Modulation of localized surface plasmon resonances of a silver nanoparticle array upon the presence of MoS2 coatings or underlying thin films
Résumé
There has been recently a growing interest in studying light-matter coupling using supported metallic nanostructures arranged into periodic arrays. The influence on the layer thickness of two-dimensional materials such as molybdenum disulfide MoS2 on the plasmonic behaviour of these arrays has become of great relevance due to the favorable bonding between S (sulfide atom) and metal atoms such as gold and silver as well as the variation of optical transition of MoS2 depending on the atomic thickness of the film. In this work, we have numerically studied the change in absorption spectra of an ordered array of silver nanoparticles AgNPs when attached to glass as well as to glass coated with different layers of MoS2. This arrangement was compared to an AgNPs attached to glass and post coated with MoS2 films of increasing thickness. It was shown that an overcoating of four MoS2 layers results in an increased plasmonic sensitivity compared to uncoated glass/AgNPs interface. Replacing the glass substrate by glass coated with MoS2 of different thickness and with added AgNPs shows a significant to the red shift with increasing MoS2 layers. This band is due to strong excitation-plasmon coupling of the silver lattice with MoS2 layers. Important is the fact that the electrical field is strongly enhanced beneath the MoS2/AgNPs barrier. One also observes a significant enhancement of the sensitivity. Hence, the design of more sensitive AgNPs/MoS2 based-plasmonic biosensors could be reached. Indeed, we show that AgNPs coating with few layers of MoS2 leads to approximately a 210.26% higher sensitivity.