Developing methods to effectively integrate rare earth doped upconverting nanoparticles (UCNPs) with gold nanostructures are currently being sought for nanoscale theranostics due to their ability to convert near infrared (NIR) photons into visible light and heat. Because the large NIR absorption cross-section of the gold nanoparticles can significantly hampers the photoluminescence of UCNPs, methods to optimize the ratio of gold nanostructures to UCNPs must be developed and studied. Herein, we demonstrate nucleic acid assembly methods to conjugate spherical gold nanoparticles (AuNPs) and gold nanostars (AuNSs) to silica-coated UCNPs and investigate their effect on upconversion photoluminescence. In these studies, the number and type of Au nanostructure were found to play significant roles in modulating the optical output from the UCNPs. The results showed that while UCNPs fluorescence enhancement was observed from the AuNP-UCNPs clusters, to a large extent fluorescence quenching was observed for the AuNS-UCNP assemblies. However, by tailoring the ratio of AuNS to UCNPs, we found that little photoluminscence quenching was observed. More importantly, at these AuNSs concentrations, we were still able to observe a large temperature increase induced by the AuNSs upon 980nm irradiation. The optical measurements were also confirmed by simulation studies which demonstrated that the orientation and distance of the UCNPs with respect to the core and arms of the gold nanostructures played significant roles in photoluminescence. Finally, more recently we have loaded photosensitizers into the silica shells on the UCNPs whose absorption spectra matched well with emission of UCNPs to generate measureable quantities of singlet oxygen for photodynamic therapy. The combined photodynamic and photothermal effects the AuNS-UCNP clusters can potentially enable their eventual use as highly effective photodynamic and photothermal therapy imaging agents for nanomedicine.

Plasmonic moduation of fluorescence in gold nanostar-NaYF<sub>4</sub>: Yb/Er for multimodal imaging, photothermal, and photodynamic therapy

251st National Meeting (2016)

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Plasmonic moduation of fluorescence in gold nanostar-NaYF4: Yb/Er for multimodal imaging, photothermal, and photodynamic therapy

Plasmonic moduation of fluorescence in gold nanostar-NaYF₄: Yb/Er for multimodal imaging, photothermal, and photodynamic therapy