α-Fe_2O_3 immobilized benzimidazolium tribromide as novel magnetically retrievable catalyst for one-pot synthesis of highly functionalized piperidines

Nanostructured α-Fe_2O_3 were prepared by precipitation followed by calcination method.Cetyltrimethylammonium bromide(CTAB) was used as surfactant.The nano α-Fe_2O_3 was then silanized with(3-chloropropyl)-triethoxysilane(CPTES) by room temperature mixing of α-Fe_2O_3 and CPTES to produce silane coated α-Fe_2O_3(ClPr-Si@Fe_2O_3).As-synthesized ClPr-Si@Fe_2O_3 was functionalized via covalent grafting of benzimidazole to produce 3-(l-benzimidazole)Pr-Si@Fe_2O_3.This was further reacted with bromine to afford α-Fe_2O_3 immobilized benzimidazolium tribromide(α-Fe_2O_3-BIM tribromide).This ionic liquid(IL)α-Fe_2O_3 BIM tribromide was characterized by FT-IR,XRD,TEM,SEM,TGA,VSM,EDX and BET analysis.The as-synthesized IL tribromide was used as catalyst for one-pot synthesis of highly substituted piperidines.The method is greener in terms of solvent selection,recovery of the catalyst and efficiency.     

Porous α-Fe_2O_3/SnO_2 nanoflower with enhanced sulfur selectivity and stability for H_2S selective oxidation

Being abundant and active,Fe_2O_3 is suitable for selective oxidation of H_2S.However,its practical application is limited due to the poor sulfur selectivity and rapid deactivation.Herein,we report a facile template-free hydrothermal method to fabricate porous α-Fe_2O_3/SnO_2 composites with hierarchical nanoflower that can obviously improve the catalytic performance of Fe_2O_3.It was disclosed that the synergistic effect between α-Fe_2O_3 and SnO_2 promotes the physico-chemical properties of α-Fe_2O_3/SnO_2 composites.Specifically,the electron transfer between the Fe~(2+)/Fe~(3+) and Sn~(2+)/Sn~(4+) redox couples enhances the reducibility of α-Fe_2O_3/SnO_2 composites.The number of oxygen vacancies is improved when the Fe cations incorporate into SnO_2 structure,which facilitates the adsorption and activation of oxygen species.Additionally,the porous structure improves the accessibility of H_2 S to active sites.Among the composites,Fe1 Sn1 exhibits complete H_2 S conversion with 100% sulfur selectivity at 220℃,better than those of pure α-Fe_2O_3 and SnO_2.Moreover,Fe1 Sn1 catalyst shows high stability and water resistance.     

溶胶凝胶法合成莫来石纳米带

Single-crystal mullite nanobelts were prepared by a simple sol-gel method using WO₃ as additive, and nanobelts were straight and uniform with width of 200 nm and length of 3~4 μm. The as-prepared products were characterized with XRD, SEM and TEM and the nanobelt formation mechanism was also discussed. The interphase of aluminium tungstate acted as seed crystals or epitaxial templates during the formation of nanobelts. The further experiments showed that there was a strong correlation between the formation of nanobelts and the presence of WO₃.     

Synthesis and Gas-sensing Performance of Nanosized SnO2

Nanosized tin dioxide particles were prepared by sol-gel dialytic processes with tin(Ⅳ) chloride and alcohol as start materials. The nanoparticles of tin dioxide were charactered by thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET. The results show that the average diameter of tin dioxide particles dried at 353 K was about 2nm. Even if the tin dioxide particles were calcined at 873 K, the average diameter of particles was less than 10 nm. The removal of Cl^- was solved by using this kind of method. The mechanism of the formation of tin dioxide nanosized particles was proposed and analyzed in this paper. We also measured the sensitivity of the sensor based on the tin oxide powder calcined at 673K to NH3, alcohol, acetone, hexane and CO. The gas-sensing performance results indicate that this sensor has a higher sensitivity to alcohol and acetone, and selectivity for NH3, hexane and CO at an operating temperature of 343 K.     

Efficient nonenzymatic hydrogen peroxide sensor in acidic media based on Prussian blue nanoparticles-modified poly(o-phenylenediamine)/glassy carbon electrode

The Prussian blue nanoparticles(PBNPs) were prepared by a self-assembly process, on a glassy carbon(GC) electrode modified with a poly(o-phenylenediamine)(Po PD) film. The stepwise fabrication process of PBNPs-modified Po PD/GCE was characterized by scanning electron microscopy(SEM) and electrochemical impedance spectroscopy. The prepared PBNPs showed an average size of 70 nm and a homogeneous distribution on the surface of modified electrodes. The PBNPs/Po PD/GCE showed adequate mechanical, electrochemical stability and good sensitivity in comparison with other PB based H_2O_2 sensors. The present modified electrode exhibited a linear response for H_2O_2 reduction over the concentration range of 1–58.22 mmol L ~(-1)with a detection limit of ca. 0.8 mmol L ~(-1)(S/N = 3), and sensitivity of 3187.89 m A(mol L ~(-1)) ~(-1)cm 2using the amperometric method. This sensor was employed for the H_2O_2 determination in real sample and also exhibited good interference resistance and selectivity.     

Catalytic Hydrogenation of Nitrobenzene to Aniline by Ag/γ-Fe_2O_3

The Ag/γ-Fe_2O_3 nanocomposite was synthesized by solvothermal reduction method via using ferric nitrate and silver nitrate as raw materials, and ethylene glycol as the reducing agent. The composite was characterized by X-ray powder diffraction, scanning electron microscope, transmission electron microscope, and energy dispersive X-ray. The prepared Ag/γ-Fe_2O_3 was used for the catalytic hydrogenation of nitrobenzene to aniline by hydrazine hydrate. The factors such as the silver content in the catalyst, reaction time, reaction temperature and the regeneration of catalyst were investigated. The results showed that the yield of aniline reached 100% by utilizing the 1%wt(nitrobenzene) Ag/γ-Fe_2O_3 for the catalytic hydrogenation of nitrobenzene for 3 h to obtain aniline at 78 ℃, hydrazine hydrate as the hydrogen source, while the silver content in the catalyst was 3%mol.     

Effect of initial nickel particle size on stability of nickel catalysts for aqueous phase reforming

The deactivation behavior by crystallite growth of nickel nanoparticles on various supports(carbon nanofibers, zirconia, Si C, α-Al_2O_3 and γ-Al_2O_3) was investigated in the aqueous phase reforming of ethylene glycol. Supported Ni catalysts of ~10 wt% were prepared by impregnation of carbon nanofibers(CNF),Zr O_2, SiC, γ-Al_2O_3 and α-Al_2O_3. The extent of the Ni nanoparticle growth on various support materials follows the order CNF ~ ZrO_2 SiC γ-Al_2O_3 α-Al_2O_3 which sequence, however, was determined by the initial Ni particle size. Based on the observed nickel leaching and the specific growth characteristics; the particle size distribution and the effect of loading on the growth rate, Ostwald ripening is suggested to be the main mechanism contributing to nickel particle growth. Remarkably, initially smaller Ni particles(~12 nm) supported on α-Al_2O_3 were found to outgrow Ni particles with initially larger size(~20 nm). It is put forward that the higher susceptibility with respect to oxidation of the smaller Ni nanoparticles and differences in initial particle size distribution are responsible for this behavior.     

Cobalt oxide and carbon modified hematite nanorod arrays for improved photoelectrochemical water splitting

Given the proper band gap, low cost and good stability, hematite(α-Fe_2O_3) has been considered as a promising candidate for photoelectrochemical(PEC) water splitting, however suffers from the sluggish surface water oxidation reaction kinetics. In this study, a simple dip-coating process was used to modify the surface of α-Fe_2O_3 nanorod arrays with cobalt oxide(CoO_x) and carbon(C) for the improved PEC performance, with a photocurrent density at 1.6 V(vs. reversible hydrogen electrode, RHE) increased from 0.10 mA/cm~2 for the pristine α-Fe_2O_3 to 0.37 mA/cm~2 for the CoO_x/C modified α-Fe_2O_3 nanorods. As revealed by electrochemical analysis, thanks to the synergistic effect of CoO_x and C, the PEC enhancement could be attributed to the enhanced charge transfer ability, decreased surface charge recombination, and accelerated water oxidation reaction kinetics. This study serves as a good example for improving PEC water splitting performance via a simple method.     

EFFECTS OF K_2O AND MnO PROMOTERS ON THE PRODUCTION OF LIGHT ALKENES VIA SYNGAS OVER Fe/SILICALITE-2 CATALYST IL REDUCIBILITY OF K-Fe-MnO/SILICALITE-2 CATALYST

K_2O and MnO are two kinds of necessary promoters to theselective production of light alkenes from CO hydrogenation over silicalite-2(Si-2) zeolite supported Fe catalyst. The addition of both K_2O and MnOpromoters into Fe/Si-2 catalyst leads to a remarkable increase in the COconversion and the selectivity to light oletins. Silicalite-2 zeolite as Fe-MnOcatalyst support can suppress the formation of α-Fe_2MnO_3 or/andα-Fe_(2-y)Mn_yO_3 as Well as α-Fe_2O_3 and/or α-Mn_2O_3, being favorable for(?)ncreasing the dispersion of active metal component. So MnO can promotethe reduction of Fe~(3-) and enhance the capacity of CO adsorption, which canimprove the activity of the activity of the catalyst for CO hydrogenation. While K_2Opromoter is unfavorable for reduction of Fe~(3-) to some degree with formation of Fe~(2-) as a new species after reduction. However, K_2O promoter can enhance the capacity and strength of CO adsorption greatly.So K_2O can alsoimprove the activity of catalyst for CO hydrogenation.     

Preparation of porous α-Fe2O3-supported Pt and its sensing performance to volatile organic compounds

Porous α-Fe2O3 was synthesized by a simple hydrothermal treatment of FeCl3 aqueous solution followed by a calcination process. In the synthesis of porous α-Fe2O3, no templates or pore-directing agents were used. The as-prepared porous α-Fe2O3 was further employed as a support for loading Pt nanoparticles. The gas sensing performance of the obtained porous α-Fe2O3-supported Pt to VOCs was investigated. The sensor presented a high response and fast response-recovery characteristic to several VOCs including acetone, ether, methanol, ethanol, butanol and hexanol. Meanwhile, it exhibited a much higher response than the pure α-Fe2O3 at the operating temperature of 260°C. The enhanced sensing properties may be related to the unique porous structure of the α-Fe2O3 support and the promoting effect of active Pt nanoparticles for the sensing reactions.     

N-doped coaxial CNTs@a-Fe_2O_3@C nanofibers as anode material for high performance lithium ion battery

N-doped coaxial CNTs@α-Fe_2O_3@C nanofibers have been successfully synthesized according to a facile solvothermal/hydrothermal method.The obtained CNTs@α-Fe_2O_3@C nanofibers composites exhibited special three-dimensional(3-D)network structure,which endows they promising candidate for anode materials of lithium ion battery.The coaxial property of CNTs@α-Fe_2O_3@C nanofibers could significantly improve the cycling and rate performance owing to the acceleration of charge/electron transfer,improvement of conductivity,maintaining of structural integrity and inhibiting the aggregation.Theα-Fe_2O_3nanoparticles with small size and high percentage of N-doped amount could further improve the electrochemical performance.As for the CNT@α-Fe_2O_3@C nanofibers,the capacity presented a high value of1255.4 mAh/g at 0.1 C,and retained at 1213.4 mAh/g after 60 cycles.Even at high rate of 5 C,the capacity still exhibited as high as 319 mAh/g.The results indicated that the synthesized N-doped coaxial CNTs@α-Fe_2O_3@C nanofibers exhibited high cycling and rate performance.     

A facile construction of heterostructured ZnO/Co_3O_4 mesoporous spheres and superior acetone sensing performance

The rapid development of internet and internet of things brings new opportunities for the expansion of intelligent sensors,and acetone as a major disease detection indicator(i.e.,diabetes) making it become extremely important clinical indicator.Herein,uniform mesoporous ZnO spheres were successfully synthesized via novel formaldehyde-assisted metal-ligand crosslinking strategy.In order to adjust the pore structure of mesoporous ZnO,various mesoporous ZnO spheres were synthesized by changing weight percentage of Zn(NO_3)_2·6 H_2 O to tannic acid(TA).Moreover,highly active heterojunction mesoporous ZnO/Co_3 O_4 has been fabricated based on as-prepared ultra-small Co_3 O_4 nanocrystals(ca.3 nm) and mesoporous ZnO spheres by flexible impregnation technique.Profit from nano-size effect and synergistic effect of p-n heterojunction,mesoporous ZnO/Co_3 O_4 exhibited excellent acetone sensing performance with high selectivity,superior sensitivity and responsiveness.Typically,5 wt% Co_3 O_4 embedded mesoporous ZnO sphere showed prominent acetone response(ca.46 for 50 ppm),which was about 11.5 times higher than that in pure ZnO sensing device,and it was also endowed high cyclic stability.The nanocrystals embedded hybrid material is expected to be used as promising efficient material in the field of catalysis and gas sensing.     

Structural and micro structural studies of PbO-doped SnO2 sensor for detection of methanol,propanol and acetone

In the present work the structural information of PbO-doped SnO2 thick film sensor has been investigated with X-ray diffractometer (XRD) and scanning electron microscope (SEM). Initially, SnO2 powder was derived using sol-gel process and was subsequently doped with PbO and ground up to nanosized particles. A suitable gas sensor structure was fabricated on 1′′×1′′ alumina substrate using thick film technology. The necessary paste for screen printing was also developed. SEM results showed sol-gel derived powder gets more agglomerated in the thick film form. The sensitivity of the sensor has been investigated at different temperatures (150 ?C?350 ?C) upon exposure to methanol, propanol and acetone, yielding a maximum at 250 ?C for acetone with 1 wt% PbO-doping while at 350 ?C for propanol with 3 wt% PbO-doping of the sensor. The reduction of particle size to nanometers (validated through XRD) leads to a dramatic improvement in sensitivity of sensors for the chosen organic vapors. The results also correlate well with the microstructural properties of the material and the dopant.     

Enhancement of H2 Sensing Properties of In2O3-based Gas Sensor by Chemical Modification with SiO2

The sensitivity and selectivity to H2 of a new In203-based gas sensor were improved significantly by surface chemical modification. A dense layer of SiO2 near the surface of the porous In2O3 bead was formed by chemical vapor deposition (CVD) of diethoxydimethysilane (DEMS). The dense layer functioned as a molecular sieve, thereby the diffusion of gases with large molecular diameters, except for 1-12, was effectively controlled, resulting in a prominent selectivity and high sensitivity for H2. The working mechanism of the sensor was also presented.     

Synthesis of Cu_2O nanobelts via surfactant-assisted polyol method

The synthesis of nanostructured Cu₂O was conducted in a non-aqueous solution via polyol method at a temperature of 130℃.It was found that the formation of Cu₂O nanobelts was heavily dependent on the presence of surfactant cetyltrimethylammonium bromide（CTAB）.Cu₂O nanobelts with 100-400 nm in width and several micrometers in length were only observed when CTAB was used,whereas in other cases where CTAB was absent or CTAB was replaced with polyvinylpyrrolidone（PVP K-30）,only spherical or cube-like particles were formed.The formation mechanism of Cu₂O nanobelts was discussed.     

The Mobility of Threaded α-Cyclodextrins in PR Copolymer and Its Influences on Mechanical Properties

The methylated polyrotaxane(Me PR) copolymer was prepared via the methylation of hydroxyl of threaded α-cyclodextrin(α-CDs) in polyrotaxane(PR) copolymer by CH_3I/Na H. Its structure was characterized by GPC, IR and NMR. The WXRD and TGA measurements showed the destruction of channel-like crystalline structure in Me PR copolymer. The sliding of threaded α-CDs along PEG axis in PR and Me PR copolymers was demonstrated by their dielectric spectra that also evidenced the presence of rotating of threaded α-CDs around PEG axis in Me PR copolymer. The frequent and vigorous molecular mobility in Me PR and PR copolymers was also verified by dynamic mechanical analysis(DMA) and rheological measurement, which was possibly assigned to the sliding and rotating of threaded α-CDs. DMA and rheological results showed that the mobility of α-CDs could simultaneously strengthen and toughen PR copolymer proved by stress-stain curves. In this paper, we report the CD mobility in PR and Me PR copolymers. The macroscopic behaviors of PR copolymer, such as mechanical properties in solid state, were also found to be benefited from CD mobility.     

Immunosensor Based on Surface Plasmon Resonance for Antigen Recognition

A novel immunosensor based on surface plasmon resonance（SPR） has been developed for the recognition of antigen. The sensor was designed on the basis of the fixed angle of incidence and measuring the reflected intensities in a wavelength range of 430--750 nm in real-time. An ultra-bright white light-emitting diode（LED） was used as the light source. Molecular self-assembling in solution was used to form the sensing membrane on gold substrate. It has been seen that the sensitivity of the SPR sensor with 3-mercaptopropionic acid（MPA）/protein A（SPA） sensing membrane is considerably higher than that with MPA or SPA modified sensing membrane. The kinetic processes on the sensing membrane were studied. The human B factor（Bf）, an activator of complement 3（C3）, was recognized among the other antigens. This sensor can also be used for other antigen/antibody or adaptor/receptor recognition. Under optimized experimental conditions, the sensor has good selectivity, repeatability, and reversibility.     

Dehydrogenation activities of highly dispersed transition metal oxides on NaY zeolite

Highly dispersed α-Fe_2O_3/NaY,NiO/NaY,and CuO/NaY catalyst systems were pre-pared by impregnation method.Dispersion thresholds of the transition metal oxides on NaY" zeolitewere determined by XRD phase analysis.The dispersion capacities of the transition metal oxides on NaYzeolite are much lower than that estimated on the basis of a closed packed monolayer in the micropores.The catalytic activity and selectivity of the highly dispersed oxide catalyst systems for ethylben-zene and cyclohexane dehydrogenation reactions were reported.     

纳米二氧化硅负载FeCl3作为一种高效多相催化剂用于合成1,2,4-三嗪衍生物（英文）

The one‐pot synthesis of a series of 1,2,4‐triazines from the reactions of semicarbazide or thiosemi‐carbazide with various α,β‐dicarbonyl compounds under reflux conditions in a EtOH‐H2O (9:1) mixture as solvent and catalyzed by nano‐sized silica supported FeCl3 (FeCl3@SiO2) was investigat‐ed. The FeCl3 content of the catalyst was measured by atomic absorption to get the adsorption ca‐pacity. The reactions gave high yields of the product and the catalyst was easily separated and re‐used for successive reaction runs without significant loss of activity.