In situ spectroscopic and microscopic study on dispersion of Ag nanoparticles in polymer thin films

The dispersion process of Ag nanoparticles into vapor-deposited nylon 11 th in films caused by heat treatment has been investigated. In situ optical tr ansmission and Fourier transform infrared (FT-IR) reflection absorption spe ctroscopy were used independently for characterizing the changes in the sur face plasmon resonance response of Ag nanoparticles and in the thermal beha vior of the nylon 11 matrix during heat treatment, respectively. The peak w avelength of the plasmon band was observed to shift to shorter wavelength i n the temperature range 40-80 degreesC. The infrared temperature study reve aled that the as-deposited nylon 11 matrix is thermodynamically metastable and semicrystalline, including hydrogen-bonded small crystallites. These re laxed upon heat treatment above 40 degreesC, at which the Ag nanoparticles penetrated from the surface into the bulk phase of the matrix; These result s demonstrate that there is a strong correlation between the optical spectr al features, dispersion state of the particles, and structural change of th e polymer matrix. Dispersion mechanism is discussed in terms of the surface free energy of Ag nanoparticles, which is reduced upon embedding in the po lymer matrix.