Core-shell Nanostructures Research Articles

Morphology engineering of novel MnMoO4@NiMoO4 core–shell nanostructure as an electrode material for asymmetric supercapacitor device

The pursuit of innovative and adaptable electrode materials with exceptional electrochemical performance is crucial for the improvement of sophisticated energy storage devices. Herein, we report a novel design of unique manganese molybdate@nickel molybdate (MnMoO4@NiMoO4) nanorods-on-nanosheets core–shell structures grown on nickel foam as a binder-free electrode using a two-step solvothermal approach for asymmetric supercapacitor. Initially, the samples were scrutinized by spectroscopic (XRD and XPS) and microscopic (FE-SEM, HR-TEM) analysis. The distinct core–shell design offers an efficient mesoporous network, ion diffusion channels a rapid electron transfer pathway, and accommodates more active sites for MnMoO4 and NiMoO4. The optimized MNM-160 presents a superior specific capacitance (Cs) of 1160.52 F/g at 0.5 A/g with an outstanding lifespan in a three-electrode cell. The assembled asymmetric supercapacitors (ASC) device exhibits an understanding of energy density (29.27 Wh kg−1) and power density (961.26 W kg−1). In addition, notable cycling stability with ∼89.85 % retaining over 10,000 charge/discharge cycles in ASCs. Finally, the practical ability is verified by three serial-connected ASC devices to drive the light-emitting diodes (LEDs). Hence, the present study clearly illustrates the efficient electrochemical performance, it can be considered a favorable material for future energy storage devices.

Controlled construction of 2D hierarchical core-shell ZnO/MnO2 nanosheets on Nitinol fiber with enhanced adsorption performance for selective solid-phase microextraction of trace polycyclic aromatic hydrocarbons in water samples

BackgroundPolycyclic aromatic hydrocarbons (PAHs) are an important class of potentially toxic persistent organic pollutants in environmental water. Their concentrations are usually too low to allow for direct determination with analytical instruments, and the preconcentration is required prior to instrumental analysis. Solid phase microextraction (SPME) is considered as a high-performance green sample preparation technique for volatile and non-volatile organic compounds due to its high enrichment factor. In fact, the nature of SPME coatings governs the adsorption performance. Therefore, more efforts have devoted to the controlled construction of novel long-life SPME fibers with enhanced adsorption performance and improved adsorption selectivity. Results2D hierarchical core-shell ZnO/MnO2 nanosheets (NSs) were constructed on a Nitinol (NiTi) fiber substrate by layer-by-layer assembly for enhanced and selective SPME of PAHs. Firstly, hexagonal ZnO NSs were electrodeposited on the NiTi substrate. Subsequently smaller secondary MnO2 NSs were uniformly grown on the surface of ZnO NSs by a facile hydrothermal oxidation process. ZnO NSs were well protected by the chemically stable MnO2 shell, making the coating highly durable and efficient for SPME application. Meanwhile, the ZnO/MnO2 NSs coating demonstrated superior adsorption performance for PAHs. After the optimization of SPME conditions, the proposed SPME-HPLC-UV method exhibited good analytical performance for preconcentrating and determining trace PAHs with wide linear ranges (0.03–200 μg L−1) and low LODs (0.005–0.112 μg L−1) as well as good repeatability (1.4%-6.9%) and fiber-to-fiber reproducibility (5.3%-7.1%). Moreover, the proposed method showed good precision and recovery in the preconcentration and determination of target PAHs in real water samples. SignificanceAs compared with representative commercially available fibers, the NiTi@ZnO/MnO2 NSs fiber showed enhanced adsorption efficiency and improved adsorption selectivity for PAHs. The constructed fiber can be used as an alternative to commercial fibers for the adsorption and preconcentration of target PAHs in the environmental water samples. Moreover, the preparation strategy is expected to provide new insights into the precisely controlled construction of the efficient and stable core-shell bimetallic oxide nanostructures on the superielastic NiTi-based fibers.

Production and immobilization of pectinases from Penicillium crustosum in magnetic core-shell nanostructures for juice clarification

Global market of food enzymes is held by pectinases, mostly sourced from filamentous fungi via submerged fermentation. Given the one-time use nature of enzymes to clarify juices and wines, there is a crucial need to explore alternatives for enzyme immobilization, enabling their reuse in food applications. In this research, an isolated fungal strain (Penicillium crustosum OR889307) was evaluated as a new potential pectinase producer in submerged fermentation. Additionally, the enzyme was immobilized in magnetic core-shell nanostructures for juice clarification. Findings revealed that Penicillium crustosum exhibited enzymatic activities higher than other Penicillium species, and pectinase production was enhanced with lemon peel as a cosubstrate in submerged fermentation. The enzyme production (548.93 U/mL) was optimized by response surface methodology, determining the optimal conditions at 35 °C and pH 6.0. Subsequently, the enzyme was covalently immobilized on synthesized magnetic core-shell nanoparticles. The immobilized enzyme exhibited superior stability at higher temperatures (50 °C) and acidic conditions (pH 4.5). Finally, the immobilized pectinases decreased 30 % the orange juice turbidity and maintained 84 % of the enzymatic activity after five consecutive cycles. In conclusion, Penicillium crustosum is a proven pectinase producer and these enzymes immobilized on functionalized nanoparticles improve the stability and reusability of pectinase for juice clarification.

Chronic toxicity of core–shell SiC/TiO2 (nano)-particles to Daphnia magna under environmentally relevant food rations in the presence of humic acid

To date, research on the toxicity and potential environmental impacts of nanomaterials has predominantly focused on relatively simple and single-component materials, whilst more complex nanomaterials are currently entering commercial stages. The current study aimed to assess the long-term and size-dependent (60 and 500 nm) toxicity of a novel core–shell nanostructure consisting of a SiC core and TiO2 shell (SiC/TiO2, 5, 25, and 50 mg L−1) to the common model organism Daphnia magna. These novel core–shell nanostructures can be categorized as advanced materials. Experiments were conducted under environmentally realistic feeding rations and in the presence of a range of concentrations of humic acid (0.5, 2, 5, and 10 mg L−1 TOC). The findings show that although effect concentrations of SiC/TiO2 were several orders of magnitude lower than the current reported environmental concentrations of more abundantly used nanomaterials, humic acid can exacerbate the toxicity of SiC/TiO2 by reducing aggregation and sedimentation rates. The EC50 values (mean ± standard error) based on nominal SiC/TiO2 concentrations for the 60 nm particles were 28.0 ± 11.5 mg L−1 (TOC 0.5 mg L−1), 21.1 ± 3.7 mg L−1 (TOC 2 mg L−1), 18.3 ± 5.4 mg L−1 (TOC 5 mg L−1), and 17.8 ± 2.4 mg L−1 (TOC 10 mg L−1). For the 500 nm particles, the EC50 values were 34.9 ± 16.5 mg L−1 (TOC 0.5 mg L−1), 24.8 ± 5.6 mg L−1 (TOC 2 mg L−1), 28.0 ± 10.0 mg L−1 (TOC 5 mg L−1), and 23.2 ± 4.1 mg L−1 (TOC 10 mg L−1). We argue that fate-driven phenomena are often neglected in effect assessments, whilst environmental factors such as the presence of humic acid may significantly influence the toxicity of nanomaterials.

Ni foam-supported Cu0.33Co0.67Se2 and modified NiCo-layered double hydroxide nanoarray composites for high-energy-density hybrid supercapacitors

High-performance supercapacitors, valued for their extended operational lifespan and remarkable power density, have garnered significant attention as potential energy storage solutions. Nevertheless, their practical application has been impeded by the limited energy density and unsatisfied rate capability of conventional electrode materials. To address these challenges, we developed an effective approach for crafting a composite material, featuring a core-shell nanostructure comprised of dodecyl sulfate (DS) ions intercalated Cu0.33Co0.67Se2/NiCo-DS-LDH nanostructures. The synergistic inter-component effect between copious active sites of Cu–Co–Se and DS-modified NiCo-LDH readily boosts the high specific capacity as ∼488 mAh g−1 at 1 A g−1 with an enhanced capacity retention of ∼36.3%. In this material system, the Cu0.33Co0.67Se2/NiCo-DS-LDH cathode-integrated hybrid supercapacitor device, with the N, S co-doped porous carbon anode achieves an energy density of ∼54.4 Wh kg−1 at a power density of ∼801 W kg−1. These exceptional electrochemical performances can be attributed to the combinatorial effect of the high conductivity of the Ni network, the high activity of the bimetallic selenide, and the expanded interlayer spacing of the NiCo-LDH. The current work presents a newly developed strategy for the design of promising transition metal-based composites with a rational architecture, offering significant potential for next-generation energy storage systems.

Heterostructure of Fe-Doped CoMoOx/CoMoOx as an Efficient Electrocatalyst for Oxygen Evolution Reaction.

Oxygen evolution reaction (OER) plays a crucial role as a counter half-reaction for both electrochemical hydrogen production through water splitting and the generation of valuable carbon compounds via CO2 reduction. To overcome the sluggish kinetics of the OER, significant efforts have been devoted to developing cost-effective, sustainable, and efficient electrocatalysts, with transition-metal-based catalysts emerging as promising candidates. Herein, we successfully synthesized a core-shell type nanostructure of Fe-doped CoMoOx/CoMoOx (CMFO), which exhibits excellent electrocatalytic properties for OER. The presence of an amorphous layer of Fe-doped CoMoOx with abundant oxygen vacancies, along with the stability of a key OER intermediate, *O, contributes to the enhanced activity of CMFO catalyst compared to pristine CoMoOx (CMO). The optimized catalyst of CMFO-550 achieved much lower overpotential and Tafel slope and also exhibited better remarkable long-term stability for over 90 h compared to CMO-550. These findings highlight the potential of CMFO-550 as a cost-effective and highly efficient electrocatalyst for the OER. The successful development of this core-shell nanostructure opens up a new opportunity for the design and synthesis of advanced electrocatalysts for the OER, with implications for various applications in energy conversion and storage.

Unraveling the Highly Plastic Behavior of ALD‐Aluminum Oxide Encapsulations by Small‐Scale Tensile Testing

We present a study directly measuring the electron‐beam‐induced plasticity of amorphous Al2O3 coatings. Core–shell nanostructures are employed as small‐scale model systems for two‐dimensional coatings made by atomic layer deposition (ALD). Copper nanowires (NWs) are used as substrates for ALD deposition, representing a model system for interconnects commonly found in integrated circuits. Experiments are performed in situ in a transmission electron microscope (TEM) and further analyzed with electron energy loss spectroscopy (EELS). Our in situ TEM tensile experiments reveal the highly plastic behavior of the ALD shell, which withstands a maximum strain of 188%. Comparable samples under beam‐off conditions show a brittle fracture, which underlines the effect of electron irradiation. The electron‐beam‐activated bond switching within the amorphous network enables compensation of the applied tensile strain, leading to viscous flow. By incorporating an intermediate nanocrystalline layer within the Al2O3 shell, the plasticity is suppressed and brittle fracture occurs. This work directly demonstrates the tuning of mechanical properties in amorphous ALD structures through electron irradiation.

Recent Approaches for Cleaving the C─C Bond During Ethanol Electro-Oxidation Reaction.

Direct ethanol fuel cells (DEFCs) play an indispensable role in the cyclic utilization of carbon resources due to its high volumetric energy density, high efficiency, and environmental benign character. However, owing to the chemically stable carbon-carbon (C─C) bond of ethanol, its incomplete electrooxidation at the anode severely inhibits the energy and power density output of DEFCs. The efficiency of C─C bond cleaving on the state-of-the-art Pt or Pd catalysts is reported as low as 7.5%. Recently, tremendous efforts are devoted to this field, and some effective strategies are put forward to facilitate the cleavage of the C─C bond. It is the right time to summarize the major breakthroughs in ethanol electrooxidation reaction. In this review, some optimization strategies including constructing core-shell nanostructure with alloying effect, doping other metal atoms in Pt and Pd catalysts, engineering composite catalyst with interface synergism, introducing cascade catalytic sites, and so on, are systematically summarized. In addition, the catalytic mechanism as well as the correlations between the catalyst structure and catalytic efficiency are further discussed. Finally, the prevailing limitations and feasible improvement directions for ethanol electrooxidation are proposed.

High-efficiency decontamination of pharmaceutical wastewater: Synergistic effects from NaGdF4:Tm,Yb@Mn-MOFs composite photocatalysts

Water pollution caused by antibiotics poses a serious threat to human health and ecosystems. Rapid and efficient removal of antibiotic pollution in water by photocatalysts is one of the effective means to protect the environment and public health. Herein, a wide-spectral responsive upconversion NaGdF4:Yb,Tm@Mn-MOFs core-shell nanostructures were built by coating hexagonal NaGdF4:Yb,Tm cores with amino-functionalized manganese carboxylate MOFs (Mn-MOFs) shells, which exhibited good water dispersibility. Mn-MOFs catalysts is mainly concentrated in the ultraviolet region, while NaGdF4:Yb,Tm nanoparticles can transform infrared light into visible light or even higher energy ultraviolet light, which is harvested by the Mn-MOFs. The optimized nanostructures were tested under simulated solar light (After 120 min irradiation) in the degradation of tetracycline, oxytetracycline hydrochloride and tetracycline hydrochloride, while their degradation rates reached 70%, 72% and 75%, respectively. The better photocatalytic mechanism for antibiotics than its individual components was elucidated, which provides a potential strategy to broaden the full spectrum absorption of the wide bandgap semiconductors and apply for the field of environmental remediation.

Enhanced electrochemical behavior of C@CdS Core-Shell heterostructures

The current work presents hydrothermally synthesized carbon@cadmium sulfide core–shell nanostructures with varying carbon nanosphere concentrations. The series is prepared to investigate the shell thickness depending on the concentration of precursors and consequently impacting the optical and electrochemical properties of the core–shell structures. XRD analysis reveals enhanced crystallinity with reduced carbon. SEM & TEM confirm uniform spherical core–shell structures, with optimal uniformity at lower carbon levels. UV–vis spectroscopy demonstrates visible range absorption and reduced band gap with decreased carbon. Electrochemical analysis exhibits diffusion-controlled behavior and Warburg impedance, making the low-carbon sample most suitable for solar cells. Core-shell structures outperform pure carbon samples in absorbance and impedance spectroscopy, showcasing potential for solar cell applications.

Surface plasmon resonance effects of Ag@ZnO core–shell nanostructure in UV and visible light for photodiode applications

AbstractHerein, Ag@ZnO core–shell nanostructures were prepared via the wet chemical method and were then dissolved in methanol and drop cast onto a p–Si wafer. Experimental current–voltage measurements of the Ag@ZnO/p–Si heterojunction device were investigated under both visible and UV illumination of 365 and 395 nm. The photocurrent, responsivity, detectivity, and on/off ratio were found to be dependent on the light intensity of visible light and wavelength of UV light. The low photocurrent at low light intensities and its rapid increase at high light intensities was attributed to the recombination of electrons and holes and also to the presence of traps at low light intensities. The responsivity and detectivity of the photodiode reach 1.32 A/W and 5.47 × 1011 Jones, respectively at 365 nm. On the contrary, the high performance under UV light was explained by the surface plasmon resonance between Ag and ZnO.

Synthesis of core-shell NiO/BFO nanocomposites for microwave absorbing applications

Magnetic core-shell nanostructures are often employed in high-performance microwave-absorbing applications due to their strong concurrent magnetic-dielectric losses. However, microwave absorbers designed using a single core-shell nanostructure may not attain the desired bandwidth of absorption. Herein, we introduce core-shell nanocomposites of (100-x)NiO/(x)BiFeO3 (x = 0, 25, 50, 75, & 100), prepared by a facile two-step sol-gel wet-chemical method for high-efficiency absorbing applications. Measurements of microwave absorption performance show that the core-shell 50NiO/50BiFeO3 (x = 50) nanocomposite exhibits a remarkable reflection loss of up to −27.3 dB at a matching thickness of 1.9 mm, and the corresponding −10 dB reflection loss bandwidth extends to 6.8 GHz (in X- and Ku-bands). The study suggests that the fabricated core-shell nanocomposite has the potential to be a promising candidate for lightweight microwave absorbing applications. This is evidenced by its showcased improved efficiency, attributed to the synergistic effects of magnetic-dielectric losses, multiple internal reflections, superior impedance matching, and enhanced interfacial polarization at NiO/BiFeO3 interfaces.

Enhanced charge transport and broadband photoresponse of MoS2 photodetectors with sparsely distributed Ag@SiO2 core–shell nanostructures

Integrating metal nanostructures with two-dimensional (2D) material photodetectors has been demonstrated that can greatly improve device performance owning to various extraordinary optoelectronic phenomena. For example, metal nanostructures are served as ideal plasmonic materials to maximize local electromagnetic fields leading to light absorption of 2D materials. In this work, other than the widely reported plasmonic effects, we discover the contribution of metal nanostructures in charge transport engineering in 2D material photodetectors, which is important but always ignored in previous studies by others. Notable improvements of carrier mobility and carrier concentration attributing to the integration of sparsely distributed Ag@SiO2 core–shell nanoparticles on the MoS2 detector were experimentally established, originating from reduced carrier scattering and interfacial gating. Consequently, a 1.5-fold broadband (400–1100 nm) uniform photocurrent enhancement was observed, which was entirely derived from the improved charge transport. These findings open up a new research perspective for the precise identification and objective evaluation of different effects of metal nanostructures on optoelectronic devices.

Novel Nanostructured Pd/Co-Alumina Materials for the Catalytic Oxidation of Atmospheric Pollutants.

Cobalt-doped alumina catalysts were prepared using different methods, either conventional wet impregnation (WI) and/or advanced spray impregnation (SI), and they were evaluated as novel oxidation catalysts for CO and MeOH oxidation. The spray impregnation technique was used with the aim of achieving the synthesis of core-shell catalytic nanostructures to secure the chemical/thermal stability of active sites on the catalyst carrier. The catalysts were further promoted with a low Pd content (0.5 wt.%) incorporated via either incipient wetness impregnation (DI) or spray impregnation. The results revealed the superior performance of the spray-impregnated catalysts (Co/γ-Al2O3-SI) for both reactions. The deposition of Co oxide on the outer surface of the alumina particle (SEM images) and the availability of the active Co phase resulted in the enhancement of the Co/γ-Al2O3 catalysts' oxidation activity. Pd incorporation increased the catalysts' reducibility (TPR-H2) and improved the catalysts' performance for both reactions. However, the Pd incorporation method affected the catalytic performance; with the SI method, the active phase of Co3O4 was probably covered with PdO and was not available for the oxidation reactions. On the contrary, the incorporation of Pd with the DI method resulted in a better dispersion of PdO all over the Co/Al catalyst surface, maintaining available Co active sites and a better Pd-Co interaction. MeOH desorption studies revealed the methanol oxidation mechanism: the Co/Al catalysts promoted the partial oxidation of MeOH to formaldehyde (HCHO) and dehydration to dimethyl ether (DME), while the Pd-based Co/Al catalysts enhanced the complete oxidation of methanol to CO2 and H2O.

New design and optimization of half-tandem quantum dot solar cell: Over 30% power conversion efficiency using nanostructure oriented core-shell

We achieve 30.64% power conversion efficiency (PCE) by comprehensive design and optimization of half-tandem quantum dot (QD) solar cell using nanostructure-oriented core-shell to improve open circuit voltage (Voc) in QD solar cell (QDSC) for first time. In this study, we have used coupling of optical and electrical equations to calculate solar cell parameters. The aim of this study was to optimize the reference structure including PbS quantum dots (PbS-QDs) treated with tetrabutylammonium iodide (PbS-TBAI), Magnesium Zinc Oxide (MgZnO) and PbS ethanedithiol (PbS-EDT) for active layer (AL), electron transport layer (ETL) and hole transport layer (HTL) respectively. At first, the structure was enhanced into half-tandem solar cell by adding Molybdenum Ditelluride (MoTe2) as the second absorber layer to cover the infrared region. Furthermore, the structure was optimized in four steps: (i) adding a Spiro-OMeTAD layer to reduce the series resistance (Rs) and prevent electrons from entering aluminum metal contact, (ii) adding a core-shell (CFTS – SnS) nanostructure, (iii) optimizing ETL, and (iv) investigating the effect of core-shell nanostructure angle. As a final result, the values of short circuit current (Jsc), Voc, PCE, fill factor (FF) and series resistance were obtained 25.25 mA/cm2, 1.49 V, 30.64 %, 0.78 and 2.8 Ω/cm2, respectively.

Fabrication and characterization of a novel strontium oxide-polythiophene core–shell nanocomposite for in-vitro electrochemical detection of antiplatelet cilostazol drug in formulation and human plasma

The green synthesis of metal or metal oxide nanoparticles utilizing plants is a novel promising approach in bio-nanotechnology. The strontium oxide nanoparticles (SrO NPs) were synthesized for the first time utilizing a plant extract of Green cardamom (Elettaria cardamomum) as a reducing and stabilizing agent. The strontium oxide polythiophene (SrO@PTh) nanocomposite was then prepared by in-situ oxidative polymerization of thiophene on the surface of SrO NPs using anhydrous FeCl3 as an oxidant. FTIR spectrum indicates the coordination of SrO NPs with the binding sites along PTh backbone. TEM analysis resulted in an average particles size of (25 – 50 nm) for SrO NPs and core–shell nanostructure of its composite (SrO@PTh CS) with shell thickness of (20–90 nm). The XRD analysis indicates a crystalline cubic structure of SrO NPs with particles size of ≈ 45 nm in average and interplanar space of (0.24 ∼ 0.36 nm). The crystallinity was relatively diminished to some extent for SrO@PTh CS which exhibits a particle size of about 85 nm and interplanar space of (0.13 ∼ 0.23 nm). A smart and novel electrochemical graphite paste sensor (GPS), based on SrO@PTh CS nanocomposite, has been fabricated for the ultrasensitive in-vitro detection of antiplatelet drug cilostazol. SrO@PTh CS nanocomposite-based square-wave voltammetry biosensor exhibited the lowest limits of detection of 1.99 × 10−10 and 9.83 × 10−10 M for cilostazol drug determination in bulk and human plasma samples, respectively compared to all the reported methods. It exhibited also good reproducibility, repeatability, long-term stability and was free from biological interference effects.

Fine-tuning of core–shell 1D nanoparticles for thermally conductive, yet electrically insulating, 3D-printable polymer nanocomposites

Core–shell nanostructures are particularly interesting for the development of dual-property nanofillers for nanocomposites.

Design of 2D/2D ZnIn2S4/MgAl-LDH core-shell nanostructures toward enhanced photodegradation of organic dyes

Design of 2D/2D ZnIn2S4/MgAl-LDH core-shell nanostructures toward enhanced photodegradation of organic dyes

Rational design of monodispersed Au@Pt core-shell nanostructures with excellent peroxidase-mimicking activity for colorimetric detection of Cr(VI).

Cr(VI) is one of the most typical heavy metal contaminants and rapid detection of Cr(VI) is highly important in food control and public health. Herein, a core-shell Au@Pt nanozyme-based colorimetric assay was developed for the rapid and sensitive detection of Cr(VI). The monodispersed Au@Pt core-shell nanoparticles exhibited high peroxidase-mimicking activity and can catalyze colorless TMB into blue-colored oxidized oxTMB. After the addition of Cr(VI), the oxTMB molecules can be reduced into colorless TMB. The ultrathin Pt shell can prevent the Pt component from aggregation, thus improving the catalytic activity of Au@Pt nanozyme. These Au@Pt nanozyme-based Cr(VI) assays exhibited high sensitivity and selectivity and displayed satisfactory recoveries in practical samples. Our work highlights opportunities for the development of core-shell nanozymes with extensive applications in food safety, biomedicine, and environmental monitoring.

Pentagonal nanowires from topological crystalline insulators: a platform for intrinsic core-shell nanowires and higher-order topology.

We report on the experimental realization of Pb1-xSnx Te pentagonal nanowires (NWs) with [110] orientation using molecular beam epitaxy techniques. Using first-principles calculations, we investigate the structural stability of NWs of SnTe and PbTe in three different structural phases: cubic, pentagonal with [001] orientation and pentagonal with [110] orientation. Within a semiclassical approach, we show that the interplay between ionic and covalent bonds favors the formation of pentagonal NWs. Additionally, we find that this pentagonal structure is more likely to occur in tellurides than in selenides. The disclination and twin boundary cause the electronic states originating from the NW core region to generate a conducting band connecting the valence and conduction bands, creating a symmetry-enforced metallic phase. The metallic core band has opposite slopes in the cases of Sn and Te twin boundaries, while the bands from the shell are insulating. We finally study the electronic and topological properties of pentagonal NWs unveiling their potential as a new platform for higher-order topology and fractional charge. These pentagonal NWs represent a unique case of intrinsic core-shell one-dimensional nanostructures with distinct structural, electronic and topological properties between the core and the shell region.