A comparative electrochemical study of electrosorbed 2- and 4-mercaptopyridines and their application as corrosion inhibitors at C60 steel

An Electrochemical Screen-Printed Sensor Based on Gold-Nanoparticle-Decorated Reduced Graphene Oxide-Carbon Nanotubes Composites for the Determination of 17-β Estradiol

In this study, a screen-printed electrode (SPE) modified with gold-nanoparticle-decorated reduced graphene oxide-carbon nanotubes (rGO-AuNPs/CNT/SPE) was used for the determination of estradiol (E2). The AuNPs were produced through an eco-friendly method utilising plant extract, eliminating the need for severe chemicals, and remove the requirements of sophisticated fabrication methods and tedious procedures. In addition, rGO-AuNP serves as a dispersant for the CNT to improve the dispersion stability of CNTs. The composite material, rGO-AuNPs/CNT, underwent characterisation through scanning electron microscopy (SEM), ultraviolet-visible absorption spectroscopy (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). The electrochemical performance of the modified SPE for estradiol oxidation was characterised using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The rGO-AuNPs/CNT/SPE exhibited a notable improvement compared to bare/SPE and GO-CNT/SPE, as evidenced by the relative peak currents. Additionally, we employed a baseline correction algorithm to accurately adjust the sensor response while eliminating extraneous background components that are typically present in voltammetric experiments. The optimised estradiol sensor offers linear sensitivity from 0.05-1.00 µM, with a detection limit of 3 nM based on three times the standard deviation (3δ). Notably, this sensing approach yields stable, repeatable, and reproducible outcomes. Assessment of drinking water samples indicated an average recovery rate of 97.5% for samples enriched with E2 at concentrations as low as 0.5 µM%, accompanied by only a modest coefficient of variation (%CV) value of 2.7%.

Corrosion Inhibition Effect of Pyridine-2-Thiol for Brass in An Acidic Environment

In this study, the inhibitive performance of pyridine-2-thiol added to a corrosive solution was investigated for brass using potentiodynamic polarization, electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy. Electrochemical experiments were performed with different inhibitor concentrations in 0.5 M H₂SO₄ as the corrosive medium. For potentiodynamic polarization, i_corr values decreased significantly for the inhibited solutions in contrast with the uninhibited solution. Pyridine-2-thiol had an optimum inhibition concentration of 0.25 mM, giving an i_corr value of 1.8 µA/cm² compared to 26 µA/cm² for the blank solution. EIS data indicated that R_p and R_ct values increased substantially after the addition of the corrosion inhibitor and corrosion inhibition efficiencies of more than 85% was achieved for the majority of the inhibited solutions. Scanning electron microscopy showed defect free and less scale formation for the inhibited surface but the bare brass surface had larger amounts of scale formation. X-ray photoelectron spectroscopy and UV-vis spectroscopy was used to investigate surface chemical composition and inhibitor structural changes over time.

Biocorrosion of mild steel and copper used in cooling tower water and its control

The present study describes the biocorrosion of mild steel (MS1010) and pure copper (Cu) in cooling water environments (both field and lab study). Electrochemical and surface analyses of both metals were carried out to confirm the corrosion susceptibility in the presence of bacteria and inhibitor. Surface analysis of the MS and Cu coupons revealed that biofilm was developed with increasing exposure time in the field study. In the lab study, accumulation of extracellular polymeric substance over the metal surface was noticed and led to the severe pitting type of corrosion on both metal surfaces. Besides, the anti-corrosive study was carried out using the combinations of commercial corrosion inhibitor (S7653-10 ppm) with biocide (F5100-5 ppm), and the results reveal that the corrosion rate of MS and Cu was highly reduced to 0.0281 and 0.0021 mm/year (inhibitor system) than 0.1589 and 0.0177 mm/year (control system). Inhibition efficiency for both metals in the presence of inhibitor with biocide was found as 82 and 88% for MS and Cu, respectively. The present study concluded that MS was very susceptible to biocorrosion, compared to copper metal in cooling water environment. Further, the combination of the both inhibitor and biocide was effectively inhibiting the biocorrosion which was due to its antibacterial and anti-corrosive properties.

C60-decorated CdS/TiO2 mesoporous architectures with enhanced photostability and photocatalytic activity for H2 evolution

Fullerene (C60) enhanced mesoporous CdS/TiO2 architectures were fabricated by an evaporation induced self-assembly route together with an ion-exchanged method. C60 clusters were incorporated into the pore wall of mesoporous CdS/TiO2 with the formation of C60 enhanced CdS/TiO2 hybrid architectures, for achieving the enhanced photostability and photocatalytic activity in H2 evolution under visible-light irradiation. Such greatly enhanced photocatalytic performance and photostability could be due to the strong combination and heterojunctions between C60 and CdS/TiO2. The as-formed C60 cluster protection layers in the CdS/TiO2 framework not only improve the light absorption capability, but also greatly accelerated the photogenerated electron transfer to C60 clusters for H2 evolution.

Tip-enhanced Raman spectroscopic imaging of patterned thiol monolayers

Full spectroscopic imaging by means of tip-enhanced Raman spectroscopy (TERS) was used to measure the distribution of two isomeric thiols (2-mercaptopyridine (2-PySH) and 4-mercaptopyridine (4-PySH)) in a self-assembled monolayer (SAM) on a gold surface. From a patterned sample created by microcontact printing, an image with full spectral information in every pixel was acquired. The spectroscopic data is in good agreement with the expected molecular distribution on the sample surface due to the microcontact printing process. Using specific marker bands at 1000 cm(-1) for 2-PySH and 1100 cm(-1) for 4-PySH, both isomers could be localized on the surface and semi-quantitative information was deduced from the band intensities. Even though nanometer size resolution information was not required, the large signal enhancement of TERS was employed here to detect a monolayer coverage of weakly scattering analytes that were not detectable with normal Raman spectroscopy, emphasizing the usefulness of TERS.

Adsorption and inhibitive properties of a Schiff base for the corrosion control of carbon steel in saline water

A Schiff base, namely N-(2-hydroxybenzylidene) thiosemicarbazide (HBTC), was investigated as inhibitor for carbon steel in saline water (SW) using electrochemical measurements such as: potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The morphology of the surfaces before and after corrosion was examined by Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDS). The results showed that HBTC acts as corrosion inhibitor in SW by suppressing simultaneously the cathodic and anodic processes via adsorption on the surface which followed the Langmuir adsorption isotherm; the polarization resistance (R(p)) and inhibition efficiency (IE) increased with each HBTC concentration increase. SEM/EDS analysis showed at this stage that the main product of corrosion is a non-stoichiometric amorphous Fe(3+) oxyhydroxide, consisting of a mixture of Fe(3+) oxyhydroxides, α-FeOOH and/or γ-FeOOH, α-FeOOH/γ-FeOOH and Fe(OH)(3).