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Linear and nonlinear optical properties of CdSe/ZnTe core/shell spherical quantum dots embedded in different dielectric matrices
摘要： Based on a two-level system, the linear and third-order nonlinear optical properties are analyzed for CdSe/ZnTe spherical core/shell quantum dots embedded in various dielectric matrices including poly-vinyl alcohol, polyethylene and silicon nitride. Our results reveal that by increasing core/shell radii ratio the eigenenergies as well as the transition energy decreased. The presence of the dielectric mismatch in the quantum dot-matrix system can cause significant enhancement of the linear and third-order nonlinear optical susceptibilities. We believe that our findings offer a new degree of freedom in optoelectronic device applications.
关键词： Core/shell,Dielectric matrices,Nonlinear optic,Third-order nonlinear susceptibility
更新于2025-09-23 15:19:57
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Refractory plasmonics enabling 20% efficient lead-free perovskite solar cells
摘要： Core-shell refractory plasmonic nanoparticles are used as excellent nanoantennas to improve the efficiency of lead-free perovskite solar cells (PSCs). SiO2 is used as the shell coating due to its high refractive index and low extinction coefficient, enabling the control over the sunlight directivity. An optoelectronic model is developed using 3D finite element method (FEM) as implemented in COMSOL Multiphysics to calculate the optical and electrical parameters of plain and ZrN/SiO2-modified PSCs. For a fair comparison, ZrN-decorated PSCs are also simulated. While the decoration with ZrN nanoparticles boosts the power conversion efficiency (PCE) of the PSC from 12.9% to 17%, the use of ZrN/SiO2 core/shell nanoparticles shows an unprecedented enhancement in the PCE to reach 20%. The enhancement in the PCE is discussed in details.
关键词： lead-free perovskite solar cells,refractory plasmonics,ZrN/SiO2 core/shell nanoparticles,power conversion efficiency,optoelectronic modeling
更新于2025-09-23 15:19:57
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Study of nanometer-scale structures and electrostatic properties of InAs quantum dots decorating GaAs/AlAs core/shell nanowires
摘要： The configurations of core/shell nanowires (NWs) and quantum dots (QDs) decorating NWs have found great applications in forming optoelectronic devices thanks to their superior performances, and the combination of the two configurations would expect to bring more benefits. However, the nanometer-scale electrostatic properties of the QD/buffer layer/NW heterostructures are still un-revealed. In this study, the InAs QDs decorating GaAs/AlAs core/shell NWs are systemically studied both experimentally and theoretically. The layered atomic structures, chemical information, and anisotropic strain conditions are characterized by comprehensive transmission electron microscopy (TEM) techniques. Quantitative electron holography analyses show large number of electrons accumulating in the InAs QD especially at the dot apex, and charges of reversed signs and similar densities are observed to distribute at the sequential interfaces, leaving great amount of holes in the NW core. Theoretical calculations including simulated heterostructural band structures, interfacial charge transfer, and chemical bonding analysis are in good accordance with the experimental results, and prove the important role of AlAs buffer layer in adjusting the heterostructural band structure as well as forming stable InAs QDs on the NW surfaces. These results could be significant for achieving related optoelectronic devices with better stability and higher efficiency.
关键词： quantum dot,transmission electron microscopy,atomic structure,core/shell nanowire,electrostatic property
更新于2025-09-23 15:19:57
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Metallic Core-Shell Photonic Crystals for Surface-Enhanced Raman Scattering (SERS)
摘要： Metallic core-shell substrate is specially used to serve ultrasensitive molecular detection down to concentration of micromolar level based on surface-enhanced Raman spectroscopy (SERS). Calculations show that the amorphous poly(methyl methacrylate) (PMMA) photonic crystals incorporated with metal nanoparticles which is either gold or silver nanoparticles can significantly increase the electromagnetic fields at the air dielectric interface, leading to remarkable Raman enhancement. Corresponding experiments and characterizations show the characteristic and performance of core-shell structures which present an excellent sensitivity, reproducibility and stability to act as SERS substrate.
关键词： Silver nanoparticles,Electromagnetic field,Poly(methyl methacrylate),SERS,Gold nanoparticles,Core-shell
更新于2025-09-23 15:19:57
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68Ga CdTe/CdS fluorescent quantum dots for detection of tumors: investigation on the effect of nanoparticle size on stability and in vivo pharmacokinetics
摘要： Background: Quantum dots (QDs)-based theranostics offer exciting new approaches to diagnose and therapy of cancer. To take advantage of the unique properties of these fluorescent QDs for different biomedical applications, their structures, size and/or surface chemistry need to be optimized, allowing their stability and functionalities to be tailored for different biomedical applications. Methodology: Cadmium telluride/Cadmium sulfide QDs (CdTe/CdS QDs) were synthesized and their structure, size, photostability and functionalities as a bioprobe for detection of Fibrosarcoma tumors were studied and compared with Cadmium telluride (CdTe) QDs. Hence, CdTe/CdS QDs were labeled with 68Ga radionuclide for fast in vivo biological nuclear imaging. Using gamma paper chromatography (γ-PC), the physicochemical properties of the prepared labeled QDs were assessed. In vivo biodistribution and positron emission tomography (PET) imaging of the 68Ga@ CdTe/CdS QDs nanocrystals were investigated in Sprague Dawley? rats bearing Fibrosarcoma tumor. Results: CdS shell on the surface of CdTe core increases the size and photostability against high energy radiations; therefore, CdTe/CdS QDs show prolonged fluorescence as compared to CdTe QDs. Conclusion: Excellent accumulation in tumor was observed for core/shell quantum dots, but this study showed that small changes in the size of the QDs (+1 nm), after adding the CdS shell around CdTe core, greatly change their biodistribution (especially the liver uptake).
关键词： core/shell quantum dots,PET,tumor imaging,68Ga,Cadmium telluride/Cadmium sulfide
更新于2025-09-23 15:19:57
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Ultrahigh Breakdown Strength and Energy Density in PLZST@ PBSAZM Antiferroelectric Ceramics Based on Core-shell Structure
摘要： A novel core-shell structured Pb0.91La0.06(Zr0.552Sn0.368Ti0.08)O3@PbO–B2O3-SiO2-Al2O3-ZnO-MnO2 (PLZST@PBSAZM) antiferroelectric particles were successfully fabricated via sol-gel method. As expected, the sintering temperature was notably reduced from 1250 oC to 1100 oC with the increasing glass contents. More importantly, the breakdown strengths of PLZST@PBSAZM ceramics were significantly increased from 252 kV/cm to 402 kV/cm. As a result, the energy density was up to 7.4 J/cm3 with 1 wt.% of coating glass content, a 55.3% enhancement over the pure PLZST (4.7 J/cm3). Furthermore, the simulations of electric field distribution provided a powerful evidence that the enhancement of the breakdown strength was induced by the core-shell structure, since the glass coating layer could not only undertake the most of electric field, but also impede the grain growth to achieve the smaller grains, which led to the reduction of electric field intensity on the grain cores.
关键词： Core-shell structured,Antiferroelectric,Breakdown strength,Energy density
更新于2025-09-23 15:19:57
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<i>In situ</i> growth of α-Fe <sub/>2</sub> O <sub/>3</sub> @Co <sub/>3</sub> O <sub/>4</sub> core–shell wormlike nanoarrays for a highly efficient photoelectrochemical water oxidation reaction
摘要： Photoelectrochemical (PEC) water splitting represents a promising strategy to convert solar energy into chemical energy in the form of hydrogen, but its performance is severely limited by the sluggish water oxidation reaction. Herein, for the first time, we report the direct assembly of an ultrathin, uniform, and dense layer of Co3O4 on wormlike nanostructured hematite (WN-α-Fe2O3) to form a large-area and high-density WN-α-Fe2O3@Co3O4 core–shell nanoarray via in situ hydrothermal growth followed by calcination, in which the electrostatic force between WN-α-Fe2O3 and the reactants, pH- and temperature-controlled structures of WN-α-Fe2O3, and ultralow nucleation rate of Co3O4 precursors all play critical roles. The obtained heteronanostructure array shows a photocurrent density of 3.48 mA cm?2, which is 4.05 times higher than that of pristine WN-α-Fe2O3 (0.86 mA cm?2), an onset potential of ～0.62 V, 60 mV lower than that of α-Fe2O3 (～0.68 V), and a photoconversion efficiency of 0.55%, 3.93 times higher than that of WN-α-Fe2O3 (0.14%). This is among the highest performances reported for Fe2O3-based photoanodes for water splitting. It is discovered that the Co3O4 shells can significantly enhance the charge separation, accelerate the charge transport and transfer, and reduce the charge transfer resistance from the photoelectrode to the electrolyte for a fast water oxidation reaction, thereby greatly promoting the PEC water oxidation performance of pristine WN-α-Fe2O3. This work not only creates a novel low-cost and Earth-abundant WN-α-Fe2O3@Co3O4 photoelectrode with superior PEC water oxidation performance and provides scientific insights into the enhancement mechanism, but also offers a general strategy for the in situ growth of water oxidation catalysts on various photoelectrodes with 3-D complex geometries for PEC water splitting.
关键词： α-Fe2O3,water oxidation reaction,Co3O4,Photoelectrochemical water splitting,core–shell nanoarray
更新于2025-09-23 15:19:57
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Synthesis and Luminescence Properties of Core-Shell-Shell Composites: SiO2@PMDA-Si-Tb@SiO2 and SiO2@PMDA-Si-Tb-phen@SiO2
摘要： Two novel core-shell composites SiO2@PMDA-Si-Tb, SiO2@PMDA-Si-Tb-phen with SiO2 as the core and terbium organic complex as the shell, were successfully synthesized. The terbium ion was coordinated with organic ligand forming terbium organic complex in the shell layer. The bi-functional organosilane ((HOOC)2C6H2(CONH(CH2)3Si(OCH2CH3)3)2 (abbreviated as PMDA-Si) was used as the first ligand and phen as the second ligand. Furthermore, the silica-modified SiO2@PMDA-Si-Tb@SiO2 and SiO2@PMDA-Si-Tb-phen@SiO2 core-shell-shell composites were also synthesized by sol-gel chemical route. An amorphous silica shell was coated around the SiO2@PMDA-Si-Tb and SiO2@PMDA-Si-Tb-phen core-shell composites. The core-shell and core-shell-shell composites both exhibited excellent luminescence in solid state. The luminescence of core-shell-shell composites was stronger than that of core-shell composites. Meanwhile, an improved luminescence stability property for the core-shell-shell composites was found in the aqueous solution. The core-shell-shell composites exhibited bright luminescence, high stability, long lifetime, and good solubility, which may present potential applications in the bio-medical field.
关键词： silica shell,2,5-bis((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid (PMDA-Si),lifetime,photoluminescence,core-shell composite,core-shell-shell composite
更新于2025-09-19 17:15:36
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Bi <sub/>2</sub> SiO <sub/>5</sub> @g-SiO <sub/>2</sub> upconverting nanoparticles: a bismuth-driven core–shell self-assembly mechanism
摘要： Core–shell systems have attracted increasing interest among the research community in recent years due to their unique properties and structural features, and the development of new synthetic strategies is still a challenge. In this work, we have investigated lanthanide-doped Bi2SiO5 nanocrystal formation inside mesoporous silica nanoparticles (MSNs). The role of both synthesis temperature and concentration of the bismuth precursor impregnated into the MSNs is discussed, showing an unprecedented strategy for the simultaneous stabilization of a crystalline core and a glassy shell. Temperature dependent synchrotron radiation X-ray powder diffraction (SR-XRPD) and high resolution transmission electron microscopy (HR-TEM) analyses allow one to follow the crystalline core growth. A mechanism for the formation of a Bi2SiO5@g-SiO2 core–shell nanosystem is proposed. In addition, the easy tunability of the color output of the upconverting system is demonstrated by means of suitable doping lanthanide ions with potential applications in several fields.
关键词： upconversion luminescence,mesoporous silica,core–shell nanoparticles,bismuth silicate,Bi2SiO5
更新于2025-09-19 17:15:36
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Reducing the surface recombination during light-driven water oxidation by core-shell BiVO4@Ni:FeOOH
摘要： The photocurrent of BiVO4 is limited by surface recombination not surface catalysis, which is currently reported as the main restrict factor for high efficiency photo-electrochemical (PEC) water splitting. To solve this problem, an ultrathin Ni:FeOOH (~ 8 nm) modified nanoporous BiVO4 photoanode (BiVO4@Ni:FeOOH) was constructed with core-shell structure for PEC water oxidation. Attributed to the p-n hetero-junction formed between BiVO4 and Ni:FeOOH, the photocurrent density of BiVO4@Ni:FeOOH increased by a factor of 11 (2.86 mA cm-2 at 1.23 V vs. RHE), together with ~ 180 mV negative shift of onset potential under AM 1.5 G irradiation (100 mW cm-2) in comparison to the pristine BiVO4. More importantly, detailed insight into the fate of the photo-generated charge carriers at the surface is investigated. Intensity modulated photocurrent spectroscopy (IMPS) is used to investigate the surface carrier dynamics of BiVO4 and BiVO4@Ni:FeOOH. IMPS results and hole scavenger measurement (HSM) certify the main role of Ni:FeOOH is to improve surface recombination by largely decreasing the surface recombination rate constant (krec), not surface catalysis. This work demonstrates Ni:FeOOH can facilitate local surface kinetics and reduce recombination rates as well and be used in other photoelectrodes especially the photoanodes with surface defects for PEC water splitting.
关键词： Core-shell,intensity modulated photocurrent spectroscopy,p-n heterojunction,surface recombination
更新于2025-09-19 17:15:36