Hollow and Solid Metallic Nanoparticles in Sensing and in Nanocatalysis

Abstract

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 properties 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.

Hollow metal nanostructures for enhanced plasmonics: synthesis, local plasmonic properties and applications

“…As mentioned earlier, Ag nanostructures are known to have better plasmonic performance than those of Au [9,14], as the plasmonic properties of Au nanostructures suffer a lot from the interband transitions as their onset partially overlaps with the LSPRs, causing a decrease in the intensity [10][11][12]. Mahmoud et al [14] applied DDA simulations to calculate the plasmonic field intensity generated by individual Ag nanocubes and Au nanoframes or their dimers (as shown in Figure 8), revealing that Au nanoframes can generate plasmonic fields that are comparable to those of Ag nanocubes.…”

“…In addition to the above-presented experimental results, several simulation studies by using DDA and FDTD have been conducted in order to understand the distribution of the plasmon resonances in individual or coupled hollow metal nanostructures [14,127,128,[166][167][168][169][170][171]. These simulation studies were usually used to explain the enhanced performance of the hollow nanostructures in applications like sensing and catalysis by revealing the distribution of plasmon resonances inside and around the nanostructures and calculating the generated electromagnetic fields [14,127,128].…”

“…These simulation studies were usually used to explain the enhanced performance of the hollow nanostructures in applications like sensing and catalysis by revealing the distribution of plasmon resonances inside and around the nanostructures and calculating the generated electromagnetic fields [14,127,128]. For instance, Mahmoud and El-Sayed [127] experimentally studied the sensitivity of Au nanoframes with different lengths and wall thicknesses and concluded that the sensitivity factors increase as the aspect ratio, the ratio between the length and wall thickness, increases.…”

“…Hollow AuAg nanostructures come into prominence as a potential solution for such combination of features as cavities are known to have better plasmonic properties than their solid counterparts thanks to a mechanism called plasmon hybridization [13]. Mahmoud et al [14] revealed by discrete dipole approximation (DDA) simulations that Au nanoframes can generate plasmonic fields whose intensities are comparable to those of Ag nanocubes. Thanks to the enhanced plasmonic fields, hollow metal nanostructures have been used in many applications such as sensing, SERS, photo thermal ablation (PTA) of cancer, drug delivery, and catalysis over the years with performances better than their solid counter parts, which is reviewed in detail in Section 4.…”

Interaction of Colloidal Silver Nanoparticles with Ni2+: Sensing Application

“…Metal nanoparticles are widely used in several different fields, from biotechnology and biomedicine, to optics and optoelectronics, and recently also as nanosensors for air and water pollution [1][2][3][4][5][6][7][8][9][10][11]. These innovative materials have peculiar physical (mechanical, magnetic, optical, etc.)…”