Nanocatalysis MoS2/rGO: An Efficient Electrocatalyst for the Hydrogen Evolution Reaction.

In this study, a systematic investigation of MoS2 nanostructure growth on a SiO2 substrate was conducted using a two-stage process. Initially, a thin layer of Mo was grown through sputtering, followed by a sulfurization process employing the CVD technique. This two-stage process enables the control of diverse nanostructure formations of both MoS2 and MoO3 on SiO2 substrates, as well as the formation of bulk-like grain structures. Subsequently, the addition of reduced graphene oxide (rGO) was examined, resulting in MoS2/rGO(n), where graphene is uniformly deposited on the surface, exposing a higher number of active sites at the edges and consequently enhancing electroactivity in the HER. The influence of the synthesis time on the treated MoS2 and also MoS2/rGO(n) samples is evident in their excellent electrocatalytic performance with a low overpotential.

Ligand influence in electrocatalytic properties of Cu(II) triazole complexes for hydrogen peroxide detection in aqueous media.

In this work, electrocatalytic changes of Cu(II) triazole complexes (Cu(L)2) resulting from inductive effects were evaluated to fabricate a sensor for hydrogen peroxide (H2O2) determination. Three copper(II) complexes with electronically differentiated ligands were synthesized by slow diffusion method and characterized by X-ray crystallography, Fourier transformed infrared (FTIR), UV-Vis, scanning electron microscopy (SEM) and voltammetry cyclic (CV). Cu(LOMe)2/GC, Cu(LBr)2/GC and Cu(LNO2)2/GC sensors were then prepared. Under optimal conditions (pH = 11), the optimal sensor presented a response at -0.5 V, good linear range of 1-32 µM, reproducibility (1.7%), repeatability (1.2%), LOD of 0.0246 µM (S/N = 5), LOQ of 0.0747 µM (S/N = 5) and selectivity. Additionally, Cu(LNO2)2/GC sensor has been successfully applied in commercial substances, such as mouthwash, milk and tea.

Electrochemical dopamine sensor using a nanoporous gold microelectrode: a proof-of-concept study for the detection of dopamine release by scanning electrochemical microscopy.

Nanoporous gold (NPG) structures were prepared on the surface of a gold microelectrode (Au-µE) by an anodization-reduction method. Cyclic voltammetry and field emission scanning electron microscopy were used to study the electrochemical properties and the morphology of the nanostructured film. Voltammetry showed an improved sensitivity for dopamine (DA) oxidation at this microelectrode when compared to a bare gold microelectrode, with a peak near 0.2 V (vs. Ag/AgCl) at a scan rate of 0.1 V s-1. This is due to the increased surface area and roughness. Square wave voltammetry shows a response that is linear in the 0.1-10 µmol L-1 DA concentration range, with a 30 nmol L-1 detection limit and a sensitivity of 1.18 mA (µmol L-1)-1 cm-2. The sensor is not interfered by ascorbic acid. The reproducibility, repeatability, long-term stability and real sample analysis (spiked urine) were assessed, and acceptable performance was achieved. The "proof-of-concept" detection of dopamine release was demonstrated by using scanning electrochemical microscopy (SECM) with the aim of future applications for single cell analysis. Graphical abstract A reproducible electrochemical approach was proposed to fabricate an NPG-microelectrode for DA detection, with enhanced sensitivity and selectivity. Besides, a proof-of-concept detection of DA release was also demonstrated by using SECM.