The Study Of The Topological Chemical Synthesis And Purification Of Low Dimensional Nanostructures

Nanomaterial is a new-fashioned type of material which has a widespread application in the field of physics and chemistry.The properties of nanomaterials are strictly dependent on their morphology and size,that is to say,the nanoparticles with different shapes or sizes will give expression to different features or application prospects.Therefore,fabricating monodisperse nanomaterial is always the goal of scientific research workers.However,there is a huge challenge in the preparation of ultrathin alloy nanosheets or monodisperse nanoparticles.Therefore,this paper has carried out two studies which are the topological chemical synthesis of two-dimensional nanomaterials and the method of density gradient centrifugation.The experimental researches and conclusions of this paper are as follows:1?Two-dimension ultrathin nanomaterials have quantum dimension effect in in their side direction,so they will have distinctive physical and chemical properties differing from the zero-dimensional,one-dimensional and three-dimensional nanomaterials.The two-dimension ultrathin nanomaterials have nearly infinite dimensions in the plane direction,and high proportion of unsaturated atoms on the surface.Therefore,two-dimension nanomaterials have tremendous specific surface area,special electronic structure and great internal conductance characteristics,which can be defined as excellent electrocatalytic materials.In recent decades,most of the 2D metal nanomaterials is noble metal by liquid phase synthesis.Transition non-noble metal nanostructures have high catalytic activity due to their d electrons,while most of the non-noble metal nanostructures have been reported were granular structures.The controlled synthesis of non-noble metal nanostructures with more excellent catalytic activity is still facing with enormous challenges.So we transformed layered double hydroxides array into non-noble metal ultrathin nanosheets array under a mild reductive condition by establishing an in-situ topological reductive method.Firstly,we synthesized binary NiFe LDHs,CoFe LDHs,NiCo LDHs and ternary NiCoFe LDHs nanosheets array on the Ni foam by hydrothermal method.And then using the mild solvothermal reducing condition to reduce the LDHs precursor to manufacture NiFe,NiCo,CoFe and NiCoFe binary or ternary alloy nanosheets.The metal alloy nanosheets not only kept the hydrotalcite morphology but also inherited the arrangement of traditional metal ion in the layered double hydroxides.Therefore,we could get ultrathin alloy nanosheets with atomic dispersed nanostructure by the in-situ topological reductive method.The binary or ternary alloy nanosheets presented perfect single-crystal structure,exposed(111)lattice plane and had about 10-15 atomic layer thickness.From the EXAFS data analysis,we could ensure that there was not Fe-Fe bond in the CoFe alloy nanosheets,that was the iron atoms disperse in the cobalt in the forrm of a single atom.And then we chose the partial oxidation in the room temperature to regulate electronic structure on the metal alloys' surface,to improve the electrocatalysis activity.The alloy metal nanosheets exerted different performance for HER and OER at different oxydic degrees.When the metal alloy exposed in the air about 6 hours,the performance was best.So we could say that the metal/metallic oxide interface could promote the electrochemical activity to some extent.As far as we know,this is the first report to establish the ultrathin atomic dispersed transitional binary or ternary alloy metal nanosheets,and provides a new way to fabricate non-noble metal alloy nanosheets.2?For the monodisperse nanomaterials,sometimes,which cannot obtain by optimizing the synthesis method,but can get by sample post-processing method.Density gradient centrifugation as an efficient separation method is widely used in the purification of nanomaterials.And the successful separation and purification of nanomaterials include FeCo@C nanoparticles,gold nanoparticles,gold nanobar,graphene,carbon nanotubes,hydrotalcite,zeolite nanometer sheet and so on.However,the most of research works are about the application of density gradient centrifugation with doing a lot of exploring experiments to obtain the optimum separation parameters.And yet,very few studies have been designed to investigate the separation effect on different separation parameters.So we combine the influence factors of the various parameters with the theory of density gradient centrifugation to model the separation process.Then through the mathematical modeling,the final separation parameters can be given by optimization calculation.For this study,we synthesized polydisperse cadmium selenide nanoparticles with good fluorescence property in the 1-octadecene,and then we analyzed the final separation effect with different parameters(centrifugal force,centrifugal time,density range,gradient interface)in the density gradient separation process using the cadmium selenide nanoparticles as the tracing agents.On this basis,we built the equation of motion of nanoparticles through theoretical research in the process of density gradient centrifugation to describe the movement of nanoparticles.And we used MATLAB mathematical modeling to optimize the kinetic equation simulation of nanoparticles.Eventually,we could get the simulative parameters with the optimal separation effect.And the calculated best parameters were used to separate given nanoparticles.According to the practice,we found that the calculated parameters were similar with the required parameters of actually experimental separation.Thus,we had a correct separation model of the density gradient centrifugation and accurate mathematical analog calculation,which provided a lot of theoretical basis.The optimal parameters which the best separation effect needed could be quickly obtained by simulation calculation,which could reduce a large number of exploring experiments to find the separation conditions.