No abstract

Solvent-controlled, pH-dependent and solvent-dependent strategies are proposed to obtain multicolor carbon dots using the same precursor.

Transforming carbon dots (CDs) fluorescent materials into smart materials with complex functions is a topic of great interest to nanoscience. However, designing CDs with regulating fluorescence/phosphorescence that can be visually monitored with the environment changes in real-time remains a challenge. Here, a very simple strategy, one-step solvent-free catalytic assistant strategy, which is low cost, facile, environment-friendly, and high throughput, is put forward. Hydrogen bond is used to manipulate nanostructure of CDs, and the obtained carbon dots (M-CDs) show a series of attractive properties including matrix-free room-temperature phosphorescence, time-dependent fluorescence, and near-infrared emissive characteristics. Different from the traditional aggregation caused quenching or aggregation-induced emission fluorescent materials, M-CDs exhibit unprecedented and unique dispersion induced redshift fluorescence phenomenon, promoting the studies of fluorescence from static to dynamic. The causes of this phenomenon are further analyzed in detail. As a kind of intelligent fluorescent materials, this new designed CDs greatly enrich the basic recognition of CDs by illustrating the relationship between redshift fluorescence behaviors and the dispersion states, and may provide with an opportunity for solid-state fluorescent materials, anti-counterfeiting, cellular imaging, and hopefully many others.

No abstract

Fluorescent carbon dots (CDs) have attracted growing attention and have exhibited widespread potential applications in photocatalysis, bioimaging, and optoelectronics in recent years. However, due to the complex structure of CDs, both the molecular ingredients and the intrinsic mechanisms governing the fluorescence (FL) of CDs are poorly understood. Herein, dual-emission N-doped carbon dots (N-CDs) were synthesized through the solvothermal reaction of p-phenylenediamine and folic acid in deionized water. Interestingly enough, the second emission band of N-CDs can be tuned by changing the polarity of the solvent, showing an obvious solvent dependence. The first emission band has obvious excitation-wavelength dependence, while the second emission band does not. The first emission band likely comes from diversified amide units, while the homogeneous polymers chains are the most likely origin of the second emission band. These findings greatly improve our understanding of the FL origin of CDs and help to guide future preparations of novel nanomaterials.