Study On The Self-Assebly Of Gold Nanoparticles Into Nanostructures

The self-assembled nanostructures of nanoparticles (NPs) behave new unique physical and chemical properties compared to individual nanoparticles, and these nanostructrures have great potential applications in electronics, optics, chemical and biological sensing. Currently, scientists have developed a penty of approaches for the self-assembly of nanoparticles. Take colloidal gold nanoparticles (AuNPs) as a example, the most simple way to produce various assembled nanostructrues is to tune the interactions between NPs through partially or totally replacing the stabilizers with other surfactants and thiols. However, these chemical molecules would remain in the system and they become an intrinsic"pollution"for some applications. Therefore, it is nessary to develop facile, surfactant-free, thiol-free, and template-free"green"methods to synthesis or assembly of NPs into"clean"nanostructures.This thesis studied the self-assembly of colloidal gold nanoparticles into one-dimensional (1D) and three dimensional (3D) nanostructures using facial and green approaches. We obtained some new results in following aspects:(1) We have demonstrated that addition NaX compounds into colloidal gold solution induced 3D network gold nanowires. The morphologies of these nanostructures can be tuned by the type and concentration of NaX, and the treating time. By this method, we have obtained 3D network nanowire of gold nanoparticles with the diameter of 17nm, 30nm, 60nm.(2) We have developed a novel route to rapid synthesis of millimeter-scale spongelike gold nanostructure within 3min by simply addition of NaBH4 into concentrated HAuCl4 aqueous solution. This approach is also suitable for the preparation of other noble metal sponge nanostructures.(3) We have first reported that citrate ions adsorbed on the surface of AuNPs partially desorbed when treated NPs with NaBH4, and stable 1D chainlike and 3D network assembly of AuNPs were produced by tuning the concentration of NaBH4 and ionic strength of the solution.(4) We have developed a novel route to directly transform the immobilized AuNPs sub-monolayer on a solid substrate into 1D chainlike assembly. We found that colloidal AuNPs can be adsorbed on aldehyde modified glass substrate through electrostatic attraction. This electrostatic interaction was weakened when the AuNPs were treated with NaBH4 and finally induced assembly of the NPs. The length, morphology and production of 1D assemblies can be controlled by regulating the density of the AuNPs, the concentration and treating time of NaBH4.