Capsella bursa-pastoris extract as an eco-friendly inhibitor on the corrosion of Q235 carbon steels in 1 mol·L^(-1) hydrochloric acid

The corrosion inhibition effect of Capsella bursa-pastoris extracts(CBE) for Q235 carbon steels in 1 mol·L-1hydrochloric acid solution was studied using electrochemical methods, environmental scanning electron microscopy(SEM) and Raman microscopy analysis. The polarization plots indicate that CBE serves as an effective, mixedtype inhibitor. Linear polarization resistance shows that increasing CBE concentration and temperature results in increased inhibition ef ficiency. The highest inhibition ef ficiency can reach 97% when adding 60 mg·L-1CBE,which is better than some reported plant extracts under the similar environment. The adsorption of CBE molecules is found to obey the Langmuir adsorption isotherm. Some thermodynamic and kinetic parameters for the adsorption process, such as the adsorption equilibrium constant(K), free energy of adsorption(ΔG ads), activation energy of corrosion reaction(E a) and the heat of adsorption(Q ads), are calculated and discussed. SEM and Raman microscopy analysis also demonstrate the formation of a CBE inhibition film on the metal surface.

Operando electrochemical SERS monitors nanoparticle reactions by capping agent fingerprints

Nanomaterials are frequently employed in daily life goods,including health,textile,and food industry.A comprehensive picture is lacking on the role of the capping agents,added ligand molecules,in case of nanoparticle reactions and degradation in aqueous solutions,like surface waters or biofluids.Here,we aim to elucidate the capping agent influence on nanoparticle reactivity probing two commonly employed capping agents citrate and polyvinylpyrrolidone(PVP).Their influence on silver nanoparticle(AgNP)transformation is studied,which is particularly important due to its application as an antimicrobial agent.We induce oxidation and reduction processes of AgNPs in halide solutions and we monitor the associated transformations of particles and capping agents by spectro-electrochemical surface-enhanced Raman spectroscopy(SERS).Raman bands of the capping agents are used here to track chemical changes of the nanoparticles under operando conditions.The sparingly soluble and non-plasmon active silver salts(AgBr and AgCl)are formed under potential bias.In addition,we spectroscopically observe plasmon-mediated structural changes of citrate to cis-or trans-aconitate,while PVP is unaltered.The different behavior of the capping agents implies a change in the physical properties on the surface of AgNPs,in particular with respect to the surface accessibility.Moreover,we showcase that reactions of the capping agents induced by different external stimuli,such as applied bias or laser irradiation,can be assessed.Our results demonstrate how SERS of capping agents can be exploited to operando track nanoparticle conversions in liquid media.This approach is envisaged to provide a more comprehensive understanding of nanoparticle fates in complex liquid environments and varied redox conditions.