Triangular Au-Ag framework nanostructures prepared by multi-stage replacement and their spectral properties
(1. School of Physical Science and Technology, Central South University, Changsha 410083, China;
2. Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China;
3. Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China)
2. Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China;
3. Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China)
Abstract: Triangular Au-Ag framework nanostructures (TFN) were synthesized via a multi-step galvanic replacement reaction (MGRR) of single-crystalline triangular silver nanoplates in a chlorauric acid (HAuCl4) solution at room temperature. The morphological, compositional, and crystal structural changes involved with reaction steps were analyzed by using transmission electron microscopy(TEM), energy-dispersive X-ray spectrometry (EDX), and X-ray diffraction. TEM combined with EDX and selected area electron diffraction confirmed the replacement of Ag with Au. The in-plane dipolar surface plasmon resonance (SPR) absorption band of the Ag nanoplates locating initially at around 700 nm gradually redshifted to 1 100 nm via a multi-stage replacement manner after 7 stages. The adding amount of HAuCl4 per stage influenced the average redshift value per stage, thus enabled a fine tuning of the in-plane dipolar band. A proposed formation mechanism of the original Ag nanoplates developing pores while growing Au nanoparticles covering this underlying structure at more reaction steps was confirmed by exploiting surface-enhanced Raman scattering (SERS).
Key words: triangular Au-Ag framework nanostructures; multi-stage galvanic replacement reaction; surface plasmon resonance; surface-enhanced Raman scattering