Direct Electrodeposition of Bimetallic Nanostructures on Co-Based MOFs for Electrochemical Sensing of Hydrogen Peroxide

Hydrogen peroxide (H₂O₂) is the most significant reactive oxygen species in biological systems. Here, we reported an electrochemical sensor for the detection of H₂O₂ on the basis of bimetallic gold-platinum nanoparticles (Au₃Pt₇ NPs) supported by Co-based metal organic frameworks (Co-MOFs). First, Au₃Pt₇ NPs, with optimal electrocatalytic activity and accessible active surface, can be deposited on the surface of the Co-MOF–modified glassy carbon electrodes (Au₃Pt₇/Co-MOFs/GCE) by one-step electrodeposition method. Then, the electrochemical results demonstrated that the two-dimensional (2D) Co-MOF nanosheets as the supporting material displayed better electrocatalytic properties than the 3D Co-MOF crystals for reduction of H₂O₂. The fabricated Au₃Pt₇/2D Co-MOF exhibited high electrocatalytic activity, and the catalytic current was linear with H₂O₂ concentration from 0.1 μM to 5 mM, and 5–60 mM with a low detection limit of 0.02 μM (S/N = 3). The remarkable electroanalytical performance of Au₃Pt₇/2D Co-MOF can be attributed to the synergistic effect of the high dispersion of the Au₃Pt₇ NPs with the marvelous electrochemical properties and the 2D Co-MOF with high-specific surface areas. Furthermore, this sensor has been utilized to detect H₂O₂ concentrations released from the human Hela cells. This work provides a new method for improving the performance of electrochemical sensors by choosing the proper support materials from diverse crystal morphology materials.

One-pot synthesis of Au-based nanocrystals via a platinum group metal anion controlled growth strategy in citrate medium

Finding a facile manufacturing method of Au-based low PGM content nanocrystals by exploring the reaction process of a series of PGM anions with the in situ Au NW templates.

In Situ SERS Monitoring of the Plasmon-Driven Catalytic Reaction by Using Single Ag@Au Nanowires as Substrates

Single nanowires (NWs), as a kind of new surface-enhanced Raman scattering (SERS) substrates, have received extensive concern owing to their distinctive properties and distinct advantages. In this contribution, single Ag nanowires (AgNWs) and single Au-coated AgNWs (Ag@AuNWs) were fabricated by the laser-assisted pulling method and the galvanic replacement reaction, respectively. The prepared single Ag@AuNWs show both high SERS activity and catalytic activity through in situ monitoring and assessing the plasmon-driven surface-catalytic reaction of 4-nitrothiophenol (4-NTP) dimerizing to 4,4'-dimercaptoazobenzene and the reduction reaction of 4-NTP to para-aminothiophenol, respectively. It was found that the intensity of the Raman peak was affected greatly by the laser power, and the Raman peak could still be observed at 0.05% power under mild conditions (633 nm wavelength) in this single nanowire system. From the Raman spectrum, the SERS enhancement factor (EF) of 5.4 × 10⁴ can be obtained, and the EF value of 1.3 × 10⁹ can be reached at optimal conditions. Results have shown that single Ag@AuNWs can be utilized as a good platform for SERS applications with high sensitivity, stability, and reproducibility, which will benefit SERS-based research at the single entity level.

Single gold nanoclusters: Formation and sensing application for isonicotinic acid hydrazide detection

Nano-sized electrodes have their special advantages for sensing applications, such as small overall dimension, fast response and low background current. In this work, single gold nanoclusters (AuNCs) were controllably prepared on single Pt nanoelectrode surface by electrodeposition method. The AuNCs covered Pt nanoelectrode (AuNCs/PtNE) had steady-state voltammetric response in redox species solution, which was similar to micro-/nano-sized electrodes. It was interesting to find isonicotinic acid hydrazide (INH, also known as isoniazid) showed good electrochemical response on AuNCs/PtNE surface, which had investigated carefully by square wave voltammetry (SWV) and chronoamperometry. Moreover, the prepared single AuNCs/PtNEs showed the capability for INH sensing with good sensitivity, reproducibility and selectivity, which was demonstrated for INH detection in human urine samples.

Amperometric sensing of hydrazine by using single gold nanopore electrodes filled with Prussian Blue and coated with polypyrrole and carbon dots

A nanoprobe for hydrazine sensing is described that is making use of a single gold nanopore electrode (SAuNPEs) that was modified by electro-deposition of Prussian Blue (PB) and then coated with a thin membrane of polypyrrole and carbon dots in order to enhance stability and catalytic activity. Best operated at a low potential of 0.3 V vs. Ag/AgCl, the nanosensor display good electrocatalytic activity towards the oxidation of hydrazine, with a linear response in the 0.5-80 μM hydrazine concentration range and a 0.18 μM detection limit (at S/N = 3). The method was applied to the determination of hydrazine in human urine. Graphical abstract Schematic presentation of the electrocatalytic oxidation of hydrazine using a single gold nanopore electrode that was modified by electro-deposition of Prussian Blue and then coated with a thin membrane of polypyrrole and carbon dots.