Graphene Oxide-Mediated Protection from Photodamage

This Letter presents the unique properties of graphene oxide (GO) as a multitask material protecting from UVB-induced photodamage. Three mechanisms of GO action on fibroblast in vitro cultures are verified here: physical - a barrier blocking UV radiation; chemical - antioxidative activity; and biological - activation of cellular antioxidative defense. The changes in GO physicochemical properties appearing due to UVB exposure underpin the observed UV protection phenomena. The results reveal the simultaneous occurrence of two opposed processes, i.e., under small doses of UVB, the tested material undergoes oxidation and sp² network rebuilding. In the vicinity of the GO surface, the locally triggered high temperature is responsible for a reduction process, while strong oxidative agents such as OH radicals cause parallel GO oxidation. This phenomenon is enabled thanks to the exceptional properties of carbonaceous materials. As a consequence, GO turns out to be a multitask UV protector increasing fibroblast survival

Nanoscale Water Contact Angle on Polytetrafluoroethylene Surfaces Characterized by Molecular Dynamics–Atomic Force Microscopy Imaging

The aim of this study is to link polytetrafluoroethylene (PTFE) surface characteristics with its wetting properties in the nanoscale. To do this using molecular dynamics (MD) simulation, three series of rough PTFE surfaces were generated by annealing and compressing and next characterized by the application of the MD version of the atomic force microscopy (AFM) method. The values of specific surface areas were additionally calculated. The TIP4P/2005 water model was used to study the wetting properties of obtained PTFE samples. The simulated water contact angle (WCA) value for the most flat (but slightly rough) sample having PTFE density is equal to 106.94°, and it is close to the value suggested for a perfect PTFE surface on the basis of experimental results. Also, the changes in the WCA with PTFE compression are in the same range as experimentally reported. The obtained MD simulation results make it possible to link, for the first time, the WCA values with the surface MD–AFM root-mean-square roughness and with the PTFE density. Finally, we show that for PTFE wetting in the nanoscale, the line tension is negligible and the Bormashenko’s equation reduces to the Cassie–Baxter (CB) model. In fact, our simulation results are close to the CB mechanism

Water at Curved Carbon Surface: Mechanisms of Adsorption Revealed by First Calorimetric Study

Water adsorption isotherms and calorimetrically measured enthalpy of this process are reported for a series of modified chemically single and multiwalled nanotubes. On the basis of calorimetric measurements, entropy of adsorption is calculated and discussed. Next the data are described using popular models of adsorption, and finally a new approach for simultaneous description of water adsorption and enthalpy of this process is discussed. On the basis of the results of this model, four different possible mechanisms of water adsorption in nanotubes are proposed

Carbon Molecular Sieves: Reconstruction of Atomistic Structural Models with Experimental Constraints

We propose a novel methodology for developing experimentally informed structural models of disordered carbon molecular sieves. The hybrid reverse Monte Carlo simulation method coupled with wide-angle X-ray scattering experiments is used for constructing an atomistic level model of a representative sample of carbon molecular sieve film (CMS-F) synthesized in our laboratory. We found that CMS-F possesses a disordered matrix enriched with bended carbon chains and various carbon clusters as opposed to the turbostratic carbon or graphite-like microcrystals. The pore structure of CMS-F has a defected lamellar morphology of one-dimensional periodicity with narrow (∼0.4 nm) micropores. The model is applied to study adsorption properties of CMS-F with respect to adsorbates of practical interest, such as N₂, H₂, CO, and C₆H₆. Special attention is paid to the phase transformations in the course of adsorption. In particular, we show theoretically and confirm experimentally that nitrogen solidifies within CMS-F pores at 77 K upon adsorption of 5 mmol/g, and its further adsorption is associated with the adsorbed phase compression induced by strong surface forces

Carbon Molecular Sieves: Reconstruction of Atomistic Structural Models with Experimental Constraints

We propose a novel methodology for developing experimentally informed structural models of disordered carbon molecular sieves. The hybrid reverse Monte Carlo simulation method coupled with wide-angle X-ray scattering experiments is used for constructing an atomistic level model of a representative sample of carbon molecular sieve film (CMS-F) synthesized in our laboratory. We found that CMS-F possesses a disordered matrix enriched with bended carbon chains and various carbon clusters as opposed to the turbostratic carbon or graphite-like microcrystals. The pore structure of CMS-F has a defected lamellar morphology of one-dimensional periodicity with narrow (∼0.4 nm) micropores. The model is applied to study adsorption properties of CMS-F with respect to adsorbates of practical interest, such as N₂, H₂, CO, and C₆H₆. Special attention is paid to the phase transformations in the course of adsorption. In particular, we show theoretically and confirm experimentally that nitrogen solidifies within CMS-F pores at 77 K upon adsorption of 5 mmol/g, and its further adsorption is associated with the adsorbed phase compression induced by strong surface forces