Effective medium theory to the description of plasmonic resonances: Role of Au and Ti nanoparticles embedded in MoO3 thin films

Gesuri Morales-Luna,Michael Morales-Luna

doi:10.1038/s41598-020-62706-4

Gesuri Morales-Luna, Michael Morales-Luna

Open Access

https://doi.org/10.1038/s41598-020-62706-4

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Abstract

The growing interest in functional transition metal oxides for efficient energy consumption or in the bio-sensing process; indicates that is necessary to develop a new theoretical method that describes experiments. This article presents a new theoretical methodology to characterize molybdenum trioxide (MoO3) thin films doped with resonant gold – nanoparticles (Au – NPs) and non-resonant titanium – nanoparticles (Ti – NPs). The modulation of surface plasmon resonance (SPR) and the implications in the MoO3 transmittance spectrum is described by applying an effective medium theory. The transmittance modulation was modified by variating three parameters, the radius of the NPs, the concentration of the NPs as well as the variation of the MoO3 thin films thickness. It was found that the nanoparticles concentration is the most important parameter in the transmittance modulation. Additionally, the orthorhombic and monoclinic structure of MoO3 was studied, from which it was obtained that the monoclinic structure of the MoO3 doped with Au – NPs favors the reduction in the transmittance values in the visible region which is associated with the increase of the SPR signal. Similar analyses are performed for non-resonant nanoparticles such as Ti, where it was found that optical modulation is not as marked as the case of gold nanoparticles.

Highlights

The growing interest in functional transition metal oxides for efficient energy consumption or in the bio-sensing process; indicates that is necessary to develop a new theoretical method that describes experiments
The most studied formalisms that consider effective medium theories (EMTs) are Maxwell Garnett or Bruggeman, these models are applied to described materials with granular topology[11] and materials with intermixed components[12], respectively. These EMTs are based on small spheres approximation, which means that the size of the particles is small compared with the incident radiation wavelength[13]
Combining the effective medium approach with well stablished reflection or transmission coefficients[18] to predict the behavior of undoped and doped thin films, could be a novelty method to study thin films. Employing this model to describe the behavior of various materials the transition metal oxides (TMOs) such as molybdenum trioxide (MoO3), tungsten trioxide (WO3) and titanium dioxide (TiO2), to name a few of them, will be useful to predict the material optical behavior[19,20,21]

Summary

Introduction

The growing interest in functional transition metal oxides for efficient energy consumption or in the bio-sensing process; indicates that is necessary to develop a new theoretical method that describes experiments. Will be studied the effect of the transmittance spectra (evolution of the SPR phenomenon) of MoO3 thin films doped with Au – NPs. It should be noted that these nanoparticles are considers as a noble metal, known as plasmonic particles[36].

Results

Conclusion