Surface modification of mild steel using 4-carboxyphenyl diazonium in sulfuric and hydrochloric acids. A corrosion study.

In this paper, the surface of mild steel is modified with 4-carboxyphenyl diazonium and subsequently, the corrosion behaviour of the modified surface is scrutinized in hydrochloric and sulfuric acid solutions. The diazonium salt was synthesized in situ either in 0.5 M HCl or 0.25 M H2SO4 through the reaction between 4-aminobenzoic acid and sodium nitrite. The surface of mild steel was modified with the obtained diazonium salt with or without the need for electrochemical assistance. Electrochemical impedance spectroscopy (EIS) measurements show that a spontaneously grafted mild steel surface has a better corrosion inhibition efficiency (86%) in 0.5 M HCl. Scanning electron microscopy reveals that the protective film formed on the surface of mild steel exposed to 0.5 M HCl containing the diazonium salt looks more consistent and uniform compared to the surface exposed to 0.25 M H2SO4. Optimized diazonium structure and the separation energy calculated using density functional theory correlate with the good corrosion inhibition obtained experimentally.

Immobilization of Molecularly Imprinted Polymer Nanoparticles onto Surfaces Using Different Strategies: Evaluating the Influence of the Functionalized Interface on the Performance of a Thermal Assay for the Detection of the Cardiac Biomarker Troponin I.

We demonstrate that a novel functionalized interface, where molecularly imprinted polymer nanoparticles (nanoMIPs) are attached to screen-printed graphite electrodes (SPEs), can be utilized for the thermal detection of the cardiac biomarker troponin I (cTnI). The ultrasensitive detection of the unique protein cTnI can be utilized for the early diagnosis of myocardial infraction (i.e., heart attacks), resulting in considerably lower patient mortality and morbidity. Our developed platform presents an innovative route to develop accurate, low-cost, and disposable sensors for the diagnosis of cardiovascular diseases, specifically myocardial infraction. A reproducible and advantageous solid-phase approach was utilized to synthesize high-affinity nanoMIPs (average size = 71 nm) for cTnI, which served as synthetic receptors in a thermal sensing platform. To assess the performance and commercial potential of the sensor platform, various approaches were used to immobilize nanoMIPs onto thermocouples or SPEs: dip coating, drop casting, and a covalent approach relying on electrografting with an organic coupling reaction. Characterization of the nanoMIP-functionalized surfaces was performed with electrochemical impedance spectroscopy, atomic force microscopy, and scanning electron microscopy. Measurements from an in-house designed thermal setup revealed that covalent functionalization of nanoMIPs onto SPEs led to the most reproducible sensing capabilities. The proof of application was provided by measuring buffered solutions spiked with cTnI, which demonstrated that through monitoring changes in heat transfer at the solid-liquid interface, we can measure concentrations as low as 10 pg L-1, resulting in the most sensitive test of this type. Furthermore, preliminary data are presented for a prototype platform, which can detect cTnI with shorter measurement times and smaller sample volumes. The excellent sensor performance, versatility of the nanoMIPs, and reproducible and low-cost nature of the SPEs demonstrate that this sensor platform technology has a clear commercial route with high potential to contribute to sustainable healthcare.