Highly photoluminescent nitrogen-doped carbon nanoparticles (N-CNPs) were prepared by a simple and green route employing sodium alginate as a carbon source and tryptophan as both a nitrogen source and a functional monomer. The as-synthesized N-CNPs exhibited excellent water solubility and biocompatibility with a fluorescence quantum yield of 47.9%. The fluorescence of the N-CNPs was intensively suppressed by the addition of ascorbic acid (AA). The mechanism of the fluorescence suppression of the N-CNPs was investigated, and the synergistic action of the inner filter effect (IFE) and the static quenching effect (SQE) contributed to the intensive fluorescence suppression, which was different from those reported for the traditional redox-based fluorescent probes. Owing to the spatial effect and hydrogen bond between the AA and the groups on the N-CNP surface, excellent sensitivity and selectivity for AA detecting was obtained in a wide linear relationship from 0.2 μM to 150 μM. The detection limit was as low as 50 nM (signal-to-noise ratio of 3). The proposed sensing systems also represented excellent sensitivity and selectivity for AA analysis in human biological fluids, providing a valuable platform for AA sensing in clinic diagnostic and drug screening.

[1] Using in situ data from 88 cruises from 1987 to 2009 in the East China Sea, downstream nutrient flux (the product of velocity and nutrient concentration) and nutrient transport (integration of flux over a section) by Kuroshio were examined. The presence of a maximum nutrient flux core in the middle layer was confirmed. Seasonal variation in the nutrient flux was not significant and was much smaller than interannual variations. The change in the Kuroshio speed and current structure were major causes for interannual variations in the nutrient flux. The downstream nitrate transport by the Kuroshio in the East China Sea had a mean value of 170.8 kmol s À1 and a standard deviation of 41.6 kmol s À1. The mean seasonal nitrate transport ranged between about 161 and 177 kmol s À1 and the absolute interannual variation from about 100 to 280 kmol s À1. The phosphate flux and phosphate transport can be approximately estimated by the ratio (13.64) of nitrate concentration to phosphate concentration. The nitrate concentration in the middle and bottom layers across the Kuroshio in the East China Sea was found to increase significantly over the 23 year period, and especially after 2004 but not at ratios with oxygen that suggest increased remineralization of organic matter. The nutrient transport, however, did not increase significantly because increases in the surface layer were offset by decreases in the middle and bottom layers caused by reduction in velocity in the density ranges of 26.0 to 27.2 s q below the Kuroshio.

Pacific Decadal Oscillation (PDO) index is strongly correlated with vertically integrated transport carried by the Kuroshio through the East China Sea (ECS). Transport was determined from satellite altimetry calibrated with in situ data and its correlation with PDO index (0.76) is highest at zero lag. Total PDO‐correlated transport variation carried by the ECS‐Kuroshio and Ryukyu Current is about 4 Sv. In addition, PDO index is strongly negatively correlated, at zero lag, with NCEP wind‐stress‐curl over the central North Pacific at ECS latitudes. Sverdrup transport, calculated from wind‐stress‐curl anomalies, is consistent with the observed transport variations. Finally, PDO index and ECS‐Kuroshio transport are each negatively correlated with Kuroshio Position Index in the Tokara Strait; this can be explained by a model in which Kuroshio path is steered by topography when transport is low and is inertially controlled when transport is high.

A Ti3C2QD-based fluorescent probe for an ALP activity assay and embryonic stem cell identification was developed by taking advantage of the inner filter effect.

Carbon coated hollow mesoporous FeP microcubes derived from Prussian blue were superior in catalytic activity and durability toward electrochemical hydrogen evolution with an overpotential of 115 mV to drive 10 mA cm−2.

A simple one-step ultrasonic method was developed for the synthesis of luminescent MnO2 quantum dots (MnO2 QDs) in the presence of cysteine, in which cysteine acted as the exfoliating agent and stabilization ligand. The cysteine-stabilized MnO2 QDs (Cys-MnO2 QDs) possess a fluorescence quantum yield of 4.7%, and the fluorescence intensity of Cys-MnO2 QDs is sensitive to dopamine (DA). The mechanism by which the Cys-MnO2 QDs catalyzed the self-polymerization of DA to form polydopamine nanoparticles (PDA NPs) and caused the fluorescence resonance energy transfer (FRET) between MnO2 QDs and PDA NPs was revealed. The sensing platform displayed a wide detection range (0.1–200 μM) with a low detection limit of 28 nM for the detection of DA. Moreover, the Michael addition/Schiff base reaction between the PDA NPs and cysteine on MnO2 QDs was demonstrated to facilitate the excellent selectivity toward DA detection in the presence of various interferences. This work not only develops a robust method for the preparation of highly luminescent MnO2 QDs but also provides a universal strategy on the basis of surface chemical reaction-induced FRET for the detection of DA with high sensitivity and selectivity, which is promising in the application of clinical diagnosis, drug delivery, and fluorescence-guided cancer therapy.

[1] Two detachment processes of low salinity water (LSW) in the Changjiang Estuary in July 2006, and the role of wind on detaching the LSW in particular, are explored with a three-dimensional numerical model. The real-case simulation and the sensitivity experiments results show that wind plays a crucial role in the detachment events and is highlighted in three aspects. First, wind is the most important dynamic factor in the two detachment processes of the LSW. Wind mixing, wind-driven northward current and wind-induced upwelling are three driving forces on detaching the LSW, which increase the salinity in the upper layer in the detachment region along the 30 m isobath and separate the offshore LSW from the nearshore main body of LSW. The diagnostic analysis further indicates that the increase of salinity in the detachment region is mainly due to northward current which transports high salinity water from the south. Second, a critical wind speed, namely a southeasterly wind above 8.0 m/s, is found to be related to the timing of the detachment events. A sensitivity experiment further confirms this critical wind speed and no detachment occurs when the wind speed is below 8.0 m/s. Third, the southwesterly wind plays a key role in the magnitude of the spatial size of the detached LSW. Before the detachment occurs, a persistent southwesterly wind induces northeastward expansion of the LSW and consequently forms larger LSW offshore after detachment, which is verified by another sensitivity experiment with modified wind direction.

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