Here we present a Density Functional Theory (DFT) study on the suitability of modern corrections for the inclusion of dispersion related terms (DFT-D) in treating the interaction of graphene and metal surfaces, exemplified by the graphene/Ni(111) system. The Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional is used as basis, on top of which we tested the family of Grimme corrections (D2 and D3, including Becke-Jonson damping and Andersson approach) as well as different flavors of the approach by Tkatchenko and Scheffler (TS). Two experimentally observed chemisorbed states, top-fcc and bridge-top conformations, were examined, as well as one physisorbed situation, the hcp-fcc state. Geometric, energetic, and electronic properties were compared to sets of experimental data for our model system of graphene/Ni(111), but also for available data of bulk Ni, graphite, and free-standing graphene. Results show that two of the most recent approximations, the fully ab initio TS-MBD, and the semi-empirical Grimme D3 correction are best suited to describe graphene↔metal contacts, yet, comparing to earlier studies, the Rev-vdW-DF2 functional is also a good option, whereas optB86-vdW and optB88b-vdW functionals are fairly close to experimental values to be harmless used. The present results highlight how different approaches for the approximate treatment of dispersive forces yield different results, and so finetuning and testing of the envisioned approach for every specific system is advisable. The present survey clears the path for future accurate and affordable theoretical studies of nanotechnologic devices based on graphene-metal contacts.
Microcantilever-based platforms are presented as versatile lab-on-chip devices for advanced applications spanning from material characterization and environmental monitoring to energy.
In this work we present a successful strategy to convert recycled LDPE films, which usually end up in landfills or leak into the environment, in an advanced biomedical product. More specifically, LDPE films for food packaging have been treated with atmosphere corona discharge plasma for electrochemical detection of glucose. Enzymefunctionalized sensors manufactured using such recycled material, which acts as a mediator capable of electro-communicating with the glucose oxidase (GOx) enzyme, are able to detect glucose concentrations in sweat that are fully compatible with the levels of such bioanalyte in both healthy and diabetic patients. Covalent immobilization of the GOx enzyme on the plasma treated LDPE films has been successfully performed using the carbodiimide method, as proved by X-ray photoelectron spectroscopy. Then, the electronic communication between the deeply buried active site of the GOx and the reactive excited species formed at the surface of the plasma-treated LDPE has been demonstrated by linear sweep voltammetry. Finally, cyclic voltammetry in artificial sweat has been used to show that the LDPE-functionalized sensor has a linear response in the concentration of range of 50 M to 1 mM with a limit of detection of 375 A•M -1 •cm -2 . Comparison of the performance of sensors prepared using recycled (i.e. with additives) and pristine (i.e. without additives) LDPE indicates that the utilization of the former does not require any pre-treatment to eliminate additives. The present strategy demonstrates a facile approach for recycling LDPE waste into a high valueadded product, which will potentially pave the way for the treatment of plastic waste in the future. Non-invasive glucose sensors based on recycled LDPE may play a crucial role for monitoring diabetes in underdeveloped regions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.