Platinum-coated Core-Shell Gold Nanorods as Multifunctional Orientation Sensors in Differential Interference Contrast Microscopy.

We characterized the optical properties of single platinum-coated core-shell gold nanorods (Pt-AuNRs) under dark-field (DF) and differential interference contrast (DIC) microscopy. Furthermore, we examined their potential use as multifunctional orientation probes. Longitudinal surface plasmon resonance damping was observed for single Pt-AuNRs due to Pt metals coated on the AuNR surface under single-particle scattering spectroscopy. Despite the strong plasmon damping with a much-decreased scattering intensity, DIC microscopy allowed us to detect single Pt-AuNRs with much higher sensitivity. We found polarization-dependent DIC images and intensities of single Pt-AuNRs, which allowed us to determine their orientation angle under DIC microscopy. Therefore, we report that single Pt-AuNRs can be used to develop multifunctional orientation probes under DIC microscopy.