Sandwich-like Nanostructures Research Articles

Black Phosphorus-Tungsten Oxide Sandwich-like Nanostructures for Highly Selective NO2 Detection.

Modern chemical production processes often emit complex mixtures of gases, including hazardous pollutants such as NO2. Although widely used, gas sensors based on metal oxide semiconductors such as WO3 respond to a wide range of interfering gases other than NO2. Consequently, developing WO3 gas sensors with high NO2 selectivity is challenging. In this study, a simple one-step hydrothermal method was used to prepare WO3 nanorods modified with black phosphorus (BP) flakes as sensitive materials for NO2 sensing, and BP-WO3-based micro-electromechanical system gas sensors were fabricated. The characterization of the as-prepared BP-WO3 composite through X-ray diffraction scanning electron microscopy and X-ray photoelectron spectroscopy confirmed the successful formation of the sandwich-like nanostructures. The result of gas-sensing tests with 2-14 ppm NO2 indicated that the sensor response was 1.25-2.21 with response-recovery times of 36 and 36 s, respectively, at 190 °C. In contrast to pure WO3, which exhibited a response of 1.07-2.2 to 0.3-5 ppm H2S at 160 °C, BP-WO3 showed almost no response to H2S. Thus, compared with pure WO3, BP-WO3 exhibited significantly improved NO2 selectivity. Overall, the BP-WO3 composite with sandwich-like nanostructures is a promising material for developing highly selective NO2 sensors for practical applications.

MoS2/NiSe2/rGO Multiple-Interfaced Sandwich-like Nanostructures as Efficient Electrocatalysts for Overall Water Splitting

Constructing a heterogeneous interface using different components is one of the effective measures to achieve the bifunctionality of nanocatalysts, while synergistic interactions between multiple interfaces can further optimize the performance of single-interface nanocatalysts. The non-precious metal nanocatalysts MoS2/NiSe2/reduced graphene oxide (rGO) bilayer sandwich-like nanostructure with multiple well-defined interfaces is prepared by a simple hydrothermal method. MoS2 and rGO are layered nanostructures with clear boundaries, and the NiSe2 nanoparticles with uniform size are sandwiched between both layered nanostructures. This multiple-interfaced sandwich-like nanostructure is prominent in catalytic water splitting with low overpotential for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and almost no degradation in performance after a 20 h long-term reaction. In order to simulate the actual overall water splitting process, the prepared nanostructures are assembled into MoS2/NiSe2/rGO||MoS2/NiSe2/rGO modified two-electrode system, whose overpotential is only 1.52 mV, even exceeded that of noble metal nanocatalyst (Pt/C||RuO2~1.63 mV). This work provides a feasible idea for constructing multi-interface bifunctional electrocatalysts using nanoparticle-doped bilayer-like nanostructures.

Super-thin LiV3O8 nanosheets/graphene sandwich-like nanostructures with ultrahigh lithium ion storage properties

With the thickness less than 5 nm, super-thin LiV3O8 nanosheets have already been successfully synthesized by transformation from super-thin V2O5·xH2O nanosheets, moreover, super-thin LiV3O8 nanosheets@graphene (LVO/G) sandwich-like layer-by-layer nanostructures were successfully obtained via a facile self-assembly method and annealing treatment. Such interesting LVO/G nanostructures as cathodes for lithium ion batteries not only show high capacity up to 397.2 mA h g−1 and outstanding rate capabilities (171 mA h g−1 at 10 C, 112 mA h g−1 at 15 C), but also present super-long cycle performance (301.2 mA h g−1 after 500 cycles at 1 C). As far as we known, the LVO/G cathodes exhibit ultrahigh lithium storage performances even much higher than those of previously reported literatures of LiV3O8, which demonstrates that such sandwich-like layer-by-layer LVO/G nanostructures is a potential candidate cathode material for the next generation of batteries.

Enhancing Photocatalytic Activity on (MnO@TNTAs):Mn2+ with a Hierarchical Sandwich-Like Nanostructure via a Two-Step Procedure

Several semiconductor nanomaterial devices are increasingly being applied in a variety of fields, especially in the treating of environmental pollutants. We have fabricated (MnO@TNTAs):Mn2+ with sandwich-like nanostructures composed of TiO2 nanotube arrays (TNTAs), Mn-doped TNTAs and MnO. The experimental procedure was a two-step synthesis: first, using anodic oxidation methods and then hydrothermal methods. We carried out many characterizations of the “sandwiches“ in the nanoscale. From the field emission scanning electron microscopy images we found nanofibers lying on the highly-ordered nanotube arrays. The diameter of the nanotubes was about 50 nm but the size of the nanofibers varied. Energy dispersive spectroscopy demonstrated that the nanofibers contained a manganese element and x-ray diffraction patterns showed the peak of the manganosite phase. From ultraviolet–visible light spectra, it was found that the nanostructures had strong absorption activities under both ultraviolet and visible light radiation, while pure TNTAs had absorption only under ultraviolet light. The photodegradation experiments proved that the sandwich-like nanostructures had an excellent photocatalytic activity (92.5% after 240 min), which was a great improvement compared with pure TNTAs. In this way, the structures as a device at the nanoscale have a huge potential in controlling environmental pollution.

CoO-Co3O4 heterostructure nanoribbon/RGO sandwich-like composites as anode materials for high performance lithium-ion batteries

CoO-Co3O4 heterostructure nanoribbons were successfully sandwiched between reduced graphene oxide (RGO) nanosheets through a facile solvothermal method and sintering process, which used directly as the anode material for lithium ion batteries. The as-prepared ultrathin CoO-Co3O4 nanoribbon/RGO sandwich-like nanostructures (CoO-Co3O4-RGO) delivers a reversible capacity of 994mAhg−1 at a current density of 100mAg−1 after 200 cycles. Even at a high charge-discharge rate of 1000mAg−1, CoO-Co3O4-RGO still demonstrate a reversible capacity of 395mAhg−1 after 500 cycles. The rate capability of CoO-Co3O4-RGO evaluated by the ratio of capacity at 100, 200, 500, 1000, 2000, 5000 and 100mAg−1 after each 10 cycles was about 1210, 1060, 890, 730, 578, 392 and 915mAhg−1, respectively. The greatly enhanced performances for CoO-Co3O4-RGO may be ascribed to the synergistic effects: The multicomponent generates hybridizing advantages; The mutual influence of both CoO-Co3O4 nanoribbons and RGO nanosheets decreases the aggregation; The two-dimensional (2D) nanoribbons with the short lithium ion diffusion and 2D RGO sheets as conductive network built an efficient three dimensional (3D) storage active material.

Boronic acid functionalized magnetic composites with sandwich-like nanostructures as a novel matrix for PDGF detection

In this paper, we present a novel multifunctional magnetic composite with sandwich-like nanostructure, which is composed of a yolk-egg-like magnetic silica core and a continuous polydopamine(PDA)-Au coating. Firstly, yolk-egg-like magnetic composite(SiO2@Fe3O4@PDA) was prepared by a combined high temperature decomposition method with mussel chemistry. Then, Au nanoparticles(NPs) were in-situ generated on the surface of the SiO2@Fe3O4@PDA by reaction between the PDA shell and HAuCl4, forming a multilayer sandwich-like nanostructure. Benefiting from the good affinity of the PDA shell and Au NPs with thiol group, the 4-mercaptophenylboronic acid was successfully assembled on the surface of Au NPs and PDA layer. The hybrid magnetic composite functionalized with boronic acid was used as affinity probes to selectively capture PDGF from solution. Meanwhile, methylene blue(MB)-doped silica NPs (SiO2-MB) were prepared to immobilize aptamer. In the presence of PDGF, the aptamer labeled SiO2-MB (SiO2-MB-aptamer) specifically bound with the PDGF protein. By monitoring the change of the electrochemical signal of MB, we were able to detect the binding events between the aptamer and PDGF in homogeneous solutions. The sensor was highly selective and sensitive with a detection limit of 0.22 fM for PDGF. The developed method showed wide potential applications in protein monitoring and cancer diagnosis.

Na0.33V2O5 nanosheet@graphene composites: Towards high performance cathode materials for sodium ion batteries

Na0.33V2O5 nanosheet@graphene composites were explored as cathodes for sodium ion batteries for the first time. Here, Na0.33V2O5 nanosheet@graphene composites with special sandwich-like nanostructures were synthesized. The composites exhibit high discharge capacity (of ca. 213mAhg−1 at 20mAg−1), good cycling stability (with a capacity retention of 83.3% at 50mAg−1 after 100 cycles) and desirable rate performance (88.2mAhg−1 at an extremely high current density of 6000mAg−1) as cathodes for sodium storage. Notably, the as-synthesized Na0.33V2O5 nanosheet@graphene composites show much higher specific capacity and better rate capability than those reported Na0.33V2O5 materials which were usually tested at relatively low currents (no more than 200mAg−1) and showed low capacities (less than 150mAhg−1).

Facile Synthesis of Na0.33V2O5 Nanosheet-Graphene Hybrids as Ultrahigh Performance Cathode Materials for Lithium Ion Batteries.

Na0.33V2O5 nanosheet-graphene hybrids were successfully fabricated for the first time via a two-step route involving a novel hydrothermal method and a freeze-drying technique. Uniform Na0.33V2O5 nanosheets with a thickness of about 30 nm are well-dispersed between graphene layers. The special sandwich-like nanostructures endow the hybrids with high discharge capacity, good cycling stability, and superior rate performance as cathodes for lithium storage. Desirable discharge capacities of 313, 232, 159, and 108 mA·h·g(-1) can be delivered at 0.3, 3, 6, and 9 A·g(-1), respectively. Moreover, the Na0.33V2O5-graphene hybrids can maintain a high discharge capacity of 199 mA·h·g(-1) after 400 cycles even at an extremely high current density of 4.5 A·g(-1), with an average fading rate of 0.03% per cycle.

Ultrathin Li3VO4 nanoribbon/graphene sandwich-like nanostructures with ultrahigh lithium ion storage properties

Two-dimensional (2D) “graphene-like” inorganic materials, because of the short lithium ion diffusion path and unique 2D carrier pathways, become a new research focus of the lithium storages. Some “graphene-like” binary compounds, such as, MnO2, MoS2 and VO2 ultrathin nanosheets, have been synthesized by the peeling method, which also exhibit enhanced lithium storage performances. However, it still remains a great challenge to synthesize widely-used lithium-containing ternary oxides with “graphene-like” nanostructures, because the lithium-containing ternary oxides, unlike ternary layered double hydroxides (LDH), are very hard to be directly peeled. Herein, we successfully synthesized ultrathin Li3VO4 nanoribbons with a thickness of about 3nm by transformation from ultrathin V2O5·xH2O nanoribbons, moreover, we achieved the preparation of ultrathin Li3VO4 nanoribbon@graphene sandwich-like nanostructures (LVO/G) through the layer-by-layer assembly method. The unique sandwich-like nanostructures shows not only a high specific reversible capacitance (up to 452.5mAhg−1 after 200 cycles) but also an excellent cycling performance (with more than 299.2mAhg−1 of the capacity at 10C after 1000 cycles) as well as very high rate capability. Such template strategy, using “graphene-like” binary inorganic nanosheets as templates to synthesize lithium-containing ternary oxide nanosheets, may be extended to prepare other ternary oxides with “graphene-like” nanostructures.

Design of Pd/PANI/Pd Sandwich-Structured Nanotube Array Catalysts with Special Shape Effects and Synergistic Effects for Ethanol Electrooxidation

Low cost, high activity, and long-term durability are the main requirements for commercializing fuel cell electrocatalysts. Despite tremendous efforts, developing non-Pt anode electrocatalysts with high activity and long-term durability at low cost remains a significant technical challenge. Here we report a new type of hybrid Pd/PANI/Pd sandwich-structured nanotube array (SNTA) to exploit shape effects and synergistic effects of Pd-PANI composites for the oxidation of small organic molecules for direct alcohol fuel cells. These synthesized Pd/PANI/Pd SNTAs exhibit significantly improved electrocatalytic activity and durability compared with Pd NTAs and commercial Pd/C catalysts. The unique SNTAs provide fast transport and short diffusion paths for electroactive species and high utilization rate of catalysts. Besides the merits of nanotube arrays, the improved electrocatalytic activity and durability are especially attributed to the special Pd/PANI/Pd sandwich-like nanostructures, which results in electron delocalization between Pd d orbitals and PANI π-conjugated ligands and in electron transfer from Pd to PANI.

Self-Healing Anticorrosion Coatings Based on pH-Sensitive Polyelectrolyte/Inhibitor Sandwichlike Nanostructures.

An anticorrosion layer of a smart polymer coating is developed. The nature and properties of the coating simultaneously provide three mechanisms of corrosion protection: passivation of the metal degradation by controlled release of an inhibitor, buffering of pH changes at the corrosive area by polyelectrolyte layers, and self-curing of the film defects due to the mobility of the polyelectrolyte constituents in the layer-by-layer assembly.

Multifunctional Magnetic Silver Nanoshells with Sandwichlike Nanostructures

We present a novel multifunctional magnetic Ag nanoshell with sandwichlike nanostructure, which is composed of a yolk−egg-like magnetic silica core and a continuous Ag nanoshell coating. First, yolk−egg-like magnetic silica was prepared by a facile one-step sol−gel method to embed the magnetic nanoparticles at the boundary between inner silica spherical core and outer silica shell. Then Ag nanoshells were coated by electroless plating method, forming a multiplayer sandwichlike nanostructure. The plasmon resonance peaks can shift across a wide wavelength range by tuning the Ag shell coverage and thickness. The magnetic Ag nanoshells fuse the broad NIR absorption property and superparamagnetic property into one particle, possessing promising biomedical applications such as magnetic-field targeted photothermal therapy agents and multimodal molecular probes.

Fabrication of the stable adduct CdS/CTAB/Clay with sandwich-like nanostructures

The ordered multilayer adducts have been synthesized by electrostatic self-assembly between exfoliated sodium montmorillonite nanoplatelets and substituted CdS/CTAB cationic polyelectrolytes, in which sodium montmorillonite particles are exfoliated by means of extensive swelling and CdS/CTAB polyelectrolytes are obtained by sonicating CdS nanoparticles in CTAB water suspension. The build-up of the stable adducts with sandwich-like nanostructures has been demonstrated by X-ray diffraction (XRD) pattern. TEM cross-sectional images indicate that the nanocomposites are aligned parallel to form ordered structures. And UV–Vis and PL spectra show the presence of the inorganic functional components. It may be predicted that this self-assembly technique can be generalized to prepare other sandwich-like nanocomposites with desired optical, electro-optical, electronic, catalytic and magnetic properties.