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ABSTRACT: We report the synthesis of 43-nm diameter Au nanocube dimers by using Ag(+) ions as competitive ligands to freeze l-cysteine-induced assembly process of the nanocubes to a desirable stage. Ascribed to the resonant interparticle coupling with an newly arising plasmon band at 710 nm and local field enhancement, the two-photon luminescence intensity of the Au nanocube dimers in solution was over 20 times stronger than that of the monomers in the wavelength range 555-620 nm. Furthermore, by coupling Raman tags onto the nanocube surface, a solution-based surface-enhanced Raman scattering (SERS) of the nanocube dimers had an enhancement factor of over 10 times compared to the isolated nanocubes. To sum up, with high stability in solution and attractive optical properties, the Au nanocube dimers have potential applications in in vivo bio-imaging and solution-based SERS.
Nanoscale 05/2013; · 5.91 Impact Factor
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ABSTRACT: The CdS/SiO<sub>2</sub> core/shell nanowires (NWs) with controlled shell thickness were successfully synthesized and subsequently heat-treated at 500 °C. The influences of silica shell coating and annealing processes on their optical properties have been investigated. Compared with original CdS NWs, the annealed CdS/SiO<sub>2</sub> NWs exhibited an enhanced band-edge emission with slowed photoluminescence lifetime, while the intensity of defect emission decreased. The results were ascribed to the surface passivation and recrystallization by shell coating and annealing. We believe our finding would help improving the optical properties of semiconductor NWs, and facilitate its applications in various realms, such as nanoscale emitter, sensor, and photoelectric device.
Optics Express 02/2013; 21(3):3253-3258. · 3.59 Impact Factor
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ABSTRACT: A new class of ratiometric fluorescence sensors composed of rare-earth (RE) compound nanotubes is described. Polyethylenimine-coated yttrium hydroxide fluoride nanotubes (YHF NTs) that were synthesized hydrothermally exhibit highly efficient fluorescence when doped with RE ions. The polyethylenimine on the NTs facilitates the incorporation of phosphors such as quantum dots or organic dyes onto the NT surface to produce dual-emitting nanocomposites which are excellent ratiometric fluorescence sensors. The phosphor layer and underlying tubes in the nanocomposites act as the indicator and reference probes, respectively. This ratiometric fluorescence method which can be applied to the detection of heavy metals in solutions, temperature sensing, and pH sensing boasts high sensitivity and selectivity as well as better accuracy than traditional intensity-based fluorescence methods.
Nanoscale 01/2013; · 5.91 Impact Factor
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Shan Liang,
Xiao-Li Liu,
Yue-Zhou Yang,
Ya-Lan Wang,
Jia-Hong Wang,
Zhong-Jian Yang,
Liang-Bing Wang,
Shuang-Feng Jia,
Xue-Feng Yu,
Li Zhou,
Jian-Bo Wang,
Jie Zeng, Qu-Quan Wang,
Zhenyu Zhang
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ABSTRACT: This paper describes a facile method for synthesis of Au-AgCdSe hybrid nanorods with controlled morphologies and spatial distributions. The synthesis involved deposition of Ag tips at the ends of Au nanorod seeds, followed by selenization of the Ag tips and overgrowth of CdSe on these sites. By simply manipulating the pH value of the system, the AgCdSe could selectively grow at one end, at both the ends or on the side surface of a Au nanorod, generating a mike-like, dumbbell-like, or toothbrush-like hybrid nanorod, respectively. These three types of Au-AgCdSe hybrid nanorods displayed distinct localized surface plasmon resonance and photoluminescence properties, demonstrating an effective pathway for maneuvering the optical properties of nanocrystals.
Nano Letters 09/2012; 12(10):5281-6. · 13.20 Impact Factor
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ABSTRACT: The complex magnetic dipole plasmon couplings in double split-ring resonators are investigated. Two split peaks in the absorption spectrum of these coupled systems are observed, but even the shorter-wavelength resonance peak can be redshifted compared to the peaks of individual rings. The magnetic plasmon fields outside rings are found to play an important role in these strong couplings. Because of them, both bonding and antibonding plasmon hybridizations occur at each split peak. When bonding coupling effects are stronger than those of antibonding ones, this abnormal splitting behavior appears. When the coupling between rings becomes weaker, the splitting phenomenon tends to be normal.
Optics Letters 09/2012; 37(17):3675-7. · 3.40 Impact Factor
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ABSTRACT: We investigate the cooperative effects of two optical dipole antennas that are coupled to a finite Au nanowire acting as plasmonic Fabry-Pérot (F-P) cavity. The coherent coupling between one single antenna and the F-P cavity can result in Fano resonance, and the coupling strength is antenna position dependent. For two antennas coupled to the F-P cavity, constructive or destructive interference between antennas could be achieved by adjusting their positions along the F-P cavity. Consequently, the Fano resonance will become stronger or weaker correspondingly.
Nanoscale 07/2012; 4(17):5308-11. · 5.91 Impact Factor
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ABSTRACT: We theoretically investigated optical third-order nonlinearity of a coherently coupled exciton-plasmon hybrid system under a strong control field with a weak probe field. The analytic formulas of exciton population and effective third-order optical susceptibility of the hybrid of a metal nanoparticle (MNP) and a semiconductor quantum dot (SQD) were deduced. The bistable exciton population and the induced bistable nonlinear absorption and refraction response were revealed. The bistability region can be tuned by adjusting the size of metal nanoparticle, interparticle distance and intensity of control field. Our results have perspective applications in optical information processing based on resonant coupling of exciton-plasmon.
Optics Express 01/2012; 20(2):1856-61. · 3.59 Impact Factor
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ABSTRACT: Semiconductor nanowire (NW) cavities with tailorable optical modes have been used to develop nanoscale oscillators and amplifiers in microlasers, sensors, and single photon emitters. The resonance modes of NW could be tuned by different boundary conditions. However, continuously and reversibly adjusting resonance modes and improving Q-factor of the cavity remain a great challenge. We report a method to modulate resonance modes continuously and reversibly and improve Q-factor based on surface plasmon-exciton interaction. By placing single Ag nanoparticle (NP) nearby a CdS NW, we show that the wavelength and relative intensity of the resonance modes in the NW cavity can systematically be tuned by adjusting the relative position of the Ag NP. We further demonstrate that a 56% enhancement of Q-factor and an equivalent π-phase shift of the resonance modes can be achieved when the Ag NP is located near the NW end. This hybrid cavity has potential applications in active plasmonic and photonic nanodevices.
Nano Letters 09/2011; 11(10):4270-4. · 13.20 Impact Factor
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ABSTRACT: The optical emission response of a single nano-emitter coupled with a plasmonic nanorod dimer is investigated, where the short and long nanorods in the dimer support dipolar and quadrupolar plasmon resonance, repsectively. Fano resonances are observed with a nano-emitter being placed at either apex of the dimer. However, no Fano resonance is seen when the nano-emitter is placed in the gap of the dimer. Bonding and antibonding dipolar-quadrupolar plasmon couplings are closely related to the Fano resonances in this dimer system.
Applied Physics Letters 08/2011; 99(8):081107-081107-3. · 3.84 Impact Factor
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ABSTRACT: We theoretically investigate the plasmon coupling in metallic nanorod dimers. A pronounced dip is found in the extinction spectrum due to plasmonic Fano resonance, which is induced by destructive interference between the bright dipole plasmon of a short nanorod and the dark quadrupole plasmon of a long nanorod. This Fano interference can also be explained as the coupling between the bright and dark modes both supported by the whole dimer. The Fano resonance can be tuned by adjusting the spatial or spectral separation between two nanorods in the dimer.
Optics Letters 05/2011; 36(9):1542-4. · 3.40 Impact Factor
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ABSTRACT: We numerically investigate the resonant spectral features of the two-dimensional stacked double-disk array. Narrow plasmon line shapes are observed on resonance spectra which are similar to the case of single-disk array. The electric field shows that the narrow plasmon modes are produced by the dark plasmon mode coupling to the diffraction which may be due to the retardation effect. The narrow mode and the dark mode overlap on resonance spectra, resulting in a Fano-like spectrum. The intensities of the electric fields for these narrow modes arising from the dark mode coupling are much stronger than that of the bright modes.
Applied Physics Letters 04/2011; 98(17):173111-173111-3. · 3.84 Impact Factor
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Advanced Functional Materials 03/2011; 21(10):1788 - 1794. · 10.18 Impact Factor
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ABSTRACT: 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.
Nano Letters 01/2011; 11(1):49-55. · 13.20 Impact Factor
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ABSTRACT: We investigate the far-field scattering property of a single Ag nanoring. Under oblique excitation, two-focus scatterings with distinct intensities were observed. We show that the two-focus scatterings result from the interference of far-field scattering light from the ring circumference, and the local field enhancement effect of surface plasmons plays the key role in the focus intensity. By finite difference time domain and numerical integer methods, we calculated far-field scattering and surface plasmons’ distributions, and the results are in good agreement with the experiment.
Applied Physics Letters 12/2010; 97(26):261107-261107-3. · 3.84 Impact Factor
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ABSTRACT: We report the development of neurotoxin-mediated upconversion nanoprobes for tumor targeting and visualization in living animals. The nanoprobes were synthesized by preparing polyethylenimine-coated hexagonal-phase NaYF(4):Yb,Er/Ce nanoparticles and conjugating them with recombinant chlorotoxin, a typical peptide neurotoxin that could bind with high specificity to many types of cancer cells. Nanoprobes that specifically targeted glioma cells were visualized by laser scanning upconversion fluorescence microscopy. Good probe biocompatibility was displayed with cellular and animal toxicity determinations. Animal studies were performed using Balb-c nude mice injected intravenously with the nanoprobes. The obtained high-contrast images demonstrated highly specific tumor binding and direct tumor visualization with bright red fluorescence under 980-nm near-infrared irradiation. The high sensitivity and high specificity of the neurotoxin-mediated upconversion nanoprobes and the simplification of the required optical device for tumor visualization suggest an approach that may help improve the effectiveness of the diagnostic and therapeutic modalities available for tumor patients.
Biomaterials 11/2010; 31(33):8724-31. · 7.40 Impact Factor
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Zhang-Kai Zhou,
Min Li,
Zhong-Jian Yang,
Xiao-Niu Peng,
Xiong-Rui Su,
Zong-Suo Zhang,
Jian-Bo Li,
Nam-Chol Kim,
Xue-Feng Yu,
Li Zhou,
Zhong-Hua Hao, Qu-Quan Wang
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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.
ACS Nano 09/2010; 4(9):5003-10. · 10.77 Impact Factor
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ABSTRACT: We investigated the scattering property of a single plasmon interacting with two quantum dots coupled to one-dimensional surface plasmonic waveguide. We demonstrated that the transmission of a single plasmon could be switched on or off by adjusting spectral detuning and controlling spatial separation of the two quantum dots. These transport properties of the nanosystem could find the applications in plasmonic nanodevices and quantum information processing.
Applied Physics Letters 09/2010; · 3.84 Impact Factor
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ABSTRACT: We theoretically investigated the plasmon interferences and hybridization in the Au–Ag nanorod heterodimers. Twinned Fanolike profiles are observed in the absorption cross sections of the gold and silver nanorods in the heterodimers, the Fano factors of which have the opposite signs near the antibonding resonances, which are found to be induced by the destructive interferences of two hybridized local surface plasmons. Both the value and sign of the Fano factors could be tuned by adjusting rod-lengths, which could find the applications in the design of plasmonic nanodevices.
Applied Physics Letters 03/2010; 96(13):131113-131113-3. · 3.84 Impact Factor
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ABSTRACT: 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.
Applied Physics Letters 03/2010; 96(12):123104-123104-3. · 3.84 Impact Factor
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ABSTRACT: The stimulated amplifications of surface plasmons (SPs) propagating along a single silver nanoring is theoretically investigated by considering the interactions between SPs and activated semiconductor quantum dots (SQDs). Threshold condition for the stimulated amplifications, the SP density as a function of propagation length and the maximum SP density are obtained. The SPs can be nonlinearly amplified when the pumping rate of SQDs is larger than the threshold, and the maximum value of SP density increases linearly with the pumping rate of SQDs.
Optics Express 03/2010; 18(5):4006-11. · 3.59 Impact Factor
