One-step aqueous solvothermal synthesis of In2O3 nanocrystals

Highly crystalline and nearly monodisperse In2O3 nanocrystals with both cube and flower shapes were successfully synthesized in one step through a facile aqueous solvothermal method for the first time, free of any surfactant or template. X-ray diffraction (XRD), transmission electron microscopy (TEM), selective area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the samples. In our work, the use of diethylene glycol (DEG) is a crucial factor for the formation of the In2O3 phase.

Effects of ammonia and cetyltrimethylammonium bromide (CTAB) on morphologies of ZnO nano- and micromaterials under solvothermal process

Submicrometer zinc oxide (ZnO) with different morphologies including spindle-like, pencil-like, branch rod-like and frizzy flower-like shapes, have been hydrothermally synthesized in mixed solvents of ethanol and water at 140 degrees C. It was found that the volumes of added ammonia, surfactant (cetyltrimethylammonium bromide, CTAB), and mixed solvent play crucial roles in morphological control of ZnO nanostructures. Increasing the volume of ammonia added to the reaction system, the shape of ZnO evolves from spindle into branch rod-like. Synergetic influence between CTAB and ammonia can only be observed at high concentration of ammonia.

DNA-Templated Gold Nanoparticles Formation

The interaction between HAuCl4 and DNA has enabled creation of DNA-templated gold nanoparticles without formation of large nanoparticles. It was found that spheral DNA-HAuCl4 hybrid of 8.7 nm in diameter, flower-like DNA-HAuCl4 hybrid, nanoparticles chains and nanoparticles network of DNA-HAuCl4 hybrid could be obtained by varying the reaction conditions, including DNA concentration and reaction temperature. The intermediate product was investigated by shortening the reaction time of DNA and HAuCl4, and the obtained nanoparticles preserved a small DNA segment, which indicated that the reaction between DNA and HAuCl4 had a process.

Photochemical synthesis and self-assembly of gold nanoparticles

Colloidal gold was prepared by UV light irradiation of the mixture of HAuCl4 aqueous solution and poly(vinyl pyrrolidone) (PVP) ethanol solution in the presence of silver ions. The resulting sheet-like nanoparticles were found to self-assemble into nanoflowers by a centrifuging process. The results of control experiments reflected that only suitable size sheet-like nanoparticles could assemble into the flower-like structures. The presence of Ag ions and PVP are essential for the formation process of nanoflowers.

Shape-Controlled Synthesis of Wurtzite ZnS Microstructures Under Mild Solvothermal Condition

Through a facile solvothermal route using zinc chloride and thiourea as reactants, wurtzite ZnS and its precursor ZnS center dot (en)(0.5) (en = ethylenediamine) with various morphologies and sizes were grown, which were characterized by XRD, SEM, TEM and N-2 adsorption and so on. The phase evolution, composition and morphologies of the products are highly dependent on the concentration of en. By keeping the en-water volume ratio at 1/2 to 1, the nanostripes-flower or nanorod-spheric wurtzite ZnS were easily obtained under 120 degrees C for 6-24 h, which possess relatively higher specific surface area and larger total pore volume.

SrF2 hierarchical flowerlike structures: Solvothermal synthesis, formation mechanism, and optical properties

We present a solvothermal route to the synthesis of SrF2 hierarchical flowerlike structures based on thermal decomposition of single source precursor (SSP) of strontium trifluoroacetate in benzylamine solvent. These flowerlike superstructures are actually composed of numerous aggregated nanoplates, and the growth process involves the initial formation of spherical nanoparticles and subsequent transformation into nanoplates. which aggregated together to form microdisks and finally flowerlike superstructures. The results demonstrate the important role of benzylamine in the formation of well-defined SrF2 superstructures, not only providing size and shape control to form nanoplates but also contributing to the self-assembly behavior of nanoplates to build into flower-like superstructures. Additionally, the photoluminescence properties of the obtained SrF2 superstructures are studied.

Gold nanowire assembling architecture for H2O2 electrochemical sensor

Morphological control of nanomaterials is of great interest due to their size and shape-dependent chemical and physical properties and very important applications in many fields such as biomedicine, sensors, electronics and others. In this paper, we reported a simple strategy for synthesizing gold nanowire assembling architecture at room temperature. It is found that two important factors, the proper volume ratio of ethanol to water and poly(vinyl pyrrolidone) (PVP), will play important roles in synthesizing flower-like short gold nanowire assembling spheres. Furthermore, the obtained flower-like gold assembling spheres with high surface-to-volume ratio have been employed as enhancing materials for electrochemical sensing H2O2. The present electrochemical sensing platform exhibited good electrocatalytic activity towards the reduction of H2O2. The detection limit for H2O2 was found to be 1.2 mu M, which was lower than certain enzyme-based biosensors.

A General Route to Construct Diverse Multifunctional Fe3O4/Metal Hybrid Nanostructures

We have developed a simple, efficient, economical, and general approach to construct diverse multifunctional Fe3O4/metal hybrid nanostructures displaying magnetization using 3-aminopropyltrimethoxysilane (APTMS) as a linker. High-density Au nanoparticles (NPs) could be supported on the surface of superparamagnetic Fe3O4 spheres and used as seeds to construct Au shell-coated magnetic spheres displaying near-infrared (NIR) absorption., which may make them promising in biosensor and biomedicine applications. High-density flower-like Au/Pt hybrid NPs could be supported on the surface of Fe3O4 spheres to construct multifunctional hybrid spheres with high catalytic activity towards the electron-transfer reaction between potassium ferricyanide and sodium thiosulfate. High-density Ag or Au/Ag core/shell NPs could also be supported on the surface of Fe3O4 spheres and exhibited pronounced surface-enhanced Raman scattering (SERS), which may possibly be used as an optical probe with magnetic function for application in high-sensitivity bioassays.

Vaterite-type YBO3 : Eu3+ crystals: hydrothermal synthesis, morphology and photoluminescence properties

Vaterite-type YBO3:Eu3+ crystals with interesting flower and hedgehog fungus-like structures composed of nanosheets were obtained by controlled crystallization of Y2O3 and Eu2O3 in H3BO3 solutions under acidic hydrothermal (HT) conditions. Nanosheets of uniform thicknesses were formed by preferential crystal growth along the (100) crystallographic plane and specific three-dimensional structures were further developed through a homocentric growth mechanism. Optical emission measurements showed that the HT-grown nanosheet crystals exhibited a higher ratio of the emitted red-to-orange light ratio than crystals grown from solid-state reactions. The photoluminescence intensity and emission lifetimes were also studied as a function of the Eu3+ dopant concentration and the HT synthesis temperature. The effect of some additives: a chelating ligand, a surfactant and a polymer, on the YBO3:Eu3+ crystals morphology was also investigated.

Polyamidoamine dendrimers-assisted electrodeposition of gold-platinum bimetallic nanoflowers

Novel Au-Pt bimetallic flower nanostructures fabricated on a polyamidoamine dendrimers-modified surface by electrodeposition are reported. These polyamidoamine dendrimers were stable, and they assisted the formation of Au-Pt bimetallic nanoflowers during the electrodeposition process. These nanoflowers were characterized by field-emitted scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and electrochemical methods. FE-SEM images showed that the bimetallic nanoflower included two parts: the "light" and the "pale" part. The two parts consisted of many small bimetallic nanoparticles, which was attributed to the progressive nucleation process. Moreover, the "light" part contained more bimetallic nanoparticles. The morphologies of bimetallic nanoflowers depended on the electrodeposition time and potential and the layer number of assembled dendrimers. The average size of nanoflowers increased with the increase in electrodeposition time. The layer number of assembled dendrimers obviously affected the size and morphologies of the "pale" parts of deposited nanoflowers.

Precursor induced synthesis of hierarchical nanostructured ZnO

As-synthesized ZnO nanostructures with a bladed bundle-like architecture have been fabricated from a flower-like precursor ZnO (.) 0.33ZnBr(2) (.) 1.74H(2)O via a mechanism of dissolution - recrystallization. Experimental conditions, such as initial reactants and reaction time, are examined. The results show that no bladed bundle-like ZnO hierarchical nanostructures can be obtained by using the same molar amount of other zinc salts, such as ZnBr2, instead of the flower-like ZnO (.) 0.33ZnBr(2) (.) 1.74H(2)O precursor, and keeping other conditions unchanged. The products were characterized by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The ZnO nanostructures are mainly composed of nanowires with a diameter around 40 - 50 nm and length up to 1.5 - 2.5 mu m. Meanwhile, ZnO nanoflakes with a thickness of about 4 - 5 nm attached to the surface of ZnO nanowires with a preferred radially aligned orientation. Furthermore, the photoluminescence (PL) measurements exhibited the unique white-light-emitting characteristic of hierarchical ZnO nanostructures. The emission spectra cover the whole visible region from 380 to 700 nm.

Polymer concentration, shear and stretch field effects on the surface morphology evolution during the spin-coating

Polymer concentration and shear and stretch field effects on the surface morphology evolution of three different kinds of polymers (polystyrene (PS), polybutadiene (PB) and polystyrene-b-polybutadiene-b-polystyrene (SBS)) during the spin-coating were investigated by means of atomic force microscopy (AFM). For PS and SBS, continuous film, net-like structure and particle structure were observed at different concentrations. For PB, net-like structures were not observed and continuous films and radial array of droplets emerged. Moreover, we compared surface morphology transitions on different substrate locations from the center to the edge. For PS, net-like structure, broken net-like structure and irregular array of particles were observed. For SBS, net-like structure, periodically orientated string-like structure and broken-line structure appeared. But for PB, flower-like holes in the continuous film, distorted stream-like structure and irregular distributions of droplets emerged. These different transitions of surface morphologies were discussed in terms of individual material property.

Reproductive ecology of the Qinghai-Tibet Plateau endemic Gentiana straminea (Gentianaceae), a hermaphrodite perennial characterized by herkogamy and dichogamy

The combined occurrence of both herkogamy and dichogamy in a hermaphrodite species has been considered to strongly favour outcrossing. In this study, we investigated in detail the reproductive ecology of Gentiana straminea Maxim. (Gentianaceae), a hermaphrodite perennial endemic to the Qinghai-Tibet Plateau. In a series of observations and experiments over four consecutive years, we examined whether the combination of dichogamy and herkogamy in individual flowers completely prevents geitonogamous pollen transfer in this species. The mode of floral development clearly indicates that autonomous self-pollination is completely avoided through herkogamy and dichogamy in individual flowers. This implication was confirmed by the breeding experiments, since no seed was produced when flowers were isolated. However, this gentian proved to be highly self-compatible when geitonogamous selfing was artificially induced. Many flowers opened simultaneously on individual plants, the ratio of male to female phase flowers was close to 2:1 in each inflorescence, at the full anthesis phase, and they were randomly distributed amongst the upper, middle and lower parts of each stem's inflorescence. On average, Bombus sushikini Skorikov, the most frequent visitor and only legitimate pollinator of G. straminea, visited nearly two flowers per inflorescence, and four flowers per plant. Among the pollinators' foraging bouts, the proportions of geitonogamous visits to inflorescences or flowers within an individual plant were 29% and 37%, respectively. Therefore, despite the strict dichogamous and herkogamous characteristics of the individual flowers, geitonogamous selfing might still prevail in G. straininea because of the size of its floral displays and the continuous visiting behavior of B. sushkini. (C) 2005 Elsevier SAS. All rights reserved.

渤海湾地区前第三系构造特征及其演化研究

Based on fine structural interpretation on seismic profiles of buried-hills in Huanghua depression, structural interpretation and balanced cross-section restoration of regional seismic profiles, drawing structural maps of main seismic interfaces, residual strata distribution of different ages in the Bohai Bay region and structural survey in the western Shandong uplifted area and the intracontinental orogeny of Yanshan mountain, the paper has studied pre-tertiary structural styles and tectonic evolution of the Bohai Bay region. There mainly develop 5 types of pre-tertiary structural style that are extension structure, compression structure, strike-slip structure, negative inversion structure and sliding structure in the Bohai Bay region. Among these 5 types of structural style, extension structure develops detachment fault and its controlling fault terrain structure and fault break slop; compression structure develops reverted fold, fault propagation fold, fault bent fold, imbricate thrust structure and triangle zone; strike-slip structure develops positive flower structure, negative flower structure, en-echelon structure and brush structure; negative reversion structure develops Indosinian compression and Yanshanian extension negative reversion structure, late Yanshanian compression and Cenozoic extension negative reversion structure; sliding structure develops interlayer sliding structure and detachment structure. According to Cangdong fault of SN direction, Zhangjiakou – Penglai fault and Qihe – Guangrao fault of NWW direction, the Bohai Bay region can be divided into 6 sub-regions in which structural direction and style is different from each other. Structural maps of bottom boundary of Cenozoic and upper Paleozoic manifest that main NNE structural direction is formed from late Yanshanian to Himalayan movement and minor NWW structural direction and a string of area more than 8000m are mainly suggest that Indosinian tectonic pattern strongly influence on Yanshanian and Himalayan movement. Residual strata distribution characteristics of middle to upper Neoproterozoic in the Bohai Bay region manifest that middle- to neo- aulacogen position may be corresponding to late Mesozoic uplifted zone. Residual Paleozoic distribution characteristics of main ENN suggest that structural alteration should be resulted from late Yanshanian to Himalayan movement while which of minor NWW structures suggest that deeper structure should restrict shallower structure. Structural patterns of main EW fold direction in the Bohai Bay region and thrust structure in eastern part are formed late Triassic in studied area. Granite magma intrusion of early to middle Jurassic mainly develops Yanshan mountain zone. Late Mesozoic rifting basins of NEE direction are widely distributed in the Bohai Bay region and granite magma intrusions are mainly distributed in Tancheng – Rongcheng zone. Mesozoic structural evolution in the Bohai Bay region is related to scissor convergent from east to west between North China plate and Yangtze plate and gradually reinforcing of the west circum-pacific tectonic tract while basin and range province of late Jurassic and early Cretaceous may be mainly related to lithospheric thinning of North China craton in late Mesozoic.