ABSTRACT
There exists a wealth of means of efficient utilization of solar energy in nature, with photosynthesis of chlorophylls as a prime example. Separately, artificially structured plasmonic materials are versatile in light harvesting and energy conversion. Using a simple and scalable design of near-percolating silver nanostructures, we demonstrate that the light-harvesting efficiency of chlorophylls can be drastically enhanced by tuning the plasmon frequency of the constituent silver nanoparticles to coincide with the maximal photon flux of sunlight. In particular, we show that the photon upconversion efficiency can be readily enhanced by over 20 folds, with the room-temperature fluorescence quantum yield increased by a factor of 2.63. The underlying mechanism for the upconversion enhancement is attributed to a one-electron-per-photon anti-Stokes process, involving absorption of a characteristic phonon mode of the chlorophylls. These findings suggest that chlorophylls can serve as molecular building blocks for high-efficiency light harvesting and solar energy conversion.
Subject(s)
Chlorophyll/chemistry , Light , Metal Nanoparticles/chemistry , Nanostructures/chemistry , Photons , Silver/chemistry , Solar Energy , Surface Plasmon Resonance , Fluorescence , PhotosynthesisABSTRACT
We demonstrate tuning emission band of CdSe/ZnS semiconductor quantum dots (SQDs) closely-packed in the proximity of Ag nanorod array by dynamically adjusting exciton-plasmon interaction. Large red-shift is observed in two-photon luminescence (TPL) spectra of the SQDs when the longitudinal surface plasmon resonance (LSPR) of Ag nanorod array is adjusted to close to excitation laser wavelength, and the spectral red-shift of TPL reaches as large as 101 meV by increasing excitation power, which is slightly larger than full width at half-maximum of emission spectrum of the SQDs. The observed LSPR-dependent spectral shifting behaviors are explained by a theoretical model of plasmon-enhanced quantum-confined Stark effect. These observations could find the applications in dynamical information processing in active plasmonic and photonic nanodevices.
Subject(s)
Cadmium Compounds/chemistry , Nanotubes/chemistry , Quantum Dots , Selenium Compounds/chemistry , Silver/chemistry , Surface Plasmon Resonance/methods , Zinc Compounds/chemistry , Materials TestingABSTRACT
We investigate the optical response of a gold nanorod array coupled with a semicontinuous nanoparticle film. We find that, as the gold nanoparticle film is adjusted to the percolating regime, the nanorod-film hybrids are tuned into plasmonic Fano resonance, characterized by the coherent coupling of discrete plasmonic modes of the nanorod array with the continuum band of the percolating film. Consequently, optical transmission of the percolating film is substantially enhanced. Even more strikingly, electromagnetic fields around the nanorod array become much stronger, as reflected by 2 orders of magnitude enhancement in the avalanche multiphoton luminescence. These findings may prove instrumental in the design of various plasmonic nanodevices.
ABSTRACT
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.
Subject(s)
Energy Transfer , Nanotechnology/instrumentation , Nanowires/chemistry , Silver/chemistry , Absorption , Cadmium Compounds/chemistry , Quantum Dots , Selenium Compounds/chemistry , Semiconductors , Sulfides/chemistry , Zinc Compounds/chemistryABSTRACT
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.
Subject(s)
Optics and Photonics , Quantum Dots , Semiconductors , Energy Transfer , Fluorescence Resonance Energy Transfer/methods , Light , Luminescence , Metal Nanoparticles/chemistry , Microscopy, Electron, Transmission/methods , Models, Theoretical , Nanotechnology/methods , Physics/methods , Spectrophotometry/methodsABSTRACT
We used CdSe/ZnS quantum dots-ssDNA-fluorescent dye conjugates as bioprobes to detect micrococcal nuclease with high specificity and sensitivity, and further utilized the bioprobe to monitor the micrococcal nuclease activity in the culture medium of Staphylococcus aureus by fluorescence microscopy.
Subject(s)
Biosensing Techniques , Fluorescence Resonance Energy Transfer/methods , Micrococcal Nuclease/analysis , Quantum Dots , Cadmium Compounds/chemical synthesis , Cadmium Compounds/chemistry , Micrococcal Nuclease/metabolism , Nanotechnology , Rhodamines/chemistry , Spectrometry, Fluorescence , Staphylococcus aureus/chemistry , Zinc Compounds/chemistryABSTRACT
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.
