Interfacial Assembly Design And Applications Of Iron Based Nano Materials

In the iron-based nanomaterials have been extensively studied in the fields of tumor thermal magnetic hyperthermia,biological drug loading,catalysis and electromagnetic shielding due to their good qualities including biocompatibility,chemical stability,corrosion resistance and high Curie temperature etc.Among them,nanoparticles and iron nanoparticles are important iron-based nanomaterials.Recently,their advantages such as high reactivity,small particles size,non-toxicity and low cost have been widely used in environmental remediation and electromagnetic shielding.However,the intrinsic magnetic properties and high surface energy of iron-based nanoparticles lead to agglomerate,thereby reducing the reactivity and structural stability.Therefore,the different types of Fe₃O₄ nanoparticles are used as the building bulk and the ligands/surfactants are used as structure-directing agents to construct specific morphology Fe₃O₄interface assembly structures through self-assembly strategies.Subsequently,the Fe₃O₄assembled structures is further prepared by in-situ thermal reduction to obtained the iron nanoparticles assembled structures.We will focus on studying the mechanism of interface assembly and the correlation between assembled nanostructure and related properties.This thesis will discuss the research work from the following aspects:In chapter 1,we briefly describe the definition of iron-based nanomaterials,focusing on the synthesis progress of Fe₃O₄nanoparticles and iron nanoparticles,the research progress of interface modification,the research progress of interface assembly design,and the application of interface assembly nanostructures in the energy,catalysis,electromagnetic shielding and other fields.Subsequently,in view of the current challenges in the interface assembly design of nanoparticles and iron nanoparticles,the design ideas and synthesis improvement strategies were proposed.In chapter 2,monodisperse Fe₃O₄nanoparticles prepared by solvotheemal synthesis are used as building bulk for single-particle interface assembly research.Based on a novel anisotropic island nucleation and growth approach with the ordered mesostructured,we designed the Fe₃O₄@PMO with Janus structure assembled by Fe₃O₄nanoparticle and PMO.Further,the dosage of BTEE and solvent volume ratio were adjusted to achieve regulation about the exposure degree of nanoparticle.And the mechanism of the evolution of the asymmetric Janus structure to the symmetric core-shell structure.Subsequently,the Fe@PMO was derived from the Fe₃O₄@PMO by in-situ thermal reduction treatment.It can still maintain the original assembled structure and morphology,suggesting the excellent structure stability of assembled structure.The Fe@PMO assembly structure was used for the evaluation of the removal performance of heavy metal ions in the water system.And,the Fe₃O₄@PMO with Janus structure exhibits rapid adsorption and reduction of heavy metal ions during the initial 10 min of the reaction,and the best removal rate reach 71%,the final removal rate is close to?98%.The Janus structure of Fe₃O₄nanoparticles based on interface assembly will provide potential applications for the rapid detection and recovery of heavy metal ions in sewage systems.In chapter 3,the spherical Fe₃O₄nanoparticles with uniform morphology,uniform size and monodisperse were prepared by organic phase method.It was used as building bulk for the study of the multi-particle interface assembly.Based on the self-assembly strategy and ligand carbonization technology,we designed and prepared carbon-coated long-range ordered three-dimensional superlattice SP Fe₃O₄@C,which were used for the evaluation of microwave absorbing performance.Subsequently,the graphitization degree of carbon layer on the nanoparticles can be controlled by adjusting the ligand carbonization temperature.Among them,the long-range ordered three-dimensional superlattice SP Fe₃O₄@C-500 with high graphitization degree exhibits excellent wave absorption performance,which the EAB value can reach 6.45 GHz?frequency range:6.52 GHz-12.9 GHz?at thickness 3 mm.It achieves full absorption of X band?8 GHz-12 GHz?,which the electromagnetic waves generated by electronic devices in life are often attributed to X band.The largest EAB value can reach 8.55 GHz at thickness 2.5mm.Moreover,the long-range ordered two-dimensional superlattices SL Fe₃O₄@C and disordered non-assembled Fe₃O₄@C were obtained by regulating the self-assembly conditions to evaluate the effect of the order and dimension of the assembled structure for the wave absorption performance.With the order and dimension of the assembled structure increase,the corresponding EAB significantly increases.Therefore,the SP Fe₃O₄@C prepared based on self-assembly strategy will provide a feasible structural design for realization of“thin,light,broad,strong”absorbing materials.In chapter 4,we will further highlight the structural advantage of the superlattice Fe₃O₄@C with interface assembly structure.It will be used as the precursor to prepare the Fe@C with interface assembly structure by in-suit thermal reduction technique.Subsequently,the assembly structure morphology and the iron content of the Fe@C can be controlled by adjusting the reduction temperature.With the temperature increases,the superlattice gradually evolves from a long-range ordered periodic arrangement to a disordered arrangement,while the iron content gradually increases.The pure phase Fe@C shows corchorifolius-like microspheres with rough surface?denoted as CL-Fe@C?,and the iron content is 74%.The CL-Fe@C is used as an electrode material for the performance evaluation of electrocatalytic denitrification,which conversion rate of NO₃^-is?100%and the selectivity of N₂ can reach 98%.Moreover,with the iron content in Fe@C increase,the corresponding conversion rate of NO₃^-and the selectivity of N₂ increase.In addition,the selectivity of N₂in Na Cl system is better than Na₂SO₄system.Further,the product content in the reaction system was analyzed and reasonably inferred the reaction mechanism:the rough surface was beneficial to the adsorption of NO₃^-,which be efficiently converted to NO₂^-.And,both the high iron content and Cl-existing system can effectively promote the conversion of NO₂^-to N₂,enhancing the catalytic activity of the Fe@C with assembly structure.In chapter 5,the uniform morphology,uniform size and monodispersed Fe₃O₄nanoparticles was used as building bulk prepared from Chapter 3.And,the carbon cloth was used as support for the interface assembly Fe₃O₄ with short-range ordered and single/small layer assembly structure.The carbon coated Fe₃O₄ with assembly structure can be obtained by ligand carbonization,denoted as CC Fe₃O₄@C.After in-situ thermal reduction,the CC Fe@C with assembly structure be derived from CC Fe₃O₄@C.The iron nanoparticles on the CC Fe@C surface did not appear to melt and sinter during the crystal phase transition process,which maintained the original interface assembly structure.Further,the CC Fe@C was used as a self-supporting electrode for electrocatalytic denitrification,which show excellent performance and high conversion rate of NO₃^-after 120 h of continuous catalytic cycle.Due to the flexibility,low toxicity,magnetic properties and arbitrarily tailorable properties,the CC Fe@C will be expected to be a potential electrode material used in portable environmental repair electronic equipment.At last,the whole thesis is summarized.