Competitive and/or cooperative interactions of graphene-family materials and benzo[a]pyrene with pulmonary surfactant: a computational and experimental study

Background Airborne nanoparticles can be inhaled and deposit in human alveoli, where pulmonary surfactant (PS) molecules lining at the alveolar air–water interface act as the first barrier against inhaled nanoparticles entering the body. Although considerable efforts have been devoted to elucidate the mechanisms underlying nanoparticle-PS interactions, our understanding on this important issue is limited due to the high complexity of the atmosphere, in which nanoparticles are believed to experience transformations that remarkably change the nanoparticles’ surface properties and states. By contrast with bare nanoparticles that have been extensively studied, relatively little is known about the interactions between PS and inhaled nanoparticles which already adsorb contaminants. In this combined experimental and computational effort, we investigate the joint interactions between PS and graphene-family materials (GFMs) with coexisting benzo[a]pyrene (BaP). Results Depending on the BaP concentration, molecular agglomeration, and graphene oxidation, different nanocomposite structures are formed via BaPs adsorption on GFMs. Upon deposition of GFMs carrying BaPs at the pulmonary surfactant (PS) layer, competition and cooperation of interactions between different components determines the interfacial processes including BaP solubilization, GFM translocation and PS perturbation. Importantly, BaPs adsorbed on GFMs are solubilized to increase BaP’s bioavailability. By contrast with graphene adhering on the PS layer to release part of adsorbed BaPs, more BaPs are released from graphene oxide, which induces a hydrophilic pore in the PS layer and shows adverse effect on the PS biophysical function. Translocation of graphene across the PS layer is facilitated by BaP adsorption through segregating it from contact with PS, while translocation of graphene oxide is suppressed by BaP adsorption due to the increase of surface hydrophobicity. Graphene extracts PS molecules from the layer, and the resultant PS depletion declines with graphene oxidation and BaP adsorption. Conclusion GFMs showed high adsorption capacity towards BaPs to form nanocomposites. Upon deposition of GFMs carrying BaPs at the alveolar air–water interface covered by a thin PS layer, the interactions of GFM-PS, GFM-BaP and BaP-PS determined the interfacial processes of BaP solubilization, GFM translocation and PS perturbation.

Structural Defects of Graphene Oxidation Reduction and Its High-Efficiency Structural Reforming Technology

The Hummers’ method is used to prepare graphene oxide and graphene powder, and the obtained powder material contains a large amount of oxygen-containing groups. Due to the effect of strong oxidants, there are many defects on the graphene body. Although a large number of oxygen-containing groups are reduced by the reduction reaction, the defects of the graphene body are numerous, which has a great influence on the conductivity of graphene and also limits the high carrier transport capability and application of graphene itself. Using industrial means, the graphene powder is highly reduced, and the ultrathin graphene powder is obtained, the graphene powder has extremely low impurity content, and the defects are substantially completely reduced. Then, these lay the foundation for its application in the battery industry.

Joint Interactions of Graphene and Benzo[a]pyrene With Pulmonary Surfactant

Background: Airborne nanoparticles can be inhaled and deposit in human alveoli, where pulmonary surfactant (PS) molecules line at the alveolar air-water interface to act as the first barrier against inhaled nanoparticles entering the body. Although considerable efforts have been made to elucidate the mechanisms underlying nanoparticle-PS interactions, our understanding on this important issue is limited due to the high complexity of the atmosphere, in which nanoparticles are believed to experience transformations that remarkably change the nanoparticles’ surface properties and states. By contrast with bare nanoparticles that have been extensively studied, relatively little is known about the interactions between PS and inhaled nanoparticles which already adsorb contaminants. In this combined experimental and computational effort, we investigate the joint interactions between PS and graphene with coexisting benzo[a]pyrene (BaP).Results: Depending on the BaP concentration and molecular agglomeration, different nanocomposite structures are formed via BaPs adsorption on graphene. Upon deposition of graphene carrying BaPs at the pulmonary surfactant (PS) layer, competition of interactions between different components determines the interfacial processes including BaP solubilization, graphene translocation and PS perturbation. Importantly, BaP adsorbed on graphene is solubilized to increase its bioavailability and inhibit the PS biophysical function. Translocation of graphene across the PS layer is facilitated by BaP adsorption through segregating it from contact with PS, while translocation of graphene oxide is suppressed due to increase of the surface hydrophobicity. Graphene extracts PS molecules from the layer, and the resultant PS depletion declines with graphene oxidation and BaP adsorption.Conclusion: Graphene showed high capacity of adsorbing BaPs to form nanocomposites, which were inhaled and deposit in alveoli, where competition of interactions between different components determined the interfacial processes of BaP solubilization, graphene translocation and PS perturbation.

Quartz crystal microbalance monitoring of large-area graphene anodization reveals layer fracturing

Graphene has numerous potential applications in ultrathin electronics. There an electrode should function in contact with fluids and under mechanical stress; therefore, its stability is specifically of concern. Here, we explored a custom-made quartz crystal microbalance (QCM) sensor covered with wet-transferred large-scale monolayer graphene for investigation of an electrode behavior. Monolayer graphene was found to be stable on an oscillating substrate in contact with air and liquid. Under the liquid flow and simultaneously applied electrochemical potential, we managed to induce graphene oxidation, impact of which was observed on a quartz crystal microbalance monitoring and Raman spectra. Applied potentials of 1 V and higher (vs. Ag/AgCl reference electrode) caused graphene oxidation which led to loss of the layer integrity and erosion of the material. Graphic abstract

Oxidation of graphene with variable defects: alternately symmetrical escape and self-restructuring of carbon rings

Graphene oxidation proceeds in a symmetrical manner on the vacancy. Disordered rings on grain boundaries self-restructure.