1 Introduction
Noble metal nanoparticles (NPs), such as gold and silver, have been studied extensively in various scientific fields due to their peculiar properties. Researchers have used NPs to fabricate biosensors. The demand for biosensors for virus detection has increased, and research is focusing on ways to fabricate small, portable devices enabling rapid and accurate detection. İn this work, noble metal NPs of different shapes and sizes, including nanospheres, nanowires, nanocubes, and nanocylinders, were dispersed in surrounding media to simulate, using the discrete dipole approximation (DDA) method, their plasmonic properties. For this, a new model was proposed to calculate the response of the surface plasmon peaks of the NPs considered, and new analytical formulas were presented. The RISs of oxide-coated metal nanocubes were studied here, too. RISs were found to depend on the shape, size, core material, shell thickness, and shell composition of the NPs.
2 Methods
-DDA is a general technique for calculating the scattering and absorption of electromagnetic radiations by particles of arbitrary shapes and compositions.
-The polarizability of the NPs considered can be written as follows:
where V represents the volume of the NP. F defines the depolarization factor.
-The properties of the NPs considered are quantified, in this work, in terms of absorption (Cabs) and scattering (Csca) cross-sections:
-Sensitivity is
3 Results
-A shift in plasmon wavelength with the shell thickness for X-SiO2 (X= Au, Ag, and Al) was found.
-A shift in the peak wavelength with the refractive index of medium for coated metallic nanocubes was found.
-A variation in sensitivity with particle size was found.
4-Conclusion
A new model was proposed and developed to model and control the plasmon peak position and intensity according to the particle size, core material, shell thickness, and shell composition. The RIS factor increased with an increasing thickness of the oxide layer.
