Quantum dots have innate advantages as the key component of optoelectronic devices. For white light–emitting diodes (WLEDs), the modulation of the spectrum and color of the device often involves various quantum dots of different emission wavelengths. Here, we fabricate a series of carbon quantum dots (CQDs) through a scalable acid reagent engineering strategy. The growing electron-withdrawing groups on the surface of CQDs that originated from acid reagents boost their photoluminescence wavelength red shift and raise their particle sizes, elucidating the quantum size effect. These CQDs emit bright and remarkably stable full-color fluorescence ranging from blue to red light and even white light. Full-color emissive polymer films and all types of high–color rendering index WLEDs are synthesized by mixing multiple kinds of CQDs in appropriate ratios. The universal electron-donating/withdrawing group engineering approach for synthesizing tunable emissive CQDs will facilitate the progress of carbon-based luminescent materials for manufacturing forward-looking films and devices.

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Here we introduce a simple, superfast, and scalable strategy that obtains graphene quantum dots (GQDs) within 3 min under microwave irradiation (MA-GQDs). The MA-GQDs exhibit excellent fluorescence quantum yields up to 35% in the optimum reaction condition. The MA-GQDs with single-crystalline and few-layer structure can reach the visible region with the longest absorption wavelength at 700 nm. Moreover, these ultrabright-fluorescence and stable MA-GQDs as a phosphor and fluorescence probe could be efficiently applied in white light-emitting diodes and cell-imaging fields. The developed pathway to GQDs can provide unambiguous and remarkable insights into the design of high-fluorescence and few-defect GQDs, and expedite the applications of GQDs.

Fluorescent probes with superior two-photon fluorescence are highly attractive in the field of bioimaging. Herein, we report a one-pot hydrothermal route to synthesis amine, sulfo cofunctionalized graphene quantum dots (GQDs), which acts as efficient one-photon and two-photon fluorescent probes for cellular imaging. As synthesized GQDs exhibit ultrastability due to the edge-site functionalization of amine and sulfo groups. In addition, GQDs display attractive two-photon fluorescence properties. The two-photon absorption cross section of GQDs reaches up to 31,000 GM, which substantially exceeds that of the majority of traditional fluorescent materials. Furthermore, the noncytotoxicity GQDs exhibit a negligible photothermal effect under 808 nm femtosecond laser irradiation, which is suitable for long-term two-photon imaging and observation. These findings open new possibilities for using two-photon fluorescent GQDs in various biological applications.