We demonstrated a non-enzymatic cholesterol sensor based on a nickel oxide (NiO) and high quality graphene composite for the first time. Graphene was grown by a chemical vapor deposition technique (CVD). The nanocomposite was fabricated through the electrodeposition of nickel hydroxide onto the surface of the CVD-grown graphene, which was followed by thermal annealing. The successful formation of the NiO/graphene composite was confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The deposition of flower-like NiO onto the graphene surface was confirmed by scanning electron microscopy. Electrochemical analyses were conducted to investigate the characteristics of the sensor during the detection of cholesterol. The sensor showed a high sensitivity of 40.6 mA mM À1 cm À2 , a rapid response time of 5 s, and a low detection of limit of 0.13 mM. We also investigated the effects of common interfering substances on the ability of the sensor to detect cholesterol. Furthermore, we successfully determined the cholesterol in a milk sample using the developed sensor. The composite electrode exhibited excellent detection of cholesterol with good reproducibility and long-term stability owing to the combined effects of NiO and graphene.

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The forest-like NiS hierarchical architectures demonstrated superior electrochemical performance with excellent cycling stability.

Cesium lead bromide perovskite quantum dots (PQDs) have recently attracted much attention because of their remarkable optoelectronic properties, such as high photoluminescence quantum efficiency, narrow emission, tunable wavelength, and color purity. However, despite these excellent properties, their instability in the case of prolonged exposure to humidity, pH, and/or temperature limits their applicability. Here, we propose a simple and portable cellulose-based colorimetric sensor integrated with CsPbBr3 PQDs for the rapid naked-eye detection of chlorine and iodine ions. We synthesized the CsPbBr3 PQDs/cellulose composite via a hot injection method, which allows the formation of monodispersed CsPbBr3 PQDs with high sensitivity; given the strong adherence of the CsPbBr3 PQDs to the porous cellulose fibers, the composite exhibited excellent stability and durability against various humidity conditions along with superior photoluminescence properties. When applying our CsPbBr3 PQDs/cellulose composite as an early diagnosis sensor, we observed a remarkable color change at a fast rate (within 5 s) after the introduction of the sample solution, resulting from its rapid diffusion into the porous cellulose network, that could be quantified via red, green, and blue imaging analysis. Therefore, the presented CsPbBr3 PQDs/cellulose composite could be used as an effective colorimetric sensor for the real-time monitoring of trace elements such as chlorine and iodine in tap water.

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Here, we report the fabrication of palladium nanoparticles on porous aromatic frameworks (Pd/PAF-6) using a facile chemical approach, which was characterized by various spectro- and electrochemical techniques. The differential pulse voltammetry (DPV) response of Pd/PAF-6 toward the vanillin (VA) sensor shows a linear relationship over concentrations (10-820 pM) and a low detection limit (2 pM). Pd/PAF-6 also exhibited good anti-interference performance toward 2-fold excess of ascorbic acid, nitrophenol, glutathione, glucose, uric acid, dopamine, ascorbic acid, 4-nitrophenol, glutathione, glucose, uric acid, dopamine, and 100-fold excess of Na(+), Mg(2+), and K(+) during the detection of VA. The developed electrochemical sensor based on Pd/PAF-6 had good reproducibility, as well as high selectivity and stability. The established sensor revealed that Pd/PAF-6 could be used to detect VA in biscuit and ice cream samples with satisfactory results.

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