Robust development of gold nanorod-quantum dot assemblies for dynamic dual-modal single nanoparticle imaging and tracking applications

The development of optical microscopy methods for the dynamic imaging and tracking of individual nanoparticles and their assemblies continues to significantly contribute to transforming colloidal particle characterization and the integration of functionalized nanoparticles into a wide range of advanced applications. The real-time imaging of freely diffusing nanoparticles in suspension typically involves a single optical modality (e.g., Rayleigh or fluorescence scattering) which limits the potential of this approach to characterize more complex nanoparticle systems that feature at least two properties which require very different detection sensitivities. However, correlated imaging methods tend to be performed for nanoparticles that are confined close to a surface. To address this, we have developed a robust approach for the preparation of functionalized gold nanorod core – quantum dot (AuNR-QD) conjugates alongside a dual-modal setup that enables correlated plasmonic-enhanced Rayleigh scattering and fluorescence imaging of these nanoassemblies in suspension. Two separate routes are reported for the preparation of the AuNR-QD conjugates, which are also polymer wrapped to enable a stable and flexible platform for further functionalization and application integration. The utilization of real-time dual-modal imaging for assessing QD conjugation at various particle concentration ratios is demonstrated and the results of both dynamic colloidal and static ex situ measurements compared.