ABSTRACTMN15/6‐31++G(d,p)/IEFPCM theory level gave a good agreement between the calculated vibronic and experimental absorption spectra of the dianion, in both the maximum position and the shape. Vibronic transitions of the dianion activate only two motions in the S1 state, namely, torsional vibrations of two aromatic rings (A and B) and the SO3 group attached to the third ring. Significant photoinduced distortions of the spatial structure of the anion (A and B rings, being almost parallel to each other in the ground state, become mutually perpendicular in the excited state) led to a failure of the Franck‐Condon computational procedure for calculating its vibronic spectrum. Photo‐induced shifts of the electron density are analyzed. The ring with the SO3 group attached is not involved in these charge redistributions for both the dianion and the anion. The negative solvatochromism of the dianion and the positive one of the anion observed experimentally were explained both from the point of view of non‐specific dipole–dipole interactions with the solvent (changes in the dipole moments of the solutes upon excitation) and specific ones (strengthening/weakening of strong hydrogen bonds of the dianion and anion with water molecules).
A.R. El Zanin, S.V. Boroznin, I.V. Zaporotskova
et al.
Due to the high practical significance and, as a consequence, active study of carbon nanomaterials, the question of methods for investigating their physicochemical, in particular, thermodynamic properties is relevant. In the present work, several approaches are considered to estimate the standard enthalpy of formation of fullerenes in the gas phase. The standard enthalpies of formation of C60 and C70 fullerenes in the gas phase have been calculated using the Laidler, Franklin, Souders-Matthews-Hurd and Joback-Reid methods. A number of analytical dependences of the standard enthalpy of formation in the gas phase on the number of carbon atoms in fullerenes molecules were obtained. The obtained values were compared with experimental data and the relative error of calculation was determined. It is concluded that the proposed methods are limitedly applicable for determination of standard enthalpy of formation of fullerenes in the gas phase. The obtained values of the standard enthalpy of formation by the most satisfactory method from the considered ones for fullerenes C60 and C70 are 2448,90 and 2857,05 kJ/mol, and the relative errors are 4,44% and 5,95%, respectively. This is the Souders-Matthews-Hurd method. The presented analytical dependences allow for an express estimation of the standard enthalpy of formation of fullerenes in the gas phase with a small amount of input data.
Lithium/fluorinated carbon (Li/CFx) primary battery is a promising energy supply device with high energy density. However, poor electrochemical capabilities such as the initial voltage delay phenomenon and the large polarization have obstructed their applications. The electrochemical performance of CFx primarily depends on the feature of the carbon source and the corresponding fluorination technique. Herein, we developed a high energy density Li/CFx battery by employing helical carbon nanotubes (HCNTs) as the carbon source. In detail, the precise control of the fluorination temperature was designed at the range of 250–400°C to tune the F/C ratio of CFx. Furthermore, the high F/C ratio of fluorinated HCNTs (F-HCNTs) reaches about 1.43, which surpasses the highest theoretical value in fluorinated crystalline carbon materials. Due to the active rich fluorination sites provided by the periodical insertion of the carbon pentacyclic (C5) and heptacyclic (C7) rings, HCNTs exhibited a defect-rich feature and F-HCNTs have a nodular shape. These features favor to enhance the transport of lithium ions and allow more C–F bonds to react with lithium ions, leading to a high energy density of 2133.13 W h/kg. This novel material offers an alternative approach for lithium primary battery being great potential in actual applications.
: Complex machine learning (ML) models applied within computational chemistry and materials science tend to be seen as black boxes, yielding property predictions given some input features. While the purpose of ML methods is often to circumvent computationally expensive fi rst-principles calculations, the fact that the inner workings of the models are not understood conceals chemical insight and knowledge regarding the underlying data and physical correlations within it. Knowing what a model is learning from the data and how outputs are formed is also useful in facilitating the justi fi cation and wider adoption of ML solutions. Here, we present an important contribution in this direction by exploring and explaining the hydrogen adsorption properties of defective nitrogen-doped carbon nanotubes (NCNTs) through density functional theory simulations and machine learning-based data analysis. As the main highlight, we demonstrate the application of a recent game-theoretic approach to deconvolute and interrogate the trained ML models, revealing how various structural, chemical, and electronic features contribute toward the hydrogen a ffi nities of roughly 6500 di ff erent NCNT adsorption sites. The employed method of Shapley additive explanations (SHAP) attributes locally accurate importances to the investigated features, unraveling high spin polarization, narrow highest occupied molecular orbital − lowest unoccupied molecular orbital (HOMO − LUMO) gap, small dopant − adsorption site separation, and diverse angle and coordination e ff ects as particularly impactful for increasing hydrogen adsorption strengths. The SHAP method is shown capable of promoting a deep understanding of complex feature − activity relationships, facilitating research e ff orts such as rational catalyst design for energy conversion applications.
Electrochemical methods were used in conjunction with digital holography to study the effects of an environmentally friendly inhibitor, polyaspartic acid (PASP), on the anodic dissolution of Inconel® 600 in a 0.04 M HCl solution. The pitting inhibition ability was enhanced and the inhibition efficiency increased with the PASP concentration, reaching 84.13 % at 6.66 g L−1 PASP. A digital holograph was used to observe the in situ hydrolysis of M2+ (M = Ni and Fe) near the electrode surface during anodic dissolution and showed the formation of a surface film on the electrode. The inhibitory effects of PASP on Inconel® 600 may be caused by the adsorption of PASP and the formation of a PASP metal complex (PASP-M complex), which may seal defects in the surface film.
The magnetic adsorption material of polyaniline (PANI) with amino functional group combined with CuFe2O4 (CuFe2O4/PANI nanocomposite) has been described in this work. It has been characterized by TEM, XRD, XPS, BET, FTIR, and VSM, respectively. Significantly, it exhibits extremely high maximum adsorption capacity (322.6 mg/g) for removal of uranyl ions from wastewater at a pH of 4. The adsorption process is consistent with the quasisecond-order kinetic equation, and the isotherm and kinetic data are accurately described by the Langmuir isothermal adsorption model. Furthermore, the magnetic CuFe2O4/PANI displays stable adsorption performance for uranyl ions after five cycles of recovery in acid medium, which indicates it possesses good recovery due to its magnetism and excellent regeneration ability for reusability.
Abstract. The number concentration of cloud particles is a key quantity for understanding aerosol–cloud interactions and describing clouds in climate and numerical weather prediction models. In contrast with recent advances for liquid clouds, few observational constraints exist regarding the ice crystal number concentration (Ni). This study investigates how combined lidar–radar measurements can be used to provide satellite estimates of Ni, using a methodology that constrains moments of a parameterized particle size distribution (PSD). The operational liDAR–raDAR (DARDAR) product serves as an existing base for this method, which focuses on ice clouds with temperatures Tc<-30 ∘C. Theoretical considerations demonstrate the capability for accurate retrievals of Ni, apart from a possible bias in the concentration in small crystals when Tc≳−50 ∘C, due to the assumption of a monomodal PSD shape in the current method. This is verified via a comparison of satellite estimates to coincident in situ measurements, which additionally demonstrates the sufficient sensitivity of lidar–radar observations to Ni. Following these results, satellite estimates of Ni are evaluated in the context of a case study and a preliminary climatological analysis based on 10 years of global data. Despite a lack of other large-scale references, this evaluation shows a reasonable physical consistency in Ni spatial distribution patterns. Notably, increases in Ni are found towards cold temperatures and, more significantly, in the presence of strong updrafts, such as those related to convective or orographic uplifts. Further evaluation and improvement of this method are necessary, although these results already constitute a first encouraging step towards large-scale observational constraints for Ni. Part 2 of this series uses this new dataset to examine the controls on Ni.