Green in situ synthesis of sandwich-like W-bridged siligraphene (g-SiC@WC@g-SiC) heterostructure from Saccharum Ravennae gum for ultrahigh-rate photodegradation of acetaminophen.

Herein, the sandwich-like W-bridged siligraphene (W/g-SiC) as a heterojunction of WC and siligraphene nanosheets have been first accomplished via a simple green synthesis using Saccharum Ravennae gum as a natural Si and W sources and gelatin as a natural C and N sources. In a magnesiothermic process, Si and C atoms bond together and form a graphene-like structure where half of the C atoms are replaced by Si atoms. The presence of W in the natural precursor creates a W-doped siligraphene structure. Tungsten in the form of carbide (WC) creates a heterojunction with g-SiC, which reduces the bandgap. According to the experimental and computational data, the proposed structure of W/g-SiC was predicted by replacing the W atoms with Si atoms and bonding with C atoms in the siligraphene structure. The W-C bond in this structure is elongated and the W atom comes out of the siligraphene sheet and is placed between two siligraphene layers to interact with three carbons from the next layer. Under visible light irradiation, holes are generated on the g-SiC layers and electrons in the WC interlayer, which makes it a highly efficient photocatalyst with ultrafast charge separation and active surface for the removal of Acetaminophen.

Electrodeposition of CoxNiVyOz Ternary Nanopetals on Bare and rGO-Coated Nickel Foam for High-Performance Supercapacitor Application.

We report a simple strategy to grow a novel cobalt nickel vanadium oxide (CoxNiVyOz) nanocomposite on bare and reduced-graphene-oxide (rGO)-coated nickel foam (Ni foam) substrates. In this way, the synthesized graphene oxide is coated on Ni foam, and reduced electrochemically with a negative voltage to prepare a more conductive rGO-coated Ni foam substrate. The fabricated electrodes were characterized with a field-emission scanning electron microscope (FESEM), energy-dispersive X-ray spectra (EDX), X-ray photoelectron spectra (XPS), and Fourier-transform infrared (FTIR) spectra. The electrochemical performance of these CoxNiVyOz-based electrode materials deposited on rGO-coated Ni foam substrate exhibited superior specific capacitance 701.08 F/g, which is more than twice that of a sample coated on bare Ni foam (300.31 F/g) under the same experimental conditions at current density 2 A/g. Our work highlights the effect of covering the Ni foam surface with a rGO film to expedite the specific capacity of the supercapacitors. Despite the slightly decreased stability of a CoxNiVyOz-based electrode coated on a Ni foam@rGO substrate, the facile synthesis, large specific capacitance, and preservation of 92% of the initial capacitance, even after running 5500 cyclic voltammetric (CV) scans, indicate that the CoxNiVyOz-based electrode is a promising candidate for high-performance energy-storage devices.

Fundamental mechanisms of hexagonal boron nitride sensing of dopamine, tryptophan, ascorbic acid, and uric acid by first-principles study.

Selectivity of dopamine (DA), uric acid (UA), and ascorbic acid (AA) is an open challenge of electrochemical sensors in the field of biosensing. In this study, two selective mechanisms for detecting DA, UA, and AA biomolecules on the pristine boron nitride nanosheets (BNNS) and functionalized BNNS with tryptophan (Trp), i.e., Trp@BNNS have been illustrated through density functional density (DFT) calculation and charge population analysis. Our findings reveal that the adsorbed biomolecules on Trp@BNNS indicate the less sensitivity factor of biomolecule separation than the functionalized biomolecules with Trp (Trp@biomolecule) adsorbed on pristine BNNS. From the calculations, strong adsorption of Trp@biomolecule on the pristine substrate corresponds to enhancing of electron charge transfer and electrical dipole moment. Our analysis is in good agreement with the previous theoretical and experimental results and suggests new pathway for electrode modification for electrochemical biosensing.

A DFT study on the potential application of pristine, B and N doped carbon nanocones in potassium-ion batteries.

Although lithium-ion batteries are broadly applied for various purposes, they suffer from safety problems, high cost, and short life. Due to widespread availability, low cost, and nontoxicity of potassium, potassium ion batteries (PIBs) can be applied instead of lithium-ion batteries. Here, dispersion-corrected B3LYP calculations were used to explore potential application of pristine carbon nanocone (CNC) as well as its B- and N-doped models in PIBs. The K cation and K atom were adsorbed onto the center of the apex ring of CNC, and the energies of adsorption were - 19.3 and - 9.0 kcal/mol. The CNC creates a cell voltage of 0.44 V as an anode material which is very small. We showed that substituting some C atoms of CNC by the electron-rich N atoms makes the nanocone more appropriate for application in the PIBs, while B-doping meaningfully decreases the cell voltage. The cell voltage created by the considered nanocones in the PIBs has the following order: N-CNC (~ 1.24 V) > CNC (~ 0.45 V) > > B-CNC (~ 0.24 V). This work illustrated that the N-CNC may be a promising electrode material for PIBs.

The influence of Stone-Wales defects in nanographene on the performance of Na-ion batteries.

The effect of the Stone-Wales (SW) defect on the energetic, structural, electronic properties of Na/Na+ adsorption on the Hexa-peri-hexabenzocoronene (HBC) nanographene is investigated using density functional theory calculations. We showed that two kinds of SW defects can be generated in the structure of HBC, and the defected sheets are less stable than the intrinsic HBC by about 63.2-65.3 kcal/mol. The heptagonal ring of SW defect is the most favorable site for the Na and Na+ adsorption and the adsorption energies increase from -0.8 and -33.2 kcal/mol on the intrinsic HBC to -16.7 and -39.3 kcal/mol on the SW-HBC, respectively. The predicted energy barrier for an Na atom to move from a heptagonal ring to another one in the SW-HBC is about 4.9 kcal/mol, indicating a high ion mobility compared to the pristine HBC. The SW defect increases the Na diffusion coefficient from 3.46 × 10-11 to 2.83 × 10-6 cm2/s. Although the SW defect increases the ion mobility, it has an undesirable effect on the cell voltage, if a HBC nanographene is used in the anode of Na-ion batteries.

Electro-Optical Properties of Monolayer and Bilayer Pentagonal BN: First Principles Study.

Two-dimensional hexagonal boron nitride (hBN) is an insulator with polar covalent B-N bonds. Monolayer and bilayer pentagonal BN emerge as an optoelectronic material, which can be used in photo-based devices such as photodetectors and photocatalysis. Herein, we implement spin polarized electron density calculations to extract electronic/optical properties of mono- and bilayer pentagonal BN structures, labeled as B 2 N 4 , B 3 N 3 , and B 4 N 2 . Unlike the insulating hBN, the pentagonal BN exhibits metallic or semiconducting behavior, depending on the detailed pentagonal structures. The origin of the metallicity is attributed to the delocalized boron (B) 2p electrons, which has been verified by electron localized function and electronic band structure as well as density of states. Interestingly, all 3D networks of different bilayer pentagonal BN are dynamically stable unlike 2D structures, whose monolayer B 4 N 2 is unstable. These 3D materials retain their metallic and semiconductor nature. Our findings of the optical properties indicate that pentagonal BN has a visible absorption peak that is suitable for photovoltaic application. Metallic behavior of pentagonal BN has a particular potential for thin-film based devices and nanomaterial engineering.

Phase transition and mechanical properties of cesium bismuth silver halide double perovskites (Cs2AgBiX6, X = Cl, Br, I): a DFT approach.

Double perovskite-based silver and bismuth Cs2AgBiX6 (X = Cl, Br, I) have shown a bright future for the development of low-risk photovoltaic devices due to their high stability and non-toxicity of their elements, unlike Pb-based perovskites. Despite the great focus on the optoelectronic properties of Cs2AgBiX6 double perovskites, there are limited studies on the behavior of their structural properties. Herein, we carefully examined the cubic structure of Cs2AgBiX6 double perovskites, identifying a pseudo-cubic (ps-cubic) phase, which is similar to the initial cubic phase. The observed pseudo-cubic phase is more consistent with previous experimental results demonstrating higher elastic properties, which are useful for designing optoelectronic devices.

Hydrogenated Ψ-graphene as an ultraviolet optomechanical sensor.

PSI (ψ)-graphene is a dynamically and thermally stable two-dimensional (2D) allotrope of carbon composed of 5-6-7 carbon rings. Herein, we study the opto/mechanical behavior of two graphene allotropes, Ψ-graphene and its hydrogenated form, Ψ-graphane under uniaxial and biaxial strain using density functional theory (DFT) calculations. We calculated the elastic constants and second Piola-Kirchhoff (PK2) stresses, in which both nanostructures indicate a similar elasticity behavior to graphene. Also, the plasmonic behavior of these structures in response to various strains has been studied. As a result, plasmonic peaks varied up to about 2 eV under strain. Our findings reveal that these two structures have a large peak in the ultraviolet (UV) region and can be tuned by different applied strain. In addition, Ψ-graphene has smaller peaks in the IR and UV regions. Therefore, both Ψ-graphene and Ψ-graphane can be used as UV optomechanical sensors, whereas Ψ-graphene could be used as an infrared (IR) and visible sensor.

Boron nitride nanochannels encapsulating a water/heavy water layer for energy applications.

Water interaction and transport through nanochannels of two-dimensional (2D) nanomaterials hold great promises in several applications including separation, energy harvesting and drug delivery. However, the fundamental underpinning of the electronic phenomena at the interface of such systems is poorly understood. Inspired by recent experiments, herein, we focus on water/heavy water in boron nitride (BN) nanochannels - as a model system - and report a series of ab initio based density functional theory (DFT) calculations on correlating the stability of adsorption and interfacial properties, decoding various synergies in the complex interfacial interactions of water encapsulated in BN nanocapillaries. We provide a comparison of phonon vibrational modes of water and heavy water (D2O) captured in bilayer BN (BLBN) to compare their mobility and group speed as a key factor for separation mechanisms. This finding, combined with the fundamental insights into the nature of the interfacial properties, provides key hypotheses for the design of nanochannels.

First-Principles Study of Water Nanotubes Captured Inside Carbon/Boron Nitride Nanotubes.

Water confined to nanopores such as carbon nanotubes (CNTs) exhibits different states, enabling the study of solidlike water nanotubes (WNTs) and the potential application of their properties due to confined effects. Herein, we report the interfacial interaction and particular stabilized boundaries of confined WNTs within CNTs and boron nitride nanotubes (BNNTs) using first-principles calculations. We demonstrate that the intermolecular potential of nanotube walls exerts diameter-dependent additive or subtractive van der Waals (vdW) pressure on the WNTs, altering the phase boundaries. Our results reveal that the most stable WNT@CNT is associated with a CNT diameter of 10.5 Å. By correlating the stability of WNTs with interfacial properties such as the vdW pressure and vibrational phonon modes of confined WNTs, we decode and compare various synergies in water interaction and stabilized states within the CNTs and BNNTs, including interfacial properties of WNT@BNNTs that are more significant than those of WNT@CNTs. Our results suggest that the transition of a water tube to an ice tube is strongly dependent on the diameter of the confining CNT or BNNT, providing new insights on leveraging the interfacial interaction mechanism of confined WNTs and their potential application for fabricating nanochannels and nanocapacitors.

Experimental and Theoretical Study of Enhanced Photocatalytic Activity of Mg-Doped ZnO NPs and ZnO/rGO Nanocomposites.

A systematic experimental and theoretical study of the origin of the enhanced photocatalytic performance of Mg-doped ZnO nanoparticles (NPs) and Mg-doped ZnO/reduced graphene oxide (rGO) nanocomposites has been performed. In addition to Mg, Cd was chosen as a doping material for the bandgap engineering of ZnO NPs, and its effects were compared with that of Mg in the photocatalytic performance of ZnO nanostructures. The experimental results revealed that Mg, as a doping material, recognizably ameliorates the photocatalytic performance of ZnO NPs and ZnO/graphene nanocomposites. Transmission electron microscopy (TEM) images showed that the Mg-doped and Cd-doped ZnO NPs had the same size. The optical properties of the samples indicated that Cd narrowed the bandgap, whereas Mg widened the bandgap of the ZnO NPs and the oxygen vacancy concentration was similar for both samples. Based on the experimental results, the narrowing of the bandgap, the particle size, and the oxygen vacancy did not enhance the photocatalytic performance. However, Brunauer-Emmett-Teller (BET) and Barret-Joyner-Halenda (BJH) models showed that Mg caused increased textural properties of the samples, whereas rGO played an opposite role. A theoretical study, conducted by using DFT methods, showed that the improvement in the photocatalytic performance of Mg-doped ZnO NPs was due to a higher electron transfer from the Mg-doped ZnO NPs to the dye molecules compared with pristine ZnO and Cd-doped ZnO NPs. Moreover, according to the experimental results, along with Mg, graphene also played an important role in the photocatalytic performance of ZnO.

Electrochemical and DFT study of an anticancer and active anthelmintic drug at carbon nanostructured modified electrode.

The electrochemical response of mebendazole (Meb), an anticancer and effective anthelmintic drug, was investigated using two different carbon nanostructured modified glassy carbon electrodes (GCE). Although, compared to unmodified GCE, both prepared modified electrodes improved the voltammetric response of Meb, the carbon nanotubes (CNTs) modified GCE showed higher sensitivity and stability. Therefore, the CNTs-GCE was chosen as a promising candidate for the further studies. At first, the electrochemical behavior of Meb was studied by cyclic voltammetry and differential pulse and square wave voltammetry. A one step reversible, pH-dependent and adsorption-controlled process was revealed for electro-oxidation of Meb. A possible mechanism for the electrochemical oxidation of Meb was proposed. In addition, electronic structure, adsorption energy, band gap, type of interaction and stable configuration of Meb on the surface of functionalized carbon nanotubes were studied by using density functional theory (DFT). Obtained results revealed that Meb is weakly physisorbed on the CNTs and that the electronic properties of the CNTs are not significantly changed. Notably, CNTs could be considered as a suitable modifier for preparation of the modified electrode for Meb analysis. Then, the experimental parameters affecting the electrochemical response of Meb were optimized. Under optimal conditions, high sensitivity (b(Meb)=dIp,a(Meb)/d[Meb]=19.65µAµM(-1)), a low detection limit (LOD (Meb)=19nM) and a wide linear dynamic range (0.06-3µM) was resulted for the voltammetric quantification of Meb.

Theoretical prediction of silicene as a new candidate for the anode of lithium-ion batteries.

Using density functional theory calculations, we determine the band structure and DOS of graphene and silicene supercell models. We also study the adsorption mechanism of Li metal atoms and Li-ions onto free-standing silicene (buckled, θ = 101.7°) and compare the results with those of graphene. In contrast to graphene, interactions between Li metal atoms and Li-ions with the silicene surface are quite strong due to its highly reactive buckled hexagonal structure. As a consequence of structural properties the adsorption height, the most stable adsorption site and energy barrier against Li diffusion are also discussed here to outline the prospects of using silicene in electronic devices such as Li ion batteries (LiBs), hydrogen storage and molecular machines. However, in most LiBs, graphene layers are used as anode electrodes. Here, it is shown that graphene has very limited Li storage capacity and low surface area than silicene. As our models are in good agreement with previous predictions, this finding presents a possible avenue for creating better anode materials that can replace graphene for higher capacity and better cycling performance of LiBs.

Theoretical study on the functionalization of BC2N nanotube with amino groups.

Using density functional theory calculations, we investigated properties of a functionalized BC2N nanotube with NH3 and five other NH2-X molecules in which one of the hydrogen atoms of NH3 is substituted by X = -CH3, -CH2CH3, -COOH, -CH2COOH and -CH2CN functional groups. It was found that NH3 can be preferentially adsorbed on top of the boron atom, with adsorption energy of -12.0 kcal mol(-1). The trend of adsorption-energy change can be correlated with the trend of relative electron-withdrawing or -donating capability of the functional groups. The adsorption energies are calculated to be in the range of -1.8 to -14.2 kcal mol(-1), and their relative magnitude order is found as follows: H2N(CH2CH3) > H2N(CH3) > NH3 > H2N(CH2COOH) > H2N(CH2CN) > H2N(COOH). Overall, the functionalization of BC2N nanotube with the amino groups results in little change in its electronic properties. The preservation of electronic properties of BC2N coupled with the enhancement of solubility renders their chemical modification with either NH3 or amino functional groups to be a way for the purification of BC2N nanotubes.

Sensing behavior of Al-rich AlN nanotube toward hydrogen cyanide.

In order to explore a sensor for detection of toxic hydrogen cyanide (HCN) molecules, interaction of pristine and defected Al-rich aluminum nitride nanotubes (AlNNT) with a HCN molecule has been investigated using density functional theory calculations in terms of energetic, geometric, and electronic properties. It has been found that unlike the pristine AlNNT, the Al-rich AlNNT can effectively interact with the HCN molecule so that its conductivity changes upon the exposure to this molecule. The adsorption energies of HCN on the pristine and defected AlNNTs have been calculated to be in the range of -0.16 to -0.62 eV and -1.75 to -2.21 eV, respectively. We believe that creating Al-rich defects may be a good strategy for improving the sensitivity of these tubes toward HCN molecules, which cannot be trapped and detected by the pristine AlNNT.

Arsenic interactions with a fullerene-like BN cage in the vacuum and aqueous phase.

Adsorption of arsenic ions, As (III and V), on the surface of fullerene-like B(12)N(12) cage has been explored in vacuum and aqueous phase using density functional theory in terms of Gibbs free energies, enthalpies, geometry, and density of state analysis. It was found that these ions can be strongly chemisorbed on the surface of the cluster in both vacuum and aqueous phase, resulting in significant changes in its electronic properties so that the cluster transforms from a semi-insulator to a semiconductor. The solvent significantly affects the geometry parameters and electronic properties of the As/B(12)N(12) complexes and the interaction between components is considerably weaker in the aqueous phase than that in the vacuum.

Hydrogen dissociation on diene-functionalized carbon nanotubes.

Chemical functionalization of a zigzag carbon nanotube (CNT) with 1, 3-cyclohexadiene (CHD), previously reported by experimentalists, has been investigated in the present study using density functional theory in terms of energetic, geometric, and electronic properties. Then, the thermodynamic and kinetic feasibility of H2 dissociation on the pristine and functionalized CNTs have been compared. The dissociation energy of the H2 molecule on the pristine and functionalized CNT has been calculated to be about -1.00 and -1.55 eV, while the barrier energy is found to be about 3.70 and 3.51 eV, respectively. Therefore, H2 dissociation is thermodynamically more favorable on the CNT-CHD system than on the pristine tube, while the favorability of the dissociation on the pristine tube is higher in term of kinetics.

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.