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C2N bild
Figure: (a) The optimized structure and 2D ELF plots of 2  2  1 supercell of C2N nanosheet and (b-d) The ground state geometries of C2N nanosheets adsorbed with glucose, fructose, and xylose (Colour scheme: brown: C, gray: N, red: O, pink: H). The ELF values 0, 0.5, and 1 interpret as the absence, uniform electron gas-like, and localized electrons. View original picture , opens in new tab/window

2D nanosheet materials as efficient and reusable sensors

Published: 28 October 2021

We study atomically thin nanomaterials as potential sensors using quantum mechanical modelling of molecular adsorption. A material similar to graphene but containing carbon and nitrogen in proportion two to one (C2N) is showing great promise as a sensor of airborne molecular pollutants and molecules in biological fluids. For molecules in fluids, we have targeted sensing of sugar levels.

 Diabetes mellitus is an incurable disease, giving rise to elevated blood glucose levels. Therefore, detecting blood sugar levels is an integral part of diabetes care. The available standard self-monitoring blood glucose sensors are typically dependent on an expensive glucose oxidase enzyme-based recognition unit while dealing with the painful finger pricking process. Besides, the enzymatic glucose sensors go through low detection limit and stability issues with variations of operating temperatures, pH values, and humidity. A better scenario for self-monitoring of diabetes would be to use novel low-cost and stable glucose sensors, which are sensitive enough towards glucose-sensing that alternative body fluids like tears, sweat, or saliva can be used instead of blood. 

Two-dimensional materials are ideal for sensing applications, which is attributed to their high surface-to-volume ratio. Experimentally synthesized C2N nanosheets possess great potential for sensing applications because of the electron loan-pair located on each N atom, resulting in strong localized dipole moments that interact with molecules on their surface. In our work, we proposed the potential of the C2N nanosheet for the detection of sugar molecules (glucose, fructose, and xylose) by employing state-of-the-art first-principles calculations that include van der Waals interactions to determine how the sugars adsorb on the sensor surface and non-equilibrium Green’s function methods to simulate the electric response inferred in the nanosheet. The work funded by Kempe stiftelserna, Knut och Alice Wallenber Foundation and Interreg Nord, and was a collaboration between Luleå University of Technology (Sweden), Hindustan Institute of Technology and Science (India), Khalifa University (United Arab Emirates), Uppsala University (Sweden), and the University of Queensland (Australia). The C2N nanosheet is not consumed and destroyed through usage because the molecules are strongly physisorbed (not chemically bound) due to the dipole moments on the nitrogens. In addition, the molecular binding strengths are small enough to be forced to unbind, making C2N nanosheets an ideal material for reuse after cleaning. Our findings will pave the way for developing an efficient sensor for detecting blood sugar.