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ABSTRACT: A low-cost and efficient photocatalytic reactor for environmental treatment and green technology was presented. ZnO nanorods firmly growing on polycarbonate optical disk substrate are generally perpendicular to the substrate as the immobilized photocatalyst of the spinning disk reactor. The photocatalytic efficiency and durability of the ZnO nanorods are effectively demonstrated.
Optics Express 03/2013; 21(6):7240-9. · 3.59 Impact Factor
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ABSTRACT: Plasmonic photocatalysis has recently facilitated the rapid progress in enhancing photocatalytic efficiency under visible light irradiation, increasing the prospect of using sunlight for environmental and energy applications such as wastewater treatment, water splitting and carbon dioxide reduction. Plasmonic photocatalysis makes use of noble metal nanoparticles dispersed into semiconductor photocatalysts and possesses two prominent features-a Schottky junction and localized surface plasmonic resonance (LSPR). The former is of benefit to charge separation and transfer whereas the latter contributes to the strong absorption of visible light and the excitation of active charge carriers. This article aims to provide a systematic study of the fundamental physical mechanisms of plasmonic photocatalysis and to rationalize many experimental observations. In particular, we show that LSPR could boost the generation of electrons and holes in semiconductor photocatalysts through two different effects-the LSPR sensitization effect and the LSPR-powered bandgap breaking effect. By classifying the plasmonic photocatalytic systems in terms of their contact form and irradiation state, we show that the enhancement effects on different properties of photocatalysis can be well-explained and systematized. Moreover, we identify popular material systems of plasmonic photocatalysis that have shown excellent performance and elucidate their key features in the context of our proposed mechanisms and classifications.
Reports on Progress in Physics 03/2013; 76(4):046401. · 14.72 Impact Factor
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Hao Ming Chen,
Chih Kai Chen,
Ming Lun Tseng,
Pin Chieh Wu,
Chia Min Chang,
Liang-Chien Cheng,
Hsin Wei Huang,
Ting Shan Chan,
Ding-Wei Huang,
Ru-Shi Liu, Din Ping Tsai
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ABSTRACT: A new fabrication strategy in which Ag plasmonics are embedded in the interface between ZnO nanorods and a conducting substrate is experimentally demonstrated using a femtosecond-laser (fs-laser)-induced plasmonic ZnO/Ag photoelectrodes. This fs-laser fabrication technique can be applied to generate patternable plasmonic nanostructures for improving their effectiveness in hydrogen generation. Plasmonic ZnO/Ag nanostructure photoelectrodes show an increase in the photocurrent of a ZnO nanorod photoelectrodes by higher than 85% at 0.5 V. Both localized surface plasmon resonance in metal nanoparticles and plasmon polaritons propagating at the metal/semiconductor interface are available for improving the capture of sunlight and collecting charge carriers. Furthermore, in-situ X-ray absorption spectroscopy is performed to monitor the plasmonic-generating electromagnetic field upon the interface between ZnO/Ag nanostructures. This can reveal induced vacancies on the conduction band of ZnO, which allow effective separation of charge carriers and improves the efficiency of hydrogen generation. Plasmon-induced effects enhance the photoresponse simultaneously, by improving optical absorbance and facilitating the separation of charge carriers.
Small 02/2013; · 8.35 Impact Factor
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Wei Ting Chen,
Ming Lun Tseng,
Chun Yen Liao,
Pin Chieh Wu,
Shulin Sun,
Yao-Wei Huang,
Chia Min Chang,
Chung Hao Lu,
Lei Zhou,
Ding-Wei Huang,
Ai Qun Liu, Din Ping Tsai
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ABSTRACT: We fabricated a three-dimensional five-layered plasmonic resonant cavity by low-cost, efficient and high-throughput femtosecond laser-induced forward transfer (fs-LIFT) technique. The fabricated cavity was characterized by optical measurements, showing two different cavity modes within the measured wavelength region which is in good agreement with numerical simulations. The mode volume corresponding to each resonance is found to be squeezed over 10<sup>4</sup> smaller than the cube of incident wavelength. This property may facilitate many applications in integrated optics, optical nonlinearities, and luminescence enhancement, etc.
Optics Express 01/2013; 21(1):618-25. · 3.59 Impact Factor
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ABSTRACT: Toroidal shapes are often found in bio-molecules, viruses, proteins and fats, but only recently it was proved experimentally that toroidal structures can support exotic high-frequency electromagnetic excitations that are neither electric or magnetic multipoles. Such excitations, known as toroidal moments, could be playing an important role in enhancing inter-molecular interaction and energy transfer due to its higher electromagnetic energy confinement and weaker coupling to free space. Using a model toroidal metamaterial system, we show that coupling optical gain medium with high Q-factor toroidal resonance mode can enhance the single pass amplification to up to 65 dB. This offers an opportunity of creating the "toroidal" lasing spaser, a source of coherent optical radiation that is fueled by toroidal plasmonic oscillations in the nanostructure.
Scientific Reports 01/2013; 3:1237.
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ABSTRACT: Using the curved arrangement of Au nanobumps, the scattering of surface plasmon waves are transformed into spots at desired locations and altitudes in three-dimensional space. The light can be modulated into desired light patterns. This work is very promising for compact plasmonic circuitry, projection, live-cell imaging, optical sensing, and holography.
Advanced Materials 12/2012; · 13.88 Impact Factor
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Shulin Sun,
Kuang-Yu Yang,
Chih-Ming Wang,
Ta-Ko Juan,
Wei Ting Chen,
Chun Yen Liao,
Qiong He,
Shiyi Xiao,
Wen-Ting Kung,
Guang-Yu Guo,
Lei Zhou, Din Ping Tsai
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ABSTRACT: We combine theory and experiment to demonstrate that a carefully designed gradient meta-surface supports high-efficiency anomalous reflections for near infrared light following the generalized Snell's law, and the reflected wave becomes a bounded surface wave as the incident angle exceeds a critical value. Compared to previously fabricated gradient meta-surfaces in infra-red regime, our samples work in a shorter wavelength regime with a broad bandwidth (750-900nm), exhibit a much higher conversion efficiency (~80%) to the anomalous reflection mode at normal incidence, and keep light polarization unchanged after the anomalous reflection. Finite-difference-time-domain (FDTD) simulations are in excellent agreement with experiments. Our findings may lead to many interesting applications, such as anti-reflection coating, polarization and spectral beam splitters, high-efficiency light absorber, and surface plasmon coupler.
Nano Letters 11/2012; · 13.20 Impact Factor
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Ming Lun Tseng,
Chia Min Chang,
Bo Han Chen,
Yao-Wei Huang,
Cheng Hung Chu,
Kuang Sheng Chung,
Yen Ju Liu,
Hung Guei Tsai,
Nien-Nan Chu,
Ding-Wei Huang,
Hai-Pang Chiang, Din Ping Tsai
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ABSTRACT: Using femtosecond laser-induced forward transfer techniques we have fabricated gold dots and nanoparticles on glass substrates, as well as nanobumps on gold thin film. The surface morphologies of these structures with different laser fluences and film thicknesses are investigated. We also study the focusing and defocusing properties of the nanofence-an arranged nanobump pattern-by the total-internal reflection microscope. Observations reveal that surface plasmon waves can be highly directed and focused via this nanofence pattern. Results are in good agreement with the simulation results using the finite-element method and demonstrate the potential applications of these nanophotonic devices. Furthermore, we utilize high laser energy to fabricate plasmonic waveguides, and also succeed in transferring the waveguides to another substrate. The attenuation rates of the light propagating in the waveguides are observed to achieve 0.31 dB μm(-1) and 0.48 dB μm(-1) on the target and receiver sides, respectively.
Nanotechnology 11/2012; 23(44):444013. · 3.98 Impact Factor
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ABSTRACT: Solar wastewater treatment based on photocatalytic reactions is a green process that utilizes renewable energy resources and minimizes secondary pollution. Reactor design plays an important role in promoting treatment efficiency and throughput density (based on unit volume of the reactor).
A rotating disk reactor that significantly increases the process efficiency has been designed and evaluated for application to photocatalytic decomposition of dye pollutants in aqueous solutions. In this process, a novel multi-layer rotating disk reactor (MLRDR) was presented. Photocatalyst (TiO(2)) particles are immobilized on the surfaces of disks. Within each layer of the reactor, methyl orange aqueous solution is allowed to flow from the center of the disk in a radial direction along the surface of the disk, which is rotating at high speed and is irradiated with UV lamps. The effluent is then directed to the center of another layer that lies underneath. Up to four stacked layers have been tested in this study, and the effects due to the number of the layers and volumetric flow rate on reaction conversion are investigated.
The efficiency of this photocatalytic reactor exhibits complex dependence on these parameters. With selected operating conditions, conversions greater than 95% can be achieved within seconds of residence time. Design equations of the reactor have been derived based on fluid dynamics and kinetic models, and the simulation results show promising scale-up potential of the reactor.
Environmental Science and Pollution Research 11/2012; 19(9):3743-50. · 2.65 Impact Factor
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ABSTRACT: We propose an innovative active imaging device named gain-assisted hybrid-superlens hyperlens and examine its resolving power theoretically. This semi-cylindrical device consists of a core of semi-cylindrical super-lens and a half cylindrical outer shell of hyperlens. Both the superlens and hyperlens parts of the device are appropriately designed multi-layered metal-dielectric structures having indefinite eigenvalues of dielectric tensors. The dielectric layers of the hyperlens are doped with Coumarin, which play the role of gain medium. The gain medium is analyzed thoroughly using a generic four-level system model, and the permittivity of the gain medium is extracted from this analysis for simulating the imaging characteristics of the device. According to our simulation at wavelength of 365 nm, an excellent resolution power much better than the diffraction limit value can be achieved.
Optics Express 09/2012; 20(20):22953-60. · 3.59 Impact Factor
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ABSTRACT: The GaN-based membrane high contrast grating (HCG) reflectors have been fabricated and investigated. The structural parameters including grating periods, grating height, filling factors and air-gap height were calculated to realize high reflectivity spectra with broad bandwidth by the rigorous coupled-wave analysis and finite-difference time-domain method. Based on the optimized simulation results, the GaN-based membrane HCGs were fabricated by e-beam lithography and focused-ion beam process. The fabricated GaN-based membrane HCG reflectors revealed high reflectivity at 460 nm band with large stopband width of 60 nm in the TE polarization measured by using the micro-reflectivity spectrometer. The experimental results also showed a good agreement with simulated ones. We believe this study will be helpful for development of the GaN-based novel light emitting devices in the blue or UV region.
Optics Express 08/2012; 20(18):20551-7. · 3.59 Impact Factor
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Hao Ming Chen,
Chih Kai Chen,
Chih-Jung Chen,
Liang-Chien Cheng,
Pin Chieh Wu,
Bo Han Cheng,
You Zhe Ho,
Ming Lun Tseng,
Ying-Ya Hsu,
Ting-Shan Chan,
Jyh-Fu Lee,
Ru-Shi Liu, Din Ping Tsai
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ABSTRACT: Artificial photosynthesis using semiconductors has been investigated for more than three decades for the purpose of transferring solar energy into chemical fuels. Numerous studies have revealed that the introduction of plasmonic materials into photochemical reaction can substantially enhance the photo response to the solar splitting of water. Until recently, few systematic studies have provided clear evidence concerning how plasmon excitation and which factor dominates the solar splitting of water in photovoltaic devices. This work demonstrates the effects of plasmons upon an Au nanostructure-ZnO nanorods array as a photoanode. Several strategies have been successfully adopted to reveal the mutually independent contributions of various plasmonic effects under solar irradiation. These have clarified that the coupling of hot electrons that are formed by plasmons and the electromagnetic field can effectively increase the probability of a photochemical reaction in the splitting of water. These findings support a new approach to investigating localized plasmon-induced effects and charge separation in photoelectrochemical processes, and solar water splitting was used herein as platform to explore mechanisms of enhancement of surface plasmon resonance.
ACS Nano 07/2012; 6(8):7362-72. · 10.77 Impact Factor
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ABSTRACT: We provide a simple physical proof of the reciprocity theorem of classical
electrodynamics in the general case of material media that contain linearly
polarizable as well as linearly magnetizable substances. The excitation source
is taken to be a point-dipole, either electric or magnetic, and the monitored
field at the observation point can be electric or magnetic, regardless of the
nature of the source dipole. The electric and magnetic susceptibility tensors
of the material system may vary from point to point in space, but they cannot
be functions of time. In the case of spatially non-dispersive media, the only
other constraint on the local susceptibility tensors is that they be symmetric
at each and every point. The proof is readily extended to media that exhibit
spatial dispersion: For reciprocity to hold, the electric susceptibility tensor
Chi_E_mn that relates the complex-valued magnitude of the electric dipole at
location r_m to the strength of the electric field at r_n must be the transpose
of Chi_E_nm. Similarly, the necessary and sufficient condition for the magnetic
susceptibility tensor is Chi_M_mn = Chi^T_M_nm.
05/2012;
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Ming Lun Tseng,
Yao-Wei Huang,
Min-Kai Hsiao,
Hsin Wei Huang,
Hao Ming Chen,
Yu Lim Chen,
Cheng Hung Chu,
Nien-Nan Chu,
You Je He,
Chia Min Chang,
Wei Chih Lin,
Ding-Wei Huang,
Hai-Pang Chiang,
Ru-Shi Liu,
Greg Sun, Din Ping Tsai
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ABSTRACT: Using a femtosecond laser, we have transformed the laser-direct-writing technique into a highly efficient method that can process AgO(x) thin films into Ag nanostructures at a fast scanning rate of 2000 μm(2)/min. The processed AgO(x) thin films exhibit broad-band enhancement of optical absorption and effectively function as active SERS substrates. Probing of the plasmonic hotspots with dyed polymer beads indicates that these hotspots are uniformly distributed over the treated area.
ACS Nano 05/2012; 6(6):5190-7. · 10.77 Impact Factor
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ABSTRACT: It is demonstrated that the sensitivity of surface plasmon resonance phase-interrogation biosensor can be enhanced by using
silver nanoparticles. Silver nanoparticles were fabricated on silver films by using thermal evaporation. Sizes of silver nanoparticles
on silver thin film can be tuned by controlling the deposition parameters of thermal evaporation. By using surface plasmon
resonance heterodyne interferometey to measure the phase difference between the p and s polarization of incident light, we have demonstrated that sensitivity of glucose detection down to the order of 10−8 refractive index units can be obtained.
KeywordsSurface plasmons–Phase measurement–Silver nanoparticles–Biosensor
Plasmonics 05/2012; 6(1):29-34. · 2.99 Impact Factor
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ABSTRACT: We present a comparative study on the enhancement of photoluminescence and Raman processes by a single metal nanoparticle. Taking an analytical approach, we show the physics behind strikingly different orders of magnitude in enhancement that have been observed, provide fundamental explanation for not observing quenching of Raman processes, and outline the path to optimization of both photoluminescence and Raman enhancement.
Optics Letters 05/2012; 37(9):1583-5. · 3.40 Impact Factor
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ABSTRACT: Near field optical properties and surface plasmon resonances on a pair of silver-shell nanocylinder and nanochain waveguides
with different core–shell patterns which interact with incident plane wave along chain axis are numerically investigated by
using the finite element method. Simulation results show that the peak wavelengths and resonant field enhancements are highly
tunable by using the nanoshell particles instead of solid ones, revealing a critical relationship among the wavelengths and
illuminated direction of incident light, interparticle spacing, radii, and medium of dielectric holes and the patterns of
chain waveguides. Besides, nanochain waveguides with different patterns of core–shell that are operated on resonant multipolar
modes can provide higher propagation intensities and the transmission ability can be increased by decreasing the size of nanocylinders
along the chain axis.
KeywordsSurface plasmon resonances–Dielectric holes–Nanochain–Nanoscale optics–Modeling and simulation
Journal of Nanoparticle Research 04/2012; 13(9):3939-3949. · 3.29 Impact Factor
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ABSTRACT: The dependence of nanoparticle size on surface-enhanced Raman scattering (SERS) from silver film over nanospheres substrate
is studied. For a range of nanosphere sizes from 430 to 1,500nm, optimum SERS signal is obtained with a nanosphere size of
1,000nm at an excitation wavelength of 532nm. We have clarified the physical origin of this optimization in an unambiguious
way as due to resonant plasmonic excitations from 3D finite-difference time-domain simulations, as well as with the assistance
of UV-visible reflectance spectrum.
KeywordsSurface-enhanced Raman scattering (SERS)–Nanosphere lithography (NSL)–Silver film over nanospheres (AgFON)–Enhanced factor (EF)–Finite-difference time-domain (FDTD)
Plasmonics 04/2012; 6(2):201-206. · 2.99 Impact Factor
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ABSTRACT: Scattering field interactions and surface plasmon resonance in a coupled silver nanodumbbell (a pair of silver nanosphere
connected by a silver nanobar) are simulated by using the three-dimensional finite-element method. The enhancement of scattering
cross section which exhibits a blue-shifted is associated with the diameter of the silver nanobar and the wavelength of incident
light. Interestingly, the generated optical cloud exceeds two times of the nanodumbbell size which can be turned by varying
the diameter of the silver nanobar.
Applied Physics A 04/2012; 104(3):801-805. · 1.63 Impact Factor
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ABSTRACT: Dispersion properties, birefringence and confinement loss between the circular air-hole photonic crystal fiber (CAHPCF) and
rotational elliptical air-hole photonic crystal fiber (REAHPCF) are investigated numerically by means of a plane-wave expansion
method and a finite element method. Results show that the performances of REAHPCF on flatter dispersion curve, single mode,
high birefringence and low confinement loss is better than that of CAHPCF.
Applied Physics A 04/2012; 104(3):857-861. · 1.63 Impact Factor
