Xuewu Ge

Fabrication of fibrous amidoxime-functionalized mesoporous silica microsphere and its selectively adsorption property for Pb2+ in aqueous solution

Fibrous cyano-modified mesoporous SiO2 microspheres with specific surface area of ca. 300 m(2) g(-1) have been successfully fabricated respectively by in-situ synthesis and post-modification methods, based on the hydrolysis of ethyl silicate in the presence of (2-cyanoethyl)triethoxysilane at a certain condition. TEM observations show that the average diameters of the prepared fibrous cyano-modified SiO2 microspheres by these two methods are 68 and 211 nm, respectively. The N2 adsorption-desorption isotherms analysis on the fibrous SiO2 microspheres show sharp peaks in the 10-20 nm range. After the cyano groups transformed to amidoxime groups, the adsorption behavior of the fibrous amidoxime-functionalized mesoporous SiO2 microspheres for Fe(3+), Cu(2+), and Pb(2+) was investigated. The results show that the prepared SiO2 microspheres can selectively adsorb Pb(2+). The maximum equilibrium adsorption capacity for Pb(2+) could reach 284 mg/g. The desorption of Pb(2+) in 2M HNO3 completes within 60 min. The efficiency of the desorption is as high as 96.2%. This work provides the methods to prepare amidoxime-functionalized SiO2 microsphere with high specific surface area and total pore volume, which has the potential to be applied as an efficient adsorbent for specific heavy metal ions.

Fabrication of Superhydrophobic Three-Dimensionally Ordered Macroporous Polytetrafluoroethylene Films and Its Application

Three-dimensionally ordered macroporous (3DOM) polytetrafluoroethylene (PTFE) has hardly been prepared due to the poor solubility in most of solvents and high melting temperature of PTFE raw material. In this work, monodispersed polystyrene (PS) microspheres and PTFE latex particles were controlled to simultaneously deposit from water. After the deposits were calcinated at 400 °C, a self-supported superhydrophobic 3DOM PTFE film with a static water contact angle of 154° was successfully fabricated. The pore size can be tunable from 1.5 to 3 μm, depending on the size of PS microspheres. The prepared 3DOM PTFE film were used as micromolds and microreactors to prepare poly(methyl methacrylate) (PMMA) particles and TiO2 macroporous material, respectively. This work provides a facile method to fabricate 3DOM PTFE materials.

A transient calorimeter pyrheliometer of high accuracy

Abstract The problems of how to improve the accuracy and keep the stability of the transient calorimeter pyrheliometer have been solved by the following methods: (i) a hemispheric mirror shell with a small hole at its top is situated over a copper disk sensor. The inner wall of the shell has high reflectivity, acting as a specular reflector. In this way, the effective absorptance of the sensor with the mirror can approach unity, and can be kept in long-term stability; (ii) a micro-computer is adopted as controller and data processor of the pyrheliometer. So the total error of the measuring system is less than 0.1%. Results of comparing our instrument with the cavity-type pyrheliometers, such as Eppley HF self-calibrating and TMI Mark-VI pyrheliometer, show that the maximum relative deviation, the average deviation, and the standard deviation are less than 0.6%, 0.12%, and 0.23%, respectively.

A novel pyrheliometer of high accuracy

Abstract In this paper, analyses have been carried out for a novel blackbody model, which is made by employing a hemispheric mirror. It is calculated that the effective absorptance of the model can approach unity by correctly choosing the coatings and the geometric parameters. Based on the analyses, a new type of absolute pyrheliometer was designed and constructed. The uncertainty of the device is indicated to be ±0.4%. Comparisons have been made with cavity-type pyrheliometers. The agreement is satisfactory.

Preliminary research in the measurement of the solar radiation by transient technique

Abstract A new technique for measuring the solar radiation is presented. It consists of measuring the heating and colling rate of the sensor of the instruments when the sensor is exposed to or shielded from the incident solar radiation. The experimental apparatus are described in the paper along with the theoretical analyses of the technique. Solar radiation data measured using the apparatus are compared with those obtained through other means. The agreement is good.

Non-invasive in vivo imaging of the ionic regimes along the gastrointestinal tract of a freshwater vertebrate model organism (Japanese medaka) using responsive photonic crystal beads

Microspherical photonic colloidal crystalline beads that are responsive to media ionic strength of cationic electrolytes have been developed for in vivo imaging of the morphology and concentration gradient of cationic electrolytes along the gastrointestinal (GI) tract of live Japanese medaka (Oryzias latipes). These responsive photonic beads were assembled from core-shell nano-sized particles with polystyrene-co-polyacrylic acid (PS-co-PAA) cores and poly(hydroxyethyl methacrylate-co-p-styrene sulfonate) (PHEMA-co-PSS) hydrogel shells. The three-dimensional orderly packing of these nano-sized core-shell particles gave rise to the photonic properties of the resultant colloidal crystalline array of microspheres. The cationic electrolyte-induced volume phase transition of the sulfonate-laden hydrogel shells of the nano-sized particles altered the lattice spacing among those particles and brought about the photonic responses of the colloidal crystalline beads. Unambiguous changes in the diffraction colour of the colloidal crystalline beads were observable under ordinary ambient light in solution media of increasing concentration of sodium chloride up to 500 mM. These photonic colloidal crystalline beads were found to possess enough structural integrity for in vivo imaging of the GI tract of live Japanese medaka. With the use of a conventional optical microscope, the gradient in the ionic strength of cationic electrolytes along the GI tract of live Japanese medaka larvae was readily revealed, with a lower electrolyte concentration in the mid-intestine (<50 mM) compared to that of the posterior-intestine (≥50 mM). Our results demonstrated the potential of stimuli-responsive photonic materials in bio-imaging applications.

Determination of Adenosine Triphosphate by a Target Inhibited Catalytic Cycle Based on a Strand Displacement Reaction

A strand displacement reaction-based system was developed for the determination of adenosine triphosphate (ATP). It involved an entropy-driven catalytic cycle that directly employed the ATP aptamer as the catalyst. Introduction of ATP into the system induced the catalyst to form the G-quadruplex conformation and inhibited its catalytic activity. All intermediates in the catalytic cycle processes were identified by polyacrylamide gel electrophoresis analysis. When the oligonucleotides were labeled with a carboxyfluorescein fluorophore and a 4-([4-(dimethylamino)phenyl]azo)benzoic acid quencher, this strand displacement reaction-based catalytic system exhibited a “switch-on” response for ATP. Conditions for detecting ATP, such as the toehold length, concentrations of the catalyst and magnesium ion, and incubation temperature, were optimized to obtain a detection limit of 50 nM and a linear response up to 1400 nM of ATP. This target inhibited catalytic cycle provides an enzyme-free biosensing strategy and has potential application in aptamer-based biosensing.