Fabrication of CdS nanoparticle chains along DNA double strands

Positively charged CdS nanoparticles having diameter of 3.0 +/- 0.2 nm were prepared by the chemical modification of their surfaces with thiocholine. Chains of size-quantized CdS nanoparticles were prepared by using the elect rostatic interaction between positively charged nanoparticle surfaces and t he phosphate groups of DNA molecules. The observation by transmission elect ron microscopy revealed that the CdS nanoparticles were arranged in a quasi one dimension with dense packing. The line width of a nanoparticle array w as equal to the diameter of CdS nanoparticles that was ca. 3.0 nm. The aver age distance between the centers of the adjacent nanoparticles was estimate d to be 3.5 nm, which was almost equal to the length of 10 base pairs in DN A double strands.