To obtain graphene-based fluorescent materials, one of the effective approaches is to convert one-dimensional (1D) graphene to 0D graphene quantum dots (GQDs), yielding an emerging nanolight with extraordinary properties due to their remarkable quantum confinement and edge effects. In this review, the state-of-the-art knowledge of GQDs is presented. The synthetic methods were summarized, with emphasis on the top-down routes which possess the advantages of abundant raw materials, large scale production and simple operation. Optical properties of GQDs are also systematically discussed ranging from the mechanism, the influencing factors to the optical tunability. The current applications are also reviewed, followed by an outlook on their future and potential development, involving the effective synthetic methods, systematic photoluminescent mechanism, bandgap engineering, in addition to the potential applications in bioimaging, sensors, etc.

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The development of nanotechnology provides promising opportunities for various important applications. The recent discovery of atomically-thick two-dimensional (2D) nanomaterials can offer manifold perspectives to construct versatile devices with high-performance to satisfy multiple requirements. Many studies directed at graphene have stimulated renewed interest on graphene-like 2D layered nanomaterials (GLNs). GLNs including boron nitride nanosheets, graphitic-carbon nitride nanosheets and transition metal dichalcogenides (e.g. MoS2 and WS2) have attracted significant interest in numerous research fields from physics and chemistry to biology and engineering, which has led to numerous interdisciplinary advances in nano science. Benefiting from the unique physical and chemical properties (e.g. strong mechanical strength, high surface area, unparalleled thermal conductivity, remarkable biocompatibility and ease of functionalization), these 2D layered nanomaterials have shown great potential in biochemistry and biomedicine. This review summarizes recent advances of GLNs in applications of biosensors and nanomedicine, including electrochemical biosensors, optical biosensors, bioimaging, drug delivery and cancer therapy. Current challenges and future perspectives in these rapidly developing areas are also outlined. It is expected that they will have great practical foundation in biomedical applications with future efforts.

In this Article, we present a facile microwave-assisted synthesis route for the preparation of water-soluble and high-quality CuInS2/ZnS nanocrystals (NCs) with glutathione as the stabilizer. The as-prepared CuInS2/ZnS NCs exhibited small particle sizes (~3.3 nm), long photoluminescence lifetimes, and color-tunable properties ranging from the visible to the near-infrared by varying the initial ratio of Cu/In in the precursors. The low-toxicity, highly luminescent and biocompatible CuInS2/ZnS NCs were applied to cell imaging, showing that they could be used as promising fluorescent probes. Furthermore, the CuInS2/ZnS NCs were used as the signal labels for a fluoroimmunoassay of the biomarker IL-6, showing their great potential for use as reliable point-of-care diagnostics for biomarkers of cancer and other diseases.

A novel strategy is reported for the fabrication of poly(diallyldimethylammonium chloride) (PDDA)-protected graphene-CdSe (P-GR-CdSe) composites. An advanced electrogenerated chemiluminescence (ECL) immunosensor is proposed for the sensitive detection of human IgG (HIgG) by using the as-prepared P-GR-CdSe composites. The P-GR-CdSe composite fi lm shows high ECL intensity, good electronic conductivity, fast response, and satisfactory stability, all of which holds great promise for the fabrication of ECL biosensors with improved sensitivity. After two successive steps of amplifi cation via the conjugation of PDDA and gold nanoparticles (GNPs) in the fi lm, high ECL intensity is observed. The ECL immunosensor has an extremely sensitive response to HIgG in a linear range of 0.02-2000 pg mL − 1 with a detection limit of 0.005 pg mL − 1 . The proposed sensor exhibits high specifi city, good reproducibility, and longterm stability, and may become a promising technique for protein detection.

A facile in situ assembly strategy was developed for the fabrication of Pt-Au alloy nanoparticles (NPs) on nitrogen-doped graphene (N-G) sheets, and the as-fabricated Pt-Au/N-G nanocomposites were suitable for electrochemical applications. As characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis and inductively coupled plasma-atomic emission spectroscopy techniques, Pt-Au alloy NPs with an average size of 4-5 nm were uniformly distributed on the N-G surface through intrinsic covalent bonds. The Pt-Au/N-G nanocomposites exhibited excellent electrocatalytic activity and stability towards the methanol oxidation reaction with the highest capability observed for a Pt/Au atomic ratio of 3/1. The unique electrochemical features are distinctive from those of N-free nanocomposites and commercially available Pt/C catalysts, indicative of the alloying effect of Pt-Au and their synergistic interaction with the N-G sheet, which may open up new possibilities for the preparation of N-G-based nanocomposites for other intensive applications as well.

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