Controllable Shell Thickness Research Articles

Preparation of Al[sbnd]Si microcapsules with high latent heat and durability via control of shell thickness

Microencapsulation of the AlSi alloy is an effective approach to overcome the challenges of corrosion and oxidation during high temperature operational service when used as phase change heat storage material. Research to date has shown that the prepared microcapsules was not able retain the high latent heat of AlSi alloy and achieve excellent thermal cycling performance at the same time. In this work, AlSi alloy microcapsules with adjustable shell thickness were successfully prepared through hydrothermal reaction, in situ polymerization and heat treatment at different oxygen contents. The phase composition and microstructure of the microcapsules were characterized in detail by XRD and electron microscopy. The thermal performances were tested through thermal cycling and thermal analysis. The results demonstrated that the outer protective shell layer of microcapsules was composed of dense α-Al2O3 and the thickness was adjustable from 372 to 1504 nm by controlling the oxygen content during heat treatment. Meanwhile, the regulation mechanism of shell thickness was analyzed. According to thermal analysis, the latent heat of microcapsules could achieve 450 J·g−1, and the latent heat retention was 100 % after 5000 thermal cycles from 500 °C to 650 °C. This work provides new method of adjusting the shell thickness of AlSi microcapsules to achieve an ultra-high thermal performance in terms of latent heat and retention, which promotes the development of applications for metal-based heat storage materials.

Optimum design of uniform and non-uniform infill-coated structures with discrete variables

This article introduces a novel computer-aided procedure to design optimised coated structures with precise shell thickness control using the Smallest Univalue Segment Assimilating Nucleus operator and a novel augmentation-projection technique. Structures with heterogeneous sections, or coated structures, combine two different materials for the nucleus and the shell, which are generally chosen so that the material in the infill is lighter and the material in the coating is stiffer, which in this work are supposed homogeneous. Solving the interface problem requires material properties interpolation equations that consider three material phases, accurate placement of the coating over the base material, and precise control over the coating's thickness. The formation of the coating is controlled by the Smallest Univalue Segment Assimilating Nucleus, an edge detection operator developed in Digital Image Processing. The coating's thickness is controlled by an innovative methodology consisting of the projection of an augmented contour field, which is shown to create a constant thickness coating around the material domain. The optimisation problem is solved with the Sequential Element Rejection and Admission method. The validity of the procedure has been verified by solving various numerical application examples.

Enhancing and broadening the photoresponse of CdS nanowire by constructing core–shell heterostructure

Limited by the severe surface recombination and large bandgap, it is still a challenge to achieve a high-performance broad-spectrum photodetector based on CdS nanowires (NWs). In this work, the CdS/GeS core–shell heterostructure is constructed to enhance and broaden the photoresponse of CdS NWs. The CdS/GeS core–shell heterostructure NWs are prepared by the chemical vapor deposition method, exhibiting smooth surfaces, controlled shell thicknesses, and compositions. From the UV-Vis-near-infrared (NIR) diffuse reflectance spectrum, PL, and time-resolved photoluminescence studies, it is found that the surface recombination is weakened and the light absorption range is widened after the constructing core–shell heterostructure. When configured into photodetectors, the responsivity of the CdS/GeS core–shell heterostructure NWs is up to 76.8 A W−1, which is 10 folds higher than that of pristine CdS NWs. Furthermore, the photoresponse wavelength of the CdS/GeS core–shell heterostructure NWs is extended from 405 to 850 nm. The improved photodetection performance is attributed to the effective separation of photogenerated carriers at the heterostructure interface, weakened surface recombination, and excellent light absorption of the GeS shell. All results imply that constructing core–shell heterostructures is an effective strategy for constructing high-performance photodetectors.

Compensatory shell thickening in corrosive environments varies between related rocky-shore and estuarine gastropods

Few studies have considered the capabilities of gastropods living in minerally-deficient acidified coastal waters to compensate for outer shell corrosion or compromised growing edge shell production. We compared inner shell thickening between pristine shells (control) and corroded shells (experiment) of two related intertidal neritid gastropod species from reduced salinity and acidified environments. We predicted that the rocky-shore, Nerita chamaeleon, which has greater access to shell building biomineralization substrates, should better control shell thickness than the estuarine, Neripteron violaceum. Accordingly, N. chameleon was found to compensate perfectly for variation in the thickness of the outer calcitic blocky layer (BL). Optimal shell thickness (OST) was maintained by selective reabsorption of the aperture ridge of the distal shell (aragonitic crossed-lamellar layer, CL) and by increased internal deposition of proximal (older) shell (aragonitic protocrossed lamellar, PCL). Despite greater exposure to acidification and hyposalinity, N. violaceum showed no significant compensatory shell thickening. These findings reveal that shell thickening capability may vary greatly among intertidal gastropods and that this may be constrained by environmental biomineralization substrate availability. Such environmentally-related responses carry implications for predicted future reductions in coastal water pH and salinity.

Recovery and reuse of magnetic silica-coated iron oxide particles for eco-friendly chemical mechanical planarization

Chemical mechanical planarization (CMP), a crucial process in semiconductor manufacturing, raises environmental concerns due to increased waste generation, prompting questions about its long-term sustainability. To address this issue, we explore an innovative approach to the waste management and recycling process by introducing magnetite (Fe3O4) particles coated with SiO2 layers, aimed at enhancing the CMP recycling efficiency. These core-shell particles exhibit controlled shell thickness, and modified surface charges, as confirmed by various analytical techniques. Our results reveal that slurries containing Fe3O4@SiO2 particles significantly improve W removal rates and surface smoothness compared to conventional slurries, attributed to the optimal mechanical properties. Moreover, the magnetite core facilitates the magnetic separation and recovery of used particles from spent slurries, offering a cost-effective and environmentally friendly solution. The recycling efficacy of these particles is demonstrated through multiple CMP cycles, showing consistent removal rates and surface quality, highlighting the potential of magnetic separation in sustainable CMP.

A tailored dual core-shell magnetic SERS substrate with precise shell-thickness control for trace organophosphorus pesticides residues detection

For addressing the challenges of strong affinity SERS substrate to organophosphorus pesticides (OPs), herein, a rapid water-assisted layer-by-layer heteronuclear growth method was investigated to grow uniform UiO-66 shell with controllable thickness outside the magnetic core and provide abundant defect sites for OPs adsorption. By further assembling the tailored Au@Ag, a highly sensitive SERS substrate Fe3O4-COOH@UiO-66/Au@Ag (FCUAA) was synthesized with a SERS enhancement factor of 2.11 × 107. The substrate's suitability for the actual vegetable samples (cowpeas and peppers) was confirmed under both destructive and non-destructive detection conditions, showing a strong SERS response to fenthion and triazophos, with limits of detection of 1.21 × 10-5 and 2.96 × 10-3 mg/kg in the vegetables under destructive conditions, and 0.13 and 1.39 ng/cm2 for non-destructive detection, respectively. The FCUAA substrate had high SERS performance, effective adsorption capability for OPs, and demonstrated good applicability, thus exhibiting great potential for rapid detection of trace OPs residues in the food industry.

Atomic controlled shell thickness on Pt@Pt3Ti core-shell nanoparticles for efficient and durable oxygen reduction

The exploitation of durable and highly active Pt-based electrocatalysts for the oxygen reduction reaction (ORR) is essential for the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, we designed Pt@Pt3Ti core-shell nanoparticles with atomic-controllable shells through precise thermal diffusing Ti into Pt nanoparticles for effective and durable ORR. Combining theoretical and experiment analysis, we found that the lattice strain of Pt3Ti shells can be tailored by precisely controlling the thickness of Pt3Ti shell in atomic-scale on account of the lattice constant difference between Pt and Pt3Ti to optimize adsorption properties of Pt3Ti for ORR intermediates, thus enhancing its performance. The Pt@Pt3Ti catalyst with one-atomic Pt3Ti shell (Pt@1L-Pt3Ti/TiO2-C) demonstrates excellent performance with mass activity of 592 mA mgPt−1 and durability nearly 19.5-fold that of commercial Pt/C with negligible decay (2 %) after 30,000 potential cycles (0.6–1.0 V vs. RHE). Notably, at higher potential cycles (1.0 V-1.5 V vs. RHE), Pt@1L-Pt3Ti/TiO2-C also showed far superior durability than Pt/C (9.6 % decayed while 54.8 % for commercial Pt/C). This excellent stability is derived from the intrinsic stability of Pt3Ti alloy and the confinement effect of TiO2-C. The catalyst’s enhancement was further confirmed in PEMFC configuration.

Ordered porous copper sulfide with hollow interior for superior electrochemical CO2 to formate conversion

Targeted for superior formate production from electrochemical carbon dioxide (CO2) reduction, hollow ordered porous copper sulfide cuboctahedra (HOP CuS-CO) with controlled shell thicknesses were designed and synthesized in this study. Uniform and interconnected pores are evenly distributed in the hollow shells of HOP CuS-CO. Capitalizing on the merits of porous cages, HOP CuS-CO exhibit outstanding formate production with a Faradaic efficiency up to 70.3 % and catalytic stability of 26 h under an applied potential of −1.1 V versus reversible hydrogen electrode (vs. RHE). In situ Raman spectroscopy results reveal that the adsorption of HCOO* intermediates is promoted on the catalyst surfaces of HOP CuS-CO due to a spatial confinement effect, which leads to highly efficient CO2 to formate conversion. The present study offers insights for designing materials toward superior formate production from electrochemical CO2 reduction.

Controllable preparation of VO2@m-SiO2 and its light transmittance and thermal insulation properties of PVB composite films

In this study, a hybrid approach using the Stöber and solvent extraction techniques was employed to synthesize mesoporous silicon-coated VO2 nanomaterials (VO2@m-SiO2, VmS) with controllable pore sizes and shell thicknesses. This synthesis was aimed at elucidating the influence of mesoporous silicon coatings on the thermochromic effect and optical properties of VO2. Experimental findings reveal that the mesoporous silica architecture markedly improve the phase-transition hysteresis of VO2 while mitigating the Mie effects attributable to particle coarsening, under the appropriate shell thickness. Furthermore, concomitant with the enlargement of the mesoporous aperture, the Tlum and ΔTsol of the VmS/PVB films also exhibit upward trends. Tlum reaches 73.33% and 62.24% in VmS3/PVB and VmS5/PVB, peak ΔTsol reaches 5.16% in VmS5/PVB. The facile synthesis procedure of VmS, in conjunction with its superior performance across phase transition, optics, and thermal insulation metrics, offers a viable pathway for industrial-scale deployment of VO2(M) in smart window applications.

Self‐templated magnesiothermic reduction of ORMOSIL particles to monodisperse hollow spherical SiC composite particles

AbstractHollow silicon carbide (SiC) particles have attracted attention due to their well‐defined morphology, low density, and large surface area that can be leveraged for a wide variety of applications. Here, we report the self‐templated synthesis of monodisperse hollow spherical SiC composite particles with controllable shell thicknesses using magnesiothermic reduction of organically modified silica (ORMOSIL) particles. Monodisperse ORMOSIL particles containing three organic groups of methyl, vinyl, and mercaptopropyl were produced by a simple one‐pot sol–gel process and then converted to hollow spherical SiC composite particles via a magnesiothermic reduction at 700°C under an inert atmosphere. The spherical morphologies of the original ORMOSIL particles were well maintained through this self‐templated conversion process, but the sizes of the hollow SiC particles were slightly reduced by the thermal treatment. Field emission transmission electron microscopy studies revealed that the shell of hollow particles mainly consists of primary β‐SiC particles with nanometer‐scale sizes. The physical and chemical properties of the hollow SiC composite particles were investigated by scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, Brunauer–Emmett–Teller, X‐ray diffraction, Fourier transform infrared spectroscopy, Raman, and solid‐state nuclear magnetic resonance analyses. The shell thickness of hollow spherical SiC composite particles can be controlled by simply changing the duration of the thermal conversion process. This study not only provides a simple and easy approach for the preparation of hollow spherical SiC particles but also opens the possibility of large‐scale manufacturing of such particles for commercial applications.

Lattice-mismatch-free construction of III-V/chalcogenide core-shell heterostructure nanowires

Growing high-quality core-shell heterostructure nanowires is still challenging due to the lattice mismatch issue at the radial interface. Herein, a versatile strategy is exploited for the lattice-mismatch-free construction of III-V/chalcogenide core-shell heterostructure nanowires by simply utilizing the surfactant and amorphous natures of chalcogenide semiconductors. Specifically, a variety of III-V/chalcogenide core-shell heterostructure nanowires are successfully constructed with controlled shell thicknesses, compositions, and smooth surfaces. Due to the conformal properties of obtained heterostructure nanowires, the wavelength-dependent bi-directional photoresponse and visible light-assisted infrared photodetection are realized in the type-I GaSb/GeS core-shell heterostructure nanowires. Also, the enhanced infrared photodetection is found in the type-II InGaAs/GeS core-shell heterostructure nanowires compared with the pristine InGaAs nanowires, in which both responsivity and detectivity are improved by more than 2 orders of magnitude. Evidently, this work paves the way for the lattice-mismatch-free construction of core-shell heterostructure nanowires by chemical vapor deposition for next-generation high-performance nanowire optoelectronics.

Strain and Shell Thickness Engineering in Pd3 Pb@Pt Bifunctional Electrocatalyst for Ethanol Upgrading Coupled with Hydrogen Production.

The ethanol oxidation reaction (EOR) is an attractive alternative to the sluggish oxygen evolution reaction in electrochemical hydrogen evolution cells. However, the development of high-performance bifunctional electrocatalysts for both EOR and hydrogen evolution reaction (HER) is a major challenge. Herein, the synthesis of Pd3 Pb@Pt core-shell nanocubes with controlled shell thickness by Pt-seeded epitaxial growth on intermetallic Pd3 Pb cores is reported. The lattice mismatch between the Pd3 Pb core and the Pt shell leads to the expansion of the Pt lattice. The synergistic effects between the tensile strain and the core-shell structures result in excellent electrocatalytic performance of Pd3 Pb@Pt catalysts for both EOR and HER. In particular, Pd3 Pb@Pt with three Pt atomic layers shows a mass activity of 8.60 A mg-1 Pd+Pt for ethanol upgrading to acetic acid and close to 100% of Faradic efficiency for HER. An EOR/HER electrolysis system is assembled using Pd3 Pb@Pt for both the anode and cathode, and it is shown that low cell voltage of 0.75V is required to reach a current density of 10mA cm-2 . The present work offers a promising strategy for the development of bifunctional catalysts for hybrid electrocatalytic reactions and beyond.

A thermal evaporator for aerosol core-shell nanoparticle synthesis

Segregated bimetallic nanoparticles like core-shell nanoparticles are of interest in various fields including biomedicine, catalysis, and optoelectronics. Aerosol technology is an optimal platform to control nanoparticle size, structure, and composition, which are some of the most important parameters tuning the material performance for the intended applications. Here, we develop a novel evaporator design to coat core particles on-line with a shell directly in the gas phase. The evaporator employs a local heater that decouples heating the evaporating material from the aerosol particles to limit core-shell alloying. We characterize the system by evaporating Zn onto core particles of Au, Sn, and Bi and demonstrate the core-shell particle formation with controllable shell thickness in each material system. We discuss simple models to explain the observed growth process inside the evaporator and the resulting shell formation.

Synthesis of Submicron-Sized Spherical Silica-Coated Iron Nickel Particles with Adjustable Shell Thickness via Swirler Connector-Assisted Spray Pyrolysis.

Silica-coated iron nickel (FeNi@SiO2) particles have attracted significant attention because of their potential applications in electronic devices. In this work, submicron-sized spherical FeNi@SiO2 particles with precisely controllable shell thickness were successfully synthesized for the first time using a swirler connector-assisted spray pyrolysis system, comprising a preheater, specific connector, and main heater. The results indicated that the thickness of the SiO2 shell can be tuned from 3 to 23 nm by adjusting the parameter conditions (i.e., preheater temperature, SiO2 supplied amount). Furthermore, our fabrication method consistently yielded a high coating ratio of more than 94%, indicating an excellent quality of the synthesized particles. Especially, to gain an in-depth understanding of the particle formation process of the FeNi@SiO2 particles, a plausible mechanism was also investigated. These findings highlight the importance of controlling the preheater and SiO2 supplied amount to obtain FeNi@SiO2 particles with desirable morphology and high coating quality.

Au@SnO2 Core@Shell Nanocrystals for Sustainable Environmental Purifications

The search for versatile catalysts for sustainable environmental purifications has been a challenging yet very important research topic especially in the post pandemic era. Core@shell nanocrystals composed of metal core and semiconductor shell have received significant attention as both photocatalysts and chemical catalysts for practical use in organic dyes degradation and bacterial disinfection. This work reports the synthesis of Au@SnO2 core@shell nanocrystals with controllable shell thicknesses. Under light illumination, Au@SnO2 can function as photocatalysts to decompose organic dyes (rhodamine B, RhB) and inactivate E. coli. Because of the band alignment between Au and SnO2, an enhanced photocatalytic activity was achieved on Au@SnO2. Time-resolved photoluminescence spectroscopic analysis was conducted to explore the influence of shell thickness on the interfacial charge dynamics of Au@SnO2 in order to establish the correlation with the resultant photocatalytic performance. On the other hand, the peroxidase mimics features of Au and SnO2 endowed Au@SnO2 with the capability of performing the disinfection of E. coli under darkness conditions. By combining the phtotocatalytic capacity with the peroxidase mimics features, Au@SnO2 demonstrated sustainable activity toward E. coli disinfection under both irradiation and darkness conditions.

Smart gating membrane based on polyzwitterion-modified SiO2 nanoparticles for water treatment and in-situ multi-modal detection

The smart gating membranes with stimuli-response permeation variations have attracted tremendous interest in the field of wastewater treatment. Specifically, successful integration of accurate porous architecture, precise water permeance regulation, long-term duration and in-situ detection of multiple environmental signals in a visualized way is highly desired yet still exclusive. Herein, a smart gating membrane with a combination of accurate porous adjustment and multi-signals detection is developed by assembling poly[2-(1-(4-vinylbenzyl) pyridin-1-ium-4-yl) ethane-1-sulfonate] (PVPES)-grafted SiO2 nanoparticles on cellulose membrane. The membrane exhibits uniform packing architecture with highly tunable water permeance from 0 to 15,330 L m−2 h−1 bar−1, mediated via polymeric shell thickness control and external salt-stimulation; besides, in-situ detection of heavy metal ions and pH values of the treated solution is simultaneously achieved via the pH-induced discoloration and heavy metal ion-dependent fluorescence of PVPES. What’s more, the membrane shows great mechanical stability against repeated bending, vibration or abrasion, as well as great anti-fouling capability, which together contributing to a long service life. We believe the membrane developed here will definitely promote the practical application of smart gating membranes.

Synthesis of Pd@Rh nanocubes with well-defined {100} surface and controlled shell thicknesses for the fabrication of Rh nanocages

We report a facile synthesis of Pd@Rh core–shell nanocubes with ultrathin Rh shell and well-defined, smooth {100} facets for the production of Rh cubic nanocages. Under carefully optimized conditions, the deposition and diffusion rates of Rh adatoms on Pd cubic seeds can be tuned to a suitable level to enable the layer-by-layer growth of Rh overlayers. Specifically, the reaction temperature, type of Rh precursor, injection rate of the precursor solution, in addition to the size of the Pd seeds, all play an important role in establishing the desired growth mode while preventing island growth and homogeneous nucleation. The Rh shell not only endows the nanocrystals with significantly enhanced shape stability against thermally activated transformation under heating up to 500 °C, but also enables the production of Rh nanocages with ultrathin walls and well-preserved {100} facets, which to our knowledge has not been reported in literature.

Influence of shell thickness on the thermal stability and melting-like behavior of Al@Fe core–shell nanoparticles from atomistic simulations: a structural and dynamic description

Core–shell nanoparticles (CSNPs) are a class of functional materials that have received important attention nowadays due to their adjustable properties by a controlled tuning of the core or shell. Understanding the thermal response and structural properties of these CSNPs is relevant to carrying out an analysis regarding their synthesis and application at the nanoscale. The present work is aimed to investigate the shell thickness effect on thermal stability and melting behavior of Al@Fe CSNPs by using molecular dynamics simulations. The results are discussed considering the influence of the Fe shell on the Al nanoparticle and analyzing the effect of different shell thicknesses in Al@Fe CSNPs. In general, calorific curves show a smooth energy decline for temperatures greater than room temperature for different shell thicknesses and sizes, corresponding to the inward and outward atomic movement of Al and Fe atoms, respectively, that produce a mixed Al–Fe nanoalloy. Here, the thermal stability of the Al@Fe nanoparticle is gradually lost passing to a liquid-Al@solid-Fe configuration and reaching a mixed Al–Fe state by an exothermic mechanism. Combining quantities of the atomic diffusion and structural identification, a stepped structural transition of the system is subsequently observed, where the melting-like point was estimated. Furthermore, it is observed that the Al@Fe CSNPs with greater stability are obtained with a thick shell and a large size. The ability to control shell thickness and vary the size opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.

Modulation of Optical Properties by ZnSe Shell Thickness Control in InP/ZnSe/ZnS Quantum Dots Front Cover: (ChemNanoMat 5/2023)

The cover picture illustrates how the optical properties of InP/ZnSe/ZnS quantum dots (QDs) can be modulated by controlling the thickness of the ZnSe intermediate shells. The circles in the top left, center, and bottom right represent QDs with thick, middle, and thin ZnSe shells, respectively. Upon excitation by blue light, they emit different colors and intensities depending on the number of photons entering and exiting the QDs. A model of the QD is presented in the top right, while a photograph of a dispersed solution of QDs emitting light is shown in the bottom left. More information can be found in the Research Article by Akihito Okamoto, Shintaro Toda et al.

A Bone-Penetrating Precise Controllable Drug Release System Enables Localized Treatment of Osteoporotic Fracture Prevention via Modulating Osteoblast-Osteoclast Communication.

Improving local bone mineral density (BMD) at fracture-prone sites of bone is a clinical concern for osteoporotic fracture prevention. In this study, a featured radial extracorporeal shock wave (rESW) responsive nano-drug delivery system (NDDS) is developed for local treatment. Based on a mechanic simulation, a sequence of hollow zoledronic acid (ZOL)-contained nanoparticles (HZNs) with controllable shell thickness that predicts various mechanical responsive properties is constructed by controlling the deposition time of ZOL and Ca2+ on liposome templates. Attributed to the controllable shell thickness, the fragmentation of HZNs and the release of ZOL and Ca2+ can be precisely controlled with the intervention of rESW. Furthermore, the distinct effect of HZNs with different shell thicknesses on bone metabolism after fragmentation is verified. In vitro co-culture experiments demonstrate that although HZN2 does not have the strongest osteoclasts inhibitory effect, the best pro-osteoblasts mineralization results are achieved via maintaining osteoblast-osteoclast (OB-OC) communication. In vivo, the HZN2 group also shows the strongest local BMD enhancement after rESW intervention and significantly improves bone-related parameters and mechanical properties in the ovariectomy (OVX)-induced osteoporosis (OP) rats. These findings suggest that an adjustable and precise rESW-responsive NDDS can effectively improve local BMD in OP therapy.