Study On The Energy Dissipation Characteristics Of Bimetallic Nanoparticles With Core-shell Structure

With the rapid progress of industrial development,the increasing consumption of traditional energy has brought about numerous environmental problems,so that renewable energy has attracted more and more attention from all walks of life.Solar energy has become an ideal alternative energy because of its advantages such as flexible exploitation and unlimited reserves.The development of nanotechnology provides an effective way to achieve high-efficiency absorption and utilization of solar energy.Bimetallic nanoparticles can effectively integrate the physical and chemical properties of two metals and express the unique properties of each metal at the same time,thus further improving the performance of light scattering,photothermal conversion,plasmon resonance decay and photon excitation.It is of great significance to explore and understand the energy attenuation path and energy transfer law in core-shell bimetallic nanoparticles for the realization of optical performance regulation of new solar materials.In this paper,the finite difference time-domain method was used to calculate the spectral properties,magnetic field,electric field and absorption power distribution of core-shell pure metal nanoparticles and bimetallic nanoparticles.The interaction between nanoparticles and incident light was studied to reveal the energy dissipation law of bimetallic nanoparticles with core-shell structure.Firstly,geometric models of core-shell pure metal nanoparticles and bimetallic nanoparticles were established to simulate the interaction between incident light and nanoparticles in the visible light band.The optical properties of the two kinds of nanoparticles were analyzed,and the effects of core size and shell thickness on absorption,scattering and attenuation of nanoparticles were obtained.It is proved that both core particle size and shell thickness of bimetallic nanoparticles can effectively regulate the absorption efficiency of nanoparticles.When the core particle diameter of Ag@Pt nanoparticles increases from 10 nm to50 nm,the absorption rate decreases from 99% to 71%,but it is still close to Ag@Ag nanoparticles.However,the absorption rate of Ag@Pt nanoparticles decreased rapidly with the increase of shell thickness.The resonance wavelength and resonance band range can be effectively adjusted according to the different effects of the change of core particle size and shell thickness on the resonance.Secondly,the distribution of electrical and magnetic fields around the nanoparticles is calculated by using the discrete grid.Based on the different refractive indices of core material and shell material,the energy distribution of the core and shell of bimetallic nanoparticles was separated,and the absorption power distribution within the nanoparticles was obtained.The energy distribution during the attenuation process was quantitatively described,and the law of energy transmission within the bimetallic nanoparticles under light induction was revealed.It is found that different shielding effects between atoms affect the formant evolution of the absorption power curves of the core and shell.When the wavelength is at the second resonance peak,the surface of the nanoparticle has a more concentrated electric and magnetic field distribution,and the Ag plasmon decays faster at this time.The higher shell absorption rate causes the attenuation path of the energy excited by the local surface plasmon to transfer from the core metal to the shell metal,and the energy tends to transfer to the nearby material.Finally,the energy dissipation law of core-shell bimetallic nanoparticles was revealed by studying the influence of factors such as the change of absorption rate during the energy dissipation process,the interaction between cores and shells of different materials,as well as the material properties that cause the interaction between plasmon metals and non-plasmon metals on the energy transmission process.When the core particle size increases to 100 nm,the proportion of energy dissipation by the scattering of nanoparticles increases,and the phenomenon of absorption inversion occurs.The fast electron transition between the bands of the non-plasmon metal shell is the preferred way to dissipate the electric field energy on the surface of nanoparticles.The metal shell with a larger imaginary part of the dielectric constant is helpful to accelerate the attenuation of the surface energy of nanoparticles.