Multilayered Core Shell Structure Research Articles

In-situ Ag SPR assisted S-scheme ZnO-CdS multi-layer core-shell heterojunction for enhanced photocatalytic degradation: Energy band engineering and reactive dynamics

Constructing an efficient photocatalyst to accelerate charge separation with strong redox capacity is in pursuit all the way. Herein, a novel heterojunction was achieved for efficient organic degradation, which took advantages of S-scheme mechanism, metal surface plasma resonance (SPR) and unique morphology. The multi-layer core-shell structure can be regulated by aging time with template-free, and Ag nanoparticles were modified on the heterojunction by photochemical deposition in situ to facilitate electron transport and improve stability. S-scheme and SPR endues the heterojunction with broad light absorption, increased light utilization, efficient carrier separation, and strong redox capacity. An examination of reactive dynamics revealed that superoxide radicals and hydroxyl radicals are crucial for oxidative degradation. Introducing oxygen during the reaction process has been found to enhance the efficiency by 7 %. This article furnishes novel insights into a coordination of energy band engineering, structure regulation, as well as reaction process adjustment for facilitating photo-degradation reactions.

Preparation and properties of multilayer core-shell structure ammonium polyphosphate synergistic with THEIC for flame retardant LDPE

In this paper, a new type of highly efficient intumescent flame-retardant low-density polyethylene composite was prepared using two key technologies, namely, microencapsulation encapsulation technology and novel carbon formation technology. Precisely, β-cyclodextrin encapsulated modified ammonium polyphosphate@melamine formaldehyde resin (β-CDMCAPP@MF) was prepared by using Si-IFR synergistic flame retardant effect combined with the gel-solution method, and then flame retardant low-density polyethylene (LDPE) was prepared by compounding with tris-(2-hydroxyethyl) isocyanate (THEIC). The results showed that β-CDMCAPP@MF was modified with MF, β-CD, and silica coating. This modification resulted in excellent hydrophobicity and good compatibility with LDPE. The addition of IFR containing β-CDMCAPP@MF significantly improved the flame retardancy of the LDPE composites. Specifically, when 30 wt% of β-CDMCAPP@MF was added, the ultimate oxygen index of the composites reached 24.7 %, and V-0 grade and the tensile strength went 11.41 MPa. Compared with IFR/LDPE with the same proportion of MF@MCAPP and β-CD@MCAPP, the ultimate oxygen indices were increased by 9.72 % and 12.15 %, respectively. The introduction of THEIC into the flame retardant system resulted in a LOI value of 36.5 % and an FRI value of 2.523, which is 32.33 % higher than that of the composites containing 30 wt% of the flame retardant system (without THEIC). Cone calorimetry test results showed that introducing β-CDMCAPP@MF and THEIC significantly improved the smoke emission.

Multilayered Core–Shell Structure in an Impact Polypropylene Copolymer Investigated by Atomic Force Microscopy–Infrared

Multilayered Core–Shell Structure in an Impact Polypropylene Copolymer Investigated by Atomic Force Microscopy–Infrared

Heterostructure CoFe@(Co0.5Fe0.5)S@NCNT anchored on rice husk-based hierarchical porous carbon as a bifunctional cathode catalyst for Zn–air batteries

A bifunctional catalyst, characterized by its sea urchin-like morphology and multi-layer core–shell structure (CoFe@(Co0.5Fe0.5)S@NCNT), was synthesized within the restriction of RHPC' hierarchical pore structure.

Robust vibrational coherence protected by a core-shell structure in silver nanoclusters.

Vibrational coherence has attracted considerable research interests because of its potential functions in light harvesting systems. Although positive signs of vibrational coherence in metal nanoclusters have been observed, the underlying mechanism remains to be verified. Here, we demonstrate that robust vibrational coherence with a lifetime of 1 ps can be clearly identified in Ag44(SR)30 core-shell nanoclusters, in which an icosahedral Ag12 core is well protected by a dodecahedral Ag20 cage. Ultrafast spectroscopy reveals that two vibrational modes at around 2.4 THz and 1.6 THz, corresponding to the breathing mode and quadrupolar-like mode of the icosahedral Ag12 core, respectively, are responsible for the generation of vibrational coherence. In addition, the vibrational coherence of Ag44 has an additional high frequency mode (2.4 THz) when compared with that of Ag29, in which there is only one low frequency vibration mode (1.6 THz), and the relatively faster dephasing in two-layer Ag29 relative to that in Ag44 further supports the fact that the robust vibrational coherence in Ag44 is ascribed to its unique matryoshka-like core-shell structure. Our findings not only present unambiguous experimental evidence for a multi-layer core-shell structure protected vibrational coherence under ambient conditions but also offers a practical strategy for the design of highly efficient quantum optoelectronic devices.

Enhancement in ignition and combustion of solid propellants by interfacial modification of Al/AP composites with transition metals

To improve the ignition and combustion behaviors of Al, the strategy of interfacial modification using transition metals (TMs) for the Al/AP composites to produce the multi-layered core-shell structured Al@TMs@AP composite fuels is provided. The relevant Al-based composite fuels are fabricated using spray granulation method and their morphologies are characterized by SEM and TEM techniques. The ignition and combustion of the solid propellants prepared with the core-shell structured composite fuels are evaluated and compared with that of reference propellant formulated with typical compositions using laser ignition setup and combustion diagnostic system. Results indicate that the heats of reaction measured for the Al@TMs@AP contained propellants are increased by as high as 13%, suggesting the completeness in combustion of Al is greatly improved by construction of Al composites with the multi-layered core-shell structure. The ignition delay times are apparently shortened from 421 ms to 373 ms for the propellants with Al@TMs@AP involved, which proves that the promoted ignition of Al is achieved by surface modification with transition metals. Additionally, the significantly increased burning velocity is monitored for the Al@TMs@AP contained propellants at low-pressure regime leading to the corresponding pressure exponents to be reduced by more than 20%, which is beneficial to the stability in operation of solid rocket motors. At last, the higher combustion wave temperature and finer particle size in CCPs are observed for the propellants containing surface modified Al, and the plausible combustion mechanism is proposed based on the phase composition analysis for the CCPs of studied propellants.

Multifunctional core-shell nanoparticles for temperature sensing and anti-counterfeiting

In this paper, the multi-functional multi-layer core-shell structure NaYF4: Ce3+/Eu3+@NaYF4 @NaYF4: Ho3+/Yb3+ nanoparticles (NPs) were prepared. These multi-layer NPs can be applied in temperature sensing with high relative sensitivity. Moreover, these NPs can be used in multimode optical anti-counterfeiting. Based on structure design and doped earth ions optimized, the maximum relative sensitivity is further promoted from 0.9 %·K−1 at 234 K (Eu/Ho) to 5.1 %·K−1 at 113 K (Ce/Eu@Y@Ho/Yb) by the blocking effect of the inter layer and by cross-relaxation of introducing Ce3+ and Yb3+ ions. Meanwhile, by introducing Ce3+ and Yb3+ ions, the NPs provide multimode emissions under multiple excitations, which are beneficial for the application of optical anti-counterfeiting. The NPs present increased sensitivity of temperature sensing and improved security of optical anti-counterfeiting, which has promising applications in biological cell calibration, micro-integrated circuits, etc.

A Multifunctional Nanocarrier System for Highly Efficient and Targeted Delivery of Ketamine to NMDAR Sites for Improved Treatment of Depression.

Ketamine (KA), commonly used as an anesthetic, is now widely studied as an antidepressant for the treatment of depression. However, due to its side effects, such as addiction and cognitive impairment, the dosage and frequency of (S)-ketamine approved by the FDA for the treatment of refractory depression is very low, which limits its efficacy. Here, a new multifunctional nanocarrier system (AC-RM@HA-MS) with specific targeting capabilities is developed to improve the efficacy of KA treatment. KA-loaded NPs (AC-RM@HA-MS-KA) are constructed with a multilayer core-shell structure. KA-loaded mesoporous silica NPs are prepared, conjugated with hyaluronic acid (HA) as pore gatekeepers, and sheathed with an RBC-membrane (RM) for camouflage. Finally, the surface is tagged with bifunctional peptides (Ang-2-Con-G, AC) to achieve specific targeting. One peptide (Ang-2) is acted as a guide to facilitate the crossing of the blood-brain barrier (BBB), while the other (Con-G) is functioned as a ligand for the targeted delivery of KA to the N-methyl-D-aspartate receptor sites. Animal experiments reveal that AC-RM@HA-MS-KA NPs effectively cross the BBB and directionally accumulate in the curing areas, thereby alleviating the depressive symptoms and improving the cognitive functions of depressed mice. After treatment, the depressed mice almost completely return to normal without obvious symptoms of addiction.

Ultra-responsive and selective ethanol and acetone sensor based on Ce-doped Co3O4 microspheres assembled by submicron spheres with multilayer core-shell structure

The sensitive detection of ethanol and acetone is of great significance to address environmental toxicity concerns. Herein, a novel Ce-doped Co3O4 microsphere is precisely fabricated and assembled by abundant submicron spheres with multilayer core-shell configuration employing metal-organic frameworks (MOFs) as template and PVP as the structure-directing agent, and the formation mechanism of the microspheres with hierarchical structure is explored. Moreover, the gas sensing performance of Ce-doped Co3O4 sensor are investigated toward ethanol and acetone. The sensor based on CoCe0.025-350 (the molar ratio of CeCo = 0.025) microspheres exhibits remarkable responsiveness toward ethanol and acetone at relatively low operating temperatures (180 and 200 °C, respectively) and excellent long-term durability. The excellent sensing properties are firstly ascribed to the existence of abundant active sites and surface defects induced by Ce doping, and secondly originated from the hierarchical structure which benefits the absorption, diffusion of the gases on the sensor surface. Furthermore, detection limits as low as 0.1 ppm are achieved by the CoCe0.025–350 sensor. The sensing dynamics of the sensors are also investigated. The versatile strategy report herein can be employed to construct other transition metal oxides with excellent gas sensing properties.

A multi-layer core-shell structure CoFe2O4@Fe3C@NiO composite with high broadband electromagnetic wave-absorption performance.

Enhancing the absorption strength of electromagnetic waves and broadening the absorption band are constant goals in designing and preparing absorbing materials. The use of composites has shown to be a very efficient method for acquiring broadband-absorbing materials, while the construction of a core-shell structure has demonstrated a significant enhancement in absorption capability. In this paper, the nanocomposite metal-organic framework (MOF) derivative CoFe2O3@C with a double core-shell structure and the nanocomposite MOF derivative CoFe2O4@Fe3C@NiO with a three-layered core-shell structure have been prepared using a chemical compound. The multi-layer structure provides more active sites for the multiple reflection and scattering of electromagnetic waves, effectively improving the attenuation capability. The effective absorption band (EAB) (reflection loss (RL) ≤ -5 dB) of both CoFe2O3@C and CoFe2O4@Fe3C@NiO are broadened compared to that of the ZIF-67 derivative. In particular, the minimum reflection loss (RLmin) of CoFe2O3@C was -52.7 dB at 13.3 GHz and 2.04 mm, and the EAB (RL ≤ -5 dB) is as wide as 9.35GHz. Compared with the ZIF-67 derivative, the EAB exhibits a twofold rise, accompanied by a corresponding thickness increase of just 0.24 mm. At a matched thickness of 2.2 mm, the EAB of CoFe2O4@Fe3C@NiO can even reach 11.9 GHz.

High-intensity first near-infrared emission through energy migration in multilayered upconversion nanoparticles.

The development of Tm3+ 807 nm first near-infrared (NIR-I, 700-1000 nm) emission with second near-infrared (NIR-II, 1000-1700 nm) excitation is urgently needed, due to its potential application in biomedicine. In this work, a range of NaErF4:Yb@NaYF4:Yb@NaYF4:Yb,Tm@NaYF4 multilayer core-shell structure upconversion nanoparticles (UCNPs) were successfully prepared by a co-precipitation method. The strongest UC emissions can be obtained by changing the concentration of Yb3+ in the core and the first shell, and the proposed UC process was discussed in detail. The analysis shows that high-intensity NIR-I emission (807 nm) from Tm3+ and visible light from Er3+ were achieved through the energy migration among Yb3+ and the energy back transfer from Yb3+ to Er3+ under 1532 nm excitation. Besides, compared to bilayer UCNPs, multilayer core-shell UCNPs display superior optical performance. The high-intensity NIR-I emission at 807 nm (Tm3+:3H4 → 3H6) under 1532 nm NIR-II excitation demonstrates huge advantages in bioimaging.

Fabrication of novel multilayer core-shell structured nanofibers network reinforced carbon matrix composites for bone tissue engineering

To further optimize the structure of bone tissue engineering composites, silicon nitride nanowires-pyrolytic carbon-hydroxyapatite-carbon matrix (Si3N4nws@PyCnls-HA-C) composites with multilayer core–shell structures are synthesized by chemical vapor deposition (CVD), pulsed electrodeposition (PED), and chemical vapor infiltration (CVI) methods. The microstructure, in-vitro bioactivity, and in-vivo histocompatibility of Si3N4nws@PyCnls-HA-C (SPHC) composites are evaluated. In-vitro, the SPHC exhibited a cell proliferation rate of 157.7% and demonstrated outstanding protein adsorption. In-vivo, the SPHC demonstrated excellent histocompatibility. Therefore, the SPHC composites can serve as an alternative suitable biomaterial for bone tissue engineering.

Influence of Ti3AlC2 addition on water vapor resistance of low‐carbon Al2O3–C refractories

AbstractAl2O3–C refractories are potential candidates for use in gasifiers, and they are Cr2O3‐free. However, the oxidation of the carbon species and ceramic phases within the high‐temperature water vapor environment may deteriorate the integrity of the working lining. Ti3AlC2 has been verified as an effective antioxidant for Al2O3–C refractories in air. In this study, the structural transformation of Ti3AlC2 during heat treatment and the water vapor resistance of Ti3AlC2‐containing Al2O3–C refractories are investigated. The results show that the oxidation of Ti3AlC2 and Si in the matrix contributes to the in situ formation of a multilayer core–shell structure of TiC–AlTi2O5–Al6Si2O13. These structural evolutions improve densification and stimulate pore size refinement, which enhances the mechanical properties and thermal stress resistance of the specimens. In particular, the refined pore size contributes to the significantly improved water vapor resistance at high temperatures.

D-Cysteine Functionalized Superhydrophobic Nanocomposite Coating with Multiple-Action Antibacterial Property and Enhanced Mechanical Durability

In this study, a durable superhydrophobic antibacterial coating was developed by a facile spraying method. A mixture of bisphenol A diglycidyl ether (BADGE) and hydrophobic SiO2 nanoparticles was sprayed on carbon steel to provide a superhydrophobic substrate. D-cysteine (D-cys) functionalized SiO2/dopamine/silver nanoparticles with multilayer core-shell structure were then sprayed on superhydrophobic substrate to enhance antibacterial performance. The results of morphology observation and X-ray photoelectron spectroscopy (XPS) indicated the successful preparation of antibacterial nanoparticles and presented the hierarchical micro/nanostructures of coating surface. The as-prepared coating exhibited superhydrophobicity, with the water contact angle of ~153°. The coating was endowed with good mechanical durability, which maintained the water contact angle of ~150° after 180 cycles in tape-peel tests. The results of electrochemical impedance spectroscopy showed satisfactory corrosion resistance of this coating during 3 days of immersion in 3.5% NaCl solution. Furthermore, the coating showed excellent antibacterial performances against Escherichia coli and Pseudomonas aeruginosa, which benefited from the synergistic actions of low wettability of superhydrophobic surface, bactericidal behavior of Ag nanoparticles, and biofilm inhibition effect of D-cys.

Study on improving the self-repairing effect of cement-based materials by microbial mineralization coupled with inorganic minerals

As a green and intelligent method, the self-repairing technology based on microbial mineralization had obvious defects. In this study, microbial mineralization coupled with inorganic minerals was used to realize the full-depth repair of cracks in cement-based materials, and the feasibility was systematically demonstrated. The self-repairing carrier with multilayer core-shell structure was prepared, and the average particle strength was 36.12 N; Protective layer was composed of hydrated calcium silicate, hydrated calcium aluminate and other hydration products, which had relatively dense structure. Compatibility between microorganisms and carrier was deeply studied, and the growth performance of microorganisms after long-term storage was basically equivalent to that of the initial microorganisms. Composition and microstructure of products in crack area were studied by X ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), and products were mainly composed of calcium carbonate and ettringite with particle sizes of approximately 5–10 µm.The repair effect was studied by stereomicroscope, X ray computed tomography (X-CT) and ultrasonic detector. A large number of products were deposited on the two surfaces of the specimen, the crack was effectively filled; In addition, more products were deposited around the carrier, and a large number of cracks were repaired. Based on the above research, repair mechanism of the full-depth was identified. Microbial mineralization was mainly committed to the repair of crack surface, while ettringite prepared by inorganic reaction could repair the interior of crack, and the combination of the two paths could achieve the full-depth repair.

Preparation and microwave absorption properties of Gd–Co ferrite@silica@carbon multilayer core–shell structure composites

Developing microwave absorbing materials having a low reflection loss (RL) and wide effective absorption band (EAB) is important. In this study, spherical Gd–Co ferrite nanoparticles were synthesized by using a co-precipitation method. Silica and carbon shells were coated on the surface of Gd–Co ferrite particles by polymerizing tetraethyl orthosilicate and glucose. Three composites were prepared: Gd–Co ferrite@silica, Gd–Co ferrite@carbon, and Gd–Co ferrite@silica@carbon. The results showed that Gd–Co ferrite@silica@carbon exhibited the best absorbing performance, with its RL reaching the minimum value of –46.85 dB and its EAB was 3.14 GHz (8.74–11.88 GHz) at an absorption layer thickness of 2.5 mm and a frequency of 9.93 GHz. This excellent microwave absorption performance is attributed to two factors: the magnetic loss caused by the natural resonance and eddy current loss of Gd–Co ferrite and the dielectric loss enhanced by the interfacial polarization and dipole polarization caused by the multilayer core–shell structure such that the composite has excellent impedance matching. Thus, Gd–Co ferrite@silica@carbon composites can be used as high-performance microwave absorption material.

Enhanced photocatalytic performance and stability of multi-layer core-shell nanocomposite C@Pt/MoS2@CdS with full-spectrum response

The nanocomposite material C@Pt/MoS 2 @CdS was prepared by a simple microwave-assisted hydrothermal method combined with photoreduction method. The crystal structure, microstructure, and surface physical chemistry properties of the material were analyzed by X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance absorption spectroscopy (UV–vis/DRS), X-ray photoelectron energy spectroscopy (XPS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), nitrogen adsorption–desorption measurement, photoluminescence spectroscopy (PL), and electrochemical tests. As a result, this material has full-spectrum light absorption property and the composited CdS presents a good hexagonal phase. Moreover, the composite material presents a nanorod-like multi-layer core-shell structure, wherein the rod-like MoS 2 @CdS surface is covered with Pt and C. The formation of the multi-layer core-shell structure increases the specific surface area of as-composite material and strengthens its light absorption performance. The electrochemical impedance and transient photocurrent test results show that C@Pt/MoS 2 @CdS has the highest charge separation efficiency and enhanced photocurrent density compared with other systems. Photogenerated charge carriers have higher separation efficiency, and photogenerated electrons and holes exhibit longer life. During the photocatalysis experiments, the nanocomposite C@Pt/MoS 2 @CdS shows enhanced photodegradation activity under multi-modal photocatalytic experiments and excellent stability under visible light irradiation. In addition, C@Pt/MoS 2 @CdS has a strong photocatalytic water splitting ability. Under the same experimental conditions, its hydrogen production is 60 times that of commercially available P25. Through capture experiments, the reactive species in the photocatalytic reaction process were determined, and the possible photocatalytic reaction mechanism of this multi-layer core-shell C@Pt/MoS 2 @CdS nanocomposite was inferred. • Constructed a multi-layer core-shell structure photocatalytic composite material. • Improved the photocatalytic activity and stability of CdS-based photocatalyst. • The hydrogen production of C@Pt/MoS 2 @CdS was approximately 60 times that of commercially available P25. • Recombination rate of photogenerated charge carriers was effectively restrained.

Enhanced Anticorrosion Properties through Structured Particle Design of Waterborne Epoxy-Styrene-Acrylate Composite Emulsion

In order to develop a waterborne epoxy-styrene–acrylate composite latex with a better stability and anticorrosion resistance, a novel synthetic approach has been proposed. First, modified by methyl acrylic, epoxy resin containing terminal C=C double bonds was successfully synthesized, where epoxide groups were partially retained. Then, by structural design and multi-stage seed emulsion copolymerization, a stable waterborne epoxy-styrene-acrylate composite latex composed of a modified epoxy resin acrylate polymer as the core, inert polystyrene ester as the intermediate layer, and carboxyl acrylate polymer as the shell was successfully fabricated. The structure of the obtained latex was characterized by fourier transform infrared (FTIR) and transmission electron microscopy (TEM). The stability of the composite latex was tested based on the wet gel weight, Zeta potential, and storage stability, and the corrosion resistance of the composite latex films was analyzed by electrochemical measurements and salt spray tests. The thickness of each layer of the composite latex was calculated by the temperature random multi-frequency modulation DSC (TOPEM-DSC) technique. In addition to the successful emulsion copolymerization that occurred between the modified epoxy resin and acrylate monomer, the presence of carboxyl groups in the obtained latex was evidenced, while the epoxide groups were partially retained. The anticorrosion resistance and stability of the multilayer composite latex with the intermediate layer are better than that of the conventional core-shell latex. The outstanding stability and corrosion resistance is attributed to the multilayer core-shell structure. The TOPEM-DSC approach can accurately determine the thickness of the intermediate layer in the multilayer core-shell particles and is a new strategy for characterizing the core-shell structure of polymer particles with a similar monomer composition.

Carbon-Interlayer SnO2–Sb2O3 Composite Core–Shell Structure Anodes for Sodium-Ion Batteries

Although great efforts have been dedicated to improving electrochemical property of oxides anode material for sodium-ion batteries, the cycling life and rate capability of oxides anode materials are still far from its theoretical value. Herein, novel uniform SnO2@C@Sb2O3 submicrospheres with multilayer core–shell hollow structure have been synthesized as anode of sodium-ion batteries. The multilayer core–shell structure SnO2@C@Sb2O3 composite delivers a reversible capacity of 269 mAh g−1 at higher current density (1,500 mA g−1) after 100 cycles and exhibited excellent rate performance. The conductivity of the anode composite is promoted by the uniformly carbon dispersion through the whole submicrospheres. The dramatic volume change of electrode material could be mitigated by the porous core–shell structure of Sb2O3 and SnO2 during charge–discharge process. The enhanced specific capacity and rate performance are mainly ascribed to the integrity of structure and synergy effect between different metal oxides.

NIR II-responsive photon upconversion through energy migration in an ytterbium sublattice

Smart control of photon upconversion is a key strategy for lanthanide-based materials used in biological and photonic applications. However, this has remained a challenge for the upconversion luminescence of lanthanides under excitation in the second near-infrared (NIR II) biowindow instead of at the conventional 980 and 808 nm wavelengths. Here, we report a conceptual design for an energy-migratory ytterbium sublattice in an erbium-sensitized multilayer core–shell nanostructure that is able to achieve photon upconversion from a broad range of lanthanide ions (Yb3+, Tm3+, Ho3+, Gd3+, Eu3+ and Tb3+) under 1,530 nm irradiation. The quasi-single-band upconversion in the first near-infrared (NIR I) biowindow is also realized through fine manipulation of the introduced cross-relaxations. By establishing an interfacial energy-transfer-mediated nanostructure, we also gain a deep insight into the mechanistic features of the energy migration. These results open new opportunities in a variety of frontier applications, such as information security. An ytterbium sublattice in an erbium-sensitized multilayer core–shell structure enables photon upconversion from lanthanide ions under 1,530 nm irradiation.