Effect of Shell Materials on Liquid Cs-Core for Optical and Thermoplasmonic Characteristics: A Simulation Approach

This study investigates the theoretical knowledge about the absorption cross-section, heat release, and temperature change of liquid Cs-core and various shell materials by employing the Mie theory. The present work was carried out with varying Cs-core sizes, viz., 10 nm, 15 nm, 20 nm, 25 nm, and 30 nm with a fixed 5 nm shell thickness of Ag and Au, Al and its oxide (Al₂O₃), and Cu and its oxide (Cu₂O) in the presence of the surrounding environment (i.e., water). The localized surface plasmon resonance (LSPR) peak position emerges between 299 and 1132 nm wavelengths, and the observed spectra are tuned in the vicinity of the ultraviolet (UV) and infrared (IR) domains of the electromagnetic (EM) spectrum. The maximum absorption cross-section was revealed for the 30 nm Cs-core at resonance wavelengths of 639 nm (σ_abs ≈2.41E − 14 m²) with a Cu shell thickness. The maximum temperature and absorption power at the surface of the nanoparticles were observed at 9.21 °C and 2476 nW for Cs@Cu at 629 nm wavelength in the water environment. Moreover, absorption cross-section spectra and heat power increased with increasing core-sizes. The E-field enhancement was highest when Cs NPs were placed in the core rather than the shell material, and the E-field values increased with decreasing Cs-core sizes. These results show that the intensity and LSPR position of peaks, heat generation, and temperature elevation are strongly influenced by varying the Cs core sizes with various shell materials. The observed results can have potential applications in thermoplasmonic devices, sensing, cancer therapy, photocatalytic activity, and Surface-enhanced Raman spectroscopy (SERS).