Monolayer of octadecylamine（ODA） and salmon sperm DNA or salmon sperm DNA-Cd complex were studied on air-water interface by π-A isotherm. After being co-transferred onto substrates by Langmuir-Blodgett technique, atomic force microscope（AFM） measurements show the DNA molecules are packed into lines in the film, due to the interactions between the ODA and DNA molecules. By exposing the ODA and DNA-Cd complex LB film to H2S, needle-like CdS nanoparticles were formed along the DNA lines as characterized by transmission electron microscope（TEM）. Electron diffraction（ED） image indicates that the so prepared needle-like CdS is a new kind of nanostructured materials.
Interactions between Cd 2+ ions and salmon sperm DNA were investigated via UV Vis, Circular Dichroism(CD) and FT Raman spectroscopies. The experimental results show that Cd 2+ ions can coordinate with the phosphate groups of DNA and thus induce conformation changes of the DNA from B to A type.
DNA/octadecylamine(ODA) monolayers were transferred onto silicon substrates and the morphologies of the monolayers were investigated by Atomic Force Microscope(AFM). AFM images show that the morphologies of DNA dissolved in pure water are very different from those of DNA dissolved in the NaCl solution. When DNA molecules are dissovled in pure water, they will form ball-like structure in the monolayer. When the DNA molecules are dissolved in NaCl solution, they will form bunch lines. This DNA line offers a valuable template to direct the formation of unique inorganic nanomaterials.
CdS nanoclusters were directly synthesized in aqueous solution by using mercaptoacetic acid as the stabilizer. The results of TEM(Transmission Electron Microscopy) and ED(Electron Diffraction) show that the structures and aggregations of the resulting CdS nanoclusters can be affected by the molar ratio of mercaptoacetic acid and Cd 2+ ion. When the ratio was high, the resulting nanoclusters were observed as densely packed layer structure on the template. When the ratio was low, the prepared CdS nanoclusters can not form highly aggregated structure. Fluorescence spectra of the CdS nanoclusters show a strong yellow fluorescence.
CdS nanoparticles were synthesized by using two complementary 2′ phosphorothioate oligo DNA, oligoG 10 SH and oligoC 10 SH as stabalizers. Because the thiol group was modified at phosphate site between C1 and C2 of 5′ end, the spatial exposure of DNA residue at C1 site was preponderant compating with the spatial exposure of the nanoparticles when the DNA renatured. The experimental result showed DNA renaturation ratio is about 50% and CdS nanoparticles were assembled into parallel quadrilateral array as the DNA renaturation progressed.
