Preparation of Polymer-stabilized Palladium–silver Bimetallic Nanoparticles by γ-irradiation and their Catalytic Properties for Hydrogenation of cis,cis-1,3-Cyclooctadiene

Polyvinypyrrolidone (PVP)-stabilized Pd-Ag bimetallic colloids were successfully prepared in an acetone:2-propanol solution mixture of palladium acetate and silver perchlorate, and in an aqueous solution of palladium nitrate and silver nitrate by γ-irradiation. The prepared PVP-stabilized bimetallic nanoparticles were characterized by UV, TEM, XRD, and XPS. In Pd–Ag bimetallic nanoparticles, the XPS data indicated that the constituent elements were in the metallic state, and the palladium atoms were concentrated on the surface of the alloy cluster. These PVP-stabilized bimetallic nanoparticles were used as catalysts for hydrogenation of cis,cis-1,3-cyclooctadiene (COD).     

Evaluation of the Performance of Carbon Supported Pt–Ru–Ni–P as Anode Catalyst for Methanol Electrooxidation

This research is aimed to improve the activity and stability of ternary alloy Pt–Ru–Ni/C catalyst. A novel anodic catalyst for direct methanol fuel cell (DMFC), carbon supported Pt–Ru–Ni–P nanoparticles, has been prepared by chemical reduction method by using NaH₂PO₂ as a reducing agent. One glassy carbon disc working electrode is used to test the catalytic performances of the homemade catalysts by cyclic voltammetric (CV), chronoamperometric (CA) and amperometric i–t measurements in a solution of 0.5 mol L^–1 H₂SO₄ and 0.5 mol L^–1 CH₃OH. The compositions, particle sizes and morphology of home‐made catalysts are evaluated by means of energy dispersive analysis of X‐ray (EDAX), X‐ray diffraction (XRD) and transmission electron micrographs (TEM), respectively. TEM images show that Pt–Ru–Ni–P nanoparticles have an even size distribution with an average diameter of less than 2 nm. The results of CV, CA and i–t curves indicate that the Pt–Ru–Ni–P/C catalyst shows significantly higher activity and stability for methanol electrooxidation due to the presence of non‐metal phosphorus in comparison to Pt–Ru–Ni/C one. All experimental results indicate that the addition of non‐metallic phosphorus into the Pt–Ru–Ni/C catalyst has definite value of research and practical application for enhancing the performance of DMFC.     

Effect of transition metals (Ni,Sn and Mo) in Pt5Ru4M alloy ternary electrocatalyst on methanol electro-oxidation

Pure Pt, PtRu and Pt₅Ru₄M (M = Ni, Sn and Mo) electrocatalysts were prepared using a NaBH₄ reduction method. The alloy formation and particle size of the electrocatalysts were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The formation of crystalline Pt was confirmed regardless of the addition of Ru and transition metals. The average particle size was found to be about 2.5–3.5 nm.The electrochemical properties of the electrocatalysts were analyzed by methanol electro-oxidation and CO stripping in the half cell. The mass activity and specific activity were obtained through these experiments. Methanol electro-oxidation and the specific activity of the PtRuNi electrocatalyst were much higher than that of PtRu electrocatalyst. The specific activity of methanol electro-oxidation based on EAS for the PtRuSn and PtRuMo electrocatalysts was higher than that of the PtRu, although their mass activity of methanol electro-oxidation was lower.     

Radiation synthesis and characterization of poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone) based hydrogels containing silver nanoparticles

A series of PVA/PVP based hydrogels at different compositions were prepared by gamma irradiation. The gel fraction degree of swelling were investigated. Highly stable and uniformly distributed silver nanoparticles have been obtained onto hydrogel networks. The morphology and structure of (PVA/PVP) hydrogel and dispersion of the silver nanoparticles in the polymeric matrix were examined by scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR), respectively. The formation of silver nanoparticles has been confirmed by ultraviolet visible (UV–vis) spectroscopy. A strong characteristic absorption peak was found to be around 420 nm for the silver nanoparticles in the hydrogel nanocomposite. The X-ray diffraction pattern confirmed the formation of silver nanoparticles with average particle size of 12 nm. The diameter distribution of silver nanoparticles was determined by dynamic light scattering DLS. Transmission electron microscope (TEM) showed almost spherical and uniform distribution of silver nanoparticles through the hydrogel network and the mean size of silver nanoparticles ranging is 23 nm. The good swelling properties and antibacterial of PVA/PVP-Ag hydrogel suggest that it can be a good candidate as wound dressing.     

Metal nanoparticles stabilized by cubic silsesquioxanes for catalytic hydrogenations

Octa(diacetic aminophenyl) silsesquioxanes (OAAPS) were synthesized and used as stabilizers for preparing metal (Pt, Pd and Ru) nanoparticles using NaBH₄ as a reducing agent. The synthesized catalysts were characterized by UV-vis, XRD, and TEM. The average diameters of Pt (0), Pd (0) and Ru (0) nanoparticles are 1.6 ± 0.3, 1.4 ± 0.2 and 1.3 ± 0.2 nm, respectively. The metal colloids show excellent stability since OAAPS offer stronger bonding of the cubic linker to the metal nanoparticles through the chelating effect. All colloids prepared are stable and show no precipitation at room temperature for several months. The catalytic hydrogenations of phenyl aldehydes using the metal colloids as catalysts demonstrate that catalytic activities depend on the variety of the metal colloids and the substrates. The colloidal catalysts stabilized by OAAPS can be recycled by simply adjusting the pH of the solution.     

Pt/Co和Pt/Ni双金属纳米溶胶制备及催化制氢

采用化学共还原法制备聚乙烯吡咯烷酮(PVP)稳定的Pt/Co和Pt/Ni双金属纳米溶胶,采用UV-Vis、TEM等对所合成的Pt/Co和Pt/Ni双金属纳米溶胶进行表征,研究了化学组成对双金属纳米溶胶催化剂催化NaBH4水解制氢的影响. 结果表明,所制双金属纳米溶胶的平均粒径约为2.0 nm,双金属纳米溶胶的催化能力高于单金属Pt, Co, Ni纳米溶胶,Pt/Co和Pt/Ni双金属纳米颗粒优异的催化性能可归因于电荷转移效应,Co或者Ni原子与Pt原子之间发生的电荷转移效应使得Pt原子带负电而Co或者Ni原子带正电,荷电的Pt和Co、Ni原子成为催化反应的活性中心,促进了催化反应的进行.     

离子液体[BMIm]NTf2中Ni纳米颗粒的制备及其催化性能研究

微波辐射下合成了1-丁基-3-甲基咪唑双三氟甲基磺酰亚胺（[BMIm]NTf2）离子液体,并采用IR和1HNMR验证了其结构。利用化学还原法分别在水溶液和离子液体[BMIm]NTf2中制备了Ni纳米颗粒,采用XRD、TEM对其结构进行表征,并考察这两种纳米Ni颗粒在邻硝基苯催化加氢反应中的催化性能。结果表明,[BMIm]NTf2中制备的Ni纳米颗粒为面心立方结构,粒径在3—30nm。在还原过程中,离子液体同时起到了溶剂和修饰剂的作用,在所生成的M纳米颗粒的表面形成了一层离子液体的修饰层,阻止了Ni纳米粒子之间的团聚;在相同条件下,[BMIm]NTf2中制备的纳米Ni颗粒的催化活性显著高于常规水性介质中制备的Ni催化剂。     

Raney Ni catalysts derived from different alloy precursors (I) morphology and characterization

Ni-Al alloys containing 41.3, 49.2 and 59.9 wt% Ni were leached by reaction with 20 wt% aqueous NaOH solution under different temperature and time. The reactivities of alloys and morphologies of resultant catalysts were investigated. A large difference in reactivities of alloys toward alkali solution was revealed according to the composition of the alloy. As Al content in precursor alloy increased, the reactivity of alloy toward alkali solution increased. It was shown that, during leaching, reaction in Ni 41.3 wt% alloy is restricted to reaction interface, whereas that in Ni 49.9 wt% alloy occurs throughout the product layer. Surface area and pore size distribution were seen to be strongly dependent upon leaching conditions and relatively independent of the composition of precursor alloy. This paper was prepared at the 2004 Korea/Japan/Taiwan Chemical Engineering Conference held at Busan, Korea between November 3 and 4, 2004.     

Preparation of Ultrafine Fe–Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis

We prepared ultrafine Fe–Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe–Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5–3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe–Pt nanoparticles and UV–visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe–Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed.     

Microwave-Assisted Polyol Process for Synthesis of Ni Nanoparticles

Ni nanoparticles of controlled size in the range 30–100 nm were synthesized with polyvinyl pyrrolidone (PVP) and dodecylamine (DDA) as protecting agents through a microwave-assisted technique using ethylene glycol both as a reducing agent and a solvent. The morphology of Ni nanoparticles was controlled by the amount of DDA added in these systems. Particle size and size distribution were controlled by the concentration of metal source and the DDA to PVP ratio. The synthesized Ni nanoparticles were characterized by transmission electron microscopy for particle size and morphology, and size distribution was calculated by Image J^TM software. Experimental UV-Vis spectra of Ni nanoparticles matched with the calculated spectrum based on Mie's theory. The microwave-assisted polyol process was found to be faster than the conventional-polyol process in Ni nanoparticle synthesis and the former technique is expected to be cost-effective compared with the latter.     

The effects of hydrothermal and thermal treatment on structure of Ni (or Co)-mesoporous molecular sieves

Ni (or Co)-mesoporous molecular sieve was hydrothermally synthesized from sodium silicate, nickel chloride or cobalt chloride. Cetyltrimethyl ammonium bromide (CTAB) was used as a template. The samples were characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (TPR), Fourier transform infrared spectrosocopy (FT-IR) and N₂ physical adsorption. The results show that the long-range ordered Ni (or Co)-mesoporous molecular sieve was synthesized. The as prepared Ni-mesoporous molecular sieve has a specific surface area of 753 m²/g and an average pore size of 3.23 nm, and the pore structure of the as prepared Ni-mesoporous molecular sieve still existed after calcination at 750°C for 3 h or hydrothermal treatment at 100°C for 5 days. On the other hand, the as prepared Co-mesoporous molecular sieve has a specific surface area of 744 m²/g and an average pore size of 4.44 nm. The as prepared Co-mesoporous molecular sieve was transformed into wormhole-like mesoporous structure after calcination at 650°C or hydrothermal treatment at 100°C for 5 days and the mesoporous ordering became very poor after calcination at 750°C for 3 h.     

纳米银粒子的制备及其催化性能的研究

采用化学还原的方法,以聚乙烯吡咯烷酮为稳定剂,硼氢化钠为还原剂合成了纳米级银粒子。TEM和XRD分析表明所制备的银纳米粒子粒径分布窄,其平均粒径为15nm左右,且具有较高的结晶度。进一步催化硼氢化钠还原甲苯胺蓝的实验表明该银溶胶具有较高的催化活性。     

Novel micelle-forming block copolymer composed of poly (ε-caprolactone) and poly(vinyl pyrrolidone)

The well-defined poly (ε-caprolactone) (PCL)/poly(vinyl pyrrolidone) (PVP) diblock copolymers were synthesized through combining radical polymerization of VP and the controlled coordination-insertion ring-opening polymerization of CL using an aluminum alkoxide macroinitiator formed from the equimolar reaction of triethylaluminum with hydroxy-terminated PVP (PVP-OH). The molecular characterization of PCL/PVP diblock copolymers was confirmed through ¹H NMR spectroscopy and GPC analysis. Polymeric micelles composed of PCL as a hydrophobic core and PVP as a hydrophilic shell were prepared by a diafiltration method. The micellar properties such as sizes, shapes, and critical micelle concentrations (CMC) were investigated with a dynamic light scattering (DLS) spectrometer, transmission electron microscope (TEM) and spectrofluorimeter. The sizes of micelles ranged from 30 to 80 nm in average size. The novel micelles formed from the well-defined PCL/PVP diblock copolymers seem to be feasible as novel promising carriers in biomedical and pharmaceutical applications.     

聚乙二醇/聚乙烯吡咯烷酮修饰的纳米Fe3O4粒子的制备与表征

为了获得能够在水中稳定分散,具有广泛应用前景的磁性纳米粒子,以不同分子量的聚乙烯吡咯烷酮(PVP)作为修饰剂,在聚乙二醇(PEG)中高温热分解乙酰丙酮铁(Fe(acac)₃)制备了纳米Fe₃O₄粒子。采用X射线粉末衍射仪(XRD)、透射电镜(TEM)、高分辨透射电镜(HRTEM)、超导量子干涉仪(SQUID)、热重分析仪(TGA)、傅里叶变换红外光谱仪(FT-IR)、纳米粒度与zeta电位分析仪对样品进行了表征,并对样品在生理盐水和生理缓冲液中的稳定性进行了研究,结果表明:制备的纳米Fe₃O₄粒子具有高的结晶度以及单分散性,在300 K下,具有超顺磁性和较高的饱和磁化强度;PEG和PVP共同修饰于纳米Fe₃O₄粒子表面,为纳米Fe₃O₄粒子提供了良好的水分散性;制备的纳米Fe₃O₄粒子在生理盐水和多种生理缓冲液中能够高度溶解并稳定地分散。水中的纳米Fe₃O₄粒子表面呈电中性,表面修饰层的空间位阻效应是所制备的纳米粒子在水溶液中高分散的原因。     

聚乙烯吡咯烷酮/银纳米复合纤维膜的制备及抗菌性

通过液相原位还原法(用乙醇还原硝酸银)获得了合有银纳米粒子的溶胶,从而制得聚乙烯吡咯烷酮(PVP)/银纳米粒子/乙醇纺丝液;再利用静电纺丝技术,得到了含有银纳米粒子的PVP纳米复合纤维膜.利用紫外光谱仪(UV-vis)对溶胶内银纳米粒子进行了表征,运用扫描电子显微镜(SEM)和透射电子显微镜(TEM)对纤维及其内部的纳米粒子的形貌结构和分布进行了表征,并且测试了该样品对大肠埃希菌的抗菌性能.结果表明:利用静电纺丝方法可制取PVP/银纳米粒子复合纤维膜,该膜具有抗菌性.     

Preparation of Pt–Ru–Co trimetallic nanoparticles and their electrocatalytic properties

Ternary Pt–Ru–Co nanoparticles are prepared by microemulsions procession. These resulting materials showed a homogenous alloy structure, the mono-dispersion and an average diameter of 2.7 ± 0.6 nm with a narrow particle size distribution. The composition of Pt–Ru–Co nanoparticles can be controlled by adjusting the initial metal salt solution and preparation conditions. Pt–Ru–Co ternary metallic nanoparticles can enhance catalytic activity towards methanol oxidation compared to Pt–Ru bimetallic nanoparticles.     

Ni–Pt/H-Y Zeolite Catalysts for Hydroisomerization of n-Hexane and n-Heptane

Ni–Pt/H-Y zeolite catalysts with different Ni contents were prepared and applied to the hydroisomerization of n-hexane and n-heptane in the temperature range 225-375 °C. ESCA studies show the complete reduction of Ni species up to 0.3 wt% Ni addition over 0.1 wt% Pt/H-Y and further addition leads to the occurrence of unreduced nickel species as NiAl₂O₄. A TEM study shows the formation of bimetallic (Ni–Pt) particles of nanoscale size and the average particle size is found to increase with increasing Ni loading. Acidity measurements by NH₃-TPD and pyridine-adsorbed FTIR spectroscopy show the increasing occupation of acid sites by the added nickel when increasing the nickel loading. The catalytic activity of Ni–Pt/H-Y zeolite and Pt/H-Y catalysts was compared and it was found that addition of Ni up to 0.3 wt% increases the n-hexane and n-heptane conversion, multibranched isomer selectivity and sustainability of the catalysts due to better metal-acid synergism, complete reduction of Ni species and the formation of catalytically active Ni–Pt bimetallic particles. Further Ni addition leads to a decrease in conversion and multibranched isomer selectivity and an increase in the cracked products, which may be due to the presence of unreduced Ni species and pore blockage by larger-sized bimetallic particles formed.     

CMC稳定的Ni/Fe双金属催化体系的制备及对PCB77原位脱氯降解

以羧甲基纤维素钠(CMC)作为稳定剂,优化了制备条件,在反应温度25℃,m(CMC)/m(Fe)=5以及m(Ni)/m(Fe) =0.03的条件下成功制备了CMC-Ni/Fe纳米双金属颗粒.用制得的CMC-Ni/Fe纳米双金属颗粒于30℃下降解5 mg/L的PCB77溶液48 h,当双金属颗粒用量为3 g/L时,有高达94％的PCB77被降解,而没有加入CMC的Ni/Fe双金属体系只有71％的PCB77被降解.CMC-Ni/Fe纳米双金属颗粒经XRD检测,表现出明显的单质铁特征峰,且无铁氧化物特征峰,表明制备所得的纳米颗粒中的铁单质没有被氧化.经粒度分析仪的检测,CMC-Ni-Fe双金属纳米颗粒平均粒径在23.94 nm,明显小于没有加CMC的Ni/Fe双金属颗粒粒径(100 nm).     

溶胶-凝胶自蔓延法合成BaFe_x(Ti_(0.5)Mn_(0.5))_(12-x)O_(19)(X=8,9,10,11,12)铁氧体粉末

采用溶胶-凝胶自蔓延法合成了BaFex(Ti0.5Mn0.5)12-xO19(X=8,9,10,11,12)铁氧体粉末,利用XRD,TEM,VSM等测试手段对其物相组成、显微结构及磁性能等进行研究,研究结果表明,合成样品均为纳米级铁氧体粉末,平均粒径为50-80 nm。焙烧温度、Fe/Ba比率对磁性能均有不同程度的影响。     

A facile approach to preparing palladium nanoparticles-embedded polyvinylpyrrolidone (PVP) heterogeneous hybrid nanofibers mats by electrospinning

Well-dispersed palladium nanoparticles (Pd NPs) were prepared under the condition that trisodium citrate was the reduction agent and polyvinylpyrrolidone (PVP) was the stabilizing agent via sol-gel process. By making good use of the advanced electrospinning technology we obtained Pd NPs/PVP composite nanofibers films. Optical properties were examined by UV-visible absorbance spectra (UV-vis) and Fourier transform infrared spectroscopy (FTIR). The morphology and distribution of Pd NPs in/on PVP matrix were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that Pd NPs presented as spherical spots and distributed in/on PVP nanofibers uniformly; their diameter was 4–10 nm and decreased with the increase of PVP. The as-prepared Pd NPs/PVP hybrid mats possess catalytic activity, stability and reusability, as verified by performance in Heck reaction.