Exploring Solvent-Related Reactions and Corresponding Band Gap Tuning Strategies for Carbon Nanodots Based on Solvothermal Synthesis

Abstract

The role of the solvent in the solvothermal synthesis of carbon nanodots (CDs) is a long-standing puzzle for comprehensively understanding the CD formation mechanism and the relevant band gap tuning phenomenon. The controversy regarding solvent effect continues, largely because the importance of solvent-related reactions (SRs) has been ignored. In this Letter, we report that the SRs, i.e., oxidation-assisted solvent-involved dehydration and solvent-promoted oligomerization of phenylene/pyridinediamine (PD/PyD), are observed and dominate the formation of corresponding CDs by producing highly C2H4/C2H4O-featured species of precursors and PEG-like oligomer chains, which is very different from previously proposed theories. Moreover, our findings reveal that the photoluminescence (PL) of as-synthesized CDs originates from fluorophores formed by SRs and can be tailored by fluorophore engineering. Based on the SRs theory, three strategies for PL band gap tuning have been demonstrated.

One-step high-yield preparation of nitrogen- and sulfur-codoped carbon dots with applications in chromium(vi) and ascorbic acid detection

“… 43 Therefore, the effects of doping and strain may account for the variation in the Raman spectra. 48 …”

“…Although the veritable mechanism of fluorescent carbon dots is remain strongly debated, it has been confirmed that the photo-physical performances of CDs rely on the HOMO–LUMO energy gap, and the heteroatomic doping could tune the PL bandgap through expanding the conjugated field of the fluorophores. 48 The N and S atoms with many lone pair electrons lead to the availability of multiple isolated sp 2 conjugated carbon clusters. And isolated sp 2 conjugated carbon clusters can serve as valid radial centers enhancing the fluorescent performances of the CDs-IPM.…”

“…43 Therefore, the effects of doping and strain may account for the variation in the Raman spectra. 48 The sensing behavior of the CDs-IPM sensing system…”

Dual-emission carbon dots for sensitive fluorescence detection of metal ions and ethanol in water

“…Therefore, various solvents can be divided into three categories for analysis. [61][62][63] First, the strongest emission peak position of the CDs shows an obvious redshi with the gradual increase of the polarity of the solvent, accompanied by a decrease in uorescence intensity, when the protic solvent does not have functional groups (such as -OH and -COOH) that easily form hydrogen bonds (Fig. S9a †).…”

Acid-regulated boron–nitrogen codoped multicolor carbonized polymer dots and applications for pH sensing and trace water detection

“…17,18 Synergistic effects will occur when the fluorescence emissions of CPDs are regulated by the size of the sp 2 domain and the surface states. 19,20 Notably, most luminescence mechanisms of CPDs prepared from organic monomers by the bottom-up method are derived from synergistic effects. 21–23…”