The Research Of Coupling Between Plasmon Modes And Photothermal Properties Based On TiN Nanospheres

The unique Localized Surface Plasmon Resonance(LSPR)generated by noble metal nanoparticles and light interaction has attracted wide attention in the nanophotonics field.When two noble metal nanoparticles get close to each other,the localized plasmon modes generated by the LSPR can be coupled,which led to both a stronger plasmon-enhanced electromagnetic field and a resonant wavelength shift.The distinctive behavior of the coupling plasmon modes has proved following the distance-dependent characteristics,an exponential decay law occurs as the departure distance increase,which has been boiled down to the notable ‘plasmon ruler equation’.A similar photothermal plasmon ruler also was reported in the optic-thermal coupling of the plasma.It provides a different idea and guidance for a new appearing set of applications including heat control,photothermal therapy and solar energy utilization.Unfortunately,the absorption bandwidth of noble NPs,often limited to visible light,is inadequate to narrow bands because of the small Drude damping factor,which restricts the applications in the power absorption and other fields based on plasmonic NPs.The development of new materials and new structures is imminent.Recently,Titanium Nitride(TiN)has become a research hotspot in the field of nano-optical absorption due to its large rude damping factor.It is found that TiN nanoparticles have wide bandwidth and high absorption efficiency in both the visible and the near infrared(NI)regions.However,there have been few studies of the TiN dimers interparticle near-field coupling behavior as well as the coupling power absorption.It is not clear whether the interparticle near-field coupling of the TiN is still satisfy the exponential decay equation,whether the optic-thermal coupling follow the existing photothermal plasmon ruler and whether there is any specific behaviors in small scale,these are worth our further research.In this paper,we study theoretically the optical properties of homo-dimers composed of TiN nanospheres with wide band absorption by finite element method(FEM).Firstly,the absorption spectrum of the TiN-TiN dimer is calculated in different polarization direction,and it is found that the interaction between light and dimer is more sensitive in the parallel polarized light.Note that an interesting decline emerges in coupling absorption with the separation gap below 5 nm,which behaves an obviously opposite trend compared with that for gold nanospheres dimer at small distance.And through further comparative study of Au-Au dimer in the same conditions,we find out the physical cause of its specific reduction.Based on the study of TiN-TiN dimer,we further study the coupling absorption and photothermal coupling of the TiN-Au hybrid dimer which composed by a TiN and an Au nanospheres.Through changing the distance between the nanoparticles,the maximum temperature difference can be obtained.And the temperature variation can be precisely controlled by adjusting the size of monomer of the TiN-Au hybrid dimer.By studying the temperature change of each monomer of hybrid dimer,a "heat plasmon ruler equation" based on double exponential decay is proposed.This provides a new way for nanoparticles to realize the nanoscale thermal control and applications in the micro-nano sensing field.