Nanopyramid With High Purity And Their Local Plasmonic Properties

Gold nanocrystals(Au NRs)are known for their outstanding plasmonic and physicochemical performances and thus have been widely applied in various fields,including spectroscopy,sensing,diagnostics,biotechnology,and catalytic reactions.They are especially preferred in preparing chemical samples and biosensors,because their shapes are well controllable and their localized surface plasmon resonance(LSPR)peaks are tunable1.However,longitudinal plasmon resonance may be difficult to assemble and unevenly broadened because of the huge size and shape distribution of Au NRs.Moreover,the electric field localization of Au NRs is not strong enough which restricts its applications such as plasmon-enhanced spectroscopy.Au nanopyramid particle(Au NBP),a symmetric structure with two sharp tips,can provide Nanopyramid With High Purity And Their Local Plasmonic Propertiesstronger confinement in the electric field and less dissipation in LSPR mode.In addition,it is feasible to change the LSPR of Au NBPs from the visible light region(VLR)to the near-infrared region(NIR)by tuning the tip angle of Au NBPs,which makes Au NBP a promising nanomaterial that can be used in bioimaging probes,bioanalytical sensors,and spectroscopy.Strong light-matter interaction has been widely studied due to its application in quantum computation,biosensing,nanolasing,and active plasmonic devices.When the energy exchange between plasmon and emitters becomes larger than the dissipation,Rabi splitting occurs in the frequency domain because of the intensive coupling.Unfortunately,it is still a great challenge to achieve such intensive coupling in a single metal nanoparticle under the ambient temperature,which,though,has been greatly reported in complex assembled structures such as dimers and gap structures.It is difficult to synthesize a suitable single nanoparticle with the strong confined electric field and low dissipation in the experiment.Besides,the seeds are structurally unstable,which hinders their applications in manufacturing high-end products.Au NBPs is a good choice to realize strong coupling at room temperature with better chemical stability and higher local electric field enhancement at the tip comparing to other nanoparticles.The wide tunable range from VLR to NIR in the situation of strong coupling can provide important applications in the biological and medical fields.To our knowledge,there were few reports of the strong interaction between Au NBPs and quantum emitters in the near-infrared region.In this paper,we used a seed-mediated method to synthesize Au NBPs with homogeneous shape and size in the experiment,which has a purity of 95%.By utilizing the finite-difference time-domain(FDTD)method to tune the LSPR of Au NBPs,we realized the strong coupling between few quantum dots(QDs)and Au NBP with a mode volume of?1178nm~3 in the visible light region and near-infrared region.The simulation results show an obvious Rabi splitting of 70 meV in scattering spectra in a single Au NBP.Furthermore,we compared the optical response of Au NBPs with Au NRs in realizing strong coupling and find that Au NBPs outweighed Au NRs in reducing dissipation and locally enhancing the electric field.Our results prove that Au NBPs have wide applications in the fields of materials,biomedical science,and quantum information.