DNA-directed Programmable Self-assembly Of Gold Nanoparticles

DNA has flexible structure, specific recognition of double-strand, and reversibleinteractions between complementary strands, which makes a candidate to bulid nanodevicesand nanoobjects. At present, it is a novel method to self-assemble metal nanoparticles(especially gold (Au) nanoparticles) through DNA direction. Compared with solated Aunanoparticle, gold nanoassemblies (NAs) have novel optical, electronic, catalytic and sensingproperties due to the synergistic effect between particles.In this thesis, a novel DNA-directed self-assembly strategy has been designed, throughwhich well-defined and ordered Au NAs were successfully obtained through programmblyassembling Au nanoparticles with about4.4and15.0nm. The components, structures, sizes,and shapes of Au NAs were characterized by transmission electron microscopy (TEM),agarose gel electrophoresis (AGE) and UV-visible (UV-vis) absorption spectrum. Meanwhile,the optical property of the assemblies were studied by suface enhanced Raman spectroscopy(SERS). The major results of this thesis were as follow:1. A novel DNA-directed self-assembly method has been disigned. In the self-assemblystrategy, DNA strand modified with thiol group in the mediun (B-A) played an important rolein the assembly of Au nanoparticles. Its two DNA chains can hybridize with other twoterminal thio-modified DNA strands (A′, B′), thus coming true programmable self-assemblyof Au nanoparticles by virtue of the interactions between the three thiol-modified DNAstrands.2. The15nm Au nanoparticles were prepared by the reduction of chloroauric acid withtrisodium citrate, after which it was incubated with B-A, A′, and B′and purified to acquireDNA/Au conjugates by AGE. Finally, geometrically controlled Au NAs were gained throughusing the different DNA/Au conjugates, which were characterized by TEM, UV-vis and SERS.In addition, the Au NAs SERS properties were explained by theoretical calculation.3. The4.4-nm Au nanoclusters were prepared by the reduction of chloroauric acid withsodium borohydride, after which it was incubated with B-A, A′, and B′and purified toacquire DNA/Au conjugates by AGE. Finally, geometrically controlled Au NAs wereobtained through using different the DNA/Au conjugates, which were characterized by TEM,UV-vis and SERS.