In this paper, a novel, accurate, sensitive and rapid ratiometric fluorescent sensor was fabricated using a copper nanoclusters@infinite coordination polymer (ICP), specifically, terbium ion-guanosine 5’-disodium (Cu NCs@Tb-GMP) nanocomposites as the ratiometric fluorescent probe, to detect alkaline phosphatase (ALP) in water. The fluorescence probe was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The experimental results showed that, compared with Tb-GMP fluorescent sensors, Cu ratiometric fluorescent sensors based on NCs encapsulated in Tb-GMP had fewer experimental errors and fewer false-positive signals and were more conducive to the sensitive and accurate detection of ALP. In addition, the developed fluorescent probe had good fluorescence intensity, selectivity, repeatability and stability. Under optimized conditions, the ratiometric fluorescent sensor detected ALP in the range of 0.002–2 U mL⁻¹ (R² = 0.9950) with a limit of detection of 0.002 U mL⁻¹, and the recovery of ALP from water samples was less than 108.2%. These satisfying results proved that the ratiometric fluorescent probe has good application prospects and provides a new method for the detection of ALP in real water samples.

Herein, a non-stacked γ-Fe₂O₃/C@TiO₂ double-layer hollow nano photocatalyst has been developed with ultrathin nanosheets-assembled double shells for photodegradation phenol. High catalytic performance was found that the phenol could be completely degraded in 135 min under visible light, due to the moderate band edge position (VB at 0.59 eV and CB at −0.66 eV) of the non-stacked γ-Fe₂O₃/C@TiO₂, which can expand the excitation wavelength range into the visible light region and produce a high concentration of free radicals (such as ·OH, ·O²⁻, holes). Furthermore, the interior of the hollow composite γ-Fe₂O₃ is responsible for charge generation, and the carbon matrix facilitates charge transfer to the external TiO₂ shell. This overlap improved the selection/utilization efficiency, while the unique non-stacked double-layered structure inhibited initial charge recombination over the photocatalysts. This work provides new approaches for photocatalytic applications with γ-Fe₂O₃/C-based materials.

In this paper, the SQDs@MnO₂ NS as the probe was applied to construct a novel “turn-on” fluorescent sensor for sensitive and selective detection of hydrazine (N₂H₄). Sulfur quantum dots (SQDs) and MnO₂ nanosheets (MnO₂ NS) were simply mixed, through the process of adsorption to prepare the architectures of SQDs@MnO₂ NS. The fluorescent emissions of SQDs@MnO₂ NS play a key role to indicate the state of the sensor. According to the inner filter effect (IFE) mechanism, the state of the sensor at the “off” position, or low emission, under the presence of MnO₂ NS, is which the ultraviolet and visible spectrum overlaps with the fluorescence emission spectrum of SQDs. Under the optimal conditions, the emission was gradually recovered with the addition of the N₂H₄, since the N₂H₄ as a strong reductant could make the MnO₂ NS converted into Mn²⁺, the state of the sensor at the “on”. Meanwhile, the fluorescent sensor possesses good selectivity and high sensitivity, and the detection concentration of N₂H₄ with a wide range from 0.1 µM to 10 mM with a detection limit of 0.072 µM. Furthermore, actual samples were successful in detecting certain implications, indicating that the fluorescent sensor possesses the potential application ability to monitor the N₂H₄ in the water.