Hydration Of Complexes Research Articles

Mechanochemical Syntheses of Ln(hfac)3(H2O)x (Ln = La-Sm, Tb): Isolation of 10-, 9-, and 8-Coordinate Ln(hfac)n Complexes.

Volatile lanthanide coordination complexes are critical to the generation of new optical and magnetic materials. One of the most common precursors for preparing volatile lanthanide complexes is the hydrate with the general formula Ln(hfac)3(H2O)x (x = 3 for La-Nd, x = 2 for Sm) (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato). We have investigated the synthesis of Ln(hfac)3(H2O)x using more environmentally sustainable mechanochemical approaches. Characterization of the products using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis, and powder X-ray diffraction shows substantial differences in product distribution between methods. The mechanochemical synthesis of the hydrate complexes leads to a variety of coordination compounds including the expected hydrate product, the known retro-Claisen impurity, and hydrated protonated Hhfac ligand depending on the technique employed. Surprisingly, 10-coordinate complexes of the form Na2Ln(hfac)5·3H2O for Ln = La-Nd were also isolated from reactions using a mortar and pestle. The electrostatic bonding of lanthanide coordination complexes is a challenge for obtaining reproducible reactions and clean products. The reproducibility issues are most acute for the large, early lanthanides whereas for the mid to late lanthanides, reproducibility in terms of product distribution and yield is less of an issue because of their smaller size and greater charge to radius ratio. Ball milling increases reproducibility in terms of generating the desired Ln(hfac)3(H2O)x along with hydrated Hhfac (tetraol) and free Hhfac products. The results illustrate the dynamic behavior of lanthanide complexes in solution and the solid state as well as the structural diversity available to the early lanthanides.

A unified effective medium modeling framework for quantitative characterization of hydrate reservoirs

Quantitative characterization of hydrate reservoirs is essential for evaluating hydrate resources and monitoring environmental hazards. Rock-physics models provide the theoretical basis for linking the hydrate saturation and distribution to the elastic properties. However, many of the existing models ignore the coupled effect of hydrate saturation and complex morphologies on the elastic behaviors and thereby fail to accurately describe hydrate reservoirs. To address these problems, the authors have proposed a unified effective medium modeling framework honoring multiple hydrate morphologies. In this framework, the manners in which the different types of hydrates interact with the sediment grains are characterized by different effective medium models. In addition to the hydrate saturation, the modeling results also reveal the effects of the cement factor, friction coefficient, incidence angle, lithology, and hydrate morphology on the elastic properties of the hydrate reservoirs. Then, five experimental data sets for synthetic methane and tetrahydrofuran hydrates formed under different conditions are used to validate the feasibility of the unified rock-physics modeling scheme. The good agreement between the theoretical predictions and laboratory data indicates that this method can effectively determine the hydrate occurrence mechanisms from the acoustic responses in different hydrate formation environments. On the basis of the constructed elastic rock-physics templates, multiple hydrate morphologies are determined with cluster analysis and then used for constraining the modeling scheme. Finally, the proposed modeling method is tested using sonic logs from Ignik Sikumi, North Slope of Alaska, and Hole U1518B, the northern Hikurangi margin, offshore New Zealand. The hydrate saturations estimated from the velocities are consistent with the interpretations based on resistivity and nuclear magnetic resonance logs, as well as chloride measurements, confirming the applicability and feasibility of our unified theoretical modeling framework.

Analysis of wellbore stability for overbalanced drilling in marine methane hydrate-bearing sediments under non-hydrostatic stresses

New challenges have emerged in drilling marine methane hydrate-bearing sediments (MHBSs); these challenges are closely related to methane hydrate (MH) dissociation and complex multi-physics coupling. This study investigates wellbore stability in overbalanced drilling by proposing exact solutions for multi-physics fields, taking into account the more general non-hydrostatic far-field stresses, partial multi-field coupling and the influences of hydrate dissociation, i.e., the water/heat production/absorption and the change in the physical properties of reservoirs due to hydrate dissociation.Wellbore drilling is simplified as a non-axisymmetric plane strain problem for the mechanical field and an axisymmetric problem for the pressure/temperature/salt concentration fields, in which the drilling domain includes four annular regions with different physical properties. The closed-form solutions for the temperature, pore pressure and salt concentration fields are obtained by considering the influence of water/heat production/absorption in the compatibility conditions of the steady-state governing equations. The solutions can explain the secondary formation of MHs around the dissociation front. The stress and drilling-induced displacement are then derived for the multi-region elastic problem subjected to non-hydrostatic far-field stresses considering seepage flow, with which the initial failure zone can be addressed by considering a failure criterion. The analytical solutions are verified by the good agreement between analytical and numerical results based on the same assumptions. Furthermore, the comparison between the analytical solutions and the results from complex numerical models suggests the applicability of the proposed solutions. Based on the conditions in marine hydrate field trials in the Shenhu area of the South China Sea, the influence of key parameters on wellbore stability in drilling in MHBSs is investigated in detail by the proposed solutions. Some useful dimensionless charts are provided.

The simultaneous removal of co-contaminants pyrene and Cu (II) from aqueous solutions by Fe/Mn bimetallic functionalized mesoporous silica.

In recent years, the co-contamination of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) has attracted more and more attention, and finding efficient and coordinated removal method has been the hot focus. In this study, Fe/Mn-SBA15 bimetallic mesoporous silica adsorbent (Fe/Mn-SBA15) was prepared by hydrothermal method with the functional groups Fe and Mn simultaneously doped into the framework structure of SBA15. Fe/Mn-SBA15 was systematically characterized by XRD, TEM, and BET and used in removal of typical PAHs-pyrene and heavy metal-Cu (II) from aqueous solutions simultaneously. The single and binary adsorption behaviors were studied by kinetics, isotherm, pH, and ionic strength. The results showed that the functional groups of Fe and Mn were successfully loaded into the structure of SBA15 and the prepared adsorbent was still a typical mesoporous adsorbent. The adsorption of pyrene and Cu (II) onto Fe/Mn-SBA15 was fast and the adsorption equilibrium was achieved in 100min. The Langmuir model fitted the adsorption isotherm better and the maximum adsorption capacities for pyrene and Cu (II) were 120mg/g and 10.52mg/g, respectively. The increase of ionic strength could enhance and decrease the adsorption capacity of pyrene and Cu (II), which may be attributed to salting-out effect and potassium competitive. With the increase of pH values, the negative charge on the surface of the adsorbent increased, resulting in the decrease and increase of adsorption capacity of pyrene and Cu (II) onto Fe/Mn-SBA15. In addition, Fe/Mn-SBA15 was found to have a synergistic effect on the adsorption of pyrene and Cu (II). This result is mainly due to the formation of hydration complex by pyrene-Cu (II) through cation-π interaction, which increases the adsorption capacity by occupying each other's adsorption sites of adsorbent. This study provides a new method for the synergistic removal of PAHs and HMs from aqueous solutions.

Crystallization of Mn(II) and Cd(II) Complexes in A Water-Methanol System: Tartrate vs Nicotinamide Ligand Selectivity

Ligand selectivity of tartrate vs nicotinamide in a water-methanol system has been observed in the crystallization of Mn(II) and Cd(II) complexes. These complexes were crystallized at room temperature by a layered solution technique using a water-methanol mixture solvent in a M(II):tartrate:nicotinamide (M = Mn, Cd) molar ratio of 1:1:2. Complexes of M(II)-nicotinamide and M(II)-tartrate were also prepared for data comparison. Analysis of the crystals by infrared spectroscopy, powder-X-ray diffraction and qualitative anion test showed that in a presence of both tartrate and nicotinamide, the Mn(II) forms neutral Mn(II)-tartrate hydrate complex, whereas the Cd(II) forms ionic Cd(II)-nicotinamide chloride complex. In the case of Mn(II) complex, tartrate tend to coordinate as ligand than the nicotinamide, although molar ratio of nicotinamide was doubled than that of tartrate ligand. In contrast, the neutral nicotinamide ligand is more predominant to coordinate in the Cd(II) complex than the anionic tartrate. The tartrate-nicotinamide ligand selectivity in the crystallization of Mn(II) and Cd(II) complexes is likely due to the use of tartrate salt as precursor and the choice of solvent mixture. In addition, powder-XRD analysis confirms that there was no indication of M(II)-tartrate and M(II)-nicotinamide that co-crystallized together at the same time by both metal ions.

Coumarin 343 in aqueous solution: theoretical analysis of absorption.

Vibronic coupling and hydration were taken into account when describing the absorption of coumarin C343 (both neutral and anionic forms) in an aqueous media. It was shown that the B3LYP functional with the 6-31 + + G(d,p) basis set and the IEFPCM solvent continuum model give theoretical vibronic absorption spectra, which are coincide with the experimental ones. Of the structural differences between C3430 and C343-, there is a different twisting of the carboxyl group additionally changing due to excitation. Upon excitation, a significant shift in the electron density occurs from the C10 atom to the C4 atom only. Thus, a charge transfer on the scale of the entire molecule does not occur. Different hydration complexes with strongly bound water molecules have been analyzed.

Coumarin 314 excitation in aqueous media: Contributions of vibronic coupling and hydration

Vibronic coupling and hydrogen bonding were considered when analyzing the excitation of coumarin C314. It was found that the B3PW91 functional in combination with the 6–31++G(d,p) basis set and the IEFPCM solvent model gives a calculated vibronic absorption spectrum, which is in good agreement with the experimental one both in the position of the maximum and in shape. Significant differences are shown between the results of calculating the transition energies using the models of vertical and vibronic transitions. Both a single C314 molecule and its five different hydration complexes with strongly bound water molecules have been analyzed. It was taken into account that a water molecule can attach both to the nitrogen atom N1 (“A” type) and the C=O carbonyl groups of the dye (“B” type). The vibronic emission spectra of a single C314 molecule and its hydrate complexes were also calculated and analyzed.

Hydration Structures and Dynamics of Ga3+ Ion Based on Molecular Mechanics Molecular Dynamics Simulation (Classical DM)

The structure and hydration dynamics of Ga3+ ion have been studied using classical Molecular Dynamics (MD) simulations. The data collection procedure includes determining the best base set, constructing 2-body and 3-body potential equations, classical molecular dynamics simulations based on 2-body potentials, classical molecular dynamics simulations based on 2-body + 3 potential-body. The trajectory file data analysis was done to obtain structural properties parameters such as RDF, CND, ADF, and dynamic properties, namely the movement of H2O ligands between hydrations shells. The results of the research indicated that the hydration complex structure of Ga(H2O)83+ and Ga(H2O)63+ was observed in molecular dynamics simulations (MM-2 body) and (MM-2 body + 3-body), respectively. The movement of H2O ligands occurs between the first and second shell or vice versa in the MD simulation of MM-2 bodies but does not occur in MD simulations of (MM-2 bodies + MM-3 bodies). Therefore, the water ligands in the first hydrated shell are stable.

Native Cyclodextrins as Complexation Agents for Pterostilbene: Complex Preparation and Characterization in Solution and in the Solid State

Pterostilbene (3,5-dimethoxy-4′-hydroxystilbene, PTB) is a natural dietary stilbene, occurring primarily in blueberries and Pterocarpus marsupium heartwood. The interest in this compound is related to its different biological and pharmacological properties, such as its antioxidant, anti-inflammatory, and anticarcinogenic activities and its capacity to reduce and regulate cholesterol and blood sugar levels. Nevertheless, its use in therapy is hindered by its low aqueous solubility; to overcome this limitation we studied the feasibility of the use of cyclodextrins (CDs) as solubility-enhancing agents. CDs are natural macrocyclic oligomers composed of α-d-glucose units linked by α-1,4 glycosidic bonds to form torus-shaped molecules, responsible for inclusion complex formation with organic molecules. In particular, the aim of this study was to evaluate the feasibility of complexation between PTB and native CDs using various preparative methods. The isolated solid products were characterized using differential scanning calorimetry (DSC), simultaneous thermogravimetric/DSC analysis (TGA/DSC), Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) on powder and single crystals. The results indicated little or no evidence of the affinity of PTB to complex with α-CD using the kneading method. However, with β-CD and γ-CD thermal analysis revealed an interaction which was also corroborated by FT-IR and 1H-NMR spectroscopy. With β-CD, a hydrated complex of PTB was isolated and its characterization by single-crystal XRD revealed, for the first time, the mode of inclusion of the PTB molecule in the cavity of a CD. To complement the solid-state data, liquid-phase studies were carried out to establish the effect of CDs on the aqueous solubility of PTB and to determine the complex stoichiometries and the association constants for complex formation. Phase-solubility studies showed AL-type profiles for α- and β-CD and a BS profile for γ-CD, with K1:1 values of 1144, 4950, and 133 M−1 for α-CD·PTB, β-CD·PTB, and γ-CD·PTB, respectively. The stoichiometry of CD·PTB complexes, determined by Job’s method, revealed for each system a 1:1 molar ratio. The dissolution rate of PTB was approximately doubled just by employing simple physical mixtures, but the best performance was achieved by products obtained via kneading and co-precipitation, which effected the complete dissolution of PTB in 40 and 20 min for β-CD and γ-CD, respectively.

Некоторые термодинамические и кинетические свойства системы H2SO4–H3PO4–H2O–Fe(III)

The values of the electrode potentials of the redox couple Fe(III) / Fe(II) and the half-wave potentials of the reactions Fe3+ + e– = Fe2+ и Fe2+ — e– = Fe3+ on the cyclic voltammogram of a platinum electrode in acid solutions containing Fe(III) salts have been measured to characterize the oxidizing ability of the H2SO4—H3PO4—H2O—Fe(III) system. The values of these experimentally obtained parameters are close. A decrease in the oxidizing ability of H2SO4 and H3PO4 mixtures containing Fe(III) with an increase in the molar fraction of H3PO4 in them occurs due to the formation of Fe(III) complexes with phosphate anions which are inferior to their hydrate and sulfate complexes in the oxidizing ability. The temperature coefficients of the electrode potential (dE / dt) of the redox couple Fe(III) / Fe(II) in the H2SO4—H2O, H2SO4—H3PO4—H2O and H3PO4–H2O systems were determined experimentally. The diffusion coefficients of Fe(III) in the studied solutions were calculated based on the Randles—Shevchik equation. The temperature dependence of the diffusion coefficients of Fe(III) cations is satisfactorily described by the Arrhenius equation. The parameters of this equation are calculated.

Visible light driven photocatalytic removal of uranium(VI) in strongly acidic solution

Photocatalytic reduction and removal of toxic uranium(VI) from aqueous solution is a highly economic, non-pollutant and efficient strategy. However, most uranium containing waste waters are highly acidic, but current photocatalysts are still restricted in slightly acidic or neutral media (pH ≥ 4). Herein, a conjugated microporous polymer (CMP), pTTT-Ben, was used for visible light driven photocatalytic reduction of U(VI) in highly acidic condition (pH = 1). A high uranium removal capacity (4710 mg/g) was achieved. The structural information of reduced uranium was investigated by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS), revealing the amorphous U(IV) hydrate complex, with an additional interaction between U(IV) and nitrogen atoms on pTTT-Ben. In addition, pTTT-Ben also showed excellent photocatalytic U(VI) reduction performance under natural sunlight irradiation.

Strength and Leaching Behavior of Contaminated Mining Sludge at High Water Content Stabilized with Lime Activated GGBS.

Sludge management is one of the major challenges in mining activities. The direct disposal of contaminated mining sludge can bring severe damages to the environment and community. Solidification/stabilization (S/S) is a very efficient technology for the treatment of contaminated mining sludge because it improves the stability of sludge dumping sites and reduces the leachability of contaminants. Very few studies investigate the S/S of mining sludge, especially with high water content. This paper investigated the effectiveness of S/S for the treatment of mining sludge at high water content by using quick lime (CaO) activated ground granulated blast furnace slag (GGBS) in comparison to ordinary Portland cement (OPC). To evaluate the mechanical, leaching, and microstructural behavior of CMS at high water content stabilized by lime-activated GGBS and OPC, a series of laboratory experimental tests were performed. Experimental results indicated that increasing the dosage of binder led to increased strength and decreased leachability of the heavy metal. In contrast, an increase in the water content of the mixture resulted in a decrease in compressive strength and an increase in the leachability of heavy metals. On the other hand, lime-activated GGBS mixes had substantially better performance than OPC mixes in the aspect of strength development of treated mining sludge and showed comparable capability of heavy metal stabilization compared to OPC. The microstructural tests revealed the formation of different hydration products such as calcium silicate hydrate, calcium aluminum silicate hydrate, ettringite, hydrotalcite, and heavy metal complexes in CG and OPC mixes.

Structural Water Molecules Confined in Soft and Hard Nanocavities as Bright Color Emitters.

Molecules confined in the nanocavity and nanointerface exhibit rich, unique physicochemical properties, e.g., the chromophore in the β-barrel can of green fluorescent protein (GFP) exhibits tunable bright colors. However, the physical origin of their photoluminescence (PL) emission remains elusive. To mimic the microenvironment of the GFP protein scaffold at the molecule level, two groups of nanocavities were created by molecule self-assembly using organic chromophores and by organic functionalization of mesoporous silica, respectively. We provide strong evidence that structural water molecules confined in these nanocavities are color emitters with a universal formula of {X+·(OH-·H2O)·(H2O) n-1}, in which X is hydrated protons (H3O+) or protonated amino (NH3 +) groups as an anchoring point, and that the efficiency of PL is strongly dependent on the stability of the main emitter centers of the structural hydrated hydroxide complex (OH-·H2O), which is a key intermediate to mediate electron transfer dominated by proton transfer at confined nanospace. Further controlled experiments and combined characterizations by time-resolved steady-state and ultrafast transient optical spectroscopy unveil an unusual multichannel radiative and/or nonradiative mechanism dominated by quantum transient states with a distinctive character of topological excitation. The finding of this work underscores the pivotal role of structurally bound H2O in regulating the PL efficiency of aggregation-induced emission luminogens and GFP.

Yb to Tb Cooperative Upconversion in Supramolecularly Assembled Complexes in a Solution

The podand-type ligand L, based on a tertiary amine substituted by three pyridyl-6-phosphonic acid functions, forms hydrated complexes with Ln3+ cations. The luminescence properties of the YbL complex were studied in D2O as a function of the pD and temperature. In basic conditions, increases in the luminescence quantum yield and the excited state lifetime of the Yb centered emission associated with the 2F5/2 → 2F7/2 transition were observed and attributed to a change in the hydration number from two water molecules in the first coordination sphere of Yb at acidic pH to a single one in basic conditions. Upon the addition of TbCl3 salts to a solution containing the YbL complex in D2O, heteropolynuclear Yb/Tb species formed, and excitation of the Yb at 980 nm resulted in the observation of the typical visible emission of Tb as a result of a cooperative upconversion (UC) photosensitization process. The UC was further evidenced by the quadratic dependence of the UC emission as a function of the laser power density.

27439 Expression of skin barrier-related genes and long-lasting moisturization by a natural hydration complex

Background: Stratum corneum water content greatly influences skin’s appearance and its mechanical and metabolic properties. A compromised skin barrier resulting from dry skin can be improved with use of a moisturizer. Plant actives have been shown to be effective in the management of several skin conditions, including atopic dermatitis, psoriasis and xerosis. A natural hydration complex (NHC) was developed using proprietary formulation of pea protein, squalane and inulin to deliver long-lasting skin hydration.

Cadmium Isotope Fractionation during Complexation with Humic Acid.

Cadmium (Cd) isotopes are known to fractionate during complexation with various environmentally relevant surfaces and ligands. Our results, which were obtained using (i) batch experiments at different Cd concentrations, ionic strengths, and pH values, (ii) modeling, and (iii) infrared and X-ray absorption spectroscopies, highlight the preferential enrichment of light Cd isotopes bound to humic acid (HA), leaving the heavier Cd pool preferentially in solution (Δ114/110CdHA-Cd(aq) of -0.15 ± 0.01‰). At high ionic strengths, Cd isotope fractionation mainly depends on its complexation with carboxylic sites. Outer-sphere complexation occurs at equilibrium together with inner-sphere complexation as well as with the change of the first Cd coordination and its hydration complexes in solution. At low ionic strengths, nonspecific Cd binding induced by electrostatic attractions plays a dominant role and promotes Cd isotope fractionation during complexation. This significant outcome elucidates the mechanisms involved in HA-Cd interactions. The results can be used during (i) fingerprinting the available Cd in soil solution after its complexation with solid or soluble natural organic matter and (ii) evaluating the contribution of Cd complexation with organic ligands and phytoplankton-derived debris versus Cd assimilation by phytoplankton in seawater.

ADDITIVES FOR HEAVY CONCRETE BASED ON INDUSTRIAL WASTE FROM CHEMICAL INDUSTRIES

The effect of a complex additive containing superplasticizer C-3 on the properties of heavy concrete has been investigated. The efficiency of the plasticizing action of the specified additive at the stage of preparation of the concrete mixture and subsequent molding of concrete products has been revealed. It is proved that at the stage of concrete hardening, the investigated additive promotes to the formation of a more homogeneous colloidal-crystalline structure and the formation of dense crystalline hydrate complexes of cement stone by the time of completion of concrete hardening. The objects of investigation were samples of grade B22.5 concrete without additives; containing a monoadditive - superplasticizer S-3; containing the complex additive. When designing the composition of additives for heavy concrete, we proceeded from the fundamental provisions of construction science that the complexity of the action of additives lies in the optimal combination of two main opposite processes in time and volume of the concrete matrix. The use of the caprolactam oligomer synthesized in the course of this investigation makes it possible to solve the problem of involving concentrated wastes of caprolactam production in the production turnover. The obtained caprolactam oligomers can be used in construction as plasticizers of concrete mixtures, as inhibitors of corrosion of steel reinforcement in the production of reinforced concrete products. Water-soluble oligomers of caprolactam, which reduce the time of dissolution of the superplasticizer C-3 and the dispersion of low-temperature catalyst in the volume of the concrete mixture being mixed, were synthesized. It was found that in the presence of the oligomer caprolactam in an amount of 10 to 20% of the mass. the dissolution rate of S-3 superplasticizer in water at a temperature of 20-21 °C increases by 2.0-2.2 times. This contributes to a better mixing of the components of the concrete mixture, primarily to improve the dispersion of the complex additive in the volume of the concrete mixture. The caprolactam oligomer used in this research work is an effective water-soluble wetting agent for the surface of particles of cement, sand, and crushed stone, which is very important for activating hydration and sorption processes during mixing of a concrete mixture. The increased wetting properties of the caprolactam oligomer are characterized by a wetting angle of 19.6 °.

A Sustainable Slit Jet FTIR Spectrometer for Hydrate Complexes and Beyond

Fourier transform infrared (FTIR) absorption spectroscopy of cold molecules and clusters in supersonic slit jet expansions complements and extends more sensitive action spectroscopy techniques and provides important reference data for the latter. We describe how its major drawback, large substance and carrier gas consumption, can be alleviated by one to two orders of magnitude via direct and continuous recycling of the gas mixture. This is achieved by a combination of dry rotary lobe and screw pump compression. The signal-to-noise ratio is boosted by the established buffered giant gas pulse technique with full interferogram synchronization. The buildup of water impurities typically limits the recycling gain, but is turned into a feature for the study of hydrate complexes of volatile molecules. Continuous operation with a single gas filling over several days becomes practical and useful. Decadic absorbances in the low ppm range are detectable and the mid infrared range can be recorded simultaneously with the near infrared. The less straightforward hydration number assignment of spectral features in direct absorption spectroscopy is supported by a gradual water buildup at a rate of less than 0.5 mg/h. A recent reassignment proposal for the water dimer OH stretching spectrum is refuted and vibrational spectra of vacuum-isolated 18O-water clusters are presented for the first time. Methanol docking on asymmetric ketones is used to illustrate the advantages and limitations of the recycling concept. Previous assignments of the hydrate complex of 1-phenylethanol are confirmed. Additional features of the setup await testing and refinement, but the recycling technique already substantially widens the applicability of direct absorption spectroscopy of neutral molecular clusters. It may be attractive for other high-throughput jet spectrometers.

Caged structural water molecules emit tunable brighter colors by topological excitation.

Intrinsically, free water molecules are a colourless liquid. If it is colourful, why and how does it emit the bright colours? We provided direct evidence that when water was trapped into the sub-nanospace of zeolites, the structural water molecules (SWs) exhibited strong tunable photoluminescence (PL) emissions from blue to red colours with unprecedented ultra-long lifetimes up to the second scale at liquid nitrogen temperature. Further controlled experiments and combined characterizations by time-resolved steady-state and ultra-fast femtosecond (fs) transient optical spectroscopy showed that the singly adsorbed hydrated hydroxide complex {OH-·H2O} as SWs in the confined nanocavity is the true emitter centre, whose PL efficiency strongly depends on the type and stability of the SWs, which is dominated by H-bond interactions, such as the solvent effect, pH value and operating temperature. The emission of SWs exhibits the characteristic of topological excitations (TAs) due to the many-body quantum electron correlations in confined nanocavities, which differs from the local excitation of organic chromophores. Our model not only elucidates the origin of the PL of metal nanoclusters (NCs), but also provides a completely new insight to understand the nature of heterogeneous catalysis and interface bonding (or state) at the molecule level, beyond the metal-centred d band theory.

Reply to the 'Comment on "Theoretical investigations on hydrogen peroxide decomposition in aquo"' by W. H. Koppenol, Phys. Chem. Chem. Phys., 2021, 23, DOI: 10.1039/D1CP03545B.

Following the comment article by Koppenol (W. H. Koppenol, Phys. Chem. Chem. Phys., 2021, 23, DOI: 10.1039/D1CP03545B), the H2O2 decomposition reaction mechanism based on the production of a de facto monovalent iron ion hydration complex, which is theoretically proposed in T. Tsuneda and T. Taketsugu, Phys. Chem. Chem. Phys., 2018, 20, 24992-24999, is reviewed from the standpoint of chemical kinetics. As a result, it is found that this decomposition mechanism is strongly supported by comparing the Gibbs energies of formation in consideration of the O-O bond dissociation of H2O2 for de facto monovalent iron, ferrous, and ferric ion complexes.