Plasmon Exciton Interaction in Gold Nanostructure and Quantum Dot Conjugate and its Applications in Biosensing

ZHANG TAO

Publication

Plasmon Exciton Interaction in Gold Nanostructure and Quantum Dot Conjugate and its Applications in Biosensing

ZHANG TAO

Abstract

By synthesizing gold nanostructure (AuNP) and quantum dot (QD) conjugates, we investigated the optical properties of this type of conjugates both experimentally and theoretically. Also, the potential applications of the conjugates in protein detection and surface-enhanced Raman scattering (SERS) were also explored. The gold nanostructure synthesized includes spheres (SAuNPs, with diameters of 11 nm, 25 nm, and 45 nm), rods (AuNRs, aspect ratio 2.5-3), and popcorn-shaped particles (PS-AuNPs). The plasmon-exciton interactions in gold nanostructure (AuNP) and quantum dot (QD) conjugates were studied systematically by single particle dark field scattering and Finite Difference Time-Domain (FDTD) calculations. In this research, the effect of plasmon-exciton interaction mainly led to two optical phenomena: photoluminescence enhancement and emission wavelength shift. Plus, the strong interaction between PS-AuNP and QD is very sensitive to the local dielectric environment. Based on this, PS-AuNP-QD conjugate is an ideal material for molecular detection and sensing. A protein detection model was demonstrated based on biotin-avidin coupling. Last but not least, the high electric field enhancement due to the strong interaction between PS-AuNP and QD makes the conjugate a good candidate for Surface Enhanced Raman Scattering (SERS). Using 514 nm Argon laser as excitation, we found that the SERS enhancement factor for certain Raman dye can be as high as 108. We also observed the binding site molecular vibration information of biotin and avidin using the same technique, which suggests that PS-AuNP-QD can be applied as a platform for protein confirmation dynamics detection.