Huaidong Jiang

A Bi2WO6‐Based Hybrid Photocatalyst with Broad Spectrum Photocatalytic Properties under UV, Visible, and Near‐Infrared Irradiation

Near-infrared active photocatalytic properties of Bi2 WO6 nanosheets owing to the oxygen vacancies of the Bi2 WO6 nanosheets are reported. The broad spectrum photocatalyst, Bi2 WO6 -TiO2 nanobelt heterostructures, are obtained by assembling Bi2 WO6 nanocrystals on TiO2 nanobelts. The active light band of the novel hybrid photocatalyst with high photocatalytic activity covers full-spectrum solar light including the UV, visible, and near-infrared ranges.

Quantitative 3D imaging of whole, unstained cells by using X-ray diffraction microscopy

Microscopy has greatly advanced our understanding of biology. Although significant progress has recently been made in optical microscopy to break the diffraction-limit barrier, reliance of such techniques on fluorescent labeling technologies prohibits quantitative 3D imaging of the entire contents of cells. Cryoelectron microscopy can image pleomorphic structures at a resolution of 3–5 nm, but is only applicable to thin or sectioned specimens. Here, we report quantitative 3D imaging of a whole, unstained cell at a resolution of 50–60 nm by X-ray diffraction microscopy. We identified the 3D morphology and structure of cellular organelles including cell wall, vacuole, endoplasmic reticulum, mitochondria, granules, nucleus, and nucleolus inside a yeast spore cell. Furthermore, we observed a 3D structure protruding from the reconstructed yeast spore, suggesting the spore germination process. Using cryogenic technologies, a 3D resolution of 5–10 nm should be achievable by X-ray diffraction microscopy. This work hence paves a way for quantitative 3D imaging of a wide range of biological specimens at nanometer-scale resolutions that are too thick for electron microscopy.

Quantitative imaging of single, unstained viruses with coherent x rays.

We report the recording and reconstruction of x-ray diffraction patterns from single, unstained viruses, for the first time. By separating the diffraction pattern of the virus particles from that of their surroundings, we performed quantitative and high-contrast imaging of a single virion. The structure of the viral capsid inside a virion was visualized. This work opens the door for quantitative x-ray imaging of a broad range of specimens from protein machineries and viruses to cellular organelles. Moreover, our experiment is directly transferable to the use of x-ray free electron lasers, and represents an experimental milestone towards the x-ray imaging of large protein complexes.

Three-dimensional structure determination from a single view

The ability to determine the structure of matter in three dimensions has profoundly advanced our understanding of nature. Traditionally, the most widely used schemes for three-dimensional (3D) structure determination of an object are implemented by acquiring multiple measurements over various sample orientations, as in the case of crystallography and tomography, or by scanning a series of thin sections through the sample, as in confocal microscopy. Here we present a 3D imaging modality, termed ankylography (derived from the Greek words ankylos meaning ‘curved’ and graphein meaning ‘writing’), which under certain circumstances enables complete 3D structure determination from a single exposure using a monochromatic incident beam. We demonstrate that when the diffraction pattern of a finite object is sampled at a sufficiently fine scale on the Ewald sphere, the 3D structure of the object is in principle determined by the 2D spherical pattern. We confirm the theoretical analysis by performing 3D numerical reconstructions of a sodium silicate glass structure at 2 Å resolution, and a single poliovirus at 2–3 nm resolution, from 2D spherical diffraction patterns alone. Using diffraction data from a soft X-ray laser, we also provide a preliminary demonstration that ankylography is experimentally feasible by obtaining a 3D image of a test object from a single 2D diffraction pattern. With further development, this approach of obtaining complete 3D structure information from a single view could find broad applications in the physical and life sciences.

Enhanced Photocatalytic Property of Reduced Graphene Oxide/TiO2 Nanobelt Surface Heterostructures Constructed by an In Situ Photochemical Reduction Method

A facile method is proposed to assemble graphene oxide (GO) on the surface of a TiO2 nanobelt followed by an in situ photocatalytic reduction to form reduced graphene oxide (rGO)/TiO2 nanobelt surface heterostructures. The special colloidal properties of GO and TiO2 nanobelt are exploited as well as the photocatalytic properties of TiO2 . Using water-ethanol solvent mixtures, GO nanosheets are tightly wrapped around the surface of the TiO2 nanobelts through an aggregation process and are then reduced in situ under UV-light irradiation to form rGO/TiO2 nanobelt surface heterostructures. The heterostructures enhance the separation of the photoinduced carriers, which results in a higher photocurrent due to the special electronic characteristics of rGO. Compared to TiO2 nanobelts, the rGO/TiO2 nanobelt surface heterostructures possess higher photocatalytic activity for the degradation of methyl orange and for the production of hydrogen from water, as well as excellent recyclability, with no loss of activity over five cycles.

High frequency complex permeability of iron particles in a nonmagnetic matrix

The effective permeability (μeff) was measured and calculated for composites consisting of micron- or submicron-sized nanocrystalline iron particles embedded in a nonmagnetic matrix. The intrinsic permeability of iron particles was obtained from the calculation for a random spatial distribution of magnetic domains and its analytical model is derived from the Landau-Lifshitz-Gilbert equation. In the calculation, each grain is assumed to be a single magnetic domain because of its nano size. The effective permeability was calculated using three methods—Bruggeman’s effective medium theory, extended Bruggeman’s effective medium theory with the consideration of the skin effect, and a simulation method which was developed in the present work. The skin effect was considered in our simulation work. Our simulation agrees well with the experimental data. Our work has shown clearly that the magnetic domain structure with a random spatial distribution of magnetic easy axes and the skin effect need to be considered to ...

Control synthesis of rutile TiO2 microspheres, nanoflowers, nanotrees and nanobelts via acid-hydrothermal method and their optical properties

Semiconductor rutileTiO2 nanostructures with a diversity of well-defined morphologies, such as microspheres, nanoflowers, nanotrees and nanobelts, are synthesized via an acid-hydrothermal process without any structure-directing agents. Their morphologies, crystal structures and orientation relationship were characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. By controlling hydrochloric acid concentration, anisotropic growth of the rutile TiO2 leads to various morphologies. The synthesis mechanism of rich TiO2 nanostructures was also studied. Finally, the relationship between optical properties and the structural complexity of the rutileTiO2 nanocrystals was characterized.

Enhanced ferroelectric-nanocrystal-based hybrid photocatalysis by ultrasonic-wave-generated piezophototronic effect.

An electric field built inside a crystal was proposed to enhance photoinduced carrier separation for improving photocatalytic property of semiconductor photocatalysts. However, a static built-in electric field can easily be saturated by the free carriers due to electrostatic screening, and the enhancement of photocatalysis, thus, is halted. To overcome this problem, here, we propose sonophotocatalysis based on a new hybrid photocatalyst, which combines ferroelectric nanocrystals (BaTiO3) and semiconductor nanoparticles (Ag2O) to form an Ag2O-BaTiO3 hybrid photocatalyst. Under periodic ultrasonic excitation, a spontaneous polarization potential of BaTiO3 nanocrystals in responding to ultrasonic wave can act as alternating built-in electric field to separate photoinduced carriers incessantly, which can significantly enhance the photocatalytic activity and cyclic performance of the Ag2O-BaTiO3 hybrid structure. The piezoelectric effect combined with photoelectric conversion realizes an ultrasonic-wave-driven piezophototronic process in the hybrid photocatalyst, which is the fundamental of sonophotocatalysis.

Optimization of Er, Yb:YCOB for CW laser operation

The erbium and ytterbium ion concentrations in the host yttrium calcium oxaborate have been optimized for diode pumped continuous-wave (CW) laser operation using spectroscopic measurements, modeling of energy transfer and population rate equation analysis, resulting in 270 mW of CW output from a diode-pumped Er,Yb:YCOB laser.

Phase transformation of TiO2 nanobelts and TiO2(B)/anatase interface heterostructure nanobelts with enhanced photocatalytic activity

TiO2 nanobelts are very attractive due to their dimensional confinement and structurally well-defined physical and chemical properties. However, the obscure phase transformation mechanism and the low photocatalytic activity of TiO2 nanobelts limit their wide applications. Here, the phase transformations among H2Ti3O7, TiO2(B), anatase and rutile nanobelts were characterized in detail by X-ray powder diffraction, high resolution transmission electron microscopy, Raman spectroscopy and UV-Vis diffuse reflectance spectra. TiO2(B) is inevitable in the phase transformation of TiO2 nanobelts due to the shape limiting effort and the similar crystal structure between H2Ti3O7 and TiO2(B). TiO2 nanobelts have a good thermal stability for the crystal phase and nanostructures. TiO2(B)/anatase interface heterostructure nanobelts were obtained by calcining H2Ti3O7 nanobelts at 800 °C, which had an enhanced photocatalytic ability comparing with pure TiO2(B) and anatase nanobelts. The mechanisms of the phase transformation of TiO2 nanobelts and the enhanced photocatalytic activity of TiO2(B)/anatase interface heterostructure nanobelts were discussed. The self-transformed heterostructure nanobelts have good photocatalytic activity, stability and easy-recovery properties, which will have important practical applications.