Nitrate adsorption by carbon nanotubes in the vacuum and aqueous phase

A DFT study of pure and Si-decorated boron nitride allotrope Irida monolayer as an effective sensor for hydroxyurea drug

Investigating effective nanomaterials for the detection of hydroxyurea anticancer drugs is essential for promoting human health and safeguarding environmental integrity. This research utilized first-principles estimations for examining the adhesion and electronic characteristics of hydroxyurea (HU) on both pristine and Si-decorated innovative two-dimensional boron nitride allotrope, known as Irida analogous (Ir-BNNS). Analyzing the adsorption energy revealed that the HU molecule has a significant interaction (Ead = -1.27 eV) with the Si@Ir-BNNS, whereas it has weak interaction P-Ir-BN. Moreover, the analysis of the electron density distributions was conducted to investigate the microcosmic interaction mechanism between HU and Ir-BNNS. The Si@Ir-BNNS was highly sensitive to HU due to the observable alterations in the electrical conductance and magnetism. At ambient temperature, the Si@Ir-BNNS had a recovery time of 5.96 ms towards HU molecules. The DFT estimations can be conducive to exploring the applications of Si@Ir-BNNS in effectively sensing HU.

Carbon Nanostructures Doped with Transition Metals for Pollutant Gas Adsorption Systems

The adsorption of molecules usually increases capacity and/or strength with the doping of surfaces with transition metals; furthermore, carbon nanostructures, i.e., graphene, carbon nanotubes, fullerenes, graphdiyne, etc., have a large specific area for gas adsorption. This review focuses on the reports (experimental or theoretical) of systems using these structures decorated with transition metals for mainly pollutant molecules' adsorption. Furthermore, we aim to present the expanding application of nanomaterials on environmental problems, mainly over the last 10 years. We found a wide range of pollutant molecules investigated for adsorption in carbon nanostructures, including greenhouse gases, anticancer drugs, and chemical warfare agents, among many more.

Carboxylated carbon nanotubes corked with tetraalkylammonium cations: A concept of nanocarriers in aqueous solutions

An explicit water molecular dynamics simulations were used to probe (6,6) and (9,9) single-walled carbon nanotubes, functionalized with three carboxylate ion groups at each of the two openings, as potential nanocarriers in aqueous solutions. Three tetraalkylammonium cations (i.e., tetraethyl-, tetrapropyl-, and tetrabuthylammonium) were tested as corks to cap the nanotube openings. The variation of the sizes of the nanotubes (diameter) and of the cork cations (bulkiness) allowed us to select the proper corks that fit the nanotube openings best. Smaller tetraalkylammonium ions could easily fit the openings, but since they are less hydrophobic compared to their larger analogues they showed less affinity for the interior of the nanotubes. On the other hand, the hydrophobicity (and thus the affinity for the nanotubes) can be adjusted through the increase of tetraalkylammonium cation size, providing that the cork still fits the opening. Additionally, an external electric field was tested as a means of nanotube uncorking. The field is capable of disjoining corked ions from the functionalized nanotube openings, triggering in this way a potential cargo release stored inside the nanotubes.

Hydrogen Adsorption on Nearly Zigzag-Edged Nanoribbons: A Density Functional Theory Study

The realistic shapes of N doped graphene nanoribbons (GNRs) can be realized by considering nearly zigzag-edged (NZE) imperfections and pyridine defects (3NV). The paper focuses on NZE-GNRs with 3NV that is populated by Scandium abbreviated as Sc/NZE-3NVGNRs. Systematic calculations have clarified roles of the nano-shapes of NZE-3NVGNRs in its formation, energetics, stability and electron states functionalized with Sc using density functional theory (DFT) formalisms. According to DFT calculations, the magnitude of the spin that is attributed to the rise of magnetic order is closely linked to the altered shape of the ribbon edges. Also, calculations show that the stability of Sc functionalization at the 3NV and NZE site is thermodynamically stable and is dictated by a strong binding energy (BE). The magnitude of the BE is enhanced when the zigzag edge is short or the ribbon width is narrow, suggesting a reduced clustering of Sc atoms over the Sc-doped NZE-3NVGNRs. Results also show that as the length of the zigzag edge in Sc/NZE-3NVGNRs increases it creates considerable distortion on the appearance of the structure. Finally, the Sc/NZE-3NVGNRs as a potential candidate for hydrogen storage was evaluated and it was found that it could adsorb multiple hydrogen molecules.

Na-ion batteries based on the inorganic BN nanocluster anodes: DFT studies

It has been recently indicated that the Li-ion batteries may be replaced by Na-ion batteries because of their low safety, high cost, and low-temperature performance, and lack of the Li mineral reserves. Here, using density functional theory calculations, we studied the potential application of B₁₂N₁₂ nanoclusters as anode in Na-ion batteries. Our calculations indicate that the adsorption energy of Na⁺ and Na are about -23.4 and -1.4kcal/mol, respectively, and the pristine BN cage to improve suffers from a low cell voltage (∼0.92V) as an anode in Na-ion batteries. We presented a strategy to increase the cell voltage and performance of Na-ion batteries. We showed that encapsulation of different halides (X=F^-, Cl^-, or Br^-) into BN cage significantly increases the cell voltage. By increasing the atomic number of X, the Gibbs free energy change of cell becomes more negative and the cell voltage is increased up to 3.93V. The results are discussed based on the structural, energetic, frontier molecular orbital, charge transfer and electronic properties and compared with the performance of other nanostructured anodes.

A theoretical study on monoatomic BN nanochains and nanorings

Boron nitride (BN) nanochains were successfully synthesized recently. In this work, we investigate the electronic, energetic, and structural properties of BN nanochains and nanorings by means of density functional theory calculations. Our calculations support the experimental findings and offer additional physical insights into these new nanostructured materials. We show that BN nanochains are biracial compounds that tend to be closed and form a ring. They have single and double bonds alternately throughout the chain. The boron atoms are not saturated and are strong Lewis acids. Increase in the length of the chain tends to result in the conversion from a semiconductor to a semimetal material. The ring structures are stabler than the corresponding chains, and unlike the chains these structures are predicted to be insulators. The binding energy of the chains and rings increases with an increase in their size. Rings with odd or even numbers of BN units show different electronic properties.

Transition metal doped ZnO nanoclusters for carbon monoxide detection: DFT studies

Metal doped ZnO nanomaterials have attracted considerable attention as a chemical sensor for toxic gases. Here, the electronic sensitivity of pristine and Sc-, Ti-, V-, Cr-, Mn-, and Fe-doped Zn12O12 nanoclusters toward CO gas is investigated using density functional theory calculations. It is found that replacing a Zn atom by a Sc or Ti atom does not change the sensitivity of cluster but doping V and Cr atoms significantly increase the sensitivity. Also, Mn, or Fe doping slightly improves the sensitivity. It is predicted that among all, the Cr-doped ZnO cluster may be the most favorable sensor for CO detection because its electrical conductivity considerably changes after the CO adsorption, thereby, generating an electrical signal. The calculated Gibbs free energy change for the adsorption of CO molecule on the Cr-doped cluster is about -51.2 kcal mol(-1) at 298.15 K and 1 atm, and the HOMO-LUMO gap of the adsorbent is changed by about 117.8 %.

Adsorption of carbon monoxide on the pristine, B- and Al-doped C3N nanosheets

The potential application of the intrinsic and extrinsic (8,0) zigzag single-walled C3N nansheets as chemical sensor for CO molecules has been investigated using density functional theory calculations. The calculation shows that the pristine sheet is a semiconductor with a HOMO-LUMO gap (Eg) of about 2.19 eV. The pristine and B-doped sheets can weakly adsorb a CO molecule with the adsorption energies of -4.8 and -4.6 kcal mol(-1), and their electronic properties are not sensitive to this molecule. By replacing a C atom with an Al atom, localized impurity states are induced under the conduction level of the sheet. The binding interaction between the CO molecule and the Al-doped sheet becomes much stronger (Ead = -17.8 kcal mol(-1)). After the adsorption of CO on the Al-dope sheet, the Eg of the sheet is significantly decreased from 1.07 to 0.73 eV. This leads to a sizable increase in the resistance of the tube. Thus, the Al-doped sheet can show the presence of CO molecules by an electronic signal because of the change in its resistance and conductivity.

A DFT study on the sensing behavior of a BC2N nanotube toward formaldehyde

We investigated the viability of using a BC2N nanotube to detect formaldehyde (H2CO) molecule by means of B3LYP and M06 density functionals. The results indicate that the molecule is weakly adsorbed on the intrinsic BC2N nanotube releasing energy of 0.8 kcal mol(-1) (at B3LYP/6-31G(d)) without significant effect on the HOMO-LUMO energy gap and electrical conductivity of the tube. Thus, H2CO cannot be detected using this intrinsic nanotube. To overcome this problem, a carbon atom of the tube wall was substituted by a Si atom. It was demonstrated that the Si-doped tube cannot only strongly adsorb the H2CO molecule, but also may effectively detect its presence because of the increase in the electric conductivity of the tube.