Terahertz spectroscopic studies of quantum dots–conjugated gold nanoparticles

Abstract

Composite structures of metal nanoparticles and semiconductor nanomaterials present unique properties that have made them candidates for various applications. The properties of these hybrid structures to a large extent depend on the design and specific material used in to produce them. Here, we present work on the synthesis and characterization of CdSeS/ZnS quantum-dot-gold nanoparticles hybrids (denoted as QD-GNP) and studies on their interaction with terahertz radiation. The prepared QD-GNPs were characterized using UV-vis spectroscopy (UV-vis), Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), Fluorescence Spectrometry, and Photoluminescence Lifetime measurement. The wavelength of maximum absorption of the gold nanoparticles was 519 nm while that of the quantum dot was 609 nm. The peak absorption band of the hybrid solution was around 519 nm. Transmission electron microscopy imaging revealed the surface morphological features of the quantum dot and gold nanoparticle. Strong photoluminescence quenching was observed upon the conjugation of the quantum dots with gold nanoparticles. The observed difference in the lifetime of free quantum dot and the hybrid QD-GNP was an indication of the bonding between the quantum dot and gold nanoparticles. A biexponential decay was observed with a lifetime of 3.57 ns for bare quantum dots and 1.05 ns for QD-GNP as for the faster component and the slower component 15.09 ns and 8.30 ns QD AND QD-GNP, respectively. Unique features were observed on the terahertz spectra of the composite structures in comparison with that of the either the QD or the GNP.