The efficiency of 1-hexylpyridinium bromide (NR3) ionic liquid for the corrosion inhibition of carbon steel in 1 M hydrochloric acid has been investigated by gravimetric, linear polarization (LPR), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques. Increasing NR3 concentration led to increasing inhibition efficiency (IE%) following the increasing surface coverage (θ). Thermodynamic studies revealed a decreasing IE% with increasing temperature proven to be due to the physical nature of the adsorption mechanism of NR3 which was shown to obey a Langmuir isotherm. LPR elucidated the mixed type inhibition effect of NR3 and its effective blocking of both cathodic and anodic corrosion sites on the carbon steel surface leading to decreased current densities of both Tafel branches without altering the corrosion mechanism. EIS results confirmed the adsorptive behavior of the investigated ionic liquid in replacement of the initially adsorbed water molecules and the formation of a protective film leading to increasing charge-transfer resistance as a result of decreasing double layer capacitance with increasing concentrations. The IE% attained ca. 88.6% in the presence of as low as 3 × 10⁻³ M NR3 inferring the high inhibitory effect of the studied compound. SEM micrographs confirmed the formation and growth of a protective layer reaching a dense coverage at the optimum concentration.

A highly selective and sensitive dopamine electrochemical sensor based on nitrogen-doped graphene quantum dots–chitosan nanocomposite-modified nanostructured screen printed carbon electrode is presented, for the first time. Graphene quantum dots were prepared via microwave-assisted hydrothermal reaction of glucose, and nitrogen doping was realized by introducing ammonia in the reaction mixture. Chitosan incorporation played a significant role towards the selectivity of the prepared sensor by hindering the ascorbic acid interference and enlarging the peak potential separation between dopamine and uric acid. The proposed sensor's performance was shown to be superior to several recently reported investigations. The as-prepared CS/N,GQDs@SPCE exhibited a high sensitivity (i.e. ca. 418 µA mM cm⁻²), a wide linear range i.e. (1–100 µM) and (100–200 µM) with excellent correlations (i.e.R² = 0.999 andR² = 1.000, respectively) and very low limit of detection (LOD = 0.145 µM) and limit of quantification (LOQ = 0.482 µM) based onS/N = 3 and 10, respectively. The applicability of the prepared sensor for real sample analysis was tested by the determination of dopamine in human urine in pH 7.0 PBS showing an approximately 100% recovery with RSD < 2% inferring both the practicability and reliability of CS/N,GQDs@SPCE. The proposed sensor is endowed with high reproducibility (i.e. RSD = ca. 3.61%), excellent repeatability (i.e. ca. 0.91% current change) and a long-term stability (i.e. ca. 94.5% retained activity).

A melanin-like nanoparticle modified screen-printed electrode for enzyme-less detection of ascorbic acid.