Computational study of the NO, SO2, and NH3 adsorptions on fragments of 3N-graphene and Al/3N graphene

Computational investigation of sensing properties of Ca-doped zinc oxide nanotube toward formaldehyde

Following an experimental work, we employed density functionals B3LYP, B97D, CAM-B3LYP, BMK, and M06-HF to study the impact of Ca-doping on a ZnO nanotube (ZnONT) sensing performance to the formaldehyde gas. The interaction of the pristine ZnONT with the formaldehyde gas was found to be weak, and the sensing response is 0.7 based on the B3LYP results. Doping a Ca atom into the ZnONT changes the adsorption energy of formaldehyde from - 4.2 to - 36.1 kcal/mol. Energy decomposing analysis indicated that the nature of interaction is partially electrostatic and covalent. The sensing response significantly rises to 4.2 by Ca-doping (experimental value ~ 5.28). A short recovery time of 5.6 s is found for the formaldehyde gas desorption from the Ca@ZnONT surface at 300 °C. Both theory and experiment suggest that Ca-doped ZnONT may be a formaldehyde gas sensor with a short recovery time.

Recent Developments in Graphene-Based Toxic Gas Sensors: A Theoretical Overview

Detecting and monitoring air-polluting gases such as carbon monoxide (CO), nitrogen oxides (NOx), and sulfur oxides (SOx) are critical, as these gases are toxic and harm the ecosystem and the human health. Therefore, it is necessary to design high-performance gas sensors for toxic gas detection. In this sense, graphene-based materials are promising for use as toxic gas sensors. In addition to experimental investigations, first-principle methods have enabled graphene-based sensor design to progress by leaps and bounds. This review presents a detailed analysis of graphene-based toxic gas sensors by using first-principle methods. The modifications made to graphene, such as decorated, defective, and doped to improve the detection of NOx, SOx, and CO toxic gases are revised and analyzed. In general, graphene decorated with transition metals, defective graphene, and doped graphene have a higher sensibility toward the toxic gases than pristine graphene. This review shows the relevance of using first-principle studies for the design of novel and efficient toxic gas sensors. The theoretical results obtained to date can greatly help experimental groups to design novel and efficient graphene-based toxic gas sensors.

A DFT study on the adsorption of DNA nucleobases on the C3N nanotubes as a sequencer

Deoxyribonucleic acid (DNA) sequencing is a crucial issue for the cure of different kinds of diseases. Here, we computationally explored the effect of DNA nucleobases on the electronic properties and electrical conductivity of a zigzag (10,0) C₃N nanotube (C₃NNT) at B3LYP-gCP-D3 level of theory. Our calculations revealed that the binding energy of nucleobases shows the order of guanine (G) > cytosine (C) > thymine (T) > adenine (A). Based on the energy decomposition analysis (EDA), the G, C, and T strongly interact with the C₃NNT, but the A nucleobase adsorbed mainly via electrostatic attraction and dispersion forces. We exposed that the nucleobase size and its carbonyl group determine its adsorption behavior. The DNA nucleobase adsorption meaningfully increased the electrical conductivity of C₃NNT. The C₃NNT sensing response toward G, C, T, or A was predicted to be 131, 66, 60, or 10. Therefore, the C₃NNT might be applied to selectively detect the G, C, T, and A. Our findings expose the usefulness of C₃NNT as a next-generation DNA sequencer, suggesting new leads for future progresses in sustainable designs, superior sensing architectures, and bioelectronics.

High cell voltage and storage capacity of graphyne as the anode of K-ion batteries: computational studies

Li-ion batteries have many advantages, but these batteries suffer from safety problems, short lifetime, and a high cost. Nontoxicity, wide availability, and low cost of potassium offer the K-ion batteries (KIB) as a replacement to the Li-ion batteries. The B3LYP-gCP-D3 approach of density functional theory is applied to examine the probable application of graphyne in the anode of KIBs. It is found that a triangular hollow is the most favorable site for the K or K⁺ adsorption, releasing energies about 16.3 or 41.1 kcal/mol. The released energies for K and K⁺ have been reported to be about 16.8 and 34.2 kcal/mol for graphene sheet, respectively, which generate a cell voltage of 0.75 V. A high K storage capacity of 241 mAh/g and cell voltage of 1.08 V are predicted for graphyne. The maximum barrier energies for the displacement of K or K⁺ on the surface of graphyne are computed to be 2.8 (~ 3.4 for K/graphene) or 5.6 kcal/mol, representing an excellent ion mobility due to the low energy barriers. Consequently, we suggest the graphyne sheet as an anode material for the KIBs owing to its high diffusion ability, high cell voltage, and high storage capacity.