Biodegradable blends of graphene quantum dots and thermoplastic starch with solid-state photoluminescent and conductive properties

Polymer composites based on blends of graphene quantum dots (GQDs) with thermoplastic starch (TPS) were prepared by melt-extrusion combined with hot pressing. The GQDs/TPS films were characterized as potential novel, high-performance, and ecofriendly composites replacing traditional non-biodegradable plastic packaging materials. GQDs stock solutions of different concentrations were incorporated into TPS matrices in order to analyze the solid-state fluorescent properties and conductive properties of GQDs/TPS films. The fluorescent, conductive, morphological, mechanical, and optical properties of the GQDs/TPS films were characterized by ultraviolet-visible spectroscopy, surface resistance measurement, scanning electron microscopy, Fourier-transform infrared (FT-IR) spectroscopy, tensile testing, and X-ray diffraction (XRD). FT-IR studies indicated hydrogen bonding between the oxygen-containing groups on GQDs surfaces and the -OH groups in the TPS. The mechanical testing results showed the optimum GQDs loading of 10.9 wt% in the blend. XRD and TEM studies indicated uniform graphene dispersions in the TPS matrix for ≤10.9 wt% GQDs loading; further increases in loading caused agglomeration. The maximum photoluminescence intensity and conductivity of the materials were obtained at 10.9 wt% GQDs loading. These materials have potential applicability in flexible optoelectronic packaging materials.