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ZnO hollow spherical structures with different surface-to-volume ratios were prepared using solid Zn microspheres as template via a simple oxygen-controlled thermal evaporation approach. The results of scanning electron microscopy testify that ZnO hollow spherical structures with different morphologies can be realized by changing oxygen supply. The corresponding transmission electron microscopy images further reveal that the prepared spherical structures are hollow, and nanorods epitaxially grow from the surface of the sphere shell along the [0001] direction. A series of experiments indicates that the formation of hollow spherical structures involves the oxidization on the surface of Zn microspheres, sublimation of Zn, and growth of ZnO nanorods. [ABSTRACT FROM AUTHOR] more...

The effect of pine provenance trials of Pinus sibirica Du Tour and Pinus koraiensis Siebold et Zucc. grown in Krasnoyarsk and Khabarovsk krais on the chemical and biological parameters of gray forest and brown forest soils in the rhizosphere and between rows of plantations is compared. It is shown that the interspecies heterogeneity of pines affects the chemical composition of the soil, the enzymatic and microbiological activity, and the formation of prokaryotic microbiomes. It is noted that the biodiversity of prokaryotes is more strongly determined by the features of soil types than by the inter- and intraspecies heterogeneity of pines and by the effect of their roots. The phyla Proteobacteria, Acidobacteria, and Actinobacteria dominate in both soil types and together account for 75–85% of the total number of type-specific 16S rRNA gene sequences in each soil. [ABSTRACT FROM AUTHOR] more...

The influence of growth parameters of the spin-spray technique upon the microstructure and electrical and optical properties of ZnO and Al-doped ZnO microstructures was investigated. This investigation was carried out by varying the pH and concentration of the solutions utilized. With increasing pH from 9 to 12, the ZnO films changed from membrane-like microstructures at a pH of 9 to single crystal ZnO rods with hexagonal ends at the pH of 10, and to polycrystal ZnO needle-like tips with random crystalline orientation at the pH of 12. Varying the concentration of the solution brought about a dramatic change in the crystal growth behavior and crystalline orientation, with the least concentration producing rods more uniform and oriented in the c-axis direction. The optical absorption dependence of the ZnO microstructures was also studied by ultraviolet visible spectrophotometer. This investigation will enable optimized low temperature (<100 °C) fabrication of ZnO films by the spin-spray technique with controllable microstructure and properties based on their processing conditions. Furthermore, the influence of Al doping on the electric property, optical property microstructures of the Al-doped ZnO thin films was examined. Increase in Al concentration from 0 to 2 % further reduced the resistivity of the ZnO films by 3 orders of magnitudes from 3.4 × 10 to 14 Ω cm; while the Hall mobility increases from 1 to 140 cm/V s at the same time. The optical photoluminescence measurement of Al-doped ZnO thin films in ultra violet (UV) was also demonstrated. [ABSTRACT FROM AUTHOR] more...

Hollow spherical ZnO particles doped with Ag were synthesized with a two-step oxidation and sublimation furnace annealing process. Ag nanoparticle precipitates, as observed by transmission electron microscopy, were present in the polycrystalline ZnO matrix at Ag concentrations below 0.02 mol%, significantly below the 0.8 mol% solubility limit for Ag in ZnO. Enhanced Raman scattering of ZnO phonon modes is observed, increasing with Ag nanoparticle concentration. A further enhancement in Raman scattering due to resonance effects was observed for LO phonons excited by 2.33-eV photons as compared with Raman scattering under 1.96-eV excitation. Room-temperature photoluminescence spectra showed both a near-band-edge emission due to free exciton transitions and a mid-gap transition due to the presence of singly ionized oxygen vacancies. ZnO:Ag particles were measured electrically in a packed column and in monolithic form, and in both cases displayed nonlinear current-voltage characteristics similar to those previously observed in sintered ZnO:Ag monoliths where Ag-enhanced disorder at grain boundaries is thought to control current transport. We demonstrate therefore that Ag simultaneously modifies the electrical and optical properties of ZnO particles through the introduction of vacancies and other defects. [ABSTRACT FROM AUTHOR] more...

Mesoporous ZnO microfans have been successfully synthesized from the ZnS microfans by the thermal treatment. The morphology, specific surface area, and optical properties of ZnO microfans were analyzed by X-ray diffraction, scanning electron microscope, N adsorption,and photoluminescence spectroscopy. Results reveal that ZnO microfans show good crystalline quality, high specific surface area, and excellent optical properties. [ABSTRACT FROM AUTHOR] more...

A solution-processable, high-concentration transparent ZnO nanoparticle (NP) solution was successfully synthesized in a new process. A highly transparent ZnO thin film was fabricated by spin coating without vacuum deposition. Subsequent ultra-short-pulsed laser annealing at room temperature was performed to change the film properties without using a blanket high temperature heating process. Although the as-deposited NP thin film was not electrically conductive, laser annealing imparted a large conductivity increase and furthermore enabled selective annealing to write conductive patterns directly on the NP thin film without a photolithographic process. Conductivity enhancement could be obtained by altering the laser annealing parameters. Parametric studies including the sheet resistance and optical transmittance of the annealed ZnO NP thin film were conducted for various laser powers, scanning speeds and background gas conditions. The lowest resistivity from laser-annealed ZnO thin film was about 4.75×10 Ω cm, exhibiting a factor of 10 higher conductivity than the previously reported furnace-annealed ZnO NP film and is even comparable to that of vacuum-deposited, impurity-doped ZnO films within a factor of 10. The process developed in this work was applied to the fabrication of a thin film transistor (TFT) device that showed enhanced performance compared with furnace-annealed devices. A ZnO TFT performance test revealed that by just changing the laser parameters, the solution-deposited ZnO thin film can also perform as a semiconductor, demonstrating that laser annealing offers tunability of ZnO thin film properties for both transparent conductors and semiconductors. [ABSTRACT FROM AUTHOR] more...

In the past decades, there was considerable controversy over the Lucas-Washburn (LW) equation widely applied in capillary imbibition kinetics. Many experimental results showed that the time exponent of the LW equation is less than 0.5. Based on the tortuous capillary model and fractal geometry, the effect of tortuosity on the capillary imbibition in wetting porous media is discussed in this article. The average height growth of wetting liquid in porous media driven by capillary force following the $${\overline L _{\rm {s}}(t)\sim t^{1/{2D_{\rm {T}}}}}$$ law is obtained (here D is the fractal dimension for tortuosity, which represents the heterogeneity of flow in porous media). The LW law turns out to be the special case when the straight capillary tube ( D = 1) is assumed. The predictions by the present model for the time exponent for capillary imbibition in porous media are compared with available experimental data, and the present model can reproduce approximately the global trend of variation of the time exponent with porosity changing. [ABSTRACT FROM AUTHOR] more...

Nanotip arrays of amorphous carbon with embedded hexagonal diamond nanoparticles were prepared at room temperature for use as excellent field emitters by a unique combination of anodic aluminum oxide (AAO) template and filtered cathodic arc plasma (FCAP) technology. In order to avoid nanopore array formation on the AAO surface, an effective multi-step treatment employing anodization and pore-widening processes alternately was adopted. The nanotips were about 100 nm in width at the bottom and 150 nm in height with density up to 10 cm. Transmission electron microscopy investigation indicates that many nanoparticles with diameters of about 10 nm were embedded in the amorphous carbon matrix, which was proved to be hexagonal diamond phase by Raman spectrum and selected-area electron diffraction. There is no previous literature report on the field emission properties of hexagonal diamond and its preparation at room temperature under high-vacuum condition. The nanotip arrays with hexagonal diamond phase exhibit a low turn-on field of 0.5 V/μm and a threshold field of 3.5 V/μm at 10 mA/cm. It is believed that the existence of hexagonal diamond phase has improved the field emission properties. [ABSTRACT FROM AUTHOR] more...

size-controlled Zn(OH) template is used as a case study to explain the chemical strategy that can be executed to chemically engineering various nanoscale cavities. Zn(OH) octahedron with 8 vertices and 14 edges is fabricated via a low temperature solution route. The size can be tuned from 1 to 30 μm by changing the reaction conditions. Two methods can be selected for the hollow process without loss of the original shape of Zn(OH) template. Ion-replacement reaction is suitable for fabrication of hollow sulfides based on the solubility difference between Zn(OH) and products. Controlled chemical deposition is utilized to coat an oxide layer on the surface of Zn(OH) template. The abundant hydroxyl groups on Zn(OH) afford strong coordination ability with cations and help to the coating of a shell layer. The rudimental Zn(OH) core is eliminated with ammonia solution. In addition, ZnO-based heterostructures possessing better chemical or physical properties can also be prepared via this unique templating process. Room-temperature photoluminescence spectra of the heterostructures and hollow structures are also shown to study their optical properties. [ABSTRACT FROM AUTHOR] more...

This work is trying to fabricate nanostructure, for the first time, on the porous anodic alumina’s (PAA) barrier layer, which has smooth half-sphere structure. The deposition of indium oxide confirms that the materials can completely cover the surface area of the barrier layer. Both chemical dissolving the PAA or mechanical peel-off can bring free-standing indium oxide thin layer. Morphology study on both sides of deposited layer verifies that the ordered indium oxide nanorods can self-arrange well and form a half-sphere front surface and nanohole-array rear surface. This work confirms that we can get some special nanostructures with the help of the barrier layer of PAAs. [ABSTRACT FROM AUTHOR] more...

Porous anodic alumina (PAA) has been intensively studied in past decade due to its applications for fabricating nanostructured materials. Since PAA’s pore diameter, thickness and shape vary too much, a systematical study on the methods of morphology characterization is meaningful and essential for its proper development and utilization. In this paper, we present detailed AFM, SEM and TEM studies on PAA and its evolvements with abundant microstructures, and discuss the advantages and disadvantages of each method. The sample preparation, testing skills and morphology analysis are discussed, especially on the differentiation during characterizing complex cross-sections and ultrasmall nanopores. The versatility of PAAs is also demonstrated by the diversity of PAAs’ microstructure. [ABSTRACT FROM AUTHOR] more...

Zinc oxide thin films doped with Li were deposited by ultrasonic spray pyrolysis (USP) at 350 ± 5°C on glass substrates from solutions of zinc acetate [Zn(CH3COO)2</subscript> · 2H2O] and lithium acetate [C2H3LiO2 · 2H2O], in which the Li/Li + Zn ratios were 1 at.%, 3 at.%, and 5 at.%. The effects of the doping on the structural, optical, electrical, and morphological properties of the films were examined. X-ray diffraction patterns indicated that the undoped and Li-doped ZnO films had a polycrystalline hexagonal wurtzite structure with a (002) preferred orientation. The films showed optical transmission around 60–80% in the visible region of the spectrum. The films were found to be transparent in the wavelength range of 450–900 nm, with sharp ultraviolet absorption edges in the wavelength range of 350–450 nm. The absorption edge analysis revealed that the optical band gap energies for the films were between 3.24 eV and 3.29 eV, and the electronic transition was of the direct transition type. The width of the band tail states, which is connected to the localized states in the band gap, was estimated to be 82–113 meV by Urbach tail analysis. For study of the electrical properties of the films, Hall effect measurements, electrical conductivities, conductivity activation, and trap energies were investigated. The electrical measurements of the films were obtained in the dark, in vacuum, and in the temperature range of 10–300 K. Morphological studies for the films were carried out by scanning electron microscopy. [ABSTRACT FROM AUTHOR] more...

Performance of biological phosphorus removal in the oxic-settling-anaerobic (OSA) process was investigated. Cell staining and fluorescent in situ hybridization (FISH) were used to analyze characteristics and microbial community of sludge. Experimental results showed that phosphorus removal efficiency was near 60% and the amount of biological phosphorus accumulation in aerobic sludge of the OSA system was up to 26.9 mg/g. Biological phosphorus removal efficiency was partially inhibited by carbon sources in the continuous OSA system. Contrasted to the OSA system, biological phosphorus removal efficiency was enhanced by 14% and the average total phosphorus (TP) contents of aerobic sludge were increased by 0.36 mg/g when sufficient carbon sources were supplied in batch experiments. Staining methods indicated that about 35% of microorganisms had typical characteristics of phosphorus accumulating organisms (PAOs). FISH analysis demonstrated that PAOMIX-binding bacteria were predominant microbial communities in the OSA system, which accounted for around 28% of total bacteria. [ABSTRACT FROM AUTHOR] more...