Graphene quantum dots (GQDs) have wide prospective applications for optoelectronic fields owing to their unique characteristics, such as tunable bandgaps, high chemical and optical stability, as well as good biocompatibility. In this work, we offered a convenient proposal to obtain uniform blue-green emissive GQDs and modified efficient orange-emitting graphene quantum dots (D-GQDs) derived from fullerene (C60) under acid-free conditions. The as-prepared D-GQDs demonstrate remarkable conversion efficiency, for which the quantum yield is up to 52.4% with an emission peak of 617 nm. Also, GQDs and D-GQDs were blended with poly­(vinyl alcohol) (PVA) to prepare transparent photoluminescent films, which show excellent flexibility and preferable white emission property meeting the requirements of commercial white LEDs.

No abstract

No abstract

Highly conductive concrete/mortar has been long pursued to realize structural health monitoring in the development of smartcement-based facilities. However, it remains challenging to significantly increase the electrical conductivity of concrete/mortar without lowering the compressive strength and flowability. Here, nanocrystalline-graphenecoated aggregates (termed Gr@AGs) are synthesized to break this conductivity−strength tradeoff. Admixing Gr@AGs with cement enables the construction of a conductive network of graphene that simultaneously strengthens the interfacial transition zone between aggregates and paste. As a result, high conductivity and improved mechanical properties have been simultaneously realized in Gr@AGs-based smart mortars. The significant positive effects of Gr@AGs are further enhanced by combining them with a low percentage of carbon fiber. Typically, the 28-day compressive/flexural strength of the optimized mortar increases by 12.2%/19.4%, with the electrical resistivity reduced by over 3 orders of magnitude from ∼4.6 × 10 5 to 182 Ω cm. On this basis, we demonstrate high-sensitivity cement-based piezoresistive sensors with a fractional change in resistivity as high as ∼25%, which is more than 1 order of magnitude higher than those reported in comparable systems. This study provides a solution to the critical issues in developing smart cementitious composites by taking full advantage of graphene's properties.