Modulating the Charge Transfer Plasmon in Bridged Au Core-Satellite Homometallic Nanostructures.

The localized surface plasmon resonance (LSPR) is one of the important properties for noble metal nanoparticles. Tuning the LSPR on demand thus has attracted tremendous interest. Beyond the size and shape control, manipulating intraparticle coupling is an effective way to tailor their LSPR. The charge transfer plasmon (CTP) is the most important mode of conductive coupling between subunits linked by conductive bridges that are well studied for structures prepared on substrates by lithography method. However, the colloidal synthesis of CTP structure remains a great challenge. This work reports the colloidal synthesis of extraordinary bridged Au core-satellite structures by exploiting the buffer effect of polydopamine shell on Au core for Au atom diffusion, in which the Au bridge is well controlled in terms of width and length. Benefiting from the tunable Au bridges, the resonance energy of the CTP can be readily controlled. As a result, the LSPR absorptions of the core-satellite structures are continuously tuned within the NIR spectral range (from 900 to >1300 nm), demonstrating their great potentials for ultrafast nano-optics and biomedical applications.