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Hu et al. reported the hydrogen storage properties of Sc2C and Ti2C based MXene phases utilizing density functional theory (DFT) as implemented in the CASTEP code [1, 2]. Based on such calculations, the authors suggest that the MXenes should be a new family of potential hydrogen storage media. Their results claim a maximum hydrogen storage capacity of 9.0 wt% with an average binding energy of 0.164 eV/H2 in Sc2C MXene indicating Kubas-type interaction between H2 and the MXene. These investigations are of prime importance since they provide insight about further applications of MXenes for hydrogen storage. In these calculations they have used local density approximation (LDA) to estimate the adsorption energies. However, binding energies for H2 with the MXene phases mentioned above obtained from more accurate calculations based on Generalised Gradient Approximation (GGA) and calculation including dispersion correction (GGA + vdW) show very weak binding energy ( ∼ 0.064 e V / H 2 ) suggesting weak physical interactions between H2 and the MXene phases. Our accurate DFT calculations predict that these MXene phases are not suitable for hydrogen storage at realistic conditions. So we conclude that appropriate exchange-correlation functional should be used to extract hydrogen adsorption energies in nano-phases to describe their hydrogen storage properties reliably.

For many centuries, paper was considered the main support for recording cultural achievements all over the world. Archives represent the historical memory of our past, and the book conservation represents one main concern since many books and documents kept in libraries and archives are at risk because of their fragility. The use of portable, not destructive technique like NIR μ-Raman spectroscopy represents a valid instrument for monitoring the documentary heritage. In the present study, we investigated the degradation process, associated to the polymers breaking, in order to propose a successful kinetic model for determining the ageing time of cellulose. We compared the calculated results with respect to both experimental samples and literature data, covering a period of seven centuries, from XV to XXI centuries. Proposed model starts directly from Raman spectra, in particular by monitoring the band at 1100 cm− 1 ascribed to C-O-C inter-monomers bond, whose relative intensity is related to the cellulose chain length. We obtained a very good agreement with the experimental data with 8% of accuracy. Finally, with the help of Density Functional Theory (DFT) simulations, we confirmed our model by studying the structure and the grade of cellulose crystallinity in the paper. In particular, the reverse trend of the band at 900 cm− 1, related to the crystallinity grade of the cellulose, and the band at 1100 cm− 1, as a function of the dimer unit cell structure, supported the kinetic model, suggesting a shear stress like effect as the origin of the cellulose chain length decrease.

A new chemosensor 1 was synthesized by reacting rhodamine B hydrazide and 2,3,4-trihydroxybenzaldehyde, which was then characterized by spectroscopic techniques and single crystal X-ray crystallography. Sensor 1 has the ability to sense Co2+/Cu2+ ions by “naked-eye” with an apparent colour change from colourless to pink in different solvent system, MeCN and DMF respectively. Furthermore, it can selectively detect Co2+/Cu2+ among wide range of different metal ions, and it exhibits low detection limit of 4.425 × 10−8 M and 1.398 × 10−7 M respectively. Binding mode of the two complexes were determined to be 1:1 stoichiometry for Co2+ complex and 1:2 stoichiometry for Cu2+ complex through Job’s plot, IR spectroscopy, mass spectrometry and 1H NMR spectroscopy. Moreover, reversibility of the sensor 1 as copper (II) ion detector was determined by using EDTA and the results showed that sensor 1 can be reused for at least 6 cycles. Other than that, a low cost chemosensor test strips were fabricated for the convenient “naked-eye” detection of Co2+ and Cu2+ in pure aqueous media. The MTT assay was conducted in order to determine the cytotoxicity of sensor 1 towards human cell lines.

VOCs in paper mills have severely exceeded the emission standards and their photo-catalytic degradations should focus on the experimental and theoretical studies. This work used TiO2 colloid as catalyst to study the photo-catalytic degradations of mixed HCHO and C6H6 at five mixing ratios. The adsorption behaviors of pure forms and mixtures on the TiO2 (101) surface were simulated using density functional theory (DFT), and their catalytic reaction mechanisms were also analyzed. The following results were found: (1) With increasing initial concentration, the enhanced adsorption and easy degradation interpreted the increased degradation rate for pure HCHO, while the counteractions of enhanced adsorption and inhibited catalytic reaction kept the constant degradation rate for pure C6H6. (2) For their mixtures, the HCHO degradation was inhibited at high C6H6 concentration due to the inhibited adsorption and catalytic reaction of HCHO. The C6H6 degradation was slightly weakened at high HCHO concentration and then restored to the normal degradation rate of C6H6, which could be attributed to the weakened adsorption of C6H6 and the easy degradation of HCHO in the initial stage. The combined experimental, simulation, and theoretical results provides sufficient information to understand the photo-catalytic degradation process for mixed gaseous pollutants in different realistic environments.

Motivated by the photocatalytic reactions of small molecules on g-C3N4 by these insights, we sought to explore the adsorption of H2O and CO2 molecules on the graphene side and H2O, H2, O2, CO, NO, and CO2 molecules on the g-C3N4 side of hybrid g-C3N4/graphene nanocomposite using first-principles calculations. The atomic structure and electronic properties of hybrid g-C3N4/graphene nanocomposite is explored. The adsorption of small molecules on graphene/g-C3N4 nanocomposite is thoroughly investigated. The computational studies revels that all small molecules on graphene/g-C3N4 nanocomposite are the physisorption. The adsorption characteristics of H2O and CO2 molecules on the graphene side are similar to that on graphene. The adsorption of H2O, H2, O2, CO, NO, and CO2 molecules on the g-C3N4 side always leads to a buckle structure of graphene/g-C3N4 nanocomposite. Graphene as a substrate can significantly relax the buckle degree of g-C3N4 in g-C3N4/graphene nanocomposite.

We report the results of X-ray spectroscopy and Raman measurements of as-prepared graphene on a high quality copper surface and the same materials after 1.5 years under different conditions (ambient and low humidity). The obtained results were compared with density functional theory calculations of the formation energies and electronic structures of various structural defects in graphene/Cu interfaces. For evaluation of the stability of the carbon cover, we propose a two-step model. The first step is oxidation of the graphene, and the second is perforation of graphene with the removal of carbon atoms as part of the carbon dioxide molecule. Results of the modeling and experimental measurements provide evidence that graphene grown on high-quality copper substrate becomes robust and stable in time (1.5 years). However, the stability of this interface depends on the quality of the graphene and the number of native defects in the graphene and substrate. The effect of the presence of a metallic substrate with defects on the stability and electronic structure of graphene is also discussed., 18 pages, 6 figures, accepted to Appl. Surf. Sci

The ultra-high specific surface area of graphene endows this two-dimensional material with an excellent capacity of ion absorption. Here we show that the ion absorption properties of graphene can be tailored via mechanical deformation. By using density function theory (DFT) analysis, we found that strain could enhance the ion absorption capacity of graphene. Our results provide perspective for the development of graphene-based electrochemical devices, such as stress difference battery and mechanochemistry sensors with graphene electrodes.

We report the ability of a pyrazino[2,3-g]quinoxaline derivative substituted with eight peripheral flexible n-octyloxy chains, to sense the volatile trifluoroacetic acid in trace amounts (in parts per billion levels). The reversible detection of acid sensing behavior was visually perceivable in both solution as well as in the drop-casted film on a TLC paper based strip. Density functional theory studies were carried out to elucidate the mechanism of the sensing behavior.

Halogen-functionalized graphenes are utilized as electronic devices and energy materials. In the present paper, the effects of halogen-termination of graphene edge on the structures and electronic states of graphene flakes have been investigated by means of density functional theory (DFT) method. It was found that the ionization potential ( Ip ) and electron affinity of graphene ( EA ) are blue-shifted by the halogen termination, while the excitation energy is red-shifted. The drastic change showed a possibility as electronic devices such as field-effect transistors. The change of electronic states caused by the halogen termination of graphene edge was discussed on the basis of the theoretical results.

Graphical abstract, In this study, density functional theory (DFT) and docking calculations were systematically performed to study the non-competitive interaction between Hydroxychloroquine (HCQ) and azithromycin (AZTH). The calculated changes in Gibbs free energy and enthalpy (at 310 K) were positive, indicating the non-spontaneous formation of HCQ-AZTH specifically in water media. Docking calculation confirmed the obtained DFT result as evident from the different binding sites of both drugs to the SARS-CoV-2 main protease and human angiotensin-converting enzyme 2 (ACE2) proteins. The HCQ-AZTH structure revealed enhanced electrochemical properties, suggesting the synergy between HCQ and AZTH without affecting their therapeutic efficacy against SARS-CoV-2.

Current iron ore processing generates about 25% of very fine material called iron ore slimes. These slimes are being disposed into tailing ponds owing to their high alumina content (10–15%) despite having good iron values (45–60% Fe). Due to the rapid depletion of high grade iron ores, there is an urgent need to develop effective beneficiation processes for utilization of slimes. The very fine size of the slime particles ( O guar gum chemical interactions as compared to only weak hydrogen bonds in the case of the other mineral surfaces. The experiments were designed to study the effect of the three key process parameters namely, pulp density, guar gum dosage and settling time on the beneficiation of iron ore slimes. The experimental data is used to develop models for prediction of yield, iron grade, % alumina and iron recovery in the concentrate. The models thus obtained are utilized to arrive at the optimized process parameters to achieve maximum iron recovery with acceptable iron grades with minimum alumina in the concentrates. These optimized process conditions shall form base line for further scale-up of the process at pilot/plant scale.

Silica has been used as support material with many photocatalytic materials. In this study, silica polymorphs on graphene and epoxy graphene were studied using Density Functional Theory (DFT) to determine the interfacial and optical properties of the composite material. The powder diffraction patterns and Raman spectra for the silica polymorph structural models as well as graphene and epoxy graphene monoxide were generated using Material Studio (2016), and the GGA in PBE first principle method. The electronic and optical properties as well as work function analysis of the polymorphs with graphene and epoxy graphene monoxide starting molecules together with the layers systems were compared. In Our findings the optical properties of the layers generated were sensitive to the visible light in both epoxy-graphene monoxide and graphene composites.

Density functional theory based on first-principle calculations was used to examine platinum-supported oxidized graphene as a beneficial nanomaterial in terms of its catalytic activity and utility for contaminant removal and disinfecting polluted solutions in both domestic and industrial applications. The first step was to select the most appropriate available computing package to apply the supercell technique, which would provide a better representation of a large and real graphene slab. Using OpenMX was less time-consuming after we enforced a basis set for valence electrons to avoid an all-electron calculation, and this had very slight and negligible effect on the accuracy of the calculations. The OpenMX software was selected to perform forward steps of investigating changes in the properties such as adsorption energy and ground state structure of the complexes made by the adsorption of a platinum atom on the surface of pristine graphene (Pt/PG) and oxidized graphene (Pt/OG), which had the lowest adsorption energy of −5.28 eV. Moreover, we examined the effect of Pt atom adsorption on the surface and between two layers of graphene. Our results show that, there was no specific change observed in mentioned properties of Pt atom adsorption on bilayer graphene in comparison with single layer.

In this work, adsorption of graphene on polar MnO(1 1 1) surface with and without hydrogen coverage was investigated by density functional theory. Local atomic reconstructions of the graphene/H:MnO(1 1 1) interface and their thermodynamic and electronic properties were analyzed for different adsorption models. Bond length and adsorption energy were found for different reconstructions of surface atomic structure in the graphene/H:MnO(1 1 1) systems. Effect of graphene adsorption on the electronic spectrum of the graphene/H:MnO(1 1 1) interface was also studied. The effective charge of carbon atoms and nearest-neighbor atoms were determined for the considered adsorption models. Our calculations show that the charge transfer from carbon atom to nearest-neighbor atoms is due to reconstruction of the local atomic and electronic structures, correlating with the interface hydrogenation concentration. At the interface hydrogen concentration of Θ = 1.0 ML (monolayer), the p–n junction was observed in the graphene and a new state, n-type semiconductor, is qualitatively emerged.

In this study, the strength of monolayer graphene oxide membranes was experimentally characterized. The monolayer GO membranes were found to have a high carbon-to-oxygen ratio (∼4:1) and an average strength of 17.3 N/m (24.7 GPa). This measured strength is orders of magnitude higher than previously reported values for graphene oxide paper and is approximately 50% of the 2D intrinsic strength of pristine graphene. In order to corroborate strength measurements, experimental values were compared to theoretical first-principles calculations. Using a supercell constructed from experimental measurements of monolayer graphene oxide chemistry and functional structure, density functional theory calculations predicted a theoretical strength of 21.9 N/m (31.3 GPa) under equibiaxial tension, in good agreement with the experimental data. Furthermore, computational simulations were used to understand the underlying fracture mechanism, in which bond cleavage occurred along a path connecting oxygenated carbon atoms in the basal plane. This work shows that monolayer graphene oxide possesses near-theoretical strength reaching tens of GPa.

In this work we investigated optoelectronic properties of graphene nanoparticles and transport properties of graphene nanosheets and the consequences on these properties after modifications with boron atoms. Within the framework of density functional theory (DFT) several important optoelectronic quantities have been calculated for graphene nanoparticles: oxidation and reduction potentials, hole and electron reorganization energies, while thermally activated delayed fluorescence was assessed by calculations of energy separation between the lowest excited singlet (S1) and triplet (T1) state, Δ E ( S 1 − T 1 ) . Obtained results show that optoelectronic properties of graphene nanoparticles are significantly improved by the modification with boron atoms and that investigated structures can be considered as a promising organic light emitting diode (OLED) materials. Influence of boron atoms to charge and heat transport properties of graphene nanosheets was investigated as well, employing the self-consistent non-equilibrium Green's functions with DFT. On the other side it is shown that charge transport of graphene nanosheets is not influenced by the introduction of boron atoms, while influence to the phonon subsystem is minimal.

Functionalized graphenes have been utilized as electronic devices and energy materials. In the present paper, the effects of fluorine-termination of graphene edge on the structures and electronic states of graphene have been investigated by means of density functional theory (DFT) method. It was found that the ionization potential (Ip) and electron affinity of graphene (EA) are blue-shifted by the F-substitution. On the other hand, the excitation energy was red-shifted. The drastic change shows a possibility as electronic devices such as field-effect transistors. The drastic change of electronic states caused by the F-substitution of graphene edge was discussed on the basis of the theoretical results.

In this study, the adsorption of methane molecules over boron, nitrogen and lithium doped graphene sheet is theoretically studied using density functional theory. Boron and nitrogen atoms are situated in a graphene network in graphitic, pyridinic and defect substitution forms, while Li atoms are placed out of the graphene layer. Density functional theory was applied to prepare the structures with the minimum level of energy by using 6-31G basis set. DFT-D3 correction was applied to calculate density functional dispersion correction. The results showed that methane molecules were adsorbed on all graphene doped surfaces with physisorption interactions. In addition, simulation results indicated that Li-doped graphene sheet was more reactive than the two other structures in terms of its higher adsorption energy and the medium distance of methane molecule from graphene sheet. Moreover, among various substitution forms of boron and nitrogen atoms in the graphene sheet, graphitic substitution is more stable due to the higher adsorption level of energy. The distribution of the highest occupied molecular orbital of nitrogen and boron substituted graphene showed the polarization nature of the graphene doped sheet in boron and nitrogen while lithium doped graphene was polarized at the adjacent carbons. After methane adsorption, no specific change was observed in highest occupied molecular orbital calculations of graphene sheets, which confirmed the physical adsorption behavior of methane molecule on the graphene doped sheets. In conclusion, Li doped graphene sheet is suggested as an appropriate material in comparison to nitrogen and boron doped structure for enhancing methane storage capacity.

The high affinity of graphene for H 2 S makes it a potential adsorbent for separating H 2 S from industrial waste gas streams, and for its use in H 2 S sensors. The gas streams containing H 2 S also contain S atoms that can get bonded to graphene during adsorption. Moreover, at high temperatures, H 2 S dissociate at graphene defects leading to H 2 desorption with S atom remaining on graphene. This study reports the effect of the presence of S atom on graphene on H 2 S adsorption using plane-wave density functional theory to assess the suitability of graphene-based adsorbents for continuous H 2 S capture. During H 2 S interaction with pristine graphene with S atom bonded to it, a surface cleaning mechanism was observed, where H 2 S exothermically removed S atom by forming H 2 S 2 . When S atom was doped in the single-vacancy defect of graphene, both physisorption and chemisorption of H 2 S was observed. The adsorption energy released during H 2 S physisorption on S-doped graphene was comparable to that for pristine graphene. However, during chemisorption, H 2 S dissociated on S-doped graphene to form HSSH bonded to graphene with the release of a high amount of energy. The results suggest that S atom in single-vacancy defects can enhance H 2 S capture on graphene.

Graphene, a two-dimensional monolayer of carbon atoms in honeycomb structure, is a research hotspot in multidisciplinary due to its excellent physical properties. To further extend the applications of graphene, various strategies have been proposed to tailor its physical properties. Recently, our group has carried out systematically computational studies on modifying graphene, including hydrogenation, oxidation, and introduction of grain boundaries. Both the hydrogenation and oxidation will convert sp 2 hybridized carbons into sp 3 configurations, while formation of grain boundaries only makes the sp 2 carbon bonds distorted. Employing density functional theory calculations, structures, physical properties and applications of these modified graphene were explored, such as structural phase diagram, mechanical and electronic properties, and photocatalytic applications. It turns out that many physical properties of graphene are tunable, endowing graphene promising applications in various fields. In this review article, we will generally summarize our recent works on the hydrogenated graphene, graphene oxide, and graphene grain boundaries.

Density functional theory calculations were performed to study the photocatalytic properties of molybdenum disulfide/graphene composites by analyzing the structure, electronic properties and optical properties of molybdenum disulfide/graphene composites. Three typical structures of molybdenum disulfide considered in our work include pristine molybdenum disulfide and molybdenum disulfide with mononiobium doping. They were then composited with graphene, N-doped graphene and graphene with epoxy, respectively. The characteristics of these composites (MoS 2 /graphene, MoS 2 /N-G, MoS 2 /O-G and Nb–MoS 2 /N-G) including binding energies, charge transfer, projected density of states, electron density and optical properties were calculated and analyzed. The binding energies of between MoS 2 and graphene were related to the extent of charge transfer. The data of projected density of states, band structures and optical properties gave an explanation of the mechanism for significant photocatalytic activity of MoS 2 /N-doped graphene and Nb-doped MoS 2 /N-doped graphene composites.

We computationally modeled the adsorptive behavior of O 2 , Li, LiO 2 , and Li 2 O 2 on graphene using density functional theory (DFT) in an effort to understand the mechanisms by which lithium oxides (Li x O 2 ) and oxygen reduction reaction (ORR) products adsorb onto graphene-based electrodes during lithium–air battery operation. O 2 weakly adsorbed onto graphene with a binding energy of −0.111 to −0.089 eV, whereas Li strongly adsorbed onto graphene with relatively large binding energy of −1.079 to −0.774 eV. The LiO 2 formation energy (−2.453 eV) was much lower than the LiO 2 adsorption energy (−0.450 eV) on graphene, indicating that after Li and O 2 had associated, LiO 2 adsorbed onto the graphene surface. Among the various Li 2 O 2 adsorption configurations, the parallel configurations in which Li 2 O 2 was oriented along the graphene axis (−0.630 to −0.611 eV) were more favorable than the perpendicular configurations (−0.513 to −0.475 eV). Consequently, more charges were transferred from Li to graphene in a parallel orientation.

The adsorption of MoS2 monolayer over reduced graphene oxide (RGO) using first-principles calculations based on the density functional theory was investigated. Also, the hybrid system was synthesized by the solvothermal method. The theoretical calculations of the band structure showed an electronic charge transfer from the MoS2 toward graphene. On the other hand the hybrid sample presented high dispersion of MoS2 on RGO.

Adsorption of sulfur dioxide (SO2) on intrinsic and modified graphene, including Stone–Wales (SW) defect, Al doping and a combination of these two, was theoretically studied using first-principles approach based on density functional theory (DFT). The most stable adsorption geometry, adsorption energy, magnetic moment, charge transfer and density of states of these systems are thoroughly discussed. It was found that SO2 molecule is weakly adsorbed on the intrinsic and SW defected graphenes and their electronic properties were slightly changed. The Al-doped graphene and the defect–dopant combination show high reactivity toward SO2. Compared with Al-doped adsorption system, the adsorption energy for Al-doped SW defect adsorption system can be enhanced by the introduction of a SW defect. This work reveals that the sensitivity of graphene-based chemical gas sensors for SO2 can be drastically improved by introducing dopant and defect, and the Al-doped SW graphene is more suitable for SO2 gas detection.

Density functional theory and molecular dynamics were used to study the adsorption of sulfur hexafluoride (which is an environmental problem) at the atmospheric pressure, on two surfaces. One is pristine graphene, and the other is graphene modified with titanium, with high metal coverage (C2Ti). We found that on the first surface, the molecule physisorbs at 77 K, and desorbs at 420 K. On the C2Ti surface, the molecule chemisorbs and dissociates completely, at 77 K.

In order to search for a gas sensor to detect hydrogen fluoride (HF), the adsorption of HF on transition metal-embedded graphene (TM/graphene) is investigated by density functional theory calculations. Compared with the relatively weak adsorption on other TM/graphene systems, HF molecule tends to be adsorbed on Ti/graphene with appreciable adsorption energy. Based on these calculations, two gas sensing mechanisms are proposed and revealed that both surface reconstruction and charge transfer result in a change of electronic conductance of Ti/graphene. Thus, this developed Ti/graphene would be an excellent candidate for sensing HF with lower cost and higher activity.

The effect of different doped atoms on the interactions between graphene sheets and hydrogen molecules were investigated by density functional theory calculations. The interactions between graphene sheets and hydrogen molecules can be adjusted by doped atoms. The Ti-doped graphene sheet had the largest interaction energy with the hydrogen molecule (approximately −0.299 eV), followed by the Zn-doped graphene sheet (about −0.294 eV) and then the Al-doped graphene sheet (approximately −0.13 eV). The doped N atom did not improve the interactions between the N-doped graphene sheet and the hydrogen molecule. Our results may serve as a basis for the development of hydrogen storage materials.

Understanding the interaction mechanisms of CO, NO, SO2, and HCHO with graphene are important in developing graphene-based sensors for gas detection and removal. In this study, the effects of doped Ti or N atom on the interaction of these gases with graphene were investigated by density functional theory calculations. Analyses of adsorption energy, electron density difference, and density of states indicated that the doped Ti atom could greatly improve the interaction of gas molecules with graphene. The Ti-doped graphene sheet demonstrated selective gas absorption. The order of interaction between the gas molecules and the Ti-doped graphene sheet was as follows: SO2 > NO > HCHO > CO. By contrast, the N-doped graphene sheet did not exhibit apparent selective gas absorption. These results imply that the Ti-doped graphene sheet is more effective than the N-doped graphene sheet in detecting and removing gas molecules because of its high selectivity.

We report a nano-scale quantification study of the adhesion energy of chemically vapor deposited (CVD) graphene on Cu and Ni. The adhesion energy of graphene on Cu and Ni substrates was measured to be 12.8 and 72.7 Jm � 2 , respectively. Density functional theory shows that the graphene/Ni interface exhibits more covalent bonding than graphene/Cu which is partially ionic, hence the reason for the higher adhesion energy for graphene/ Ni. We believe that this nano-scale adhesion energy measurement method could be further extended for measuring the adhesion energy of other 2D materials.

Atomic structure of Ti and Ti 4 cluster on the surface of graphene are studied by the density functional theory and nonequilibrium Green’s function formalism. The most stable configurations for Ti and Ti 4 adsorbed on the graphene surface are investigated, and the binding energies corresponding to the configurations are calculated. We found that the Ti 4 clusters can strongly interact with pristine graphene surface, and the interaction can be further enhanced when structural vacancies are introduced onto the graphene surface. Electronic properties of metal/graphene composites are also presented to show their highly spin polarized behaviors. The transport properties of systems are dependent on the applied bias voltage. Our results also indicate that the Ti 4 /graphene composite is a simple and typical model to study the interactive effects of metal clusters absorbed on graphene. The results of this work could help to design novel devices such as nanoelectrodes and magnetic sensors based on graphene.

A density functional theory (DFT) study of graphene synthesis from graphite oxidation and exfoliation is presented. The calculated DFT results for O adsorption predict C O as a most stable bond on the graphene oxide (GO) sheet. The obtained exfoliation energy for the graphene and the GO are 143 and ∼70 mJ/m 2 that verify easier exfoliation of the graphite oxide compared with the graphite. Furthermore, the DFT results show that for decreasing the exfoliation energy of the GO at least two layers of the graphite should be oxidized during the oxidation process.

S-nitrosothiols (RSNOs) are an important group of nitric oxide (NO)-donating compounds with low toxicity and wide biomedical applications. In this paper, we, for the first time, demonstrate that the concentration of buffer remarkably affects the stability of RSNOs including naturally occurring S-nitrosoglutathione (GSNO) and synthetic S-nitroso-N-acetylpenicillamine (SNAP). For a solution with a high concentration of GSNO (e.g., 50 mM) and an initial near-neutral pH, the optimal buffer concentration is close to the GSNO concentration under our experimental conditions. A lower buffer concentration does not have adequate buffer capacity to resist the pH drop caused by GSNO decomposition. The decreased solution pH further accelerates GSNO decomposition because GSNO is most stable at near-neutral pH according to our density functional theory (DFT) calculations. A higher-than-optimal buffer concentration also reduces the GSNO stability because buffer ingredients including phosphate, Tris base, and HEPES consume NO/N2O3. In contrast to GSNO, the highest SNAP stability is obtained when the starting solution at a neutral pH does not contain buffer species, and the stability decreases as the buffer concentration increases. This is because SNAP is more stable at mildly acidic pH and the SNAP decomposition-induced pH drop stabilizes the donor. When the RSNO concentration is low (e.g., 1 mM), the buffer concentration also matters because any excess buffer accelerates the donor decomposition. Since the effect of buffer concentration was previously overlooked and suboptimal buffer concentrations were often used, this paper will aid in the formulation of RSNO solutions to obtain the maximum stability for prolonged storage and sustained NO release.

The last few decades have seen an immense development of interest in two-dimensional materials, which can be integrated in either mono-, bi-, tri- or tetra-layer form. The tuning of physical properties of 2D materials is a prevalent challenge since they disclose enormous opportunities for electronic and opto-electronic devices. The functionality of two dimensional (2D) materials can be enhanced through several external factors such as strain, defects, doping, electric field, stacking, and mechanical stress, etc. Recently, the two-dimensional III-V (III = B, Al, Ga, In, Tl and V = N, P, As, Sb, and Bi) monolayers have been theoretically discovered. The present research has been designed to study the variations in their properties under a small range of external electric field. Previous studies have been highlighted which suggested that electric field can be an effective approach to improve the physical properties of 2D materials. In this paper, the influence of an external electric field, in the range of −0.3 VA−1 to 0.3 VA−1, on the structural, electronic and optical properties of III-V monolayers has been investigated using the first-principles calculations in the context of density functional theory (DFT). The results suggest that monolayers retain their geometrical properties. However, the electric field enhances the strength of covalent bonds. The results also disclose that the bandgap of these monolayers can be widely tuned with the help of electric field. As the electric field is raised, few of the monolayers exhibit transition from semiconducting to conducting behavior. Moreover, the optical absorption is also observed to modify with electric field. The amount of absorption and the energy at which electronic transitions occur vary uniformly with electric field. The transparency of few monolayers in visible region alongwith maximum absorption in UV region ensures their potential for Visible-blind UV detectors, flat panel displays and window layers in solar cells. The bandgap-type transition promise their application in low-power electronic devices and widely tunable bandgap shows their potential for various opto-electronic devices. The findings of this paper focus on the contribution of III-V monolayers to the development of more efficient electronic and opto-electronic devices.

Among all inorganic perovskite, CsPbI3 has the closest ideal bang gap for solar cells. However, the instability of metal halides hinders its commercial application. The doping of A-site organic cations might improve the stability of perovskite and also make the bandgap adjustable, thus enhance its photoelectric properties. In this paper, the structure stability, electronic structure and optical properties of CsPbI3 with five different organic cations (H3NNH2+, CH3NH3+, C3H6NH2+, CH3NH2CH3+, CH3CH2NH3+) partially alternative doping instead the A site cation have been studied by using the first principles within density functional theory. In order to get accurate description of the bandstructure information, different exchange–correlation functions, e. g. PBE, PBE + SOC and HSE were used to describe the calculated systems, our calculation results indicated that the PBE exchange–correlation function can describe the electronic properties of the systems very well in this paper. Formation energy calculation indicates that all the doping systems are thermally stable; and all the doped CsPbI3 show good tolerance factor according Goldschmidt rule. Among the five different doping systems, the bandgap of doped H3NNH2+ will decrease to 1.28 eV, while the bandstructure of other doped cations will widen the bandgap. The maximum bandgap increased to 1.65 eV with doping C3H6NH2+. However, all the band structures are mainly contributed by inorganic framework. The results suggest that the structure doped organic cations can be exited stably, and the band edge of the optical absorption spectrum will be redshifted. These properties can provide research ideas for the subsequent research of A-site doping organic cations.

In this paper, the topological phase of LuX (X = Sb, Bi) compounds under hydrostatic and biaxial pressures is investigated based on first principles of density functional theory by WIEN2k package. To find out the Z2 topological invariants of centrosymmetric compounds with the time reversal symmetry, the Bloch functions parity analysis can be used via electronic band structure calculations. So in this paper the Z2 topological invariants of the LuX (X = Sb, Bi) compounds with the time reversal and inversion symmetries are calculated using this approach. The results show that the d-p band inversion can be occurred in these compounds due to spin orbit interaction and appropriate pressure. These compounds have the strong electronic interaction due to their large d-electronic orbitals near the Fermi energy. The dynamic stability of these compounds is verified by phonon modes analysis. The surface states topological phase of these compounds are investigated based on the band structure calculations.

Based on the density functional theory (DFT) combined thermodynamics method, the flue gas arsenic forms from the coal-fired power plants were successfully confirmed at different temperature ranges, and the interaction mechanism of the fly ash unburned carbon (UBC) components on different gaseous arsenic species were also investigated. The content of trivalent arsenic (As3+) is the highest in flue gas, and its morphological distribution is significantly affected by the flue gas temperature. When the flue gas temperature is lower than 900 K, the As2O3 molecules are dominant in the trigonal bipyramid type. While when the temperature exceeds 900 K, the priority structure of As2O3 is chain type > horn type > trigonal bipyramid type in turn. This paper has verified the feasibility for the adsorption of flue gas arsenic via the unburned carbon in fly ash, and the performance of the zigzag carbon surface is always better than the armchair surface. This paper provides theoretical support for arsenic removal in coal-fired power plants, and also provides some new ideas for the secondary utilization of fly ash and the development of carbon-based arsenic removal adsorbent.

The present paper deals with quantitative kinetics and thermodynamics of collision induced dissociation (CID) reactions of piperazines under different experimental conditions together with a systematic description of effect of counter-ions on common MS fragment reactions of piperazines; and intra-molecular effect of quaternary cyclization of substituted piperazines yielding to quaternary salts. There are discussed quantitative model equations of rate constants as well as free Gibbs energies of series of m–independent CID fragment processes in GP, which have been evidenced experimentally. Both kinetic and thermodynamic parameters are also predicted by computational density functional theory (DFT) and ab initio both static and dynamic methods. The paper examines validity of Maxwell–Boltzmann distribution to non–Boltzmann CID processes in quantitatively as well. The experiments conducted within the latter framework yield to an excellent correspondence with theoretical quantum chemical modeling. The important property of presented model equations of reaction kinetics is the applicability in predicting unknown and assigning of known mass spectrometric (MS) patterns. The nature of “GP” continuum of CID–MS coupled scheme of measurements with electrospray ionization (ESI) source is discussed, performing parallel computations in gas–phase (GP) and polar continuum at different temperatures and ionic strengths. The effect of pressure is presented. The study contributes significantly to methodological and phenomenological developments of CID–MS and its analytical implementations for quantitative and structural analyses. It also demonstrates great prospective of a complementary application of experimental CID–MS and computational quantum chemistry studying chemical reactivity, among others. To a considerable extend this work underlies the place of computational quantum chemistry to the field of experimental analytical chemistry in particular highlighting the structural analysis.

Nanolaminates such as the Mn+1AXn (MAX) phases are a class of materials with hexagonal crystal structure for which ab-initio derived elasticity tensors have been published due to sizeable single-crystals not being available. Single crystal elastic constants, however, are fundamental to understanding phase transitions, and a range of mechanical, fracture, wear and electro-mechanical properties. Recent experiments using neutron powder diffraction indicated strong shear stiffness in case of Ti 3 SiC 2 via a large value for c44. The data presented in this paper combine neutron spectroscopy and a detailed ab-initio Molecular Dynamics - Density Functional Theory calculation and confirm the magnitude of c44 without the need of a micromechanical model. Additionally, the calculations allow estimating the remaining cij using the experimental value of c44. Nanolaminates such as the Mn+1AXn (MAX) phases are a class of materials with hexagonal crystal structure for which ab-initio derived elasticity tensors have been published due to sizeable single-crystals not being available. Single crystal elastic constants, however, are fundamental to understanding phase transitions, and a range of mechanical, fracture, wear and electro-mechanical properties. Recent experiments using neutron powder diffraction indicated strong shear stiffness in case of Ti3SiC2 via a large value for c44. The data presented in this paper combine neutron spectroscopy and a detailed ab-initio Molecular Dynamics - Density Functional Theory calculation and confirm the magnitude of c44 without the need of a micromechanical model. Additionally, the calculations allow estimating the remaining cij using the experimental value of c44.

In this paper, the adsorption properties of Cr modified InN (Cr-InN) and GaN (Cr-GaN) monolayers to SF6 decomposed components were investigated based on the density functional theory (DFT). Results reveal that these two graphene-like materials exhibit strong adsorption capacity for the three decomposed species SO2, SOF2 and SO2F2. Remarkable adsorption energy, significant charge transfer and molecular deformation indicate the occurrence of chemisorption. The hybridization of atomic electron orbitals in the density of states calculation verifies the strong chemical interaction between the gases and two monolayers. According to this strong adsorption capacity, Cr-InN and Cr-GaN monolayers demonstrate their potential as gas Scavenger for removing SF6 decomposition products in the insulation equipment. Besides, the significant change in conductivity of the monolayer caused by gas adsorption makes it possible to explore gas sensors based on Cr-InN and Cr-GaN monolayer. This paper indicates that Cr-doped InN and GaN monolayers can be used as adsorbents and sensors to guard the operation status of SF6 insulation devices by detecting and scavenging SF6 decomposed components.

High-entropy ceramics with five or more cations have recently attracted significant attention due to their superior properties for various structural and functional applications. Although the multi-component ceramics have been of interest for several decades, the concept of high-entropy ceramics was defined in 2004 by producing the first high-entropy nitride films. Following the introduction of the entropy stabilization concept, significant efforts were started to increase the entropy, minimize the Gibbs free energy and achieve stable single-phase high-entropy ceramics. High-entropy oxides, nitrides, carbides, borides and hydrides are currently the most popular high-entropy ceramics due to their potential for various applications, while the study of other ceramics, such as silicides, sulfides, fluorides, phosphides, phosphates, oxynitrides, carbonitrides and borocarbonitrides, is also growing fast. In this paper, the progress regarding high-entropy ceramics is reviewed from both experimental and theoretical points of view. Different aspects including the history, principles, compositions, crystal structure, theoretical/empirical design (via density functional theory, molecular dynamics simulation, machine learning, CALPHAD and descriptors), production methods and properties are thoroughly reviewed. The paper specifically attempts to answer how these materials with remarkable structures and properties can be used in future applications.

Zinc oxide is regarded as a third generation transparent conductive film which can replace indium doped tin oxide. It can be widely used in the electrodes of solar cells, the display of electronic instruments and other devices. In this paper, the photoelectric properties of ZnO thin films and their different growth directions were studied, and the best growth direction was obtained. The ZnO system was calculated by density functional theory. The band structure, density of states and other electronic properties of the stable structure are calculated by using Quantum Espresso program. It is found that the Valence Band Maximum and Conduction Band Minimum of ZnO (002) crystal plane both pass through the Fermi level, and the system exhibits semi-metallic properties, which has an important effect on the electrical properties. The band structure is interpolated by wannier90 program, and the precise maximum localized Wannier functions are obtained. Phonons properties are studied by density functional perturbation theory, and the accurate phonon dynamic matrix and the electron phonon coupling matrix elements are obtained. Based on that, the Perturbo program is used to solve the Boltzmann Transport Equation by using relaxation time approximation and electron phonon coupling theory. The scattering rate and relaxation time under different temperature are obtained and the reason why the conductivity and mobility decrease with the increase of temperature is analyzed. In the optical properties of the calculation, the time-dependent density functional theory and epsilon.x program are used to solve the Kohn–Sham equation, and then find out the refractive index, absorption coefficient, visible light transmittance and other important optical properties by obtaining the dielectric function. Combined with the analysis of electrical and optical properties, the (002) crystal plane is determined to be the best growth direction, which is well consistent with the preferred orientation obtained from the experiment. Therefore, it provides a theoretical basis and support for the preparation of better ZnO thin films. The work in this paper fills the blank of theoretical research on ZnO.

In this paper, electron transport in quantum dot sensitized solar cell (QDSSCs) linkers is studied by using density function theory (DFT). Experimentally, the linker effect on the solar cell efficiency has been a topic of interest to researchers. However, electron transport in linkers is simulated in this paper for the first time. We have introduced a new figure of merit as “molecular resistance parameter” to compare the performance of the linkers. In this study, 3-Aminopropyl trimethoxysilane (APS), p-Aminophenyl trimethoxysilane (APhS), Mercaptobenzoic acid (MBA), Mercaptopropionic acid (MPA) and Mercaptoacetic acid (MAA) Molecules are simulated as common linkers in quantum dot sensitized solar cells. In addition, we compared electron transport for APS and APhS linkers in case of three atoms of linker interact with the electron acceptor and case of only one atom of linker interact with the electron acceptor. In this study, DMol3 is used to simulate the optical and electrical properties of linker molecules. The simulation results can be used in the optimization of quantum dots sensitized solar cells.

Efavirenz,(S)-6-chloro-4-(cyclopropylethynyl)-1,4-dihydro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one, is an anti HIV agent from the class of the non-nucleoside inhibitors of the HIV-1 virus reverse transcriptase. This paper describes the synthesis of two new solvatomorphs of efavirenz (EFV). The results through XRPD and DSC/TG indicate that the new forms undergo a solvent loss over the days, and then return to the original polymorph. Structural and spectral characteristics of EFV were studied by vibrational spectroscopy and quantum chemical methods. Density functional theory (DFT) calculations for the potential energy curve, optimized geometries and vibrational spectra were carried out using 6-311 + G** basis sets and CAM-B3LYP functional, solid state calculations were also performed using DFT-XGGA (PBE-D3) exchange-correlation functional with the option of mixtures of Gaussian and plane waves method (GPW). Based on these results, the paper discussed the correlation between the vibrational modes and the crystalline structure of the most stable form of EFV. A complete analysis of the experimental infrared and Raman spectra was reported on the basis of the wavenumbers of the vibrational bands and the potential energy distribution.

This paper first uses density functional theory combined with the method of quantum chemistry calculations to obtain the electrostatic potential surfaces of the four main triglyceride molecules in palm oil and the water molecule, which reveals the reactivities of triglyceride molecules and the water molecule from a microscopic perspective. In addition, the conductor-like screening model for real solutions (COSMO-RS) method is used to calculate the σ-profile of the main active components of naphthenic mineral oil and the four main triglycerides in palm oil. Then, the COSMO-RS model of the triglyceride-hydrocarbon system is constructed, which theoretically predicts the solubility of the four main triglyceride molecules tripalmitin, tristearin, triolein, and trilinolein in mineral oil. The results show that triglyceride molecules and the mineral oil molecules have similar intermolecular forces, so triglyceride molecules can easily dissolve into the mineral oil. The results of this paper can provide theoretical reference and calculation support for the development of new-type mixed insulating oil for transformers.

In this paper, the authors conduct an in-depth investigation for the thermochemical reaction of organic carbon and H free radical during oil shale retorting process. A set of carbon chain and reaction models were constructed and calculated through the transition state theory (TST) of quantum chemistry with Gaussian-16 package. The effect of functional groups during the reactions was explored through the density functional theory (DFT) at the B3LYP/6-311G (d) level. To make the calculation results more trustful and reliable, we choose reasonably simplified straight carbon chain models and construct the corresponding multiple reaction paths, which could elucidate the mechanisms of the thermochemical reaction. In the presence of H free radical, the cracking process of carbon chains in kerogen is promoted because of lower energy barriers. The charge re-distribution causing by the functional group also changes the H adsorption capacity of the organic carbons in different positions (α, β, γ, etc.). Moreover, different measuring methods of the rate constants are evaluated in this paper. The results could provide direct insight into the limitation of the conventional transition state theory (TST), which deserves more attention in further theoretical research.

Thiols are widely used in the preparation of self-assembled monolayers (SAMs) on metallic surfaces such as Ag, Cu and Au because of their strong affinity for such surfaces. These SAMs have various applications in nanotechnology and supramolecular chemistry. However, the chemistry of the metal surface and the thiol end is still vaguely understood, yet it fundamentally governs the properties of the SAMs. This paper reports density functional theory (DFT) and corroborating experimental findings focusing on vibrational Raman spectroscopy of Ag-Mercaptobenzoic acid (AgMBA) SAMs. The 4-MBA thiol was self-assembled onto Ag (111) and (100) fcc surfaces via both the COO- and S- ends. The experimental AgMBA vibrational frequencies showed the interaction of the 4-MBA with the Ag surface from both the S- and COO- atoms and the observation was supported by the our own n-layered integrated molecular orbital and molecular mechanics (ONIOM) calculated surface-enhanced Raman spectroscopy spectra and DFT thermodynamic calculations. The Ag(100)MBA self-assembled via the COO- end had the highest enthalpy of adsorption of -310.34 kJ/mol and it was the most stable plane contradicting the sulphur end consensus on previous papers. The adsorption of the 4-MBA moiety on the Ag surface was interplayed by the corrugation potential of the exposed surface and the thiol’s aromatic nature which resulted in the adsorption of 4-MBA predominately via the carbonyl end at slightly acidic pH conditions and a deprotonated thiol end.

The detection of low-concentration hydrogen peroxide (H2O2) has important theoretical-significance and practical value in many fields, such as medical science, biological chemistry, and food safety inspection. Traditional commercial H2O2 test paper and detection technology can only reach the detection limit of 10−3–10−5 (mass fraction). In this paper, we report a simple method to prepare 2D MOF (metal-organic frameworks) [Co3(HOB)2]n films based on Langmuir-Blodgett (LB) method combined with layer-by-layer growth technique. Even 3-layer [Co3(HOB)2]n films can realize the lowest H2O2 detection limit of 1.05 × 10−8 wt% (3.08 nmol·L−1) based on the resultant 2D MOF catalyst. Meanwhile, density functional theory (DFT) calculations revealed that Co2+ ions of the LB films decreased the energy of [HOOH] transforming into [HO2] during the H2O2 reduction reactions, thus speeding up the decomposition of H2O2.

This paper reports the physicochemical analysis of the multilayer adsorption of anionic dyes on lignocellulosic biomasses. Experimental studies, statistical physics modeling and density functional theory (DFT) calculations were carried out to understand and characterize the adsorption mechanism of dyes Acid Blue 29, Acid Blue 113 and Reactive Blue 4 using coconut shells, cauliflower cores and broccoli stalks as low-cost adsorbents. Steric parameters and adsorption energies were estimated from an advanced multilayer statistical physics model and these parameters were associated with the biomass composition and dye molecular properties. DFT calculations were also performed to characterize the atomic interactions of dye molecules and surface functionalities from the main biopolymers contained in the lignocellulosic biomasses. Results showed that the multilayer adsorption of these anionic dyes was related to the cellulose contained in these biomasses where the best adsorption capacities were obtained for cauliflower cores with a cellulose composition of 11.2%. It was also confirmed that the dye aggregation played an important role for the removal of these adsorbates where cluster formation was significantly affected by adsorption temperature. Hydrogen bonding was the main interaction for the endothermic dye adsorption using these biomasses. Results reported in this paper contribute to understand the dye adsorption mechanism using low-cost adsorbents like lignocellulosic materials with the aim of improving the performance of treatment technologies for water decolorization.

According to density functional theory (DFT), a novel carbon allotrope is first predicted and investigated in this paper, denoted as oP72 carbon. oP72 carbon is mechanically stable and dynamically stable. There are fourteen carbon atom positions in oP72 carbon, it is an all-sp3 hybridized bonding network, and 4, 5, 6, 10 and 12 membered rings exist in the crystal structure of oP72 carbon. The shear modulus (224 GPa) and bulk modulus (269 GPa) of oP72 carbon are both slightly larger than those of C64, Y carbon, TY carbon, and T carbon, and the shear modulus of oP72 carbon is slightly greater than that of Pnma-BN. The conduction band minimum of oP72 carbon is situated in the X point, when the maximum value of the valence band of oP72 carbon is from point T to point Y, the indirect band gap of oP72 carbon is 2.941 eV. Therefore we speculate the oP72 carbon is an indirect semiconductor material. Furthermore, the Debye temperature, elastic anisotropy, Poisson’s ratio v, and Young’s modulus E of oP72 carbon are calculated and discussed systematically in this paper.

SiC is a two-dimensional semiconductor with a direct band gap. Many authors studied its electric and magnetic properties in sheet and ribbon shapes. The previous papers have shown that SiC sheet and full saturated armchair ribbons are non-magnetic (NM) semiconductor while zigzag ribbons are ferromagnetic (FM) semiconductor. In this paper, we saturate only C (CH) and Si (SiH) atoms of armchair ribbon by hydrogen and study its electric and magnetic properties by density functional theory (DFT). Our results show that CH, saturated carbon atoms in armchair ribbon, can show both FM and antiferromagnetic (AFM) semiconductor states while SiH, saturated silicon atoms in armchair ribbon, can show both FM half-metal and AFM metallic states. We found that the total magnetic moment of the unit cell is about 2 μB. Our results confirm that armchair ribbons can show many different magnetic states only by hydrogen saturation.