Gold Nanocages: Engineering Their Structure for Biomedical Applications

The galvanic replacement reaction between a Ag template and HAuCl₄ in an aqueous solution transforms 30–200 nm Ag nanocubes into Au nanoboxes and nanocages (nanoboxes with porous walls). By controlling the molar ratio of Ag to HAuCl₄, the extinction peak of resultant structures can be continuously tuned from the blue (400 nm) to the near‐infrared (1200 nm) region of the electromagnetic spectrum. These hollow Au nanostructures are characterized by extraordinarily large cross‐sections for both absorption and scattering. Optical coherence tomography measurements indicate that the 36 nm nanocage has a scattering cross‐section of ～ 0.8 × 10^–15 m² and an absorption cross‐section of ～ 7.3 × 10^–15 m². The absorption cross‐section is more than five orders of magnitude larger than those of conventional organic dyes. Exposure of Au nanocages to a camera flash resulted in the melting and conversion of Au nanocages into spherical particles due to photothermal heating. Discrete‐dipole‐approximation calculations suggest that the magnitudes of both scattering and absorption cross‐sections of Au nanocages can be tailored by controlling their dimensions, as well as the thickness and porosity of their walls. This novel class of hollow nanostructures is expected to find use as both a contrast agent for optical imaging in early stage tumor detection and as a therapeutic agent for photothermal cancer treatment.     

模糊模式判别在油气预测中的应用

通过对泌阳凹陷前杜楼地区北部断块 98- 1井区资料的分析 ,设立隶属函数 ,建立模糊判别模式 ,对 98- 1区的 7个砂层进行模糊判别 ,获得了较好的效果。     

GSH-assisted hydrothermal synthesis of MnxCd1−xS solid solution hollow spheres and their application in photocatalytic degradation

A series of Mn_xCd_1−xS (MCS) solid solutions hollow spheres (x=0.0, 0.20, 0.33, 0.50 and 0.67) have been synthesized with the assistance of l-Glutathione (GSH) by a simple hydrothermal route for the first time. Different characterization techniques, including X-Ray diffraction (XRD), atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller surface area (BET), UV–vis and diffuse reflectance spectra (DRS) are performed to investigate the structural and optical properties of the as-prepared samples. The experiment of rhodamine B (RhB) decoloration indicates that all the MCS samples show higher photo-catalytic activities than commercial CdS under visible light irradiation. Among them, the Mn_0.33Cd_0.67S exhibits the highest photo-catalytic activity. The superior photo-catalytic activity of MCS samples may be attributed predominantly to the synergistic effect of the appropriate band-gap structure as well as the special hollow spherical morphology which makes MCS samples have the ability to harvest exciting visible-light due to multiple scattering within the interior space. Furthermore, the Mn_0.33Cd_0.67S shows well stability, the photo-catalytic activities do not decrease significantly after six recycles. The work may open a novel strategy to fabricate multi-component chalcogenide solid solutions hollow spheres.     

Uniform Bi2S3 nanorods-assembled hollow spheres with excellent electrochemical hydrogen storage abilities

Hierarchical Bi₂S₃ hollow spheres have been synthesized by a facile solvothermal process in the presence of sodium tartrate. The hollow spheres are composed of numerous ultrathin nanorods with the average diameter of 15 nm. Based on the time dependent electron microscope observations, the formation mechanism of such hierarchical structures has been proposed as a sodium tartrate directed self-assembled process and oriented attachement mechanism. The morphology and size of the subunits can be controlled by adjusting the amount of sodium tartrate. The Nitrogen adsorption-desorption measurements suggest that mesopores exist in these hollow spheres. The as-derived Bi₂S₃ hollow spheres exhibit excellent electrochemical hydrogen storage properties.     

Characteristic of rotating detonation wave in the H2/Air hollow chamber with Laval nozzle

To pinpoint the relationship between high frequency tangential instability(HFTI) and continuous rotating detonation (CRD), series of H₂/Air rotating detonations are experimentally achieved in the hollow chamber with Laval nozzle. The contraction ratio of the nozzle has a significant effect on the detonation. The detonation waves number increases with the increasing of equivalence ratio (ER) or nozzle contraction ratio. Based on its character, a new type of detonation is defined as two dominant peak one wave mode (TDPO). The velocities of detonation waves propagating in this new mode are larger than the Chapman-Jouguet (CJ) theoretic value. On the assumption that the reflection wave is rotated with the detonation wave, this mode is well illustrated. The forming process of two waves is also given. The results show that the appearance of combustion mode is relative to the reflection wave generated at the contraction section of the nozzle. The inner mechanism of the refection wave is illustrated. These works make a foundation to investigate the relationship between rotating detonation and tangential instability.     

Simulation study on horizontal continuous casting process of copper hollow billet under rotating electromagnetic stirring Part 1—model description and primary results

In this paper, a comprehensive three-dimensional mathematical model is built to investigate the effect of rotating electromagnetic stirring on solidification process of copper hollow billet during horizontal continuous casting. The finite element package ANSYS and the commercial finite volume package FLUENT are employed for simulating electromagnetic field and thermal flow field respectively. The Lorenz force and Joule heat are transferred between them with a special data communication method. The model involves the solution of Maxwell equations, Navier—Stokes equations and energy equation for the turbulence characteristics κ and ?. The measured magnetic flux density is used for validating the proposed model. The simulated results show that rotating electromagnetic stirring causes a swirling motion in the hollow billet and makes the temperature field uniform. In the present study, the temperature gradient decreases from 748 to 196 K m^?1, and the sump depth is reduced from 48·8 to 29·0 mm.     

Solution blow spun nickel oxide/carbon nanocomposite hollow fibres as an efficient oxygen evolution reaction electrocatalyst

The development of efficient electrocatalysts for slow reaction of the oxygen evolution reaction (OER) is fundamental for viability of the electrochemical water splitting technologies. Here we report for the first time the synthesis of NiO/carbon hollow fibres (NiO-HF) by the Solution Blow Spinning (SBS) technique, and a study of their catalytic activity towards the OER in alkaline medium. The hollow fibres were obtained with ca. 300 nm in diameter consisting of agglomerated NiO nanoparticles with an average size of 50 nm which is close to the tubular wall thickness. The formation mechanism of the hollow structure was discussed. It was revealed that the carbon from polyenic branch of polyvinylpyrrolidone (PVP) resists the firing treatment and acts as an agglomerating agent, thus ensuring a conductive and percolating path between NiO nanoparticles along the fibres. A battery of electrochemical tests of NiO-HF supported by commercial Ni foam reveals excellent electrochemical activity for OER in 1 M KOH, in comparison with reference NiO nanoparticles (NiO-NP, diameter ca. 23 nm). NiO-HF attains an overpotential of 340 mV vs. RHE at a current density of 10 mA cm⁻², which is amongst the lowest values reported in the literature for undoped NiO. Chronopotentiometry reveals stable NiO-HF electrodes over 15 h under an electrolysis current of 25 mA cm⁻². Microscopic analysis shows that the fibrillar morphology is completely preserved after the electrolysis test. The remarkable performance of the NiO-HF catalyst is ascribed to the enhanced electronic conductivity resulting from the interpenetrating NiO-HF/carbon microstructure.     

One-pot synthesis of hematite-alumina hollow sphere composite by ultrasonic spray pyrolysis technique with high adsorption capacity toward PAHs

A hybrid nanocomposite of alumina and hematite was synthesized by ultrasonic spray pyrolysis technique. The study of microscopic images, mapping analysis, and XRD patterns revealed that the Al₂O₃ – Fe₂O₃ nanocomposite was composed of separated spherical particles with a thin layer ball-shaped structure that metal oxides are uniformly distributed in the wall of hollow sphere particles, led to a coherent and monotonous construction. A series of coefficients of equilibrium sorption of polycyclic aromatic hydrocarbons (PAHs) as hazardous materials were measured on the prepared composite material in a batch technique. The free or pure Al₂O₃ or Fe₂O₃ showed negligible removal efficiency for the mentioned analytes. The various significant variables, such as initial analyte concentration, solution pH, adsorbent dose, and contact time to remove analyte, were studied in the aqueous solutions. Adsorption data were modeled to Langmuir, Freundlich, and Temkin isotherms, and a good correlation found in the case of Langmuir isotherm and adsorption capacity for anthracene, phenanthrene, and naphthalene were 370, 333, and 322 mg g^?1, respectively. Investigation of the kinetic models proved a pseudo-second-order, and the prepared adsorbent can be reused more than 7 times without a significant decrease of adsorption performance.     

pH-responsive drug delivery system based on hollow silicon dioxide micropillars coated with polyelectrolyte multilayers

We report on the fabrication of polyelectrolyte multilayer-coated hollow silicon dioxide micropillars as pH-responsive drug delivery systems. Silicon dioxide micropillars are based on macroporous silicon formed by electrochemical etching. Due to their hollow core capable of being loaded with chemically active agents, silicon dioxide micropillars provide additional function such as drug delivery system. The polyelectrolyte multilayer was assembled by the layer-by-layer technique based on the alternative deposition of cationic and anionic polyelectrolytes. The polyelectrolyte pair poly(allylamine hydrochloride) and sodium poly(styrene sulfonate) exhibited pH-responsive properties for the loading and release of a positively charged drug doxorubicin. The drug release rate was observed to be higher at pH 5.2 compared to that at pH 7.4. Furthermore, we assessed the effect of the number of polyelectrolyte bilayers on the drug release loading and release rate. Thus, this hybrid composite could be potentially applicable as a pH-controlled system for localized drug release.     

Jute and hollow conjugated polyester composites for outdoor & indoor insulation applications

The research work aims at investigating the fitness of jute and hollow conjugated polyester (HCP) composites for indoor and outdoor applications. Limiting oxygen value index, natural weathering exposure was done on four optimized composite structures; i) sandwich structure composite (A); ii) blended non-woven structure composite (B); iii) multiple layers with 5% of low melt polyester added composite (C); (iv) multiple layers of non-woven stitched composite (D) were produced. Their tensile strength, strain at break, and Young’s modulus values were evaluated both before and after the coating of acrylic-based silicon emulsion (ASE). From the experimental results, it is suggested that sample A can be used for an interior trim, sample B can be a base material for interior designing, sample C can replace the usage of wood, plastics, metals, and alloys in hardware applicationsand sample D can be used in interiors as an insulation material in commercial buildings for the purpose of internal cooling or heating.