Study On The Effect Of Damping On Surface Plasmonics And Related Applications

In the past decade,plasmonics has always been the hot spot and frontier of international research.The localized surface plasmon resonance(LSPR)effect has become the foundation and core content of this field due to its ability to generate strong electromagnetic fields,light scattering,and a large number of hot electrons.The shape,size,structure,and composition of particles have a significant impact on LSPR,and there have been numerous reports on related research.In addition,under the influence of external field,there are many kinds of damping of plasmonics,which will also affect the strength and behaviors of LSPR,and then affect the application of plasmonics.However,there are few reports on the impact of damping on surface plasmons and related applications.This makes it difficult to explain the damping related phenomena that often occur in related applications,and the energy conversion efficiency of plasmonic applications cannot be fully improved.Aiming at these issues,this paper establishes an analytical model and conducts researches on the behavior of electrons and energy conversion efficiency of LSPR,in order to understand the impact of damping on different applications of plasmonics.The innovative results obtained are as follows:(1)A surface enhanced Raman scattering(SERS)intensity mechanism based on chemical interface damping(CID)has been proposed.It demonstrates that the adsorption of target molecules on the surface of SERS substrate will increase the Raman scattering centers,thereby increasing the SERS intensity.However,CID is also introduced,significantly weakening the LSPR effect and SERS enhancement factor;It was revealed that the SERS intensity should be the result of the co-impact of the two,and may not necessarily monotonically increase with rising concentration;It is proposed that there often exists a maximum value for SERS strength,which depends on the strength of CID.The above conclusion has been experimentally confirmed.This work is a refinement and supplement to the existing SERS enhancement mechanism,and provides a reference for SERS and other surface plasmon related applications.(2)The mechanism of CID-based near-field spectral redshift was proposed and experimentally confirmed,revealing the physical cause of the redshift of the SERS’s optimal excitation wavelength relative to the LSPR;A criterion of the shift in the optimal excitation wavelength of SERS has been proposed for the noble metalmolecule system,that is,in the SERS substrate-molecule system that generates physical adsorption,the optimal excitation wavelength of SERS is consistent with LSPR,while in the system that generates chemical adsorption,the optimal excitation wavelength of SERS will significantly redshift LSPR.In addition,the stronger the CID,the more significant the red shift of the optimal excitation wavelength of SERS.This not only reveals the role of chemical interface damping in SERS testing and deepens the understanding of the electromagnetic enhancement mechanism in SERS,but also provides practical guidelines for selecting the optimal excitation wavelength in SERS testing.(3)A localized field loss mechanism based on crystal defect damping is proposed,revealing that the anomalous phenomenon of low SERS activity in star shaped Au nanoparticles is caused by high concentration of crystal defects within the particles.In previous work,gold nanostars often exhibited excellent SERS performance due to their rich hot spots and nano gaps.However,our study found that the SERS performance of Au nanostars rich in crystal defects is exceptionally poor.Combined with finite element method simulation,it was confirmed that the low SERS activity of the prepared gold nanostars is due to the damping introduced by defects,which reduces the strength of LSPR.This work highlights the significant impact of crystal defects on SERS activity,deepens the understanding of the electromagnetic enhancement mechanism of nanostructures,and has guiding significance for the design and preparation of highly active SERS substrates.(4)A crystal defect-enhanced photothermal conversion strategy was proposed,which significantly improves the photothermal conversion performance of plasmonic nanoparticle by introducing sufficient concentration of crystal defects;The analytical model of defect damping harmonic oscillator is established,which reveals the relationship between the photothermal conversion performance and the crystal structure of plasmonic particles,and shows that defect damping can effectively improve the photothermal conversion performance;From an experimental perspective,the introduction of crystal defects improved the photothermal conversion efficiency of gold particles by 23%.This work effectively explores the intrinsic properties of plasmonic particles,break through the limitations of existing ways to improve photothermal conversion,and provide new ideas for the design and preparation of photothermal agents with high photothermal performance.