Comparative analysis of surface electrostatic potentials of carbon, boron/nitrogen and carbon/boron/nitrogen model nanotubes

Zigzag boron nitride nanotube functionalization as a sensor for the recognition of group IIA (Mg2+, Ca2+) metal ions, quasi-metal (Si2+, Ge2+) ions, and transition metal (Cu2+, Zn2+) ions: a computational study

CONTEXT

Boron nitride nanotubes (BNNTs) provide an exceptional and sophisticated platform for detecting metal ions with high surface area and remarkable chemical stability. Metal cations tend to bind to the surface of BNNTs, which leads to significant changes in the electrical properties of nanotubes. BNNT-based metal ion sensors have shown promising results in various applications, including water quality monitoring, biomedical research, industrial quality control, and environmental monitoring. In the present study, we have explored the electronic sensitivity of the BNNT to metal ions (Si2+, Ge2+, Cu2+, Zn2+, Mg2+, and Ca2+). The interaction between the ions with the pristine BNNT is performed in the solution phase. The results show that ion adsorption on the nanotube surface is exothermic and favorable. The density of states calculation is presented to investigate the electronic properties of the nanotube during the adsorption process. The results display that an increase in the electrical conductivity of the complexes accompanies the reduction in the energy gap. Based on the obtained data, the Si2+ and Ge2+ cations adsorbed on the BNNT with satisfactory Eg changes (%ΔE) can be promising candidates for better sensing ability.

METHOD

All calculations are conducted within the density functional theory (DFT) using the ωB97XD functional and 6-31G(d,p) basis set. The present approach incorporates the utilization of empirical atom-atom dispersion in conjunction with long-range correction. The calculations are performed using the quantum chemistry package GAMESS, and the obtained results are visualized by employing the GaussView 6.0.16 program.

Nitrogen-Doped Porous Carbon Derived from Coal for High-Performance Dual-Carbon Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) are emerging as one of the most advanced hybrid energy storage devices, however, their development is limited by the imbalance of the dynamics and capacity between the anode and cathode electrodes. Herein, anthracite was proposed as the raw material to prepare coal-based, nitrogen-doped porous carbon materials (CNPCs), together with being employed as a cathode and anode used for dual-carbon lithium-ion capacitors (DC-LICs). The prepared CNPCs exhibited a folded carbon nanosheet structure and the pores could be well regulated by changing the additional amount of g-C3N4, showing a high conductivity, abundant heteroatoms, and a large specific surface area. As expected, the optimized CNPCs (CTK-1.0) delivered a superior lithium storage capacity, which exhibited a high specific capacity of 750 mAh g-1 and maintained an excellent capacity retention rate of 97% after 800 cycles. Furthermore, DC-LICs (CTK-1.0//CTK-1.0) were assembled using the CTK-1.0 as both cathode and anode electrodes to match well in terms of internal kinetics and capacity simultaneously, which displayed a maximum energy density of 137.6 Wh kg-1 and a protracted lifetime of 3000 cycles. This work demonstrates the great potential of coal-based carbon materials for electrochemical energy storage devices and also provides a new way for the high value-added utilization of coal materials.

DNA origami nanocalipers for pH sensing at the nanoscale

A DNA origami nanocaliper is employed as a shape-resolved nanomechanical device, with pH-responsive triplex DNA integrated into the two arms. The shape transition of the nanocaliper results in a subtle difference depending on the local pH that is visible via TEM imaging, demonstrating the potential of these nanocalipers to act as a universal platform for pH sensing at the nanoscale.

Chemical reactivity and adsorption properties of pro-carbazine anti-cancer drug on gallium-doped nanotubes: a quantum chemical study

In this study, we propose new armchair single-walled nanotubes (SWNTs) for stable adsorption, increasing drug delivery performance and decreasing side effects of pro-carbazine (Pro-CB) anti-cancer in the framework of B3LYP/6-31 g*/Lanl2DZ level of theory. Indeed, doping gallium (Ga) metal in SWNTs is naturally followed by changing of geometry, increasing dipole moment, and creating one site with high reactivity in order to better adsorption of the drug molecule. Chemical reactivity descriptors show that SWNTs and Pro-CB have electrophile and nucleophile roles in interaction, respectively. More importantly, high local and dual softness in Ga-doped SWNTs indicate improvement of drug adsorption. Parallel and perpendicular complexes result from their interaction in the N and the O sites. Negative values of binding energy (E_bind) show that composed complexes are energetically stable especially in the O site in comparison with the N site. On the other hand, more negative value of the E_bind in SWCNTs shows that these nanotubes are more effective for drug adsorption than their boron nitride counterparts. Graphical abstract The Ga dopping results in reducing of HOMO-LUMO gap and increasing charge transfer between SWNTs and Pro-CB, and formation better complex, especially SWCNT.

Chemical reactivity and adsorption properties of pro-carbazine anti-cancer drug on gallium-doped nanotubes: a quantum chemical study

In this study, we propose new armchair single-walled nanotubes (SWNTs) for stable adsorption, increasing drug delivery performance and decreasing side effects of pro-carbazine (Pro-CB) anti-cancer in the framework of B3LYP/6-31 g*/Lanl2DZ level of theory. Indeed, doping gallium (Ga) metal in SWNTs is naturally followed by changing of geometry, increasing dipole moment, and creating one site with high reactivity in order to better adsorption of the drug molecule. Chemical reactivity descriptors show that SWNTs and Pro-CB have electrophile and nucleophile roles in interaction, respectively. More importantly, high local and dual softness in Ga-doped SWNTs indicate improvement of drug adsorption. Parallel and perpendicular complexes result from their interaction in the N and the O sites. Negative values of binding energy (E_bind) show that composed complexes are energetically stable especially in the O site in comparison with the N site. On the other hand, more negative value of the E_bind in SWCNTs shows that these nanotubes are more effective for drug adsorption than their boron nitride counterparts. Graphical abstract The Ga dopping results in reducing of HOMO-LUMO gap and increasing charge transfer between SWNTs and Pro-CB, and formation better complex, especially SWCNT.

Nucleotide conjugated (ZnO)3 cluster: Interaction and optical characteristics using TDDFT

Binding of four DNA nucleotide units with (ZnO)₃ cluster in an aqueous phase has been investigated using density functional theory (DFT) and time dependent-density functional theory (TDDFT) method and the stability order for (ZnO)₃-nucleobases/sugar/phosphate systems is predicted as phosphate > C > A > S > T ∼ G. The order of binding energy for (ZnO)₃-nucleotide hybrid systems is observed to be (ZnO)₃ + nuc-C ˃ (ZnO)₃ + nuc-A ˃ (ZnO)₃ + nuc-G ˃ (ZnO)₃ + nuc-T. The binding of nucleotide units with the cluster has been explained on the basis of molecular electrostatic potential (MEP) plots, hydrogen bonding, glycosidic torsion angles, density of state (DOS) plots. The photophysical properties of (ZnO)₃-nucleotide complexes have been studied using TDDFT approach. Among all (ZnO)₃-nucleotide complexes, the absorption spectra of (ZnO)₃ + nuc-A and (ZnO)₃ + nuc-C complexes are seen to undergo red shift with respect to their bare nucleotide units that would be useful in the optical sensing of the respective nucleotides of DNA. It is interesting to note that binding of the nucleotide unit with the cluster makes it fluorescent, the study reports the fluorescence activity of (ZnO)₃ + nuc-T complex.

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.

Functionalization of single-walled (n,0) carbon and boron nitride nanotubes by carbonyl derivatives (n = 5, 6): a DFT study

By using density functional theory calculations, the chemical functionalization of finite-sized (5,0) and (6,0) carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) by different carbonyl derivatives –COX (X = H, CH3, OCH3, OH, and NH2) is studied in terms of geometrical and electronic structure properties. Also, the benefits of local reactivity descriptors is studied to characterize the reactive sites of the external surface of the tubes. These local reactivity descriptors include the electrostatic potential VS(r) and average local ionization energy ĪS(r) on the surfaces of these nanotubes. The estimated ĪS(r) values show that the functionalized CNTs tend to activate the surface toward electrophilic/radical attack. Results show that the chemical functionalization of CNTs leads to the reduction of VS(r) values and therefore enhances the surface reactivity. On the other hand, BNNTs resist chemical functionalization due to the negligible decrease in the VS,min and ĪS,min values. Generally, in contrast to BNNTs, the chemical functionalization of CNTs can considerably improve their surface reactivity. To verify the surface reactivity pattern based on the chosen reactivity descriptors, the reaction energies for the interaction of an H + ion or hydrogen radical with external surface of the functionalized CNTs and BNNTs are calculated. A general feature of all studied systems is that stronger potentials are associated with regions of higher curvature.

An ab initio study on tunability of σ-hole interactions in XHS:PH2Y and XH2P:SHY complexes (X = F, Cl, Br; Y = H, OH, OCH3, CH3, C2H5, and NH2)

Quantum chemical calculations are performed to investigate the tunability of σ-hole interactions in chalcogen-bonded XHS:PH2Y and pnicogen-bonded XH2P:SHY complexes, where X  =  F, Cl, Br and Y  =  H, OH, OCH3, CH3, C2H5, NH2. The formation of these binary complexes can be understood in terms of molecular electrostatic potentials (MEPs), considering the P and S atoms as an electron acceptor or an electron donor in the chalcogen and pnicogen bonds. The strength of the XHS:PH2Y and XH2P:SHY complexes for a given Y increases as follows: X = Br < Cl < F. In addition, an acceptable linear relationship is found between the interaction energies and the magnitudes of the product of most positive and negative MEPs. This finding along with the electron density difference maps provides a clear picture of the electrostatic nature of the interactions in the XHS:PH2Y and XH2P:SHY complexes. The calculated spin-spin coupling constants across the chalcogen bond interactions in the XHS:PH2Y complexes display a quadratic dependence with the P···S binding distance.

A theoretical study on surface reactivity of fluorinated (n,0) and (n,n) carbon nanotubes (n = 3–6)

Density functional theory calculations are performed to investigate the surface reactivity of pristine as well as fluorine-terminated zigzag (n,0) and armchair (n,n) carbon nanotubes (n = 3–6). The properties determined include the electrostatic potential V(r) and average local ionization energy Ī(r) on the surfaces of the investigated tubes. A general feature of all of the systems studied is that stronger potentials are associated with regions of higher curvature. The results indicate that both V(r) and Ī(r) detect the effects of fluorine-terminated regions in which significant effects are observed for those atoms in the vicinity of the fluorine-terminated regions. Comparison with the Ī(r) of the pristine nanotube indicates correctly that in the fluorine-terminated models, the fluorine atoms tend to deactivate the surface toward electrophilic/radical attack.

Nitrous oxide adsorption on pristine and Si-doped AlN nanotubes

Using density functional theory, we studied the adsorption of an N(2)O molecule onto pristine and Si-doped AlN nanotubes in terms of energetic, geometric, and electronic properties. The N(2)O is weakly adsorbed onto the pristine tube, releasing energies in the range of -1.1 to -5.7 kcal mol(-1). The electronic properties of the pristine tube are not influenced by the adsorption process. The N(2)O molecule is predicted to strongly interact with the Si-doped tube in such a way that its oxygen atom diffuses into the tube wall, releasing an N(2) molecule. The energy of this reaction is calculated to be about -103.6 kcal mol(-1), and the electronic properties of the Si-doped tube are slightly altered.

Adsorption of CO molecule on AlN nanotubes by parallel electric field

The behavior of the carbon monoxide (CO) adsorbed on the external surface of H-capped (6,0) zigzag single-walled aluminum nitride nanotube (AlNNT) was studied using parallel and transverse electric field (strengths 0-140 × 10(-4) a.u.) and density functional calculations. The calculated adsorption energies of the CO/AlNNT complex increased with increasing parallel electric field intensity, whereas the adsorption energy values at the applied transverse electric field show a significant reverse trend. The calculated adsorption energies of the complex at the applied parallel electric field strengths increased gradually from -0.42 eV at zero field strength to -0.80 eV at a field strength of 140 × 10(-4) a.u. The considerable changes in the adsorption energies and energy gap values generated by the applied parallel electric field strengths show the high sensitivity of the electronic properties of AlNNT towards the adsorption of CO on its surface. Analysis of structural parameters indicates that the nanotube is resistant to external electric field strengths. The dipole moment variations in the complex show a significant change in the presence of parallel and transverse electric fields, which results in much stronger interactions at higher electric field strengths. Additionally, the natural bond orbital charges, quantum molecular descriptors, and molecular orbital energies of the complex show that the nanotube can absorb CO molecule in its pristine form at a high applied parallel electric field, and that the nanotube can be used as a CO storage medium.

Electronic sensor for sulfide dioxide based on AlN nanotubes: a computational study

Single-walled aluminum nitride nanotubes (AlNNTs) are introduced as an electronic sensor for detection of sulfur dioxide (SO₂) molecules based on density functional theory calculations. The proposed sensor benefits from several advantages including high sensitivity: HOMO-LUMO energy gap of the AlNNT is appreciably sensitive toward the presence of SO₂ so that it decreases from 4.11 eV in the pristine tube to 1.01 eV in the SO₂-adsorbed form, pristine application: this nanotube can detect the SO₂ molecule in its pristine type without manipulating its structure through doping, chemical functionalization, making defect, etc., short recovery time: the adsorption energy of SO₂ molecule is not so large to hinder the recovery of AlNNTs and therefore the sensor will possess short recovery times, and good selectivity: the tube can selectively detect the SO₂ molecule in the presence of several molecules such as H₂O, CO, NH₃, HCOH, CO₂, N₂, and H₂.

NMR and NQR study of Si-doped (6,0) zigzag single-walled aluminum nitride nanotube as n or P-semiconductors

Density functional theory (DFT) calculations were performed to investigate the electronic structure properties of pristine and Si-doped aluminum nitride nanotubes as n or P-semiconductors at the B3LYP/6-31G* level of theory in order to evaluate the influence of Si-doped in the (6,0) zigzag AlNNTs. We extended the DFT calculation to predict the electronic structure properties of Si-doped aluminum nitride nanotubes, which are very important for production of solid-state devices and other applications. To this aim, pristine and Si-doped AlNNT structures in two models (Si(N) and Si(Al)) were optimized, and then the electronic properties, the isotropic (CS(I)) and anisotropic (CS(A)) chemical shielding parameters for the sites of various (27)Al and (14)N atoms, NQR parameters for the sites of various of (27)Al and (14)N atoms, and quantum molecular descriptors were calculated in the optimized structures. The optimized structures, the electronic properties, NMR and NQR parameters, and quantum molecular descriptors for the Si(N) and Si(Al) models show that the Si(N) model is a more reactive material than the pristine or Si(Al) model.

Cation-π interaction of alkali metal ions with C24 fullerene: a DFT study

Using first principle calculations, we investigated cation-π interactions between alkali cations (Li(+), Na(+), and K(+)) and pristine C(24) or doped fullerenes of BC(23), and NC(23). The most suitable adsorption site is found to be atop the center of a six-membered ring of the exterior surface of C(24) molecule. Interaction energies of these cations decreased in the order: Li(+) > Na(+) > K(+), with values of -31.82, -22.36, and -15.68 kcal mol(-1), respectively. It was shown that the interaction energies are increased and decreased by impurity doping of B and N atoms in adjacent wall of adsorption site, depending on electron donating or receptivity of the doping atoms.

A donor-nanotube paradigm for nonlinear optical materials

Studies of the nonlinear electronic response of donor/acceptor substituted nanotubes suggest a behavior that is both surprising and qualitatively distinct from that in conventional conjugated organic species. We find that the carbon nanotubes serve as both electronic bridges and acceptors, leading to a donor-nanotube paradigm for the effective design of large first hyperpolarizabilities. We also find that tuning the donor orientation, relative to the nanotube, can significantly enhance the first hyperpolarizability.