Simultaneous Photoinduced Silver Nanoparticles Formation and Cationic Polymerization of Divinyl Ethers (original) (raw)

For the past two decades, there has been considerable interest in metallic nanoparticles in applications for quantum dots and homogeneous superconductors, for magneto-optics, and optoelectronics, and for chemical and biosensors and other devices. 1À4 One of the interesting optical phenomena of metallic nanoparticles is that of localized surface plasmon resonance which is observed as strong absorptions in the UVÀvisÀNIR spectrum due to the collective oscillation of the conduction electrons in the electromagnetic field. 5,6 Since the electromagnetic field can only penetrate a certain depth (∼50 nm for Ag 7 ), the surface electrons are the most important except for small particles. The effect of the silver particle size, shape, and containing medium on the localized surface plasmon resonance is rather complex. Summarizing the literature up to the mid-1980s, Bohren and Huffman 5 report that the plasmon resonance is red-shifted (shifted to longer wavelengths) as the particle size increases, and this has been further documented by Kreibig and Genzel. 8 Thus, in a recent study of the aqueous formation of silver from silver nitrate (the silver cation acting as the oxidizer) and trisodium citrate (acting as a reducer) in acid, the observed decrease in the wavelength maximum (a blue shift) as the concentration of citrate increased was interpreted by Smitha et al. 9 as a decrease in the particle size. However, Manikandan et al. 10 reported a blue shift as the diameter of silver nanoparticles in a ceramic increased. Regarding shape, as the particles become more spherical, the absorption maximum wavelength is predicted to decrease (i.e., the absorption is blue-shifted) 11 and to lower the absorption than less spherical particles such as cubes or rods, for example. The refractive index of the particle coating or of the embedding medium also has an influence on the plasmon resonance and causes a red-shift as the index increases. 6, One of the most useful ways of utilizing the properties of metallic nanoparticles is in the form of polymer composites, and those containing silver or gold particles offer unusual spectroscopic properties, high conductivity, and antibacterial activity. Although nanocomposites were initially prepared from separately formed nanoparticles and a polymer, 13À16 in situ formation of both the polymer and metallic particle provides a greater range of potential polymeric materials and a greater control of the particle size and distribution. Carotenu et al. 17 synthesized silver nanocomposites in poly(vinylpyrrolidone) using ethylene glycol as the solvent and reducer and suggested that they could be used for advanced optical applications. De Santa Maria et al. 18 manufactured silver nanoparticles in aqueous dispersions of styre-neÀdivinyl particles for bactericidal applications by reduction of the silver salt with hydroxylamine. In order to create a composite that protects against biological warfare agents, Wu et al. prepared aqueous dispersions of inorganicÀorganic hybrids incorporating silver nanoparticles by hydrazine reduction of AgNO 3 .