Bismuth-Decorated Honeycomb-like Carbon Nanofibers: An Active Electrocatalyst for the Construction of a Sensitive Nitrite Sensor.

The existence of carcinogenic nitrites in food and the natural environment has attracted much attention. Therefore, it is still urgent and necessary to develop nitrite sensors with higher sensitivity and selectivity and expand their applications in daily life to protect human health and environmental safety. Herein, one-dimensional honeycomb-like carbon nanofibers (HCNFs) were synthesized with electrospun technology, and their specific structure enabled controlled growth and highly dispersed bismuth nanoparticles (Bi NPs) on their surface, which endowed the obtained Bi/HCNFs with excellent electrocatalytic activity towards nitrite oxidation. By modifying Bi/HCNFs on the screen-printed electrode, the constructed Bi/HCNFs electrode (Bi/HCNFs-SPE) can be used for nitrite detection in one drop of solution, and exhibits higher sensitivity (1269.9 µA mM-1 cm-2) in a wide range of 0.1~800 µM with a lower detection limit (19 nM). Impressively, the Bi/HCNFs-SPE has been successfully used for nitrite detection in food and environment samples, and the satisfactory properties and recovery indicate its feasibility for further practical applications.

Dual-readout performance of Eu3+-doped nanoceria as a phosphatase mimic for degradation and detection of organophosphate.

Eu3+-Doped nanoceria (Eu:CeO2) with self-integrated catalytic and luminescence sensing functions was synthesized by a simple and gentle one-pot method to build a dual-readout nanozyme platform for organophosphate compound (OPC) sensing in this work. The catalytic degradation of the model substrate of OPC, p-nitrophenyl phosphate (p-NPP), by as-prepared Eu:CeO2 can be completed in 2 min with little influence of temperature and pH values, highlighting the advantages of Eu:CeO2 as an artificial enzyme for dephosphorylation. Most importantly, the characteristic red emission of Eu3+ (592 nm) from Eu:CeO2 can be quenched by p-NPP, accompanied by a color change from colorless to yellow. Based on this, linear ranges of 4-50 µM with a detection limit of 3.3 µM and 1-20 µM with a detection limit of 0.6 µM for p-NPP were obtained by colorimetric and fluorescence methods, respectively. Furthermore, the fluorescence strategy was effectively applied to the determination of ethyl para-nitrophenyl (EPN), one of the most commonly used pesticides, with a detection limit of 5.86 µM. The proposed strategy was also successfully applied to the assay of p-NPP and EPN in real water samples, showing great application prospects in detecting OPC in the environment.

Silicon nanoparticles-based ratiometric fluorescence platform: Real-time visual sensing to ciprofloxacin and Cu2.

In this work, a silicon nanoparticles (Si NPs)-based ratiometric fluorescence sensing platform was conveniently fabricated by simply mixing fluorescent Si NPs as co-ligands and reference signal with lanthanide metal ion Eu3+ as response signal. The introduction of ciprofloxacin (CIP) remarkably turned on the characteristic fluorescence of Eu3+ at 590 nm and 619 nm through the "antenna effect". At the same time, the blue emission of Si NPs at 445 nm kept comparatively stable. A good linear relationship between the ratio fluorescence intensity and CIP concentration in the range of 0.211-132.4 µM with a limit of detection (LOD) of 89 nM was obtained. In the presence of Cu2+, the fluorescence emission of Eu3+ was sharply turned off because of the stronger coordination ability of Cu2+ with CIP, which guaranteed the sequential detection of Cu2+. Meanwhile, the distinct fluorescent color change from bright blue to red, then back to blue, enabled naked-eye visual detection of CIP and Cu2+ in the solution phase and on paper-based test strip, and was successfully applied to determine the levels of CIP in complicated food samples with high sensitivity.