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Hydrogen peroxide (H 2 O 2) is a common oxidant that plays an important role in many biological processes and is also an important medium analysis in various fields. In this work, a new electrochemical nanosensor capable of detecting and quantifying hydrogen peroxide was introduced. This nanosensor was fabricated by electrodepositing prussian blue (PB)/graphene quantum dots (GQDs)/polypyrrole (PPy) on single nanopore electrode etched from single gold nanoelectrode. This prepapred nanosensor exhibits good electrochemical response to hydrogen peroxide with high sensitivity and stability, with a linear response in the 2.0 and 80 μM by using amperometric method and differential pulse voltammetry (DPV) method. The limit of detections are 0.33 μM (S/N = 3) for amperometric method and 0.67 μM (S/N = 3) for differential pulse voltammetry (DPV) method, respectively. This nanosensor can be used for the determination of hydrogen peroxide in human urine, and can serve as a new electrochemical platform to monitor H 2 O 2 release from single living cells due to its small overal dimension and high sensitivity. [Display omitted] • Nanosensor was fabricated on single nanopore electrode filled with Prussian blue and graphene quantum dots coated by Polypyrrole. • New nanosensor shows good electrocatalytic activity towards H2O2 oxidation. • This nanosensor can serve as a new electrochemical platform to monitor H2O2 release from single living cells due to its small overal dimension. [ABSTRACT FROM AUTHOR]

A new nanozyme (CuGaa) with switchable enzyme-like activity of peroxidase and polyphenol oxidase was successfully prepared based on guanidinoacetic acid and copper. The two enzyme-like activities can be easily switched by changing temperature or adding MnCl 2. At 4 °C, polyphenol oxidase-like activity decreased to nearly 1%, and the material is mainly characterized by peroxidase-like activity at this point. However, at 60 °C in the presence of 20 mM MnCl 2 , the peroxidase-like activity decreased to nearly 10%, and the polyphenol oxidase-like activity of the materials increased to 140%. Based on the switchable enzyme-like activity of CuGaa, detection methods for thymol and hydrogen peroxide were developed. In addition, a rapid combination strategy was further established combined with logic gate technology for the facile identification of complex contamination in honey, which provided new ideas for low-cost and rapid honey identification. The graphic descriptives that CuGaa has polyphenol oxidase-like and peroxidase-like activities, and that under different conditions, CuGaa can be made to exhibit only one enzyme activity. [Display omitted] • Nanozyme with switchable enzyme-like activity. • Thymol detection at high temperature based on the nanozyme. • A sensing strategy combined with logic gate technology. • A facile identification of complex contamination in honey. [ABSTRACT FROM AUTHOR]

Abstract: Based on the enhancement of chemiluminescence (CL) of luminol-hydrogen peroxide-gold nanoparticles system by fluoroquinolones (FQs), a novel and rapid CL method is reported for the determination of FQs derivatives. Under the optimum conditions, the CL intensity is proportional to the concentration of FQs derivative in solution. The corresponding linear regression equations are established over the range of 0.08–1.28μg/mL for norfloxacin, 0.013–1.32μg/mL for ciprofloxacin, 0.014–1.4μg/mL for lomefloxacin, 0.029–1.46μg/mL for fleroxacin, 0.02–1.0μg/mL for ofloxacin and 0.01–1.44μg/mL for levofloxacin, respectively. The limits of detection (S/N =3) are 3.2, 9.5, 7.0, 9.0, 8.0, and 8.0ng/mL with the relative standard deviation (n =11) 4.3, 1.5, 1.9, 1.3, 1.6 and 2.1% for norfloxacin, ciprofloxacin, lomefloxacin, fleroxacin, ofloxacin and levofloxacin, respectively. This proposed method has been applied to detect FQs derivatives in human urine successfully. [Copyright &y& Elsevier]

Solid-nanopores/nanopipettes have the exquisite ability to reveal the changes in molecular volume due to the advantages of adjustable size, good rigidity and low noise. Herein, a new platform for sensing application was established based on G-quadruplex-hemin DNAzyme (GQH) functionalized gold-coated nanopipettes. In this method, GQH was immobilized on gold-coated nanopipette, which could be used as a catalyst for the reaction of H 2 O 2 with 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) to promote the conversion of ABTS to ABTS+ ions inside gold-coated nanopipette, and the change of transmembrane ion current could be monitored in real time. At the optimal conditions, there was a correlation between the ion current and the concentration of H 2 O 2 in a certain range, which could be used for the hydrogen peroxide sensing. The GQH immobilized nanopipette provides a useful platform to investigate enzymatic catalysis in confined environment, which can be used in electrocatalysis, sensing and fundamental electrochemistry. [Display omitted] • GQH-functionalized gold-coated nanopipettes was fabricated successfully. • GQH-functionalized nanopipettes was used as a catalyst for H 2 O 2 and ABTS reaction. • The conversion of ABTS to ABTS + ions resulted the change of ICR. • A H 2 O 2 sensor was established using the GQH-functionalized nanopipettes platform. [ABSTRACT FROM AUTHOR]