The Many Faces of Graphene as Protection Barrier. Performance under Microbial Corrosion and Ni Allergy Conditions

Graphene-coated nickel in biological environments: role of structural defects

Graphene (Gr) is a promising material for addressing microbially induced corrosion (MIC) issues that cause staggering economic losses, estimated at nearly $55 billion annually in the US alone. However, structural defects including edges, grain boundaries, and cracks can compromise its performance in aggressive biological environments. Owing to the technological relevance of nickel (Ni), its key roles in biological mechanisms, and the strong hybridization of d-electrons of Ni with Gr π-orbitals, we explore the effects of the key defects in Gr/Ni exposed to archetype sulfate-reducing bacteria (SRB). Electrochemical and spectroscopy tests revealed that the grain boundaries play a stronger role than cracks. The edges and grain boundaries in as-grown Gr on Ni (dGr/Ni) aggravated corrosion by two-fold, while the cracks in the transferred counterpart that lacked these defects improved corrosion resistance by 2-fold. A combination of biotic and abiotic studies corroborated the unique roles of grain boundaries as sulfur reservoirs to promote the attachment of sessile SRB cells and subsequent redox reactions. Analysis of distinct biogenic products confirmed the role of grain boundaries on pitting corrosion. These insights can guide the rational design of graphene coatings specifically for biological environments prone to MIC.

Fractional Factorial Design to Evaluate the Synthesis and Electrochemical Transfer Parameters of h-BN Coatings

In this study, we present a fractional factorial design approach for exploring the effects and interactions of key synthesis and electrochemical transfer parameters on the roughness and wettability of hexagonal boron nitride (h-BN) coatings, due to their essential role in biofilm formation. The studied parameters for the synthesis process include precursor mass, growth time, and substrate conditioning, whereas for the transfer process, applied voltage and aqueous medium concentration were studied. Through this polynomial model, we confirmed the strong influence of precursor mass and medium concentration parameters on h-BN surface roughness and its resulting antibiofilm properties.

Inhibition performances of graphene oxide/silver nanostructure for the microbial corrosion: molecular dynamic simulation study

Steel is one of the mainly used materials in the oil and gas industry. However, it is susceptible to the marine corrosion, which 20% of the total marine corrosion is caused by microbiologically influenced corrosion (MIC). The economic and environmental impacts of corrosion are significant, and it is crucial to fight against corrosion in a proper sustainability context and environmental-friendly methods. In this study, the graphene oxide/silver nanostructure (GO-Ag) inhibitory effect on the corrosion of steel in the presence of sulfate reducing bacteria (SRB) was investigated, via weight loss (WL) and Tafel polarization measurements. Moreover, molecular dynamic (MD) simulations were performed to obtain a deep understanding of the corrosion inhibition effect of GO-Ag. GO-Ag showed a significant antibacterial effect at 80 ppm. Moreover, WL and Tafel polarization measurements illustrated a great inhibition efficiency, which reached up to 84% reduction of WL and 98% reduction of corrosion current density (I_corr) after 7 days of incubation with GO-Ag. Based on MD simulations, bonding energy reached to the larger value in the presence of GO-Ag, which indicated the ability of graphene oxide nanosheets to be adsorbed on the steel surface and prevent the access of corrosive agents to the steel surface. The radial distribution function (RDF) results implied distance between corrosive agent (water and SRB) and steel surface (Fe atoms), which indicated protection of the steel surface due to the effective adsorption of GO nanosheets through the active sites of the steel surface. The mean square displacement (MSD) result showed smaller displacement of the corrosive particles on the surface of steel, resulting that the GO-Ag molecules bonded with Fe molecules on the surface of steel.

Microbiologically Influenced Corrosion of Copper and Its Alloys in Anaerobic Aqueous Environments: A Review

Regardless of the long record of research works based on microbiologically influenced corrosion (MIC), its principle and mechanism, which lead to accelerated corrosion, is yet to be fully understood. MIC is observed on different metallic substrates and can be caused by a wide variety of microorganisms with sulfate-reducing bacteria (SRB) being considered the most prominent and economically destructive one. Copper and its alloys, despite being used as an antimicrobial agent, are recorded to be susceptible to microbial corrosion. This review offers a research overview on MIC of copper and its alloys in anaerobic aqueous environments. Proposed MIC mechanisms, recent work and developments as well as MIC inhibition techniques are presented focusing on potable water systems and marine environment. In the future research perspectives section, the importance and possible contribution of knowledge about intrinsic properties of substrate material are discussed with the intent to bridge the knowledge gap between microbiology and materials science related to MIC.

Interactions Between 2D Materials and Living Matter: A Review on Graphene and Hexagonal Boron Nitride Coatings

Two-dimensional material (2DM) coatings exhibit complex and controversial interactions with biological matter, having shown in different contexts to induce bacterial cell death and contribute to mammalian cell growth and proliferation in vitro and tissue differentiation in vivo. Although several reports indicate that the morphologic and electronic properties of the coating, as well as its surface features (e.g., crystallinity, wettability, and chemistry), play a key role in the biological interaction, these kinds of interactions have not been fully understood yet. In this review, we report and classify the cellular interaction mechanisms observed in graphene and hexagonal boron nitride (hBN) coatings. Graphene and hBN were chosen as study materials to gauge the effect of two atomic-thick coatings with analogous lattice structure yet dissimilar electrical properties upon contact with living matter, allowing to discern among the observed effects and link them to specific material properties. In our analysis, we also considered the influence of crystallinity and surface roughness, detailing the mechanisms of interaction that make specific coatings of these 2DMs either hostile toward bacterial cells or innocuous for mammalian cells. In doing this, we discriminate among the material and surface properties, which are often strictly connected to the 2DM production technique, coating deposition and post-processing method. Building on this knowledge, the selection of 2DM coatings based on their specific characteristics will allow to engineer desired functionalities and devices. Antibacterial coatings to prevent biofouling, biocompatible platforms suitable for biomedical applications (e.g., wound healing, tissue repairing and regeneration, and novel biosensing devices) could be realized in the next future. Overall, a clear understanding on how the 2DM coating's properties may modulate a specific bacterial or cellular response is crucial for any future innovation in the field.

Inhibition of Wild Enterobacter cloacae Biofilm Formation by Nanostructured Graphene- and Hexagonal Boron Nitride-Coated Surfaces

Although biofilm formation is a very effective mechanism to sustain bacterial life, it is detrimental in medical and industrial sectors. Current strategies to control biofilm proliferation are typically based on biocides, which exhibit a negative environmental impact. In the search for environmentally friendly solutions, nanotechnology opens the possibility to control the interaction between biological systems and colonized surfaces by introducing nanostructured coatings that have the potential to affect bacterial adhesion by modifying surface properties at the same scale. In this work, we present a study on the performance of graphene and hexagonal boron nitride coatings (h-BN) to reduce biofilm formation. In contraposition to planktonic state, we focused on evaluating the efficiency of graphene and h-BN at the irreversible stage of biofilm formation, where most of the biocide solutions have a poor performance. A wild Enterobacter cloacae strain was isolated, from fouling found in a natural environment, and used in these experiments. According to our results, graphene and h-BN coatings modify surface energy and electrostatic interactions with biological systems. This nanoscale modification determines a significant reduction in biofilm formation at its irreversible stage. No bactericidal effects were found, suggesting both coatings offer a biocompatible solution for biofilm and fouling control in a wide range of applications.

Low-Temperature CVD Graphene Nanostructures on Cu and Their Corrosion Properties

Chemical vapor deposition (CVD) graphene is reported to effectively prevent the penetration of outer factors and insulate the underneath metals, hence achieving an anticorrosion purpose. However, there is little knowledge about their characteristics and corresponding corrosion properties, especially for those prepared under different parameters at low temperatures. Using electron cyclotron resonance chemical vapor deposition (ECR-CVD), we can successfully prepare graphene nanostructures on copper (Cu) at temperatures lower than 600 °C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and potentiodynamic polarization measurements were used to characterize these samples. In simulated seawater, i.e., 3.5 wt.% sodium chloride (NaCl) solution, the corrosion current density of one graphene-coated Cu fabricated at 400 °C can be 1.16 × 10⁻⁵ A/cm², which is one order of magnitude lower than that of pure Cu. Moreover, the existence of tall graphene nanowalls was found not to be beneficial to the protection as a consequence of their layered orientation. These correlations among the morphology, structure, and corrosion properties of graphene nanostructures were investigated in this study. Therefore, the enhanced corrosion resistance in selected cases suggests that the low-temperature CVD graphene under appropriate conditions would be able to protect metal substrates against corrosion.

CVD Synthesis of Monodisperse Graphene/Cu Microparticles with High Corrosion Resistance in Cu Etchant

Copper powder has broad applications in the powder metallurgy, heat exchanger, and electronic industries due to its intrinsically high electrical and thermal conductivities. However, the ease of formation of surface oxide or patina layer raises difficulty of storage and handling of copper powder, particularly in the case of Cu microparticles. Here, we developed a thermal chemical vapor deposition chemical vapor deposition (CVD) process for large-scale synthesis of graphene coatings on Cu microparticles, which importantly can remain monodisperse without aggregation after graphene growth at high temperature by using removal spacers. Compared to other protective coating methods, the intrinsic electrical and thermal properties of Cu powder would not be degraded by uniform growth of low defect few-layer graphene on each particle surface. As a result, when the anticorrosion performance test was carried out by immersing the samples in Cu etchant, the corrosion rate of graphene/Cu microparticles was significantly improved (ca three times slower) compared to that of pristine Cu powder, also showing a comparable anticorrosion ability to commercial CuZn30 alloy.