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This review discusses various sol–gel coatings for the corrosion protection of Cu. It is used in various industries, including automotive, electronics, oil/gas, and thermal–power plants, owing to its electrical/thermal conductivity, and mechanical ductility. However, Cu undergoes severe corrosion in aggressive chloride environments, causing considerable industrial losses. Sol–gel coatings for Cu metal protection are a preferred to other types of metallic coatings, because they are cost effectiveness, simple preparation methodology and eco-friendly. Sol–gel coatings compromise a produce an adhesive and compact layer that adheres to the metal surface and acts as a barrier, preventing the diffusion of aggressive Cl ions into the Cu metal and impeding corrosion. The synthesis, morphological studies, and corrosion protection methods of some advanced sol–gel based hybrid protective coatings are discussed in this review. Furthermore, the corrosion protection ability of these sol–gel coatings and their future development prospects are addressed. Highlights: Sol–gel coatings is a very effective method for Cu protection especially in aggressive corrosive media. Sol–gel coatings generate an adhesive layer and acted as a barrier between the Cu and corrosive species. Sol–gel coatings possess several mode of synthesis accordingly with the metal specimen and its surroundings. Sol–gel coatings exhibit an exceptional corrosion inhibitive potential that has been well proven via standard corrosion measurement techniques. [ABSTRACT FROM AUTHOR]

Aluminum metal and its alloys are most precious metals in industries, marine, and aircraft applications due to its interesting properties. However, aluminum metal undergoes corrosion in presence of aggressive chloride environments. Sol-gel based protective coating is mainly used to safeguard aluminum metal from corrosive chloride environments. In the present work, inorganic and polymeric composite corrosion inhibitors were synthesized for Al protection in aqueous 3.5% NaCl media (Zr and chitosan were hybridized using silanes). Surface morphology and chemical composition were duly characterized via FTIR and SEM-EDX, while corrosion resistivity was investigated by impedance (EIS) and polarization studies (PDS). Further, molecular modeling studies were performed to understand the corrosion inhibition mechanism and reveal those factors influences the corrosion efficiency of the chitosan-doped hybrid corrosion inhibitors.Chitosan-doped Hy/Zrnanocomposite sol-gel coating shown higher corrosion resistance of 96.1% than a hybrid (Hy) and Hy/Zr sol-gel coating. PDS showed that the chitosan-doped Hy/Zr sol-gel coating protects the Al metal by an anodic dissolution process. Computational chemistry and molecular dynamics study further evident the chitosan-doped Hy/Zr sol-gel coating enhanced the corrosion resistance of the Al substrates by lowering the molecular orbital gap energy and enhancing the adsorption of the corrosion inhibitors. Highlights: A new carbohydrate polymer, Chitosan is doped with Hy/Zrbio-nanocomposite sol–gel based coating over Al metal. Chitosan doped-Hy/Zr nanocomposite sol–gel coating is successfully fabricated and analyzed. The maximum protection efficiency of Chitosan doped-Hy/Zr nanocomposite sol–gel coating is 96.14%. DFT and MDs values are accordance with inhibition efficiency of modified Al metal. [ABSTRACT FROM AUTHOR]

An efficient, simple, robust strategy for the protection of copper in a neutral medium has been developed by the fabrication of electropolymerised film of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) + TiO2 composite. The electrosynthesised polymeric and composite films were characterised by different spectroscopic methods (FTIR, Raman spectroscopy, XPS, and XRD pattern). Electrochemical impedance spectroscopy and potentiodynamic polarisation studies confirmed the superior corrosion inhibition performance of fabricated composite film on copper in 3.5% NaCl medium. The enhanced protection efficiency of the polymeric composite could be due to the synergism between the organic polymer and inorganic particles. It is also found that the protection efficiency of the DMTD–TiO2 composite film lasts for more than 24 h. Further, SEM analysis reveals the formation of the protective film of the composite over Cu surface, while EDAX analysis unravels its composition. The study on effect of scan rate on electropolymerisation revealed that the electrodeposition of the polymer is a diffusion-controlled process. Thus, the study suggests that the fabrication of DMTD–TiO2 composite is an ideal strategy for the protection of copper in a neutral medium. [ABSTRACT FROM AUTHOR]

In the present work, 4-aminothiophenol was impregnated into hybrid sol-gel consisting of 3-glycidoxypropyltrimethoxysilane and tetraethoxysilane at acidic, neutral and basic pH, which were subsequently self-assembled over copper surface. The resultant hybrid sol-gel layers were ascertained using Fourier transform infrared and UV-visible spectroscopic techniques. The surface morphology, chemical composition and wettability were studied using scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy and water contact angle analyses, respectively. The corrosion inhibitive behavior of the as-prepared layers was studied using electrochemical impedance spectroscopy and potentiodynamic polarization studies. These studies revealed that among the three pH regions examined, the maximum inhibition efficiency was achieved only at acidic pH. Graphical Abstract: By appropriately tuning the pH of 4-aminothiophenol-impregnated hybrid sol-gel endures better copper corrosion protection.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this work, 3-amino-5-mercapto-1,2,4-triazole (AMTa) was incorporated into 3-glycidoxypropyltrimethoxysilane (GPTMS)-based sol-gel coatings, which were self-assembled over a copper surface. The AMTa-doped GPTMS-based sol-gel coatings were characterized by Fourier transform infrared spectroscopy, Scanning Electron Microscopy, and Energy-Dispersive X-ray spectroscopy analyses. The protective ability of these coatings was evaluated by electrochemical impedance studies and potentiodynamic polarization measurements in 3.5 % NaCl medium. The AMTa-doped sol-gel coating showed enhanced corrosion protection ability compared to the un-doped GPTMS-based sol-gel coating, which may be largely due to the formation of thiolate bonds between copper and AMTa. The presence of a silane network through the amine group of AMTa could also be a reason for the enhanced protection. [ABSTRACT FROM AUTHOR]

Electropolymerization of 3-amino-5-mercapto-1,2,4-triazole (AMTA) on copper was carried out in methanol/NaOH solution by cyclic voltammetry. Chronoamperometry technique was used to investigate the formation kinetics of the polymer film. The effect of scan rate was also studied. Electropolymerized film of AMTA was duly characterized by Fourier transform infrared spectroscopy. Scanning electron microscopy was used to analyze the surface morphology of the polymer film. The protective ability of poly-3-amino-5-mercapto-1,2,4-triazole (p-AMTA) film was determined by electrochemical impedance spectroscopy and potentiodynamic polarization studies in NaCl medium. The results of the study showed that the p-AMTA film on copper afforded significant corrosion protection in neutral medium. Quantum theoretical studies revealed the adsorptive behavior of AMTA on copper. [ABSTRACT FROM AUTHOR]

The present work involves the incorporation of dopamine (DA) into the hybrid sol-gel monolayers (Hy) consisting of (3-glycidoxypropyl)methyldiethoxysilane and Tetraethyl orthosilicate. The resultant doped hybrid layers coated over aluminum surface was characterized by FT-IR, UV-Vis, XRD, EDX and SEM analyses. The corrosion behavior of bare and coated aluminum substrates in 3.5 % NaCl medium was examined by cyclic voltammetry, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. Results from the electrochemical measurements showed that the DA impregnated Hy sol-gel monolayers offered better corrosion protection with superior coating thickness than the Hy sol-gel monolayers without DA. The enhancement of protection could be attributed to the fact that DA promote the formation of strongly bonded and densely packed monolayer films, which show better adhesion than the conventional silane systems. [ABSTRACT FROM AUTHOR]

The corrosion inhibitive and adsorption behaviors of Hydroclathrus clathratus on mild steel in 1 M HCl and 1 M HSO solutions at 303, 313 and 323 K were investigated by weight loss, electrochemical, and surface analysis techniques. The results show that H. clathratus acts as an inhibitor of corrosion of mild steel in acid media. The inhibition efficiency was found to increase with increase in inhibitor concentration but to decrease with rise in temperature, suggestive of physical adsorption. The adsorption of the inhibitor onto the mild steel surface was found to follow the Temkin adsorption isotherm. The inhibition mechanism was further corroborated by the results obtained from electrochemical methods. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses supported the inhibitive action of the alga against acid corrosion of mild steel. [ABSTRACT FROM AUTHOR]

The corrosion inhibition of mild steel in 1 M hydrochloric acid by a few piperidin-4-one oxime derivatives, namely, 1,3-dimethyl-2,6-diphenyl piperidin-4-one oxime ( I), 3,3-dimethyl-2,6-diphenyl piperidin-4-one oxime ( II), and 3-isopropyl-2,6-diphenyl piperidin-4-one oxime ( III) was studied using chemical weight loss method, electrochemical polarization and impedance spectroscopy, SEM with EDS, XRD, FT-IR measurements, and semi-empirical AM1 method for electronic properties. The weight loss measurements at four different temperatures such as 30, 40, 50, and 60 °C showed that the percentage inhibition efficiency (IE) of these compounds increased with increase of concentration and decreased with increase of temperature. The IE followed the order III < II < I. It was found that these inhibitors function through physical adsorption mechanism obeying Temkin's isotherm. Polarization studies showed that these compounds act as mixed-type inhibitors. Impedance measurements revealed the increase of charge transfer resistance with inhibitor concentration. Surface analysis using SEM, XRD, and FT-IR revealed the formation of protective film over the mild steel surface. The electronic properties calculated using AM1 semi-empirical method explained the inhibition characteristics. The quantum chemical studies showed that ring nitrogen and phenyl rings are the probable active centers to inhibit corrosion process. [ABSTRACT FROM AUTHOR]

Alkaloid extract of Rauvolfia serpentina was tested as corrosion inhibitor for mild steel in 1 M HCl and H2SO4 using weight loss method at three different temperatures, viz., 303, 313, and 323 K, potentiodynamic polarization, electrochemical impedance spectroscopy and scanning electron microscope (SEM) studies. It is evident from the results of this study that R. serpentina effectively inhibits the corrosion in both the acids through adsorption process following Tempkin adsorption isotherm. The protection efficiency increased with increase in inhibitor concentration and temperature. Free energy of adsorption calculated from the temperature studies also revealed the chemisorption. The mixed mode of action exhibited by the inhibitor was confirmed by the polarization studies while SEM analysis substantiated the formation of protective layer over the mild steel surface. [ABSTRACT FROM AUTHOR]

Uncuffed endotracheal tubes are commonly used in children in an attempt to decrease the potential for pressure induced tracheal injury. However, uncuffed endotracheal tube may increase the risk of aspiration and lead to erratic delivery of preset tidal volume during mechanical ventilation. Therefore, it is desirable to intubate trachea with an appropriate but not an oversized endotracheal tube. In children, for selecting an endotracheal tube, a variety of formulas and techniques are used to find the endotracheal tube size that minimizes both pressure induced tracheal injury and aspiration potential or variable ventilation. Air-leak following tracheal intubation can be recognized by the presence of audible leak, by auscultation over the trachea, by palpation over the trachea and by observing effects of positive end-expiratory pressure on inspiratory expiratory tidal volume difference during mechanical ventilation. We describe mainstream time-capnograph as an aid to recognize leak around the endotracheal tube and its utility to determine appropriate endotracheal tube size in small children. [ABSTRACT FROM AUTHOR]

This research introduces a novel fluorescence sensor ‘on-off-on’ employing nitrogen-doped carbon dots (N-CDs) with an ‘on-off-on’ mechanism for the selective and sensitive detection of Hg(II) and L-cysteine (L-Cys). N-CDs was synthesized using citric acid as the carbon precursor and urea as the nitrogen source in dimethylformamide (DMF) solvent, resulting in red emissive characteristics under UV light. Comprehensive spectroscopic analyses, including UV-Vis, fluorescence, FT-IR, XRD, XPS, Raman, and Zeta potential techniques, validated the structural and optical characteristics of the synthesized N-CDs. The maximum excitation and emission of N-CDs were observed at 548 and 622 nm, respectively. The quantum yield of N-CDs was calculated to be 16.1%. The fluorescence of N-CDs effectively quenches upon the addition of Hg(II) due to the strong coordination between Hg(II) and the surface functionalities of N-CDs. Conversely, upon the subsequent addition of L-Cys, the fluorescence of N-CDs was restored. This restoration can be attributed to the stronger affinity of the -SH group in L-Cys towards Hg(II) relative to the surface functionalities of N-CDs. This dual-mode response enabled the detection of Hg(II) and L-Cys with impressive detection limits of 15.1 nM and 8.0 nM, respectively. This sensor methodology effectively detects Hg(II) in lake water samples and L-Cys levels in human urine, with a recovery range between 99 and 101%. Furthermore, the N-CDs demonstrated excellent stability, high sensitivity, and selectivity, making them a promising fluorescence on-off-on probe for both environmental monitoring of Hg(II) and clinical diagnostics of L-Cys. [ABSTRACT FROM AUTHOR]

Bilirubin plays a significant role in human health management, particularly in the case of jaundice. Because of the need for the monitoring of bilirubin levels in jaundice patients, the development of a robust sensitive method becomes essential. Here, we describe the development of a highly sensitive and selective turn-off fluorometric detection method for bilirubin in blood serum samples using nitrogen-doped carbon dots (N-CDs). N-CDs was synthesized by the pyrolysis process, using citric acid and L-asparagine as the carbon and nitrogen sources, respectively. The prepared N-CDs solution showed highly intense blue emission with good stability. The HR-TEM image of N-CDs revealed spherical dot-like structures with an average size calculated to be 7.16 nm. Further, the surface functional groups of N-CDs were analyzed by FT-IR, Raman, XRD, and XPS techniques. Fluorescence spectra showed the maximum emission intensity at 443 nm (λex). The linear range of addition was performed from 1 to 150 µM, and the limit of detection (LOD) was determined to be 1.97 nM. The emission of N-CDs was quenched by Förster Resonance Energy Transfer (FRET) by adding bilirubin. These N-CDs showed extraordinary sensitivity and selectivity in the detection of bilirubin. Hence, this fluorescent probe has been proven successful in detecting the concentration of free bilirubin in human serum samples. [ABSTRACT FROM AUTHOR]