Carbon dots, as a potential substitute for semiconductor quantum dots, have drawn great interest in recent years. The preparation of fluorescent carbon dots has been made easy with many significant advances, but the complicated purifying processes, low quantum yield, and blue emission wavelength still limit its wider application in biosensors, biomedicine, and photonic devices. Here we report a strategy to synthesis Gd-doped carbon dots (Gd-Cdots) of super-high quantum yield with a microwave assisted hydrothermal method. The Gd-Cdots, with a diameter of 47∼8 nm, can be purified easily with conventional centrifugal techniques. Carbon microparticles (CMPs) have also been synthesized with a similar procedure. Meanwhile, we demonstrated a novel "turn-off-on" fluorescent biosensor, which has been developed for highly sensitive detection of glucose using Gd-doped carbon dots as probes. The proposed biosensor has exhibited low-cost and non-toxic properties, with high sensitivity and good specificity. In addition, the results in real blood samples further confirmed it as a promising application in diabetes diagnosis.

Carbon nanodots (C-dots), as a new emerging star, have attracted great attention in recent years. Its unique properties have been developed and applied to energy conversion/storage, bioimaging, drug delivery, sensor and other biological related aspects. In this review, we introduce various synthetic methods, basic photoluminscene properties, PL mechanism and then focus on the most recent progress in targeted drug and gene delivery guided by multimode bioimaging technologies in cancer therapy. We also speculate on an outlook towards future developments for their use in bioimaging, drug delivery, sensors, diagnostics and composites.

Due to the dual role as an electron acceptor and an electron donor in solution, carbon dots (Cdots) have broad applications in environmental analysis, biological detection, and biosensors. Herein, we report a facile-green strategy for a large-scale synthesis of fluorescent N, P-doped carbon dots (N, P-Cdots) with an absolute quantum yield of 66.08% by a simple one-step thermal decomposition. Glucose was selected as a carbon precursor and tryptophan (Trp) as an N-doping and passivation reagent. Organic polar solvents with a high boiling point, i.e., ethylene glycol and glycerol, were used as the reaction medium, and phosphoric acid was employed as a P source and oxidation accelerator. It is shown that the emission wavelength of the N, P-Cdots can be tuned by adjusting the reaction conditions, such as mass ratio, heating time, temperature, and medium, without further passivation. Finally, advantage was taken of the superior fluorescent characteristics of N, P-Cdots to detect selectively and with high sensitivity a cancer marker, carcinoembryonic antigen (CEA), based on the fluorescent quenching mechanism. Additionally, CEA was also detected in human serum samples with high efficiency and RSD, further confirming that the proposed method has a good consistency and stability for supersensitive fluorimetric detection of cancer markers.