Hollow Gold Nanoprism as Highly Efficient Single Nanotransducer for Surface-Enhanced Raman Scattering Applications

In this Article, we report the optical properties of anisotropic hollow nanostructure, hollow gold nanoprism (HGN, an equilateral triangular gold nanoprism with a circular cavity) and its application as a highly active nonaggregated surface-enhanced Raman scattering (SERS) substrate. Small colloidal HGNs are prepared using sacrificial galvanic replacement method. Our study reveals that HGNs are highly stable nanostructure in solution and robust against salt or ligand induced aggregation. We find that the LSPR spectra of the HGNs can be tuned by controlling their aspect ratios. Excellent SERS were detected from the J-aggregates of pseudoisocyanine dye, adsorbed on the HGN surface. Interestingly, strong SERS is obtained without the need of any aggregation of the nanoparticles. Numerical simulations reveal that a single HGN can not only harvest large local electromagnetic fields but also offer large sensing volume due to efficient plasmon hybridization, due to the presence of the cavity. This large sensing volume is a great advantage, and it is the key factor behind the observation of SERS from nonaggregated HGNs. A careful optimization of the plasmon-hybridization mediated field enhancement, for example, by controlling the cavity positions through the use of lithographic techniques, can enhance the SERS signal even further. All of the observations and analyses made in this work clearly suggest that HGNs will be an excellent choice in SERS-based chemical and biological sensing applications. Moreover, the cavity of an HGN has the potential for being used as nanoreactor, in the future.