Because 2,4,6-trinitrophenol (TNP) and its analogues such as 2,4,6-trinitrotoluene (TNT) possess similar chemical structures and properties, the reliable and accurate detection of TNP from its analogues still remains a challenging task. In the present work, a selective and sensitive method based on the water-soluble silicon nanoparticles (SiNPs) for the determination of TNP was established. The SiNPs with good thermostability and excellent antiphotobleaching capability were prepared via a simple one-pot method. Compared with the synthesized time of other nanomaterials with respect to the detection of TNP, this method avoided a multistep and time-consuming synthesis procedure. Significantly, the fluorescence of the SiNPs could be remarkably quenched by TNP via an inner filter effect. A wide linear range was obtained from 0.02 to 120 μg/mL with a limit of detection of 6.7 ng/mL. The method displayed excellent selectivity toward TNP over other nitroaromatic explosives. The proposed fluorescent method was successfully applied to the analysis of TNP. Moreover, a straightforward and convenient fluorescent filter paper sensor was developed for the detection of TNP, providing a valuable platform for TNP sensing in public safety and security.

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This work describes a "switch-on" fluorescence approach for sensing of ascorbic acid (AA) in food samples. In the present method, the fluorescence intensity (FL) of carbon quantum dots (CQDs) was first quenched by addition of MnO2 nanosheets through an inner filter effect to form a CQDs-MnO2 probe. When reductive AA was introduced into the quenched CQDs solution, the added MnO2 was destroyed due to the redox reaction between AA and MnO2 nanosheets, and the FL of the system was recovered. Under the optimal conditions, the limit of detection for AA was 42 nM, with a wide concentration linear range of 0.18-90 μM. Furthermore, the as-fabricated fluorescent sensing system was successfully applied to the analysis of AA in fresh fruits, vegetables, and commercial fruit juices samples with satisfactory results.

A sensitive and selective fluorescence "turn-off" sensor to detect heparin using water-soluble silicon nanoparticles (Si NPs) was developed for the first time. The Si NPs were synthesized by a simple one-step procedure, which did not need high-temperature and complex modification. The as-prepared Si NPs featured strong fluorescence, favorable biocompatibility, and robust photo- and pH stability. Significantly, the Si NPs were induced to assemble or aggregate via hydrogen bonding, which resulted in the fluorescence of Si NPs quenched. Under the optimized conditions, the linear range was obtained from 0.02 to 2.0 μg/mL, with a limit of detection of 18 ng/mL (equal to 0.004 U/mL). It was lower than the proper therapeutic level of heparin during cardiovascular surgery and long-term therapy. This proposed method was relatively free of interference from heparin analogues, which commonly existed in heparin samples and could possibly affect heparin detection. Moreover, it did not need to introduce any control medium. As expected, the method was successfully applied to detect heparin in human serum samples with satisfactory recovery ranging from 98.8 to 102.5%. The Si NPs were superbly suitable for cell imaging owing to the negligible cytotoxicity and excellent biocompatibility.

The synthesis of dual-emissive carbon dots (CDs) with a longer emission wavelength by using a facile strategy is of great importance for the fabrication of ratiometric fluorescent nanoprobes. Herein, red/green dual-emissive carbon dots (RGDE CDs) were synthesized in one step using 2,5-diaminotoluene sulfate (DATS) as a carbon source. The as-prepared RGDE CDs not only exhibited dual emission fluorescence peaks (525 nm, 603 nm) at the single excitation wavelength of 370 nm, but also possessed good water solubility and excellent fluorescence stability. Moreover, the as-prepared RGDE CDs could be directly utilized as a ratiometric fluorescent probe for the determination of trace ONOO- due to the electron transfer process from ONOO- to the excited RGDE CDs. Under optimal conditions, the linear range was 0.03-60 μM with the limit of detection of 11.6 nM. Importantly, this RGDE CD probe could be applied for the detection of intracellular ONOO- with excellent biocompatibility and cellular imaging capability, indicating great promise in biomedical applications.