We systematically summarize the recent progress in the green synthesis and formation mechanism of CDs with the hope to provide guidance for developing CDs with the concept of green chemistry. In addition, we discuss and organize the current opinions on the fluorescence origin of CDs and the latest progress of CDs in fluorescence sensing applications.

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The room temperature synthesis of highly PL CNDs and GQDs by simply mixing TETA and p-benzoquinone and the origin of their photoluminescence.

Core–shell structural carbon quantum dots (CQDs) are prepared through a highly efficient self-exothermic reaction at room temperature, which possess 24.6% absolute quantum yield and can be well applied for analysis applications.

Highly selective and sensitive detection of guanosine 3'-diphosphate-5'-diphosphate (ppGpp), namely, the stringent in plants or microorganisms responding to strict or extreme environmental conditions such as stress and starvation, which plays an important role in gene expression, rRNA and antibiotics production, regulations of virulence of bacteria, and growth of plants, faces a great challenge owing to its extreme similarity to normal nucleotides. By modifying the surface groups of a facile two-step hydrothermal route prepared carbon dots (CDs) with terbium ions (Tb) in this contribution, a novel fluorescent probe with excellent properties such as highly physical and chemical stability, narrow emission and excitation wavelength-independent emission was prepared. The Tb ions on the surface of CDs cannot only preserve the intrinsic fluorescence (FL) of CDs but also keep its own coordination capacity with rare earth complex, and thus the clamp structure (four phosphate groups) of ppGpp can specific binding with Tb ions on the surface of CDs to produce antenna effect. Therefore, a highly selective and sensitive fluorescent ratiometry of ppGpp was developed by terbium-modified carbon dots (CDs-Tb) with the limit of detection as low as 50 nM based on the synergistic effect of antenna effect of Tb ions and specific recognition capacity of CDs. The applicability of this assay was demonstrated by CDs-Tb-based paper sensor for high distinguishing ppGpp from other nucleotides with similar structure.

We summarize the construction methods and influencing factors of CDs-based composites and discuss their catalytic applications, including photocatalysis, chemical catalysis, peroxidase-like catalysis, Fenton-like catalysis and electrocatalysis.

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Cu(i)-CQDs with zigzag-shaped edges were prepared and used for a highly efficient catalysis of the Huisgen 1,3-dipolar cycloaddition that was made possible owing to their rapid release of Cu(i).