MULTIPLE COLOR GRAPHENE AND TRANSITION-METAL D1CHALCOGENIDES QUANTUM DOTS

摘要

Graphene quantum dots (GQDs) have garnered an increasing interest as a promising new class of fluorophores as bio-imaging fluorescent markers, light emitting materials, and elements for photovoltaics. A prominent advantage of GQDs is their potential of replacing traditional semiconductor QDs for bio-imaging applications, in order to overcome toxicity associated with heavy metal ions present in QDs. GQDs have been synthesized using a variety of methods such as chemical breakdown of graphene oxide (GO)/carbon fibers (CF) or nano lithography, although both methods involve tedious multistep processes. Here, we report a two-step workflow to prepare multiple color graphene quantum dots with controllable diameters with mean values between 14 to 34 nm. Their optical properties are controlled by stoichiometry of an amine-containing molecule present in the reaction suspension. For biological application robust water soluble GQDs are required. So, we transfer the GQDs dispersed in methanol to water. Furthermore, the GQD particles exhibit two-photon fluorescence, measured on a home-made optical setup under Ti:sapphire near-infrared (NIR) pulsed-laser excitation. We also report on synthetic routes to metal dichalcogenide quantum dots (MDCQDs). While to date, very few works have been reported on these MDCQDs such as M0S2, and WS2, in which low quantum yields are obtained, complicated preparation steps are used, and material degradation was observed, here we employ a straightforward sonication method to prepare water-soluble M0S2 or WS2 QDs and enhanced their photo luminescence by a factor of nine by passivating their surface with amine groups. We demonstrate peptide binding to these particles by showing fluorescence resonance energy transfer (FRET) efficiency of maxima 28% from MoS2 to fluorescein isothiocyanate (FITC).