Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 24
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
ACS Appl Mater Interfaces ; 11(29): 26243-26249, 2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31283173

RESUMO

Atomically thin membranes of two-dimensional (2-D) transition-metal dichalcogenides (TMDCs) have distinct emission properties, which can be utilized for realizing ultrathin optoelectronic integrated systems in the future. Growing a large-area and strain-reduced monolayer 2-D material on a three-dimensional (3-D) substrate with microstructures or nanostructures is a crucial technique because the electronic band structure of TMDC atomic layers is strongly affected by the number of stacked layers and strain. In this study, a large-area and strain-reduced MoS2 monolayer was fabricated on a 3-D substrate through a two-step growth procedure. The material characteristics and optical properties of monolayer TMDCs fabricated on the nonplanar substrate were examined. The growth of monolayer MoS2 on a cone-shaped sapphire substrate effectively reduced the tensile strain induced by the substrate by decreasing the thermal expansion mismatch between the 2-D material and the substrate. Monolayer MoS2 grown on the nonplanar substrate exhibited uniform strain reduction and luminescence intensity. The fabrication of monolayer MoS2 on a nonplanar substrate increased the light extraction efficiency. In the future, large-area and strain-reduced 2-D TMDC materials grown on a nonplanar substrate can be employed as novel light-emitting devices for applications in lighting, communication, and displays for the development of ultrathin optoelectronic integrated systems.

2.
Opt Lett ; 44(6): 1512-1515, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30874689

RESUMO

In this work, for the first time, to the best of our knowledge, an anomalous dispersion CMOS-compatible Ta2O5 waveguide was realized, and broadband on-chip supercontinuum generation (SCG) was accordingly demonstrated. When pumped at a center wavelength of 1056 nm with pulses of 100 fs duration and peak power of 396 W, a supercontinuum ranging from 585 nm to 1697 nm was generated, comprising a bandwidth of more than 1.5 octaves and leading to an efficient SCG source. The excellent performance for Ta2O5 to generate SCG benefits mainly from its high nonlinear refractive index, which enhances the efficiency of the nonlinear conversion process.

3.
Int J Nanomedicine ; 14: 181-193, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30613145

RESUMO

Purpose: A biocompatible nanocomplex system co-encapsulated with gold nanorods (AuNRs) and doxorubicin (DOX) was investigated for its potentials on the combined photothermal- and chemotherapy. Materials and methods: Hydrophobic AuNRs were synthesized by the hexadecyltrimethyl-ammonium bromide (CTAB)-mediated seed growth method, and then, they received two-step surface modifications of polyethylene glycol (PEG) and dodecane. The AuNR/DOX/poly(lactic-co-glycolic acid) (PLGA) nanocomplexes were prepared by emulsifying DOX, AuNR, and PLGA into aqueous polyvinyl alcohol solution by sonication. Human serum albumin (HSA) was used to coat the nanocomplexes to afford HSA/AuNR/DOX-PLGA (HADP). Size and surface potential of the HADP nanocomplexes were determined by using a Zetasizer. Cytotoxicity and cellular uptake of the HADP were analyzed by using MTT assay and flow cytometry, respectively. In vitro anticancer effects of the HADP were studied on various cancer cell lines. To assess the therapeutic efficacy, CT26 tumor-bearing mice were intravenously administered with HADP nanocomplexes and laser treatments, followed by monitoring of the tumor growth and body weight. Results: Size and surface potential of the HADP nanocomplexes were 245.8 nm and -8.6 mV, respectively. Strong photothermal effects were verified on the AuNR-loaded PLGA nanoparticles (NPs) in vitro. Rapid and repeated drug release from the HADP nanocomplexes was successfully achieved by near-infrared (NIR) irradiations. HSA significantly promoted cellular uptake of the HADP nanocomplexes to murine colon cancer cells as demonstrated by cell imaging and flow cytometric studies. By combining photothermal and chemotherapy, the HADP nanocomplexes exhibited strong synergistic anticancer effects in vitro and in vivo. Conclusion: An NIR-triggered drug release system by encapsulating hydrophobic AuNR and DOX inside the PLGA NPs has been successfully prepared in this study. The HADP NPs show promising combined photothermal- and chemotherapeutic effects without inducing undesired side effects on a murine colon cancer animal model.


Assuntos
Materiais Biocompatíveis/química , Doxorrubicina/uso terapêutico , Ouro/química , Hipertermia Induzida , Nanotubos/química , Neoplasias/terapia , Fototerapia , Polímeros/química , Animais , Antineoplásicos/uso terapêutico , Linhagem Celular Tumoral , Modelos Animais de Doenças , Doxorrubicina/química , Liberação Controlada de Fármacos , Endocitose , Humanos , Interações Hidrofóbicas e Hidrofílicas , Camundongos , Nanotubos/ultraestrutura , Tamanho da Partícula , Copolímero de Ácido Poliláctico e Ácido Poliglicólico/química , Albumina Sérica/química , Eletricidade Estática
4.
Sci Rep ; 8(1): 11812, 2018 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-30087401

RESUMO

The small sized, flexible, high-performed and bio-compatible sensing devices are the critical elements to realize the bio-related detection or on-site health monitoring systems. In this work, the flexible localized surface plasmon resonance (LSPR) bio-sensors were demonstrated by integrating the metal-insulator-metal (MIM) nanodisks with bio-compatible polydimethylsiloxane (PDMS) substrate. The different geometries of MIM nanodisk sensors were investigated and optimized to enhance the spatial overlap of the LSPR waves with the environment, which lead to a high sensitivity of 1500 nm/RIU. The omni-directional characteristics of LSPR resonances were beneficial for maintaining the device sensitivity stable under various bending curvatures. Furthermore, the flexible MIM nanodisk LSPR sensor was applied to detect A549 cancer cells in PBS+ solution. The absorption peak of the MIM-disk LSPR sensor obviously redshift to easily distinguish between the phosphate buffered saline (PBS+) solution with A549 cancer cells and without cells. Therefore, the flexible MIM nanodisk LSPR sensor is suitable to develop on-chip microfluidic biosensors for detection of cancer cells on nonplanar surfaces.

5.
ACS Appl Mater Interfaces ; 10(18): 15996-16004, 2018 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-29658267

RESUMO

Controlling circularly polarized (CP) states of light is critical to the development of functional devices for key and emerging applications such as display technology and quantum communication, and the compact circular polarization-tunable photon source is one critical element to realize the applications in the chip-scale integrated system. The atomic layers of transition metal dichalcogenides (TMDCs) exhibit intrinsic CP emissions and are potential chiroptical materials for ultrathin CP photon sources. In this work, we demonstrated CP photon sources of TMDCs with device thicknesses approximately 50 nm. CP photoluminescence from the atomic layers of tungsten diselenide (WSe2) was precisely controlled with chiral metamolecules (MMs), and the optical chirality of WSe2 was enhanced more than 4 times by integrating with the MMs. Both the enhanced and reversed circular dichroisms had been achieved. Through integrations of the novel gain material and plasmonic structure which are both low-dimensional, a compact device capable of efficiently manipulating emissions of CP photon was realized. These ultrathin devices are suitable for important applications such as the optical information technology and chip-scale biosensing.

6.
Opt Lett ; 42(23): 4804-4807, 2017 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-29216115

RESUMO

The Ta2O5-based micro-ring resonator with an unloaded quality factor of 182,000 has been demonstrated to realize efficient nonlinear wavelength generation. The propagation loss of the resonator is 0.5 cm-1, and the buildup factor of the ring resonator is estimated to be ∼50. With a high buildup factor of the ring structure, the four-wave-mixing (FWM) conversion efficiency of -30 dB is achieved in the resonator with a pump power of 6 mW. Based on power-dependent FWM results, the nonlinear refractive index of Ta2O5 is estimated to be 1.4×10-14 cm2/W at a wavelength of ∼1550 nm. The demonstration of an enhanced FWM process in the Ta2O5-based micro-ring cavity implies the possibility of realizing FWM-based optical parametric oscillation in a Ta2O5-based micro-ring resonator.

7.
Sci Rep ; 6: 26578, 2016 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-27220650

RESUMO

Circularly polarized laser sources with small footprints and high efficiencies can possess advanced functionalities in optical communication and biophotonic integrated systems. However, the conventional lasers with additional circular-polarization converters are bulky and hardly compatible with nanophotonic circuits, and most active chiral plasmonic nanostructures nowadays exhibit broadband emission and low circular dichroism. In this work, with spirals of gallium nitride (GaN) nanowires (NWRs) covered by a metal layer, we demonstrated an ultrasmall semiconductor laser capable of emitting circularly-polarized photons. The left- and right-hand spiral metal nanowire cavities with varied periods were designed at ultraviolet wavelengths to achieve the high quality factor circular dichroism metastructures. The dissymmetry factors characterizing the degrees of circular polarizations of the left- and right-hand chiral lasers were 1.4 and -1.6 (±2 if perfectly circular polarized), respectively. The results show that the chiral cavities with only 5 spiral periods can achieve lasing signals with the high degrees of circular polarizations.

8.
Opt Express ; 24(1): 300-7, 2016 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-26832261

RESUMO

We describe a dispersion-enabled, ultra-low power realization of super-resolution in an integrated Mach-Zehnder interferometer. Our scheme is based on a Vernier-like effect in the coincident detection of frequency correlated, non-degenerate photon pairs at the sensor output in the presence of group index dispersion. We design and simulate a realistic integrated refractive index sensor in a silicon nitride on silica platform and characterize its performance in the proposed scheme. We present numerical results showing a sensitivity improvement upward of 40 times over a traditional sensing scheme. The device we design is well within the reach of modern semiconductor fabrication technology. We believe this is the first metrology scheme that uses waveguide group index dispersion as a resource to attain super-resolution.

9.
Nanoscale ; 8(8): 4579-87, 2016 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-26842460

RESUMO

The catalytic solid-phase synthesis of self-organized nanoporous tin sulfide (SnS) with enhanced absorption, manipulative transmittance and depolarization features is demonstrated. Using an ultralow radio-frequency (RF) sputtering power, the variation of the orientation angle between the anodized aluminum oxide (AAO) membrane and the axis of the sputtered ion beam detunes the catalytically synthesized SnS from nanorod to nanoporous morphology, along the sidewall of the AAO membrane. The ultraslow catalytic sputtering synthesis on the AAO at the RF plasma power of 20 W and the orientation angle of 0° regulates the porosity and integrality of nanoporous SnS, with average pore diameter of 80-150 nm. When transferring from planar to nanoporous structure, the phase composition changes from SnS to SnS2-Sn2S3, and the optical bandgap shrinks from 1.43 to 1.16 eV, due to the preferred crystalline orientation, which also contributes to an ultralow reflectance of <1% at 200-500 nm when both the transmittance and the surface scattering remain at their maxima. The absorption coefficient is enhanced by nearly one order of magnitude with its minimum of >5 × 10(4) cm(-1) at the wavelength between 200 and 700 nm, due to the red-shifting of the absorption spectrum to at least 100 nm. The catalytically self-organized nanoporous SnS causes strong haze and beam divergence of 20°-30° by depolarized nonlinear scattering at the surface, which favors the solar energy conversion with reduced surface reflection and enhanced photon scattering under preserved transmittance.

10.
Sci Rep ; 6: 19757, 2016 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-26794268

RESUMO

The epitaxy of high-power gallium nitride (GaN) light-emitting diode (LED) on amorphous silicon carbide (a-SixC(1-x)) buffer is demonstrated. The a-SixC(1-x) buffers with different nonstoichiometric C/Si composition ratios are synthesized on SiO2/Si substrate by using a low-temperature plasma enhanced chemical vapor deposition. The GaN LEDs on different SixC(1-x) buffers exhibit different EL and C-V characteristics because of the extended strain induced interfacial defects. The EL power decays when increasing the Si content of SixC(1-x) buffer. The C-rich SixC(1-x) favors the GaN epitaxy and enables the strain relaxation to suppress the probability of Auger recombination. When the SixC(1-x) buffer changes from Si-rich to C-rich condition, the EL peak wavelengh shifts from 446 nm to 450 nm. Moreover, the uniform distribution contour of EL intensity spreads between the anode and the cathode because the traping density of the interfacial defect gradually reduces. In comparison with the GaN LED grown on Si-rich SixC(1-x) buffer, the device deposited on C-rich SixC(1-x) buffer shows a lower turn-on voltage, a higher output power, an external quantum efficiency, and an efficiency droop of 2.48 V, 106 mW, 42.3%, and 7%, respectively.

11.
Sci Rep ; 5: 16374, 2015 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-26576041

RESUMO

The 2-D transition metal dichalcogenide (TMD) semiconductors, has received great attention due to its excellent optical and electronic properties and potential applications in field-effect transistors, light emitting and sensing devices. Recently surface plasmon enhanced photoluminescence (PL) of the weak 2-D TMD atomic layers was developed to realize the potential optoelectronic devices. However, we noticed that the enhancement would not increase monotonically with increasing of metal plasmonic objects and the emission drop after the certain coverage. This study presents the optimized PL enhancement of a monolayer MoS2 in the presence of gold (Au) nanorods. A localized surface plasmon wave of Au nanorods that generated around the monolayer MoS2 can provide resonance wavelength overlapping with that of the MoS2 gain spectrum. These spatial and spectral overlapping between the localized surface plasmon polariton waves and that from MoS2 emission drastically enhanced the light emission from the MoS2 monolayer. We gave a simple model and physical interpretations to explain the phenomena. The plasmonic Au nanostructures approach provides a valuable avenue to enhancing the emitting efficiency of the 2-D nano-materials and their devices for the future optoelectronic devices and systems.

12.
Sensors (Basel) ; 15(10): 25868-81, 2015 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-26473870

RESUMO

We numerically and experimentally investigated the lateral coupling between photonic crystal (PhC) nanobeam (NB) cavities, pursuing high sensitivity and figure of merit (FOM) label-free biosensor. We numerically carried out 3D finite-difference time-domain (3D-FDTD) and the finite element method (FEM) simulations. We showed that when two PhC NB cavities separated by a small gap are evanescently coupled, the variation in the gap width significantly changes the coupling efficiency between the two coupled NB cavities and the resulting resonant frequencies split. Experimentally, we fabricated laterally-coupled PhC NB cavities using (InGaAsP) layer on the InP substrate. For sensing, we showed that the laterally coupled PhC NB cavities sensor exhibits higher sensitivity than the single PhC NB cavity. The higher sensitivity of laterally coupled PhC NB cavities is due to the strong evanescent coupling between nearby PhC NB cavities, which depends on the gap width and it is attributed to the large confinement of the electromagnetic field in the gap (air or liquid). As a result of the lateral coupling, both even (symmetric) and odd (asymmetric) modes exist. We show that even modes are more sensitive than odd modes. In addition, higher-order modes exhibit higher sensitivity. Hence, we characterized and examined the fabricated PhC NB cavity as a label-free biosensor, and it exhibits high figure of merit due to its high Q-factor. This illustrates a potentially useful method for optical sensing at nanoscale.


Assuntos
Técnicas Biossensoriais/instrumentação , Nanotecnologia/instrumentação , Nanotecnologia/métodos , Óptica e Fotônica/instrumentação , Simulação por Computador , Refratometria
13.
Opt Express ; 23(7): A204-10, 2015 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-25968786

RESUMO

The hybrid white light-emitting didoes (LED) with polyfluoren (PFO) polymer and quantum dot (QD) was investigated using dispensing method at the different correlated color temperature (CCT) for cool and warm color temperature. This result indicates that the hybrid white LED device has the higher luminous efficiency than the convention one, which could be attributed to the increased utilization rate of the UV light. Furthermore, the CIE 1931 coordinate of high quality white hybrid LED with different CCT range from 3000K to 9000K is demonstrated. Consequently, the angular-dependent CCT and the thermal issue of the hybrid white LED device were also analyzed in this study.

14.
Opt Express ; 23(3): A27-33, 2015 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-25836249

RESUMO

This study demonstrates the application of DBR structure into the remote phosphor structure to improve the angular correlated color temperature (CCT) deviation in white light-emitting diodes (WLEDs). In the experiment, the LED device with DBR structure yielded a higher luminous efficiency than a conventional structure. The CCT deviation can be improved from 1758K to 280K in a range of -70 to 70 degree and the luminous flux increases more than 10% due to the enhancement of the light extraction of the blue light. Moreover, the reflectance of the different DBR structures is analyzed with different angles to reveal the reasons of such improvements. As the result, this LED device with DBR structure shows the great potential to use as the next generation lighting source.

15.
Nanoscale ; 6(10): 5378-83, 2014 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-24706049

RESUMO

To enhance the uniformity of correlated color temperature (CCT) and luminous flux, we integrated ZrO2 nanoparticles into white light-emitting diodes. This novel packaging scheme led to a more than 12% increase in luminous flux as compared to that in conventional dispensing structures. This was attributed to the scattering effect of ZrO2 nanoparticles, which enhanced the utilization of blue light. Moreover, the CCT deviation was reduced from 522 to 7 K in a range of -70 to +70°, and essentially eliminated the yellow ring phenomenon. The haze measurement indicated strong scattering across the visible spectrum in the presence of ZrO2 in the silicone layer, and this finding also substantiates our claim. In addition, the chromaticity coordinate shift was steady in the ZrO2 dispensing package structure as the drive current increased, which is crucial for indoor lighting. Combined with its low cost, easy fabrication, and superior optical characteristics, ZrO2 nanoparticles can be an effective performance enhancer for the future generation of white light-emitting devices.

16.
Opt Express ; 22(4): 4516-22, 2014 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-24663772

RESUMO

Micro-patterned PDMS film was fabricated and combined with LED chip on board (COB) package to improve the emission uniformity of LED chip. The micro scale patterned sapphire substrate (PSS) was used as a mold to fabricate micro-cone patterned PDMS (MC-PDMS) film. A strong scattering effect from this MC-PDMS film can be verified by the high haze ratio and the Bi-directional Transmission effect. The angle dependent color temperature measurement system was used to measure the ΔCCT of COB with and without MC-PDMS. The measurement results indicate that the ΔCCT was reduced from 1025K to 428K. This improvement can effectively eliminate the yellow ring effect of LED chip. This technology can be thus considered as a cost-effective way for the next generation of light source packages.

17.
Opt Express ; 22(1): 463-9, 2014 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-24515006

RESUMO

A tapered AlGaN electron blocking layer with step-graded aluminum composition is analyzed in nitride-based blue light-emitting diode (LED) numerically and experimentally. The energy band diagrams, electrostatic fields, carrier concentration, electron current density profiles, and hole transmitting probability are investigated. The simulation results demonstrated that such tapered structure can effectively enhance the hole injection efficiency as well as the electron confinement. Consequently, the LED with a tapered EBL grown by metal-organic chemical vapor deposition exhibits reduced efficiency droop behavior of 29% as compared with 44% for original LED, which reflects the improvement in hole injection and electron overflow in our design.


Assuntos
Compostos de Alumínio/química , Gálio/química , Índio/química , Iluminação/instrumentação , Semicondutores , Transporte de Elétrons , Desenho de Equipamento , Análise de Falha de Equipamento , Teste de Materiais
18.
ACS Nano ; 7(12): 10818-24, 2013 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-24224797

RESUMO

Graphene, which exhibits excellent thermal conductivity, is a potential heat dissipation medium for compact optoelectronic devices. Photonic devices normally produce large- quantity of unwanted heat, and thus, a heat dissipation strategy is urgently needed. In this study, single-layer graphene (SLG) grown by chemical vapor deposition (CVD) is used to cover the surface of a photonic crystal (PhC) cavity, where the heat flux produced by the PhC cavity can be efficiently dissipated along the in-plane direction of the SLG. The thermal properties of the graphene-capped PhC cavity were characterized by experiments and theoretical calculations. The thermal resistance of the SLG-capped PhC cavity obtained from experiments is lower than half of that of a bare PhC cavity. The temperature of a SLG-capped PhC cavity is 45 K lower than that without SLG capping under an optical power of 100 µW. Our simulation results indicate that SLG receives the majority of the heat fluxes from the device, leading to the efficient heat dissipation. Both the experimental and simulation results suggest that the SLG is a promising material to enhance the heat dissipation efficiency for optoelectronic applications.

19.
Opt Express ; 21 Suppl 2: A201-7, 2013 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-23482281

RESUMO

This study experimentally and numerically examines the correlated color temperature (CCT) stability issue for hybrid warm white high-voltage light-emitting diodes (HV-LEDs) by using a current compensation method. This method could efficiently maintain the CCT stability factor at approximately 1.0 and yield greater color uniformity with Δu'v' values ranging from 0.017 to 0.003 in CIE 1976 chromaticity coordinates. The simulation results show that the red chip intensity drop is the primary cause of CCT instability in the hybrid warm white system when the temperature increases. Therefore, Furthermore, results indicate that the relative lumen drop improves from 21% to 15% by using a current compensation method.

20.
Nanotechnology ; 23(26): 265201, 2012 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-22700687

RESUMO

The high luminous efficiency and superior uniformity of angular-dependent correlated color temperature (CCT) white light-emitting diodes have been investigated by ZrO2 nano-particles in a remote phosphor structure. By adding ZrO2 nano-particles with silicone onto the surface of the phosphor layer, the capability of light scattering could be enhanced. In particular, the intensity of blue light at large angles was increased and the CCT deviations could be reduced. Besides, the luminous flux was improved due to the ZrO2 nano-particles with silicone providing a suitable refractive index between air and phosphor layers. This novel structure reduces angular-dependent CCT deviations from 1000 to 420 K in the range of -70° to 70°. Moreover, the enhancement of lumen flux was increased by 2.25% at a driving current 120 mA, compared to a conventional remote phosphor structure without ZrO2 nano-particles. Consequently, the ZrO2 nano-particles in a remote phosphor structure could not only improve the uniformity of lighting but also increase the light output.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA