Highly sensitive sensing of CO and HF gases by monolayer CuCl

Using a first-principles approach, the adsorption characteristics of CO and HF on a CuCl monolayer (ML) are studied with Grimme-scheme DFT-D2 for accurate description of the long-range (van der Waals) interactions. According to our study, CO gas molecules undergo chemisorption and HF gas molecules show a physisorption phenomenon on the CuCl monolayer. The adsorption energy for CO is -1.80 eV, which is quite a large negative value compared to that on other previously studied substrates, like InN (-0.223 eV), phosphorene (0.325 eV), Janus Te2Se (-0.171 eV), graphene (P-graphene, -0.12 eV, B-graphene, -0.14 eV, N-graphene, -0.1 eV) and monolayer ZnS (-0.96 eV), as well as pristine hBN (0.21 eV) and Ti-doped hBN (1.66 eV). Meanwhile, for HF, the adsorption energy value is -0.31 eV (greater than that of Ti-doped hBN, 0.27 eV). For CO, the large value of the diffusion energy barrier (DEB = 1.26 eV) during its movement between two optimal sites indicates that clustering can be prevented if many molecules of CO are adsorbed on the CuCl ML. For HF, the value of the DEB (0.082 eV) implies that the adsorption phenomenon may happen quite easily upon the CuCl ML. The transfer of charge according to Bader charge analysis and the variation in the work function depend only on the properties of the elements involved, i.e., their nature, rather than the local binding environment. The work function and band-gap energy variation of the CuCl ML (before and after adsorption) show high sensitivity and selectivity of CO and HF binding with the CuCl monolayer. HF molecules give a more rapid recovery time of 1.09 × 10-7 s compared to that of CO molecules at a room temperature (RT) of 300 K, which indicates that the necessary adsorption and reusability of the CuCl ML for HF can be accomplished effectively at RT. Significant changes in the conductivity are observed due to the CO adsorption at various temperatures, as compared to adsorption of HF, which suggests the possibility of a modification in the conductivity of the CuCl ML.

Unravelling performance of honeycomb structures as drug delivery systems for the isoniazid drug using DFT-D3 correction dispersion and molecular dynamic simulations

In this study, the potential of aluminum nitride (h-AlN), boron nitride (h-BN) and silicon carbide (h-SiC) nanosheets as the drug delivery systems (DDS) of isoniazid (INH) was scrutinized through density functional theory (DFT) and molecular dynamic (MD) simulations. We performed DFT periodic calculations on the geometry and electronic features of nanosheets adsorbed with INH by the DFT functional (DZP/GGA-PBE) employed in the SIESTA code. In the energetically favorable model, an oxygen atom of the C-O group of the INH molecule interacts with a Si atom of the h-SiC at 2.077 Å with an interaction energy of -1.361 eV. Charge transfer (CT) calculation by employing the Mulliken, Hirshfeld and Voronoi approaches reveals that the monolayers and drug molecules act as donors and acceptors, respectively. The density of states (DOS) calculations indicate that the HOMO-LUMO energy gap (HLG) of the h-SiC nanosheet declines significantly from 2.543 to 1.492 eV upon the adsorption of the INH molecule, which causes an electrical conductivity increase and then produces an electrical signal. The signal is linked to the existence of INH, demonstrating that h-SiC may be an appropriate sensor for INH sensing. The decrease in HLG for the interaction of INH and h-SiC is the uppermost (up to 41%) representing the uppermost sensitivity, whereas the sensitivity trend is σ(h-SiC) > σ(h-AlN) > σ(h-BN). Quantum theory of atoms in molecules (QTAIM) investigations is employed to scrutinize the nature of the INH/nanosheet interactions. The QTAIM analysis reveals that the interaction of the INH molecule and h-SiC has a partially covalent nature, while INH/h-AlN model electrostatic interaction occurs in the system and noncovalent and electrostatic interaction for the INH/h-BN model. Finally, the state-of-the-art DFT-MD simulations utilized in this study can mimic ambient conditions. The results obtained from the MD simulation show that it takes more time to bond the INH drug and h-SiC, and the INH/h-SiC system becomes stable. The results of the current research demonstrate the potential of h-SiC as a suitable sensor and drug delivery platform for INH drugs to remedy tuberculosis.

Investigation of the electronic and optical properties of bilayer CdS as a gas sensor: first-principles calculations

We utilised first-principles computations based on density functional theory to investigate the optical and electronic properties of bilayer CdS before and after the adsorption of gas molecules. Initially, we examined four candidate adsorption sites to determine the best site for adsorbing CO, CO2, SO2, H2S, and SO. In order to achieve the optimal adsorption configurations, we analysed the adsorption energy, distance, and total charge. Our findings reveal that the CdS bilayer forms a unique connection between the O and Cd atoms, as well as the S and Cd atoms, which renders it sensitive to SO2, H2S, and SO through chemical adsorption, and CO and CO2 through strong physical adsorption. The adsorption of gas molecules enhances the optical properties of the CdS bilayer. Consequently, the CdS bilayer proves to be a highly efficient gas sensor for SO2, H2S, and SO gases.

Phosphorus-doped T-graphene nanocapsule toward O3 and SO2 gas sensing: a DFT and QTAIM analysis

Tetragonal graphene nano-capsule (TGC), a novel stable carbon allotrope of sp2 hybridization is designed and doped with phosphorus (P) to study the O3 and SO2 gas sensitivity via density functional theory calculation. Real frequencies verified the natural existence of both TGC and P-doped TGC (PTGC). Both TGC and PTGC suffer structural deformations due to interaction with O3 and SO2 gases. The amount of charge transfer from the adsorbent to the gas molecule is significantly greater for O3 adsorption than SO2 adsorption. The adsorption energies for TGC + O3 and PTGC + O3 complexes are - 3.46 and - 4.34 eV respectively, whereas for TGC + SO2 and PTGC + SO2 complexes the value decreased to - 0.29 and - 0.30 eV respectively. The dissociation of O3 is observed via interaction with PTGC. A significant variation in electronic energy gap and conductivity results from gas adsorption which can provide efficient electrical responses via gas adsorption. The blue/red shift in the optical response proved to be a way of detecting the types of adsorbed gases. The adsorption of O3 is exothermic and spontaneous whereas the adsorption of SO2 is endothermic and non-spontaneous. The negative change in entropy verifies the thermodynamic stability of all the complexes. QTAIM analysis reveals strong covalent or partial covalent interactions between absorbent and adsorbate. The significant variation in electrical and optical response with optimal adsorbent-gas interaction strength makes both TGC and PTGC promising candidates for O3 and SO2 sensing.

Adsorption and sensor performance of transition metal-decorated zirconium-doped silicon carbide nanotubes for NO2 gas application: a computational insight

Owing to the fact that the detection limit of already existing sensor-devices is below 100% efficiency, the use of 3D nanomaterials as detectors and sensors for various pollutants has attracted interest from researchers in this field. Therefore, the sensing potentials of bare and the impact of Cu-group transition metal (Cu, Ag, Au)-functionalized silicon carbide nanotube (SiCNT) nanostructured surfaces were examined towards the efficient detection of NO2 gas in the atmosphere. All computational calculations were carried out using the density functional theory (DFT) electronic structure method at the B3LYP-D3(BJ)/def2svp level of theory. The mechanistic results showed that the Cu-functionalized silicon carbide nanotube surface possesses the greatest adsorption energies of -3.780 and -2.925 eV, corresponding to the adsorption at the o-site and n-site, respectively. Furthermore, the lowest energy gap of 2.095 eV for the Cu-functionalized surface indicates that adsorption at the o-site is the most stable. The stability of both adsorption sites on the Cu-functionalized surface was attributed to the small ellipticity (ε) values obtained. Sensor mechanisms confirmed that among the surfaces, the Cu-functionalized surface exhibited the best sensing properties, including sensitivity, conductivity, and enhanced adsorption capacity. Hence, the Cu-functionalized SiCNT can be considered a promising choice as a gas sensor material.

Evaluation of experimental, computational, molecular docking and dynamic simulation of flucytosine

Flucytosine (5-fluorocytosine), a fluorine derivative of pyrimidine, has been studied both experimentally and quantum chemically. To obtain the optimized structure, vibrational frequencies and other various parameters, the B3LYP method with a 6-311++G(d,p) basis set was used. Atom-in-molecule theory was used to calculate the binding energies, ellipticity and isosurface projection by electron localization of the molecule (AIM). In addition, the computational results from IR and Raman were compared with the experimental spectra. NBO analysis was used to analyze the donor and acceptor interactions. To know the reactive region of the molecule, the molecular electrostatic potential (MEP) and Fukui functions were determined. The UV-Vis spectrum calculated by the TD-DFT/PCM method was also compared with the experimentally determined spectrum. The HOMO-LUMO energy outcomes proved that there was a good charge exchange occurring within the molecule. With DMSO and MeOH as the solvents, maps of the hole and electron density distribution (EDD and HDD) were produced in an excited state. An electrophilicity index parameter was looked at to theoretically test the bioactivity of the compound. To find the best ligand-protein interactions, molecular docking was also carried out with various receptor proteins. In order to verify the inhibitory potency for the receptor protein complex predicted by docking and molecular dynamic simulation studies, the binding free energy of the receptor protein complex was calculated. Using the MM/GBSA technique, we determined the docked complex's binding free energy. To confirm the molecule's drug similarity, a biological drug similarity investigation was also executed.Communicated by Ramaswamy H. Sarma.

Anab initiostudy of catechol sensing in pristine and transition metal decoratedγ-graphyne

Catechol is a toxic biomolecule due to its low degradability to the ecosystem and unpredictable impact on human health. In this work, we have investigated the catechol sensing properties of pristine and transition metal (Ag, Au, Pd, and Ti) decoratedγ-graphyne (GY) systems by employing the density functional theory and first-principles molecular dynamics approach. Simulation results revealed that Pd and Ti atom is more suitable than Ag and Au atom for the decoration of the GY structure with a large charge transfer of 0.29e and 1.54e from valence d-orbitals of the Pd/Ti atom to the carbon-2p orbitals of GY. The GY + Ti system offers excellent electrochemical sensing towards catechol with charge donation of 0.14e from catechol O-p orbitals to Ti-d orbitals, while the catechol molecule is physisorbed to pristine GY with only 0.04e of charge transfer. There exists an energy barrier of 5.19 eV for the diffusion of the Ti atom, which prevents the system from metal-metal clustering. To verify the thermal stability of the sensing material, we have conducted the molecular dynamics simulations at 300 K. We have reported feasible recovery times of 2.05 × 10^-5s and 4.7 × 10²s for sensing substrate GY + Pd and GY + Ti, respectively, at 500 K of UV light.

Investigation and comparison of graphene nanoribbon and carbon nanotube based SARS-CoV-2 detection sensors: An ab initio study

The rapid detection of SARS-CoV-2, the pathogen of the Covid-19 pandemic, is obviously of great importance for stopping the spread of the virus by detecting infected individuals. Here, we report the ab initio analysis results of graphene nanoribbon (GNR) and carbon nanotube (CNT) based SARS-CoV-2 detection sensors which are experimentally demonstrated in the literature. The investigated structures are the realistic molecular models of the sensors that are employing 1-pyrenebutyric acid N-hydroxysuccinimide ester as the antibody linker. Density functional theory in conjunction with non-equilibrium Green's function formalism (DFT-NEGF) is used to obtain the transmission spectra, current-voltage and resistance-voltage characteristics of the sensors before and after the attachment of the SARS-CoV-2 spike protein. The operation mechanism of the GNR and CNT based SARS-CoV-2 sensors are exposed using the transmission spectrum analysis. Moreover, it is observed that GNR based sensor has more definitive detection characteristics compared to its CNT based counterpart.

From Fundamental to CO2 and COCl2 Gas Sensing Properties of Pristine and Defective Si2BN Monolayer

The capability of Si2BN monolayer (Si2BN-ML) in sensing CO2 and COCl2 molecules is investigated by analyzing the structural, electronic, mechanical and gas sensing properties of defect-free and defective Si2BN-ML. Electronic...