Nicotinamide Inhibition Properties for Copper Corrosion in 3.5% NaCl Solution: Experimental and Theorical Investigations

This work reports the inhibition properties of nicotinamide (NAM) for copper protection during its applications in seawater systems such as water pipelines, shipbuilding, seawater desalination and heat exchange systems. The efficiency of NAM as a copper corrosion inhibitor in simulated seawater (3.5% NaCl solution) was investigated by Tafel extrapolation and linear polarization methods in the temperature range from 20℃ to 50℃. The corrosion parameters and the adsorption isotherms were determined using potentiodynamic polarization techniques. It was found that the inhibition efficiency (η) and the coverage rate (θ) increase up 80% at 25℃ for nicotinamide concentration of 10 mM but decrease as the temperature of the solution increases. Moreover, the obtained thermodynamic parameters using Langmuir model suggested a physical adsorption type. A correlation was found between the corrosion inhibition efficiency and the global theoretical parameters obtained by the functional density method B3LYP/ 6-31 + G (d, p). Local parameters such as condensed Fukui functions [f(r)] and condensed local softness [s(r)] indices have also been determined to obtain a chemical insight into atoms that have a significant tendency toward donation or acceptance of whole or fraction of electrons.

Nanoscale image of the drug/metal mono-layer interaction:Tapping A FM-IR investigations

The application of metal nanoparticles as an efficient drug delivery system is one of the directions of cancer therapy development.However,this strategy requires precise information about how the drug interacts with the applied nanocarrier.In this study,atomic force microscopy combined with infrared spectroscopy(AFM-IR)was used for the first time to investigate the erlotinib adsorption structure on two different types of 15 nm metal nanoparticle mono-layers,namely,silver nanoparticle(AgNP)and gold nanoparticle(AuNP)mono-layers.Because the metal nanoparticles are loosely bound samples,only the tapping AFM-IR mode is suitable for the collection of IR maps and spectra for such a system.The obtained results indicated the relevance of the AFM-IR technique for characterizing drug interactions with a metal mono-layer surface.The investigated drug interacts with the AgNPs mainly through phenyl rings and methoxy moieties,while quinazoline,amino,and ethoxy moieties appear to be farther from the surface.For the AuNPs,the interaction occurs through both the phenyl ring and the quinazoline moiety.Additionally,the aliphatic groups of erlotinib directly participate in this interaction.The novelty of the present work is also related to the use of the tapping AFM-IR mode to study metal NP mono-layers with a drug adsorbed on them.The collected IR maps for the most enhanced erlotinib bands show specific areas with very high signal intensity.The connection between these areas and the"hot spots"typical for the surface plasmon resonance phenomenon of metals is considered.