Graphene quantum dots (GQDs) that are flat 0D nanomaterials have attracted increasing interest because of their exceptional chemicophysical properties and novel applications in energy conversion and storage, electro/photo/chemical catalysis, flexible devices, sensing, display, imaging, and theranostics. The significant advances in the recent years are summarized with comparative and balanced discussion. The differences between GQDs and other nanomaterials, including their nanocarbon cousins, are emphasized, and the unique advantages of GQDs for specific applications are highlighted. The current challenges and outlook of this growing field are also discussed.

/pdf/recent-advances-on-graphene-quantum-dots-from-chemistry-and-1d6dzbzh6n.pdf

Recent Advances on Graphene Quantum Dots: From Chemistry and Physics to Applications

Graphene quantum dots from chemistry to applications

Using atomic force microscopy nanomanipulation, we position a single Au nanoparticle near a CdSe/ZnS quantum dot to construct a hybrid nanostructure with variable geometry. The coupling between the two particles is varied in a systematic and reversible manner. The photoluminescence lifetime and blinking of the same quantum dot are measured before and after assembly of the structure. In some hybrid structures, the total lifetime is reduced from about 30 ns to well below 1 ns. This dramatic change in lifetime is accompanied by the disappearance of blinking as the nonradiative energy transfer from the CdSe/ZnS quantum dot to the Au nanoparticle becomes the dominant decay channel. Both total lifetime and photoluminescence intensity changes are well described by simple analytical calculations.

http://absimage.aps.org/image/MAR11/MWS_MAR11-2010-002213.pdf

Manipulating coupling between a single semiconductor quantum dot and single gold nanoparticle

Photo-and Electroluminescence from Nitrogen-Doped and Nitrogen–Sulfur Codoped Graphene Quantum Dots

Graphene quantum dots, the next generation carbon based nanomaterials, due to their outstanding physical, chemical and biological properties, have shown potential in revolutionizing the future of nanomedicine and biotechnology. Their strong size-dependent photoluminescence (PL) and the presence of reactive groups on the GQD surface, which allow their multimodal conjugation with various functional groups and biologically active molecules, make them ideal candidates for cancer diagnosis and treatment. GQDs have been loaded with drugs and labeled with tumor-targeting ligand units that are able to specifically recognize cancer receptors exposed on the cancer cell surface by generating new therapies that are able to allow a more efficient targeted delivery of anticancer agents while minimizing their distribution in healthy tissues, as well as the development of new imaging agents for the in vitro and in vivo diagnosis of several types of cancer. Here, we review the recent advances in the study of the application of GQDs as nanoplatforms for anticancer therapy, taking into account the methods used for their synthesis and functionalization procedures, which can deeply affect their biocompatibility and their electronic and optical features. The biosafety and toxicity aspects of these nanomaterials at cellular and animal levels, mainly related to their size and the kind and degree of surface functionalization, are also discussed.

Graphene quantum dots: multifunctional nanoplatforms for anticancer therapy

Aromatic nitrogen doped graphene quantum dots were investigated by steady-state and time-resolved photoluminescence (PL) techniques. The PL lifetime was found to be dependent on the emission wavelength and coincident with the PL spectrum, which is different from most semiconductor quantum dots and fluorescent dyes. This result shows the synergy and competition between the quantum confinement effect and edge functional groups, which may have the potential to guide the synthesis and expand the applications of graphene quantum dots.

The emission wavelength dependent photoluminescence lifetime of the N-doped graphene quantum dots

We investigated the strong interaction between graphene quantum dots and silver nanoparticles in solution using time-resolved photoluminescence techniques. In solution, the silver nanoparticles are surrounded by graphene quantum dots and interacted with graphene quantum dots through exciton-plasmon coupling. An ultrafast spontaneous emission process (lifetime 27 ps) was observed in such a mixed solution. This ultrafast lifetime corresponds to the emission rate exceeding 35 GHz, with the purcell enhancement by a factor of ∼12. These experiment results pave the way for the realization of future high speed light sources applications.

Xingxia Deng

Papers

The emission wavelength dependent photoluminescence lifetime of the N-doped graphene quantum dots

Ultrafast spontaneous emission modulation of graphene quantum dots interacting with Ag nanoparticles in solution