Real-time imaging of nanoscale electrochemical Ni etching under thermal conditions

The ability to vary the temperature of an electrochemical cell provides opportunities to control reaction rates and pathways and to drive processes that are inaccessible at ambient temperature. Here, we explore the effect of temperature on electrochemical etching of Ni–Pt bimetallic nanoparticles. To observe the process at nanoscale resolution we use liquid cell transmission electron microscopy with a modified liquid cell that enables simultaneous heating and biasing. By controlling the cell temperature, we demonstrate that the reaction rate and dissolution potential of the electrochemical Ni etching process can be changed. The in situ measurements suggest that the destabilization of the native nickel oxide layer is the slow step prior to subsequent fast Ni removal in the electrochemical Ni dissolution process. These experiments highlight the importance of in situ structural characterization under electrochemical and thermal conditions as a strategy to provide deeper insights into nanomaterial transformations as a function of temperature and potential.

The combination of electrochemical analysis, temperature control and in situ TEM imaging directly probes the etching of Ni from bimetallic Ni–Pt nanoparticles.     

Deconvolution of overlapped peaks based on the exponentially modified Gaussian model in comprehensive two-dimensional gas chromatography

Comprehensive two-dimensional gas chromatography (GC x GC) has attracted much attention for the analysis of complex samples. Even with a large peak capacity in GC x GC, peak overlapping is often met. In this paper, a new method was developed to resolve overlapped peaks based on the mass conservation and the exponentially modified Gaussian (EMG) model. Linear relationships between the calculated sigma, tau of primary peaks with the corresponding retention time (tR) were obtained, and the correlation coefficients were over 0.99. Based on such relationships, the elution profile of each compound in overlapped peaks could be simulated, even for the peak never separated on the second-dimension. The proposed method has proven to offer more accurate peak area than the general data processing method.     

Interactions with ATP, DNA Cleavage and Anti-tumor Activities of Complexes with Anions [Mo（V）O2（O2CeH4）2]^3-, [Mo（Ⅴ）0.5W（Ⅵ）0.5O2（O2C6H4）2]^2.5- and [W（Ⅵ）O2（O2C6H4）2]^2-

(NH3CH2CH2NH2)3[Mo(Ⅴ)O2(O2C6H4)2] (1), (NH3CH2CH2NH2)2.5[Mo(Ⅴ)o.sW(Ⅵ)o.502(O2C6H4)2] (2) and(NH3CH2CH2NH2)2[VC(Ⅵ)O2(O2C6H4)2] (3) were synthesized, structurally characterized by X-ray diffraction analysis, and studied on their interactions with ATP, their DNA cleavage activities and antitumor properties. The redox state of molybdenum was not changed on going from crystal to aqueous solutions in complexes 1 and 2, while tungsten underwent reduction from W(VI) to W(V) in complexes 2 and 3. ATP promoted the oxidation of both molybdenum and tungsten from M(Ⅴ) to M(Ⅵ) and the hydrolysis of catecholate ligands in solution consisting of ATP and the complexes. Complex 1 possesses fairly good activity to DNA cleavage and against tumor S180 in mice, and is more effective than the control drug cyclophosphamide under the identical conditions. However, complexes 2 and 3 exhibited marginal effectiveness. The effectiveness of anti-tumor of the complexes was related positively to their DNA cleavage activities and their hydrolysis of catecholate ligands.     

采用红外漫反射光谱研究纳米Si3N4的表面结构

采用付利叶红外漫反射光谱对激光法制取的具有不同化学组成的纳米Ｓｉ３Ｎ４粉（１５４－３０ｎｍ）的表面结构，室表面氧化及热稳定性进行了研究，结果表明新鲜的富氮粉体表面主要为硅胺基（Ｓｉ３－ｘＮＨｘ，ｘ＝１－３）结构，粉体暴露空气后硅胺基会与空气中的水分子反应形成硅醇基（ＳｉＯＨ）结构，具有不同组成的粉体随粉中氮含量的增大粒子表面硅胺基量也增加；富硅粉体表面硅胺基较少，其氧化主要为表面硅原子与空气中氧原     

晶态C60,K3C60,K6C60的能带计算

本文用紧束缚法的ＥＨＭＯ三维晶体轨道程序进行计算求得了Ｃ６０，Ｋ３Ｃ６０和Ｋ６Ｃ６０的能带结构，并得到了一系列过去未曾见过报导的原子投影态密度、轨道、原子重叠布据、原子电荷、轨道矢量等数据。从这些能带图中可以充分说明三种物质的区别，并可解释Ｋ３Ｃ６０的超导性和Ｃ６０与Ｋ６Ｃ６０的绝缘性。     

Combustion synthesis and luminescence properties of Dy-doped MgO nanocrystals

MgO nanocrystals doped with Dy³⁺ have been synthesized by a combustion method. The synthesized sample is characterized by X-ray diffraction, transmission electron micrograph, Fourier transform infrared, and photoluminescence spectroscopy. The as-prepared MgO nanocrystals appear to be single cubic crystalline phase and the diameter is in the range of 20–25 nm. The hypersensitive transition (⁴F_9/2→⁶H_13/2 of Dy³⁺) emission is prominent in the emission spectra resulting from the low-symmetry local site at which Dy³⁺ ions locate. In addition, the dependence of the luminescence intensity on Dy³⁺ concentration is also discussed.     

Optogenetic Control of Voltage‐Gated Calcium Channels

Voltage‐gated Ca²⁺ (Ca_V) channels mediate Ca²⁺ entry into excitable cells to regulate a myriad of cellular events following membrane depolarization. We report the engineering of RGK GTPases, a class of genetically encoded Ca_V channel modulators, to enable photo‐tunable modulation of Ca_V channel activity in excitable mammalian cells. This optogenetic tool (designated optoRGK) tailored for Ca_V channels could find broad applications in interrogating a wide range of Ca_V‐mediated physiological processes.     

Synergic nitrogen source route to inorganic fullerene-like boron nitride with vessel, hollow sphere, onion, and peanut nanostructures

In this paper we describe the large-scale synthesis of inorganic fullerene-like (IF-like) hexagonal boron nitride with vessel, hollow sphere, peanut, and onion structures by reacting BBr(3) with the synergic nitrogen sources NaNH(2) and NH(4)Cl at 400-450 degrees C for 6-12 h. The composition of products could be confirmed to be pure boron nitride with hexagonal structures by the XRD patterns and FT-IR, XPS, and EDXA spectra. The representative HRTEM images clearly reveal the layerlike features of the products. Here, the peanut-like structure of the IF-like BN is reported for the first time, and added to the list as one kind of new morphology of BN nanomaterials. The similarity in the structure between h-BN and graphite is responsible for the formation of IF-like BN with nanostructures of vessels, hollow spheres, peanuts, and onions.     

Correlations between gas permeation and free-volume hole properties of polyurethane membranes

A series of polyurethane films based on hard segments consisting of toluene diisocyanate and 1,4-butanediol and different soft segments consisting of hydroxyl terminated polybutadiene, hydroxyl terminated polybutadiene/styrene and hydroxyl terminated polybutadiene/acrylonitrile were synthesized by solution polymerization separately. Positron annihilation lifetimes were measured at room temperature for all samples studied. We found that both the free volume size and fractional free-volume decreased with the increase of hard segment content. On the other hand, direct relationship between the gas permeability and the free-volume has been established based on the free-volume parameters and gas diffusivity measured. Experimental results revealed that the free-volume plays an important role in determining the gas permeability.     

The effects of flow angle and shear rate within the spinneret on the separation performance of poly(ethersulfone) (PES) ultrafiltration hollow fiber membranes

The effects of dope flow rate and flow angle within a spinneret during spinning hollow fiber membranes on the morphology, water permeability and separation performance of poly(ethersulfone) ultrafiltration hollow fiber membranes were investigated. For this purpose, two spinnerets with different flow angles were designed and used. The dope solution, containing polyethersulphone (PES)/N-methyl-2-pyrrolidone (NMP)/diethylene glycol (DG) with a weight ratio of 23/41/36, which was very close to its cloud point (binodal line), was used in order to speed up the coagulation of nascent fibers so that the relaxation effect on molecular orientation was reduced. The wet-spinning process was purposely chosen to fabricate the hollow fibers without extra drawing. Therefore, the effects of gravity and elongation stress on fiber formation could be significantly reduced and the orientation induced by shear stress within the spinneret could be frozen into the wet-spun fibers. Experimental results suggest that higher dope flow rates (shear rates) in the spinneret produce UF hollow fiber membranes with smaller pore sizes and denser skin layers due to the enhanced molecular orientation. Hence, the pore size and the water permeability decrease, but the solute separation increases. Hollow fibers spun from a conical spinneret have smaller mean pore sizes with larger geometric standard deviations, thus exhibiting lower water flux and greater solute separation than hollow fibers spun from a traditional straight spinneret. In addition, SEM studies indicate macrovoids response differently for the 90° straight and 60° conical spinnerets when increasing the dope flow rate. Macrovoids can be significantly suppressed and almost disappear in the 90° spinneret at high dope flow rates. This phenomenon cannot be observed for the 60° conic spinneret.