Optic and catalytic properties of gold nanoparticles tuned by homopolymers

Gold nanoparticles (GNs) are prepared through in situ reduction using NaBH4 in the presence of homopolymer PDMAEMA. The sizes of the GNs can be adjusted by alternating the molar ratio of gold to DMAEMA. Pure PDMAEMA aqueous solution shows a phase-transition at 50A degrees C at pH 10 and 25A degrees C at pH 14, while PDMAEMA-supported GNs aqueous solution shows a phase-transition at 47A degrees C at pH 10 because of the increasing hydrophobic property resulting from GNs. Due to the pH and temperature-responsible characteristics of PDMAEMA, the resulting PDMAEMA-supported GNs exhibit pH adjustable temperature-responsive characteristics in optic and catalytic aspects. Under an acidic condition (pH 2), the GNs show unchanged surface Plasmon absorbance with a peak of 518 nm in a temperature range from 20 to 65A degrees C. Under a basic condition (pH 10), the GNs first show the same absorbance with a peak at 518 nm in a temperature range from 20 to 40A degrees C, and then the absorbance red shifts from 518 to 545 nm as temperature increases from 40 to 65A degrees C. When the GNs are used as catalysts to catalyze the reduction of p-nitrophenol, the catalytic activity can be adjusted by changing the permeation of reactants in the PDMAEMA layer at low and high temperatures, respectively.