Micro-raman spectroscopy study of colloidal crystal films of polystyrene-gold composites

Monolayers and multilayers of polystyrene (PS)-gold composite films prepared by two different deposition methods have been investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and confocal Raman microspectroscopy. The intensity of the 1001 cm ^-1 ring breathing mode of PS is used to evaluate the degree of ordering of monolayers and multilayers within a colloidal crystal. The depth profiling capability of confocal Raman microscopy is used to probe the regions inside the fractures in multilayered films. The intensity profile of the 1001 cm^-1 peak revealed the presence of fractures of different shapes with some PS microspheres at the bottom of the fracture. A strong increase in the Raman intensity (by 10³ times) has been observed when probing the regions where Au nanoparticles are concentrated in aggregates of different shapes. This enhancement is attributed to the surface plasmons generated by the periodic structure of the gold nanoparticles.