(635f) Morphological Control in the Synthesis of Silver Nanostructures: Role of Polyvinylpyrrolidone (PVP)

Solution-phase syntheses are extremely useful for assembling metallic nanostructures with desired morphologies. For example, the polyol process [1] and the N,N-DMF reduction method [2] provide experimentalists the ability to finely manipulate the shapes and sizes of Ag nanostructures. A wide variety of different nanostructure morphologies have been achieved, including nanowires, nanoplates, cubes, etc. The morphologies of these nanostructures depend on: (i) the concentration of the silver salt (AgNO₃); (ii) the relative concentrations of the polymer capping agent (PVP) and AgNO₃; and (iii) the degree of polymerization of PVP. PVP plays a key role in controlling nanostructure morphologies in these fabrication processes. Based on experimental observations, the interaction strength between PVP chains and Ag atoms in different crystallographic facets is expected to vary significantly. This difference in interaction strengths is believed to influence the crystallinity of the Ag seeds and, in turn, the shape and size of the resultant nanostructures. A thorough theoretical study of the interaction between PVP chains and Ag nanoparticles would elucidate the structure-directing role played by PVP both in the polyol and N,N-DMF reduction processes. Using first-principles calculations based on DFT, as implemented in the VASP code, we compute the interactions of a PVP molecule with various crystal faces of Ag. In this talk, we discuss the results of our calculations and their ramifications for the assembly of Ag nanostructures.

[1] B. Wiley et al., Chem. Eur. J. 11, 454 (2005).

[2] I. Pastoriza-Santos et al., Adv. Func. Mater 19, 679 (2009).