Confined Assembly And Optical Properties Research Of Nanocrystal Superlattices

Although self-assembly of binary nanocrystal mixtures into long-range ordered crystalline films with tunable lattice structures are well known,it would be interesting to shape these binary nanocrystal supracrystals into faceted assemblies because it potentially provides the shape-dependent optical,electronic and catalytic properties.Herein,we report the self-assembly of binary nanocrystal supracrystals with faceted morphologies from Fe3O4 and Au binary mixtures.The crystal structure of the binary system can be controlled by changing the size ratio(?)of Au/Fe3O4.When ?=0.56 formed the AlB2 binary nanocrystal supracrystals,the lattice parameters a=b>c,favors one-dimensional(1D)self-assembly along<001>direction,resulting in the formation of supraspindles and suprarods with twenty facets.However,for the symmetric cubic lattice system,when y=0.42 and 0.59,the binary structures of NaCl type and NaZn13 type are formed respectively,and the morphologies are truncated cubes and octahedrons that preferentially expose facets(100)and(111).In contrast,when ?=0.4,another cubic lattice structure bcc-AB6 is formed,and its morphology is truncated rhombic dodecahedra with(110)and(100)facets.By adjusting the shape of the binary nanocrystalline superlattice composed of magnetic Fe3O4 nanocrystals and plasma Au nanocrystals,the particle spacing in the superlattice is changed,and the surface plasmon resonance coupling effect between particles is controlled.To have a better understanding of the optical properties of the binary supracrystals,computational modeling of the binary supracrystals was done with various crystalline structures.The finite element method(FEM)simulations of the binary nanocrystal supracrystals were performed using Comsol Multiphysics,on the basis of solving Maxwell's equations in frequency domain.The simulation results are highly consistent with the experimental data.This will provide theoretical basis and display samples for the design of other new collaborative materials.Moreover,using simulation methods,we can predict the chemical and physical properties of supercrystals,such as assembly behavior,photoelectromagnetic properties,etc.,by controlling the size and crystal structure of the particles.Through the in-depth combination of simulation and experimental data,we believe that metamaterials have great application potential in biomedicine and plasma catalysis.Finally,we developed a simple strategy to control the assembly process of arrayed nanocrystals and demonstrated that the evaporation rate,nanocrystalline concentration,and template pattern can,be precisely controlled for the final assembly,resulting in a highly controlled arrayed assembly crystals.Due to the high crystallinity and crystal order characteristics of one-dimensional array,high responsiveness and fast response performance of photoelectric detection can be achieved.This simple and effective method can be extended to the microstructural integration of other material systems.