Search

We resolved the O:H-O bond transition from the mode of ordinary water to its hydration in terms of its phonon stiffness (vibration frequency shift Δω), order of fluctuation (line width), and number fraction (phonon abundance), fx(C) = Nhyd/Ntotal. The fx(C) follows fH(C) = 0, fLi(C) ∝ fOH(C) ∝ C, and fBr(C) ∝ 1 - exp(-C/C0) toward saturation with C being the solute concentration. The invariant dfx(C)/dC suggests that the solute forms a constantly sized hydration droplet without responding to interference of other ions because its hydrating H2O dipoles fully screen its electric field. However, the number inadequacy of the highly ordered hydration H2O dipoles partially screens the large Br-. The Br- then interacts repulsively with other Br- anions, which weakens its electric field and the fBr(C) approaches saturation at higher solute concentration. The consistency in the concentration trend of the fLiBr(C), the Jones-Dole viscosity η(C), and the surface stress of LiBr solution clarifies their common origin of ionic polarization. The resultant energy of the solvent H-O exothermic elongation by O: ⇔ :O repulsion and the solute H-O endothermic contraction by bond-order deficiency heats up the LiOH solution. An estimation of at least 0.15 eV (160% of the O:H cohesive energy of 0.1 eV) suggests that the H-O elongation is the main source heating up the solution, while the molecular motion, structure fluctuation, or even evaporation dissipates energy caped at 0.1 eV. [ABSTRACT FROM AUTHOR]

It has long been puzzling regarding the atomistic origin of the pressure-induced Raman optical phonon stiffening that generally follows a polynomial expression with coefficients needing physical indication. Here, we show that an extension of the bond−order−length−strength correlation mechanism and a local bond average approach to the pressure domain have led to an analytical solution to connect the pressure-induced Raman optical phonon stiffening directly to the bonding identities of the specimen and the response of the bonding identities to the applied stimulus. It is found that the pressure-induced blue-shift of Raman optical phonons arises from the bond compression and energy storage exerted by the compressive stress. Agreement between predictions and experimental measurements lead to the clarification of the detailed form for the polynomial coefficients, which provide an atomistic understanding of the physical mechanism of the external pressure induced energy gain, thermally induced bond expansion, as well as means of determining the mode atomic cohesive energy in a specimen. [ABSTRACT FROM AUTHOR]

An approach of local bond average (LBA) has been developed by extending the bond-order-length-strength correlation (Sun, C. Q. Prog. Solid State Chem.2007, 35, 1− 159) to temperature domain for the mechanism of the thermally driven bond expansion in a solid specimen. It is shown that the detectable quantities of a solid can be connected directly to the bonding identities and the response of the bonding identities to the stimulus of temperature change, being free from using the concepts in classical thermodynamics or hypothetical constants. The success of the LBA approach has been evidenced by fitting the observations from a number of specimens with derived information of atomic cohesive energy, which may go beyond the currently available approaches. [ABSTRACT FROM AUTHOR]

Water nanobubbles manifest fascinatingly higher mechanical strength, higher thermal stability, and longer lifetime than macroscopic bubbles; thus, they provide an important impact in applications in the biomedical and chemical industries. However, a detailed understanding of the mechanism behind these mysteries of nanobubbles remains a challenge. Consistency between quantum computations and Raman spectrometric measurements confirmed our predictions that a nanobubble skin shares the same supersolidity with molecular clusters, skins of bulk water, and water droplets because of molecular undercoordination (fewer than four nearest molecular neighbors). Molecular undercoordination (coordination number Z cluster < Z surface < Z bubble < Z bulk = 4) shortens/extends the H-O/O:H bond and stiffens/softens its corresponding stretching phonons, whose frequency shift is proportional to the square root of the cohesive energy and inversely proportional to the segmental length. The strongly polarized O:H-O bond slows the molecular dynamics and increases the viscosity. The freezing temperature is lowered by the softened O:H bond, and the melting temperature is enhanced by the stiffened H-O bond. Therefore, the supersolid skin makes the nanobubbles thermally more stable, less dense, and stiffer and slows the dynamics of their molecular motion. [ABSTRACT FROM AUTHOR]

The article discusses coordination and multifield resolved spectrometries of electron. It mentions that atomistic information of bond relaxation has been resolved by nonbonding electron polarization (NEP). It mentions that coordination-resolved spectrometry has made shifts of energy levels. It mentions that the performance of local bonds and electrons in various energy levels has increased bonding capacities.

It has long been puzzling that water nanodroplets undergo simultaneously "supercooling" at freezing and "superheating" at melting. Recent progress (Sun et al. J. Phys. Chem. Lett.2013, 4, 2565, 3238) enables us to resolve this anomaly from the perspective of hydrogen bond (O:H-O) specific heat disparity. A superposition of the specific heat ?x(T) curves for the H-O bond (x = H) and the O:H nonbond (x = L) defines two intersecting temperatures that form the ice/quasi-solid/liquid phase boundaries. Molecular undercoordination (with fewer than four nearest neighbors in the bulk) stretches the ?H(T) curve by raising the Debye temperature TDH through H-O bond shortening and phonon stiffening. The ?H(T) stretching is coupled with the ?L(T) depressing because of the Coulomb repulsion between electron pairs on oxygen ions. The extent of dispersion varies with the size of a droplet that prefers a core-shell structure configuration?the bulk interior and the skin. Understandings may open an effective way of dealing with the thermodynamic behavior of water droplets and bubbles from the perspective of O:H-O bond cooperativity. [ABSTRACT FROM AUTHOR]

A combination of the Lagrangian mechanicsof oscillators vibration,molecular dynamics decomposition of volume evolution, and Raman spectroscopyof phonon relaxation has enabled us to resolve the asymmetric, local,and short-range potentials pertaining to the hydrogen bond (O:H–O)in compressed ice. Results show that both oxygen atoms in the O:H–Obond shift initially outwardly with respect to the coordination origin(H), lengthening the O–O distance by 0.0136 nm from 0.2597to 0.2733 nm by Coulomb repulsion between electron pairs on adjacentoxygen atoms. Both oxygen atoms then move toward right along the O:H–Obond by different amounts upon being compressed, approaching identicallength of 0.11 nm. The van der Waals potential VL(r) for the O:H noncovalent bond reachesa valley at −0.25 eV, and the lowest exchange VH(r) for the H–O polar-covalentbond is valued at −3.97 eV. [ABSTRACT FROM AUTHOR]

Incorporating the tight-binding theory and the bond order–length–strength(BOLS) correlation into the X-ray photoelectron spectra of Ag(111)and (100) surfaces and the Auger electron spectra of Ag nanoparticlesdeposited on Al2O3and CeO2substrateshas led to quantitative information of the 3d5/2and thevalence binding energies of an isolated Ag atom and their shifts uponbulk, defect, surface, and nanocrystal formation. It is clarifiedthat the globally positive energy shifts originate from the undercoordination-inducedGoldschmidt–Pauling bond contraction and the associated localquantum entrapment and the heterocoordination-induced bond naturealteration at the particle–substrate interfaces. Perturbationto the Hamiltonian by atomic ill-coordination dictates the energyshift that is proportional to the bond energy at equilibrium. Theoreticalreproduction of the measured spectroscopic data derived that the 3d5/2energy of an isolated Ag atom shifts from 363.02 to 367.65eV and the valence band center from 0.36 to 8.32 eV upon bulk formation.The extended Wagner plots revealed the coefficients of valence rechargingand potential screening to be 1.21 and 1.56 for Ag interacting withAl2O3substrate and 1.15 and 1.50 for Ag withCeO2, respectively. Exercises exemplify the enhanced capabilitiesof XPS and AES in determining quantitative information regarding theevolution of the local bond length, bond energy, binding energy density,and atomic cohesive energy, with the coordination and chemical environment. [ABSTRACT FROM AUTHOR]

The article focuses on the results of the formulation, correlation, clarification, and quantification of the behavior of zinc oxide (ZnO) for five years. It states the exercises undertaken for the bond-band correlation were based on three frameworks namely bond-order-length-strength (BOLS) correlation, nonbonding electron polarization (NEP), and local bond averaging (LBA) method. It explores the catalytic performance, dilute magnetism, and superhydrophobicity of ZnO.

In this work, a superhydrophilic polypyrrole (PPy) nanofiber network is electrochemically synthesized in an aqueous solution by using phosphate buffer solution (PBS) in the absence of templates, surfactants and structure-directing molecules. FESEM, X-ray diffraction, UV−visible absorption, and contact angle measurement were employed to characterize the nanofiber network. The effect of synthetic conditions including pH, oxidation potential and concentrations of phosphate, pyrrole (Py) and dopant ClO 4−on the PPy nanostructure is systematically investigated. A mechanism for the nanofiber formation in an aqueous solution without assistance of any “hard” and “soft” template is proposed, in which the presence of the hydrogen bonding between phosphate and Py oligomers is essential to producing the 1D nanofiber structure, and the electrostatic interactions between ion dopant and Py oligomers lead to an irregular nanostructure. This is a simple, environmentally friendly and one-step approach to fabricate a PPy film with unique nanostructure and chem-physical properties, which can have great potential in various applications such as sensors, electronics, and energy source systems. [ABSTRACT FROM AUTHOR]