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Exploring highly efficient electrocatalyst for H2O2 production based on two-electron oxygen reduction reaction (2e- ORR) is still a challenge. Herein, we design and fabricate a 3D interconnected P-doped nickel/porous carbon material (P-Ni/MC) through a NaCl template-assisted strategy. The interconnected macro/meso/micro-porous structure increases the specific surface area of catalyst with higher mass transfer rate, and the phosphating treatment endows the catalyst with a disordered amorphous state, which induces more active sites on catalyst surface and thus boosting their electrocatalytic performance for 2e- ORR. When tested in 0.1 M KOH, a considerable H2O2 yield of 4.40 mol h-1 gcat.-1 and an outstanding H2O2 selectivity over 98% can be obtained with decent electrochemical durability, which is 3-folds higher than that of Ni/MC without phosphating (1.46 mol h-1 gcat.-1). This strategy opens the eyes for developing highly efficient carbon-based catalyst for 2e- ORR by modulating its crystallinity through phosphating.

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.

In this work, fluorescent silicon nanoparticles (Si NPs) with good water solubility were facilely synthesized by one-step hydrothermal method. The obtained bright blue emitting Si NPs were employed as a fluorescent probe for simultaneously discriminating and sensitively quantifying two dihydroxybenzene (DHB) isomers (catechol (CC) and hydroquinone (HQ). Specifically, the fluorescence of Si NPs was dramatically quenched by HQ without a fluorescence shift. Interestingly, Si NPs revealed an obvious ratiometric fluorescent response characteristic toward CC, and an obvious fluorescent color change from bright blue to green was easily detected. Based on these, a simultaneous visual discrimination strategy for HQ and CC was proposed, and the determination of the concentration of HQ and CC with high sensitivity was obtained, respectively. The proposed strategy was also successfully applied to the assay of HQ and CC in real water samples. Moreover, the fabrication of luminescent test strip based on Si NPs and its application for straightforward visual discrimination of HQ and CC may open new applications of Si NPs in environmental chemistry.