Carbon nanotube functionalization with carboxylic derivatives: a DFT study

Ultrasonically Driven Structural Evolution of Bimetallic Heterostructures for Construction of an ElectroTrace Analyzer

Bimetallic heterostructure materials (BHMs) have garnered significant attention due to their exceptional synergistic electrocatalytic properties. However, challenges persist in developing precise, scalable synthetic methods and understanding their underlying mechanisms. Here, we develop an ultrasonic-assisted anchoring strategy to fabricate BHMs on multiwalled carbon nanotubes (MWCNTs). First, a multifunctional polyaromatic organic receptor (MPOR), featuring urea and imine functional groups, was physisorbed onto MWCNTs (MWCNTs@MPOR), inducing structural coiling. Subsequent interaction with Hg metal ions led to the reorganization of MWCNTs (MWCNTs@MPOR/Hg), followed by ultrasonic treatment that facilitated Mn ion anchoring at the free imine sites, yielding the final BHMs MWCNTs@MPOR/Hg/Mn. Notably, the structural changes and nature of interactions were thoroughly studied by density functional theory (DFT) simulations. Experimental results and first-principles calculations revealed remarkably enhanced electrochemical activity with a charge transfer of -0.179e in MWCNTs@MPOR/Hg/Mn. Further, we introduced a portable "ElectroTrace Analyzer" based on MWCNTs@MPOR/Hg/Mn for real-time detection and quantification of atrazine (herbicide). Our ultrasonically assisted strategy for BHM synthesis offers a fascinating avenue for the advanced development of useful BHMs for real-world applications.

Electrically enhanced adsorption efficiency of aluminum nitride nanotube for sulfate ion removal from water

Herein, the adsorption performance of sulfate ion in water on aluminum nitride nanotube(AlNNT) under the influence of an electric field was investigated using the density functional theory (DFT) calculation method. The model structure stability, adsorption energy, electronic and thermodynamic properties of sulfate ion adsorbed on the surface of AlNNT were studied. The calculation results indicate that sulfate ion reacts with multi-atoms on the surface of AlNNT, forming ionic bonds and undergoing chemical adsorption. As the electric field intensity increases, the adsorption energy and the transfer of electrons from sulfate ion to AlNNT increase, leading to a higher degree of hybridization of atomic orbitals and enhanced multi-atom interactions. Additionally, the thermodynamic data suggests that the adsorption between sulfate ion and AlNNT under electric field can occur spontaneously, the process of which is exothermic. The results of present study are expected to propose a novel method for separation and removal of sulfate pollutants from water.

Carboxyl Functionalization of N-MWCNTs with Stone-Wales Defects and Possibility of HIF-1α Wave-Diffusive Delivery

Nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) are widely used for drug delivery. One of the main challenges is to clarify their interaction with hypoxia-inducible factor 1 alpha (HIF-1α), the lack of which leads to oncological and cardiovascular diseases. In the presented study, N-MWCNTs were synthesized by catalytic chemical vapor deposition and irradiated with argon ions. Their chemical state, local structure, interfaces, Stone-Wales defects, and doping with nitrogen were analyzed by high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Using experimental data, supercells of functionalized N-MWCNTs with an oxygen content of 2.7, 4 and 6 at. % in carboxyl groups were built by quantum chemical methods. Our analysis by the self-consistent charge density functional tight-binding (SCC DFTB) method shows that a key role in the functionalization of CNTs with carboxyl groups belongs to Stone-Wales defects. The results of research in the decoration of CNTs with HIF-1α demonstrate the possibility of wave-diffusion drug delivery. The nature of hybridization and relaxation determines the mechanism of oxygen regulation with HIF-1α molecules, namely, by OH-(OH-C) and OH-(O=C) chemical bonds. The concentration dependence of drug release in the diffusion mode suggests that the best pattern for drug delivery is provided by the tube with a carboxylic oxygen content of 6 at. %.

Structural Stability and Electronic Properties of Boron Phosphide Nanotubes: A Density Functional Theory Perspective

Based on the Density Functional Theory (DFT) calculations, we analyze the structural and electronic properties of boron phosphide nanotubes (BPNTs) as functions of chirality. The DFT calculations are performed using the M06-2X method in conjunction with the 6-31G(d) divided valence basis set. All nanostructures, (n,0) BPNT (n = 5–8, 10, 12, 14) and (n,n) BPNT (n = 3–11), were optimized minimizing the total energy, assuming a non-magnetic nature and a total charge neutrality. Results show that the BPNT diameter size increases linearly with the chiral index “n” for both chiralities. According to the global molecular descriptors, the (3,3) BPNT is the most stable structure provided that it shows the largest global hardness value. The low chirality (5,0) BPNT has a strong electrophilic character, and it is the most conductive system due to the small |HOMO-LUMO| energy gap. The chemical potential and electrophilicity index in the zigzag-type BPNTs show remarkable chirality-dependent behavior. The increase in diameter/chirality causes a gradual decrease in the |HOMO-LUMO| energy gap for the zigzag BPNTs; however, in the armchair-type BPNTs, a phase transition is generated from a semiconductor to a conductor system. Therefore, the nanostructures investigated in this work may be suggested for both electrical and biophysical applications.

Electrically Conductive Silicone-Based Nanocomposites Incorporated with Carbon Nanotubes and Silver Nanowires for Stretchable Electrodes

Stretchable electrode materials have attracted great attention as next-generation electronic materials because of their ability to maintain intrinsic properties with rare damage when undergoing repetitive deformations, such as folding, twisting, and stretching. In this study, an electrically conductive PDMS nanocomposite was manufactured by combining the hybrid nanofillers of carbon nanotubes (CNTs) and silver nanowires (AgNWs). The amphiphilic isopropyl alcohol molecules temporarily adhered simultaneously to the hydrophobic CNT and hydrophilic AgNW surfaces, thereby improving the dispersity. As the CNT/AgNW ratio (wt %/wt %) decreased under the constant nanofiller content, the tensile modulus decreased and the elongation at break increased owing to the poor interaction between the AgNWs and matrix. The shear storage moduli of all nanocomposites were higher than the loss moduli, indicating the elastic behavior with a cross-linked network. The electrical conductivities of the nanocomposite containing the hybrid nanofillers were superior to those of the nanocomposite containing either CNT or AgNW at the same filler content (4 wt %). The hybrid nanofillers were rearranged and deformed by 5000 cyclic strain tests, relaxing the PDMS matrix chain and weakening the interfacial bonding. However, the elastic behavior was maintained. The dynamic electrical conductivities gradually increased under the cyclic strain tests due to the rearrangement and tunneling effect of the nanofillers. The highest dynamic electrical conductivity (10 S/m) was obtained for the nanocomposite consisting of 2 wt % of CNTs and 2 wt % of AgNWs.

The adsorption of cathinone drug on the platinum decorated silicon carbide nanosheets: DFT studies

Cathinone (CTN), classified as stimulants, is one of the psychoactive drugs. Although the sale of CTN was controlled by international drug laws, it was still sold on the internet, and its overdose caused many deaths worldwide. As chemical sensors, two-dimensional (2D) nanomaterials have drawn attention to be used in various biological molecules. In the current study, the sensing characteristics of the intrinsic SiC monolayer (SiCM) and its Pt-decorated state (Pt@SiCM) were scrutinized toward the CTN drug by utilizing density functional theory (DFT) calculations. It was illustrated that the SiCM sensing response to CTN is insignificant (~ 10.6 at 298 K) due to the weak interaction with the adsorption energy of -0.25 eV. After the decoration of Pt on the SiCM, it was adsorbed above a hexagonal ring, which formed an η⁶-Pt half-sandwich and the adsorption energy was -3.62 eV. It was found that the Pt@SiCM strongly adsorbed CTN and the adsorption energy was -1.60 eV. Therefore, Pt-decoration augmented the SiCM sensing response to CTN from 10.3 to 716.6. The recovery time obtained for the CTN desorption from the Pt@SiCM surface was 12.7 s, which was short. It was concluded that Pt-decoration makes the SiCM a favorable candidate for CTN identification.

Theoretical analysis of the structural and electronic properties of the interaction of boron nitride diamantane nanocrystal with the drug hydroxyurea as an anticancer drug

The density functional theory calculations with hybrid B3LYP/6-31G(d,p) basis sets have been used to examine the structural and electronic properties of boron nitride (BN) diamantane interacted with the drug hydroxyurea (HU) as an anticancer drug. The findings have been shown that there is a decrease in the total energy after combining the drug with diamantane. The energy levels of HOMO and LUMO analyses indicate that the value of HOMO energy increased slightly, while the value of LUMO energy decreased significantly in these systems in the HU/BN diamantane. In addition, the decreasing of the energy gap between HOMO and LUMO confirms a strong bond between the drug hydroxyurea and BN diamantane. Finally, the drug's stability and reactivity with BN diamantane were investigated by measuring chemical reaction characteristics such as chemical potential, electron affinity, global hardness, and electrophilicity index. As a result, the nanocrystal of BN diamantane can be considered a vector for the delivery of anticancer drugs within biological systems.

Predicting whether aromatic molecules would prefer to enter a carbon nanotube: A density functional theory study

The interaction of a carbon nanotube (CNT) with various aromatic molecules, such as aniline, benzophenone, and diphenylamine, was studied using density functional theory able to compute intermolecular weak interactions (B3LYP-D3). CNTs of varying lengths were used, such as 4-CNT, 6-CNT, and 8-CNT (the numbers denoting relative lengths), with the lengths being chosen appropriately to save computation times. All aromatic molecules were found to exhibit strong intermolecular binding energies with the inner surface of the CNT, rather than the outer surface. Hydrogen bonding between two aromatic molecules that include N and O atoms is shown to further stabilize the intermolecular adsorption process. Therefore, when benzophenone and diphenylamine were simultaneously allowed to interact with a CNT, the aromatic molecules were expected to preferably enter the CNT. Furthermore, additional calculations of the intermolecular adsorption energy for aniline adsorbed on a graphene surface showed that the concavity of graphene-like carbon sheet is in proportion to the intermolecular binding energy between the graphene-like carbon sheet and the aromatic molecule.

Selective detection of cyanogen halides by BN nanocluster: a DFT study

The electronic sensitivity and adsorption behavior toward cyanogen halides (X–CN; X = F, Cl, and Br) of a B₁₂N₁₂ nanocluster were investigated by means of density functional theory calculations. The X-head of these molecules was predicted to interact weakly with the BN cluster because of the positive σ-hole on the electronic potential surface of halogens. The X–CN molecules interact somewhat strongly with the boron atoms of the cluster via the N-head, which is accompanied by a large charge transfer from the X–CN to the cluster. The change in enthalpy upon the adsorption process (at room temperature and 1 atm) is about −19.2, −23.4, and −30.5 kJ mol⁻¹ for X = F, Cl, and Br, respectively. The LUMO level of the BN cluster is largely stabilized after the adsorption process, and the HOMO–LUMO gap is significantly decreased. Thus, the electrical conductivity of the cluster is increased, and an electrical signal is generated that can help to detect these molecules. By increasing the atomic number of X, the signal will increase, which makes the sensor selective for cyanogen halides. Also, it was indicated that the B₁₂N₁₂ nanocluster benefits from a short recovery time as a sensor.

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.

N-H bond cleavage of ammonia on graphene-like B36 borophene: DFT studies

Ammonia N-H bond cleavage at metal-free substrates has attracted great attention because of its industrial importance. Here, we investigate the dissociative adsorption of ammonia onto the surface of a B36 borophene sheet by means of density functional theory calculations. We show that the N-H bond may be broken at the edges of B36 even at room temperature, regarding the small energy barrier of 14.1-19.3 kcal mol(-1) at different levels of theory, and more negative Gibbs free energy change. Unlike basis set size, the kind of exchange correlation functional significantly affects the electronic properties of the studied systems. Also, by increasing the percentage of Hartree Fock (HF) exchange of density functionals, the activation and adsorption energies are lowered. A linear relationship between the highest occupied molecular orbital or lowest unoccupied molecular orbital of B36 borophene and the %HF exchange of functionals is predicted. Our work reveals that pure whole boron nanosheets may be promising metal-free materials in N-H bond cleavage, which would raise the potential application of these sheets.

Calculation of Raman parameters of real-size zigzag (n, 0) single-walled carbon nanotubes using finite-size models

Structural and selected Raman features of real-size single-walled carbon nanotubes (SWCNTs) were studied using finite-size pristine SWCNT models at the DFT level.

Functionalization of the pristine and stone-wales defected BC3 graphenes with pyrene

The functionalization of pristine and Stone-Wales defected BC3 nanosheets with a pyrene molecule was investigated using density functional theory. Frontier molecular analysis shows that the main interaction is π-π stacking, releasing energies in the range of 143.6 to 169.1 kJ mol(-1). We predicted that after the functionalization process, the electrical conductance of the pristine sheet may be increased. Also, it modifies the work function of the pristine sheet and, as a consequence, its field-emission current densities may significantly enhance. However, the pyrene functionalization results in little change in the electronic properties of the defected sheet.