Preparation Of Functional Nanometric Metals And Their Compounds By A Reverse Microemulsions Method

Because of their special structure,nano-metals based materials show peculiar characteristics such as photo-electricity,catalytic activity and magnetism,which make them have extensive application as functional nano-materials in the 21st century.The successful preparation of metal nano-materials has significant meaning to the real application of nano-scale functional devices.It is the key issue to prepare the nanometric particles with controllable uniform size and morphology in order to improve the various properties of the nano-particles.The Reverse microemulsions are transparent,isotropic,thermodynamically stable with nanosized water droplets which are dispersed in a continuous oil phase and stabilized by surfactant molecules at the water/oil interface.Because of its advantages of narrow diameter distribution,simple experimental devices and easy operation,the reverse microemulsions method has been employed as a suitable method to synthesize metals and/or their compound on the nanoscale with greater uniformity and controllable size.Here,Fe-based and Ru-based nano-particles were prepared by the reverse microemulsions method with the use of sodium bis(2-ethylhexyl) sulfosuccinate(AOT) as the surfactant and isooctane as the oil phase.The morphology and structure of the resulting were characterized by using transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR) and X-ray diffraction(XRD) respectively.The magnetic property was characterized by Vibrating sample magnetometer(VSM).The cyclic voltammograms(CV) and oxygen reduction reaction(ORR) were used to research electrochemical curves of Ru-based nanoparticles in the acidic environment.The main conclusions of our work are summaized follows: 1.The purity of surfactant(AOT) and the aging time of emulsion-breaking solution had a large effect on the particles size and distribution.When purified AOT was used, the obtained nano-particles had small size and uniform distribution,while the appropriate aging time improved the distribution of Fe-based nano-particles.2.When the surfactant concentration(n₀) was less than 0.3 M,can be obtained the spherical nano-particles of uniform distribution with 10 nm in diameter.When n₀ was more than 0.3 M,some of the nano-particles changed from spherical to the needle-like, meanwhile the spherical particles size increased to 12 nm.When no was 0.5 M,there was only needle-like.That indicated it can control nano-particles size and morphology by adjusting no.3.The obtained Fe-based nano-particles were component of Fe and Fe₂O₃.the nano-particles surface was still coated by partial of AOT after the products were centrifuged and washed.And the magnetic property showed the Fe-based nano-particles almost had no residual magnetism and can be used as Paramagnetic materials.4.The effects of surfactant concentration(n₀) and the molar ratio of water and surfactant(ω₀) on the Ru-based nano-particles had been investigated.With increasing n₀ andω₀,the size of Ru-based nano-particles increased.For the Ru₁Se_0.15 nano-particles,size increased from 4 nm to 8 nm with the increase of n₀ andω₀.5.It had been obtained Carbon supported Ru₁Se_0.15 with controllable composition and better diepertion synthesized by a simple reverse microemulsions method at room temperature.6.CV and ORR had been used to study the electrochemical behavior of Ru,Ru₁Se_0.15 and Ru₁Se_0.15/C nano-particles in the acid environment.The results showed that Ru-based nano-particles with the modification of Se can prevent oxidation of Ru in the acid medium,and the Ru-based particles can be used as the catalyst for oxygen reduction reaction.