length is observed. The subwavelength imaging and spectral response of the silver nanowire arrays with near-field point-source excitations are revealed by theoretical simulations. Our studies demonstrate three advantages of the nanosystem: efficient exciton-plasmon conversion at the input side of the array through near-field strong coupling, directional waveguidance and resonant transmission via half-wave plasmon modes of the nanowire array, and subwavelength imaging at the output side of the array. These advantages allow a long-range radiative excitation energy transfer with a high efficiency and a good directionality.

Multipole-plasmon-enhanced förster energy transfer between semiconductor quantum dots via dual-resonance nanoantenna effects

Ag nanoparticles with dipole and quadrupole plasmon are employed as dual-resonant nanoantenna to enhance both “receiving” and “emitting” fields resonantly. Strong enhancement of photoluminescence (PL) and highly efficient plasmon-assisted Forster energy transfer between CdSe quantum dots are demonstrated by employing Ag dual-resonant nanoantenna and micro-PL spectroscopy. The collaboration effect of quadrupole and dipole plasmon of Ag dual-resonant nanoantenna could find applications in plasmonics such as biosensoring and optical information processing.

Plasmon-enhanced Förster energy transfer between semiconductor quantum dots: multipole effects

We experimentally demonstrated plasmon-assisted energy transfer (ET) between CdSe semiconductor quantum dots (QDs) self-assembled in a monolayer by using time-resolved micro-photoluminescence (PL) technique. The enhancements of PL intensity and ET efficiency were manipulated by adjusting thickness (Delta) of SiO(2) coating on large Ag nanoparticles. The PL enhancement factor of the acceptor QDs and the PL intensity ratio of acceptor-to-donor reached their maxima approximately 47 and approximately 14 when Delta = 7 nm, the corresponding ET efficiency reached 86%. We also presented theoretical analysis based on the rate equation. The theoretical calculations agreed with experimental data and revealed interesting physics of multipole effect, and metal nanoparticle induced quench effect and plasmon-enhanced Förster ET.

Plasmonic interferences and optical modulations in dark-bright-dark plasmon resonators

We fabricated dark-bright-dark plasmon resonators, investigated enhanced-transmission induced by plasmon transfer from the bright mode to the dark modes. Furthermore, we demonstrated interferences between dark plasmons excited by the near-field bright plasmons and directly excited by slantwise incident light, which leads to selective storage of excited energy in one of the two dark plasmon cells in the resonators by adjusting the phase between signal and control sources. This could find the applications in all-optical modulations.

High temperature sensitivity of manganese-assisted excitonic photoluminescence from inverted core/shell ZnSe:Mn/CdSe nanocrystals

We report efficient and long-lived exciton photoluminescence (PL) from inverted core/shell ZnSe:Mn/CdSe nanocrystals (NCs) at room temperature. Contrary to low temperature-sensitivity of Mn2+ PL from ZnSe:Mn/ZnSe NCs, the Mn2+-assisted excitonic PL from the ZnSe:4%Mn/CdSe NCs exhibits unusually high temperature-sensitivity (−2.4% per K) in the temperature range 298–334 K, which is even higher than that of the pure excitonic PL from the undoped ZnSe/CdSe NCs. Such unexpected temperature-dependence of the Mn2+-assisted excitonic PL is well explained by the deduced exciton rate equation involving the exciton-Mn2+ resonant energy transfer in the ZnSe:Mn/CdSe NCs.

Sublinear and superlinear photoluminescence from Nd doped anodic aluminum oxide templates loaded with Ag nanowires

We first time prepared Nd(3+) ions doped anodic aluminum oxide (Nd:AAO) templates, reported linear, sublinear and superlinear photoluminescence (PL) from Nd:AAO templates loaded with Ag nanowires in different excitation power regions, in which, the excitation laser with wavelength 805 nm resonantly pumped the population to (4)F5/2 states of Nd(3+), and the radiative transitions (4)F(3/2) -->(4)I(9/2) of Nd(3+) centered at 880 nm. The excitation power dependences of emission polarization ratio and the spectral width were also investigated. The observed nonlinear amplifications of the PL intensity implied strong interaction between randomly-dispersed Nd(3+) ions and ordered-arrayed Ag nanowires in AAO templates.

Photochromism and two-photon luminescence of Ag-TiO 2 granular composite films activated by near infrared ps/fs pulses

We reported photochromism and largely enhanced visible two-photon luminescence (TPL) of Ag-TiO(2) granular composite films by using ps/fs laser at the wavelength of 800 nm. Three types of photochromism spectra were observed when the Ag atom fraction are less than, comparable to and larger than the percolation threshold. The strong surface-plasmon-resonance enhanced visible TPL emissions near Ag(2)O transition band from the photoactivated Ag-TiO(2) samples were also observed. Furthermore, we found that the TPL intensity saturatedly increased while the absorbance at 800 nm exponentially decreased with the same rate as the increasing of photoactivation time, which means that both photochromism and TPL of Ag-TiO(2) composite films are originated from the photo-oxidation of Ag to Ag(+). These observations exhibit the multifunctional features of Ag nanoparticle materials.

LOCALIZED SURFACE PLASMON OF THIN GOLD FILM WITH PERIODIC ARRAYS OF NANOHOLES

The localized surface plasmon (LSP) resonances properties of periodic arrays of nanoholes in thin gold films are investigated by using the method of discrete dipole approximation (DDA). The surface plasmon polaritons (SPPs) play important roles in amplification or suppression of the LSP resonances in the film. The LSP-SPP coupling is affirmed based on the extinction spectra calculated by the DDA. The intensity of the LSP resonances can be controlled through changing the edge-to-edge separation distances between nanoholes, the number and the diameter of the nanoholes. The calculations also indicate that the LSP resonance peak decreases with increasing the thickness of the gold film.

CHARGE TRANSFER FROM MONOLAYERED CdSe/ZnS QUANTUM DOTS TO C60

The interaction between C60 and quantum dots (QDs) has attracted much attention recently due to its potential applications in solar cells, for example, as a promising renewable energy source. In this paper, monolayer self-assembled CdSe/ZnS core/shell QDs films were prepared and drop-coated with different amounts of C60. A significant photoluminescence quenching and an emission lifetime reduction were observed in the QDs-C60 composite films, and the quenching efficiency was increased with the increasing of the C60 content. Together with the reduced emission lifetime, the results here provide direct evidence for the charge transfer process in the QDs-C60 system.