Heterostructure Nanocomposites Research Articles

Room-temperature self-powered ethanol sensor based on the piezo-surface coupling effect of heterostructured α-Fe2O3/ZnO nanowires

At room temperature, high sensitivity for detecting ethanol has been achieved from α-Fe2O3/ZnO nanowire piezo-nanogenerator as self-powered gas sensor. Such ethanol sensing can be ascribed to piezo-surface coupling effect of the heterostructured nanocomposites. The results demonstrate a novel approach for room-temperature ethanol sensors and promote the development of self-powered sensing.

Harvesting Nanocatalytic Heat Localized in Nanoalloy Catalyst as a Heat Source in a Nanocomposite Thin Film Thermoelectric Device.

This report describes findings of an investigation of harvesting nanocatalytic heat localized in a nanoalloy catalyst layer as a heat source in a nanocomposite thin film thermoelectric device for thermoelectric energy conversion. This device couples a heterostructured copper-zinc sulfide nanocomposite for thermoelectrics and low-temperature combustion of methanol fuels over a platinum-cobalt nanoalloy catalyst for producing heat localized in the nanocatalyst layer. The possibility of tuning nanocatalytic heat in the nanocatalyst and thin film thermoelectric properties by compositions points to a promising pathway in thermoelectric energy conversion.

Enhanced ultraviolet photocatalytic activity of Ag/ZnO nanoparticles synthesized by modified polymer-network gel method

Ag/ZnO nanoparticle (NP) heterostructures are synthesized through a modified polymer-network gel method in which glucose is added to the precursor solution to prevent the gel from drastically shrinking during drying of the aqueous solution. Structural and optical properties of the samples are characterized by a range of techniques including XRD, SEM, TEM, XPS, UV–Vis, and PL. The high-quality Ag-ZnO heterostructure is evidenced clearly by high-resolution TEM. The Ag/ZnO heterostructure nanocomposites exhibit a higher photocatalytic activity in the degradation of methyl orange than pure ZnO. Especially, Ag/ZnO NP heterostructures with the Ag/Zn molar ratio of 5:95 (sample ZA-5) show the highest degradation efficiency, which is 11 times higher compared with pure ZnO. The photoluminescence properties of the heterostructures and O defect states are studied to well explain the observed photocatalytic effects. ZA-5 also exhibits competitive photocatalytic activity for the degradation of other pollutant dyes such as Methylene blue and Rhodamine B compared with the recently reported techniques, while showing excellent catalyst photostability as well as offering simplicity and reliability.

Hierarchical Assembly of SnO2/ZnO Nanostructures for Enhanced Photocatalytic Performance.

SnO2/ZnO hierarchical heterostructures have been successfully synthesized by combining electrospinning technique and hydrothermal method. Various morphologies of the secondary ZnO nanostructures including nanorods (NRs) and nanosheets (NSs) can be tailored by adding surfactants. Photocatalytic performance of the heterostructures was investigated and obvious enhancement was demonstrated in degradation of the organic pollutant, compared to the primary SnO2-based nanofibers (NFs) and bare ZnO. Furthermore, it was found that the H2 evolution from water splitting was achieved by photocatalysis of heterostructured nanocomposites after sulfurization treatment. This synthetic methodology described herein promises to be an effective approach for fabricating variety of nanostructures for enhanced catalytic applications. The heterostructured nanomaterials have considerable potential to address the environmental and energy issues via degradation of pollutant and generation of clean H2 fuel.

Ultrasonic synthesis of high fluorescent C-dots and modified with CuWO4 nanocomposite for effective photocatalytic activity

High fluorescent C-dots were synthesized from dextrose via facile ultrasonic wave assisted reaction. Carbon dots (C-dots)/Copper tungstate (CuWO4) heterostructure has been prepared via a facile reflux approach. The novel C-dots/CuWO4 photocatalyst were characterized by using transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, UV–vis, photoluminescence and X-ray photoelectron spectroscopy. The photocatalytic property of heterostructure nanocomposite has also been investigated by using rhodamine B as a model organic pollutant. The obtained results revealed that as prepared C-dots are predominately multilayer graphene oxide with luminance properties. After incorporation of C-dots onto the CuWO4, it contributes to the improvement of charge separation and reduction of charge recombination and thereby enhancing the photocatalytic property, respectively. The C-dots in the nanocomposites can efficiently trap electrons, thus hindering the recombination of photogenerated electrons and holes. The heterostructure nanocomposite with 5.0 wt% C-dots shows the highest photocatalytic activity, which is about three times as that of pure CuWO4.

Visible light photocatalytic behavior of manganese carbonate/titanium dioxide nanocomposites based on photoinduced interfacial charge transfer

Here, a novel visible-light-driven photocatalyst MnCO3/TiO2 heterostructure nanocomposite has been prepared via a precipitation method. The synthesized MnCO3/TiO2 exhibited superior activity for the degradation of propylene under visible light compared to bare P25 TiO2 and pure MnCO3. This high visible light activity is due to the interfacial charge transfer (IFCT) from the MnCO3 to the conduction band of TiO2. After repeated cycles of photo-oxidation of propylene, the photocatalytic behavior of MnCO3/TiO2 exhibited no loss of activity. This work provides new perspective to fabricate visible-light-active photocatalyst by use of IFCT effect between carbonate and semiconductor.

Microwave Absorption Properties of Polyester Composites Incorporated with Heterostructure Nanofillers with Carbon Nanotubes as Carriers**Supported by the National Natural Science Foundation of China under Grant No 10332020.

Carbonaceous nanomaterials such as carbon nanotubes (CNTs), magnetic metal nanomaterials and semiconductor nanomaterials are superior candidates for microwave absorbers. Taking full advantage of the features of CNTs, nanophase cobalt and nanophase zinc oxide, whose main microwave absorption mechanisms are based on resistance loss, magnetic loss and dielectric loss, we fabricate CNT/Co and CNT/ZnO heterostructure nanocomposites, respectively. By using the CNTs, CNT/Co nanocomposites and CNT/ZnO nanocomposites as nanofillers, composites with polyester as matrix are prepared by in situ polymerization, and their microwave absorption performance is studied. It is indicated that the synergetic effects of the physic properties of different components in nano-heterostructures result in greatly enhanced microwave absorption performance in a wide frequency range. The absorption peak is increased, the absorption bandwidth is broadened, and the maximum peak shifts to a lower frequency.

Functionalization of Smart Gels with Beta-Cyclodextrin and Release Characteristics to Simulating Drugs

Smart gels have many applications in sensors, actuators, shape memory intelligent devices, recognition, self-healing, drug release, biomimetic soft robot design, biomimetic tactile, neural regeneration, biomimetic membranes, supercapacitor, dye-sensitized solar cells, advanced lithium polymer batteries, environmental fields, biomedical fields, et al. And that cyclodextrins are one of the typical macrocycles with good recognition ability, and endowed with fascinating hydrophobic cavities and hydrophilic surface, which enable the encapsulation of diverse small organic molecules by forming inclusion complexes. In this paper, grafted copolymerization between acrylic acid and N,N-dimethyl acrylamide in the presence of water-soluble cyclodextrins was carried out. The effect of ratio of copolymerization monomer on the grafted polymer was examined. The results indicated that self-crosslinking smart gel with multi-stimuli responsive was obtained by selecting suitable the ratio of copolymerization monomer, its behaviors of swelling/shrinking were examined. The adsorption properties and releasing characteristics of smart gel were performed with simulating drugs. Some meaningful results were obtained. These series grafted copolymer would also be used to modify the surface and interface properties of low-dimensional functional materials or heterostructured nanocomposites for intelligent organic-inorganic functional nanocomposites, some good results were obtained.

Enhanced optical properties of heterostructured ZnO/CeO2 nanocomposite fabricated by one-pot hydrothermal method: Fluorescence and ultraviolet absorption and visible light transparency

Many researchers investigated the properties of either discrete metal oxide CeO2 or ZnO materials. However, less attention has been paid to the various nanostructure and performances of CeO2 and ZnO nanocomposite up to now. In this paper, a facile and low cost one-pot hydrothermal synthesis method has been adopted to obtained directly precursors of CeCO3OH and Zn5(CO3)2(OH)6 with different Ce atom molar ratios to Zn, which are transformed into their corresponding metal oxide to form the ZnO/CeO2 heterostructure nanocomposites (HSNCs) by pyrolysis. The heterostructure is composed of ZnO and CeO2 monocrystals, simultaneously, CeO2 monocrystals are well dispersed on the surface of ZnO monocrystal for cosmetics. Bing dependent on the analysis results of XRD and TEM for the obtained precursors before and after pyrolysis, the formation mechanism of HSNCs was proposed. To the best of our knowledge, the paper first reported heterostructured ZnO/CeO2 nanocomposite grown in one-pot mixed aqueous solution of cerium nitrate, zinc acetate and urea without other extra surfactant. Additionally, the influence of various Ce/Zn molar ratios on the heterostructure, fluorescence emission and UV–visible absorption properties of HSNCs was investigated in detail. ZnO/CeO2 HSNCs display higher fluorescence emission with the increasing Ce/Zn molar ratio. Meanwhile, the larger Ce/Zn molar ratio of ZnO/CeO2 HSNCs, the stronger transparency in the visible light region and the weaker UV absorption. The results are due to the fact that the band gap of ZnO/CeO2 HSNCs will decrease from 3.25 to 3.08eV when Ce/Zn atom molar ratio is increased from 0 to 0.08. By the comprehensive analysis on the optical performances of HSNCs with the different Ce/Zn atom molar ratios, ZnO/CeO2-0.04 HSNCs could become UV absorber materials and transparent material in the visible region. ZnO/CeO2-0.04 HSNCs with the UV-filtering and Vis-transparent properties is appropriate for personal-care cosmetics.

The study on the geometry and electronic properties of (WO3)x/(TiO2)y heterostructure by using the layered structural model

The layered structural model was proposed to study the geometry and electronic properties of the ( WO 3)x/( TiO 2)y heterostructures in this paper. The geometry and electronic properties were affected greatly by the relative proportion of TiO 2 and WO 3 in the nanocomposites. The minimum band gap of ( WO 3)x/( TiO 2)y heterostructures decreased with the proportion of WO 3 increasing but increased with the proportion of TiO 2 increasing. Interestingly, electrons at the upper valence band (VB) can be directly excited from 2p and 3d orbitals of titania to the conduction band (CB), which was mainly consisted of 5d orbitals of tungsten trioxide. The effective electron mass of ( WO 3)x/( TiO 2)y heterostructures was higher than that of pure TiO 2. It indicated that the electron–hole recombination rate of hybrid ( WO 3)x/( TiO 2)y heterostructure was lower than that of pure TiO 2, which might imply that photocatalytic activities of the hybrid ( WO 3)x/( TiO 2)y heterostructures were enhanced under visible light irradiation. The theoretical results might offer a new useful guide for designing semiconductors photocatalyst, such as heterostructure nanocomposites.

In situ synthesis of Ag@Ag3PO4/MWCNT triples hetero-photocatalyst for degradation of malachite green

The Ag@Ag3PO4/MWCNT triple heterostructure nanocomposites were facilely fabricated by an in-situ reduction method. The multi-walled carbon nanotube (MWCNT) was fully enwrapped by Ag@Ag3PO4 nanocrystals with an average diameter of 200nm. Ag@Ag3PO4/MWCNT hetero-photocatalyst showed strong absorbance in the visible regions. Compared with Ag@Ag3PO4, Ag@Ag3PO4/MWCNT hetero-photocatalyst exhibited significantly higher photocatalytic activities under the irradiation of visible light for the photodegradation of malachite green (MG), as the MWCNT could facilitate charge transfer and suppress the recombination of electron–hole pairs. This study provided an invaluable methodology for designing and fabrication of highly efficient visible-light-driven photocatalysts for catalytic and new energy applications.

Colloidal Polymers via Dipolar Assembly of Magnetic Nanoparticle Monomers

In this Spotlight on Applications, we describe our recent progress in the preparation of hierarchical one-dimensional (1-D) materials constructed from polymer-coated ferromagnetic cobalt nanoparticles. We begin with a general discussion of nanoparticles capable of 1-D self-organization to form 1-D assemblies, which we term colloidal polymers. The need for efficient, highly directional interactions prompted our investigation with polymer-coated ferromagnetic nanoparticles, which spontaneously form linear assemblies through coupling of north and south magnetic poles present in these single-domain ferromagnetic nanoparticles. These highly directional N-S interactions and the resulting formation of 1-D assemblies can be understood in the context of traditional polymer-forming reactions. The dipolar assembly of these ferromagnetic nanoparticles into chains and binary assemblies while dispersed in organic media has been investigated as a key foundation to form novel magnetic materials and heterostructured nanocomposites. These studies enabled the fabrication of magnetic nanoactuating systems resembling "artificial cilia and flagella". We then discuss our recent efforts to prepare cobalt oxide nanowires using various nanoparticle conversion reactions through a process termed colloidal polymerization. A series of novel functional "colloidal monomers" based on dipolar cobalt nanoparticles were also prepared, incorporating noble metal or semiconductor nanoinclusions to form heterostructured cobalt oxide nanocomposites.

Enhanced photocatalytic degradation of methyl orange in TiO2(B)@anatase heterostructure nanocomposites prepared by a facile hydrothermal method

In this work, one-dimensional TiO2(B)@anatase heterostructure nanocomposites were synthesized via a facile hydrothermal process in ethanol/water solution with the aid of polyvinylpyrrolidone. TiO2(B) nanobelts were uniformly coated with an anatase nanocrystals shell. The shell thickness can be tuned from 10nm to 30nm. The energy bandgap at the heterostructure interface favors the transferring of the photo-induced holes in anatase to TiO2(B) nanobelts, thus the charge recombination can be effectively suppressed. The nanocomposites showed superior photocatalytic degradation of methyl orange due to the enhanced charge separation efficiency.

Surfactant‐Free Scalable Synthesis of Bi2Te3 and Bi2Se3 Nanoflakes and Enhanced Thermoelectric Properties of Their Nanocomposites (Adv. Mater. 10/2013)

Nanomaterial-based thermoelectric devices request scalable production and compositional tolerance for reliable device performance. On page 1425 Unyong Jeong and co-workers suggest a large-quantity synthesis of surfactant-free nanoflakes of Bi2Te3 and Bi2Se3. The chemical composition of the heterostructured nanocomposites is precisely controlled by mixing the nanoflake suspensions. A maximum ZT (0.7 at 400 K) is achieved with a broad content of 10–15% Bi2Se3 in the nanocomposites.

Fabrication of LiF/Fe/Graphene Nanocomposites As Cathode Material for Lithium-Ion Batteries

Homogeneous LiF/Fe/Graphene nanocomposites as cathode material for lithium ion batteries have been synthesized for the first time by a facile two-step strategy, which not only avoids the use of highly corrosive reagents and expensive precursors but also fully takes advantage of the excellent electronic conductivity of graphene. The capacity remains higher than 150 mA h g(-1) after 180 cylces, indicating high reversible capacity and stable cyclability. The ex situ XRD and HRTEM investigations on the cycled LiF/Fe/G nanocomposites confirm the formation of FeF(x) and the coexistence of LiF and FeF(x) at the charged state. Therefore, the heterostructure nanocomposites of LiF/Fe/Graphene with nano-LiF and ultrafine Fe homogeneously anchored on graphene sheets could open up a novel avenue for the application of iron fluorides as high-performance cathode materials for lithium-ion batteries.

Nonlinear resonant and high dielectric loss behavior of CdS∕α-Fe2O3 heterostructure nanocomposites

Cd S ∕ α - Fe 2 O 3 heterostructures, where the CdS nanorods grow irregularly on the side surface of α-Fe2O3 nanorods, were synthesized via a three-step process. The dielectric properties of the CdS∕α-Fe2O3 heterostructure nanocomposites have been investigated. The equivalent circuit model of the CdS∕α-Fe2O3 heterostructures was established, which reasonably explained the nonlinear dielectric resonant behavior of the CdS∕α-Fe2O3 heterostructure nanocomposites in the range of 5–15GHz. The high dielectric loss is mainly attributed to the conductance loss and the dipole relaxation loss in the CdS∕α-Fe2O3 heterostructures.

Catalysts for low-temperature methanol synthesis. Preparation of CuZnAl mixed oxides via hydrotalcite-like precursors

In the present study, a novel heterostructure nanocomposite consisting of hexagonal boron nitride (h-BN) and ZnTi layered double hydroxide was synthesized to remove two organic pollutants simultaneously from the aqueous solution under visible light irradiation at room temperature. ZnTi LDH/h-BN represents a cost-effective reusable material that showed both adsorption and substantial photocatalytic performance in the degradation of amaranth (AM) azo dye and diazepam (DZP) as organic contaminants of water. Various analyses were performed to assess the morphology, characteristic features, and synthesis accuracy of the as-prepared materials that proved the proper formation of the nanocomposite. Additionally, an acceptable reduction was observed in the bandgap of the nanocomposite in comparison with the bandgap of ZnTi LDH. Furthermore, the effect of various parameters, including pH of the solution, contaminant concentration, and catalyst dosage, were studied on the adsorption and photocatalytic activity to find out optimum conditions during the process. Results revealed that the synthesized catalysts had performed exceptionally well in adsorbing and degrading considered pollutants even in removing both from the same solution. The layered structure of the h-BN played a crucial role in providing an available surface area needed for adsorption and better dispersion of the photocatalyst particles, and at the same time, ZnTi LDH reduced AM and DZP by its photocatalytic activity. In the optimal conditions, the simultaneous removal efficiency of the molecule of AM and DZP was measured to be more than 99% and 95%, respectively.