Room-temperature phosphorescence (RTP) materials are desirable in chemical sensing because of their long emission lifetime and they are free from background autofluorescence. Nevertheless, the achievement of RTP in aqueous solution is still a highly challenging task. Herein, a molten salt method to prepare carbon dot (CD)-based RTP materials is presented by direct calcination of carbon sources in the presence of inorganic salts. The resultant CD composites (CDs@MP) exhibit bright RTP with a quantum yield of 26.4% and a lifetime of 1.28 s, which lasts for about 6 s to the naked eye. Importantly, their aqueous dispersion also has good RTP characteristics. This is the first time that the long-lived CDs@MP with RTP are achieved in aqueous solution owing to the synergistic effect of crystalline confinement and aggregation-induced phosphorescence. Further investigations reveal that three key processes may be responsible for the observed RTP of the composite materials: (1) The rigid crystalline salt shell can preserve the triplet states of CDs@MP in water and suppress the nonradiative deactivation; (2) The addition of high-charge-density metal ions Mg­(II) and phosphorus element in the composite facilitates the singlet-to-triplet intersystem crossing process and enhances the RTP emission; (3) The aggregation of CDs@MP nanocomposites enables the matrix shell to self-assemble into a network, which further improves the rigidity of the shell and prevents the intermolecular motions, hence prolonging the RTP lifetime. The unique RTP feature and good water dispersibility allow the CD-based composite materials to be applicable in detection of temperature and pH in the aqueous phase. Our approach for producing long-lived RTP CDs@MP is effective, simple, and low-cost, which opens a new route to develop RTP materials that are applicable in aqueous solution.

The structural confinement and charge density engineering of molten salt endorsed CD-based room temperature phosphorescent (RTP) nanocomposites with long-lifetime, long-wavelength and excitation-dependent RTP.

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Driven by the urgent need for recognition and quantification of trace amino acids enantiomers in various biologic samples, we demonstrate for the first time an ultrasensitive electrochemical chiral biosensor for cysteine (Cys) based on magnetic nanoparticles (FeO@PDA/Cu O) as electrode units. d-Cys-Cu-d-Cys formed in the presence of cysteine exhibits strong stability and a shielding effect on the redox current of indicator Cu, which can be used to quantify and recognize d-Cys by square wave voltammetry. Simultaneous detection of d-Cys and homocysteine (Hcy) is achieved in the presence of other amino acids, demonstrating an excellent selectivity of the sensor. Moreover, aided by the enrichment treatment effect of magnetic micronanoelectrodes, an ultrahigh sensitivity up to 102 μA μM cm was achieved, the detection limit is reduced to picomolar level (83 pM) for d-Cys and can be used for the recognition of cysteine enantiomers. The proposed method has been verified by real sample analysis with satisfactory results. The results highlight the feasibility of our proposed strategy for magnetic micronanoelectrode sensor, electrochemical recognition, and quantification of d-Cys, which can be more broadly applicable than that with traditional electrode structures and further advance the field of electrochemical sensors.

Photodynamic therapy (PDT) has attracted wide attention due to its distinct advantages in cancer treatment. Herein, a kind of red emissive carbon dots (R-CDs) was synthesized from methylene blue (MB) and phosphate through a hydrothermal method. The resultant R-CDs display good biocompatibility, photostability, and high singlet oxygen ( 1 O 2 ) yield (0.91); thus, they have been successfully applied to the PDT study in vitro. More importantly, the R-CDs show noninfective property to DNA, which is substantially different to their precursor MB. The structure of R-CDs was comprehensively characterized both experimentally as well as by density functional theory (DFT) calculations. This study not only provides a rational strategy for preparation of highly efficient PDT material but also gives insight into the mechanism of 1 O 2 generation.

Turn-on thermosensitive carbon dots (CDs) with dual function of imaging and sensing are desirable for biological research and clinical diagnosis at cellular level. Herein, we synthesized eight types of novel...