A stable interface based on aryl diazonium salts/SWNTs modified gold electrodes for sensitive detection of hydrogen peroxide

Tailoring the performance of electrochemical biosensors based on carbon nanomaterials via aryldiazonium electrografting

Carbon nanomaterials (CNs) offer some of the most valuable properties for electrochemical biosensing applications, such as good electrical conductivity, wide electrochemical stability, high specific surface area, and biocompatibility. Regardless the envisioned sensing application, endowing CNs with specific functions through controlled chemical functionalization is fundamental for promoting the specific binding of the analyte. As a versatile and straightforward method of surface functionalization, aryldiazonium chemistry have been successfully used to accommodate in a stable and reproducible way different functionalities, while the electrochemical route has become the favourite choice since the deposition conditions can be readily controlled and adapted to the substrate. In particular, the modification of CNs by electrochemical reduction of aryl diazonium salts is established as a powerful tool which allows tailoring the chemical and electronic properties of the sensing platform. By outlining the stimulating results disclosed in the last years, this article provides not only a comprehensively review, but also a rational assessment on contribution of aryldiazonium electrografting in developing CNs-based electrochemical biosensors. Furthermore, some of the emerging challenges to be surpassed to effectively implement this methodology for in vivo and point of care analysis are also highlighted.

Exonuclease-assisted target recycling for ultrasensitive electrochemical detection of microRNA at vertically aligned carbon nanotubes

As an important biomarker for early disease diagnosis, microRNA-21 (miRNA-21) has attracted considerable attention owing to its accurate detection. Herein we combine the one-step biorecognition reaction at a vertically aligned nanostructure-based biosensor with the T7 exonuclease (Exo)-assisted target recycling to develop a novel electrochemical bioassay method for miRNA-21 detection. The vertically aligned nanointerface is constructed through the covalent attachment of terminally carboxylated single-walled carbon nanotubes (SWCNTs) at an aryldiazonium salt-modified electrode, which enables the noncovalent adsorption of a ferrocene-labeled single-stranded signal DNA to obtain the biosensor. Upon its incubation with a target miRNA-21 solution, DNA/RNA hybridized duplexes will form and release from the electrode surface, leading to the corresponding electrochemical signal decrease of the biosensor. Moreover, this biorecognition reaction can also trigger the T7 Exo-assisted target recycling to achieve great signal amplification. Together with the highly efficient biorecognition and excellent electron transfer promotion at the vertically aligned SWCNTs, this biosensor exhibits a wide linear range varying from 0.01 to 100 pM and a low detection limit down to 3.5 fM. Considering its obvious performance superiority and convenient manipulations, this vertically aligned SWCNT-based electrochemical biosensing method has extensive potential for practical applications.

Facile synthesis of 3D N-doped porous carbon nanosheets as highly active electrocatalysts toward the reduction of hydrogen peroxide

Constructing three-dimensional (3D) conductive frameworks with high specific surface areas and porous structures is indispensable for their applications as electrocatalysts. In this work, we illustrate for the first time that 3D N-doped porous carbon nanosheets (3D-NS), which are synthesized via a facile one-pot pyrolysis reaction using glucose and melamine as raw materials, can serve as high performance and green electrocatalysts for the reduction of H2O2. Moreover, a series of 3D-NS samples with a controllable content of nitrogen were obtained by adjusting the calcination temperature. From our research, the 3D-NS obtained at 900 °C possessed high specific surface areas, porous structures, proper dosages of N atoms, suitable degrees of graphitization and defects. Furthermore, we also illustrate their application in H2O2 electrochemical sensing in physiological environments. Under optimum conditions, the 3D-NS-based sensor displays a wide linear scope in the range of 0.5-14 000 μM and a low detection limit of 0.18 μM (S/N = 3). Therefore, with desirable selectivity, stability and anti-interference performance, the proposed sensor can be feasibly applied to detect H2O2 in human serum samples.

Advances on Aryldiazonium Salt Chemistry Based Interfacial Fabrication for Sensing Applications

Aryldiazonium salts as coupling agents for surface chemistry have evidenced their wide applications for the development of sensors. Combined with advances in nanomaterials, current trends in sensor science and a variety of particular advantages of aryldiazonium salt chemistry in sensing have driven the aryldiazonium salt-based sensing strategies to grow at an astonishing pace. This review focuses on the advances in the use of aryldiazonium salts for modifying interfaces in sensors and biosensors during the past decade. It will first summarize the current methods for modification of interfaces with aryldiazonium salts, and then discuss the sensing applications of aryldiazonium salts modified on different transducers (bulky solid electrodes, nanomaterials modified bulky solid electrodes, and nanoparticles). Finally, the challenges and perspectives that aryldiazonium salt chemistry is facing in sensing applications are critically discussed.