Strong Covalent Interactions Research Articles

On the potential of Zn@B38 superatom as a drug delivery vehicle for several anticancer drugs: A DFT study

The interaction between a boron-based Zn@B38 superatom and five drugs, including cisplatin (DDP), 5-fluorouracil (FU), mercaptopurine (MP), hydroxyurea (HU) and nitrogen mustard (CM) have been investigated. The adsorption of these anticancer drugs onto Zn@B38 reduces the energy gap of this superatom. Except for DDP, these drugs exhibit strong covalent interaction with the vertex of Zn@B38 because the lone pair of N/O atom of FU, MP, HU, and CM can fill into the empty atomic orbital of the electron-deficient boron atom of Zn@B38 to form polar covalent bonds, resulting in the charge transfer from drugs to Zn@B38. Hence, the adsorption energies of drug@[Zn@B38] (drug = FU, MP, HU, and CM) are −37.67 ∼ −57.21 kcal/mol, but can be significantly decreased to −8.63 ∼ 5.48 kcal/mol upon protonation, suggesting that these drugs can be efficiently adsorbed by the Zn@B38 carrier in neutral aqueous solution but are easily released in the acidic tumor microenvironment.

Revealing the Critical Role of the Lone Pair Electrons of Bi3+ in Electrocatalytic Oxygen Reduction Reaction on Mn‐Based BiMn2O5 Mullite Surface

AbstractThere is a research gap regarding the role of lone pair electrons of post‐transition metal cations in catalysis field, yet such studies hold significant implications for expanding their applications. Herein, the role of Bi3+ ion lone pair electrons in electrocatalytic oxygen reduction reaction (ORR) is elucidated using ternary mullite oxides as prototype catalysts. Among the three synthesized mullites ((Sm/Y/Bi)Mn2O5), BiMn2O5 exhibits notably superior ORR catalytic activity. Through advanced characterization techniques, including in situ Raman, in situ infrared, and X‐ray absorption spectroscopy, combined with theoretical calculations, it is determined that the superior electrocatalytic performance of BiMn2O5 originates from the lone pair electrons that activate catalytic sites through stereochemical effects. Specifically, the Bi3+ lone pair electrons in the 6s orbital near Fermi level interact with O 2p orbitals, causing a shift of the oxygen ligands, and significant variance in A─O bond lengths. This structural distortion of BiO8 coordination unit directly results in a large Mn─O bond angle at the active center of BiMn2O5 and strong covalent interactions, facilitating charge transfer and refining the adsorption behavior of oxygen intermediates to achieve the overpotential of 0.25 V vs. RHE. This study provides insights into developing next‐generation catalysts by harnessing the lone pair electrons of post‐transition metal cations.

How does the integration of amino acids enhance the bonding ability of triazine-based inhibitors with iron surfaces: Insights from SCC-DFTB, COSMO-RS and molecular dynamics simulations

Theoretical investigations into the adsorption of molecules on metal surfaces play a pivotal role in the development of more efficient corrosion inhibitors. This study offers a novel approach by combining Density Functional Tight Binding (DFTB), Molecular Dynamics (MD) simulations, and conductor-like screening model for realistic solvation (COSMO-RS) calculations to comprehensively assess the interaction and diffusion properties of glycine (Gly), 2,2′-azanediyldiacetic acid (IDA), and 5-aminopentanoic acid (5-APA) with two 1,3,5-triazine (Tris) derivatives (Tris-Gly and Tris-IDA) for corrosion protection of carbon steel in acidic medium. The solvation properties of these molecules were evaluated alongside their interaction strength with the Fe(1 1 0) surface, considering both neutral and protonated forms. DFTB simulations revealed a clear trend in interaction energies, following the order: Tris-IDA > Tris-Gly > 5-APA > IDA > Gly. It ranges from −1.191 eV to −1.853 eV, with the highest stability observed for protonated Tris-IDA (−1.853 eV), while protonated Glycine exhibits the lowest interaction energy (−1.191 eV). These theoretical results diverged slightly from experimental observations, with Tris-Gly outperforming Tris-IDA, which was attributed to steric effects and solvent interactions. The DFTB results also indicated strong covalent interactions, particularly involving acetic groups, between the inhibitors’ orbitals and the iron’s 3d orbitals. MD simulations further demonstrated the impact of protonation on inhibitor mobility, with reduced diffusion coefficients due to enhanced electrostatic interactions and hydrogen bonding. COSMO-RS solvation analysis confirmed the strong hydrogen bonding capabilities of these molecules with water. Overall, this study elucidates the mechanisms of corrosion inhibition by integrating multiple simulation techniques, providing key molecular insights that can guide the design of more effective corrosion inhibitors. The findings emphasize the significance of electronic interactions and molecular structure in enhancing inhibitor performance, making this a valuable contribution to corrosion science.

Bimetallic metal organic frameworks-based nanozyme for colorimetry/fluorescence dual-mode uremic toxin detection

Chronic kidney disease (CKD) can greatly increase the mortality risk for clinical patients, with a major challenge being the accurate detection of uremic toxins. Metal organic frameworks (MOFs)-based colorimetry/fluorescence dual-mode probe have shown great potential for bio-detection. However, one of the challenges for MOFs-based nanoprobe is to effectively improve the activity of mimetic enzymes for colorimetric assays while maintaining their outstanding luminescence response for fluorescence sensing. Here, we developed a novel bimetallic Zr/Ce-MOFs, which possesses high catalytic activity and excellent luminescence properties for dual-mode sensing of uremic toxins. The co-existence of Ce and Zr in the MOFs improves the catalytic activity for colorimetric detection of phosphate ions (one type of uremic toxins) and the strong coordinate covalent interaction between phosphate ions and Zr/Ce leads to a significant fluorescence enhancement of the MOFs. Furthermore, we achieved high sensitivity phosphate ions analysis in serum samples. This strategy provides an easy and reliable platform for the detection of uremic toxins in complicated physiological environment.

Bi-intercalated epitaxial graphene on SiC(0001)

Abstract The intercalation of graphene with suitable atomic species is one of the most frequently applied methods to decouple the graphene layer from the substrate in order to establish the classical electronic properties of graphene. In this context, we studied the bismuth (Bi) intercalation of the (6√3×6√3)R30° reconstructed so-called "zeroth layer graphene'' on SiC(0001). 
As reported earlier by Sohn et al. [J. Korean Phys. Soc. 78, 157 (2021)], two phases are formed depending on the amount of intercalated Bi, which in turn is controlled by the annealing temperature: The α phase, showing a 1×1 periodicity with respect to the substrate, and, at higher temperatures, the √3×√3 reconstructed β phase. We characterise both phases and the transformation from the α to the β phase by photoelectron spectroscopy, normal incidence x-ray standing waves, electron diffraction and electron microscopy. We clearly see an almost complete intercalation of the graphene layers in both phases, with strong (covalent) interaction between the topmost Si atoms of the substrate and the Bi intercalant, but only weak (van der Waals) interaction between Bi and the graphene layer. The n-doping of the graphene found for the α phase decreases continuously during the phase transformation, in agreement with a reduced density of the Bi intercalating layer. Missing core level shifts of the surface species as well as the normal incidence x-ray standing waves results indicate that all surface Si atoms remain saturated during the transition and no dangling bonds are formed. Low energy electron microscopy and diffraction reveal the coexistance of both phases after annealing to intermediate temperatures and allow a quantitative analysis of island sizes and numbers.

Covalent-Organic Frameworks for Selective and Sensitive Detection of Antibiotics from Water.

As the consumption of antibiotics rises, they have generated some negative impacts on organisms and the environment because they are often unable to be effectively degraded, and seeking effective detection methods is currently a challenge. Covalent-organic frameworks (COFs) are new types of crystalline porous crystals created based on the strong covalent interactions between blocked monomers, and COFs demonstrate great potential in the detection of antibiotics from aqueous solutions because of their large surface area, adjustable porosity, recyclability, and predictable structure. This review aims to present state-of-the-art insights into COFs (properties, classification, synthesis methods, and functionalization). The key mechanisms for the detection of antibiotics and the application performance of COFs in the detection of antibiotics from water are also discussed, followed by the challenges and opportunities for COFs in future research.

Strong yet Tough Catalyst-Free Transesterification Vitrimer with Excellent Fire-Retardancy, Durability, and Closed-Loop Recyclability.

Despite great advances in vitrimer, it remains highly challenging to achieve a property portfolio of excellent mechanical properties, desired durability, and high fire safety. Thus, a catalyst-free, closed-loop recyclable transesterification vitrimer (TPN1.50) with superior mechanical properties, durability, and fire retardancy is developed by introducing a rationally designed tertiary amine/phosphorus-containing reactive oligomer (TPN) into epoxy resin (EP). Because of strong covalent interactions between TPN and EP and its linear oligomer structure, as-prepared TPN1.50 achieves a tensile strength of 86.2MPa and a toughness of 6.8MJm-3, superior to previous vitrimer counterparts. TPN1.50 containing 1.50 wt% phosphorus shows desirable fire retardancy, including a limiting oxygen index of 35.2% and a vertical burning (UL-94) V-0 classification. TPN1.50 features great durability and can maintain its structure integrity in 1M HCl or NaOH solution for 100 days. This is because the tertiary amines are anchored within the cross-linked network and blocked by rigid P-containing groups, thus effectively suppressing the transesterification. Owing to its good chemical recovery, TPN1.50 can be used as a promising resin for creating recyclable carbon fiber-reinforced polymer composites. This work offers a promising integrated method for creating robust durable fire-safe vitrimers which facilitate the sustainable development of high-performance polymer composites.

First-principles calculations of the mechanical properties of Mg2Si intermetallic via ternary elements doping

Abstract Site preference, structural stability and mechanical properties of Mg2Si doped by ternary elements were studied by first-principles calculation. Formation enthalpies show that light element impurity Al and rare earth elements Sc and Y tend to occupy the Mg site, while transition element Cu has a preference for the Si site. Shear modulus to bulk modulus ratio (G/B), Poisson’s ratio ν and Cauchy pressure show that the ductility of Mg2Si is improved for ternary element addition. The introduced parameter of ductility factor D indicates that the enhanced dislocation emission but suppressed micro-crack propagation is the key to enhancing ductility. Electronic structure indicates the brittleness is due to the strong covalent interaction between Mg-2p and Si-3p (Mg-3s and Si-3p/3s). While, with the incorporation of alloying elements, abundant electrons are injected into the matrix Mg2Si. Thereby, the covalent interaction is effectively suppressed and the ductility is improved.

Semimetal-triggered covalent interaction in Pt-based intermetallics for fuel-cell electrocatalysis.

Platinum-based intermetallic compounds (IMCs) play a vital role as electrocatalysts in a range of energy and environmental technologies, such as proton exchange membrane fuel cells. However, the synthesis of IMCs necessitates recombination of ordered Pt-M metallic bonds with high temperature driving, which is generally accompanied by side effects for catalysts' structure and performance. In this work, we highlight that semimetal atoms can trigger covalent interactions to break the synthesis-temperature limitation of platinum-based intermetallic compounds and benefit fuel-cell electrocatalysis. Attributed to partial fillings of p-block in semimetal elements, the strong covalent interaction of d-p π backbonding can benefit the recombination of ordered Pt-M metallic bonds (PtGe, PtSb and PtTe) in the synthesis process. Moreover, this covalent interaction in metallic states can further promote both electron transport and orbital fillings of active sites in fuel cells. The semimetal-Pt IMCs were obtained with a temperature 300K lower than that needed for the synthesis of metal-Pt intermetallic compounds and reached the highest CO-tolerant oxygen reduction activity (0.794 A mg-1 at 0.9V and 5.1% decay under CO poisoning) among reported electrocatalysts. We anticipate that semimetal-Pt IMCs will offer new insights for the rational design of advanced electrocatalysts for fuel cells.

Fluorinated Fullerenes as Electrolyte Additives for High Ionic Conductivity Lithium-Ion Batteries.

Currently, lithium-ion batteries have an increasingly urgent need for high-performance electrolytes, and additives are highly valued for their convenience and cost-effectiveness features. In this work, the feasibilities of fullerenes and fluorinated fullerenes as typical bis(fluorosulfonyl)imide/1,2-dimethoxymethane (LiFSI/DME) electrolyte additives are rationally evaluated based on density functional theory calculations and molecular dynamic simulations. Interestingly, electronic structures of C60, C60F2, C60F4, C60F6, 1-C60F8, and 2-C60F8 are found to be compatible with the properties required as additives. It is noted that that different numbers and positions of F atoms lead to changes in the deformation and electronic properties of fullerenes. The F atoms not only show strong covalent interactions with C cages, but also affect the C-C covalent interaction in C cages. In addition, molecular dynamic simulations unravel that the addition of trace amounts of C60F4, C60F6, and 2-C60F8 can effectively enhance the Li+ mobility in LiFSI/DME electrolytes. The results expand the range of applications for fullerenes and their derivatives and shed light on the research into novel additives for high-performance electrolytes.

An efficient method to prepare high grafting montmorillonite with silane coupling agent and its improvements for styrene butadiene rubber composites

AbstractThe quantity of silane chemically bonded to the organoclay's surface significantly influences its dispersion within the polymer matrix, as well as the interfacial interaction. This research presents a groundbreaking method for enhancing the surface properties of montmorillonite (Mt) through the use of γ‐(methacryloxy) propyl trimethoxy silane (KH570) coupled with acid treatment, leading to increased grafting efficiency. Confirmed by FT‐IR, TGA, and XRD, the process effectively bonds organo‐silanes to Mt and achieves a high grafting level of 1.59 mequiv/g. Utilizing a latex compounding method, Mt/rubber nanocomposites are synthesized with thoroughly modified clay for peak performance. Dispersion and interfacial properties are evaluated through XRD, TEM, AFM, and DMTA. The findings reveal that the well‐modified Mt is an exceptional filler, ensuring a high level of dispersion and robust interaction with the rubber matrix. This synergy translates to a marked improvement in the mechanical properties of the composite, with notable enhancements observed in both tensile strength and elongation at break of 9.7 MPa and 1141%, respectively. This innovative approach to the graft modification of clays presents a potent method, offering the potential for the industrial‐scale manufacture of high‐performance clay‐based composites.Highlights A processing method for preparing high grafting clay with a silane coupling agent. Functionalized clay presents better nano‐dispersion in the polymeric matrix. Strong covalent interfacial interaction is constructed between clay and rubber. Tensile Strength and elongation at break of the composites are obliviously improved.

Interlayer Potassium Single-Atom-Coordinated g-C3N4 for Significantly Boosted Visible Light Photocatalytic H2 Production.

In recent years, graphitic carbon nitride (g-C3N4) has attracted considerable attention because it includes earth-abundant carbon and nitrogen elements and exhibits good chemical and thermal stability owing to the strong covalent interaction in its conjugated layer structure. However, bulk g-C3N4 has some disadvantages of low specific surface area, poor light absorption, rapid recombination of photogenerated charge carriers, and insufficient active sites, which hinder its practical applications. In this study, we design and synthesize potassium single-atom (K SAs)-doped g-C3N4 porous nanosheets (CM-KX, where X represents the mass of KHP added) via supramolecular self-assembling and chemical cross-linking copolymerization strategies. The results show that the utilization of supramolecules as precursors can produce g-C3N4 nanosheets with reduced thickness, increased surface area, and abundant mesopores. In addition, the intercalation of K atoms within the g-C3N4 nitrogen pots through the formation of K-N bonds results in the reduction of the band gap and expansion of the visible-light absorption range. The optimized K-doped CM-K12 nanosheets achieve a specific surface area of 127 m2 g-1, which is 11.4 times larger than that of the pristine g-C3N4 nanosheets. Furthermore, the optimal CM-K12 sample exhibits the maximum H2 production rate of 127.78 μmol h-1 under visible light (λ ≥ 420 nm), which is nearly 23 times higher than that of bare g-C3N4. This significant improvement of photocatalytic activity is attributed to the synergistic effects of the mesoporous structure and K SAs doping, which effectively increase the specific surface area, improve the visible-light absorption capacity, and facilitate the separation and transfer of photogenerated electron-hole pairs. Besides, the optimal sample shows good chemical stability for 20 h in the recycling experiments. Density functional theory calculations confirm that the introduction of K SAs significantly boosts the adsorption energy for water and decreases the activation energy barrier for the reduction of water to hydrogen.

Unlocking highly stable and reversible in-situ integration of defect-rich 2D vanadium sulfide with Ti3C2Tx MXene heterostructures: Boosting asymmetric supercapacitor performance

To broaden the functionalities of transition metal dichalcogenides and two-dimensional transition metal carbides such as MXenes (Ti3C2Tx-MX), it is necessary to appropriately integrate them with each other to form heterostructures. The integrated heterostructures should maintain functionality through strong covalent interaction and offer excellent electrochemical properties. The requirement for developing appropriately integrated heterostructures is the control of nucleation and growth by governing the reaction kinetics. However, developing heterostructures over MXenes on a large scale is extremely challenging. Herein, we propose an investigation to elucidate the formation of defect-rich conductive heterostructures by in-situ integration of vanadium sulfide (VS2) on the surface of Ti3C2Tx-MX (VS2–Ti3C2Tx-MX) via controlled nucleation and growth in a facile hydrothermal process. The scrutinized binder-free flexible fabric-based VS2–Ti3C2Tx-MX0.25 electrode exhibits an excellent specific capacitance of 750 F g−1 and long-term stability (∼93 % retention after 10000 cycles). Moreover, these defect-rich and interlayer-expanded integrated heterostructures showed exceptional cycling stability and an impressive energy density of 52.08 Wh kg−1 at a power density of 750 W kg−1 when employed as fabric-based asymmetric supercapacitor (ASC) devices with VS2–Ti3C2Tx-MX0.25//Ti3C2Tx-MX configuration. We anticipate that the approach presented in this work will promote the development of various MXene-based heterostructures for manipulating the versatile properties of MXenes and VS2 in energy storage applications.

DFT Calculations on Defect Induced and Doped ASiNR for Sensing the COPD Breath Biomarker

COPD is a respiratory disease with a high mortality rate worldwide. The major cause of death in COPD patients is due to late diagnosis. Early detection of COPD is crucial for significantly reducing the risk of death but is challenging to attain. A distinguished way to early diagnosis is by using the nanosensor for sensing the COPD breath biomarkers. For the first time, we report an armchair silicene nanoribbon (ASiNR) as a promising sensing material for the diagnosis of hexanal a COPD breath biomarker. In this present study, the density functional theory (DFT) with Grimme D2 corrected approach was incorporated to observe the ground state electronic properties and adsorption mechanism of hexanal on the pristine, defect induced (D) and B, C, and N-doped ASiNR systems. N-ASiNR systems show the highest adsorption energy value among previously reported works due to the presence of strong covalent interaction, and it does not show recovery at room temperature. The B-ASiNR system with higher charge transfer exhibits large work function change with the fastest recovery at room temperature in 1.81 s. Our results confirms B-doped ASiNR system acts as an efficient reusable work function-based sensor for the early diagnosis of COPD at room temperature.

Highly Active and Sintering-Resistant Pt Clusters Supported on FeOx-Hydroxyapatite Achieved by Tailoring Strong Metal-Support Interactions.

The catalytic performance of supported metal catalysts is closely related to their structure. While Pt-based catalysts are widely used in many catalytic reactions because of their exceptional intrinsic activity, they tend to deactivate in high-temperature reactions, requiring a tedious and expensive regeneration process. The strong metal-support interaction (SMSI) is a promising strategy to improve the stability of supported metal nanoparticles, but often at the price of the activity due to either the coverage of the active sites by support overlay and/or the too-strong metal-support bonding. Herein, we newly constructed a supported Pt cluster catalyst by introducing FeOx into hydroxyapatite (HAP) support to fine-tune the SMSIs. The catalyst exhibited not only high catalytic activity but also sintering resistance, without deactivation in a 100 h test for catalytic CO oxidation. Detailed characterizations reveal that FeOx introduced into HAP weaken the strong covalent metal-support interaction (CMSI) between Pt and FeOx while simultaneously inhibiting the oxidative strong metal-support interaction (OMSI) between Pt and HAP, giving rise to both high activity and thermal stability of the supported Pt clusters.

Highly Dense N-N-Bridged Dinitramino Bistriazole-Based 3D Metal-Organic Frameworks with Balanced Outstanding Energetic Performance.

Due to the inherent conflict between energy and safety, the construction of energetic materials or energetic metal-organic frameworks (E-MOFs) with balanced thermal stability, sensitivity, and high detonation performance is challenging for chemists worldwide. In this regard, in recent times self-assembly of energetic ligands (high nitrogen- and oxygen-containing small molecules) with alkali metals were probed as a promising strategy to build high-energy materials with excellent density, insensitivity, stability, and detonation performance. Herein, based on the nitrogen-rich N,N'-([4,4'-bi(1,2,4-triazole)]-3,3'-dial)dinitramide (H2BDNBT) energetic ligand, two new environmentally benign E-MOFs including potassium [K2BDNBT]n (K-MOF) and sodium [Na2BDNBT]n (Na-MOF) have been introduced and characterized by NMR, IR, TGA-DSC, ICP-MS, PXRD, elemental analyses, and SCXRD. Interestingly, Na-MOF and K-MOF demonstrate solvent-free 3D dense frameworks having crystal densities of 2.16 and 2.14 g cm-3, respectively. Both the E-MOFs show high detonation velocity (VOD) of 8557-9724 m/s, detonation pressure (DP) of 30.41-36.97 GPa, positive heat of formation of 122.52-242.25 kJ mol-1, and insensitivity to mechanical stimuli such as impact and friction (IS = 30-40 J, FS > 360 N). Among them, Na-MOF has a detonation velocity (9724 m/s) superior to that of conventional explosives. Additionally, both the E-MOFs are highly heat-resistant, having higher decomposition (319 °C for K-MOF and 293 °C for Na-MOF) than the traditional explosives RDX (210 °C), HMX (279 °C), and CL-20 (221 °C). This stability is ascribed to the extensive structure and strong covalent interactions between BDNBT2- and K(I)/Na(I) ions. To the best of our knowledge, for the first time, we report dinitramino-based E-MOFs as highly stable secondary explosives, and Na-MOF may serve as a promising next-generation high-energy-density material for the replacement of presently used secondary thermally stable energetic materials such as RDX, HNS, HMX, and CL-20.

Local spatial polarization induced efficient electron transfer in fluorinated borocarbonitride for boosting CO2 photoreduction

CO2 photoreduction into highly value-added chemicals over metal-free h-BCN has emerged as a promising strategy to address the issue of global warming. However, the serious carrier recombination caused by disordered charger transfer has limited its practical application. To circumvent this issue, fluorine modified h-BCN were synthesized using a facile heat treatment method. The surface halogenation created local spatial polarized electric field, which facilitated the local charge separation and transmission efficiency. Among them, BCN-F-4 exhibited the best photocatalytic CO2 reduction activitiy with CO and CH4 yield of 25.38 and 14.11 µmol g−1h−1, respectively. The turnover number (TON) of BCN-F-4 reached up to 163.6 μmol g−1h−1, 4.4 times that of BCN. Both theoretical simulation and experimental analysis demonstrated a strong covalent interaction between the F atoms and the h-BCN matrix, which gain deep understanding of the mechanism of prominent photocatalytic CO2 reduction activity boosted by surface halogenation.

Reaction solution mediated photo-degradation process and mechanism of tetracycline via semiconductor-insulator composite ZnO:N-BaSO4

Research in contaminants photo-degradation has witnessed significant progress, recently insulator-based catalysts gaining prominence. In this study, N-containing p-type ZnO decorated BaSO4 (ZnO:N-BaSO4) were synthesized and presented a pseudo-first-order kinetic constant of 1.30 × 10−2 min−1 for TC degradation, surpassing that of ZnO:N and their physical mixture by four and seven-fold, respectively. Impressively, the electron transfer in ZnO:N/TC solution interface led to band bending on ZnO:N surface and realized the band matching between ZnO:N and BaSO4. Density functional theory (DFT) calculations unveiled that the strong Zn-O covalent interaction involving 4s states of Zn atoms and 2p states of O atoms, established a distinctive pathway for electron transfer from semiconductor to insulator. Moreover, the catalysts demonstrated robust activity and sustained long-term stability in real wastewater and surface water. This research illuminates the role of wastewater redox potential in semiconductor band adjustment and highlights abundant, eco-friendly insulators as co-catalysts for selective photo-degradation.

Phosphorus-doped T-graphene nanocapsule toward O3 and SO2 gas sensing: a DFT and QTAIM analysis

Tetragonal graphene nano-capsule (TGC), a novel stable carbon allotrope of sp2 hybridization is designed and doped with phosphorus (P) to study the O3 and SO2 gas sensitivity via density functional theory calculation. Real frequencies verified the natural existence of both TGC and P-doped TGC (PTGC). Both TGC and PTGC suffer structural deformations due to interaction with O3 and SO2 gases. The amount of charge transfer from the adsorbent to the gas molecule is significantly greater for O3 adsorption than SO2 adsorption. The adsorption energies for TGC + O3 and PTGC + O3 complexes are − 3.46 and − 4.34 eV respectively, whereas for TGC + SO2 and PTGC + SO2 complexes the value decreased to − 0.29 and − 0.30 eV respectively. The dissociation of O3 is observed via interaction with PTGC. A significant variation in electronic energy gap and conductivity results from gas adsorption which can provide efficient electrical responses via gas adsorption. The blue/red shift in the optical response proved to be a way of detecting the types of adsorbed gases. The adsorption of O3 is exothermic and spontaneous whereas the adsorption of SO2 is endothermic and non-spontaneous. The negative change in entropy verifies the thermodynamic stability of all the complexes. QTAIM analysis reveals strong covalent or partial covalent interactions between absorbent and adsorbate. The significant variation in electrical and optical response with optimal adsorbent-gas interaction strength makes both TGC and PTGC promising candidates for O3 and SO2 sensing.

Redox assisted solvent extraction to enable highly efficient separation of cerium from other lanthanides: Experimental studies and DFT calculations

Cerium (Ce) has become an important strategic resource in high-tech fields owing to its excellent optical, magnetic, acoustic, and electrical properties. The recovery of non-natural Ce derived from nuclear fission through spent fuel reprocessing is of potential significance for the reservation of extremely precious resources. In the present work, Ce3+ was oxidized to Ce4+ by NaBiO3 and then extracted by alkyl phosphate ligands. The extraction efficiency can be enhanced by increasing acidity, raising extractant concentration and decreasing temperature. By taking the advantage of the intrinsic selectivity to tetravalent lanthanides (Ln) by alkyl phosphates, highly efficient and selective extraction of Ce4+ from other trivalent lanthanides with remarkable separation factor (SF) over 103 was achieved. Meanwhile, the back extraction of Ce could be accomplished through reducing Ce4+ to Ce3+ by H2O2. Further studies on structure-property relationship by spectroscopic methods and DFT calculations revealed that alkyl substituent groups with more C atoms enhanced the complexation between Ce4+ and the ligand, while steric hindrance effect could weaken the extractability of Ce4+. Moreover, a shorter CeO bond and a stronger covalent interaction in the Ce4+ complex, as compared to the Ln3+ complex, contributed to the excellent selectivity to Ce4+ over Ln3+.