Eco-friendly carbon dot-based nanocomposites in smart construction materials for green-house gases reduction

Advanced composites and hybrid nanomaterials for environmental applications such as CO₂ capture could be a promising approach to addressing the impacts of climate change. One of the most promising zero-dimensional nanomaterials is carbon dots (CDs), which are carbonaceous nanomaterials whose particle sizes range from 1 to 10 nm. This study investigates environmentally friendly and novel carbon dot nanocomposites (CD-NCs), including TiO₂, ZnO, and SiO₂ semiconductor nanoparticles (SNs), in Portland cement (OPC) to be converted to new smart construction materials for reducing CO₂ emissions. Water-soluble CDs were made via microwave hydrothermal synthesis, forming 6-10 nm spheres. Optical properties revealed photoluminescence emission at 490 nm. Different molar ratios of CDs are introduced into the SNs to produce x% CD-TiO₂, CD-ZnO, and CD-SiO₂ (x = 0.01, 0.05, and 1% molar ratio). XRD, XPS, and TEM techniques evidenced the integration of CDs without modification in the crystallite size of host materials. CDs and their cement composites improved compressive strength and bulk density while lowering porosity, leading to enhanced hydration and better mechanical performance. Adding CDs to the nanoparticle matrix improved S _BET and XPS surface features, increasing oxygen vacancies. The nanocomposite cement's CO₂-removal performance and reuse were tested under simulated sunlight. The cement-based CDs nanocomposites show activity and reusability for three repetitive cycles, demonstrating their significance for CO₂ capturing.