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In this work, highly photoluminescent glycine (GLY) functionalized graphene quantum dots (GQDs) (GLY-GQDs) were synthesized by a simple and green pyrolysis method employing ethylene glycol as carbon source, GLY as functional molecule. The as-synthesized GLY-GQDs exhibited excellent water solubility with a fluorescence quantum yield of 21.7%. The fluorescence of GLY-GQDs was intensively quenched by Ce 4+ via forming non luminescent complexes of GLY-GQDs-Ce 4+ . When ascorbic acid (AA) was in presence, Ce 4+ was reduced to Ce 3+ and the fluorescence of GLY-GQDs regained. In the light of this theory, a simple AA sensor was fabricated without complicated, costly and time-consuming operations. Under the optimal conditions, the fluorescence recovery ratio and the concentration of AA has a linear relationship in the range of 0.03–17.0 μM and with a detection limit of 25 nM which was one order higher sensitive than the reported methods Furthermore, this established sensor system also shows a high selectivity toward AA over a wide range of common biological molecules such as uric acid, dopamine and glutathione and so on. The proposed method was successfully applied for the AA detection in serum samples. All these suggested the potential of this GLY-GQDs based sensor in the clinical analysis. [ABSTRACT FROM AUTHOR]

We design a novel high throughput photonic crystal microsphere (PHCM) suspension array for multiplex mycotoxins in cereal samples based on the aptamer fluorescence signal recovery. The hybridization duplex strand DNA from mycotoxin aptamer and anti-aptamer respectively labeled with fluorescence dye and quencher was immobilized on the carboxylated surfaces of PHCMs. When the corresponding mycotoxin targets bind to their aptamers, the fluorescence recovery signal intensity of PHCMs reported the concentration of mycotoxins. The different kinds of mycotoxins were distinguished by the structure colors of PHCMs. The fluorescence signal intensity on the PHCMs is nearly higher 100 times than that of solid glass beads. The detection system presents an ultrasensitive, high selectivity, and small volume reagent screening for multiplex mycotoxins with a dynamic linear detection range of 0.1 pg/mL–0.1 ng/mL for AFB1/OTA and 0.1 ng/mL–10 ng/mL for FB1 and a limit of detection (LOD) of 15.96 fg/mL, 3.96 fg/mL and 11.04 pg/mL for AFB1, OTA and FB1, respectively. The recovery rates in spiked cereal samples were well consistent with that of the traditional ELISA. The designed system provides a new high throughput aptamer-based suspension array for small molecule screening in parallel. [ABSTRACT FROM AUTHOR]

Novel fluorescent thioglycollic acid (TGA) surface-functionalized single-layered thickness structured MoS 2 nanosheets were purposely synthesized by a facile one-step hydrothermal treatment of using molybdenyl acetylacetonate, TGA and sodium sulfide as precursors. During the process of synthesis, we subtly solved the problem of the poor water solubility of the precursor molybdenyl acetylacetonate, and obtained thiolated single-layer MoS 2 nanosheet (TGA-MoS 2 ) with excellent water solubility and stable fluorescence property. The fluorescence of TGA-modified MoS 2 nanosheets was significantly suppressed in the presence of dopamine (DA), and a simple sensing system for highly selective, fast, direct detection of dopamine was established. Meanwhile, the present methodology has a wide detection range of 0.05 μΜ to 20 μΜ, a comparable detection limit of 27 nM and an extremely short response time of 3 min. To understand the fast response behavior, we tried effort to explain the interaction mechanisms between TGA-MoS 2 nanosheets and the quencher DA. Further research suggests that the possible mechanism might be the charge transfer (CT) by the stacking of MoS 2 layers through C O⋯H O hydrogen boding interaction, providing a fast fluorescence sensing platform for DA determination in urine and serum sample. [ABSTRACT FROM AUTHOR]