We use Au@SiO_2 nanoparticles(NPs) to systematically and comprehensively study the relationship between nanostructure and activity for surface-enhanced Raman scattering. Calculation simulation using the finite different time domain method verifies the experiment results and further reveals that the particle size and the distance between the NPs play vital roles in the surface-enhanced Raman scattering(SERS). Furthermore, in order to better simulate the real experiment, a Au@SiO_2 nanosphere dimer is placed on the silicon substrate and Au substrate, separately. The simulation results show that the large EM field coupling is due to the "hot spots" transferred from the NP–NP gaps to NP–surface of metal gaps,meanwhile, more "hot spots" occur. We also find that the signal intensity strongly depends on the position of the probe molecule. This work provides a better understanding of EM field enhancement.
A novel organic–inorganic nanoparticle–photopolymer composite system is developed, and its fundamental holographic recording characteristics are studied. In this hydrophilic TiO2-nanoparticle-dispersed acrylamide photopolymer composite system, the counter-diffusion of monomers and nanoparticles plays a fundamental and key role in hologram grating formation. The experimental results indicate that the volume shrinkage of the nanoparticle–photopolymer film during the holographic recording can be drastically reduced compared with the undoped photopolymer film. It is also found that the diffraction efficiency of the grating recorded in the nanoparticle–photopolymer film depends strongly on the concentration of the TiO2-nanoparticles, and there exists an optimal TiO2-nanoparticle-doping concentration to make the diffraction efficiency and the refractive index modulation reach their maxima. Additionally, the digital data page is stored and reconstructed in the nanoparticle–photopolymer film.
