Dissociation Energy Research Articles

Nanomaterials as medicinal gas sensors described by density functional theory: a comprehensive review.

Using medical gas detectors offers a promising and non-invasive approach for the early identification of diseases. This technique provides a less painful and more accessible alternative to traditional diagnostic methods. In the development of these new detection methods, the use of nanomaterials as gas sensors has proven advantageous due to their large surface areas, which enhance reactivity and sensitivity in identifying volatile compounds. To evaluate the behavior of nanomaterials when in contact with medical gases, ab initio computational simulations based on density functional theory have shown to be effective. This literature review presents studies that have applied density functional theory to investigate intermolecular interactions between specific nanosystems and gases, such as toluene, hydrogen sulfide, ammonia, and nitric oxide. These studies have yielded promising results related to adsorption and dissociation energies, electronic properties, energy gaps, bond lengths, and charge transfer, suggesting the potential of nanomaterials as effective sensors for medical gas detection.

Computational Study of the Gas-Phase Thermal Degradation and the Reaction Rate Coefficients of Perfluoroalkyl Ether Carboxylic Acids.

Perfluoroalkyl ether carboxylic acids (PFECA), which are replacements for legacy per- and polyfluorinated alkyl substances (PFAS), exhibit undesirable properties and often require thermal remediation. Detailed kinetic evaluation of the pyrolysis of PFECA was achieved computationally using density functional ωB97xD/6-311+G (d,p) to establish homolytic bond dissociation energies for the carboxylic acid and carboxylate forms of ∼90-100 kcal/mol and as low as 65 ± 3 kcal/mol, respectively. The negatively charged oxygenated radical products collapse with activation energies (Ea) of Ea(β-scission) ∼ 12-42 kcal/mol, Ea(1,2-F-shift) ∼ 24-47 kcal/mol, and Ea(oxygen atom-shift) ∼ 33-35 kcal/mol and enthalpies (ΔH) of ΔH(F-loss) ∼ 56-71 kcal/mol. The perfluoroalkoxyl radical intermediates transform via Ea(β scission) ∼ 2-9 kcal/mol and Ea(F-loss) ∼ 25-43 kcal/mol. The radical intermediates have lifetimes in the microsecond-to-nanosecond range at 1000 K and 1 atm, with some radicals stable for hours or even days with respect to the unimolecular processes. The results provide new fundamental thermodynamic and kinetic parameters for the partitioning of the degradation pathways of PFECA and establish specific structure-activity relationships of intermediates, leading to the final degradation products. These results are critical for modeling the thermal treatment of PFECA and related PFAS.

Rational Design for Antioxidant Diphenylamine Derivatives Using Quantitative Structure-Activity Relationships andQuantum Mechanics Calculations.

Diphenylamine (DPA) derivatives, used as antioxidants in rubber-based products, inhibit autoxidation by donating hydrogen atoms to peroxyl radicals. Octanol-water partition coefficient (LogKow), an antioxidant index, helps predict their distribution in hydrophobic polymer matrices. Therefore, this study aimed to investigate the relationship between the structure of DPA derivatives and their antioxidant activities, using machine learning with quantitative structure-activity relationships (QSAR) and quantum mechanics (QM). The structure of DPA derivatives was optimized using Density Functional Theory and analyzed for molecular properties. The QSAR models were trained using important descriptors identified through permutation importance. Among the models developed, the Gradient Boosting Regressor (GBR) showed the best performance, with R2 of 0.983 and root mean square error (RMSE) of 0.642 for the test set. SHAP analysis revealed that molecular weight and electronic properties significantly influenced LogKow predictions. For instance, a higher molecular weight was associated with increased LogKow, and a higher positive charge of C2 correlated with higher LogKow predictions. Consequently, the two potent compounds (D1 and D2) were designed based on QSAR model guidance. The GBR model predicted LogKow values of 9.789 and 7.102 for D1 and D2, respectively, which are higher than the training compounds in the model. To gain molecular insight, the quantum chemical calculations with M062X/6-311++G(d,p)//M062X/6-31G(d,p) were performed to investigate the bond dissociation enthalpy (BDE). The results showed that D1 (79.50 kcal/mol) and D2 (72.43 kcal/mol) exhibited lower BDEs than the reference compounds, suggesting that the designed compounds have the potential for enhanced antioxidant activity. In addition, the antioxidant reaction mechanism was studied by using M062X/6-311++G(d,p)//M062X/6-31G(d,p) which found that the hydrogen atom transfer is the key step, where D1 and D2 showed activation energy barriers of 10.38 and 6.29 kcal/mol, respectively, compared to reference compounds of R3 (10.39 kcal/mol), R1 (10.40 kcal/mol), and R2 (18.26 kcal/mol). Therefore, our findings demonstrate that integrating QSAR with quantum chemical calculations can effectively guide the design of DPA derivatives with improved antioxidant properties.

Cation-π Bonding in Actinides: UOx+(Benzene) (x = 0, 1, 2) Complexes Studied with Threshold Photodissociation Spectroscopy and Theory.

Cation-π complexes of the form UOx+(benzene) (x = 0, 1, 2) are produced by laser vaporization and cooled in a supersonic molecular beam. These ions are mass selected and studied with UV-visible laser photodissociation spectroscopy. Each of these complexes photodissociates by elimination of the benzene ligand. Above an energetic threshold, the absorption and photodissociation are continuous, indicating a high density of strongly coupled electronic states. The thresholds for the dissociation of each of these three complexes are measured and assigned as their respective bond dissociation energies. The bond energies determined [U+-(benzene): 42.5 ± 0.3 kcal/mol; UO+-(benzene): 41.0 ± 0.3 kcal/mol; UO2+-(benzene): 39.7 ± 0.3 kcal/mol] are comparable to those of transition metal ion-benzene complexes. Computational studies at the DFT/B3LYP level complement the experiments, predicting dissociation energies in reasonably good agreement with the experiments. Experiments and theory agree that the U+(benzene) complex is more strongly bound than its corresponding oxide ions. This new thermochemistry on actinide cation-π bonding should stimulate higher-level computational studies on these systems.

Non-Born-Oppenheimer Electronic Structure and Relativistic Effects in the Ground States of BH and BH.

In this work, we report benchmark variational calculations for the boron monohydride (BH) molecule and its cation (BH+). The solutions to the nonrelativistic Schrödinger equations for these systems are obtained using a variational method without assuming the Born-Oppenheimer (BO) approximation, which separates electronic and nuclear motions. The ground-state wave functions for both the eight-particle (two nuclei and six electrons) BH molecule and the seven-particle (two nuclei and five electrons) BH+ ion are expanded in terms of all-particle explicitly correlated Gaussian with prefactors that effectively capture nucleus-nucleus correlation effects. These nonrelativistic non-BO wave functions are used to compute leading-order relativistic corrections to the total energies via perturbation theory, as well as to estimate leading-order quantum electrodynamics (QED) effects. The resulting total, dissociation, and ionization energies of BH represent the most accurate rigorously obtained theoretical values to date.

Molecular Evolution of Target Organosulfur Enables High-Performance Aqueous Zinc Batteries.

Organic cathode materials for aqueous zinc-ion batteries (AZIBs) have garnered significant attention due to their environmental friendliness and structurally customizable nature. However, the low voltage, sluggish redox kinetics, and high solubility of most n-type cathode materials hinder their wide deployment. To overcome these challenges, through molecular evolution, we rationally select a cheap industrial material, organodisulfide 2,2'-dithiobis (benzothiazole) (MBTS), as an n-type cathode material for AZIBs. Due to the presence of N-containing benzothiazole rings, the dissociation energy of the sulfur-sulfur (S-S) bond is reduced, substantially enhancing the discharge voltage and improving the reaction kinetics. They regulate the π-conjugated plane to achieve a low solubility and fast charge transfer. Moreover, density functional theory (DFT) calculations elucidate the synergistic effect between adjacent active sites and Zn2+ storage reactions, revealing that the formation of weak coordination bonds between N and Zn atoms (N-Zn-S bond) reduces the solubility of the discharge product. Molecular evolution has led to the fast reaction kinetics of zinc ion storage, thus achieving a high performance under high mass loading. At a current density of 0.05 A g-1, MBTS exhibits an average discharge voltage of 1.02 V, with a mere overpotential of 100 mV, and delivers a high specific capacity of 153.6 mAh g-1. The assembled pouch cell demonstrates an excellent rate capability of 124.4 mAh g-1 at 1 A g-1 and displays a stable cycle life after 200 cycles with 96.8% capacity retention. Remarkably, MBTS maintains high specific capacity and favorable cycle stability under various ultrahigh loadings, up to 18.2 mg cm-2. The findings provide substantial guidance for practical applications of organic electrode materials in AZIBs.

Understanding key interactions between NOx and C2-C5 alkanes and alkenes: The ab initio kinetics and influences of H-atom abstractions by NO2

This study aims to reveal the important role and the respective rate rules of H-atom abstractions by NO2 for better understanding NOX/hydrocarbon interactions. To this end, H-atom abstractions from C2-C5 alkanes and alkenes (15 species) by NO2, leading to the formation of three HNO2 isomers (trans-HONO, HNO2, and cis-HONO) and their respective products (45 reactions), are first characterized through quantum chemistry computation, where electronic structures, single point energies, C-H bond dissociation energies and 1-D hindered rotor potentials are determined at DLPNO-CCSD(T)/cc-pVDZ//M06–2X/6−311++g(d,p). The rate coefficients for all studied reactions, over a temperature range from 298.15 to 2000 K, are computed using transition state theory with the Master Equation System Solver program. Comprehensive analysis of branching ratios elucidates the diversity and similarities between different species, HNO2 isomers, and abstraction sites, from which accurate rate rules are determined. With the rate rules, the rate coefficients at various reaction sites on heavier hydrocarbons (e.g., > C5) can be reliably estimated by analogy. Incorporating the updated rate parameters into a detailed chemical kinetic model reveals the significant influences of this type of reaction on model prediction results, where the simulated ignition delay times are either prolonged or reduced, depending on the original rate parameters presented in the selected model. Sensitivity and flux analysis further highlight the critical role of this type of reaction in affecting system reactivity and reaction pathways, emphasizing the need for adequately representing these kinetics in existing chemistry models. This can now be sufficiently achieved for alkanes and alkenes based on the results from this study.

Z-scheme H5PMo10V2O40/g-C3N4 heterojunction with strong photooxidative capacity for promoting efficient cleavage of Cα-Cβ bond in lignin models and lignin.

The efficient photocatalytic breakage of Cα-Cβ bonds has great significance for the valorization of lignin into value-added aromatic chemicals, but remains challenging owing to their demanding depolymerization conditions and high bond dissociation energies. In this study, the Z-scheme heterojunction H5PMo10V2O40/g-C3N4 (HPA/CN) photocatalyst was elaborately developed for the selective and efficient cleaving of Cα-Cβ bonds in real lignin and its β-O-4 models under mild conditions. The construction of Z-scheme heterojunction with irregular sheet micromorphology not only enhanced the charge separation and redox abilities, but also broadened the light absorption range and promoted charge-to-surface transfer in two redox components. Notably, 35% HPA/CN could completely convert the 2-phenoxy-1-phenylethanol with Cα-Cβ bond cleavage selectivity of 97.4%, achieving approximately 50.0- and 2.2-times higher conversion rates compared to HPA and CN, respectively. Meanwhile, this strategy also offered a wide substrate scope containing various β-O-4 model compounds and native lignin, leading to the generation of corresponding aromatics. The mechanism experiments revealed that photoinduced holes and superoxide radicals synergistically triggered the oxidative cleavage of Cα-Cβ bond. This study could provide a reference for photocatalytic production of value-added aromatic monomers by exploiting both renewable feedstocks and solar energy.

Physical, structural and elastic properties of Fe2O3-doped oxyfluoroborate glasses

A series of Fe2O3-doped oxyfluoroborate 75B2O3–20NaF–5BaO glasses (Fe2O3 = 0, 2, 4, and 6 mol) were synthesized using the conventional melt-quenching method. The effect of Fe2O3 on the physical, structural, and elastic characteristics of synthesized glass samples has been studied. The non-crystalline characteristics of the prepared glass samples were validated through XRD analysis, while their structural properties were examined using FTIR spectroscopy. Elastic properties were investigated through the measurement of longitudinal and shear ultrasonic velocities, employing the pulse-echo technique. The observed density and computed molar volume were determined to be influenced by the content of Fe2O3. The ultrasonic velocities, elastic moduli, micro-hardness, and Debye temperature exhibited similar behavior across all glass compositions, showing an increase with increasing Fe2O3 content. The findings are analyzed concerning the alteration in the topology of the borate network. The incorporation of Fe2O3 led to the transformation of BO3 structural groups into BO4 structural groups, enhancing the network connectivity and increasing the rigidity of the glass structure and elastic moduli. A variety of compositional parameters, including the average separation between boron ions, mean atomic volume, glass packing density, dissociation energy per unit volume, and excess molar volume, were assessed in concerning Fe2O3 content. These parameters were then correlated with the elastic properties, drawing on established models and theories within the discipline. The theoretical elastic moduli, micro-hardness, and Poisson's ratio values were ultimately calculated and compared with the experimental ones.

Halogen Bonding and Rearrangements in Complexes of N-Chlorosuccinimide with Halides

The role of halogen bonding (HaB) in the reactions of N-chlorosuccinimide (SimCl), a versatile reagent in organic synthesis, was investigated through experimental and computational analyses of its interactions with halides. The reactions of SimCl with Br− or I− resulted in the crystallization of HaB complexes of chloride with N-iodosuccinimide (SimI) or N-bromosuccinimide (SimBr). Computational analysis revealed that halogen rearrangements, which occurred even at −73 °C, were facilitated by halogen bonding. The dissociation of SimCl∙Y− (Y = I or Br) complexes into a Sim− + ClY pair (followed by the rotation and re-binding of the interhalogen molecules) bypassed the formation of the high-energy Sim− + Cl⁺ pair and drastically (about tenfold) reduced the dissociation energy of the N–Cl bond. Furthermore, while the dissociation energy of individual SimCl is higher (and its HaB is weaker) compared to that of SimI or SimBr, the dissociation of the N-Cl bond in SimCl∙Y− requires less energy than in the complexes of SimBr or SimI. The facile cleavage of such bonds in HaB complexes explains the high reactivity of SimCl and its effectiveness as a halogenating agent.

Mechanism of Formation and Decomposition of C6H5(O2•)C(OH)C6H4OH

AbstractIn the present theoretical study, the thermochemical properties of Ph(O2•)C(OH)PhOH and considered products of its oxidation are calculated using the DFT approaches (M062X, B3LYP, wB97XD, M08HX, MN15) at the 6−311++G(d, p) level of theory. The DFT values of ΔraHo(Yi) of the atomization of considered structures are corrected using the linear calibration dependencies reported for the peroxides as well as for the hydrocarbons (including aromatic and simple oxygenated compounds). The values of ΔfHo(Yi, CORR) ± 3SDi, derived from the corrected values of ΔraHo(Yi, CORR), are coordinated by the intersection of their 3SDi intervals, determined previously. The values of ΔfHo(Y, MEAN) ± 2SDY of the Ph(O2•)C(OH)PhOH (2F), Ph•─OO─C(OH)PhOH (3G), HOPh•─OO─C(OH)Ph (2G), PhC(OH)2PhOH (1H), Ph(O2H)C(OH)PhOH (4G) and Ph(O•)C(OH)PhOH (1G) (corresponded, respectively, to −159.4 ± 6,−55.2 ± 6,−61.5 ± 3.7,−385.8 ± 6,−293.4 ± 1.4,−148.9 ± 6 kJ/mol), as well as the values of Ea‡ = 127.8 ± 7, 121.2 ± 8, 17.2 ± 5, 19.4 ± 3 kJ/mol, determined, respectively, for the reactions (R21a), (R21b), (R22a), (R22b) and the values of the rate constants of associated reactions, are reported for the first time. According to calculations, the replacement of >C•H by OH group increases the values of dissociation energy (DE) of >C(X)─O2•, >C(X)O─O•, >C(X)O─H, PhC(X)OO─•PhOH, and HOPhC(X)OO─•Ph bonds, but decreases those values of >C(X)O2–H, HOPhC(X)OO•Ph, and PhC(X)OO•PhOH bonds. As a result of increased stability of the >C(X)─O2• bond (X = OH), the higher temperatures can be used for the chain production of p‐PhC(O2H)HPhOH and p‐PhC(O2H)(OH)PhOH at high concentrations of p‐PhCH2PhOH. On the contrary, the contribution of reactions (R21a) and (R21b) to the oxidation is significant under low concentrations of p‐PhCH2PhOH. Its also found that the stable intermediate O2 π–π cluster, predicted for the >C•(H) radical, is not observed for the reaction of >C•(OH) with O2, due to the formation of a hydrogen bond between the OH group and partially charged O2δ−.

Energetic and Electronic Properties of AcX and LaX (X = O and F).

The bonding and spectroscopic properties of LaX and AcX (X = O and F) diatomic molecules were studied by high-level ab initio CCSD(T) and SO-CASPT2 electronic structure calculations. Bond dissociation energies (BDEs) were calculated at the Feller-Peterson-Dixon (FPD) level. Potential energy curves and spectroscopic constants for the lowest-lying spin-orbit Ω states were obtained at the SO-CASPT2/aQ-DK level. A dense manifold of excited states was described for the monofluorides with the ground states well separated from the excited states. The spectroscopic parameters were in good agreement with those reported experimentally for LaO and LaF. For the diatomic molecules containing actinides, no experimental data of these parameters was found, but the results were consistent with other high-level calculations. The BDEs calculated at the FPD level were 791.3 (LaO), 705.2 (AcO), 650.0 (LaF), and 678.6 (AcF) kJ/mol. The NBO analysis showed that the monofluorides are essentially ionic, which explains why the BDE(AcF) is higher than BDE(LaF); for the monoxides, covalent contributions involving the d orbitals of the metal and the p orbitals of the oxygen are stronger for LaO than AcO, which explains the higher BDE for LaO. The bond orders are predicted to be 2 for LaF and AcF, 3 for AcO, and higher than 3 for LaO.

Improving Bond Dissociations of Reactive Machine Learning Potentials through Physics-Constrained Data Augmentation.

In the field of computational chemistry, predicting bond dissociation energies (BDEs) presents well-known challenges, particularly due to the multireference character of reactive systems. Many chemical reactions involve configurations where single-reference methods fall short, as the electronic structure can significantly change during bond breaking. As generating training data for partially broken bonds is a challenging task, even state-of-the-art reactive machine learning interatomic potentials (MLIPs) often fail to predict reliable BDEs and smooth dissociation curves. By contrast, simple and inexpensive physics-based models, such as the well-established Morse potential, do not suffer from any such limitations. This work leverages the Morse potential to improve reactive MLIPs by augmenting the training data set with inexpensive Morse data along the dissociation pathways. This physics-constrained data augmentation (PCDA) approach results in MLIPs with smooth bond dissociation curves as well as near coupled-cluster level BDEs, all without requiring any expensive multireference quantum mechanical calculations. A case study for methane combustion demonstrates how the PCDA approach can improve an existing reactive MLIP, namely, ANI-1xnr. Not only are the BDEs and bond dissociation curves for all radicals and molecules significantly improved compared to ANI-1xnr but the PCDA-trained MLIP retains the reliability of ANI-1xnr when performing reactive molecular dynamics simulations.

Interstellar spectroscopic detection of HC(S)NC and DC(S)NC.

The detection of HC(S)CN in TMC-1 suggests that HC(S)NC may also exist. To aid in its possible detection, HC(S)NC and its deuterated isotopologue DC(S)NC were investigated via high-level abinitio methods, specifically CCSD(T) and CCSD(T)-F12. By utilizing multidimensional potential energy surfaces derived from explicitly correlated coupled-cluster calculations, we analyzed their geometrical parameters, vibrational frequencies, rotational constants, and a comprehensive set of spectroscopic constants generated via the vibrational second-order perturbation theory, vibrational self-consistent field, and vibrational configuration interaction theory(VCI) approaches. HC(S)NC is thermodynamically stable relative to the HCS + NC dissociation limit, with a predicted bond dissociation energy of 4.1eV. The calculated vibrational frequencies are characterized by two bright modes that correspond to CN stretching. Finally, HC(S)NC shows a significant dipole moment, predicted to be 1.9D, making its detection via rotational spectroscopy plausible.

Excited electronic states of Na2 and K2: The potential for long-lived "reservoir" states leading to collision induced population inversions.

Potential energy curves (PECs) for the spin-free (ΛS) and spin-orbit (Ω) states associated with the four lowest-lying dissociation channels of Na2 and K2 were calculated at the SA-CASSCF/SO-CASPT2/aug-cc-pwCVQZ-DK level. The PECs of Na2 were consistent with the experimental data and with the FS-CCSD (2,0) calculations, reproducing the double-well and the "shelf" character for some of the potentials of the excited states. For K2, the PECs behaved in a similar way and the spectroscopic parameters for the ground and the excited states are in good agreement with the available experimental values. The dissociation energy of K2 was predicted to be De = 4454cm-1, within an agreement of 5cm-1 with the experiments. For Na2, De = 5789cm-1 compared to the experimental value of 6022cm-1. The inclusion of spin-orbit coupling effects resulted in avoided crossings, which affect the PECs. Spin-orbit changes the predicted curves for some excited Ω states arising from ΛS states that overlap each other, affecting their associated vibrational frequencies and bond distances. The current studies of the low-lying states in K2 reveal a similar structure to those of Na2, which suggests the accessibility of long-lived energy storing reservoir states and possible population inversions in K2 following prior experimental work on the reaction of halogen atoms with Na3 to produce excited states of Na2.

Nature and stability of the chemical bond in H3C-XHn (XHn = CH3, NH2, OH, F, Cl, Br, I).

We have quantum chemically analyzed the trends in bond dissociation enthalpy (BDE) of H3C-XHn single bonds (XHn = CH3, NH2, OH, F, Cl, Br, I) along three different dissociation pathways at ZORA-BLYP-D3(BJ)/TZ2P: (i) homolytic dissociation into H3C∙ + ∙XHn, (ii) heterolytic dissociation into H3C+ + -XHn, and (iii) heterolytic dissociation into H3C- + +XHn. The associated BDEs for the three pathways differ not only quantitatively but, in some cases, also in terms of opposite trends along the C-X series. Based on activation strain analyses and quantitative molecular orbital theory, we explain how these differences are caused by the profoundly different electronic structures of, and thus bonding mechanisms between, the resulting fragments in the three different dissociation pathways. We demonstrate that the nature and strength of a chemical bond are only fully defined when considering both (i) the molecule in which the bond exists and (ii) the fragments from which it forms or into which it dissociates.

Ultrabright and Stable Red Perovskite Nanocrystals in Micro Light-Emitting Diodes Using Flow Chemistry System.

Addressing the challenges of the efficiency and stability of red perovskite nanocrystals is imperative for the successful deployment of these materials in displays and lighting applications. the structural dynamic changes of red perovskite quantum dots (PQDs) are explored using a flow chemistry system to solve the above hurdles. First, the ultrabright red-emitting PQDs of CsPb(Br,I)3 are achieved by adjusting ligand distribution (oleic acid and oleyamine) in combination with different flow rates and equivalence ratios. The PQDs exhibit an impressive photoluminescence quantum yield (PLQY) of 95%. In addition, as mentioned in numerous previous studies, the severe instability of mixed halide perovskites is due to halide immigration. Therefore, in this paper, zinc, which has a lower dissociation energy than lead is utilized, as a reagent to provide more halide ions in the synthesis to enhance the stability of PQDs. As a result, a CsPb(Br,I)3@Cs4Pb(Br,I)6 core-shell structure with outstanding stability and 92% PLQY is obtained. The simple method for synthesizing the core-shell structure of CsPb(Br,I)3@Cs4Pb(Br,I)6 paves the way for the production of perovskite micro light-emitting diodes for commercial applications.

The Degree and Origin of the Cooperativity of the Chalcogen (Ch···N) and Dihydrogen (H···H) Bonds in Some Triad Systems.

The strength and cooperative energy of chalcogen and dihydrogen bonds in some ABC triad systems of the types XHTe…NCH…HY (X = F, Cl, Br, I, H; Y = Li, Na, BeH, MgH) and FHCh…NCH…HNa (Ch = Te, Se, S) were computed and compared at several levels of theory. All resulting data showed that the strengths of chalcogen (Te…N) and dihydrogen (H…H) bonds increase in the order of H < I < Br < Cl < F, and Be < Mg < Li < Na, respectively. Then, the comparison of data for the FHTe…NCH…HY, FHSe…NCH…HNa, and FHS…NCH…HNa triads indicated that the interaction, stabilization, and cooperativity energies decrease in the order of Te > Se > S. The data show that in all cases the chalcogen and dihydrogen bonds change the bond dissociation energies (BDEs) and interaction energies (IEs) of each other by the same quantitative value. However, the relative impact of the above bonds on BDEs and IEs of each other depends on the relative strength of these bonds. Finally, the nature of both dihydrogen and chalcogen bonds and the origin of the cooperativity of bonds were evaluated by NBO and energy decomposition analysis (EDA) analyses.

Theoretical Investigation of Bond Dissociation Energies of exo-Polyhedral B–H and B–F Bonds of closo-Borate Anions [BnHn−1X]2− (n = 6, 10, 12; X = H, F)

This paper reports on a theoretical investigation of the bond dissociation energies of B–H and B–F interactions of closo-borate anions [BnHn−1X]2− (n = 6, 10 and 12; X = H and F), in which homolytic and heterolytic bond breaking cases were considered, and the main trends in bond dissociation energy values were analysed. The wB97X-D3/TZVPP level of theory was applied for geometry optimisation of the molecular species under consideration. DLPNO-CCSDT/CBS single-point calculations were made to ensure an accurate estimation of the target systems’ electronic energy. The correlations between the value of the bond dissociation energy and variables such as electron density descriptors of B–H and B–F interactions and frontier orbital energies (HOMO, SOMO and LUMO) were established.

Bio-waste derived reduced graphene oxide (rGO) decorated Cr (III) doped α-Fe2O3 nanocomposite for selective ppm-level acetone sensing at room temperature: Potential approach towards non-invasive diagnosis of diabetic biomarker

Reduced graphene oxide (rGO) was synthesized via reduction of graphitized household tea-waste utilizing neem leaves extract. The synergistic effect of rGO decoration and Cr3+ doping within pristine Fe2O3 enhanced surface adsorption property, defect density, and oxygen vacancies, facilitating the detection of ppm-levels (1 to 10 ppm) acetone at room temperature. Noticeably, the formation of ‘inversion space-charge-layer’ on sensing material surface at lower operating temperature resulted p-type sensing response using n-type nanomaterial that was transformed to n-type response when the operating temperature was elevated. The maximum sensing response (Rg/Ra) ~ 6.8 towards ~ 10 ppm acetone was obtained from optimized rGO decorated Cr3+ doped Fe2O3 sensor (FC3R3) at ambient condition. This sensor also revealed a rapid response/recovery time (~ 10 s/ ~ 10 s) and was able to detect as low as ~ 1 ppm acetone. The sensor exhibited improved selectivity towards acetone over other interfering VOCs, attributed to significant dipole moment, low bond dissociation energy, and strong affinity of acetone towards surface-adsorbed oxygenated ions. Notably, the sensor showed negligible deterioration in sensing performance even after ~ 150 days. Furthermore, this sensor was capable to differentiate between acetone concentration in breath sample of healthy and diabetic person for non-invasive diabetes detection.