Synthesis and optical properties of tetrapod-like zinc oxide nanorods

Two-dimensional Czochralski growth of single-crystal MoS2

Batch production of single-crystal two-dimensional (2D) transition metal dichalcogenides is one prerequisite for the fabrication of next-generation integrated circuits. Contemporary strategies for the wafer-scale high-quality crystallinity of 2D materials centre on merging unidirectionally aligned, differently sized domains. However, an imperfectly merged area with a translational lattice brings about a high defect density and low device uniformity, which restricts the application of the 2D materials. Here we establish a liquid-to-solid crystallization in 2D space that can rapidly grow a centimetre-scale single-crystal MoS2 domain with no grain boundaries. The large MoS2 single crystal obtained shows superb uniformity and high quality with an ultra-low defect density. A statistical analysis of field effect transistors fabricated from the MoS2 reveals a high device yield and minimal variation in mobility, positioning this FET as an advanced standard monolayer MoS2 device. This 2D Czochralski method has implications for fabricating high-quality and scalable 2D semiconductor materials and devices.

Synthesis of Zinc Oxide Nanorods from Zinc Borate Precursor and Characterization of Supercapacitor Properties

The synthesis of zinc oxide (ZnO) was accomplished from zinc borate (Zn3B2O6) minerals to be used as electrodes in supercapacitor applications. The concentrations of obtained zinc (Zn) metal after treatment with hydrochloric acid (HCl) were determined by atomic absorption spectroscopy (AAS). Direct synthesis of ZnO on a nickel (Ni) foam surface was conducted by employing the hydrothermal technique using a solution with the highest Zn content. The results showed the successful synthesis of ZnO nanorods on the surface of Ni foam with an average wall size of approximately 358 nm. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements revealed that the synthesized electrode exhibited battery-type charge storage characteristics, reaching a maximum specific capacitance of approximately 867 mF·cm-² at a current density of 2 mA·cm-². Additionally, the energy and power densities of the electrode at a current density of 2 mA·cm-² were calculated as 19.3 mWh·cm-² and 200 mW·cm-², respectively. These results exhibited promising performance of the single-component electrode, outperforming the existing counterparts reported in the literature.

Efficient Photothermal Elimination of Formaldehyde under Visible Light at Room Temperature by a MnOx-Modified Multi-Porous Carbon Sphere

Volatile organic compounds (VOCs) exert a serious impact on the environment and human health. The development of new technologies for the elimination of VOCs, especially those from non-industrial emission sources, such as indoor air pollution and other low-concentration VOCs exhaust gases, is essential for improving environmental quality and human health. In this study, a monolithic photothermocatalyst was prepared by stabilizing manganese oxide on multi-porous carbon spheres to facilitate the elimination of formaldehyde (HCHO). This catalyst exhibited excellent photothermal synergistic performance. Therefore, by harvesting only visible light, the catalyst could spontaneously heat up its surface to achieve a thermal catalytic oxidation state suitable for eliminating HCHO. We found that the surface temperature of the catalyst could reach to up 93.8 °C under visible light, achieving an 87.5% HCHO removal efficiency when the initial concentration of HCHO was 160 ppm. The microporous structure on the surface of the carbon spheres not only increased the specific surface area and loading capacity of manganese oxide but also increased their photothermal efficiency, allowing them to reach a temperature high enough for MnO_x to overcome the activation energy required for HCHO oxidation. The relevant catalyst characteristics were analyzed using XRD, measurement of BET surface area, scanning electron microscopy, HR-TEM, XPS, and DRS. Results obtained from a cyclic performance test indicated high stability and potential application of the MnO_x-modified multi-porous carbon sphere.

White light phosphorescence from ZnO nanoparticles for white LED applications

Point defect-mediated, reproducible, stable, and intense white phosphorescence from a single-phase solid has been reported for the first time.

High special surface area and "warm light" responsive ZnO: Synthesis mechanism, application and optimization

In this study, a new series of zinc oxide (ZnO) with high specific surface area and narrow energy band gap are prepared using a facile microwave-induced method. The corresponding formation mechanism is also discussed for the first time. Due to the introduction of C, these ZnO can be excited by long wave temperature light without harmful short wave radiation, and play an efficient photocatalytic activity. This valuable property fundamentally improves the biological safety of its photocatalytic application. Herein, taking teeth whitening as an example, the photocatalytic performance of ZnO is evaluated. The “pure” yellow light-emitting diode (PYLED) with high biological safety is used as the excitation source. It is found that this method could effectively remove pigment on the tooth surface through physical adsorption. In addition, these ZnO could generate active oxygen to degrade the pigment on the tooth surface under the irradiation of yellow light. Some further optimization of these “warm light” responsive ZnO is also discussed in this systematical study, which could open up new opportunities in biomedical field.

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A series of ZnO (PZCs, ZnO-BC) with high specific surface area and low band gap were synthesized by simple microwave-induced synthesis.

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The introduction of C or BC can effectively reduce the band gap of ZnO.

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Long wavelength warm light can effectively stimulate the photocatalytic activity of PZCs and ZnO-BC.

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Under the yellow light, ZnO can effectively decompose the pigment on the tooth surface.

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Warm light whitening, from the light source and material two levels to reduce the stimulation of teeth, and no obvious damage to enamel.

Effect of annealing on the defect-mediated blue phosphorescence in ZnO nanocrystals

Recently, UV/NUV excitable RGB phosphors with precisely tunable PL emission properties have been in high demand for their suitability in the fabrication of white LEDs. In this paper, we report to have tuned the PL intensity, shade, and color temperature of the defect-mediated blue phosphorescence of ZnO nanopowders by systematic annealing at different temperatures. The ZnO nanopowder was prepared by a facile and cost-effective aqueous solution-precipitation method. The as-synthesized nanopowder was annealed at different temperatures ranging from 150 °C to 850 °C and all these samples were characterized by XRD, FESEM, EDX, BET, Raman spectroscopy, and UV-Vis spectroscopy to have insight into their microstructural, compositional, and band-structure details. Optical studies of the samples were conducted by PL and τ-PL spectroscopy. Color coordinates of the samples were obtained from the CIE plots derived from the PL spectra. The CIE coordinates were further used to calculate the CCT values of the samples. τ-PL spectroscopy was carried out to measure the life-time of the photogenerated electrons. PL studies of the samples revealed that the blue emissions have red, yellow, and blue components originating from crystalline point defects, viz. zinc interstitial (Zni), and oxygen interstitial (Oi). Annealing at different temperatures triggered changes in the defect concentrations leading to the corresponding changes in the intensity, shade, and color temperature of the blue phosphorescence.

Durable and Flexible Superhydrophobic Materials: Abrasion/Scratching/Slicing/Droplet Impacting/Bending/Twisting-Tolerant Composite with Porcupinefish-Like Structure

Superhydrophobic materials with micro/nanotextured surface have attracted tremendous attention owing to their potential applications such as self-cleaning, antifouling, anti-icing, and corrosion prevention. Such a micro/nanotextured surface is a key for high water repellency. However, such a texture is fragile and readily damaged when the material is deformed, scratched, or sliced off. Thus, it is challenging to develop superhydrophobic materials that can sustain high water repellency after experiencing such a mechanical deformation and damage. Here we report abrasion/scratching/slicing/droplet impacting/bending/twisting-tolerant superhydrophobic flexible materials with porcupinefish-like structure by using a composite of micrometer-scale tetrapod-shaped ZnO and poly(dimethylsiloxane). Owing to the geometry of the tetrapod and elasticity of poly(dimethylsiloxane), the composite material exhibits stable water repellency after 1000 abrasion and 1000 bending cycles, or even after their surfaces were sliced off many times. The material maintains superhydrophobicity even under a mechanically deformed state such as bending and twisting. The materials can be painted on a variety of substrates and molded into desired shapes and used in a myriad of applications that require superhydrophobicity.

Antibacterial Application on Staphylococcus aureus Using Antibiotic Agent/Zinc Oxide Nanorod Arrays/Polyethylethylketone Composite Samples

In this study, zinc oxide (ZnO) nanorod arrays as antibiotic agent carriers were grown on polyetheretherketone (PEEK) substrates using a chemical synthesis method. With the concentration of ammonium hydroxide in the precursor solution kept at 4 M, ZnO nanorod arrays with diameters in the range of 100-400 nm and a loading density of 1.7 mg/cm2 were grown onto the PEEK substrates. Their drug release profiles and the antibacterial properties of the antibiotic agent/ZnO/PEEK samples in the buffer solution were investigated. The results showed that the concentrations of antibiotic agents (ampicillin or vancomycin) released from the samples into the buffer solution were higher than the value of minimum inhibitory concentration of 90% for Staphylococcus aureus within the 96 h test. The bioactivities of ampicillin and vancomycin on substrates also showed around 40% and 80% on the Staphylococcus aureus, respectively. In the antibacterial activity test, sample with the suitable loading amount of antibiotic agent had a good inhibitory effect on the growth of Staphylococcus aureus.

Effect of the calcination process on CdO-ZnO nanocomposites by a honey-assisted combustion method for antimicrobial performance

This work reports on honey as a combustion agent of CdO : ZnO nanocomposites and the effects of further annealing (100 °C, 200 °C, 300 °C and 400 °C) on their structural, optical, morphological, elemental, electrical and antimicrobial properties are investigated. X-ray diffraction spectra confirm the cubic and hexagonal structure of CdO : ZnO nanocomposites at 400 °C. When the calcination temperature was increased, the crystallinity, absorbance, bandgap, luminescence intensity, morphological dispersion and mean particle size were also increased. HR-TEM imaging confirmed spherical particles with an average particle size of ∼49 nm. The electrical conductivity of the CdO : ZnO nanoparticles was investigated. The antimicrobial activity of CdO : ZnO nanocomposites was tested for various bacterial and fungal organisms using a zone inhibition method.

Super-long ZnO nanofibers and novel nucleation mechanism for a gas-phase environment: spatial linear nucleation

Single-crystal super-long ZnO nanofibers (SZFs) have been prepared based on a newly proposed spatial linear nucleation (SLN) mechanism.

Ultrasonic assisted synthesis of two new coordination polymers and their applications as precursors for preparation of nano-materials

Two new isostructural coordination polymers, [Zn₃(Oba)₄][Me₂NH₂)₂]·6DMF·3H₂O (1) and [Cd₃(Oba)₄][Me₂NH₂)₂]·2DMF·2H₂O (2), were synthesized using the nonlinear dicarboxylate ligand, 4,4'-oxybis(benzoic acid) (H₂oba) and characterized by IR spectroscopy and single-crystal X-ray crystallography. Single-crystal X-ray data show that 1 and 2 are two-dimensional coordination polymers that can be extended to three-dimensional supramolecular networks by CH…O interactions. These two new coordination polymers were also sonochemically synthesized while sonication time and power of irradiation influencing size and morphology of nano-structured compounds were also studied. Moreover, calcination of these coordination polymers creates ZnO and CdO nanostructures.

Novel multiple phosphorescence in nanostructured zinc oxide and calculations of correlated colour temperature

A thermodynamic explanation using defect chemistry for the temperature and atmosphere dependent novel multiple phosphorescence in ZnO nanoparticles (∼160 nm) fit for cool lighting application is reported.

Flexible Light-Emitting Nanocomposite Based on ZnO Nanotetrapods

Flexible, light-emitting materials have shown promise in a wide range of applications. Here, we develop an inverse soft-lithography process for embedding zinc oxide nanotetrapods (ZnO NTP) uniformly and nondestructively into a host matrix. The crystalline NTPs were synthesized using a catalyst-free, environmentally friendly chemical vapor transport method. The fluorescent emission of the ZnO NTPs was measured before and after the embedding process. Cyclical mechanical bend tests (N > 100) were performed. The emission of the nanomaterial remains throughout.

High adsorption capacity of two Zn-based metal-organic frameworks by ultrasound assisted synthesis

Micro- and nano-rods and plates of two 3D, porous Zn(II)-based metal-organic frameworks [Zn(oba)(4-bpdh)0.5]n·(DMF)1.5 (TMU-5) and [Zn(oba)(4-bpmb)0.5]n (DMF)1.5 (TMU-6) were prepared by sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy. These MOFs were synthesized using a non-linear dicarboxylate (H2oba=4,4-oxybisbenzoic acid) and two linear N-donor (4-bpdh=2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene and 4-bpmb=N(1),N(4)-bis((pyridin-4-yl)methylene)benzene-1,4-diamine) ligands by ultrasonic irradiation. Sonication time and concentration of initial reagents influencing size and morphology of nano-structured MOFs, were also studied. Calcination of TMU-5 and TMU-6 at 550°C under air atmosphere yields ZnO nanoparticles. TMU-5 and TMU-6 exhibited maximum percent adsorption of 96.2% and 92.8% of 100ppm rhodamine B dye, respectively, which obeys first order reaction kinetics.

Sonochemical synthesis of nanoplates of two Cd(II) based metal-organic frameworks and their applications as precursors for preparation of nano-materials

Nano plates of two Cd(II)-based metal-organic frameworks, [Cd2(oba)2(4-bpdb)2]n ·(DMF)x(TMU-8) and [Cd(oba)(4,4'-bipy)]n ·(DMF)y (TMU-9) were synthesized via sonochemical reaction by using various time and concentrations of initial reagents and power of irradiation and characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy. Moreover, the effect of triethylamine on speed of nucleation during the synthesis was investigated. Thermolysis of these MOFs at 550°C under air atmosphere yields CdO nanoparticles.

Novel green phosphorescence from pristine ZnO quantum dots: tuning of correlated color temperature

Creating novel functionality is always fascinating as well as advantageous from a device point of view.

Direct Growth of Freestanding ZnO Tetrapod Networks for Multifunctional Applications in Photocatalysis, UV Photodetection, and Gas Sensing

Growth of freestanding nano- and microstructures with complex morphologies is a highly desired aspect for real applications of nanoscale materials in various technologies. Zinc oxide tetrapods (ZnO-T), which exhibit three-dimensional (3D) shapes, are of major importance from a technological applications point of view, and thus efficient techniques for growth of different varieties of tetrapod-based networks are demanded. Here, we demonstrate the versatile and single-step synthesis of ZnO-T with different arm morphologies by a simple flame transport synthesis (FTS) approach, forming a network. Morphological evolutions and structural intactness of these tetrapods have been investigated in detail by scanning electron microscopy, X-ray diffraction, and micro-Raman measurements. For a deeper understanding of the crystallinity, detailed high-resolution transmission electron microscopic studies on a typical ZnO tetrapod structure are presented. The involved growth mechanism for ZnO tetrapods with various arm morphologies is discussed with respect to variations in experimental conditions. These ZnO-T have been utilized for photocatalytic degradation and nanosensing applications. The photocatalytic activities of these ZnO-T with different arm morphologies forming networks have been investigated through the photocatalytic decolorization of a methylene blue (MB) solution under UV light illumination at ambient temperature. The results show that these ZnO-T exhibit strong photocatalytic activities against MB and its complete degradation can be achieved in very short time. In another application, a prototype of nanoelectronic sensing device has been built from these ZnO-T interconnected networks and accordingly utilized for UV detection and H2 gas sensing. The fabricated device structures showed excellent sensing behaviors for promising practical applications. The involved sensing mechanisms with respect to UV photons and H2 gas are discussed in detail. We consider that such multifunctional nanodevices based on ZnO tetrapod interconnected networks will be of interest for various advanced applications.

Investigation on the optimization, design and microwave absorption properties of reduced graphene oxide/tetrapod-like ZnO composites

We demonstrated the excellent microwave absorption properties of RGO/tetrapod-like ZnO composites, and investigated the effects of RGO mass fractions and thickness of composites on microwave absorption properties in the range from 2 to 18 GHz.

Hierarchical porous carbon derived from recycled waste filter paper as high-performance supercapacitor electrodes

Hierarchical activated porous carbon (APC) was synthesized through convenient chemical activation with ZnCl₂ using recycled waste filter paper as the carbon precursor.

Effective CdS/ZnO nanorod arrays as antireflection coatings for light trapping in c-Si solar cells

The cell with CdS/ZnO nanorod array (NRAs) antireflection coatings exhibits lower reflectance and better light trapping ability than the c-Si solar cell.

Ultrasound assisted synthesis of a Zn(ii) metal–organic framework with nano-plate morphology using non-linear dicarboxylate and linear N-donor ligands

Nano-plates of TMU-4 were obtained upon ultrasonic irradiation.

Convenient synthesis of porous carbon nanospheres with tunable pore structure and excellent adsorption capacity

A novel adsorbent, porous carbon nanosphere (PCNS), was conveniently prepared by the chemical activation of hydrothermally synthesized carbon nanosphere (CNS) with ZnCl2. The obtained PCNS materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 sorption technology and transmission electron microscope, and the results indicated that these materials possessed superior porosity with high surface area and large pore volume, in the meantime maintaining the nanospherical morphologies. Moreover, the porous structure of PCNS can be tuned from micropores to mesopores by adjusting the mass ratio of ZnCl2/CNS and the activation temperature. The porous structure endued PCNS excellent performance for the adsorption of bulky dyes from aqueous solution. Detailed adsorption behaviors of the optimized PCNS material, including adsorption isotherms and adsorption kinetics, were investigated. The experimental data of equilibrium adsorption capacity well matched Langmuir isotherms, and the maximum adsorption amounts of methylene blue, malachite green and rhodamine B were calculated as 3152, 1455 and 1409 mg g(-1), respectively, which were much higher than those of activated carbon and mesoporous carbon. The kinetic data were fitted to the models of pseudo-first-order and pseudo-second-order, which followed more closely the pseudo-second-order chemisorptions model. In addition, PCNS exhibited a good reusable property after five consecutive cycles.

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation were constructed with ohmic and Schottky contact characteristics. Localized UV irradiation at the third leg of the tetrapod was monitored by measuring the sensor's current response. Measurements of I-V performances and time-resolved current were conducted. The results demonstrate that localized UV irradiation can be detected in real time as electrical transport properties can be modulated by localized UV irradiation, and the higher the UV light power density gets, the larger the current response becomes, which is observed to be completely repeatable and reversible. Additionally, Schottky-contact type sensors clearly show a greater current response than ohmic-contact-type sensors, which further proved that Schottky-contact-type sensors are a better choice for detection in an irradiation environment. Two possible explanations are given for the phenomenon, including an electron transfer effect and a surface/interface effect on the band structure. The as-constructed sensors exhibit different sensitivities towards irradiation with various power densities, indicating that ZnO nanotetrapod-based sensors can be a promising candidate for detection in many areas including electron irradiation detection, ultraviolet irradiation monitoring, strain sensing, and complicated microenvironment observations such as biological cell inspection.

Catalyst-free direct vapor-phase growth of Zn1-xCuxO micro-cross structures and their optical properties

We report a simple catalyst-free vapor-phase method to fabricate Zn1-xCuxO micro-cross structures. Through a series of controlled experiments by changing the location of the substrate and reaction time, we have realized the continuous evolution of product morphology from nanorods into brush-like structures and micro-cross structures at different positions, together with the epitaxial growth of branched nanorods from the central stem with the time extended. The growth mechanism of the Zn1-xCuxO micro-cross structures has been proposed to involve the synthesis of Cu/Zn square-like core, surface oxidation, and the secondary growth of nanorod arrays. By the detailed structural analysis of the yielded Zn1-xCuxO samples at different locations, we have shown that the CuO phases were gradually formed in Zn1-xCuxO, which is significant to induce the usual ZnO hexagonal structures changing into four-folded symmetrical hierarchical micro-cross structures. Furthermore, the visible luminescence can be greatly enhanced by the introduction of Cu, and the observed inhomogeneous cathode luminescence in an individual micro-cross structure is caused by the different distributions of Cu.

Growth of High-Density Zinc Oxide Nanorods on Porous Silicon by Thermal Evaporation

The formation of high-density zinc oxide (ZnO) nanorods on porous silicon (PS) substrates at growth temperatures of 600–1000 °C by a simple thermal evaporation of zinc (Zn) powder in the presence of oxygen (O₂) gas was systematically investigated. The high-density growth of ZnO nanorods with (0002) orientation over a large area was attributed to the rough surface of PS, which provides appropriate planes to promote deposition of Zn or ZnO_x seeds as nucleation sites for the subsequent growth of ZnO nanorods. The geometrical morphologies of ZnO nanorods are determined by the ZnO_x seed structures, i.e., cluster or layer structures. The flower-like hexagonal-faceted ZnO nanorods grown at 600 °C seem to be generated from the sparsely distributed ZnO_x nanoclusters. Vertically aligned hexagonal-faceted ZnO nanorods grown at 800 °C may be inferred from the formation of dense arrays of ZnO_x clusters. The formation of disordered ZnO nanorods formed at 1000 °C may due to the formation of a ZnO_x seed layer. The growth mechanism involved has been described by a combination of self-catalyzed vapor-liquid-solid (VLS) and vapor-solid (VS) mechanism. The results suggest that for a more precise study on the growth of ZnO nanostructures involving the introduction of seeds, the initial seed structures must be taken into account given their significant effects.

Synthesis and applications of CdSe nano-tetrapods in hybrid photovoltaic devices

Tetrapod-shaped nanocrystals have attracted increasing interest for optoelectronic applications in recent years due to their rich morphologies. With unique properties such as a direct band-gap and excellent photoelectrical characteristics, CdSe nano-tetrapods are promising nanostructures for applications in such fields as photodetectors, field emitters, and photovoltaic devices. This review mainly describes the remarkable progress made in synthesis and hybrid photovoltaic applications of CdSe nano-tetrapods over the last few years. In particular, the “blinking” effect observed from these nano-tetrapods in chloroform solution is highlighted. This overview covers the current state of the art as well as an outlook on possibilities and limitations.

Sputtered ZnO-SiO2 nanocomposite light-emitting diodes with flat-top nanosecond laser treatment

Sputtered ZnO-SiO2 nanocomposite light-emitting diodes (LEDs) were treated using a flat-top nanosecond laser (FTNL) under room temperature. The intensity of the 376 nm electroluminescence (EL) emission of ZnO-SiO2 nanocomposite LEDs at a current of 9 mA with FTNL treatment was approximately 1.4 times greater than LEDs without FTNL treatment. Furthermore, the FTNL-treated LEDs indicated a narrower full width at half maximum of the 376 nm EL emission than those of LEDs without FTNL treatment. Thus, FTNL treatment of ZnO-SiO2 nanocomposite LEDs could induce the recrystallization of distributed ZnO nanoclusters and reduce the defects in ZnO-SiO2 nanocomposite layers.

Growth of ZnO Nanorod Arrays on Flexible Substrates: Effect of Precursor Solution Concentration

We report a low-temperature aqueous solution growth of uniformly aligned ZnO nanorod arrays on flexible substrates. The substrate is Indium Tin Oxide (ITO) film coated on polyethylene terephthalate (PET). Solutions with five different concentrations of the precursors with equimolar Zinc Nitrate and Hexamethylenetetramine (HMT) in distilled water were prepared to systematically study the effect of precursor solution concentration on the structural and optical properties of ZnO nanorods. It was concluded that the precursor concentration have great influence on the morphology, crystal quality, and optical property of ZnO nanorods. The diameter, density, and orientation of the nanorods are dependent on the precursor solution concentration. X-ray diffraction and micro-Raman spectroscopy showed that the ZnO nanorods with the highest concentration of 50 mM were highly aligned and have the highest level of surface coverage. It was also found that the diameter and length of the nanorods increases upon increasing precursor solution concentration. This is the first systematic investigation of studying the effect of precursor solution concentration on the quality of ZnO nanorods grown on ITO/PET substrates by low-temperature solution method. We believe that our work will contribute to the realization of flexible organic-inorganic hybrid solar cell based on ZnO nanorods and conjugated polymer.

A highly sensitive electrochemical biosensor based on zinc oxide nanotetrapods for L-lactic acid detection

An amperometric biosensor based on zinc oxide (ZnO) nanotetrapods was designed to detect L-lactic acid. The lactate oxidase was immobilized on the surface of ZnO nanotetrapods by electrostatic adsorption. Unlike traditional detectors, the special four-leg individual ZnO nanostructure, as an adsorption layer, provides multiterminal charge transfer channels. Furthermore, a large amount of ZnO tetrapods are randomly stacked to form a three-dimensional network naturally that facilitates the exchange of electrons and ions in the phosphate buffer solution. Utilizing amperometric response measurements, the prepared ZnO nanotetrapod L-lactic acid biosensor displayed a detection limit of 1.2 μM, a low apparent Michaelis-Menten constant of 0.58 mM, a high sensitivity of 28.0 μA cm(-2) mM(-1) and a good linear relationship in the range of 3.6 μM-0.6 mM for the L-lactic acid detection. This study shows that the biosensor based on ZnO tetrapod nanostructures is highly sensitive and able to respond rapidly in detecting lactic acid.

Nanoparticle-controlled aggregation of colloidal tetrapods

Tetrapods are among the most promising building blocks for nanoscale self-assembly, offering various desirable features. Whereas these particles can be fabricated with remarkable precision, comparatively less is known about their aggregation behavior. Employing a novel, powerful simulation method, we demonstrate that charged nanoparticles offer considerable control over the assembly of tip-functionalized tetrapods. Extending these findings to tetrapods confined to a gas/liquid interface, we show that regular structures can be achieved even without functionalization.

The interplay of structural and optical properties in individual ZnO nanostructures

Semiconductor nanostructures exhibit unique properties distinct from their bulk counterparts by virtue of nanoscale dimensions; in particular, exceptionally large surface area-to-volume ratios relative to that of the bulk produce variations in surface state populations that have numerous consequences on materials properties. Of the low-dimensional semiconductor nanostructures, nanowires offer a unique prospect in nanoscale optoelectronics due to their one-dimensional architecture. Already, many devices based upon individual nanowires have been demonstrated, but questions about how nano-size and structural variations affect the underlying materials properties still remain unanswered. Here, we focus on understanding the growth mechanism and kinetics of ZnO nanowires and related nanowalls, and their effects on nanoscale structural and optical properties.

Growth and structure analysis of tungsten oxide nanorods using environmental TEM

WO3 nanorods targeted for applications in electric devices were grown from a tungsten wire heated in an oxygen atmosphere inside an environmental transmission electron microscope, which allowed the growth process to be observed to reveal the growth mechanism of the WO3 nanorods. The initial growth of the nanorods did not consist of tungsten oxide but rather crystal tungsten. The formed crystal tungsten nanorods were then oxidized, resulting in the formation of the tungsten oxide nanorods. Furthermore, it is expected that the nanorods grew through cracks in the natural surface oxide layer on the tungsten wire.