Influence Of Shell Thickness Research Articles

Influence of Shell Thickness on the Performance of NiO-Based All-Inorganic Quantum Dot Light-Emitting Diodes.

The effect of shell thickness on the performance of all-inorganic quantum dot light-emitting diodes (QLEDs) is explored by employing a series of green quantum dots (QDs) (Zn xCd1- xSe/ZnS core/shell QDs with different ZnS shell thicknesses) as the emitters. ZnO nanoparticles and sol-gel NiO are employed as the electron and hole transport materials, respectively. Time-resolved and steady-state photoluminescence results indicate that positive charging processes might occur for the QDs deposited on NiO, which results in emission quenching of QDs and poor device performance. The thick shell outside the core in QDs not only largely suppresses the QD emission quenching but also effectively preserves the excitons in QDs from dissociation of electron-hole pairs when they are subjected to an electric field. The peak efficiency of 4.2 cd/A and maximum luminance of 4205 cd/m2 are achieved for the device based on QDs with the thickest shells (∼4.2 nm). We anticipate that these results will spur progress toward the design and realization of efficient all-inorganic QLEDs as a platform for the QD-based full-colored displays.

Improved dielectric, tensile and energy storage properties of surface rubberized BaTiO3/polypropylene nanocomposites

The low permittivity of the polypropylene (PP) film has become a barrier for the further development of film capacitors with high energy storage density. An advanced strategy of the high-permittivity filler/polymer nanocomposite turns out to be a promising way of solving this problem. In this work, we coated ethylene propylene diene monomer (EPDM) as the shell on the surfaces of BaTiO3 successfully to fabricate core-shell structural nanoparticles. The addition of surface rubberized BaTiO3 into PP matrix promotes the permittivity to about 5.8, while the dielectric loss is barely changed as compared with PP itself. In addition, the elongation at break is as high as 364%, which is over 4 times higher than that of PP. The influences of shell thickness (3 nm, 5 nm and 7 nm) for the nanoparticles and hot-stretching process for the nanocomposite films were also carefully investigated, both of which greatly affected the properties of nanocomposites. Finally, the optimum breakdown strength as high as 370 MV/m is obtained, leading to a maximum energy density of 3.06 J/cm3, which can be attributed to both high breakdown strength and high permittivity of the core-shell structural BaTiO3/PP nanocomposites.

Facile and controllable construction of vanadium pentoxide@conducting polymer core/shell nanostructures and their thickness-dependent synergistic energy storage properties

Thickness- and morphology-controlled vanadium pentoxide/polyaniline (V2O5/PANI) core/shell hybrid nanofibers are fabricated by electropolymerization of PANI on V2O5 nanofibers for enhanced energy storage. By simply adjusting the electrodeposition time, the thickness of the PANI shells can be controlled from 5nm to 47nm, and the morphology can be changed from coaxial to branched. The influence of shell thickness on the improved Li-ion storage performance of the V2O5/PANI core/shell nanofibers is systematically investigated, and this enhancement of charge capability and cycling stability strongly varies with the shell thickness. Thickness-dependent synergistic electron transport, Li-ion diffusion distances, and shell mechanical strength mechanisms are also proposed. These results provide meaningful references for developing new functional core/shell materials and high-performance energy storage composite materials.

Shell thickness matters! Energy transfer and rectification study of Au/ZnO core/shell nanoparticles

In the present study we report the influence of shell thickness on fluorescence resonance energy transfer between Au/ZnO core-shell nanoparticles and Rhodamine 6G dye by steady-state and time-resolved spectroscopy and rectification behaviours. Au/ZnO core-shell nanoparticles with different shell thickness were synthesized in aqueous solution by chemically depositing zinc oxide on gold nanoparticles surface. A pronounced effect on the photoluminescence (PL) intensity and shortening of the decay time of the dye in presence of Au/ZnO core-shell nanoparticles is observed. The calculated energy transfer efficiencies from dye to Au/ZnO are 62.5%, 79.2%, 53.6% and 46.7% for 1.5nm, 3nm, 5nm and 8nm thickness of shell, respectively. Using FRET process, the calculated distances (r) are 117.8, 113.2Å 129.9Å and 136.7Å for 1.5nm, 3nm, 5nm and 8nm thick Au/ZnO core-shell nanoparticles, respectively. The distances (d) between the donor and acceptor are 71.0, 57.8, 76.2 and 81.6Å for 1.5nm, 3nm, 5nm and 8nm thick core-shell Au/ZnO nanoparticles, respectively, using the efficiency of surface energy transfer (SET). The current-voltage (I-V) curve of hybrid Au/ZnO clearly exhibits a rectifying nature and represents the n-type Schottky diode characteristics with a typical turn-on voltage of between 0.6 and 1.3V. It was found that the rectifying ratio increases from 20 to 90 with decreasing the thickness of the shell from 5nm to 3nm and with shell thickness of 8nm, electrical transport through the core-shell is similar to what is observed with pure ZnO samples nanoparticles. The results indicated that the Au/ZnO core-shell nanoparticles with an average shell thickness of 3nm exhibited the maximum energy transfer efficiencies (79.2%) and rectification (rectifying ratio 90).

Preparation, Characterization and Visible-Light Catalytic Activity of Core-Shell Structure NiFe<sub>2</sub>O<sub>4</sub>@TiO<sub>2</sub> Ferrite Nanoparticles

The core-shell structure NiFe2O4@TiO2 nanoparticles was successfully prepared using a sol-gel method, the influence of shell thickness and calcination temperatures on the composition, microstructure, magnetic properties and visible-light catalytic activity of the nanoparticles was studied by XRD, TEM, Uv–vis, vibrating sample magnetometer, etc. Results showed the main composition of core in NiFe2O4@TiO2 was spinel ferrite, and the shell was anatase TiO2, and theshell thickness increased significantly with the increase of TiO2 content, ranging from 10nm to 50nm. The Ms and Mr of nanoparticles decreased with the increase of TiO2 content, and no obvious reaction between the magnetic core and shell occurred; visible-light degradation percent of NiFe2O4@TiO2 nanoparticles increased along with the increase of TiO2 content, whereas the recovery rate of it decreased. Degradation percent and the recovery percent of NiFe2O4@TiO2-50 still reached 93.7% and 90.5%, even after 10 cycle times, respectively, possessing the excellent long-term stability.

Extended photoresponse of ZnO/CdS core/shell nanorods to solar radiation and related mechanisms

We report the study on the influences of shell thickness and core–shell structure on the optical properties of ZnO/CdS core/shell nanorods (NRs) for an elucidation of the mechanisms responsible for the extended photoresponse of ZnO/CdS core/shell NRs to solar radiation. Well aligned ZnO/CdS core/shell NRs were fabricated on indium tin oxide substrates using hydrothermally grown ZnO NRs as the cores and pulsed laser deposited CdS coatings as the shells. The sample structure was characterized by X-ray diffraction and Raman backscattering spectroscopy, revealing the wurtzite structure of both the ZnO cores and CdS shells, and the improvement in the structure after annealing. The optical properties were studied through optical transmittance, absorbance and photoluminescence measurements, showing the optical properties featured with type-II heterogeneous nanostructures constructed from ZnO and CdS. The results provide a support that the optical properties of the CdS covered ZnO NRs are attributed to the suppressed radiative recombination of photogenerated carriers due to the efficient spatial separation of electrons and holes in the nanosized ZnO–CdS heterostructures.

Plasmonic Effect of a Nanoshell Dimer with Different Gain Materials

Though the plasmonic property for a passive nanoparticle dimer has been studied widely, the performance of a nanoparticle dimer with gain material is still inexplicit to our knowledge. Therefore, in this paper, we focus on the plasmonic effect of a nanoshell dimer, with its core filled with different gain materials, under a polarized plane wave excitation using a three-dimensional finite difference time domain method. It is shown that the gain materials in the core of the nanoshell can compensate the intrinsic absorption of the metal shell, resulting in a local energy enhancement in the junction of the active nanoshell dimer. The physics is supported by the detailed energy distribution of the active nanoshell dimer in each geometry region. It is found that the plasmonic coupling between two active nanoshell particles is more compact than the case of passive ones. The influence of shell thickness on the interaction between two adjacent active nanoshells is also analyzed.

A Non-Destructive Evaluation Strategy for Thick Coating Evaluation on Hemispherical Steel Shells of Different Sizes with a Wide-Range ECT Sensor

Abstract The goal of this paper is to develop an effective and high-precision method for thick coating evaluation in hemispherical steel shells of different sizes using eddy current technology. The key problems of the study include limited capability and low measure precision of eddy current sensor for long liftoff evaluation as well as the influence of shell thickness and curvature on liftoff-evaluation precision for coating in different size shells. To solve these problems, a wide-range sensor was proposed and the influence laws of shell sizes on signals were analyzed using a finite element method-boundary element method (FEM-BEM) hybrid program. Finally, a strategy using cubic spline interpolation method and sample database was adopted for thickness evaluation of coating in different size shells, and its applicability was validated by liftoff evaluation results.

ZnSe∶Cu/CdS核壳量子点的合成及光学性能研究

Water-soluble ZnSe:Cu quantum dots were synthesised in aqueous solution,ZnSe:Cu/CdS core/shell quantum dots(QDs)with different shell thickness were obtained in this paper.The influence of shell thickness on the optical properties of ZnSe:Cu QDs was studied.The samples were characterized by TEM,XRD,PL and UV-Vis.The results showed that ZnSe:Cu/CdS core/shell QDs have a cubic zinc-blende structure and are spherical with good dispersibility.The average grain size increased from 2.7 to 4.0 nm after the shell modification.The redshift of core/shell QDs compared with the core QDs was observed in both the UV-Vis and the PL spectra,which suggested that the size of core/shell QDs increased.The results proved that CdS shell were coated on the surface of ZnSe:Cu QDs and formed the ZnSe:Cu/CdS core/shell structure QDs.The PL intensity of the ZnSe:Cu QDs decreased with higher stability after being coated by CdS shell.

The influence of shell thickness of Au@TiO2 core–shell nanoparticles on the plasmonic enhancement effect in dye-sensitized solar cells

Plasmonic core-shell nanoparticles (PCSNPs) can function as nanoantennas and improve the efficiency of dye-sensitized solar cells (DSSCs). To achieve maximum enhancement, the morphology of PCSNPs needs to be optimized. Here we precisely control the morphology of Au@TiO2 PCSNPs and systematically study its influence on the plasmonic enhancement effect. The enhancement mechanism was found to vary with the thickness of the TiO2 shell. PCSNPs with a thinner shell mainly enhance the current, whereas particles with a thicker shell improve the voltage. While pronounced plasmonic enhancement was found in the near infrared regime, wavelength-independent enhancement in the visible range was observed and attributed to the plasmonic heating effect. Emission lifetime measurement confirms that N719 molecules neighboring nanoparticles with TiO2 shells exhibit a longer lifetime than those in contact with metal cores. Overall, PCSNPs with a 5 nm shell give the highest efficiency enhancement of 23%. Our work provides a new synthesis route for well-controlled Au@TiO2 core-shell nanoparticles and gains insight into the plasmonic enhancement in DSSCs.

Instability of cylindrical shells with single and multiple cracks under axial compression

Linear eigenvalue buckling analysis was carried out for singly and doubly cracked cylindrical thin shells under axial compression using the finite element method. First, the effect of crack size and orientation on the buckling behavior of an axially loaded shell with a single crack was studied. Then, the buckling behavior of a cylinder with two parallel longitudinal cracks was investigated. Two different buckling shapes with cross-sectional deformation profiles that resemble letters M (symmetric) and N (anti-symmetric) were identified as the first buckling modes of the cylinder. The exchange between these local buckling modes due to variation of crack size and spacing was illustrated. The transition between these two buckling shapes can be used to estimate the ‘maximum interaction distance’ of the cylinder cracks—the separation distance beyond which the two cracks do not interact in affecting the buckling load of the cylindrical shell. The influence of shell thickness and crack length on the maximum interaction distance was quantified for cylinders with two co-centered (i.e., parallel offset) or collinear longitudinal cracks. Additional simulations were carried out for cylinders with multiple symmetrically spaced longitudinal cracks to show how the behavior of single and double cracks can give the buckling load and mode shape of cylinders with multiple cracks.

Induced Thermal Stresses in Core Shell Magnetic Particles

In this paper, the induced thermal stresses that appear during the cooling process from the room temperature to a lower temperature for core shell magnetic particles are analyzed. Using a finite element method for solving the Fourier heat transport equation, the thermal stresses in the system were calculated taking into account of the temperature dependence of thermal conductivity, heat capacity and different thermal expansion coefficients of the two materials (iron core + alumina shell) in contact. The thermal stresses depend on the particle's radius and the thickness of the alumina shell, having negative values due to the thermal contraction. It was estimated the influence of shell thickness on thermal stresses and on the speed of reaching the mechanical and thermal equilibrium state.

Optimization and design of pigments for heat-insulating coatings

This paper reports that heat insulating property of infrared reflective coatings is obtained through the use of pigments which diffuse near-infrared thermal radiation. Suitable structure and size distribution of pigments would attain maximum diffuse infrared radiation and reduce the pigment volume concentration required. The optimum structure and size range of pigments for reflective infrared coatings are studied by using Kubelka—Munk theory, Mie model and independent scattering approximation. Taking titania particle as the pigment embedded in an inorganic coating, the computational results show that core-shell particles present excellent scattering ability, more so than solid and hollow spherical particles. The optimum radius range of core-shell particles is around 0.3 ∼ 1.6 μm. Furthermore, the influence of shell thickness on optical parameters of the coating is also obvious and the optimal thickness of shell is 100–300 nm.

Modeling the performance of magnetic nanoparticles in multimodal cancer therapy

Composite magnetic nanoparticles (MNPs) consisting of an MNP core and drug loaded polymer shell can increase the efficacy of cancer therapy by overcoming several limitations of conventional hyperthermia and chemotherapy. Multimodal therapy consisting of simultaneous hyperthermia and chemotherapy can increase therapeutic efficiency compared to individual applications of these modalities. Factors influencing power output in an alternating magnetic field (AMF) for superparamagnetic γ-Fe2O3 and Fe3O4 iron oxide MNP were studied. The optimum MNP properties for in vivo magnetic hyperthermia were identified. For a 375 kHz AMF, 23 nm γ-Fe2O3 MNP and 12 nm Fe3O4 MNP produce maximum heating, heat generation is dependent primarily on Néel relaxation and is insensitive to polymer shell thickness. The heating of tumors by uniformly distributed magnetic clusters of optimized iron oxide MNP was modeled. The MNP mass required to heat tumors to hyperthermia temperatures was calculated, the Fe3O4 MNP concentration in the tumor required for hyperthermia was in the range of 0.12–2.2 g ml−1 for Fe3O4 and 0.06–1.7 g ml−1 for γ-Fe2O3 MNP respectively. In vitro drug release from doxorubicin loaded poly-n-isopropylacrylamide coated MNP was also modeled to understand the influence of shell thickness on thermoresponsive drug release. An increase in shell thickness or decrease in temperature resulted in decreased drug release rates. The MNP mass requirements for hyperthermia closely match the requirements for chemotherapy confirming the feasibility of these particles for combined hyperthermia and drug release applications.

Multi-Color Emission in Quantum-Dot-Quantum-Well Semiconductor Heteronanocrystals

We present calculation results of multi-color spontaneous emission from quantum-dot-quantum-well semiconductor heteronanocrystals. Our theoretical results explain experimental results of onion-like spherical system similar to: CdSe (core), ZnS (shell), CdSe (shell) spherical quantum dots surrounded by ZnS. We demonstrate influence of shell thickness to exciton localization in distinct layers of heteronanocrystals. Multi-color emission of such heterosystem is determined by l = 0, n = 1 state localization in CdSe core and by l = 0, n = 2 state localization in CdSe shell.

Surface enhanced Raman scattering of pyridine adsorbed on Au@Pd core/shell nanoparticles

Surface enhanced Raman scattering (SERS) of pyridine adsorbed on Au@Pd core/shell nanoparticles has been investigated theoretically with quantum chemical method, generalized Mie theory and three-dimensional finite-difference time domain (3D-FDTD) method. We first studied the influence of the coated Pd on the electronic structure of Au nanoparticle, and compared the electronic structure of Au(20) cluster with that of Au(10)Pd(10) (core/shell) cluster. Second, we studied SERS spectroscopy of pyridine on Au@Pd core/shell nanoparticles, which revealed the rate of static chemical enhancement and electromagnetic enhancement in the experimental reports. Third, the influence of the Pd shell thickness to the optical absorption of Au@Pd core/shell nanoparticles was investigated with generalized Mie theory. Fourth, we studied the influence of the shell thickness to the local electric field enhancement with 3D-FDTD method. The theoretical results reveal that the static chemical enhancement and electromagnetic enhancement are in the order of 10 and 10(3), respectively. These theoretical studies promote the deeper understanding of the electronic structure and optical absorption properties of Au@Pd, and the mechanisms for SERS of molecule adsorbed on Au@Pd.

Controlled release of avermectin from porous hollow silica nanoparticles: Influence of shell thickness on loading efficiency, UV-shielding property and release

Preparation and characterization of porous hollow silica nanoparticles (PHSNs), with various shell thicknesses in the range of 5–45 nm and a pore diameter of about 4–5 nm, were investigated. PHSNs were fabricated via a sol-gel route with two different structure-directing templates and their shell thickness could be controlled by adjusting the reactant ratio of Na 2SiO 3·9H 2O/CaCO 3. The produced PHSNs were applied as controlled pesticide release carriers to study the effects of the shell thickness on the loading efficiency for avermectin, the UV-shielding property for the loaded avermectin and the controlled release of the loaded avermectin from the carriers. It was found that the amount of loaded avermectin decreases with the increase of shell thickness, while the UV-shielding property of PHSNs for avermectin is improved as the shell gets thicker. In addition, the shell thickness has a significant impact on avermectin release. Increasing the shell thickness in the range of 5–45 nm leads to a more sustained release by decreasing the release rate of the pesticide from PHSNs, showing that the shell thickness is one of the main controlling factors for the active agent release from such systems.

Maximization of the fundamental frequencies of laminated truncated conical shells with respect to fiber orientations

The fundamental frequencies of laminated truncated conical shells with a given material system are maximized with respect to fiber orientations by using a sequential linear programming method with a simple move-limit strategy. The significant influences of shell thickness, shell length, shell radius ratio and cutout on the maximum fundamental frequencies and the associated optimal fiber orientations are demonstrated.

The Influence of Shell Thickness on Hatchability in Commercial Broiler Breeder Flocks

The hatchability of then and thick shelled eggs was compared for 25 broiler breeder flocks. Shell thickness of the eggs was determined by using salt solutions with specific gravities of 1.075, 1.080 and 1.085 to measure the average egg specific gravity. Eggs that floated in solutions with specific gravities of 1.080 or lower were classified as thin shelled. The average specific gravity for the flocks in this study declined below the industry standard of 1.080 at 42 weeks of age. Greater numbers of embryos in thin shelled eggs died throughout incubation, and hatchability was lower than in thick shelled eggs. Using salt solutions to determine shell thickness had little or no effect on the hatchability of the eggs tested.

Influence of Shell Geometry on Buckling Optimization of Fiber-Composite Laminate Shells

The buckling strength of fiber-composite laminate shells with given loading condition and material system is maximized with respect to fiber orientations by using a sequential linear programming method together with a simple move-limit strategy. Significant influence of shell thickness and shell length on the optimal fiber angles, the critical buckling loads and the critical buckling modes of fiber-composite laminate shells has been shown through this investigation.