Green synthesis of carbon quantum dots from Rosa canina L. (K-CQDs), preparation of K-CQDs filled polycaprolacton films (PCL/K-CQDs), investigation of their mechanical and biodegradability properties

Great efforts and investigations into biodegradable polymers are on going to decrease theuse of non-biodegradable plastics and solve their waste problem. Inrecentyears, biodegradable materials have gained popularity due to their synthetic versatility and flexible features. PCL is a synthetic and hydrolytically degradable polyester group polymer known for its good flexibility, non-toxicity, ease of processing, and compatibility with other polymers. Due to the insufficient mechanical properties of PCL, its use is limited. To improve their mechanical properties, PCL-based composites or nanocomposites have been produced with fillers. Carbon nanostructures have been widely used as fillers due to their excellent physicochemical, mechanical, and electrical properties. Carbon quantum nanodots (CQDs) areone of the carbon nano structures with superior properties that have become the focus of many studies in recentyears. In this study, K-CQDs samples were synthesized through a hydrothermal method using rosehip fruit (Rose Canina L.) and used as filler to produce PCL film nanocomposites with improved mechanical and biodegradable properties. The PCL/K-CQDs film nanocomposites filled with different contents (0,3-, 0,5-, 1,2-, 2,0-, and 4,0 wt.%) of K-CQDs were produced vialiquid phase ultra sonic mixing. The characterization results of K-CQDs samples showed that their quantum yields were 23.8%, their surfaces were enriched with oxygen-containing groups, and they exhibited a graphite phase structure. The results of the structural analysis confirmed the interfacial interactions between the K-CQDs and the PCL matrix, as well as the amorphous structures of the PCL/K-CQDs films. PCL/K-CQDs-2.0 film had the highest tensile strength value (17.65 MPa) with a 27.7% increase, and PCL/K-CQDs-4.0 film had the highest yield strength (9.02 MPa; a 40.9% increase) and the highest microhardness (4.80 HV0.025; a 14.8% increase) compared to PCL. Biodegradability test results showed that PCL/K-CQDs films exhibited lower weight loss than PCL due to polymer-filler interfacial interaction and amorphous structure.