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Photoluminescence from GaAs nanostructures
摘要： The confinement properties of semiconductor nanostructures have promising potential in technological application. The main objective of this study is to describe the dependence of Photoluminescence (PL) intensity on different parameters like temperature, excitation wavelength, time and photon energy of GaAs quantum dots (QDs). The model equations are numerically analyzed and simulated with matlab and FORTRAN codes. The experimental fitted values and physical properties of materials are used as data source for our simulation. The result shows that at low temperature the peak is quite sharp, as temperature increases the PL intensity decreases and get quenched at particular thermal energy.
关键词： quantum confinement,Photoluminescence (PL) intensity,GaAs quantum dots,nanostructures,thermal quenching energy
更新于2025-09-04 15:30:14
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Photon Noise Suppression by a Built-in Feedback Loop
摘要： Visionary quantum photonic networks need transform-limited single photons on demand. Resonance fluorescence on a quantum dot provides the access to a solid-state single photon source, where the environment is unfortunately the source of spin and charge noise that leads to fluctuations of the emission frequency and destroys the needed indistinguishability. We demonstrate a built-in stabilization approach for the photon stream, which relies solely on charge carrier dynamics of a two-dimensional hole gas inside a micropillar structure. The hole gas is fed by hole tunneling from field-ionized excitons and influences the energetic position of the excitonic transition by changing the local electric field at the position of the quantum dot. The standard deviation of the photon noise is suppressed by nearly 50% (noise power reduction of 6 dB) and it works in the developed micropillar structure for frequencies up to 1 kHz. This built-in feedback loop represents an easy way for photon noise suppression in large arrays of single photon emitters and promises to reach higher bandwidth by device optimization.
关键词： semiconductor heterostructure,single photon source,two-dimensional hole gas,Quantum dots,quantum optics,resonance fluorescence
更新于2025-09-04 15:30:14
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Faraday Filtering on the Cs-D <sub/>1</sub> -Line for Quantum Hybrid Systems
摘要： Narrow-band ?ltering of light is widely used in optical spectroscopy. Atomic ?lters, which rely on the Faraday effect, allow for GHz-wide transmission spectra, which are intrinsically matched to an atomic transition. We present an experimental realization and a theoretical study of a Faraday ?lter based on cesium and its D1-line-transition (62 S1/2 → 62 P1/2) around 894 nm. We also present the prospects and visions for combining this ?lter with the single photon emission of a single quantum dot, which matches with the atomic transition. The option to lock the spectral position of a quantum dot is discussed at the end of this letter.
关键词： Faraday ?lter,Atomic ?lter,quantum hybrid devices,quantum dots
更新于2025-09-04 15:30:14
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Refractometric Sensing of Heavy Oils in Fluorescent Core Microcapillaries
摘要： Refractometric Sensing of Heavy Oils in Fluorescent Core Microcapillaries — The refractometric sensing of calibrated heavy oils (density > 1 000 kg/m3) is demonstrated using fluorescent-core microcapillaries. A 25-micron capillary channel was first coated with a high-index layer of fluorescent silicon Quantum Dots (QD). This QD film supports the development of cylindrical Whispering Gallery Mode (WGM) resonances inside the capillary. Heavy oils spanning a wide range of refractive index were pumped into the capillary channel, causing large shifts in the fluorescence WGM resonant wavelengths. The sensitivity for heavy oils approached 250 nm per Refractive Index Unit (nm/RIU) at the higher oil indices, which is the highest sensitivity so far observed for a refractometric sensor operating in the fluorescence mode. This suggests that fluorescent core microcapillaries may be a viable microfluidic alternative for refractometric or chemical sensing in various stages of oil and gas processing, monitoring and usage.
关键词： Fluorescent core microcapillaries,Heavy oils,Quantum Dots,Refractometric sensing,Whispering Gallery Mode
更新于2025-09-04 15:30:14
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Photocatalytic Performance on Visible Light Induced ZnS QDs-MgAl Layered Double Hydroxides Hybrids for Methylene Blue Dye Degradation
摘要： Semiconductor hybrids based photocatalytic reaction is one of the prominent methods to treat wastewater, containing the organic pollutants. In the present work, we report the development of ZnS QDs-LDH hybrid structure for the photocatalytic treatment of methylene blue (MB) dye. The as-synthesized ZnS QDs-LDH hybrid structure was characterized by XRD, FESEM, HRTEM, EDX, XPS, and FTIR to analyze the formation, morphology and chemical structure. The UV-Vis DRS was used to investigate the optical absorption characteristics of the ZnS QDs-LDH hybrid. The photocatalytic performance of the as-prepared samples was investigated against the methylene blue dye molecule under UV-Vis light irradiation. The scavenging experiments were carried out in order to probe the radical formation by using EDTA, benzoquinone, and 2-proponal. The cycling experiments were performed to check the stability of the ZnS QDs-LDH hybrid photocatalyst after repeated photodegradation experiments.
关键词： ZnS Quantum dots,Layered double hydroxides,Photocatalytic activity,Methylene blue dye degradation,Water treatment
更新于2025-09-04 15:30:14
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Surface defect and rational design of TiO2?x nanobelts/ g-C3N4 nanosheets/ CdS quantum dots?hierarchical structure for enhanced visible-light-driven photocatalysis
摘要： TiO2-x/g-C3N4/CdS ternary heterojunctions are fabricated through thermal polymerization-chemical bath deposition combined with in-situ solid-state chemical reduction approach. The prepared materials are characterized by X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption, and X-ray photoelectron spectroscopy. The results show that the ternary heterojunctions are formed successfully and CdS quantum dots (QDs) and TiO2 are anchored on surface of g-C3N4 nanosheets simultaneously. The visible-light-driven photocatalytic degradation ratio of Bisphenol A and hydrogen production rate are up to 95% and ~254.8 mmol h-1, respectively, which are several times higher than that of pristine TiO2. The excellent visible-light-driven photocatalytic activity can be ascribed to the synergistic effect of TiO2-x, g-C3N4 and CdS QDs which extend the photoresponse to visible light region and favor the spatial separation of photogenerated charge carriers.
关键词： Photocatalysis,Ti3+ self-doping,g-C3N4 nanosheets,CdS quantum dots,TiO2 nanobelts
更新于2025-09-04 15:30:14
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3D reticulated carbon nitride materials high-uniformly capture 0D black phosphorus as 3D/0D composites for stable and efficient photocatalytic hydrogen evolution
摘要： Black phosphorus has recently emerged as an excellent 2D semiconductor with high charge-carrier mobility and wide tunable bandgap for photocatalysis. In the research, a simple method was developed to manufacture reticulated carbon nitride materials (CN-4N). Utilizing the self-capturing property of CN-4N to catch the black phosphorus quantum dots (BQ) that were uniformly dispersed in aqueous solution, the BQ were successfully implanted into the interior surface of CN-4N, to form a unique structure instead of the normal exterior surface contact pattern. The optimized CN-4N(BQ) showed good stability and achieved an excellent hydrogen production rate of 13.83 mmol h?1 g?1, which was is 3.3 and 35.5 folds larger than that of CN-4N and bulk CN (NCN), respectively. The experimental results illustrated that greatly improved photocatalytic performance of CN-4N(BQ) was attributed to the joint actions of the abundant active sites provided by ultra-porous structures, the excellent vis-NIR absorption capability, the spatially separated reactive sites for the redox reaction, and the greatly enhanced photoinduced electron-hole separation efficiency. This research provides a novel insight for the rational fabrication of CN-based hybrids for various applications.
关键词： Black phosphorus,carbon nitride,photocatalysis,quantum dots,hydrogen evolution
更新于2025-09-04 15:30:14
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Ultra-small amorphous carbon dots: preparation, photoluminescence properties, and their application as TiO2 photosensitizers
摘要： Ultra-small carbon quantum dots (s-CQDs) with excitation wavelength-independent fluorescence had been obtained by hydrothermal-followed acid precipitation method and were characterized by FT-IR, TEM, XPS, UV–Vis and XRD. It was found that as-prepared s-CQDs were amorphous spherical particles with an average diameter of 1.51 nm, and there were abundant hydroxyl and carbonyl groups on their surfaces. Moreover, fluorescence emission study found that the luminescence of s-CQDs was aroused by oxygen group decorated on its surface, and the fluorescence properties of s-CQDs were much different from those of large CQDs (l-CQDs), which showed higher quantum yield and better photoluminescence (PL) property than that of l-CQDs. The PL of s-CQDs possessed two emission centers and was exhibited to be excitation independent. When s-CQDs was used as photosensitizer for TiO2 to photocatalytic degradation of methylene blue under visible light irradiation, it showed significantly improved photocatalytic activities compared with 1-CQDs, and the degradation efficiency of methylene blue reached up to 96.6%. The high degradation efficiency was attributed to the ultra-small particle size, abundant acidic groups, and excellent optical properties of s-CQDs.
关键词： Photocatalytic degradation,Ultra-small carbon quantum dots,TiO2 photosensitizers,Photoluminescence,Hydrothermal-followed acid precipitation method
更新于2025-09-04 15:30:14
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<i>In-Situ</i> Measurement and Control of the Fermi Level in Colloidal Nanocrystal Thin Films during Their Fabrication
摘要： In engineering a high-performance semiconductor device, understanding of the Fermi level position is critical. Here, we demonstrate that open-circuit potential (OCP) measurements can be used to quantify the Fermi level in nanocrystal thin films in-situ during their solution-based fabrication. We use this method to study the influence of (1) a metal contact and (2) nanocrystal surface termination on the Fermi level of the nanocrystal film, and find that oxidization or reduction of the nanocrystals as well as surface terminations with dipoles can be used to tune the Fermi level over large energy ranges. Finally, to emphasize the compatibility of the technique with device fabrication, we show that we can use blends of ligands to design the Fermi level landscape in a nanocrystal film. Our work highlights that OCP measurements can be used to gain insights into existing device operation and direct further optimization of optoelectronic devices.
关键词： Fermi level,nanocrystals,quantum dots,electronic structure,In-situ measurement
更新于2025-09-04 15:30:14
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Blue Luminescent ZnO Nanoclusters Stabilized by Esterifiable Polyamidoamine Dendrimers and their UV-Shielding Applications
摘要： Zinc oxide quantum dots (QDs) were added to the water solutions of esterifiable polyamidoamine (PAMAMs) and the ZnO nanoclusters were prepared. The ZnO nanoclusters are stable in water and show bright blue fluorescence under UV lamp. TEM images showed that the ZnO nanoclusters consisted of numerous ZnO QDs. FTIR spectra of ZnO nanoclusters demonstrated the successful modification of ZnO QDs by the esterifiable polyamidoamine dendrimers. The UV-visible absorption spectra indicated that the ZnO nanoclusters exhibited wider and red-shifted comparing with ZnO QDs. The fluorescent spectra showed that the emission peaks at 404 nm of the ZnO QDs became weaker and a new emission peaks appeared at 330 nm after modifying the ZnO QDs with polyamidoamine dendrimers. The UV-visible transmittance spectra showed that the poly(vinyl alcohol)/ZnO nanoclusters film absorbed nearly 99 % of UV light at wavelengths between 200 and 240 nm while 75 % between 240 and 300 nm.
关键词： Poly(vinyl alcohol),Nanoclusters,ZnO quantum dots,UV-shielding,Polyamidoamine dendrimers
更新于2025-09-04 15:30:14