Hollow and Solid Metallic Nanoparticles in Sensing and in Nanocatalysis

When the size of a material is reduced to the nanoscale, at or below the characteristic length scale that determines their properties, the material acquires completely new properties. On this length, its characteristics become sensitive to further changes in size, shape, or whether they are hollow or solid. In this perspective article, we first discuss the different experimental techniques used in the synthesis, assembly, and handling of colloidal solid or hollow nanoparticles with single and double shells. This is then followed by comparing the experimental and theoretical (DDA and FDTD) results for solid and hollow plasmonic nanoparticles as sensors using two different methods. The first method compares the plasmonic enhancement of the radiative properties of molecules or materials (e.g., in surface enhanced Raman scattering, SERS). The second one is based on the amount of the plasmon peak wavelength shift of the nanoparticle in media with different dielectric functions. In the last section of the perspective, we present a summary of the difference between the solid and hollow nanoparticles in nanocatalysis. We present the results of a number of experiments showing that the superior catalytic properties of hollow nanoparticles are due to catalysis occurring within the cavity of the hollow nanoparticles. Finally, using a femtosecond optical technique, we show that adding a second shell of a stiff metal (like Pt or Pd) to the plasmonic hollow nanoparticles increases their mechanical stability.