Ultrasensitive second harmonic generation nanoprobes via plasmonic coreshell structures

Here we show, for the first time to our knowledge, that when we encapsulate a core material that is not centrosymmetric (BaTiO₃) in a plasmonic shell (Au), the SHG response is strongly enhanced at resonance. In theory, the enhancement can reach 900 times based on a 100 nm diameter BaTiO₃ core and a 10 nm Au shell. Such composite nanostructures potentially provide a class of ultrasensitive SHG biomarkers. We adapted previous self-assembly schemes for core-shell assembly to the synthesis of BaTiO₃-core Au nanoshell. The nanoparticles were first dispersed on an Indium-Tin-Oxide (ITO) coated glass slide for SEM, after which polarization-dependent SHG measurements were performed using a femtosecond Ti: Sapphire oscillator operated at 800 nm.