Step-addition Method for Enhancing the Yield of Gold Nanoparticles in Block Copolymer Solution

作者：Ray Debes; Aswal Vinod K^*

来源：Journal of Macromolecular Science Part B-Physics, 2010, 49(4): 810-820.

DOI：10.1080/00222341003603743

• block copolymers
• dynamic light scattering
• gold nanoparticles
• micelles
• self-assembly
• small-angle neutron scattering

Triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) has been used to synthesize gold nanoparticles from hydrogen tetrachloroaureate (III) hydrate (HAuCl4 center dot 3H2O) salt in aqueous solution at room temperature. Measurements were performed using the triblock copolymer Pluronic P85 (EO26PO39EO26) at a fixed concentration (1 wt%) mixed with varying HAuCl4 center dot 3H2O concentration in the range of 0.001 to 0.1 wt%. The surface plasmon resonance (SPR) band in UV-visible absorption spectra confirmed the formation of the gold nanoparticles. The maximum yield of the nanoparticles was found at 0.005 wt% of the salt solution. Small-angle neutron scattering (SANS) does not show any significant change in the scattering profile in these suspensions of the nanoparticles. A similar behavior was also observed in dynamic light scattering (DLS) experiments where autocorrelation function was found to be independent of the salt concentration. This can be understood since a high-block copolymer-to-gold ion ratio (r 22) is required in the reduction reaction to produce gold particles. As a result, a very small fraction of the block copolymers were associated with the gold nanoparticles, and hence lead to a very low yield. Both SANS and DLS basically see the micelles of most of these block copolymers, which are not associated with nanoparticles. Based on this explanation, a step-addition method was used to enhance the yield of gold nanoparticles by manifold, where the gold salt is added in small steps to maintain higher value of r (22), and therefore continuous formation of nanoparticles.

• 出版日期2010