Carbon Quantum Dot-Based Thin Films for Multifunctional and Sustainable Applications

Abstract

Carbon quantum dots (CQDs) have attracted significant attention as a versatile class of nanomaterials owing to their abundance, biocompatibility, and highly tunable functional properties. Their optical, electronic, and chemical characteristics are strongly governed by particle size, surface functional groups, and heteroatom doping, while their carbon-based composition makes them attractive candidates for low-toxicity and biocompatible systems. CQDs are typically integrated into solid matrices, particularly polymer-based thin films, not only to suppress nanoparticle aggregation and environmental degradation but also to realize functional applications. Such integration also enhances the stability, reliability, and reproducibility of CQD-based composites, enabling their use for applications ranging from bioimaging and wearable sensing to antimicrobial and antifouling coatings, environmental remediation, and flexible optoelectronic devices. However, precise control over CQD size, surface chemistry, and dispersion within solid matrices, as well as scalable and reproducible fabrication of CQD-based films compatible with industrial processing, remains challenging. Moreover, ensuring long-term structural, optical, and functional stability of CQD-based films under practical operating conditions is essential for their reliable and widespread deployment. This review provides a comprehensive overview of recent progress in CQD-based films, with emphasis on CQD synthesis and film fabrication strategies, key application areas, associated challenges, and future research directions.