Ultrastable Amine, Sulfo Cofunctionalized Graphene Quantum Dots with High Two-Photon Fluorescence for Cellular Imaging

Abstract

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.

Sustainable Synthesis of Bright Green Fluorescent Nitrogen‐Doped Carbon Quantum Dots from Alkali Lignin

“…It is worth noting that for the triplet carbene structure, the energy difference (DE)b etween the s and p orbitals should be below 1.5 eV. [51] In our work, DE is calculated to be 1.47 eV,w hich falls within the range of values required for the free carbene and indicates that the emission mechanism is reasonable. More interestingly, the fluorescenceo fp repared CQDs showed ar edshift from blue, observed in the previous report, to green.…”

“…These can be seen as transitions from the HOMO to the LUMO, corresponding to the π→π* transition of the aromatic ring and the n→π* transition of the conjugate N, as shown in Figure c. Therefore, we conclude that the excitation band at 420 nm may be attributed to the HOMO→LUMO transition of the N state in the CQDs. It is worth noting that for the triplet carbene structure, the energy difference (Δ E ) between the σ and π orbitals should be below 1.5 eV . In our work, Δ E is calculated to be 1.47 eV, which falls within the range of values required for the free carbene and indicates that the emission mechanism is reasonable.…”

Facile preparation of high fluorescent carbon quantum dots from orange waste peels for nonlinear optical applications

“…As seen in Figure , absorption intensity increased at different concentrations, as the intensity of the fluorescence spectrum increased. The absorption and emission edges are a clear indication of a visible light response from the particles, indicating that CQDs could be used for various fluorescence and biological applications …”

Graphene Quantum Dots for Optical Bioimaging

“…c,d) Two‐photon cell imaging under 800 nm excitation. Reproduced with permission . Copyright 2018, American Chemical Society.…”