首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 38 毫秒
1.
In the work, we propose an efficient one-pot approach for synthesis of a new type of mesoporous silica nanoparticles (MSNs). That can be successfully realized by using tetraethylorthosilicate (TEOS) and N-[3-(trimethoxysilyl)propyl]ethylenediamine (TSD) as the silica precursors and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent through a facile assembly process. The as-synthesized MSNs possess a spherical morphology with about 230 nm, a relatively high surface area of 133 m2/g, and a hierarchical pore size distribution. When applied as the sorbents, the amine-functioned MSNs demonstrate the enhanced adsorption capacity for CO2 capture (at 1 bar, 15 vol% CO2, up to 80.5 mg/g at 75 °C), high selectivity, and good cycling durability, benefiting from the suitable modification of polyethyleneimine.  相似文献   

2.
侯文华  马军  陈静  颜其洁 《中国化学》1999,17(6):690-692
Europium hydroxide particles with an average diameter of 10 run and a BET surface area of 127 m2 /g have been prepared by controlled precipitation in the polyoxyethylene octylphenol (Triton X-100) (hex-anol)/cyclohexane/water microemulsion system. After calcination in air at 750℃, the obtained europium hydroxide particles were readily converted to the nanosize Eu2O3 particles with an average size of 30 nm and a high BET surface area of 36.5 m2/g.  相似文献   

3.
Highly uniform, porous β-Co(OH)2 nanostructures with an appearance reminding of certain spherical corals were synthesized via a facile, one-step hydrothermal route using ethanol-water mixtures as solvents. The rough surfaces of the nanostructures consist of numerous randomly distributed, interconnecting nanoflakes, resulting in a network-like structure with many cavities. The coral-like product has a high Brunauer-Emmet-Teller specific surface area of 163 m2/g. The diameter of the coral-like β-Co(OH)2 nanostructures is adjustable from 800 nm to 2 μm. The effects of the ethanol/water ratio, the Co2+ concentration, the hydrothermal temperature, and the reaction time on the formation of the coral-like structures were investigated. Cyclic voltammetry and galvanostatic charge-discharge tests show that the β-Co(OH)2 possesses excellent capacitive properties. This is mainly attributed to the high porosity, which allows a deep penetration by electrolytes.  相似文献   

4.
It was shown for the example of the Si(OC2H5)4/(CH3O)3Si(CH2)3SH system that successively increasing the fraction of tetraethoxysilane in it (from 1: 1 to 5: 1 (mol)) successively decreased the content of 3-mercaptopropyl groups in xerogels synthesized by the sol-gel method (in the presence of methanol as a solvent and fluorine ions as a catalyst) from 5.0 to 1.9 mmol/g, whereas the specific surface area of such xerogels simultaneously increased from 13 to 631 m2/g. The sorption volume of pores also increased, their mean diameter varying insignificantly. The mean diameter of pores (2.2–2.5 nm) was close to the boundary between meso-and micropores, which was in agreement with the form of nitrogen adsorption isotherms (type I according to the IUPAC classification). It was shown by scanning electron microscopy that virtually nonporous xerogels formed at a 1: 1 ratio between alkoxysilanes consisted of spherical partially united particles 2.5–3 μm in diameter. All the 3-mercaptopropyl groups of this and other samples were, however, accessible to silver(I) ions. It follows that these groups are situated in the surface layer of xerogels. The number of thiol groups per 1 nm2 of the surface of nonporous xerogels was 1.7–7.0 groups/nm2 and depended on the ratio between reacting alkoxysilanes and s sp.  相似文献   

5.
ZrO2 nanoparticles were synthesized through arc discharge of zirconium electrodes in deionized (DI) water. X-ray diffraction (XRD) analysis of the as prepared nanoparticles indicates formation a mixture of nanocrystalline ZrO2 monoclinic and tetragonal phase structures. Transmission electron microscopy (TEM) images illustrate spherical ZrO2 nanoparticles with 7–30 nm diameter range, which were formed during the discharge process with 10 A arc current. The average particle size was found to increase with the increasing arc current. X-ray photoelectron spectroscopy (XPS) analysis confirms formation of ZrO2 at the surface of the nanoparticles. Surface area of the sample prepared at 10 A arc current, measured by BET analysis, was 44 m2/g. Photodegradation of Rhodamine B (Rh. B) shows that the prepared samples at lower currents have a higher photocatalytic activity due to larger surface area and smaller particle size.  相似文献   

6.
A series of composites containing 2.5–21.0% NiO on a surface of macroporous silica is synthesized. The specific surface area of the composites measured by the thermal desorption of nitrogen decreases with an increase in the NiO content from 24 for the original silica carrier to 16 m2/g the for composite containing 21.0% NiO. The basic dye, methylene blue (MB), is only adsorbed on SiO2 in water solutions, while acid blue anthraquinone (ABA) is only adsorbed on the NiO. The effective specific surface area Seff and effective diameters D eff of NiO nanoparticles are calculated from the adsorption isotherms of ABA on NiO composites and on NiO synthesized without a carrier. S eff of NiO nanoparticles decreases from 76 to 42 m2/g and D eff increases from 8 to 14 nm with rising NiO content in the composites. The NiO nanoparticles synthesized without a carrier are characterized by the lowest S eff (30 m2/g) and the largest D eff (20 nm).  相似文献   

7.
Nanocrystalline Mo2C powders were successfully synthesized at 500 °C by reacting molybdenum chloride (MoCl5) with C (graphite or carbon nanotube) in metallic sodium medium. X-ray powder diffractometer (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscope (XPS) and surface area analyzer (BET method) were used to characterize the samples. Experiments reveal that the carbon source used for the carbide synthesis has a great effect on the particle size and the surface area of the samples. When micro-sized graphite was used as C source the obtained nanocrystalline Mo2C powder consists of particles of 30∼100 nm, with a surface area of 2.311 m2/g. When carbon nanotubes were used as C source, the as-synthesized Mo2C sample is composed of particles of 20∼50 nm, with a surface area of 23.458 m2/g, which is an order of magnitude larger than that of the carbide prepared from the graphite.  相似文献   

8.
Resorcinol and formaldehyde were used as carbon precursors, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer was employed as a soft template, and tetraethylorthosilicate-generated silica was used as hard templates to synthesize spherical mesoporous carbon. The resulting spherical mesoporous carbons were characterized by nitrogen adsorption–desorption isotherms and electron microscopy (SEM and TEM) and used as electrode materials for aqueous electric double-layer capacitors. The average diameters of spherical particles ranged from 2 to 7 μm and the mesopore was ca 2 nm. The highest specific surface area of 1,000 m2/g and mesopore volume of 0.86 cm3/g was obtained. The specific capacitance of 130 F/g was obtained by means of galvanostatic charging/discharging and cycle voltammetry.  相似文献   

9.
The study is concerned with synthesizing copper oxide nanoparticles with leaf extract Eucalyptus Globoulus. The results of scanning electron microscopy (SEM) and dynamic light scattering (DLS) revealed that the green synthesized copper oxide nanoparticles are spherical and have a mean particle size of 88 nm, with a negative zeta potential of ?16.9 mV. The XRD graph showed the crystalline and monoclinic phases of CuO nanoparticles. The average crystalline size around 85.80 nm was observed by the Debye–Scherrer formula. The adsorption characteristics of the nano-adsorbents were investigated using methyl orange, and the adsorption efficiency at room temperature attained 95 mg/g. Copper oxide nanoparticles (CuO NPs) adsorb methyl orange dye most effectively at pH 4.5 when the dye is applied in quantities of 0.04 g/50 mL. Box–Behnken design (BBD) in response surface methodology (RSM) was used to optimize various process parameters, such as pH solution (X1: 2 – 11), adsorbing dose (X2: 0.01 – 0.08 g/L), [MO] dye concentration (X3: 10 – 80 mg/L). Overall, the adjusted coefficient of determination (R2) value of 0.99 demonstrated that the used model was quite appropriate, and the chosen RSM was effective in optimization the decolorization conditions of MO.  相似文献   

10.
Double-scale composite lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (PZT) thin films of 360 nm thickness were prepared by a modified composite sol-gel method. PZT films were deposited from both the pure sol and the composite suspension on Pt/Al2O3 substrates by the spin-coating method and were sintered at 650°C. The composite suspension formed after ultrasonic mixing of the PZT nanopowder and PZT sol at the powder/sol mass concentration 0.5 g mL−1. PZT nanopowder (≈ 40–70 nm) was prepared using the conventional sol-gel method and calcination at 500°C. Pure PZT sol was prepared by a modified sol-gel method using a propan-1-ol/propane-1,2-diol mixture as a stabilizing solution. X-ray diffraction (XRD) analysis indicated that the thin films possess a single perovskite phase after their sintering at 650°C. The results of scanning electron microscope (SEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and transmission electron microscopy (TEM) analyses confirmed that the roughness of double-scale composite PZT films (≈ 17 nm) was significantly lower than that of PZT films prepared from pure sol (≈ 40 nm). The composite film consisted of nanosized PZT powder uniformly dispersed in the PZT matrix. In the surface micrograph of the film derived from sol, large round perovskite particles (≈ 100 nm) composed of small spherical individual nanoparticles (≈ 60 nm) were observed. The composite PZT film had a higher crystallinity degree and smoother surface morphology with necklace clusters of nanopowder particles in the sol-gel matrix compared to the pure PZT film. Microstructure of the composite PZT film can be characterized by a bimodal particle size distribution containing spherical perovskite particles from added PZT nanopowder and round perovskite particles from the sol-matrix, (≈ 30–50 nm and ≈ 100–120 nm), respectively. Effect of the PZT film preparation method on the morphology of pure and composite PZT thin films deposited on Pt/Al2O3 substrates was evaluated.  相似文献   

11.
Mesoporous MgO was obtained via the hydrothermal synthesis using both ionogenic and non-ionogenic surfactants as structure-directing templates. The materials prepared were characterized by SEM, BET-N2, XRD, and TG-DTA techniques. MgO particles are spherical 20-μm aggregates of primary oxide particles well shaped as rectangular parallelepipeds. Magnesium oxide samples have the specific surface area of 290–400 m2/g and pore sizes of 3.3–4.1 nm. Their mesoporous structure remained unchanged after calcination up to 350°C. Catalytic activity of mesoporous MgO was studied in acetone condensation reaction.  相似文献   

12.
The thermolysis of Zr(BH4)4 vapor at 573 and 623 K in a vacuum of 1.33 × 10−1 Pa was studied. Nanosized zirconium diboride was produced as an X-ray amorphous powder and a crystalline film. According to electron microscopy data, the X-ray amorphous zirconium diboride powder obtained at 573 or 623 K consists of spherical particles 30–40 nm in diameter, which is in quite a good agreement with the equivalent particle diameter (∼35 nm) calculated from the specific surface area of ZrB2. After annealing at 1273 K, the X-ray amorphous zirconium diboride powder crystallizes into a hexagonal lattice with the unit cell parameters a = 0.3159 nm and c = 0.3527 nm. The coherent scattering length D hkl is ∼27 nm. The zirconium diboride film produced at 573 or 623 K crystallizes into a hexagonal lattice with the unit cell parameters a = 0.3163−0.3168 nm and c = 0.3524−0.3531 nm. The coherent scattering length D hkl is ∼14 nm. The thickness of the ZrB2 film on quartz, glass ceramics, and stainless steel is 5–7 μm. The microhardness of the film on a stainless steel substrate under a load of 20 g is 17.8 GPa.  相似文献   

13.
TiO2/Eu-MCM纳米超分子材料的组装和光催化性能   总被引:1,自引:0,他引:1  
尹伟  张秀莲  张迈生 《化学学报》2005,63(13):1193-1200
利用有机相-水相界面共沉淀溶胶支持自组装方法制备粒径为15 nm、孔径为8 nm的分子筛Eu-MCM, 它拥有734 m2/g的比表面积和1.49 cm3/g的比孔容. 把TiO2组装到Eu-MCM的孔道中, 组装成TiO2/Eu-MCM纳米复合材料. XRD, RAMAN和选区电子衍射花样分析表明纳米复合材料中的TiO2为锐钛型. TiO2/Eu-MCM的发光表现为Eu3+离子的特征光谱, 激发峰分别为342 (5L10), 358 (5L9), 378 (5L7), 390 (5L6), 411 (5D3), 462 (5D2)和524 (5D1) nm; 发射峰为579, 592, 613, 653和701 nm, 归属于5D07FJ (J=0, 1, 2, 3, 4)组态间的跃迁. 纳米复合材料的发光强度都要比Eu-MCM的发光强, 其中43%TiO2/Eu-MCM的发光最强. 荧光和紫外漫反射结果表明客体TiO2对主体分子筛存在能量传递效应. 在微弱的紫外灯光照射下, TiO2/Eu-MCM纳米复合材料对苯酚的光催化氧化性能和其发光强度具有一定的相关性. 29%TiO2/Eu-MCM的纳米复合材料拥有的比表面积、孔容和孔径分别为204 m2/g, 0.24 cm3/g和4.7 nm. 29%TiO2/Eu- MCM对苯酚具有68%的最高光催化氧化产率和85%催化氧化选择性.  相似文献   

14.
Homogeneous cuprous oxide (Cu2O) nanoparticles with size of 8-10 nm are deposited on multiwall carbon nanotubes (MWNTs) by a polyol process using Cu(CH3COO)2·H2O as a precursor and diethylene glycol as both solvent and reducing agent. The composition of the resulting Cu2O/MWNTs composites is confirmed by XRD pattern, XPS spectrum and HRTEM images. With the change of the reaction conditions, it is found that Cu2O nanoparticles on the surface of MWNTs can be leafage-like or big spherical particle coated on the surface of MWNTs. HRTEM images indicate that all the leafage-like and big spherical particles are assembled by small Cu2O particles with size of about 2-5 nm. With the assistance of FTIR spectrum, a tentative mechanism is proposed for the formation of Cu2O nanoparticles with different morphologies on the surface of MWNTs.  相似文献   

15.
Scientists seek to synthesize new catalysts with simple methods to treat water pollution from organic dyes using photocatalytic degradation technology. In this technology, when light falls on the catalyst, the produced hydroxyl free radicals convert the dye into non-toxic gases such as CO2 and H2O. So, in this work, copper oxalate/cobalt oxalate/manganese oxalate (Abbreviated as P1) and copper oxide/cobalt manganese oxide/manganese oxide (Abbreviated as P2) new nanocomposites were fabricated via precipitation of Cu2+/Co2+/Mn2+ solution using oxalic acid and ignition of precipitate at 550 °C for 4 hrs, respectively. Some tools, involving X-ray diffraction (XRD), UV–vis spectrophotometer, energy dispersive X-ray spectroscopy (EDX), nitrogen gas sorption analyzer, transmission electron microscope (TEM), and field emission scanning electron microscope (FE-SEM), were used for characterizing the fabricated nanocomposites. The EDX spectra confirmed that the P1 composite consist of C (26.28 %), oxygen (46.66 %), manganese (7.27 %), cobalt (7.59 %), and copper (12.20 %). Also, the P2 composite consist of oxygen (8.23 %), manganese (31.34 %), cobalt (27.19 %), and copper (33.24 %). A transmission electron microscope shows that the P1 and P2 composites consist of polyhedral and spherical shapes with an average diameter of 28.13 and 14.37 nm, respectively. The BET surface area, average pore size, and total pore volume of the P1 composite are 29.0725 m2/g, 2.0749 nm, and 0.0302 cc/g, respectively. Besides, the BET surface area, average pore size, and total pore volume of the P2 composite are 58.1088 m2/g, 1.6087 nm, 0.0467 cc/g, respectively. 60 mg of the synthesized nanocomposites completely decompose 60 mL of 15 mg/L of malachite green dye solution within 20 min in the presence of hydrogen peroxide and UV light. The synthesized catalysts outperformed many other catalysts published in previous studies.  相似文献   

16.
The spherical mesoporous MCM-41 coated with a novel Ca2MoO5:Eu3+ phosphor layer was prepared for the first time. The obtained Ca2MoO5:Eu3+-MCM-41 was characterized via XRD and FT-IR. The crystal system of the Ca2MoO5 phase was determined to be orthorhombic, and its space group was found to be Ima2 (46), and its cell parameters were a = 16.175, b = 5.1514, c = 5.6977 A°; α = β = γ = 90°. The particle dimensions of MCM-41 and Ca2MoO5:Eu3+-MCM-41 nanoparticles were determined to be 260 nm and 229 nm via scanning electron microscopy analysis. Bortezomib was loaded into the Ca2MoO5:Eu3+-MCM-41 nanoparticles under scCO2 at 200 bars and 40 °C. The results of the TG analysis showed that the amount of drug-loaded to MCM-41 and Ca2MoO5:Eu3+-MCM-41 nanoparticles were determined to be 14.02% and 3.02%, respectively. The BET analysis showed that while the specific surface area and pore volume of MCM-41 and Ca2MoO5:Eu3+ before Bortezomib (BTZ) loading were 1,506 m2/g and 267 m2/g, respectively, after drug loading these values were found to decrease to 488 m2/g and 7.883 m2/g. It was determined that BTZ was released from the nanoparticles in a sustained manner over 66 h. The R2 value, which was calculated to be 0.9739, indicated that the release kinetic of BTZ followed the Korsmeyer–Peppas model.  相似文献   

17.
Mechanical properties of glass fiber reinforced composite materials are affected by fiber sizing. A complex film formation, based on a silane film and PVA/PVAc (polyvinyl alcohol/polyvinyl acetate) microspheres on a glass fiber surface is determined at 1) the nanoscale by using atomic force microscopy (AFM), and 2) the macroscale by using the zeta potential. Silane groups strongly bind through the Si? O? Si bond to the glass surface, which provides the attachment mechanism as a coupling agent. The silane groups form islands, a homogeneous film, as well as empty sites. The average roughness of the silanized surface is 6.5 nm, whereas it is only 0.6 nm for the non‐silanized surface. The silane film vertically penetrates in a honeycomb fashion from the glass surface through the deposited PVA/PVAc microspheres to form a hexagonal close pack structure. The silane film not only penetrates, but also deforms the PVA/PVAc microspheres from the spherical shape in a dispersion to a ellipsoidal shape on the surface with average dimensions of 300/600 nm. The surface area value Sa represents an area of PVA/PVAc microspheres that are not affected by the silane penetration. The areas are found to be 0.2, 0.08, and 0.03 μm2 if the ellipsoid sizes are 320/570, 300/610, and 270/620 nm for silane concentrations of 0, 3.8, and 7.2 μg mL?1, respectively. The silane film also moves PVA/PVAc microspheres in the process of complex film formation, from the low silane concentration areas to the complex film area providing enough silane groups to stabilize the structure. The values for the residual silane honeycomb structure heights (Ha) are 6.5, 7, and 12 nm for silane concentrations of 3.8, 7.2, and 14.3 μg mL?1, respectively. The pH‐dependent zeta‐potential results suggest a specific role of the silane groups with effects on the glass fiber surface and also on the PVA/PVAc microspheres. The non‐silanized glass fiber surface and the silane film have similar zeta potentials ranging from ?64 to ?12 mV at pH’s of 10.5 and 3, respectively. The zeta potentials for the PVA/PVAc microspheres on the glass fiber surface and within the silane film significantly decrease and range from ?25 to ?5 mV. The shapes of the pH‐dependent zeta potentials are different in the cases of silane groups over a pH range from 7 to 4. A triple‐layer model is used to fit the non‐silanized glass surface and the silane film. The value of the surface‐site density for ΓXglass and ΓXsilane, in which X denotes the Al? O? Si group, differs by a factor of 10?4, which suggests an effective coupling of the silane film. A soft‐layer model is used to fit the silane‐PVA/PVAc complex film, which is approximated as four layers. Such a simplification and compensation of the microsphere shape gives an approximation of the relevant widths of the layers as the follows: 1) the layer of the silane groups makes up 10 % of the total length (27 nm), 2) the layer of the first PVA shell contributes 30 % to the total length (81 nm), 3) the layer of the PVAc core contributes 30 % to the total length (81 nm), and finally 4) the layer of the second PVA shell provides 30 % of the total length (81 nm). The coverage simulation resulted in a value of 0.4, which corresponds with the assumption of low‐order coverage, and is supported by the AFM scans. Correlating the results of the AFM scans, and the zeta potentials sheds some light on the formation mechanism of the silane‐PVA/PVAc complex film.  相似文献   

18.
A solution approach based on Au(CN)2? chemistry is reported for the formation of nanoparticles. The covalent character of the Au(CN)2? precursor was exploited in the formation of sub‐10 nm nanospheres (≈2.4 nm) and highly monodisperse icosahedral Au nanoparticles (≈8 nm) at room temperature in a one‐pot aqueous synthesis. The respective spherical and icosahedral Au morphologies can be controlled by either the absence or presence of the polymer polyvinylpyrrolidone (PVP). Using Au(CN)2? as a metal ion source, our findings suggest that the addition of citrate ions is necessary to enhance the particle formation rate as well as to generate a more homogeneous colloidal dispersion. Because of the presence of oxygen and the operation of a CN? etching process associated with Au(CN)2? complex formation, an interesting reversible formation–dissolution process was observed, which allowed us to repeatedly prepare spherical and icosahedral Au nanoparticles. Time‐dependent TEM images and UV/Vis spectra were carefully acquired to study the reversibility of this formation–dissolution process. In view of the accompanying generation of toxic cyanide anions, we have developed a protocol to recycle cyanide in the presence of citrate ions through ferric ferrocyanide formation. After completion of particle formation, the residual solutions containing citrate ions and cyanide ions were processed to stain iron oxide nanoparticles endocytosized in cells. Additionally, the as‐prepared 8 nm Au icosahedra could be isolated and grown to larger 57 nm‐sized icosahedra using the seed‐mediated growth approach.  相似文献   

19.
The boehmite nanofibers were prepared by using NaAlO2 and Al2(SO4)3 as the starting materials without any surfactant. The phase transitions of the boehmite nanofibres against different temperature were studied and various phases were derived from well-crystallized boehmite nanofibers. All these phases had the same morphology even after high temperature calcination. In addition, the retention of specific surface area of the samples were very high because of the limited aggregation occurred in calcinations for each sample. For instance, the ??-Al2O3 obtained at 500?°C had the specific surface area (208.56?m2/g) with an average pore diameter of 6.0?nm. With the further increase of the calcination temperature, the nanofibers became shorter and coarsening, which resulted in the decrease of the specific surface area. It is worthwhile to notice that the BET surface areas (40.97?m2/g) and the pore volume (0.27?cm3/g) of the fibrous structures obtained after 1200?°C calcination are substantially higher than that of the non-fibrous alumina because of the morphology maintenance.  相似文献   

20.
Nanosized MgF2 was synthesized by precipitation in microemulsions of water in cyclohexane stabilized by polyethylene glycol tert-octylphenyl ether. The synthesized MgF2 powder was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), BET specific surface area, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray diffraction (XRD). The results showed that the synthesized powder was a MgF2 powder with a crystallite size in the range of 9-11 nm and a specific surface area of 190 m2/g.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号