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Efficient fluorescence quenching of CdSe quantum dots on epitaxial GaAs nanostructures
摘要： Interaction of CdSe quantum dots (QDs) with epitaxially grown GaAs nanostructures has been studied using photoluminescence (PL) technique. Highly fluorescent CdSe QDs of size 3.9 nm were synthesized by colloidal method and coated over GaAs nanostructures grown on GaAs (111)B substrate by metal organic vapor phase epitaxy (MOVPE) using self-assembled Ga droplets as catalyst. Effect of conditions like catalyst growth time and temperature on the growth of GaAs nanostructures has also been studied. Highly uniform tapered hexagonal nanostructures of height around 500 nm were obtained in nearly 100% yield at 420 °C using Ga droplets grown for 10 s. The fluorescence emission of the CdSe QDs on sample bearing the GaAs nanostructures was measured by steady state and time-resolved photoluminescence (TRPL) techniques and compared with the one obtained on bare substrate. Enhanced quenching of the fluorescence of QDs has been witnessed on the sample in which GaAs nanostructures were present. It has been attributed to more efficient defect-related non-radiative relaxation of excited QDs on the surface of six {110} side facets of the GaAs nanostructures that were not present in the bare substrate. The detailed analysis of the TRPL characteristics of the samples has suggested F?rster-like resonance energy transfer (FRET)-based relaxation of CdSe QDs on GaAs nanostructures through shallow traps with significantly reduced average lifetime and the high quenching efficiency.
关键词： Nanostructures,MOVPE,GaAs,CdSe,Time-resolved photoluminescence,Quantum dots
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Suspended Epoxy Polymer Inverted Tapers for Scalable Fibre-Coupled Single-Photon Devices
摘要： The combination of integrated nanophotonic circuits and single quantum emitters holds great promise for scalable quantum information processing (QIP) and for the realization of photonic quantum networks. Efficient and deterministic sources of highly-pure and indistinguishable single photons have been demonstrated using quantum dots (QDs) in GaAs nanostructures [1], enabling the integration with planar circuitry. However, the efficient out-coupling of light from the chip into optical fibres, required for communication with distant quantum nodes and photon storage, remains a challenging task. Here, we report a spot-size converter for the end-fire coupling between suspended GaAs waveguides with embedded QDs and lensed fibres.
关键词： spot-size converter,single-photon sources,photonic quantum networks,quantum dots,GaAs nanostructures
更新于2025-09-11 14:15:04
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CZTS counter electrode in dye-sensitized solar cell: enhancement in photo conversion efficiency with morphology of TiO2 nanostructured thin films
摘要： In the present investigation, kesterite phase Cu2ZnSnS4 (CZTS) nanoparticle, and one-dimensional (1D) nanorods and three-dimensional (3D) flower-like rutile phase TiO2 thin films were obtained by the conventional hydrothermal method. The (112) plane–oriented single-phase CZTS nanoparticles with chemical composition Cu/(Zn + Sn) = 0.84, 0.90, 1.05 were obtained by changing the copper concentration of the precursor solution. The CZTS thin films were prepared on fluorine-doped tin oxide (FTO) substrate by the doctor blade coating method. The effect of reaction time on growth of the hydrothermal deposited rutile phase TiO2 nanorod thin films were investigated. The detailed structural properties, phase identification, and morphological developments were investigated using X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM) techniques. The dye-sensitized solar cells were fabricated with CZTS counter electrodes (CEs) and hydrothermal deposited nanostructured TiO2 photoanodes. The device formed with three-dimensional TiO2 nanostructured photoanode showed higher efficiency (2.65%) than one-dimensional microstructures (1.74%). The study demonstrates that the nanostructure-based morphologies of TiO2 photoanodes affect the performance of CZTS CEs–based dye-sensitized solar cell.
关键词： TiO2 nanostructures,2.65% efficiency,DSSC counter electrode,CZTS nanoparticles
更新于2025-09-11 14:15:04
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Performance improvement of thin-film silicon solar cells using transversal and longitudinal titanium nitride plasmonic nanogratings
摘要： Taking advantage of plasmonic nanostructures for light trapping in thin-film silicon solar cells has attracted ample attention among researchers. Titanium nitride (TiN) has recently been introduced as a promising material exhibiting plasmonic properties similar to gold while taking advantage of low cost, low loss, and CMOS compatibility. Moreover, utilization of TiN offers a good tunability since the optical properties of TiN depend on many fabrication parameters. In this work, transversal and longitudinal TiN nanograting arrays have been employed to act like perpendicular polarizers trapping the incident light in the active layer of the cell. Using optical and electrical simulations, it has been shown that the design provides a significant enhancement in the performance of thin-film silicon solar cells owing to the excitation of surface plasmon resonances and their resultant light trapping. Thanks to the employment of TiN nanogratings, the device offers a broadband absorption enhancement with a considerable improvement at the near infrared wavelengths in which the absorption of bare silicon layer is weak. The proposed thin-film cell results in short-circuit current and power conversion efficiency of about 26.46 mA/cm2 and 12.27%, respectively proving the proficiency of the design for performance improvement of thin-film photovoltaic systems.
关键词： Titanium nitride (TiN),Light trapping,Thin-film silicon solar cells,Plasmonic nanostructures
更新于2025-09-11 14:15:04
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Bacterial Adhesion on Femtosecond Laser-Modified Polyethylene
摘要： In this study, femtosecond laser-induced sub-micrometer structures are generated to modify polyethylene (PE) surface topographies. These surfaces were subjected to bacterial colonization studies with Escherichia coli and Staphylococcus aureus as test strains. The results reveal that the nanostructures do not influence S. aureus coverage, while the adhesion of E. coli is reduced.
关键词： bacterial adhesion,biofilm formation,polyethylene,laser-induced nanostructures,laser-modified surface
更新于2025-09-11 14:15:04
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Embedded quantum dots in semiconductor nanostructures
摘要： In this work, we report the behavior of the tunneling current in a semiconductor nanostructure of (Ga, Al)As/GaAs which takes into account the behavior of the electrons and the Rashba’s spin orbit interaction in the presence of embedded quantum dots of di?erent geometries (lens, pyramid and ring) in voltage function, magnetic ?eld, and the di?erent values of the interaction spin orbit (π/2, π/4 and 3π/4). The results that were obtained show, that the intensity of the current presents appreciable changes when is changed the con?guration of the quantum dot as the intensities of external ?elds and spin polarization as well. All these internal and external e?ects that are studied in our model, signi?cantly modify the transport of information of the semiconductor nanostructure, our results show that the spin e?ects and the quantum dot con?guration contribute to the quantum memories e?ciency and the spin ?lter devices of actual use on nanoscience and nanotechnology.
关键词： quantum dots,Rashba’s spin orbit interaction,tunneling current,semiconductor nanostructures
更新于2025-09-11 14:15:04
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Controllable “Clicked-to-Assembled” Plasmonic Core–Satellite Nanostructures and Its Surface-Enhanced Fluorescence in Living Cells
摘要： The assembly of noble-metal core?satellite (CS) nanostructures is an appealing means to control their plasmonic properties for applications such as surface-enhanced ?uorescence or Raman scattering. However, till now there is a lack of some rapid or convenient methods to construct stable CS nanostructures. Here, we proposed a “clicked-to-assembly” strategy based on the fast and speci?c “click chemistry” reaction between trans-cyclooctene (TCO) and 1,2,4,5-tetrazine (Tz). The CS nanostructures were constructed within 8 min by simple mixing of TCO- or Tz-modi?ed nanoparticles (TCO-NPs or Tz-NPs) without any catalysts or heating required. Transmission electron microscopy experiments show that the constructed CS nanostructures are uniform, and particularly the number of “satellite” nanoparticles in the core surface is controllable by simply adjusting the feeding ratio of TCO-NPs or Tz-NPs in the reaction. The strong surface plasmon coupling e?ect (SPCE) was observed in these CS nanostructures, which was dependent on the coverage degree, size and composition of the satellite, and core NPs. The nanostructures with tuned surface plasmon resonance (SPR) e?ect were tried for the surface-enhanced ?uorescence in living cells. Such well-de?ned CS nanostructures could potentially serve as e?cient SPR-enhanced ?uorescent probes as diagnostics or biomedical imaging agents in nanomedicine.
关键词： core?satellite nanostructures,surface-enhanced ?uorescence,plasmonic properties,nanomedicine,click chemistry
更新于2025-09-11 14:15:04
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Generation of hot electrons in nanostructures incorporating conventional and unconventional plasmonic materials
摘要： The generation of energetic electrons is an effect occurring in any plasmonic nanostructure. However, the number of electrons with high energies generated optically in a plasmonic nanostructure can be relatively small. This is an intrinsic property of the collective plasmon excitations in a Fermi gas of electrons. But the choices of material and geometry have a great impact on the generation rate, which are therefore crucial to design nanostructure with a large rate of generation of energetic (hot) electrons. Here we test different plasmonic materials from the point of view of the generation of hot electrons (HEs). Our choice of materials includes both strongly-plasmonic materials (Au, Ag, Cu and Al) and crystals with strongly broadened plasmonic resonances (Pt, TiN, ZrN). Regarding the choice of geometry, we consider two types of nanostructures, single nanocrystals deposited over a dielectric substrate and metastructure absorber, observing interesting opto-electronic properties. For single nanocrystals, the rate of HE generation is strongly material-dependent since the HE generation rate strongly depends on several physical parameters such as plasmonic enhancement, plasmonic resonance wavelength, Fermi energy, etc. Interestingly, the plasmonic meta-absorbers exhibit a different behaviour. The strongly-plasmonic metals, such as Au, Ag, Cu or Al, show very similar performances, while the materials with damped plasmon resonances demonstrate diverse and reduced rates of HE generation. The physical reason for these differentiated behaviours lies in the dielectric functions of these materials. In the metastructures, plasmonic resonances are in the infrared and the strongly-plasmonic materials behave as an almost ideal metal, whereas the second group of the materials exhibits strong dissipation. This makes the responses from the metastructures made of crystals with damped plasmons strongly dependent on the choice of material. The physical principles described in our study can be useful for designing metastructures and nanodevices based on HEs, which can be used in photo-chemistry and opto-electronics.
关键词： metastructures,hot electrons,nanostructures,opto-electronics,plasmonic materials
更新于2025-09-11 14:15:04
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Renewable and Sustainable Composites || Methodologies for Achieving 1D ZnO Nanostructures Potential for Solar Cells
摘要： One-dimensional (1D) nanostructures are generally used to describe large aspect ratio rods, wires, belts, and tubes. The 1D ZnO nanostructures have become the focus of research owing to its unique physical and technological significance in fabricating nanoscale devices. When the radial dimension of the 1D ZnO nanostructures decreases to some lengths (e.g., the light wavelength, the mean of the free path of the phonon, Bohr radius, etc.), the effect of the quantum mechanics is definitely crucial. With the large surface-to-volume ratio and the confinement of two dimensions, 1D ZnO nanostructures possess the captivating electronic, magnetic, and optical properties. Furthermore, 1D ZnO nanostructure’s large aspect ratio, an ideal candidate for the energy transport material, can conduct the quantum particles (photons, phonons, electrons) to improve the relevant technique applications. To date, many methods have been developed to synthesize 1D ZnO nanostructures. Therefore, methodologies for achieving 1D ZnO nanostructures are expressed, and the relevant potential application for solar cells are also present to highlight the attractive property of 1D ZnO nanostructures.
关键词： hydrothermal,nanostructures,one dimensional,ZnO,solar cell,chemical vapor transport and condensation (CVTC),vapor-liquid-solid (VLS),electrochemical,metal-organic chemical vapor deposition (MOCVD),chemical vapor deposition (CVD)
更新于2025-09-11 14:15:04
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Electromagnetic Energy Redistribution in Coupled Chiral Particle Chain-Film System
摘要： Metal nanoparticle-film system has been proved that it has the ability of focusing light in the gap between particle and film, which is useful for surface-enhanced Raman scattering and plasmon catalysis. The rapid developed plasmonic chirality can also be realized in such system. Here, we investigated an electromagnetic energy focusing effect and chiral near-field enhancement in a coupled chiral particle chain on gold film. It shows large electric field enhancement in the gap between particle and film, as well as chiral near field. The enhancement properties at resonant peaks for the system excited by left circularly polarized light and right circularly polarized light are obviously different. This difference resulted from the interaction of circularly polarized light and the chiral particle-film system is analyzed with plasmon hybridization. The enhanced optical activity can provide promising applications for the enhancement of chiral molecule sensor for this chiral particle chain-film system.
关键词： Chiral near-field enhancement,Chiral plasmonic nanostructures,Chiral focusing,Electromagnetic energy focusing
更新于2025-09-11 14:15:04