Red-emitting carbon dots (CDs) have attracted tremendous attention due to their wide applications in areas including imaging, sensing, drug delivery, and cancer therapy. However, it is still highly...

Nucleolus-Targeted Red Emissive Carbon Dots with Polarity-Sensitive and Excitation-Independent Fluorescence Emission: High-Resolution Cell Imaging and in Vivo Tracking

Multicolor bandgap fluorescent carbon quantum dots (MCBF-CQDs) from blue to red with quantum yield up to 75% are synthesized using a solvothermal method. For the first time, monochrome electroluminescent light-emitting diodes (LEDs) with MCBF-CQDs directly as an active emission layer are fabricated. The maximum luminance of blue LEDs reaches 136 cd m-2 , which is the best performance for CQD-based monochrome electroluminescent LEDs.

Bright Multicolor Bandgap Fluorescent Carbon Quantum Dots for Electroluminescent Light-Emitting Diodes

Recent advances and prospects of carbon dots in phototherapy

Carbon dots (CDs) are a new type of carbon nanomaterial that have unique physical and chemical properties, good biocompatibility, low toxicity, and easy surface functionalization, making them widely used in biological imaging, environmental monitoring, chemical analysis, targeted drug delivery, disease diagnosis, therapy, etc. In this review, our content is mainly divided into four parts. In the first part, we focused on the preparation methods of CDs, including arc discharge, laser ablation, electrochemical oxidation, chemical oxidation, combustion, hydrothermal/solvent thermal, microwave, template, method etc. Next, we summarized methods of CD modification, including heteroatom doping and surface functionalization. Then, we discussed the optical properties of CDs (ultraviolet absorption, photoluminescence, up-conversion fluorescence, etc.). Lastly, we reviewed the common applications of CDs in biomedicine from the aspects of in vivo and in vitro imaging, sensors, drug delivery, cancer theranostics, etc. Furthermore, we also discussed the existing problems and the future development direction of CDs.

Carbon dots: synthesis, properties and biomedical applications

Recently, graphene quantum dots (GQDs) have been extensively studied in biomedical areas such as bio-imaging, bio-sensing and photothermal therapy due to their superior optical and physiochemical properties compared to traditional organic biomarkers. Application of GQDs in photodynamic therapy (PDT) has been explored since 2014, but currently the main challenges are inadequate singlet oxygen (1O2) quantum yield (QY), poor solubility and biocompatibility. Herein, we report on the synthesis of a new class of fluorine-containing GQDs (F-GQDs) by an oxidative cutting method using fluorinated graphite as the raw material. The as-synthesized F-GQD sample demonstrates an average particle size of 2.1 nm with a fluorine doping content of 1.43%. The F-GQDs have a better water solubility and biocompatibility than the GQDs, and emit strong green fluorescence at 365 nm excitation with a relative fluorescence QY of 13.72%. Moreover, the fluorescence imaging effect as well as photodynamic activity was successfully tested in both an in vitro HepG2 cell line model and a 3D multicellular spheroid model, the latter of which mimics the tumour microenvironment. Further studies using UV-visible spectroscopy to monitor the degradation of water-soluble 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABDA) demonstrate that the F-GQD sample generates 1O2 efficiently (QY = 0.49) under visible light irradiation. Compared to non-fluorinated GQDs, the as-reported F-GQDs appear to be a more promising photosensitizer for image-guided PDT.

Fluorine-containing graphene quantum dots with a high singlet oxygen generation applied for photodynamic therapy

Red emissive carbon dots (CDs) have attracted more and more attention in biological fields, due to less interference from autofluorescence of the biological matrix and lower photodamage to biological tissues. Herein, N and P co-doped red emissive carbon dots (R-CDs) were firstly prepared with o-phenylenediamine and phosphoric acid as the raw materials using a facile hydrothermal method. The R-CDs exhibited excitation-independent emission peaks at 622 nm with an absolute fluorescence quantum yield (QY) of 15% in water. At the same time, N-doped yellow emissive carbon dots (Y-CDs) were also synthesized with o-phenylenediamine using a similar procedure to that used for the R-CDs. Both CDs were successfully applied to in vitro cell imaging. By comparing the optical properties and surface states of the Y-CDs and R-CDs, we concluded that the photoluminescence (PL) of the CDs is related to the surface states of both CDs, and the surface functional group CO plays the main role in the yellow emission, while the new surface state introduced by doping phosphorus atoms into the R-CDs is responsible for the red emission. More importantly, the R-CDs had an excellent capability for killing cancer cells and inhibited the growth of a tumor under 532 nm laser irradiation. This work provides a novel strategy for preparing red emissive CDs and expands the application of CDs in biological fields.

Ying An

Papers

Preparation of N-doped yellow carbon dots and N, P co-doped red carbon dots for bioimaging and photodynamic therapy of tumors