- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
The mechanochemical synthesis of PbTe nanostructures: following the Ostwald ripening effect during milling
摘要： A fundamental understanding of the Ostwald ripening effect (ORE) during the mechanochemical synthesis of PbTe nanostructures is presented. The ripening process involves the coarsening of larger particles from those of smaller size; this phenomenon was systematically evaluated at different stages of milling by microscopy analyses (AFM, TEM, STEM and HRTEM). At the early stage of milling, smaller particles and quantum dots are eventually dissolved to lower the total energy associated with their surfaces. The ripening process – during milling – involves short-range mass transfer among particles. HRTEM analyses allowed us to identify that coarsening occurs by thermo-mechanically activated cooperative mechanisms. The detachment of the atoms from smaller particles to form bigger ones plays a major role in the particle coarsening. It was found that the coarsening process was not limited to crystalline nanostructures; so grain boundaries, edge dislocations and boundaries among crystalline and amorphous phases also play an important role to determine how species migration contributes to generate coarse particles. Those serve as sites for inducing coarsening in an equivalent way as surfaces do. Secondary ion mass spectrometry and elemental chemical mapping (EDX-STEM) revealed that both the purity and the chemical homogeneity of the PbTe nanostructures are prominent features of this material. Additionally, a direct band gap enhancement (780 nm) compared to bulk PbTe (3859 nm) was detected. It occurred due to the quantum confinement effect, lattice imperfections and even surface properties of the nanostructures. It is important to point out that the whole optical behaviour of the PbTe nanostructures was dependent upon the embedded nanoparticles and quantum dots in the clusters and coarse particles ranging from 15 nm to 35 nm.
关键词： PbTe nanostructures,microscopy analyses,quantum confinement effect,mechanochemical synthesis,Ostwald ripening effect,high-energy milling
更新于2025-09-19 17:15:36
-
Phonon and Polaron properties in InSb spherical quantum dots
摘要： The size-dependent energy gaps, electron and heavy hole effective masses, phonon frequencies and polaron related parameters in InSb spherical quantum dots are investigated. The calculations are performed using a pseudopotential approach. Good agreement is obtained between our results and those of the literature for bulk InSb. When proceeding from bulk to nano-scale, all studied properties are found to be changed significantly. This is attributed to the quantum confinement effect.
关键词： Polarons,Phonons,Quantum dots,InSb,Quantum confinement
更新于2025-09-19 17:13:59
-
Nonradiative Energy Transfer between Thickness-Controlled Halide Perovskite Nanoplatelets
摘要： Despite showing great promise for optoelectronics, the commercialization of halide perovskite nanostructure-based devices is hampered by inefficient electrical excitation and strong exciton binding energies. While transport of excitons in an energy-tailored system via F?rster resonance energy transfer (FRET) could be an efficient alternative, halide ion migration makes the realization of cascaded structures difficult. Here, we show how these could be obtained by exploiting the pronounced quantum confinement effect in two-dimensional CsPbBr3-based nanoplatelets (NPls). In thin films of NPls of two predetermined thicknesses, we observe an enhanced acceptor photoluminescence (PL) emission and a decreased donor PL lifetime. This indicates a FRET-mediated process, benefitted by the structural parameters of the NPls. We determine corresponding transfer rates up to kFRET = 0.99 ns?1 and efficiencies of nearly ηFRET = 70%. We also show FRET to occur between perovskite NPls of other thicknesses. Consequently, this strategy could lead to tailored energy cascade nanostructures for improved optoelectronic devices.
关键词： nanoplatelets,quantum confinement,FRET,halide perovskite,optoelectronics
更新于2025-09-19 17:13:59
-
Ag2ZnSnS4 Nanocrystals Expand the Availability of RoHS Compliant Colloidal Quantum Dots
摘要： The demonstration of the quantum confinement effect in colloidal quantum dots (QDs) has been extensively studied and exploited mainly in Pb and Cd chalcogenide systems. There has been an urgent need recently for the development of non(less)-toxic colloidal QDs to warrant compliance with current safety regulations (Restriction of Hazardous Substances (RoHS) Directive 2002/95/EC). Herein, we report Pb/Cd-free, solution processed luminescent Ag2ZnSnS4 (AZTS) colloidal QDs. We present a selective and controlled amine and thiol-free synthesis of air stable luminescent Ag2ZnSnS4 QDs by hot injection technique. By controlling the reaction conditions we obtain controlled size variation, and demonstrate the quantum confinement effect that is in good agreement with the theoretically calculated values. The bandgap of the AZTS QDs is size-tunable in the near infrared from 740 nm to 850 nm. Finally, we passivate the surface with Zn-oleate, which yields higher quantum yield (QY), longer lifetime and better colloidal stability.
关键词： near infrared,RoHS compliant,Ag2ZnSnS4,colloidal quantum dots,quantum confinement,Zn-oleate passivation
更新于2025-09-19 17:13:59
-
[IEEE 2019 7th International Japan-Africa Conference on Electronics, Communications, and Computations, (JAC-ECC) - Alexandria, Egypt (2019.12.15-2019.12.16)] 2019 7th International Japan-Africa Conference on Electronics, Communications, and Computations, (JAC-ECC) - Circularly Polarized Ridge Gap Waveguide Fed SIW Dielectric Resonator Antenna
摘要： The emerging field of nanophotonics requires plasmonic devices to be fully compatible with semiconductor fabrication techniques. However, very few feasible practical structures exist at present. Here, we propose a CMOS-compatible hybrid plasmonic slot waveguide (HPSW) with enhanced field confinement. Our simulation results show that the HPSW exhibits significantly enhanced field confinement as compared with the traditional low-index slot waveguides and the hybrid metal dielectric slot waveguides. By controlling the thicknesses of different layers, an optimized HPSW structure with a better tradeoff between field confinement and propagation length has been simultaneously achieved.
关键词： field confinement,multi-layer structure,Hybrid plasmonic slot waveguide
更新于2025-09-19 17:13:59
-
[IEEE 2019 International Conference on Power Electronics, Control and Automation (ICPECA) - New Delhi, India (2019.11.16-2019.11.17)] 2019 International Conference on Power Electronics, Control and Automation (ICPECA) - Failure Rate Basics for a Case Study on Grid Connected Photovoltaic Plant
摘要： The emerging field of nanophotonics requires plasmonic devices to be fully compatible with semiconductor fabrication techniques. However, very few feasible practical structures exist at present. Here, we propose a CMOS-compatible hybrid plasmonic slot waveguide (HPSW) with enhanced field confinement. Our simulation results show that the HPSW exhibits significantly enhanced field confinement as compared with the traditional low-index slot waveguides and the hybrid metal dielectric slot waveguides. By controlling the thicknesses of different layers, an optimized HPSW structure with a better tradeoff between field confinement and propagation length has been simultaneously achieved.
关键词： Hybrid plasmonic slot waveguide,multi-layer structure,field confinement
更新于2025-09-19 17:13:59
-
[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - High Responsivity and Low NEP of Room-Temperature Terahertz Antenna-Coupled Microbolometers with Meander Titanium Thermistor
摘要： In this paper, we first formulate the confinement-escape problem of a defender and an evader who attempts escaping from a circular region, which differs from the traditional pursuit-evasion problems. In our setting of the confinement-escape problem, the defender is restricted to move and patrol on the circle, trying to prevent possible escape of the evader who is initially located inside the circle. We describe and characterize some general properties of the problem, and then design two bio-inspired control strategies for the evader and the defender, respectively. In addition, we illustrate some possible motion patterns of the system, investigate the escaping time as a function of the relative-initial-positions of the agents, as well as the winning sets of the two players, respectively, under different system-parameters. To that end, we characterize the contour lines of the winning sets with their gradient properties. Finally, we indicate the abrupt phase transitions between successful confinement and escaping, revealing the strong sensitivity and nonlinearities of the system under critical conditions.
关键词： Confinement-escape problem,phase transition,evader,pursuer-evader,defender,patrolling,pursuit-evasion
更新于2025-09-19 17:13:59
-
Unique Design Strategy for Laser‐Driven Color Converters Enabling Superhigh‐Luminance and High‐Directionality White Light
摘要： Robust ceramic color converters withstanding strong laser irradiations have recently drawn great attention for laser-driven white lighting. However, the local emission within the incident laser spot usually expands to the whole surface area of the ceramics, which definitely makes it hard to achieve white light with high luminance and high directionality. Herein, a new strategy is proposed to solve the problem by elaborately introducing uniform spherical pores (diameter of ≈2 μm) into the phosphor ceramics with controlled contents from 8 to 24.6 vol%. The well-distributed pores, acting as light scattering centers, enable reduction of the luminescent spot size greatly but without any losses in conversion efficiency. By using the high-scattering ceramic color converters with 15% porosity, the light spot diameter is decreased by 46% and the central illuminance is increased by 156%. Moreover, laser-driven white light with an enhanced beam directionality and uniformity is also achieved. A superhigh luminous flux of 7199 lm is realized by using this promising color converter in a rotary mode. The designed high-scattering ceramics with controllable microstructures show great potential for use in extra-high luminance laser-driven lighting and projection.
关键词： light confinement,phosphor ceramics,phosphor wheel,laser-driven lighting,color converters,scattering
更新于2025-09-19 17:13:59
-
One Pot Aqueous Synthesis of L-Histidine Amino Acid Capped Mn: ZnS Quantum Dots for Dopamine Sensing
摘要： Background: Mn doped ZnS is selected as the right element which is prominent among quantum dot for its high luminescent and quantum yield property and also non toxicity while comparing with other organometallic quantum dot synthesized by using different capping agents. Methods: An interesting observation based on colorimetric sensing of dopamine using manganese doped zinc sulfide quantum dot is discussed in this study. Mn doped ZnS quantum dot surface passivated with capping agents such as L-histidine and also in polymers like chitosan, PVA and PVP were studied and compared. The tunable fluorescence effect was also observed in different polymers and amino acid as capping agents. Optical characterization studies like UV-Visible spectroscopy and PL spectroscopy have been carried out. The functional group modification of Quantum dot has been analyzed using FTIR and size and shape analysis was conducted by using HRTEM image. Results: The strong and broad peak of FTIR in the range of 3500-3300 cm-1 confirms the presence of O-H bond. It is also observed that quenching phenomena in the luminescent peak are due to weaker confinement effect. The average size of the particle is shown to be around 4-5 nm. Changes in color of the quantum dot solution from transparent to dark brown has been due to the interaction with dopamine. Conclusion: Finally, L-Histidine amino acid capped Mn:ZnS shows better results in luminescence and size confinement properties. Hence, it was chosen for dopamine sensing due to its colloidal nature and inborn affinity towards dopamine, a neurotransmitter which is essential for early diagnosis of neural diseases.
关键词： dopamine,Quantum dots,confinement,quenching,fluorescence,amino acid,capping agent
更新于2025-09-19 17:13:59
-
Role of nitrogen doped carbon quantum dots on CuO nano-leaves as solar induced photo catalyst
摘要： A p-type transition metal oxide, copper oxide (CuO) was modified with nitrogen doped carbon quantum dots (NCQDs) to fabricate an effective CuO/NCQDs solar driven photo catalyst. The fabrication of single phase monoclinic CuO was confirmed by XRD. SEM images showed the leaf like morphology for CuO which appeared rough and densely packed in CuO/NCQDs composites. TEM images of CuO/NCQDs shows slightly distorted nano-leaves with NCQDs dispersed on them. HRTEM of CuO/NCQDs shows fringes with characteristic planes confirming that the addition of NCQDs has not distorted the crystal structure of CuO. SAED of CuO/NCQDs further confirms the crystalline nature of the as synthesized composite photo catalyst by exhibiting bright diffraction rings. These results further supported the XRD data. EDS spectra of NCQDs and CuO/NCQDs confirm the formation of pure nitrogen doped carbon quantum dots and Cu, N, C and O atoms confirming that NCQDs are well incorporated on CuO Nano leaves. UV-Vis spectra showed a slight increase of band gap energies due to quantum confinement effects. PL spectra exhibited decreased photoluminescence intensity indicating suppression of recombination rate. The developed photocatalyst was applied for the degradation of harmful dye methyl orange. The composite catalyst showed superior degradation efficiency as compared to pure CuO nano-leaves attributed to enhanced visible light absorption and better charge separation ability due to introduction of NCQDs.
关键词： solar light catalyst,nitrogen doped quantum dots,charge separation efficiency,quantum confinement effect,CuO nano-leaves
更新于2025-09-19 17:13:59