Reproducibility roadblocks and standardization in carbon dot synthesis: a critical review of current practices, challenges, and future directions.

Carbon dots (CDs) have emerged as promising nanomaterials due to their unique photoluminescent properties, biocompatibility, and wide-ranging applications in biomedicine, sensing, energy, and environmental monitoring. However, despite extensive research on their synthesis and applications, the field faces persistent challenges in reproducibility and standardization. Variability in synthetic approaches, such as differences in precursors, reaction conditions, and post-synthesis treatments, leads to inconsistent physicochemical and optical properties, which hinders both scientific progress and commercial translation. This review critically examines the current landscape of CDs synthesis methods and the influence of key variables on material quality. It also provides a comprehensive evaluation of characterization techniques for determining essential properties such as particle size, surface charge, quantum yield, and emission stability. Special emphasis is placed on the major barriers to reproducibility, including batch-to-batch inconsistency, ambiguous classification schemes, and non-uniform reporting practices. Unlike prior reviews that primarily focus on synthetic routes or end-use applications, this work uniquely addresses the systemic lack of standardization across laboratories, which is a key bottleneck to scaling and regulatory approval. By analyzing emerging efforts toward harmonized protocols and exploring the potential of machine learning for synthesis optimization, this review offers actionable recommendations such as the adoption of reference materials and universal reporting standards. These insights aim to guide the development of robust, reproducible, and application-ready CDs technologies.