Carbon Dot Synthesis and Purification: Trends, Challenges and Recommendations

• Published in: Angewandte Chemie 2024-11, Vol.136 (48), p.n/a
• Main Authors: Hu, Yalei, Seivert, Océane, Tang, Yue, Karahan, Hüseyin Enis, Bianco, Alberto
• Format: Article
• Language: English
• Subjects: Biocompatibility; Carbon; Carbon dots; Carbon materials; Catalysis; Chemical synthesis; Clean energy; Coexistence; Dialysis; Electrophoresis; graphene; Impurities; Microparticles; Mixtures; Nanomaterials; Nanotechnology; Optical properties; Photoluminescence; Photons; Physicochemical properties; Purification; Reviews; separation
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202412341

Carbon dots (CDs) have rapidly emerged as a new family of carbon‐based nanomaterials since their initial discovery two decades ago. Numerous appealing properties, such as precursor and synthesis process flexibility, tunable photoluminescence, and good biocompatibility, have enabled their widespread applications in sensing, catalysis, energy, and biomedical fields. As the field expands, notable efforts have recently focused on mechanistically elucidating the structural formation and optical behavior of CDs. However, the absence of “clean” CDs presents a major obstacle to achieving a solid understanding of these aspects. Often, the claimed CDs are, in fact, a mixture of small molecules, oligomers, nano‐sized aggregates, or even microparticles. Such coexistence of impurities markedly impacts the physicochemical properties of resulting CD‐based mixtures, hampering the resolution of key mechanistic questions. Here, we aim to address this fundamental shortcoming of the field, going beyond the customary focus of the existing reviews that predominantly cover synthesis, optical performance, and application prospects. We begin with an overview of CD synthesis and then thoroughly examine the purification methods, including filtration, dialysis, electrophoresis, and chromatography. The insights provided here will guide the researchers towards obtaining high‐quality CDs, employing proper combinations of available tools, and ultimately paving the way for more demanding applications. This Review analyzes the current trends and challenges in the synthesis and purification of carbon dots prepared through various methods and using a wide variety of precursors. Diverse purification techniques, including centrifugation, filtration, dialysis, column chromatography, and electrophoresis, are systematically and thoroughly described, along with pointing out the gaps in the synthesis, purification, and assessment of CD purity.