Yolk-shell Nanostructures Research Articles

Electrochemical immunosensor using artificial enzyme-induced metallization for the ultra-sensitive detection of alpha fetoprotein

During the long incubation process of an electrochemical immunosensor, the sensitivity and detection limit of the sensor are seriously affected because the signal label easily falls off. In this work, we proposed an innovative artificial enzyme-induced metallization process. Firstly, an artificial enzyme is used to catalyze the solution to produce a reducing substance. Subsequently, metal ions in the solution are reduced to the surface of the electrode. Finally, the metal is dissolved by electrochemically, and the peak current is proportional to the alpha-fetoprotein (AFP) concentration. As a Lewis acid, CeO2 can hydrolyze phosphate bonds, and the hydrolysate ascorbic acid (AA) can reduce silver nanoparticles. In addition, the Au@CeO2 yolk shell nanostructure (Au@CeO2 YSNs) can greatly improve the catalytic activity of CeO2 and the conductivity of the signal tag. More importantly, since the signal substance is deposited on the electrode surface as soon as it is generated, the loss of electrical signals is reduced. Results show that the immunosensor has good analytical performance, a detection range of 0.1 pg/mL to 200 ng/mL, a detection limit of 0.035 pg/mL, and it performs well in serum samples. Therefore, this strategy provides a novel method for the early screening of AFP.

Ag‐CdS Yolk–Shell Heteronanostructures for Plasmon‐Enhanced Photocatalysis

The combination of a semiconductor and a plasmonic metal holds great promise for developing advanced photocatalysts. However, the realization of a heteronanostructure that accommodates both materials in an effective way has been a great challenge. Herein, we report a synthesis of a photocatalyst with a yolk–shell heteronanostructure, which contains a plasmonic Ag yolk inside a CdS shell. The sulfidation of Ag nanospheres followed by a controlled cation exchange reaction successfully generated the Ag‐CdS yolk–shell nanostructures. The as‐prepared heteronanostructures exhibited a prominent enhancement of photocatalytic activity toward hydrogen evolution reaction under visible‐light irradiation compared to CdS hollow nanoparticles without the Ag yolk. This improvement can be attributed to the plasmon energy transfer from the Ag yolk to the CdS shell and the yolk–shell structure that enables the multiple reflections of the incident light.

A novel synthesis of Ag@ZnO yolk-shell and ZnO hollow sphere nanostructures and comparison of their photocatalytic performances

ZnO hallow spheres and Ag@ZnO yolk-shell nanostructures were synthesized using a hydrothermal method and their dye absorption and photocatalytic performances were investigated. For ZnO hollow spheres preparation, carbon sphere templates were used and ZnO hollow spheres with average size of 200 nm were obtained. Also, Ag@C core-shell spheres with diameters of 350 nm were prepared by a hydrothermal method and were used as template to prepare Ag@ZnO yolk-shell spheres. The samples were characterized using XRD, SEM, TEM, EDX and FT-IR measurements. The results confirmed the formation of yolk-shell nanostructure. The average diameters of ZnO shells and Ag cores, 300 and 55 nm were measured respectively. Then Congo red dye absorption of ZnO hollow spheres and Ag@ZnO yolk-shells were examined. The results showed that the ZnO hollow spheres were a better dye absorbent, but Ag@ZnO yolk-shells had better photocatalytic performance probably due to presence of Ag nanoparticles as a plasmonic material.

Solvent‐Dependent Adsorption‐Driven Mechanism for MOFs‐Based Yolk–Shell Nanostructures

AbstractMetal‐organic frameworks (MOFs)‐based yolk–shell nanostructures have drawn enormous attention recently due to their multifunctionality. However, the regulations of the size and morphology of yolk–shell nanostructures are still limited by the unclear formation mechanism. Herein, we first demonstrated a solvent‐dependent adsorption‐driven mechanism for synthesizing yolk–shelled MOFs‐based nanostructures coated with mesoporous SiO2 shells (ZIF‐8@mSiO2) with tunable size and morphology. The selective and competitive adsorption of methanol (CH3OH) and water (H2O) on ZIF‐8 core were found to have decisive effects on inducing the morphology evolution of yolk–shell nanostructures. The obtained yolk–shelled ZIF‐8@mSiO2 nanostructures show great promise in generating acoustic cavitation effect for sonodynamic cancer therapy in vitro. We believe that this work will not only help us to design novel MOFs‐based yolk–shell nanostructures, but also promote the widespread application of MOFs materials.

Solvent-Dependent Adsorption-Driven Mechanism for MOFs-Based Yolk-Shell Nanostructures.

Metal-organic frameworks (MOFs)-based yolk-shell nanostructures have drawn enormous attention recently due to their multifunctionality. However, the regulations of the size and morphology of yolk-shell nanostructures are still limited by the unclear formation mechanism. Herein, we first demonstrated a solvent-dependent adsorption-driven mechanism for synthesizing yolk-shelled MOFs-based nanostructures coated with mesoporous SiO2 shells (ZIF-8@mSiO2 ) with tunable size and morphology. The selective and competitive adsorption of methanol (CH3 OH) and water (H2 O) on ZIF-8 core were found to have decisive effects on inducing the morphology evolution of yolk-shell nanostructures. The obtained yolk-shelled ZIF-8@mSiO2 nanostructures show great promise in generating acoustic cavitation effect for sonodynamic cancer therapy in vitro. We believe that this work will not only help us to design novel MOFs-based yolk-shell nanostructures, but also promote the widespread application of MOFs materials.

Sn/FeSn2/FeO@N-doped carbon yolk-shell nanocubes with multi-phase nanocores for highly stable anode materials in lithium-ion battery

A two-step approach using co-precipitation and thermal reduction treatment strategy is adopted to synthesize Sn/FeSn2/[email protected] carbon yolk-shell nanocubes with multi-phase nanocores for highly stable anode materials in lithium-ion battery. In the novel yolk-shell nanostructure, the multi-phase nanocores consist of Sn, FeSn2 and FeO nanoparticles while the shell is made of amorphous nitrogen-doped carbon. With the synergy of multi-phase nanocores, the confining effect of the carbon shell and the in-depth nanocrystallization of Sn/FeSn2/FeO nanocores in the yolk-shell nanostructures, Sn/FeSn2/[email protected] nanocomposites exhibit high capacity of 601 mAh g−1 at 0.1 Ag−1 after the 300th cycle and capacity of 484 mAh g−1 at 0.5 Ag−1 after the 600th cycle. Our work suggests that high-performance battery materials can be produced by rational structure engineering of multi-phase nanocomposites.

Well-dispersed tin nanoparticles encapsulated in amorphous carbon tubes as high-performance anode for lithium ion batteries

Tin/carbon (Sn/C) nanocomposite is considered as a promising anode material for high-performance Li-ion batteries (LIBs). However, since the carbon matrix is always derived from high-temperature carbonization of polymers and Sn has a low melting point (232 °C), the Sn nanoparticles in the Sn/C tend to be heavily aggregated during the carbonization process. It is thus challenging to synthesize well-dispersed Sn nanoparticles in a carbon matrix. Here, we report a facile templating method to encapsulate uniform well-dispersed Sn nanoparticles in amorphous carbon tube (Sn@aCT). The electrode fabricated with the hierarchical Sn@aCT exhibits excellent cycle performance. A stable specific capacity of 870 mAh g−1 after 350 cycles and a Li-ion diffusion coefficient as high as are obtained. Meanwhile, the intermediate structure of SnO2@aCT and a carbon-coated Sn yolk-shell nanostructure (Sn@C-YS) are investigated for comparison. The results further manifest the advantage of the architecture of the Sn@aCT. Our strategy provides a feasible way to optimize Sn/C nanocomposite as a high-performance anode material for LIBs.

In Situ Study of the Wet Chemical Etching of SiO2 and Nanoparticle@SiO2 Core-Shell Nanospheres.

The recent development of liquid cell (scanning) transmission electron microscopy (LC-(S)TEM) has opened the unique possibility of studying the chemical behavior of nanomaterials down to the nanoscale in a liquid environment. Here, we show that the chemically induced etching of three different types of silica-based silica nanoparticles can be reliably studied at the single particle level using LC-(S)TEM with a negligible effect of the electron beam, and we demonstrate this method by successfully monitoring the formation of silica-based heterogeneous yolk–shell nanostructures. By scrutinizing the influence of electron beam irradiation, we show that the cumulative electron dose on the imaging area plays a crucial role in the observed damage and needs to be considered during experimental design. Monte-Carlo simulations of the electron trajectories during LC-(S)TEM experiments allowed us to relate the cumulative electron dose to the deposited energy on the particles, which was found to significantly alter the silica network under imaging conditions of nanoparticles. We used these optimized LC-(S)TEM imaging conditions to systematically characterize the wet etching of silica and metal(oxide)–silica core–shell nanoparticles with cores of gold and iron oxide, which are representative of many other core–silica–shell systems. The LC-(S)TEM method reliably reproduced the etching patterns of Stöber, water-in-oil reverse microemulsion (WORM), and amino acid-catalyzed silica particles that were reported before in the literature. Furthermore, we directly visualized the formation of yolk–shell structures from the wet etching of Au@Stöber silica and Fe3O4@WORM silica core–shell nanospheres.

Yolk-shell nanostructures: synthesis, photocatalysis and interfacial charge dynamics.

Solar energy has long been regarded as a promising alternative and sustainable energy source. In this regard, photocatalysts emerge as a versatile paradigm that can practically transform solar energy into chemical energy. At present, unsatisfactory conversion efficiency is a major obstacle to the widespread deployment of photocatalysis technology. Many structural engineering strategies have been proposed to address the issue of insufficient activity for semiconductor photocatalysts. Among them, creation of yolk–shell nanostructures which possess many beneficial features, such as large surface area, efficient light harvesting, homogeneous catalytic environment and enhanced molecular diffusion kinetics, has attracted particular attention. This review summarizes the developments that have been made for the preparation and photocatalytic applications of yolk–shell nanostructures. Additional focus is placed on the realization of interfacial charge dynamics and the possibility of achieving spatial separation of charge carriers for this unique nanoarchitecture as charge transfer is the most critical factor determining the overall photocatalytic efficiency. A future perspective that can facilitate the advancement of using yolk–shell nanostructures in sophisticated photocatalytic systems is also presented.

An advanced hybrid supercapacitor constructed from rugby-ball-like NiCo2Se4 yolk–shell nanostructures

A facile strategy is developed to fabricate rugby-ball-like NiCo2Se4 yolk–shell nanostructures (RB-NCS) as the cathode electrode material for hybrid supercapacitors.

Porous yolk-shell Fe/Fe3O4 nanoparticles with controlled exposure of highly active Fe(0) for cancer therapy

The iron-based Fenton-type reaction has drawn tremendous attention in cancer therapy. Compared with oxidized iron, Fe(0) possesses high catalytic activity but unstable for biomedical application. Here, we report a new strategy to stabilize Fe(0) via a porous yolk shell nanostructure of Fe/Fe3O4 (PYSNPs) in normal physiological condition, and to control the release of Fe(0) in tumor microenvironment for enhanced cancer therapy. These PYSNPs display superior tumor inhibition with the IC50 down to 20 μg/mL (over 1 mg/mL for iron oxide nanoparticles as control) for HepG2 cell. A single intravenous injection of as low as 1 mg/kg dosage is effective to suppress tumor growth in vivo. Moreover, the disintegration of PYSNPs in the acidic tumor microenvironment could cause significant change in MRI signal for contrast-enhanced diagnosis. Of note, the resulting Fe3O4 fragments are renal clearable with minimized side effect. In all, this work represented a nanoplatform to stabilize and selectively deliver Fe(0) for highly effective cancer therapy.

A general strategy for enabling Fe3O4 with enhanced lithium storage performance: Synergy between yolk-shell nanostructures and doping-free carbon

Transition metal oxides such as Fe3O4 have been widely explored as the anode material for lithium-ion batteries (LIBs). The construction of yolk-shelled structure and doping-free carbon shell is considered as an ideal strategy to advance their lithium storage properties. Herein, a facile and scalable strategy is provided to fabricate the carbon shell on the surface of Fe3O4 nanocubes. Then, a series of yolk-shelled Fe3O4 nanocubes are synthesized through etching-in-a-box strategy. Thanks to the doping-free carbon shelled and the void between the Fe3O4 and carbon, the yolk-shelled Fe3O4 nanocubes electrode as anode materials for LIBs display a high specific capacity (910 mA h g−1 at 100 mA g−1) and excellent cycle stability (451 mA h g−1 after 2000 cycles at 5 A g−1). The method to produce doping-free carbon shell is easy and efficient and can be readily extended to design other high-performance LIBs anode materials.

NIR-II-Activated Yolk-Shell Nanostructures as an Intelligent Platform for Parkinsonian Therapy.

Despite the relative severity of Parkinson's disease (PD), to date, there has been only limited success in preventing or treating this condition owing to the low permeability of the blood-brain barrier (BBB), which makes the cerebral delivery of pharmaceutical agents very challenging. In the present study, we explored an approach to increasing BBB permeability via the use of mesoporous silica-encapsulated gold nanorods (MSNs-AuNRs) that could reliably achieve a robust photothermal effect in response to second near-infrared (NIR-II) irradiation. To test the potential anti-Parkinsonian activity, we loaded MSNs-AuNRs with the frequently utilized anti-PD agent quercetin (QCT) to yield MSNs-AuNRs@QCT. Following NIR-II irradiation, we observed a dramatical increase in QCT transfer through the BBB, indicating that MSNs-AuNRs may enhance BBB permeability via the photothermal effect. These findings were further supported by rat pharmacokinetic studies, which clearly revealed that the combination of MSNs-AuNRs and NIR-II irradiation was associated with significantly improved brain accumulation. In a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced murine model of PD, we also found that intravenous MSNs-AuNRs@QCT delivery and subsequent NIR-II irradiation was sufficient to markedly reduce the neurological abnormalities in these mice. Together, this combination offers promising potential as a nanoplatform for neuroprotective drug delivery and treatment of PD.

Facile Synthesis of Yolk–Shell Bi@C Nanospheres with Superior Li-ion Storage Performances

Recently, exploring appropriate anode materials for current commercial lithium-ion batteries (LIBs) with suitable operating potential and long cycle life has attracted extensive attention. Herein, a novel anode of Bi nanoparticles fully encapsulated in carbon nanosphere framework with uniform yolk–shell nanostructure was prepared via a facile hydrothermal method. Due to the special structure design, this anode of yolk–shell Bi@C can effectively moderate the volume exchange, avoid the aggregation of active Bi nanoparticle and provide superior kinetic during discharge/charge process. Cycling in the voltage of 0.01–2.0 V, yolk–shell Bi@C anode exhibits outstanding Li+ storage performance (a reversible capacity over 200 mAh g−1 after 400 cycles at 1.25 A g−1) and excellent rate capability (a capacity of 404, 347, 304, 275, 240, 199 and 163 mAh g−1 at 0.05, 0.1, 0.25, 0.5, 1.0, 1.8 and 3.2 A g−1, respectively). This work indicates that rational design of nanostructured anode materials is highly applicable for the next-generation LIBs.

Multifunctional Smart Yolk-Shell Nanostructure with Mesoporous MnO2 Shell for Enhanced Cancer Therapy.

Manganese dioxide (MnO2) nanostructures have aroused great interest among analytical and biological medicine researchers as a unique type of tumor microenvironment (TME)-responsive nanomaterial. However, reliable approaches for synthesizing yolk-shell nanostructures (YSNs) with mesoporous MnO2 shell still remain exciting challenges. Herein, a YSN (size, ∼75 nm) containing a mesoporous MnO2 shell and Er3+-doped upconversion/downconversion nanoparticle (UCNP) core with a large cavity is demonstrated for the first time. This nanostructure not only integrates diverse functional components including MnO2, UCNPs, and YSNs into one system but also endows a size-controllable hollow cavity and thickness-tunable MnO2 layers, which can load various guest molecules like photosensitizers, methylene blue (MB), and the anticancer drugs doxorubicin (DOX). NIR-II fluorescence and photoacoustic (PA) imaging from UCNP and MB, respectively, can monitor the enrichment of the nanomaterials in the tumors for guiding chemo-photodynamic therapy (PDT) in vivo. In the TME, degradation of the mMnO2 shell by H2O2 and GSH not only generates Mn2+ for tumor-specific T1-MR imaging but also releases O2 and drugs for tumor-specific treatment. The result confirmed that imaging-guided enhanced chemo-PDT combination therapy that benefited from the unique structural features of YSNs could substantially improve the therapeutic effectiveness toward malignant tumors compared to monotherapy.

Yolk-Shell Fe3 O4 @Void@N-Carbon Nanostructures Based on One-Step Deposition of SiO2 and Resorcinol-3-Aminophenol-Formaldehyde (R-APF) Cocondensed Resin Dual Layers onto Fe3 O4 Nanoclusters.

Yolk-shell magnetic nanoparticles@nitrogen-enriched Carbon nanostructures with a magnetic core and a hollow nitrogen-enriched carbon shell exhibit considerable promise in various applications, such as drug delivery, heterogenous catalysts, removal of metal ions and organic pollutants, and screening of biomolecules, due to their strong magnetic response, unique cavities, and the selective absorption ability of nitrogen-enriched groups. However, their complicated synthesis always involves possible surface modification, layer-by-layer deposition of a sacrificial middle layer and an outer nitrogen-enriched layer on magnetic nanoparticles, subsequent carbonization, and final removal of the sacrificial middle layer. Herein, yolk-shell Fe3 O4 @nitrogen-enriched carbon nanostructures are constructed based on NH4 + ion-induced one-step deposition of SiO2 and Resorcinol-3-aminophenol-formaldehyde cocondensed resin (R-APF) dual layers onto poly acrylic acid-modified Fe3 O4 nanoclusters without any extra surface modification. The N-Carbon shell thickness of the yolk-shell Fe3 O4 @Void@N-Carbon nanostructure can be finely tailored though tailoring the feeding amount of aminophenol and resorcinol to tune the thickness of the outer R-APF resin shell onto Fe3 O4 @SiO2 intermediate particles. This NH4 + ion-induced one-pot deposition of double layers can effectively promote synthesis efficiency of this kind of yolk-shell nanostructure.

Mesoporous Silica Encapsulated Metal-Organic Frameworks for Heterogeneous Catalysis

Encapsulation of metal-organic frameworks (MOFs) with a shell of mesoporous silica can boost overall performance of MOFs, offering versatility for synthetic architecture of integrated nanocatalysts with reactor-like features. Recently, Yu et al. report a green approach to make yolk-shell nanoreactors.

A novel silicon nanoparticles-infilled capsule prepared by an oil-in-water emulsion strategy for high-performance Li-ion battery anodes

Conventional approaches for preparing yolk-shell nanostructures require complicated procedures such as multi-step coatings and template removal. Herein, we present a new and general strategy for making yolk-shell nanocomposites based on an oil-in-water emulsion system. As a demonstrating case, silicon nanoparticles were dispersed in an oil phase which was in an oil-in-water emulsion; then the oil/water interface was in-situ polymerized to form microcapsules. After carbonization, the shell of microcapsules was formed. The Li-ion battery anodes based on the microcapsules exhibit a good electrochemical performance including stable capacity and high rate-performance. The capacity remains 1100 mAh g−1 after 500 cycles at a current density of 1.9 A g−1, along with a Coulombic efficiency of ≈ 99.9%. In addition, the method presented here is general, which is applicable for the synthesis of many yolk shell-structured nanocomposites.

Spontaneous and reversible hollowing of alloy anode nanocrystals for stable battery cycling.

High-capacity alloy anode materials for Li-ion batteries have long been held back by limited cyclability caused by the large volume changes during lithium insertion and removal. Hollow and yolk-shell nanostructures have been used to increase the cycling stability by providing an inner void space to accommodate volume changes and a mechanically and dimensionally stable outer surface. These materials, however, require complex synthesis procedures. Here, using in situ transmission electron microscopy, we show that sufficiently small antimony nanocrystals spontaneously form uniform voids on the removal of lithium, which are then reversibly filled and vacated during cycling. This behaviour is found to arise from a resilient native oxide layer that allows for an initial expansion during lithiation but mechanically prevents shrinkage as antimony forms voids during delithiation. We developed a chemomechanical model that explains these observations, and we demonstrate that this behaviour is size dependent. Thus, antimony naturally evolves to form optimal nanostructures for alloy anodes, as we show through electrochemical experiments in a half-cell configuration in which 15-nm antimony nanocrystals have a consistently higher Coulombic efficiency than larger nanoparticles.

Core-Shell and Yolk-Shell Covalent Organic Framework Nanostructures with Size-Selective Permeability

Many methods exist for the synthesis of covalent organic frameworks (COFs), but precise morphology control allowing the tailoring of core-shell and yolk-shell nanostructures has been elusive, mainly due to poor control of the reaction-diffusion processes. Herein, we propose the precise regulation of the COF generation and decomposition rates and their relationship with the diffusion rate of COF species during the synthesis, which enables a successful preparation of core-shell, yolk-shell, hollow-spherical, and multiple yolk-shell COF structures with tunable sizes ranging from 200 to 1,400 nm. Formed COF structures can serve as nanoreactors or nanocontainers, with the shell layer providing molecular-size selectivity determined by the nanopore size demonstrated here using Suzuki coupling reactions with phenylboronic acid, which produce a size-cutoff efficiency for halogenated aromatics approaching 100%. The precise morphology design and control of COF particles and hybrids may help enhance application efficiencies and provide access to new functionalities for COF materials.