Tuning the absorptions of Au nanospheres on a microshell by photo-deformation

We report the design, modelling, fabrication, and testing of a photo-tunable particulate medium that comprises photo-responsible polymeric microshells covered by Au nanospheres. The microshells were formed by a layer-by-layer method. The charged Au nanospheres were coated on outer surfaces of the microshells. The polymeric shells contain azobenzene moieties and shrink upon ultraviolet irradiation; therefore, the interparticle spaces between the nanospheres are tunable by UV light. The absorption spectrum of the Au nanosphere modified microshells changed drastically after the shrinkage. A decreased absorption peak of Au nanospheres and an enhanced absorption in the near-infrared region were clearly observed. The results of theoretical modelling suggest that the overall spectral changes stem mainly from the enhanced particle interactions and also from the field enhancements in the space among the nanospheres.