Local Electric Field Enhancement in the Vicinity of Ag Nanoparticles and Their Agglomerates in Zinc-Phosphate and Silicate Glass

Based on calculations, the spatial distribution of the local electric field (LEF) for various structural configurations of silver nanoparticles (NPs) in silicate and zinc-phosphate glasses was studied. The features of this distribution determine the efficiency of energy transfer from plasmonic NPs to rare earth (RE) ions located in the particle vicinity. The mechanism of energy transfer through field enhancement via surface plasmon resonance of particles, which is dominant for NPs of sizes of ≥ 5 nm, is determined by several factors. To clarify their roles and significance, the dependencies of LEF upon the size, spatial distribution, and degree of agglomeration of silver NPs in glass were studied. Comparative analysis of the nature of the field enhancement in places of hypothetical location of RE ions was carried out on the basis of a visual representation of the spatial distribution of the LEF in the vicinity of agglomerates of plasmonic NPs. Based on simulations, the dependencies of LEF intensity enhancement, the spatial distribution of such places in relation to the nearest plasmonic particle, upon the concentration of NPs, their size, degree of agglomeration, and the presence of small (≤ 5 nm) particles in the sample along with the relatively large ones, were determined. The optimal configuration of silver particles in glass for obtaining the maximum average enhancement of LEF intensity per the site of possible location of RE ion is revealed to be an agglomerate of NPs with sizes slightly larger than 25 nm and average distances between particle centers about 30 nm.