Synthesis and regular array formation of nano-particles assisted by protein

Abstract

One of the important points in synthesis of nano-particles (NPs) is regulation of the size of particles. Use of a protein cavity as a grow field of NP is one candidate procedure to make the size uniform. Here fabrication of nanometric aluminium and indium particles using protein, ferritin, are described. Aluminium NPs were observed as nano-crystals however indium NPs were amorphous. The indium NPs thus formed have uniform spherical shape with diameter of 6.6 ± 0.5 nm, while aluminium NPs were somewhat irregular in shape with about 6 nm diameter. At some special condition, proteins are going to crystallize and that would provide regularly arranged sites for NPs. This means crystallization of proteins provides regular array of NPs. Regular two-dimensional (2D) arrays of indium nanoparticles are successfully produced by crystallising ferritin with indium NP (In-ferritin) on a solid surface using the denatured protein film method or direct spreading. The lattice constant of NP arrays obtained by the denatured protein film method is 13.3 nm with hexagonal packing, and arrays of more than 4 μm² in area can be obtained by transfer onto silicon wafer. Square lattice with spacing of 9.3 nm is also obtained by direct spreading of salt free In-ferritin on solid surface. The square lattice is expect to be bilayer because spacing of 9.3 nm cannot be performed by monolayer.