Adsorption Energy Values Research Articles

CO and CO2 adsorption performance of transition metal-functionalized germanene

In this work, the pristine and transition metal (TM)-functionalized germanene are investigated for sensing applications. Firstly, the detection of CO and CO2 molecules by pristine germanene is considered, and the numerical results show that adsorption energy values are in the physisorption range. Then, the adsorption of CO and CO2 molecules on Cu-, Ag-, and Au-functionalized germanene is studied. Results show that germanene functionalization with TM atoms considerably improves the interaction towards CO molecule when bound through the C atom [CO(C)], in the chemisorption range. On the other hand, numerical results show that the germanene sensing capabilities for the CO(O) and CO2 molecules do not improve with TM, these were adsorbed in the physisorption interval. Results suggest that the TM-functionalized germanene can have potential uses in CO sensing.

In Silico Designing of Mg12O12 Nanoclusters with a Late Transition Metal for NO2 Adsorption: An Efficient Approach toward the Development of NO2 Sensing Materials.

Gas sensors are widely used for detection of environmental pollution caused by various environmental factors such as road traffic and combustion of fossil fuels. Nitrogen dioxide (NO2) is one of the leading pollutants of the present age, which causes a number of serious health issues including acute bronchitis, cough, and phlegm, particularly in children. Nowadays, researchers are focused on designing new sensor materials for detection and removal of NO2 from the environment. In this line, we have made an attempt to design NO2 sensing materials by using theoretical techniques. Here, we have reported decoration of Mg12O12 nanoclusters with a late transition metal (Cu) by employing density functional theory at the B3LYP/6-31G(d,p) basis set. The decoration of metal on Mg12O12 gives two geometries (M1 and M2) with adsorption energies of −363.81 and −384.09 kJ/mol, respectively. Adsorption of NO2 on pristine Mg12O12 expressed an adsorption energy value of −62.36 kJ/mol. Adsorption of NO2 on Cu-decorated Mg12O12 nanocages delivered two geometries (N1 and N2) with adsorption energies of −442.56 and −447.64 kJ/mol. Metal-decorated Mg12O12 nanoclusters offer better adsorption of NO2 as compared to pristine Mg12O12. Adsorption of NO2 on Cu-Mg12O12 nanoclusters also causes narrowing of band gap of magnesium oxide nanoclusters. Large dipole moment, high QNBO with large electrophilic index in NO2-Cu-Mg12O12 nanoclusters suggested that metal-decorated Mg12O12 nanoclusters are efficient candidates for NO2 adsorption. Different geometric parameters and results of global reactivity descriptors show that NO2-Cu-Mg12O12 nanoclusters are quite stable in nature with least reactivity. Thus, conceptualized systems are potential candidates for applications in NO2 sensing materials.

Ionic bond in hydrogen transferring of the ferrous and/or ferric human/mouse verdoheme oxygenase.

Formation of five coordinated ferric (ferrous) verdoheme oxygenase complexes have been investigated at ωB97X-D/6-31G(d) level of theory. This process was carried out by adsorption of imidazole and human/mouse verdoheme oxygenase (VO) compounds. Global reactivity indexes show electrophile and nucleophile roles of the VO complexes and Imidazole, respectively. This result confirms their interaction, molecular electrostatic potential (MEP) maps, and low HOMOFRVMO-LUMOImidazole gap. These interactions can cause in adsorption and five coordinated of the VO complexes. More negative value (-64.3kJmol-1) of adsorption energy (Eads) in the FRVMO complex shows better adsorption strength and stable configuration. Significant point of this interaction is hydrogen transfer from imidazole to the nearest oxygen of the VO complexes; this issue is approved using quantum theory of atom in molecule (QTAIM) and natural bond orbital (NBO) analysis. QTAIM calculations confirm ionic bonding between the transferred hydrogen and the oxygen atom of the VO. The 312.2-kcalmol-1s order stabilization energies in this complex are confirmation for strong donation and better formation of five coordinated complex in electron view point.

Lithium clusters on graphene surface and their ability to adsorb hydrogen molecules

This research describes the theoretical study of the adsorption of lithium clusters on graphene and the ability to capture hydrogen molecules. The results of the studied structures showed that the [Li1C54H18]+ system is capable of accepting three hydrogen molecules showing adsorption energies of 0.12 eV. On the other hand, it is important to note that in [LinC54H18] n = 2–6 systems, the lithium atoms that do not interact with the graphene surface, they can adsorb up to four hydrogen molecules. The [Li6C54H18]4H2 system presented a higher adsorption energy value of 0.31 eV. Finally, the Li–H2 interactions were characterized by a NBO analysis, which showed that hydrogen atoms are the donors and lithium atoms are the acceptors.

Adsorption of methylene blue cationic dye onto brookite and rutile phases of titanium dioxide: Quantum chemical and molecular dynamic simulation studies

This study reports the statistical physics modeling of the methylene blue cationic dye (MBCD) adsorption in aqueous solution on TiO2 surface. In order to comprehend the adsorption performance, theoretical investigations were done to collect extensive information about the chemical and physical properties of the molecules using quantum chemical parameters (QCP). Also, molecular dynamic and quantum descriptors were applied to better understand the dye adsorption on different phases of TiO2 (i.e., brookite and rutile). The molecular structures of MBCD acts as good electron donators to an empty d orbital of TiO2 due to the availability of electrons in both the lone pair on the N atoms and π electrons of the aromatic rings. The reactivity of optimized molecular structures was confirmed by the quantum chemical descriptors. Modeling results showed that the adsorption was performed with a horizontal position of MBCD molecules on both surfaces. Overall, the TiO2 showed the highest adsorption energies for protonated MBCD (N36N35) (-886.533 kcal/mol (MBCD/rutile-TiO2)) > −626.428 kcal/mol (MBCD/brookite-TiO2)), which implies that these sites prompt the adsorption on both surfaces. The analysis of the adsorption energy values showed an exothermic chemisorption process, which could be governed by steric parameters according to the results obtained with the molecular dynamics modeling.

A density functional theory study of molecular H2S adsorption on (4,0) SWCNT doped with Ge, Ga and B

The molecular adsorption of hydrogen sulfide has been investigated theoretically by using Density Functional Theory for gallium (Ga), germanium (Ge) and boron (B) doped (4,0) single-walled carbon nanotubes (SWCNTs). The method of B3LYP was utilized with basis sets of 6-31G(d,p) and LANL2DZ. Adsorption energy and adsorption enthalpy, HOMO and LUMO energy values, HOMO-LUMO energy gap, chemical hardness, chemical potential, electronegativity and Gibbs free energy values have been evaluated in this study. All doped SWCNT structures have negative Gibbs free energy and adsorption energy values which make these clusters promising for the removal of H2S by adsorption. However, Ge doped SWCNT cluster has the lowest HOMO-LUMO energy gap and chemical potential, highest electronegativity with minimum adsorption energy values when compared to other clusters. Furthermore, it is softer than other metal doped SWCNT clusters due to the lower chemical hardness value.

In Silico Adsorption of Lomustin anticancer drug on the surface of Boron Nitride nanotube

The present study aimed to assess the adsorption of Lomustin on the single-walled Boron Nitride nanotube which has been examined using Density Functional Theory (DFT), agent in a solvent phase (water) at the B3LYP/6-31G (d) theoretical level. Initially, the structures of Lomustin, Boron Nitride nanotube, and Lomustin complexes with Boron Nitride nanotubes were designed in Gauss View in three different conformers and were optimized geometrically, on which IR and frontier molecular orbital computations were carried out. Adsorption energy values, Gibbs free energy changes (ΔGad), adsorption enthalpy changes (ΔHad), and equilibrium thermodynamic constants were estimated. The results showed that adsorption process was spontaneous, exothermic and non-equilibrium. The values of specific heat capacity and adsorption enthalpy indicate that this nanostructure can be used to build new thermal sensors to measure Lomustin. The results of molecule orbitals estimations showed that energy gap, after drug absorption on the nanotube surface, decreased significantly and the values of chemical hardness and dipole moment were studied after the interaction of drug with adsorbent and the results showed that drug solubility and reactivity, after adsorption on Boron Nitride nanotubes, increased significantly. According to the obtained results for adsorption of Lomustin, this nanostructure can be used as a sensing material in building new electrochemical sensors to measure this drug.

Graphene-like BC3 and NC3 flakes as promising drug delivery systems

In recent years, two-dimensional nanostructures have become some of the most interesting to be studied for application in the drug delivery. Novel two-dimensional layers, denoted by BC 3 and NC 3 flakes, have been previously synthesized. Motivated by these interesting nanomaterials, in the present study, we have investigated the pristine graphene as well as BC 3 and NC 3 flakes as versatile drug delivery systems. The main objective of the present work is to study the interaction of graphene, BC 3 , and NC 3 flakes with 5-fluorouracil (FU) anticancer drug using the density functional theory (DFT). We found that the more negative values of adsorption energies in the solvent phase reveal that the considered flakes can improve their solubility and modify their interaction with the drug in the aqueous phase. Also, our ultraviolet–visible analysis shows that the electronic spectra of the drug/sheet complexes show a blue shift toward lower wavelengths. To gain insight into the binding features of considered systems with FU drug, the Atoms in Molecules analysis was also performed. Our results determine the electrostatic features of the drug/BC 3 flake bonding. Therefore, ore calculations demonstrated that the graphene-like BC 3 flake could be used as potential carrier for the delivery of the 5-fluorouracil anticancer drug. Graphene-like BC3 flake as versatile drug delivery system. • The stability and electronic properties of graphene-like BC 3 and NC 3 flakes were studied. • The 5-fluorouracil adsorption on the surface of BC 3 is more favorable than the NC 3 . • Electronic spectra of drug/flake complexes exhibit a blue shift toward lower wavelengths. • BC 3 flake could be used as potential carrier for delivery of 5-fluorouracil in the nanomedicine domain.

Comparison of Adsorption Conformation of Comb‐Shaped Polycarboxylate on Tricalcium Aluminate (100) and Ettringite (100) Surfaces: A Molecular Dynamics Study

AbstractThe adsorption conformations of three comb‐shaped polycarboxylate (PCE) with different numbers of grafted side‐chains on the tricalcium aluminate (C3A) and ettringite surface is studied by all‐atom molecular dynamics (MD) simulations with INTERFACE‐PCFF forcefield. The similarity of absorbed PCEs on both surfaces is backbones of PCEs absorbed on the surface and the side‐chains extended to liquid phase. The difference is that side‐chains of PCEs keep a tilt angle with the C3A crystal but maintain parallel and closer to ettringite crystals. The absolute value of adsorption energy of PCEs on C3A surface is greater than that on ettringite surface, which indicate the stronger interaction between PCEs and C3A than ettringite. PCE with less side chains is favorable for the adsorption due to stronger electrostatic interaction with surface. Adsorption capacity and water‐reducing ability of PCEs are contradictory. Density of water near the solid–liquid interface is more severely decreased by PCE with more side chains. Correlation of the adsorption conformation of PCEs with the flow behaviors of fresh cement paste is summarized.

How does the defect ZnO@Au surface activate the methane via the precursor-mediated mechanism?

It is imperative to explore advanced catalysts that could activate methane in a mild manner. Herein, using density function theory (DFT), we have investigated the activation mechanism for the dissociation of methane, which is adsorbed on the triangle defect surface of ZnO@Au, where the defect ZnO(001) nanosheet is supported by Au(111). We found that the triangle defects induced coordination unsaturated O and Zn on the ZnO@Au are of great importance for this dissociation process, as the coordination unsaturated O and Zn not only can stabilize the methane, but also can polarize the CH bond through the dynamic frustrated Lewis pairs. Compared with perfect ZnO@Au heterojunction, the defect ZnO@Au can activate methane via precursor-mediated mechanism where the activation energy (0.21 eV) is lower than the absolute value of adsorption energy (0.48 eV). Such outstanding activation mainly originates from the electronic interaction between the methane and the coordination unsaturated O as well as Zn. Overall, the result not only provide a vital insight into the catalytic mechanism of the methane activation on ZnO@Au, but also give a new thought to develop catalysts for the facile methane activation.

Tailoring the d-Band Center of Double-Perovskite LaCoxNi1-xO3 Nanorods for High Activity in Artificial N2 Fixation.

The d-band center of a catalyst can be applied for the prediction of its catalytic activity, but the application of d-band theory for the electrocatalytic nitrogen reduction reaction (eNRR) has rarely been studied in perovskite materials. In this work, a series of double-perovskite LaCoxNi1-xO3 (LCNO) nanorods (NRs) were synthesized as models, where the d-band centers can be modulated by changing the stoichiometric ratios between Co and Ni elements. Experimentally, the LCNO-III NRs (x = 0.5) attained the highest faradic efficiency and NH3 yield rate among various LCNO NRs. This result matches well with the finding from theoretical calculations that LCNO-III has the most positive d-band center (εd = -0.96 eV vs Fermi level), thus confirming that LCNO-III shows the strongest adsorption ability for N2 molecules (adsorption energy value of -2.01 eV) for the subsequent N2 activation and reduction reactions. Therefore, this work proposes a general rule to adopt for developing novel catalysts (especially perovskite-based catalysts) for substantially increasing the eNRR activity by modulating the corresponding d-band centers.

DFT study of adsorption and diffusion of Mg, K, Ca over monolayer antimonene

Density Functional theory (DFT) based calculations are carried out to investigate adsorption and diffusion properties of Magnesium (Mg), Potassium (K) and Calcium (Ca) over single layer antimony (Sb) i.e. antimonene. Ca has highest value of absolute adsorption energy followed by K and Mg respectively. Charge transfer is greater in case of K adsorbed antimonene as compared to both of the other metals. This affects the electronic properties such as bandstructure and density of states. Antimonene is semiconducting in its pristine form. The adsorption of K leads to a shift to metallic nature, whereas Mg and Ca adsorption still maintain the semiconducting nature after reducing the bandgap. Diffusion of these metals shows that K can easily diffuse through the antimonene surface as compared to the Mg and Ca. The value of diffusion barrier for Mg, K and Ca is 0.30, 0.12 and 0.43 eV respectively. The effective adsorption and charge transfer along with low values of diffusion barrier suggests that phosphorene can be explored further as potential candidate for metal-ion batteries.

Removal of lead ions from aqueous solution using phosphate‐based geopolymer cement composite

AbstractBACKGROUNDWater contaminated by heavy metals has many negative impacts on human health and the environment. According to the UN's sustainable development goals, preserving natural resources will have positive impacts on living conditions by reducing diseases. In this study, a novel adsorbent synthesized from phosphate‐based geopolymer cement composite material was developed and evaluated for lead removal from aqueous solutions. The developed adsorbent is made from natural resources using a facile protocol, and thus it is suitable for both developed and developing countries.RESULTSAnalyses of mineralogical composition, pore‐size distribution and surface of the synthesized phosphate‐based geopolymer cement composite were performed. A microporous structure was observed from the microstructural characterization. Geopolymer cement was immobilized with sodium alginate to fabricate alginate–geopolymer cement beads (Alg/GES). The parameters influencing the adsorption process were investigated in batch mode. The obtained results showed that the adsorption capacity of Pb(II) ions increased with time and equilibrium was reached in 90 min. The optimum adsorption pH was 4.17. The experimental results showed that the adsorption equilibrium of Pb(II) on Alg/GES was well described by the Freundlich and Langmuir models whereas the adsorption rate was well fitted by the pseudo‐second‐order kinetics model. The maximum adsorption capacity obtained from the Langmuir isotherm was qmax = 0.38 mmol g−1. From the Dubinin–Radushkevitch isotherm model, the value of the free adsorption energy was 41 kJ mol−1.CONCLUSIONSCompared with other adsorbents, Alg/GES exhibited a greater adsorption capacity confirming that the phosphate‐based geopolymer cement can be suitable for removal of heavy metals from wastewaters. © 2021 Society of Chemical Industry

Theoretical Framework for Encapsulation of Inorganic B12N12 Nanoclusters with Alkaline Earth Metals for Efficient Hydrogen Adsorption: A Step Forward toward Hydrogen Storage Materials

The increasing demand for energy storage materials has gained considerable attention of scientific community toward the development of hydrogen storage materials. Hydrogen has become more important, as it not only works efficiently in different processes but is also used as an alternative energy resource whenever it is combined with a cell technology like fuel cell. Herein, efforts are being made to develop efficient hydrogen storage materials based on alkaline earth metal (beryllium, magnesium, and calcium)-encapsulated B12N12 nanocages. Quantum chemical calculations were performed using density functional theory (DFT) and time-dependent DFT at B3LYP/6-31G(d,p) and CAM-B3LYP/6-311+G(d,p) levels of theory for all the studied systems. The adsorption energies of Be-B12N12, Mg-B12N12, and Ca-B12N12 systems suggested that Mg and Ca are not fitted accurately in the cavity of nanocages because of their large size. However, H2 adsorbed efficiently on the metal-encapsulated systems with high adsorption energy values. Furthermore, dipole moment and QNBO (Charges-Natural Bond Orbital) calculations suggested that a greater charge separation is seen in H2-adsorbed metal-encapsulated systems. The molecular electrostatic potential analysis also unveiled the different charge sites in the studied systems and also demonstrated the charge separation upon hydrogen adsorption on metal-encapsulated systems. Partial density of states analysis was performed in the support of frontier molecular orbital distribution that indicates the narrow highest occupied molecular orbital-lowest unoccupied molecular orbital energy gap in hydrogen-adsorbed metal-encapsulated systems. Results of all analyses and global descriptions of reactivity suggested that the designed H2-adsorbed metal-encapsulated B12N12 systems are efficient systems for designing future hydrogen storage materials. Thus, these novel kinds of systems for efficient hydrogen storage purposes have been recommended.

The effect of external electric field and metal impurities on the interaction of HF and boraphene: a computational study.

Using density functional theory, the effects of P, Al, and Ga atoms doping on electronic structure of boraphene (B36) were investigated. The results show the highest change in electronic structure of doped-B36 systems belongs to Al-B36 structures wherein the gap energy of the system is decreased by 17.92%. DOS diagrams and absorption spectra of doped B36 are compared to pristine and discussed. The capability of pristine and modified B36 in the field of detection/adsorption of HF molecule has been evaluated. The calculated values of adsorption energies of 0.13, 0.63, 0.24, and 0.16eV for adsorption of HF on pristine, Al-, Ga-, and P-B36 and related DOS diagrams reveal that these systems are not superior host materials for detection/adsorption applications. It was found that the external electric field could increase the interaction between HF and B36 systems leading to suggesting Al-B36 as proper candidate for HF removal applications.

A DFT study of bismuthene as anode material for alkali-metal (Li/Na/K)-ion batteries

The buckled Bismuthene (b-Bi) has attracted the researchers owing to its exceptional properties. The first-principles calculations were utilized to investigate application of b-Bi in lithium-, sodium- and potassium-ion batteries. The respective values of adsorption energies of Li, Na and K atoms were found as −2.70 eV, −2.94 eV and −3.45 eV for b-Bi which point to good stability in the lithiation, sodiation and potassiation processes. The fully lithiated, sodiated and potassiated structures exhibited theoretical capacity of 2276 mAh g−1, 2149 mAh g−1, and 1896 mAh g−1 for Li, Na and K respectively which are higher than that of commercially available graphite anode. The value of diffusion barrier calculated using CI-NEB is reasonably lower than that of contemporary materials. Our findings such as storage capacity, low open circuit voltage (OCV) and diffusion energies are better than the commonly studied 2D materials which makes b-Bi a favorable candidate as an anode material for said rechargeable batteries.

DFT study of the interaction between carbon monoxide and Rh-Cu bimetallic nanoclusters

The interaction between CO and RhxCu4-x(x = 0–4) nanoclusters was studied using B3PW91 hybrid functional. The values of adsorption energies for the most stable structures that were in the range between −1.25 eV to -2.41 eV indicated chemisorption of CO on the clusters along with the formation of chemical bond(s). The nature of these chemical bonds was investigated by NBO analysis and calculation of Wiberg bond indexes as well as considering the change in CO bond length and frequency. It was concluded that the cluster−CO bonds arose mainly from the cluster→(CO) π-back-donation. Also, the NBO analyses revealed that for the adsorption of CO in the bridge and on the top sites, availability of d orbitals and s&p orbitals of cluster atoms was required respectively. Therefore, on the one hand for RhCu3 and Cu4 clusters adsorption in the bridge site was not observed because of the fully occupied d orbitals of Cu atoms but for Rh4, Rh3Cu, and Rh2Cu2 clusters, on the other hand, the adsorption in the bridge of two Rh atoms was the most stable structure. More favorable adsorption on Rh-Cu bimetallic clusters compared to pure Cu4 cluster was also observed.

Statistical physics modeling and interpretation of the adsorption of enantiomeric terpenes onto the human olfactory receptor OR1A1

The statistical physics approach has been well studied by our research team for liquid and gaseous adsorption systems. This treatment is based on the grand canonical partition function to give new interpretations of the adsorption process at molecular level for chemical senses: olfaction and taste. This work represents a contribution to understand the olfaction mechanism of four of enantiomeric terpenes by applying a statistical physics treatment that allows giving a physico-chemical meaning to parameters involved in the analytical model. It is possible to estimate the number of adsorbed molecules per site, the anchorage number, the receptor density, the concentration at half saturation and the molar adsorption energy. Through this selection of the best fitting model and through fitted values of these parameters, we showed that the adsorption of carvone and limonene enantiomers is not a multilayer process but a monolayer monosite process (monolayer adsorption model with identical and independent sites (n ≠ 1)). The physico-chemical model parameters can be used for the energetic characterization of the interactions between the carvone and the limonene enantiomers and the human olfactory receptor OR1A1 and the determination of an olfactory band of order of 14 kJ/mol, 7 kJ/mol, 9 kJ/mol, 8 kJ/mol for (R)-(−)-carvone, (S)-(+)-carvone, (R)-(+)-limonene and (S)-(−)-limonene, respectively, through the determination of the adsorption energy values and the adsorption energy distributions (AEDs).Thanks to the grand canonical formalism in statistical physics, the negative values of the Gibbs free enthalpy indicate that the adsorption process of the four enantiomeric terpenes onto the human olfactory receptor OR1A1 was spontaneous. The exothermic adsorption mechanism involved in the olfactory perception was explained via the negative values of the internal energy.

Hydrogen adsorption and storage on palladium-functionalized graphyne and its boron nitride analogue

This study investigates adsorption of a hydrogen molecule on palladium-functionalized graphyne and its boron nitride analogue using the mPW1PW91 functional. The stability of various isomers of hydrogen adsorption are analyzed. The adsorption energy values are estimated in these systems. Changes in the dipole moment and structural parameters are illustrated. Also, a variation in frontier orbital energy and HOMO—LUMO gap values are revealed. A charge transfer between fragments is exemplified by the electrophilicity-based charge transfer (ECT). Recovery times of the hydrogen molecule in the studied systems are calculated. Also, field emission properties of the studied system are illustrated.

Magnetite-Functionalized Horse Dung Humic Acid (HDHA) for the Uptake of Toxic Lead(II) from Artificial Wastewater

Magnetite-functionalized horse dung humic acid (HDHA) has been successfully prepared by the coprecipitation method, and the as-prepared adsorbent (MHDHA) has been applied as an easy-handling adsorbent for toxic Pb(II) in artificial wastewater. The MHDHA was characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), and vibrating sample magnetometer (VSM). The FT-IR study showed that the MHDHA had the characteristics peaks of HA and Fe-O stretching. The XRD analysis revealed that the MHDHA had the [Formula: see text] characteristic for magnetite. The TEM image and EDX analysis exhibited that the MHDHA with an average size of ∼14 nm was partially aggregated and contained ([Formula: see text]) 9.89% carbon, 2.89% nitrogen, and 32.74% oxygen based on functional groups of HDHA. The stability improvement of MHDHA was showed by decreasing HDHA dissolved from 95% to less than 30% at pH 12 after magnetite functionalization. The post-adsorption handling improvement was evidenced by easy and quick retraction by an external magnet with a 62.95 emu/g magnetic strength value. The adsorption capacities were influenced by the pH and ionic strength, whilst the adsorption rates were well simulated by the Ho pseudo-second-order model. The removal uptake of Pb(II) ions increased when the initial concentration was increased and fitted well with the Langmuir isotherm model when the monolayer adsorption capacity was [Formula: see text] (equal to 57.64 mg/g). The value of Dubinin-Radushkevich adsorption energy ([Formula: see text]) found in this study was 14.78 kJ/mol, which implied that ion exchange is the main mechanism involved in the adsorption process. The regeneration studies of MHDHA show that there was no significant change in composition, morphology, crystallinity, and functional group after five consecutive cycles of the adsorption-desorption process.