Carbon quantum dots as multifunctional nanomaterials for sustainable optoelectronic biosensing and green photonics

Carbon quantum dots (CQDs) have emerged as highly promising multifunctional nanomaterials for next-generation optoelectronic applications, offering tunable fluorescence, high biocompatibility, and sustainable synthesis routes. In this review, we explore recent advances in CQD-based fluorescent biosensors, emphasizing their potential in real-time pollutant detection, bioimaging, and green energy solutions. We analyze the underlying photophysical mechanisms, including quantum confinement, surface functionalization, and heteroatom doping, that govern fluorescence modulation. Importantly, the review highlights eco-friendly synthesis techniques and the integration of CQDs in optoelectronic architectures such as photodetectors, photocatalytic systems, and hybrid sensors. By coupling photonic and electronic responses within a single material platform, CQDs offer a pathway toward energy-efficient, neuromorphic-inspired sensing and processing. We conclude by identifying future directions for enhancing the multifunctionality, spectral selectivity, and device-level integration of CQDs, positioning them as sustainable alternatives in two-dimensional (2D) optoelectronic systems. This review explores recent advances in carbon quantum dot-based fluorescent biosensors, emphasizing their potential in real-time pollutant detection, bioimaging, and green energy solutions.