Ultrathin Shell Research Articles

Hierarchical covalent organic frameworks-modified diatomite for efficient separation of bisphenol A from water in a convenient column mode

To optimize the highly stacked, lamellar covalent organic frameworks (COF) with more easily accessible micropores for molecular separations, a facile and economical strategy, using the naturally available diatomite (Dt) as a substrate, is proposed to fabricate hierarchical Dt@COF hybrids through an in-situ solvothermal method to grow a uniform COF shell on Dt. This strategy not only enormously enhances the adsorption capacity of diatomite through introducing abundant micropores, but also endows the grown COFs with highly accessible adsorption sites for molecular adsorption owing to the ultrathin COFs shell and the intrinsic porosity of the diatomite matrix. The maximum adsorption capacity of COFs from Dt@COF-0.04 is 686 mg g−1 toward bisphenol A (BPA), outperforming the bulk COFs adsorbent (∼381 mg g−1). Significantly, in a more convenient column separation mode, the equilibrium adsorption amount of Dt@COF-0.04 is ∼3 times greater than that of the COF/Dt mixture. It is found that the thin COFs shell and the intrinsic microchannels of diatomite nanoplates synergistically facilitate the diffusion of water molecules and pollutants, leading to the outstanding performance of Dt@COF adsorbents. The results indicate that the hierarchical Dt@COF hybrids have great application potential in the separation of organic pollutants from water for environmental remediation.

Ion compaction effect in hollow FePt nanochains with ultrathin shell under low energy ion irradiation

Ion compaction effect in hollow FePt nanochains with ultrathin shell under low energy ion irradiation

Engineering of Oxide Protected Gold Nanoparticles.

Gold nanoparticles that are partially or fully covered by metal oxide shells provide superior functionality and stability for catalytic and plasmonic applications. Yet, facile methods for controlled fabrication of thin oxide layers on metal nanoparticles are lacking. Here, we report an easy method to reliably engineer thin Ga2O3 shells on Au nanoparticles, based on liquid-phase chemical oxidation of Au-Ga alloy nanoparticles. We demonstrate that, with this technique, laminar and ultrathin Ga2O3 shells can be grown with ranging thickness from sub- to several monolayers. We show how the localized surface plasmon resonance can be used to understand the reaction process and quantitatively monitor the Ga2O3 shell growth. Finally, we demonstrate that the Ga2O3 coating prevents sintering of the Au nanoparticles, providing thermal stability to at least 250 °C. This approach, building on dealloying of bimetallic nanoparticles by the solution-phase oxidation, promises a general technique for achieving controlled metal/oxide core/shell nanoparticles.

Assessing the insulating properties of an ultrathin SrTiO3 shell grown around GaAs nanowires with molecular beam epitaxy

We have studied electronic transport in undoped GaAs/SrTiO3 core–shell nanowires standing on their Si substrate with two-tip scanning tunneling microscopy in ultrahigh vacuum. The resistance profile along the nanowires is proportional to the tip separation with resistances per unit length of a few GΩ/μm. Examination of the different transport pathways parallel to the nanowire growth axis reveals that the measured resistance is consistent with a conduction along the interfacial states at the GaAs{110} sidewalls, the 2 nm thick SrTiO3 shell being as much as resistive, despite oxygen deficient growth conditions. The origin of the shell resistivity is discussed in light of the nanowire analysis with transmission electron microscopy and Raman spectroscopy, providing good grounds for the use of SrTiO3 shells as gate insulators.

Ag Nanoparticles with Ultrathin Au Shell-Based Lateral Flow Immunoassay for Colorimetric and SERS Dual-Mode Detection of SARS-CoV-2 IgG.

Immunoglobulin detection is essential for diagnosing progression of SARS-CoV-2 infection, for which SARS-CoV-2 IgG is one of the most important indexes. In this paper, Ag nanoparticles with ultrathin Au shells (∼2 nm) embedded with 4-mercaptobenzoic acid (MBA) (AgMBA@Au) were manufactured via a ligand-assisted epitaxial growth method and integrated into lateral flow immunoassay (LFIA) for colorimetric and SERS dual-mode detection of SARS-CoV-2 IgG. AgMBA@Au possessed not only the surface chemistry advantages of Au but also the superior optical characteristics of Ag. Moreover, the nanogap between the Ag core and the Au shell also greatly enhanced the Raman signal. After being modified with anti-human antibodies, AgMBA@Au recognized and combined with SARS-CoV-2 IgG, which was captured by the SARS-CoV-2 spike protein on the T line. Qualitative analysis was achieved by visually observing the color of the T line, and quantitative analysis was conducted by measuring the SERS signal with a sensitivity four orders of magnitude higher (detection limit: 0.22 pg/mL). The intra-assay and inter-assay variation coefficients were 7.7 and 10.3%, respectively, and other proteins at concentrations of 10 to 20 times higher than those of SARS-CoV-2 IgG could hardly produce distinguishable signals, confirming good reproducibility and specificity. Finally, this method was used to detect 107 clinical serum samples. The results agreed well with those obtained from enzyme-linked immunosorbent assay kits and were significantly better than those of the colloidal gold test strips. Therefore, this dual-mode LFIA has great potential in clinical practical applications and can be used to screen and trace the early immune response of SARS-CoV-2.

Hollow double-shell stacked CdS@ZnIn2S4 photocatalyst incorporating spatially separated dual cocatalysts for the enhanced photocatalytic hydrogen evolution and hydrogen peroxide production

Semiconductor-based photocatalytic water splitting is a promising technology to convert solar energy into chemical energy. However, the photocatalytic performance is seriously limited by the low photo-generated charge separation efficiency and high interfacial reaction resistance. Here, a hollow double-shell stacked CdS@ZnIn2S4 system was firstly constructed. The Pt and Co3O4 nanoparticles (NPs) as the hydrogen evolution and the hydrogen peroxide production cocatalysts were loaded on the inner surface and outer surface of CdS@ZnIn2S4 to obtain a novel Pt/CdS@ZnIn2S4/Co3O4 photocatalyst. Compared with the CdS@ZnIn2S4 and dual cocatalysts randomly incorporated CdS@ZnIn2S4/(Pt+Co3O4) sample, this well-designed photocatalyst shows high photocatalytic performance with hydrogen evolution rate and H2O2 production rate reached 8.53 mmol g−1 h−1 and 5.26 mmol g−1 h−1, respectively, which are 3.8 and 1.8 times higher than those of CdS@ZnIn2S4 sample. The enhanced photocatalytic performance can be attributed to the formation of compact heterojunction structure between the ultrathin double shells, which can promote the separation of electron-hole pairs due to its built-in field effect. Besides, the synergistic effect of spatially separated dual cocatalysts are beneficial to the migration of the photo-generated charges to the opposite direction and the suppression of the reverse reaction. This work would pave a way to design unique structure and high-performanced photocatalyts towards photocatalytic water splitting.

Interfacial interaction-dependent in situ restructure of NiO/TiO2 photocatalysts

Composite photocatalysts often undergo in situ restructure during photocatalytic reactions. Herein we report that the NiO-TiO2 interfacial interaction of NiO/TiO2 photocatalysts prepared via an ion exchange method strongly influences in situ restructure processes. With the Ni loading increasing, TiO2 supported NiO nanoparticles, TiO2 (core)-NiO (ultrathin shell) and TiO2 (core)-NiO (ultrathin shell) supported NiO nanoparticles are acquired sequentially. During photocatalytic water reduction reaction, TiO2 supported NiO nanoparticles and TiO2 (core)-NiO (ultrathin shell) are stable due to strong NiO-TiO2 interfacial interaction, whereas NiO nanoparticles supported on TiO2 (core)-NiO (ultrathin shell) are reduced to Ni nanoparticles, resulting enhanced photocatalytic activity. These findings bridge heterogeneous thermocatalysis and photocatalysis with the phenomenon of interfacial interaction-dependent in situ restructure.

Load-Carrying Capacity of Ultra-Thin Shells with and without CNTs Reinforcement

Isotropic ultra-thin shells or membranes, as well as cable–membrane structures, cannot resist loads at the initial state and always require a form-finding process to reach the steady state. After this stage, they can work in a pure membrane state and quickly experience large deflection behavior, even with a small amplitude of load. This paper aims to improve the load-carrying capacity and strength of membrane structures via exploiting the advantages of functionally graded carbon-nanotube-reinforced composite (FG-CNTRC) material. In this work, the load-carrying capacity and nonlinear behavior of membrane structures with and without CNTs reinforcement are first investigated using a unified adaptive approach (UAA). As an advantage of UAA, both form finding and postbuckling analysis are performed conveniently and simultaneously based on a modified Riks method. Different from the classical membrane theory, the present theory (first-order shear deformation theory) simultaneously takes into account the membrane, shear and bending strains/stiffnesses of structures. Accordingly, the present formulation can be applied adaptively and naturally to various types of FG-CNTRC structures: plates, shells and membranes. A verification study is conducted to show the high accuracy of the present approach and formulation. Effects of CNTs distribution, volume fraction, thickness, curvature, radius-to-thickness and length-to-radius ratios on the form-finding and postbuckling behavior of FG-CNTRC membranes are particularly investigated. In particular, equilibrium paths of FG-CNTRC membrane structures are first provided in this paper.

Osmosis-Mediated Microfluidic Production of Submillimeter-Sized Capsules with an Ultrathin Shell for Cosmetic Applications.

There is a demand for submillimeter-sized capsules with an ultrathin shell with high visibility and no tactile sensation after release for cosmetic applications. However, neither bulk emulsification nor droplet microfluidics can directly produce such capsules in a controlled manner. Herein, we report the microfluidic production of submillimeter-sized capsules with a spacious lumen and ultrathin biodegradable shell through osmotic inflation of water-in-oil-in-water (W/O/W) double-emulsion drops. Monodisperse double-emulsion drops are produced with a capillary microfluidic device to have an organic solution of poly(lactic-co-glycolic acid) (PLGA) in the middle oil layer. Hypotonic conditions inflate the drops, leading to core volume expansion and oil-layer thickness reduction. Afterward, the oil layer is consolidated to the PLGA shell through solvent evaporation. The degree of inflation is controllable with the osmotic pressure. With a strong hypotonic condition, the capsule radius increases up to 330 μm and the shell thickness decreases to 1 μm so that the ratio of the thickness to radius is as small as 0.006. The large capsules with an ultrathin shell readily release their encapsulant under an external force by shell rupture. In the mechanical test of single capsules, the threshold strain for shell rupture is reduced from 75 to 12%, and the threshold stress is decreased by two orders for highly inflated capsules in comparison with noninflated ones. During the shell rupture, the tactile sensation of capsules gradually disappears as the capsules lose volume and the residual shells are ultrathin.

Optimizing Lattice Strain and Electron Effect of Ultrathin Platinum Nanoshells through Core–Shell Construction toward Superior Electrocatalytic Hydrogen Evolution

For optimizing the lattice strain and electron effect of Pt catalysts toward boosting their intrinsic electrocatalytic properties, we herein report the building of ultrathin Pt nanoshells in subnanoscale on the fine AgPd alloy cores, which are produced by alloying Pd atoms into the Ag nanoparticles through galvanic replacement reaction (GRR). Because of the smaller lattice expansion and modified electron effect of the ultrathin Pt shells in core–shell AgPd@Pt nanoparticles relative to those in core–shell Ag@Pt counterparts, the d-band center of core–shell AgPd@Pt nanoparticles locates at a lower position, favorable for weakening the adsorption of hydrogen and promoting their electrocatalysis for hydrogen evolution reaction (HER) in an acidic medium. Specifically, the core–shell AgPd@Pt nanoparticles with an appropriate Pt shell thickness not only show the lowest overpotential of 15.8 mV at 10 mA cm–2 in comparison with 27 mV of core–shell Ag@Pt nanoparticles, and 35 mV of commercial Pt/C catalyst, but also possesses the highest mass activity (1092.6 A g–1) at the overpotential of 25 mV, which is 1.58 times higher than that of core–shell Ag@Pt nanoparticles (693.5 A g–1) and 6.74 times higher than that of commercial Pt/C (162 A g–1). Moreover, alloying Pd into Ag cores also endows the ultrathin Pt shells with excellent electrocatalytic durability for HER. The concept of both lattice strain and electronic engineering through a core–shell construction may provide guidance for designing other highly catalytic and cost-effective nanostructures for a myriad of electrochemical reactions.

Suppressed Dissolution and Enhanced Desolvation in Core–Shell MoO3@TiO2 Nanorods as a High‐Rate and Long‐Life Anode Material for Proton Batteries

AbstractRechargeable proton batteries are attractive, because protons as a charge carrier have a small ionic radius, a lightest mass, and a high abundance on Earth. MoO3, as one of the promising anode materials in rechargeable proton batteries, suffers from the severe dissolution in acidic electrolytes upon cycling. Here, an ultrathin TiO2 shell is coated on MoO3 nanorods to suppress the detrimental dissolution during cycles. TiO2 also lowers the desolvation energy of hydrated protons, promoting the reaction kinetics. As a result, MoO3@TiO2 displays outstanding electrochemical performance, especially at high rates (171.0 mAh g−1 at 30 A g−1) and at high mass loadings (17 mAh cm−2 at 104 mg cm−2). The full cells constructed with MnO2 deliver an energy density up to 252.9 Wh kg−1 and a power density of 18.3 kW kg−1. Ex situ X‐ray diffraction and X‐ray photoelectron spectroscopy indicate that protons shuttle back and forth between different monoclinic phases. The results offer a simple way to achieve the high performance of MoO3 in a diluted acidic solution.

Facile synthesis of near-infrared responsive on-demand oxygen releasing nanoplatform for precise MRI-guided theranostics of hypoxia-induced tumor chemoresistance and metastasis in triple negative breast cancer

BackgroundHypoxia is an important factor that contributes to chemoresistance and metastasis in triple negative breast cancer (TNBC), and alleviating hypoxia microenvironment can enhance the anti-tumor efficacy and also inhibit tumor invasion.MethodsA near-infrared (NIR) responsive on-demand oxygen releasing nanoplatform (O2-PPSiI) was successfully synthesized by a two-stage self-assembly process to overcome the hypoxia-induced tumor chemoresistance and metastasis. We embedded drug-loaded poly (lactic-co-glycolic acid) cores into an ultrathin silica shell attached with paramagnetic Gd-DTPA to develop a Magnetic Resonance Imaging (MRI)-guided NIR-responsive on-demand drug releasing nanosystem, where indocyanine green was used as a photothermal converter to trigger the oxygen and drug release under NIR irradiation.ResultsThe near-infrared responsive on-demand oxygen releasing nanoplatform O2-PPSiI was chemically synthesized in this study by a two-stage self-assembly process, which could deliver oxygen and release it under NIR irradiation to relieve hypoxia, improving the therapeutic effect of chemotherapy and suppressed tumor metastasis. This smart design achieves the following advantages: (i) the O2 in this nanosystem can be precisely released by an NIR-responsive silica shell rupture; (ii) the dynamic biodistribution process of O2-PPSiI was monitored in real-time and quantitatively analyzed via sensitive MR imaging of the tumor; (iii) O2-PPSiI could alleviate tumor hypoxia by releasing O2 within the tumor upon NIR laser excitation; (iv) The migration and invasion abilities of the TNBC tumor were weakened by inhibiting the process of EMT as a result of the synergistic therapy of NIR-triggered O2-PPSiI.ConclusionsOur work proposes a smart tactic guided by MRI and presents a valid approach for the reasonable design of NIR-responsive on-demand drug-releasing nanomedicine systems for precise theranostics in TNBC.Graphical

Nickel Phosphide Coated with Ultrathin Nitrogen-Doped Carbon Shell as a Highly Durable and Active Catalyst towards Hydrogen Evolution Reaction.

Developing non-precious metal catalysts towards hydrogen evolution reaction (HER) is of both high scientific and technical importance for the widespread application of water electrolysis. Herein, Ni2 P nanoparticles coated with a ultrathin N-doped carbon shell were prepared as a highly efficient HER catalyst. Ni2 P@CN exhibits both enhanced catalytic activity and durability in comparison with the carbon-supported Ni2 P counterpart, and represents 100% faradaic yield for HER in an acidic medium. The improved charge transfer of N-doped graphitic carbon shells contributes to the increase in activity. Meanwhile, the carbon shells suppress the aggregation and exfoliation of Ni2 P nanoparticles. As a result, the synergistic role of the N-doped carbon layer confers the Ni2 P cores with boosted activity and stability.

Numerical simulation of deployable ultra-thin composite shell structures for space applications and comparison with experiments

In the present article, the geometrical nonlinear behavior of deployable booms undergoing large displacements and rotations is investigated. The triangular rollable and collapsible boom made of fiber-reinforced composite materials is considered along with a metallic tape spring. The mathematical model makes use of higher-order 1D structural theories based on the Carrera unified formulation, which allows the description of moderate nonlinearities to deep post-buckling mechanics of ultra-thin shells in a hierarchical and scalable manner. Particular attention is focused on the study of equilibrium paths of the booms subjected to coiling bending. Dedicated experimental tests reveal the validity of the proposed finite element approach, whereas the investigation of different lamination sequences offer a valuable perspective for possible future designs.

Non-Stacked γ-Fe2O3/C@TiO2 Double-Layer Hollow Nanoparticles for Enhanced Photocatalytic Applications under Visible Light.

Herein, a non-stacked γ-Fe2O3/C@TiO2 double-layer hollow nano photocatalyst has been developed with ultrathin nanosheets-assembled double shells for photodegradation phenol. High catalytic performance was found that the phenol could be completely degraded in 135 min under visible light, due to the moderate band edge position (VB at 0.59 eV and CB at −0.66 eV) of the non-stacked γ-Fe2O3/C@TiO2, which can expand the excitation wavelength range into the visible light region and produce a high concentration of free radicals (such as ·OH, ·O2−, holes). Furthermore, the interior of the hollow composite γ-Fe2O3 is responsible for charge generation, and the carbon matrix facilitates charge transfer to the external TiO2 shell. This overlap improved the selection/utilization efficiency, while the unique non-stacked double-layered structure inhibited initial charge recombination over the photocatalysts. This work provides new approaches for photocatalytic applications with γ-Fe2O3/C-based materials.

Controllable synthesis of a hollow Cr2O3 electrocatalyst for enhanced nitrogen reduction toward ammonia synthesis

A facile template-assisted approach is proposed for the construction of a hollow Cr 2 O 3 catalyst with a small size and ultrathin shell. The as-prepared catalyst displays excellent activity toward nitrogen reduction for ammonia production. As a fascinating alternative to the energy-intensive Haber-Bosch process, the electrochemically-driven N 2 reduction reaction (NRR) utilizing the N 2 and H 2 O for the production of NH 3 has received enormous attention. The development and preparation of promising electrocatalysts are requisite to realize an efficient N 2 conversion for NH 3 production. In this research, we propose a template-assisted strategy to construct the hollow electrocatalyst with controllable morphology. As a paradigm, the hollow Cr 2 O 3 nanocatalyst with a uniform size (∼170 nm), small cavity and ultrathin shell (∼15 nm) is successfully fabricated with this strategy. This promising hollow structure is favourable to trap N 2 into the cavity, provides abundant active sites to accelerate the three-phase interactions, and facilitates the reactant transfer across the shell. Attributed to these synergetic effects, the designed catalyst displays an outstanding behaviour in N 2 fixation for NH 3 production in ambient condition. In the neutral electrolyte of 0.1 mol·L −1 Na 2 SO 4 , an impressive electrocatalytic performance with the NH 3 generation rate of 2.72 μg·h −1 ·cm −2 and a high FE of 5.31% is acquired respectively at −0.85 V with the hollow Cr 2 O 3 catalyst. Inspired by this work, it is highly expected that this approach could be applied as a universal strategy and extended to fabricating other promising electrocatalysts for realizing highly efficient nitrogen reduction reaction (NRR).

(Plasmonic gold core)@(ultrathin ruthenium shell) nanostructures as antenna-reactor photocatalysts toward nitrogen photofixation.

Ruthenium (Ru) is known as the optimal metal catalyst for ammonia (NH3) synthesis, but the poor light-harvesting capability restricts its application in photocatalysis. Herein, we construct an antenna-reactor nanostructure through the controllable growth of an ultrathin Ru nanocluster shell with desired catalytic activity on the plasmonic gold (Au) nanoantennas. In this nanostructure, Au nanoantennas interact strongly with light to generate hot carriers, meanwhile Ru nanoclusters adsorb and activate N2, leading to the reduction of N2 to NH3 by the generated hot electrons. This antenna-reactor plasmonic photocatalyst exhibits shell-thickness-dependent photocatalytic activity toward nitrogen (N2) photofixation under visible and near-infrared light illumination.

Unveiling the advantages of an ultrathin N-doped carbon shell on self-supported tungsten phosphide nanowire arrays for the hydrogen evolution reaction experimentally and theoretically.

Packaging electrocatalysts with carbon shells offers an opportunity to develop stable and effective hydrogen evolution reaction (HER) materials. Here, an ultrathin N-doped carbon-coated self-supported WP nanowire array (WP@NC NA) hybrid has been synthesized. Owing to the encapsulation of the ultrathin N-doped carbon shell on the WP surface, the as-prepared WP@NC NA hybrid exhibits enhanced physicochemical stability, more active sites, and superior conductivity compared with WP NA without carbon coating. Besides, density functional theory calculations demonstrate that the carbon shell can optimize the hydrogen adsorption step in the acidic HER, and simultaneously facilitate water physical adsorption, water dissociation, and hydroxyl group desorption steps during the alkaline HER. These findings demonstrate the intrinsic mechanism of how a carbon shell promotes the acidic and alkaline HER kinetics, and provide scientific guidance for the packaging design of promising carbon-encapsulating self-supported electrocatalysts.

Palladium cubes with Pt shell deposition for localized surface plasmon resonance enhanced photodynamic and photothermal therapy of hypoxic tumors.

Multifunctional phototherapy nanoagents for imaging-guided synergistic photothermal therapy (PTT) and photodynamic therapy (PDT) are highly desirable in the field of solid tumor therapy. Nevertheless, the tumor microenvironment (TME) inherently associated with hypoxia significantly hampers the photodynamic effect of these multifunctional nanoagents. Herein, Pd nanocubes coated with an ultrathin Pt shell were prepared and further conjugated with fluorescein labeled and thiol functionalized polyethylene glycol (FITC-PEG-SH) (denoted as Pd@Pt-PEG). The deposition of a Pt shell on Pd nanocubes not only enhances the photothermal performance, exhibiting excellent hyperthermia outcomes and impressive photothermal (PT) imaging quality, but also leads to the formation of singlet oxygen (1O2) induced by plasmonic excitation. In the meantime, the catalytic activity of the Pt layer is enhanced by electronic coupling and the plasmonic effect, which induces the decomposition of endogenous overexpressed hydrogen peroxide (H2O2) in tumors to generate O2 for conquering TME and augmenting 1O2 generation for efficacious tumor cell apoptosis. The modification of FITC-PEG-SH improves the biocompatibility and provides outstanding fluorescence (FL) imaging properties. Upon NIR laser irradiation, Pd@Pt-PEG allows in situ O2 generation and dual-mode imaging-guided synergistic PTT/PDT that effectively kills hypoxic tumor cells, which makes it a promising nanotherapeutic agent for enhanced tumor therapy.

Core-Shell Structured Fe-N-C Nanocatalyst Wrapped by Ultrathin Porous Carbon Shell as a Robust Electrocatalyst for Oxygen Reduction Reaction

Core-Shell Structured Fe-N-C Nanocatalyst Wrapped by Ultrathin Porous Carbon Shell as a Robust Electrocatalyst for Oxygen Reduction Reaction