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Freezing-thawing cycling of salt solutions is ubiquitously important to fields varying from biochemistry to agriculture, climate, and geological engineering. However, understanding the dynamics of energy exchange and freezing-temperature TN shift during phase transition of the concentrated solutions remains elusive despite intensive investigations since the discovery of Homeister series in 1888. Here we address this issue by focusing on the performance of the hydrogen bond (O:H O) in the fraction fS molecules of the hydrating supersolid phase and in the remaining fraction fO molecules of the pristine phase during NaCl solution ice formation. The supersolid formation is related to the effect of ionic polarization that shortens and stiffens the H O bond, while lengthening and weakening the O:H non-bonding interactions in the hydration cells. The supersolid phase is gel-like, less dense, viscoelastic, and mechanically and thermally stable. We demonstrate that the polarization-weakening of the O:H non-bonding interactions of the supersolid phase reduces the TN of the solution and that the H O cooling contraction in the quasisolid (QS) phase of the pristine water absorbs energy during the Liquid-QS-Ice transition of solution. At fS = 1, neither TN nor energy absorption is resolved within the range of 273 ± 20 K. The least saturation number of molecules is 10 per pair of Na+ and Cl− ions. These findings shall help to develop solutions with tunable TN for practical applications and to understand the mechanism of energy exchange during phase transition in the temperature and time domains.

Raman phonon differential spectrometrics (DPS) and contact angle measurements resolved that solvation of the NaX (X = HSO4, NO3, ClO4, SCN) complex salts stiffens the H O stretching phonon from 3200 to ~ 3500 cm− 1 and softens the O:H nonbond phonon from 180 to ~ 70 cm− 1 with rising of solution surface stress. The solute capability of bond transition in terms of the fraction coefficient, follows the relation, fNaX(C) ∝ 1-exp(− C/C0) towards saturation, with C being the solute concentration and C0 the decay constant. Observations evidence that: (i) the solute ionic field electrification aligns, stretches, and polarizes its neighboring H2O molecules, which shortens the H O bond but lengthens the O:H nonbond via O O Coulomb repulsion; (ii) the effect of X− electrification on the O:H O bond relaxation varies with solute type and solute concentration. Exercises not only verify the essentiality of solvent O:H O bond cooperative relaxation and polarization but also demonstrate the power of DPS that resolves processes occurred upon solvation.

The low charge transfer efficiency of isolated semiconductors is an urgent challenge in the photocatalytic degradation of hazardous contaminants. In this work, CaIn2S4/MXene Ti3C2Tx Schottky heterojunctions are synthesized via a simple hydrothermal method and applied for tetracycline hydrochloride degradation and Cr(VI) reduction. Results show that Ti3C2Tx as a cocatalyst can limit the charge recombination and boost the absorption of visible light, thus promoting the photocatalytic efficiency of pure CaIn2S4. An optimized CaIn2S4-Ti3C2Tx hybrid has the highest catalytic rate in the degradation of tetracycline hydrochloride (96%) and reduction of Cr(VI) (98%). Studies probing the mechanism indicate that the photogenerated superoxide radicals and holes play a key role in the tetracycline hydrochloride degradation process, while electrons are core to the Cr(VI) reduction reaction. Besides the high photocatalytic efficiency, the CaIn2S4-Ti3C2Tx hybrids also exhibit outstanding photo-stability in the present conditions, suggesting the potential for practical use.

A localized, metastable, 5775-type defect is uncovered in the double-layer ice with and without Au(1 1 1) support from density functional theory calculations. Without destroying the total number conservation of the hydrogen bonds in the hexagonal ice, the defect only dislocates the molecules by 0.08 A associated with a 3.27% difference of the interaction energy. The high energy barrier, low quantum tunneling and thermal transporting probabilities hindered the transformation from the 6666 to the 5775 structures. This finding indicates that the defected ice is stable, and it tends to form during the ice growth instead of post-grown process.

Solvation of acid, base, and salt is ubiquitously important to all subject areas in chemistry, health care and life science. However, fine resolution of the solvation dynamics, solute-solvent molecular interactions, and solute capability of transforming the hydrogen bond (O:H O, or HB) and surface stress remain great challenge. Incorporating the notion of O:H O bond cooperativity with a strategy of differential phonon spectroscopy (DPS) has enabled resolution on the fraction and stiffness of the solvent HB from the mode of water to the hydration shells upon NaOH, NaI and HI solvation. Results show that Na+ and I+ ionic polarization shortens the H O bond and stiffens its phonon from 3200 to 3500 cm− 1 in the hydration shells. The H+ in the HI solution forms a H ↔ H anti-HB that disrupts the solution network and surface stress. The excessive electron lone pairs of OH– form the O : ⇔ : O super-HB that compresses the network, sharing the same effect of mechanical compression shifting the H O phonon from above 3100 cm− 1 to its below; the solute H O bond performs the same to the H O dangling bond at surface featured at 3610 cm− 1. The fraction coefficients or phonon abundance transition, fH = 0, fHO ∝ C, and fx ∝ 1-exp(− C/C0) (x = Na+ and I− and C the solute concentration) towards saturation, feature the solute capability of HB transformation. Practice not only confirms the essentiality of the H ↔ H anti-HB point fragilization, the O : ⇔ : O super-HB point compression, and the ionic polarization to the performance of the respective HI, NaOH, and NaI solutions, but also demonstrate the power of the DPS that enables fine-resolution of solvation dynamics and solute capabilities.

The bimetallic nanoparticles with core-shell structure have attracted much attention due to the excellent catalytic performance recently. We examined the thickness effect of the Pd overlayer/shell on Cu substrate/core on the catalytic ability of the overlayer using first-principle calculations and d-band center theory. It is found that overlayer thickness has the important effect on the d-band center of Pd layer. There is a quasi-linear relationship between the adsorption energies of O, O2, and CO and energy level of d-band center which is modulated by the overlayer thickness. The energy barriers of isolated O2 dissociation and CO oxidation are found to have an opposite trend with the shift of the d-band center. With this rule, the dissociation of O2 with the assistant of nearby CO is found to be easier on the surface of 2L-Pd/Cu(111).

A combination of photoelectron spectrometric analysis and density functional theory calculations has enabled reconciliation of the bond-energy-electron relaxation for the Ta(100, 110, 111) surfaces chemisorbed with oxygen at different coverages. Results show that increasing oxygen coverage lowers the adsorption energy associated with lattice reconstruction. Valence electrons transfer from Ta surface atoms to oxygen to create four excessive DOS features in terms of O Ta bonding, lone pairs of oxygen, Ta+ electron holes, and polarized Ta dipoles. Oxidation proceeds in the following dynamics: oxygen gets electrons from two neighboring Ta atoms left behind Ta+; the sp3-orbital hybridization takes place with additional two electron lone pairs, the lone pairs polarize the other two Ta neighbors becoming dipoles. X-ray photoelectron spectral analysis results in the 4f binding energy of an isolated Ta atom and its shift upon bond formation and oxidation. Exercises provide not only a promising numerical approach for the quantitative information about the bond and electronic behavior but also consistent insight into the electronic dynamics of metal oxidation.

Raman spectroscopy is employed to investigate bond phonon relaxation of layered (Mo, W)‐(S 2 , Se 2 ) by using the stimuli of number‐of‐layer. The results demonstrate that the dimer interaction dictates the blue shift of the E 1 2g phonon but the collective interaction of an atom with its z ‐neighbors governs the red shift of the A 1g phonon dynamics as the number‐of‐layer reduces.

In situ Raman spectroscopy revealed that transiting the concentrated NaI/H2O solutions to an ice VI phase and then into an ice VII phase at 298 K proceeds in a way different from that activated by the solute type. Unlike the solute type that raises both the critical pressures PC1 and PC2, for the liquid-VI, the VI-VII transition simultaneously occurs in the Hofmeister series order: I > Br > Cl > F ∼ 0; concentration increase raises the PC1 faster than the PC2 that remains almost constant at higher NaI/H2O molecular number ratios. Concentration increase moves the PC1 along the liquid-VI phase boundary and it finally merges with PC2 at the triple-phase junction featured at 350 K and 3.05 GPa. The highly-deformed H-O bond is less sensitive to the concentration because of the involvement of anion-anion repulsion that weakens the electric field in the hydration shells. Observations confirm that the salt solvation lengthens the O:H nonbond and softens its phonon but relaxes the H-O bond contrastingly. Compression, however, has the opposite effect from that of salt solvation. Therefore, compression recovers the polarization-deformed O:H-O bond first and then proceeds to the phase transitions. The anion-anion interaction discriminates the effect of NaI/H2O concentration from that of the solute type at an identical concentration on the phase transitions.

Skins of water and ice perform anomalously in capacities of hydrophobicity, lubricity, mass density, thermal stability, viscoelasticity, and phonon frequency with yet little knowledge about the mechanism behind these anomalies. We present the recent progress in this regard from the perspective of molecular undercoordination induced O:H-O bond segmental cooperative relaxation and nonbonding electron polarization. The skin molecular undercoordination shortens the intramolecular H-O covalent bond spontaneously from 1.0 to 0.84 Ǻ, while the Coulomb repulsion between oxygen anions lengthens the intermolecular O:H nonbond from 1.70 to 2.71 Ǻ associated with strong polarization. The O:H-O resultant elongation depresses the mass density to 0.75 g/cm 3 ; the polarization results the skin high stress, hydrophobicity, lubricity, viscoelasticity; the H-O contraction shifts its stretching vibration frequency from the bulk value of 3150 to 3450 cm -1 at skin and to 3650 cm -1 of vapor; the O:H elongation shifts its stretching mode from 210 of bulk to 180 cm -1 at skin. Therefore, molecular undercoordination induced O:H-O bond relaxation and the associated polarization govern the performance of molecules at the skins of water and ice.

The effects of microstructure on the creep behavior in a new developed Ni-Co base superalloy were investigated and two microstructures were obtained by different heat treatments. The results show that the air cooling microstructure, consisting of large spherical γ′ and small spherical γ′, resulted in a slow creep rate and small creep strain. While the slow cooling microstructure, consisting of large flowery γ′ and small spherical γ′, resulted in a fast creep rate and large creep strain. The γ channel and γ′ morphology are two main factors for these differences, the large γ channel and flowery γ′ in the slow cooling microstructure causing the dislocations slip easily in the γ matrix and cut into the γ′ precipitates with low stress.

Interfacial stability of electrode materials is crucial to the internal resistance and electrochemical performance of the lithium-ion batteries. However, determination of the cohesive energy at the heterogeneous interface remains yet a great challenge. Here, we report an approach and outcomes of quantifying the heterogeneous interfacial adhesion strength of the lithium-ion battery electrodes using the combination of the bond-order-length–strength (BOLS) correlation theory and X-ray photoelectron spectroscopy (XPS). Results revealed that the core-bond electrons of Ge/Si, Cu/Sn, Si/C and Ge/C alloys undergo quantum entrapment, while the C 1s electrons in Si/C and Ge/C alloys undergo polarization. Most strikingly, besides the interfacial adhesion energies, we are able to gain the local bond energy, energy density, atomic cohesive energy, and free energy at the interfaces. The presented approach and outcomes not only clarify the origin of the energetic behavior of the hetero-junction interface but also provide with reliable strategies for designing alloy electrodes with desired functions.

Although the alcohol–water mixtures are ubiquitously important to beverage and pharmacy industries, it remains yet puzzling how the alcohols interact with water molecules and how the alcohol molecules functionalize the hydrogen bond network of liquid water and body fluid. We show spectrometrically that alcohol hydration softens both the H–O bond and the O:H nonbond through hydrogen bond cooperative relaxation and associated charge polarization. Observations suggested that each of the dangling hydroxide group :O:H− (interacts with :O or –H+) and the dangling methyl group C–H+ (with –H+ or :O) is equally capable of interacting with H2O molecules in the form of O:↔:O point compressor, H+↔H+ point breaker, and O:H–O hydrogen bond at the alcohol–water interface without charge sharing or new bond formation. The alcohol–water O:H–O formation enables the solubility and hydrophilicity of the alcohol; the H+↔H+ breaker embrittles the hydration network; the O:↔:O compression shortens the O:H nonbond and lengthens the H–O bond. H–O softening is associated with heat emission and depression of solution melting temperature; the O:H nonbond softening (due to polarization) lowers the critical temperatures for freezing. Copyright © 2016 John Wiley & Sons, Ltd.

We show phonon spectrometrically that the unprecedented H 2 O: ↔ :O:H – compression resolves the performance of the base solution networks with “:” being the electron lone pair of oxygen. At hydration, LiOH, NaOH, KOH molecules dissolve each into a :O:H – hydroxide and cations of Li + , Na + , and K + , respectively. The cations serve as charge centers to polarize the neighboring water molecules and raise the solution skin stress (or surface tension). The :O:H – tetrahedron adds, however, three lone pairs and one bonded H + proton to the solution matrix, turning the initially 2N lone pairs into 2N + 3 and the 2N bonded H + into 2N + 1 with an additional O 2– anion. This hydration process breaks the conservation of the 2N lone pairs and protons with two extra lone pairs that only can form a H 2 O: ↔ :O:H – super hydrogen bond (super-HB) with strong repulsivity. In addition to the H O bond of the :O:H – featured at 3610 cm − 1 , the internal H 2 O: ↔ :O:H – compression has an identical effect of mechanical compression, shortening the O:H nonbonds and stiffening their phonons from below 200 cm − 1 to the above. Meanwhile, compression lengthens the network H O bonds and softens their phonons from above 3150 cm − 1 to below. The network H O bonds elongation decreases their energy from ~ 4.0 to ~ 2.7 eV at hydration, which heats the solution as one often observes. The H 2 O: ↔ :O:H – super-HB compressor and the alkali cation polarizor form the keys to the base hydration networks and the properties.

Density functional computation revealed that in YOH solvation (Y = Li, Na, and K), the Y+ cation locates eccentrically at the interstitial hollow site to form the Y+·4H2O unit, and the hydroxyl adds an excessive electron lone pair ":" to form a OH-·H2O unit where the hydroxide stays in the the center. The surrounding four oriented H2O neighbors interact with the Y+ through Y+ ↔ H+ repulsion and Y+:O2- attraction, causing the Y+ eccentric dislocation by some 0.80 A. The ":" turns one O:H-O bond into the O: ⇔ :O super hydrogen bond by altering H2O·4H2O into HO-·4H2O. The repulsive Y+ ↔ H+ enlarges its separation and the attractive Y+:O shortens itself, showing the anisotropic polarization of the Y+ cation. The anisotropic Y+ polarizability, O: ⇔ :O compressibility, and the H-O bond contraction of the solute OH- distorts the solute bonding network and disperses the O:H-O segmental phonon frequencies, as confirmed spectroscopically.

Pentazole anion, the best candidate for full-nitrogen energetic materials, can be isolated only from acidic solution for unclear reasons, which hinders the high-yield realization of a full-nitrogen substance with higher energy density. Herein, we report for the first time the discovery of the dual aromaticity (π and σ) of cyclo-N

Water dissolves salt into ions and then hydrates the ions to form an aqueous solution. Hydration of ions deforms the hydrogen bonding network and triggers the solution with what the pure water never shows such as conductivity, molecular diffusivity, thermal stability, surface stress, solubility, and viscosity, having enormous impact to many branches in biochemistry, chemistry, physics, and energy and environmental industry sectors. However, regulations for the solute-solute-solvent interactions are still open for exploration. From the perspective of the screened ionic polarization and O:H-O bond relaxation, this treatise features the recent progress and a perspective in understanding the hydration dynamics of Hofmeister ions in the typical YI, NaX, ZX2, and NaT salt solutions (Y = Li, Na, K, Rb, Cs; X = F, Cl, Br, I; Z = Mg, Ca, Ba, Sr; T = ClO4, NO3, HSO4, SCN). Phonon spectrometric analysis turned out the f(C) number fraction of bonds transition from the mode of deionized water to the hydrating. The linear f(C) ∝ C form features the invariant hydration volume of small cations that are fully-screened by their hydration H2O dipoles. The nonlinear f(C) ∝ 1 - exp.(-C/C0) form describes that the number insufficiency of the ordered hydrating H2O dipoles partially screens the anions. Molecular anions show stronger yet shorter electric field of dipoles. The screened ionic polarization, inter-solute interaction, and O:H-O bond transition unify the solution conductivity, surface stress, viscosity, and critical energies for phase transition. Accepted version

The electronic structures of two-dimensional (2D) indium (In) and bismuth (Bi) metal on BN nanosheets are systematically studied using hybrid density functional theory (DFT). We found that 2D In and Bi metal effectively modulate the band gap of a BN nanosheet. We also found that the indirect band gap of the 2D In and Bi metal electronic structures are 0.70 and 0.09 eV, respectively. This modulation originates from the charge transfer between the 2D metal and BN nanosheet interfaces, as well as from the electron redistribution of the In/BN and Bi/BN heterojunctions of the s and p orbitals. Our results provide an insight into 2D In/BN and Bi/BN heterojunctions, which should be useful in the design of 2D In and Bi metal-semiconductor-based devices. Published version This work was supported by Chongqing Municipal Education Commission (Grant No. KJ1712310).

Charge injection in terms of lone pairs ‘:’, protons, and ions upon acid and base solvation mediates the hydrogen bonding network and properties of Lewis solutions, and is ubiquitously important in many subject areas of Chemical Physics. This work features the recent progress and future trends in this aspect with a focus on the solute–solvent interactions and hydrogen bond (O:H–O or HB) transition from the vibration mode of ordinary water to the hydrating states. A combination of the O:H–O bond cooperativity notion, differential phonon spectrometrics, calorimetric detection, and quantum computations clarified the solute capabilities of O:H–O bond transition in HX and YOH (X = Cl, Br, I and Y = Li, Na, K) solutions. The H+ and the lone pair do not stay alone to move or shuttle freely between adjacent H2O molecules, but they are attached to a H2O molecule to form (H3O+ and OH−)·4H2O tetrahedral motifs, which transits an O:H–O bond into the H↔H anti-HB point breaker in acidic solutions and into the O:⇔:O super-HB compressor and polarizer in basic solutions, respectively. H↔H disrupts the solvent network and surface stress, having the same effect of liquid heating on HB bond relaxation and thermal fluctuation on surface stress. The O:⇔:O compression lengthens and weakens the solute H–O bond, which heats up the solution during solvation. The H–O bonds due to H3O+ contract by 3% and due to OH− shrink by 10%. The Y+ and X− ions perform in the same manner as they do in salt solutions to form hydration shells through electrostatic polarization and hydrating H2O dipolar screen shielding. Focusing more on the O:H–O bond transition would be even more promising and revealing than on the manner and mobility of lone pair and proton transportation.

Fabrication of high-performance electrodes from waste biomass has attracted increasing attention among the energy storage and conversion field. In this work, we have synthesized nitrogen-doped activated carbon by a simultaneous pyrolysis/activation method from waste bones. It is found that the specific surface area and pore structure of as-synthesized carbon depends on the carbonization temperature (500-800 °C), and the highest specific surface area is 1522 m2 g-1. The electrochemical properties of Pork bone, Blackfish bone, Eel bone based activated carbon (PBAC, BFAC, EBAC) mainly depend on their micro-/mesoporosity. Three samples PBAC-600, BFAC-600 and EBAC-600, which have higher ratio of micropore surface area and nitrogen content, exhibit enhanced specific capacitance of 263, 302 and 264F g-1 in 6 M KOH electrolyte. Furthermore, the assembled symmetric supercapacitors of PBAC-600 can deliver energy density as high as 7.0 and 26.2 Wh Kg-1 in the aqueous and ionic liquid electrolyte, respectively. Such excellent performance can be attributed to the microporous structure, reasonable pore size distribution and nitrogen self-doping of the activated carbon. This research indicates that waste bones have great potential for mass fabrication of the activated carbon electrodes for energy storage applications. This research was supported by Zhejiang Provincial Natural Science Foundation of China under Grant No. LQ18E030005, LY18E020007, LY18E060005, LY19E020006.

The OH− and the H2O2 possess each two excessive pairs of electron lone pairs “:” that form an O:⇔:O super−HB upon solvation. The O:⇔:O compression shortens the O:H nonbond and stiffens its phonon but relaxes the H–O bond oppositely. The H–O bond elongation emits energy to heat up the solution. Bond-order-deficiency shortens the solute H–O bond and stiffens its phonon to 3550 cm−1 for H2O2 and 3610 cm−1 for OH−. However, the O:⇔:O compression annihilates the weak cationic polarization. The H2O2 is less than the OH− capable of transiting the solvent H–O bonds and surface stress. The linear fraction coefficient f(C) suggests that the OH− be less sensitive to other solutes. The resultant of solvent exothermic H–O elongation by O:⇔:O compression and the solute endothermic H–O contraction by bond order deficiency heats up the solutions. Observations evidence not only the significance of the inter-lone-pair interaction but also the universality of the bond order-length-strength (BOLS) correlation to aqueous solutions.

A combination of the spatially- and temporally-resolved phonon spectroscopies has enabled calibration of hydrogen bond transition from the vibration mode of heavy water to the core-shell structured nanodroplets and to the ionic hydration shells of salt solutions in terms of phonon abundance-lifetime-stiffness. It is uncovered that charge injection by salt solvation and skin formation by molecular undercoordination (often called confinement) share the same supersolidity characterized by H–O (D–O as a probe) bond contraction, O:H nonbond elongation, and polarization. Such a process of bond transition stems the solution viscosity, surface stress, and slowing down of the molecular dynamics and diffusivity. The nanodroplet skin reflection further hinders phonon energy dissipation associated with longer D–O phonon lifetime. Financial support received from National Natural Science Foundation of China (Nos. 11872052(YL); 21875024(CQ)), the Science Challenge Project (No. TZ2016001) of China is acknowledged.

Water dissolves salt into ions and then hydrates the ions in an aqueous solution. Hydration of ions deforms the hydrogen bonding network and triggers the solution with what the pure water never shows such as conductivity, molecular diffusivity, thermal stability, surface stress, solubility, and viscosity, having enormous impact to many branches in biochemistry, chemistry, physics, and energy and environmental industry sectors. However, regulations for the solute-solute-solvent interactions are still open for exploration. From the perspective of the screened ionic polarization and O:H–O bond relaxation, this chapter is focused on understanding the hydration dynamics of Hofmeister ions in the typical YI, NaX, ZX2, and NaT salt solutions (Y = Li, Na, K, Rb, Cs; X = F, Cl, Br, I; Z = Mg, Ca, Ba, Sr; T = ClO4, NO3, HSO4, SCN). Phonon spectrometric analysis turned out the f(C) fraction of bond transition from the mode of deionized water to the hydrating. The linear f(C) ∝ C form features the invariant hydration volume of small cations that are fully-screened by their hydration H2O dipoles. The nonlinear f(C) ∝ 1 − exp(−C/C0) form describes that the number insufficiency of the ordered hydrating H2O diploes partially screens the anions. Molecular anions show stronger yet shorter electric field of dipoles. The screened ionic polarization, inter-solute interaction, and O:H–O bond transition unify the solution conductivity, surface stress, viscosity, and critical energies for phase transition.

The excessive number of H+ or “:” and their asymmetrical distribution determines the performance of their surrounding water molecules in a way different from that of ordinary water. The naked lone pairs and protons are equally capable of interacting with the solvent H2O molecules to form O:H vdW bond, O:⇔:O super–HB or H↔H anti-HB without charge sharing or new bond forming. Solvation examination of alcohols, aldehydes, formic acids, and sugars reveals that O:H–O formation enables the solubility and hydrophilicity of alcohol; the H↔H anti-HB formation and interface structure distortion disrupt the hydration network and surface stress. The O:H phonon redshift depresses the freezing point of sugar solution of anti-icing.

Solvation is a process of aqueous charge injection in the forms of H+, electrons, electron lone pairs, cations, anions, or molecular dipoles with long- and short-range interaction. A solute interacts with its neighboring H2O molecules through the O:H vdW, O:⇔:O super-HB compression, H↔H anti-HB fragilization, ionic or dipolar polarization with screen shielding, and solute-solute interaction and their combinations. The hydration H2O dipoles tend to be aligned oppositely along the electric field screen in turn the electric fields of the solute. The ionic size, charge quantity, and the numbers and spatial distribution of H+ and “:” determine the form of solute-solvent interaction. A solute may be sensitive or not to interference of other solutes depending on the solute size and its extent of screening. The intermolecular nonbond and intramolecular bond cooperative relaxation determines the performance of a solution in terms of surface stress, solution viscosity, energy absorption-emission-dissipation at solvation, solvation temperature, thermal stability, critical pressures and pressures for phase transition.

An incorporation of the hydrogen bond cooperativity theory to the DPS strategy and surface stress (contact angle) detection could resolve the solvation bonding and nonbonding dynamics and solute capabilities. The enabled information includes bond length and stiffness transition, electron polarization, and the fraction of bonds transformed from the mode of ordinary water to the hydration shells. A combination of the DPS and the ultrafast IR spectroscopy would be more revealing towards solute-solvent and solute-solute molecular interactions, solute capabilities, and solution properties. The DPS is focused on the solvation O:H–O segmental cooperative bonding dynamics and the ultrafast IR on molecular motion dynamics by measuring phonon relaxation time.

Solvation dissolves the HX into an H+ and an X−. The H+ bonds to a H2O to form a firm H3O+ and a H↔H anti − HB point breaker. The H–O bond due H3O+ is 3% shorter and the associated O:H nonbond is 60% longer than normal. The H↔H compression shortens its nearest O:H nonbond by 11% and lengthens the H–O by 4%. The X− point polarizer shortens the H–O bond and stiffens its phonon but relax the O:H nonbond oppositely in the supersolid hydration shell. The X− solute capability of bond transition follows the I > Br > Cl order in the form of fx(C) ∝ 1 − exp(−C/C0) towards saturation because of the involvement of the X−↔X− interaction that weakens the hydration-shell electric field at higher concentrations. However, the H+ neither hops or tunnels freely nor polarize its neighbors, fH(C) = 0. The H↔H has the same effect of heating on the surface stress and solution viscosity disruption.

Full solar spectrum active heterogenous photocatalysis for environmental applications remains highly challenging. Here we report the novel Cu2In2ZnS5/Gd2O2S:Tb (CG) hybrid photocatalysts via a facile solvothermal method for efficient Cr(VI) and CO2 reduction. The narrow band gap energies of the CG hybrid photocatalysts synthesized via a facile solvothermal method show excellent absorption and catalytic activity in the full solar spectrum. High Cr(VI) reduction rate of 90% and CH4 production rate of 57.73 μmol h−1 g−1 are achieved for CG hybrid photocatalyst with 1 wt.% Gd2O2S:Tb. The excellent performance is due to the fact that in the hybrid, Gd2O2S:Tb as cocatalyst, provides more active sites and inhibits the recombination of charge carriers due to the synergetic effect between Cu2In2ZnS5 and Gd2O2S:Tb, consequently improving the photocatalytic reduction activity. Financial support from the Province Natural Science Foundation of Zhejiang (No. LY18E060005, LY18E020007 and LQ18E030005), National Natural Science Foundation of China (No. 21401180) are gratefully acknowledged.

Supersolidity of ice, which was proposed in 2013 and intensively verified since then [C. Q. Sun et al., Density, Elasticity, and Stability Anomalies of Water Molecules with Fewer than Four Neighbors, J. Phys. Chem. Lett., 2013, 4, 2565-2570; C. Q. Sun et al., Density and phonon-stiffness anomalies of water and ice in the full temperature range, J. Phys. Chem. Lett., 2013, 4, 3238-3244], refers to the water molecules being polarized by molecular undercoordination, which is associated with the skin of bulk ice, nanobubbles, and nanodroplets (often called confinement), or by the electrostatic field of ions in salt solutions [X. Zhang et al., Mediating relaxation and polarization of hydrogen-bonds in water by NaCl salting and heating, Phys. Chem. Chem. Phys., 2014, 16(45), 24666-24671; C. Q. Sun et al., (H, Li)Br and LiOH solvation bonding dynamics: molecular nonbond interactions and solute extraordinary capabilities, J. Phys. Chem. B, 2018, 122(3), 1228-1238]. From the perspective of hydrogen bond (O:H-O or HB with ":" representing the lone pairs on O2-) cooperative relaxation and polarization, this review features the recent progress and recommends future trends in understanding the bond-electron-phonon correlation in the supersolid phase. Supersolidity is characterized by a shorter and stiffer H-O bond, longer and softer O:H nonbond, deeper O 1s energy band, and longer photoelectron and phonon lifetimes. The supersolid phase is less dense, viscoelastic, and mechanically and thermally more stable. Furthermore, O:H-O bond cooperative relaxation offsets the boundaries of structural phases and increases the melting point while lowering the freezing temperature of ice, which is known as supercooling and superheating. Accepted version

Atomic undercoordination entitles the inert gold even more noble at sites pertained to adatoms, defects, kinks, and skins of bulk and sized crystals with unclear mechanism. Systematic analysis of the electron emission spectra of XPS and STM/S of the undercoordinated gold atoms revealed that the 4f and 5d bands undergo quantum entrapment while the 6s level is subject to localization and polarization because of the undercoordination-induced local bond contraction and bond strength gain – named bond order-length-strength correlation and nonbonding electron polarization (BOLS-NEP). Such a bonding and electronic relaxation result in the undercoordination derivacy of properties such as its extraordinary catalytic ability that the bulk gold does never demonstrate. The BOLS-NEP in the skin-electrical-double-layer shell dictates the nanostructure size dependency of the known bulk properties such as the chemical potential, inner potential constant, elasticity, and thermal stability. The exercise not only establishes a powerful means monitoring the Hamiltonian perturbation by atomic undercoordination but also offers information on the atomic-site-resolved local bond length, bond energy, chemical potentials, energy density, and atomic cohesive energy and the associated properties. Support from National Natural Science Foundation of China (21875024) is acknowledged.

We show that nanocrystals share a common and intrinsic skin electric-double-layer (EDL). The EDL is determined to be 2.14 regular-bond-length thick using differential phonon spectroscopy that distills phonon abundance transiting from the core region to the EDL of the sized crystals. Theoretical reproduction of the size-resolved Raman shift for Si, CeO₂, and SnO₂ nanocrystals, elasticity of ZnO, and the XPS 2p energy shift, band gap expansion and melting point shift of Si crystals confirmed the universality of the EDL of which bonds are shorter and stronger than those inside the bulk or the particle core interior. The EDL bond contraction and the associated electron entrapment and polarization originate, and the EDL volume quantifies the size dependency of nanostructures while the electron entrapment or polarization entitles the undercoordinated single or edge atoms with properties that a bulk does never show. Financial support received from the National Natural Science Foundation (No 21273191) of China, is gratefully acknowledged.

Metal-free catalyst with favorable advantages of nonpolluting, cost-effective and stable catalytic performances may be used in various redox reactions. In this paper, we design a series of C6H4NO2/g-C3N4 composites by combining a polar nitrobenzene molecule with g-C3N4 monolayer using density functional theory calculations. The electrocatalytic performances during oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are substantially improved thanks to the electron redistributions of g-C3N4 substrate. One composite specimen exhibits the lowest bi-directional OER/ORR overpotentials of 0.14/0.14 V, and the most stable composite specimen has OER/ORR overpotentials of 0.27/0.39 V. The number of active electrons in active atom, as descriptor of catalytic activity, can accurately estimate the OER and ORR activity of metal-free electrocatalysts. The modification strategy would be extended to design high-efficiency metal-free electrocatalysts.

We show the reconciliation of the strain (e)-, pressure (P)-, and layer-number (N)-dependence of the phonon frequency and photon energy shifts for MX2 in terms of stimulated bond relaxation, with quantification of the coefficients of bond length and energy relaxation, the bond nature index, force constant, and cohesive energy density. We found that (i) atomic under-coordination shortens and stiffens the M–X bond, which widens the bandgap; (ii) the directional strain governs phonon-frequency splitting and narrowing; and (iii) homogenous mechanical compression induces the opposite effect of stretching.

A combination of the differential Raman spectrometrics and contact-angle measurements has enabled resolution of the hydrogen bond (HB, O:H O) relaxation and molecular dynamics in the NaX hydration shells. Observations suggest that the aqueous ions create each an electric field to form the hydration shells through O:H O bond elongation and polarization. The ionic polarization shares the same, and even stronger, effect of molecular undercoordination that shortens the H O bond and stiffen its phonon, and meanwhile, the O O Coulomb repulsivity lengthen and soften the O:H nonbond with an association of polarization. O:H O bond electrification raises not only the structure order of molecules and the viscosity in the hydration shells but also the skin stress and thermal stability of the solution. Exercises not only deepen our insight into the salt solute-solvent interaction involved in the Hofmeister series in terms of O:H O bond electrification but also provide a powerful means quantifying the dynamic, local, molecular-site-resolved information regarding the O:H O bond cooperativity in aqueous solutions.

Inspired by nacre, we designed biomimetic metal–ceramic composites in which hard and ductile phases were alternately arranged. We first prepared lamellar-structured TiC scaffolds with 25, 30 and 35 vol% solid loadings using a unidirectional freeze casting technique and then measured wetting and infiltration dynamics for a commercial Al cast alloy, ZL107, with the main composition of Al–7Si–5Cu on the porous TiC scaffold using a modified sessile drop method at 850 °C. The wetting was affected by liquid spreading at horizontal surface and infiltration in depth, while the latter played a dominant role in the decrease in contact angle. On the basis of the wetting results, the lamellar ZL107/TiC composites were successfully fabricated by pressure infiltration of the molten ZL107 alloy into porous TiC scaffolds and their mechanical properties were evaluated. The compressive strength and elastic modulus increased while bending strength decreased with increasing TiC content, giving maximum values of 1166 ± 20 MPa, 205 ± 2 GPa and 363 ± 5 MPa, respectively. Formation of (Alm,Si1 − m)3Ti, Al3Ti and Al4C3 phases in the composites was presumed to deteriorate the toughness of the composites, leading to brittle fracture under loading. Keywords: Freeze casting, Pressure infiltration, Wetting, Mechanical properties

Albeit its chemical inertness, rare gas doping can substantially enhance the quantum size effect of nanocrystals, yet little attention has been paid on this fascination and the mechanism behind remains unclear. Here, we show that the rare gas dopant breaks bonds of its neighboring atoms, which effects the same to atomic under-coordination on the bond strain, energy quantum entrapment, and valence electron polarization of Li and Na clusters. Consistency between density functional theory calculation and the bond-order-length-strength correlation prediction revealed that the bond strain by 16.86% and 21.12% before and after He doping for Na30 clusters. Observations suggest an effective yet simple means to modulate the physical properties by doping the inert gases.

Water skin is the toughest of ever known with a mechanism that remains unclear. We show phonon spectrometrically that molecular undercoordination induced hydrogen bond (O:H O) relaxation and nonbonding electron polarization furnished the skin with the supersolid nature – less dense, elastic, thermally more stable than the bulk. Heating from 5 to 95 °C stiffens the skin H O phonon (or bond stiffness) from 3443 cm− 1 by 0.38%, and the bulk phonon from 3239 cm− 1 by 1.48%, but softens the H O dangling bonds from 3604 cm− 1 by − 0.40%. Heating also changes the respective molecular structural order and phonon abundance by − 8.4/− 19.7%, 4.9/− 2.6%, and 13.0/137.0%. Observations also evidenced that both heating and molecular undercoordination have the same effect on O:H O bond relaxation but opposite on polarization, which improves our understanding of the anomalous skin of liquid water.

Spin-resolved density functional theory examination revealed that 0, ±1e, and ±2e additional surface charge has impact to the bond-electron-energy relaxation, and the associated catalystic and magnetic properties of MN atomic clusters (M = Ag, Cu, Pt, and Rh; N = 13–147 atoms). Trends consistency between calculations and experimental observations confirmed our predictions [Chem. Rev. 2015, 115, 6746] that the shorter-and-stronger bonds between undercoordinated atoms induce the local densification and quantum entrapment of the core electrons, which in turn polarize the valence electrons dominating the catalytic and magnetic performance of the clusters. The excessive charge states has an important impact to the magnetization of MN. Specifically, even excessive charge states addition induces magnetization of all the MN clusters while odd excessive charge addition affects only Pt and Rh clusters. Observations provide insight on the relationship between excessive charge and the intrinsic effect of the atomic u...

We examined the combined effect of atomic under- and hetero-coordination on the bond relaxation and electronic binding energy of Sc, Zr, and ScZr alloying using a combination of the bond-order–length–strength (BOLS) correlation and density functional theory (DFT) calculations. Observations strongly emphasize the relevance of core-level shifts as reliable X-ray photoelectron spectroscopy experimental descriptors of core–shell catalysis reactivity, along with under-coordinated atoms in bimetallic transition metal systems. The BOLS–DFT method provides enhanced catalysis reactivity and detects surface and alloy configurations, opening up the possibility to investigate more complex systems with irregularly under- and hetero-coordinated atoms.

We systematically examined the effects of number-of-layer, pressure, and temperature on the bond length and energy, Debye temperature, atomic cohesive energy, and binding energy density for layered black phosphorus using bond–phonon–photon spectrometric methods. We clarified the following: (1) atomic under-coordination shortens and stiffens the PP bond, which raises the B2g and Ag2 phonon frequency and widens the bandgap, (2) bond thermal elongation and weakening soften all phonon modes, and (3) bond mechanical compression has the opposite effect of heating on phonon frequency relaxation. The phonon and photon energy depends on the bond length and energy, which determines the relevant elasticity and thermal stability of layered structure. More broadly, the approaches and findings of this work provide both insight into and efficient tools for further exploration of unusual behaviors of other two-dimensional substance. Copyright © 2016 John Wiley & Sons, Ltd.

The solute–solvent interaction of salts has a striking impact on various biological and industrial processes but its mechanism remains yet mysterious despite intensive studies since 1888 when Franz Hofmeister established the salt series. A combination of confocal Raman spectroscopy and contact angle measurements has enabled us to resolve the hydrogen bond relaxation (O:H―O, HB) and the associated charge polarization dynamics at different molecular site because of alkali halides hydration. Results show consistently that salt hydration softens the O:H phonon but stiffens H―O phonon cooperatively. The extent of HB relaxation and polarization is proportional to the electronegativity difference and ionic radius, following the order of Hofmeister series: X (R/η) = I (2.2/2.5) > Br (1.96/2.8) > Cl (1.81/3.0) > F (1.33/4.0) ≈ 0 for anions, and Y(R/η) = Na (0.98/0.9) > K (1.33/0.8) > Rb (1.49/0.8) > Cs (1.65/0.8) for cations. Observations suggest that ions create each an electric field that aligns, stretches, and polarizes water molecules, which relaxes the O:H―O bond cooperatively, depresses the molecular dynamics, and enhances the hydration shell viscosity and the skin stress. Exercises also demonstrate that Raman spectroscopy performs as a powerful tool for probing the molecular-site-resolved HB network relaxation dynamics in terms of phonon stiffness, molecular fluctuation dynamics, and phonon abundance transition under external stimulus. Copyright © 2016 John Wiley & Sons, Ltd.

We examined the effect of group-IVA doping on the electronic structure and transmittance of ZnO using first-principle calculations. All these doped ZnO materials are found to perform n -type conductive behavior. Si-doped ZnO and Pb-doped ZnO are found to have larger optical band gap than those of Ge-doped ZnO and Sn-doped ZnO. The transmittance of Si-doped ZnO is found to be high in both UV and visible region. The enhancement of UV region transmittance can be attributed to the enhanced optical band gap, while the reduction of visible region transmittance is due to the intraband optical transition.