Self-Assemblies from RNA-Templated Colloidal CdS Nanostructures

RNA serves as an effective template for the synthesis of quantized CdS nanoparticles and mediates their growth to create novel assemblies. Unlike DNA-stabilized particles in aqueous medium, these particles display relatively strong emission at 2.34 eV, which is further enhanced by more than 2.5 fold and blue shifts to higher energy (2.39 eV) upon aging. Chelation of Cd²⁺ with RNA restricts the nucleation of CdS. A variation in the molar ratio of Cd/S from 2 to 6 produces different nanostructures with varied electronic properties. Unlike general colloidal systems, aging of these nanoparticles produced smaller crystalline nanocrystals as evidenced by their blue-shifted optical threshold and fluorescence maxima, and by atomic force microscopy and transmission electron microscopy analysis. Different nanostructures grow upon aging to yield self-assembly of different shapes, and the morphology and structure of these nanostructures could be manipulated by changing the molar ratio of Cd/S. The formation of organized structures could provide a basis for controlled fabrication of new nanostructures and nanodevices.