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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.

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.

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.

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.

It is impossible to directly measure the photoelectron spectrum of an atom using conventional XPS due to its low detection sensitivity. In this work, an indirect method has been developed to determine the binding energy (BE) of an atom. In this method, the BE of the atom can be obtained by extrapolation of the experimental BE curves with atomic deposition coverage to zero coverage. With this method, the Ni 2p3/2 BE's of atomic Ni on TiO2(001) and (110) surfaces are deduced to be 853.69 and 853.55 eV, respectively. Compared with atomic Ni in gas phase, relaxation shifts of 7.34 and 7.48 eV are obtained on TiO2(001) and (110) surfaces, respectively. These values are very close to the relaxation shift of 7.3 eV due to d electron screening, indicating d-like screening effects from the TiO2 substrates after Ni 2p photoionization. This method is also used to determinate the Ni 2p3/2 BE's of atomic Ni on TiO2(001) with different surface stoichiometries. The difference of Ni 2p3/2 BE is due to different interfacial charge transfer. Copyright © 2010 John Wiley & Sons, Ltd.

Novel microelectrodes or microsensors may be based in future on the extraordinary single-crystalline, channel-structured β-AgVO3 compound (see image) created by a simple hydrothermal process. The synthesis and electron transport in these compounds are discussed. It is shown that, depending on the electric field, the transport mechanism changes, which in turn influences the electronic behavior. For Graphical Abstract please refer to this link: http://dx.doi.org/10.1002/smll.200700032

ZnO nanowire was tailored both physically and chemically to immobilize the enzyme glucose oxidase (GOD) for construction of a glucose sensor with high performance, which was ascribed to its high specific surface area and high isoelectric point value for efficient immobilization of high concentration of acidic enzymes and the mediating effect by the redox reaction of ZnO nanowires. The apparent Michaelis constants Jmax, and KM were adjusted in a large scope by tailoring the thickness of the GOD/ZnO nanowire layer and the enzyme load in the nanowired network. Thus, a variety of linear region, sensitivities and reaction rates of the sensor could be easily achieved. Moreover, the glucose sensor showed long term stability with the incorporation of the inorganic zinc oxide nanowire.

Consistent insight is presented into the atomistic origin and temperature (T) dependence of the redshift of Raman optical modes in nanostructures from the perspective of surface bond unsaturation and the bond-order-length-strength (BOLS) correlation [Sun et al., Phys Rev B 72, 134301 (2005)]. It turns out that: (1) the size-induced redshift of Raman optical modes results from the effect of bond order deficiency of atoms on the surface and its consequences on the force constants of bonds between the under-coordinated surface atoms; (2) the temperature-induced redshift arises from thermally induced bond expansion and bond weakening and (3) the magnitude of vibration of atoms in the surface or surrounding defects is always greater than the fully coordinated bulk atoms, while the frequency of such under-coordinated atoms are relatively lower. It is demonstrated that a combination of the freedoms of solid size and temperature of testing with Raman spectroscopy could lead to information about the vibrational frequency of a monatomic chain and single-bond energy, which is beyond the scope of the traditional size- and temperature-independent approaches. Copyright  2007 John Wiley & Sons, Ltd.

Polypyrrole was electrochemically synthesized onto a gold electrode in the presence of sodium p-toluenesulfonate (TSNa) as the key dopant. Under the optimal synthesis condition, the surface morphology of PPy/TSNa was tailored and exhibited a nano-tentacle structure. The resulting rough and fuzzy morphology greatly enhanced the apparent surface area as well as the polymer film conductivity. Adenosine triphosphate (ATP) was then incorporated in the structure by subsequent ion exchanging. This procedure could be envisaged as pseudo-molecular templating to eliminate several shortcomings associated with physical templating. Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy were conducted to investigate the incorporation of ATP. The pronounced rough surface of PPy/TSNa provided a higher density of active sites for ATP binding. The resulting PPy/ATP film exhibited a high charged capacity and lower impedance compared to the bare gold electrode. ATP remained stable in the PPy film; however, a negative bias to the electrode stimulated the conducting polymer to release ATP. This concept could serve as a mechanism for drug delivery and biosensing applications. (c) 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006.

Single walled carbon nanotubes (SWCNT) and room temperature ionic liquid (RTIL) were used to make a gel microelectrode for studies of the oxidation of nitric oxide (NO). The Faraday response of the gel microelectrode was contributed from two components: an outside-surface microdisk and a thin-layer cell formed by inner porous electrode materials, and enhanced by the thin-layer effect. An EC mechanism, electrochemical NO oxidation followed by a chemical oxidation, was proposed. The gel microelectrode with a Nafion coating eliminated interferences from nitrite and some biomolecules, improved stability, and had a linear response range from 100 nM to 100 μM. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.

An innovative method is presented to estimate the size effect on the ferroelectric phase transitions in the barium titanate ceramic system. The method is based on the phenomenological thermodynamic theory with additional stress led by surface bond contraction. Two symmetry-breaking factors are introduced to correct the stress. This method has enabled us to predict the changing trends in phase transitions and the critical grain size for the disappearance of ferroelectric phase, which is beyond the prediction of existing models.

Nanostructured photocatalysts have attracted considerable interest due to their wide range of applications in processes such as organic pollutant degradation, heavy metal reduction, air and water purification, hydrogen production, etc. Pursuing high catalytic efficiency is the foremost goal in the field. One of the current key issues is to search for suitable photocatalysts to enhance light harvesting in the UV or visible light region. In this treatise, the microwave-assisted solution-phase synthesis of various nanomaterials including semiconductor oxides and sulfides, Bi-based oxides, as well as nanocomposites including carbon nanotube-based and graphene-based composites is systematically presented with demonstrations of the advantages of the microwave-assisted process over traditional synthesis methods including solid state or vapor reactions and hydrothermal or solvothermal processes. Application of these nanomaterials as photocatalysts for the degradation of pollutants in water or air, removal of Cr(VI) as well as hydrogen evolution is also demonstrated, showing the improved photocatalytic activities compared with the ones synthesized via traditional methods.

This report deals with the mechanism behind the unusual behavior of nanostructures in mechanical strength, thermal stability, acoustics (lattice dynamics), photonics, electronics, magnetism, dielectrics, and chemical reactivity and its indication for designing and fabricating nanostructured materials with desired functions. A bond-order-length-strength (BOLS) correlation mechanism has been initiated and intensively verified, which has enabled the tunability of a variety of properties of a nanosolid to be universally reconciled to the effect of bond order deficiency of atoms at sites surrounding defects or near the surface edges of the nanosolid. The BOLS correlation indicates that atomic coordination imperfection causes the remaining bonds of the under-coordinated atom to contract spontaneously associated with bond strength gain and the intraatomic trapping potential well depression. Consequently, localized densification of charge, energy and mass occurs to the surface skin, which modify the atomic coherency (the product of bond number and the single bond energy), electroaffinity (separation between the vacuum level and the conduction band edge), work function, and the Hamiltonian of the nanosolid. Therefore, any detectable quantity can be functionalized depending on the atomic coherency, electroaffinity, work function, Hamiltonian or their combinations. For instances, the perturbed Hamiltonian determines the entire band structure such as the band-gap expansion, core-level shift, Stokes shift (electron-phonon interaction), and dielectric suppression (electron polarization); The modified atomic coherency dictates the thermodynamic process of the solid such as self-assembly growth, atomic vibration, phase transition, diffusitivity, sinterbility, chemical reactivity, and thermal stability. The joint effect of atomic coherency and energy density dictates the mechanical strength (surface stress, surface energy, Young's modulus), and compressibility (extensibility, or ductility) of a nanosolid. Most strikingly, a combination of the new freedom of size and the original BOLS correlation has allowed us to gain quantitative information about the single energy levels of an isolated atom and the vibration frequency of an isolated dimer, and the bonding identities in the metallic monatomic chains and in the carbon nanotubes. A survey and analysis of the theoretical and experimental observations available to date demonstrated that the under-coordinated atoms in the surface skin of 2-3 atomic layers dictate the performance of nanostructures yet atoms of the interior remain as they are in the bulk counterpart. Further extension of the BOLS correlation and the associated approaches to atomic defects, impurities, liquid surfaces, junction interfaces, and amorphous states and to the temperature domain would be more challenging, fascinating, and rewarding.

This report presents a systematic understanding of the nature behind the unusual behavior of a nanosolid, and a surface as well, in mechanics, thermodynamics, acoustics, optoelectronics, magnetism, dielectrics, atomic diffusivity and chemical reactivity towards predictable design and controllable growth of nanostructured materials. A bond order-length-strength (BOLS) correlation mechanism has been developed, which has enabled the tunability of a variety of properties of a nanosolid in connection with surface to be consistently predicted and experimentally verified. The BOLS correlation indicates that the coordination number (CN) imperfection of an atom at site surrounding a defect or in the surface skin causes the remaining bonds of the lower-coordinated atom to contract spontaneously. The spontaneous bond contraction is associated with bond-strength gain or atomic potential well deppression, which localize electrons and enhance the density of charge, mass, and energy in the relaxed region. The enhancement of energy density in the relaxed region perturbs the Hamiltonian and the associated properties such as the band-gap width, core-level energy, Stokes shift (electron-phonon interaction), and dielectric susceptibility. On the other hand, bond order loss lowers generally the cohesive energy of the lower-coordinated atom from the value of a fully-coordinated atom, which dictates the thermodynamic process such as self-assembly growth, atomic vibration, thermal stability, and activation energies for atomic dislocation and diffusion. Consistency between predictions and observations evidences the enormous impact of atomic CN imperfection and the validity and essentiality of the BOLS correlation., Comment: Review 120 pages, 635 refrences, and 49 figures (excluded in this submission)

Most partial altervalent/aliovalent substitutions for Mg or B in MgB2 studied to date depress the superconducting transition temperature (Tc) and, at higher replacements, completely suppress superconductivity of MgB2. The diminution and loss of superconductivity in MgB2 arise from the subtle interplay between the competing/cooperating effects of the electronic and lattice structural variations, which are induced by the different charge and atomic radii of the substituents. Here, we experimentally discriminate lattice structural effects from electronic contributions to superconductivity by exploiting the nanosize dependence of the lattice structure to modify structural parameters without resorting to chemical doping. It is found that the superconductivity of MgB2 is extremely sensitive to lattice parameter variation, such that contraction of Mg−Mg bond dramatically depresses Tc and eventually results in the loss of superconductivity as the average coordination of Mg to B falls from 12 to 8 due to the introduction of B vacancies for nanocrystalline MgB2 of 2.5 nm diameter.

This report features the recent progress in understanding the behaviour of atoms and valence electrons involved in the process of oxidation, and some technological development driven by the new knowledge. It is initiated and verified that a chemical bond contracts spontaneously at a surface associated with magnitude rise of the bond energy due to the coordination imperfection and that an oxygen atom hybridizes its sp orbitals upon reacting with a solid surface. The former leads to the bond order–length–strength (BOLS) correlation for the physical aspect of a surface and a nano-solid and the latter to a bond–band–barrier (BBB) correlation for chemical reaction. In the process of oxidation, non-bonding lone pairs, anti-bonding dipoles and hydrogen-like bonds are involved, which add corresponding density-of-states (DOS) features to the valence band of the host. Bond forming also alters the sizes and valencies of the involved atoms and causes a collective dislocation of these atoms, which corrugate the morphology or the potential barrier of the surface. Based on the above premises, the oxidation of the low-index surfaces of transition metals Cu, Co, Ag and V, noble metals Rh, Ru, and Pd and non-metallic diamond has been consistently analyzed. Identities probed with various techniques, such as STM, LEED, XRD, STS, PES, TDS, EELS and Raman, have been systematically defined in terms of atomic valencies, bond geometry, valence DOS, bond strength and bond forming kinetics. It is understood that formation of the basic oxide tetrahedron, and consequently, the four discrete stages of bond forming kinetics and the oxygen-derived DOS features, are intrinsically common for all the analyzed systems though the patterns of observations may vary from situation to situation. What differs one oxide surface from another in observations are: (i) the site selectivity of the oxygen adsorbate, (ii) the order of the ionic bond formation and, (iii) the orientation of the tetrahedron at the host surfaces. The valencies of oxygen, the scale and geometrical orientation of the host lattice and the electronegativity of the host elements determine these specific differences extrinsically. Extending the premise of sp-orbital hybridization to the reactions of (C, N)–Ni(001) surfaces has led to a novel approach neutralizing the diamond–metal interfacial stress and hence strengthening the diamond–metal adhesion substantially. The BOLS correlation has provided consistent insight into the shape-and-size dependence of a number of properties for nano-solids. The BBB correlation has led to new findings in designing and fabricating materials for photoluminescence, electron emission and ultrahigh elasticity, etc.

Understanding the blue shift in the photoluminescence (PL) of the nanosolid near the lower end of the size limit (D < 5 nm) seems difficult with the currently available models. This challenges are ...