A simple chemical kinetic model is developed which describes the behavior of small ligands that can bind reversibly with large carrier molecules with slower intrinsic rates of transport. Under certain conditions, which we describe, the presence of the slower carriers in fact enhances the transport of the ligand. This is the chemical version of Wyman-Murray's facilitated diffusion. The simple model illuminates the driven nature of the enhancement of the transport by the carrier molecules: we show that the facilitated transport depends crucially on a“grand canonical” setting in which the free ligand concentrations are kept constant in the presence of the facilitating protein, in contrast to a canonical setting with constant total ligand concentrations. Results from the simple model are compared to previous experimental and theoretical results for Wyman-Murray facilitated diffusion of oxygen and carbon monoxide in muscle. A relation is established between the association-dissociation rates and the down-stream ligand concentration, or back pressure for oxygen, required for the facilitation effect to occur.

The coupling and synergistic effects of the unique structure of multi-level, multi-dimension, and multi- components allow for the directed synthesis of hierarchical nanostructures and this field has attracted much interest recently. In this paper, we discuss progress in the solution synthesis of three kinds of hierarchical structures including core-shell, segmented, and branched structures. We focus on the formation mechanism and the influencing factors of the hierarchical structures by considering the crystal nucleation-growth process and growth kinetics. The construction of the hierarchical nanocomposites mainly involves the heterogeneous nucleation-growth of the secondary structures on the primary structures or a component exchange between the two kinds of materials. The degree of lattice matching, the degree of supersaturation, and chemical bonding mainly influence the hetero-nucleation sites of the secondary structures on the primary structures. The growth behaviors of the secondary structures can be modulated mainly by adjusting their crystallographic energy through surface modifications. For the synthesis via component exchange, an important prerequisite is that the primary and secondary structures share the same anions or cations.

Experimental methods, theoretical calculations as well as computer simulations are the three most often used approaches to investigate the microscopic properties and interactions of ionic liquids (ILs). The relationship between the structure and properties of ILs, which is the foundation for designing new functional ionic liquids and promoting their applications in cleaner production, are not thoroughly understood. Recently, spectroscopic methods have been developed to study the structures of solutions. Among the various spectroscopic methods, infrared spectroscopy and Raman spectroscopy play important roles in investigations on the structural properties and interactions of ionic liquids. We thus review the applications and progress of these two spectroscopic methods on structural and property studies of pure ionic liquids and ionic liquids/solvent mixtures. Additionally, we address the associated challenges and prospects.

We investigated the adsorption of diclofenac (an anti-inflammatory drug) in aqueous solutions by magnetic multiwalled carbon nanotubes (MWCNTs). The results showed that the amount of adsorbed diclofenac initially increased with magnetic MWCNT dosage and stabilized at a magnetic MWCNT dosage of 0.7 g·L^-1. The amount of diclofenac adsorbed by the magnetic MWCNTs was 33.37 mg·g^-1 and the removal rate of diclofenac was 98.1%. The removal rate for the diclofenac increased and then decreased with the pH value of solution, but it decreased with the temperature of solution. Kinetic analysis was conducted using pseudo first and second order models. Regression results showed that the adsorption kinetics was more accurately represented by a pseudo second order model. The linear correlation coefficients and standard deviations of the Langmuir and Freundlich isotherms were determined and the results revealed that the Langmuir isothermfit the experimental results well. The calculated thermodynamic parameters were: ΔG⁰<0 indicating that the adsorption of diclofenac on magnetic MWCNTs was spontaneous, ΔH⁰<0 indicating that the absorption reaction was exothermic and that low temperatures are favorable for adsorption, and ΔS⁰>0 indicating that the adsorption process was a entropy enhancing process.

We studied the effects of reaction pressure, molar ratios of air to methane and steam to methane on the reforming process at temperatures below 973 K theoretically. Their reasonable ranges were also studied. We also compared the performance of a methane autothermal reforming system and a non-oxygen system. Results show that methane autothermal reforming occurs much more easily at temperatures above 633 K, reaction pressures below 0.10 MPa, a molar ratio of air to methane of 2.0, and a molar ratio of steam to methane between 1.0 and 2.5. At a definite methane mass flow, a higher methane conversion rate and hydrogen yield can be obtained at lower temperatures and in lesser steam to methane ratio in an autothermal reforming systemcompared with a non-oxygen system.

Polyacrylamide (PAM) applied to various fields is an important class of linear water-soluble polymers. Therefore, it is of great significance to study the solution properties of PAM. We constructed solution models containing different amounts of water molecules with a mass concentration of about 1 g·mL^-1. Using molecular dynamics (MD) simulations we calculated the radius of gyration (R_g) for non-ionic PAM (PAM-H) and anionic PAM (HPAM) in pure water and in aqueous solutions with different mass fractions of NaCl. We discussed their behaviors at different temperatures. We found that the salt tolerance of the polyacrylamides fromthe simulation agreed with the experimental results at different temperatures. Furthermore, the simulation results for all the solution models containing a different amount of water molecules basically showed a similar trend. Considering computational efficiency, the solution model containing 2000 water molecules was selected for our study. The radial distribution functions (RDF) for the oxygen ions and oxygen atoms of the HPAMchain were investigated in NaCl solution model containing 2000 water molecules. The reduced viscosity of HPAM solutions with increasing NaCl mass fractions and a better thickening ability as well as poor salt tolerance compared to PAM-H were explained considering their microstructures as determined by RDF.

The thermal decomposition kinetics of the novel terpolymer, poly(propylene carbonate maleate) (PPCMA), was investigated using thermogravimetric (TG) analysis at different heating rates. A new computational method called nonlinear approximation (NLA) is introduced in this work. The Flynn-Wall-Ozawa (FWO), Tang, Kissinger-Akahira- Sunose (KAS), and NLA methods were used to calculate the apparent activation energy (Ea). The results show that the NLA method is ideal for Ea calculations because of its simpler and more appropriate analysis process. It does, however, give slightly higher average relative errors for Ea compared to the other typical model-free methods. Calculations using the solid-state reaction model-fitting method indicated that the thermal decomposition process was composed of multiple mechanisms. For the whole decomposition process, the values of Ea were between 70 and 135 kJ·mol^-1, and the pre-exponential factor (A) varied from5.24×10⁴ to 9.89×10⁷ min^-1. The differences in Ea also explain the differences in decomposition temperature between poly(propylene carbonate) (PPC) and PPCMA.

To overcome the disadvantages of chronoamperometry we report a novel electrochemical method where a peak current is quickly generated for the current vs time curve by changing the waveform of voltage excitation in the working electrode. In particular, we derived a mathematical model to illustrate the principle of this method and it can also be used to demonstrate that the peak current is linear with regards to the concentration of the target substance. Moreover, we developed a device with an improved electrochemical circuit using a control element from control theory to change the waveform of voltage excitation. The improved circuit can detect the peak automatically without a precise sample time. Finally, the device was used to study the electrochemical behavior of K₃[Fe(CN)₆] and 3,3',5,5'- tetramethylbenzidine (TMB). We show that the method has a better signal to noise ratio and higher sensitivity than chronoamperometry. The obtained peak current is linear with regards to the concentration of the target substance and can be quickly detected without a precise sample time.

We sensitized CdS quantum dots on a ZnO nanorod array electrode by the successive ionic layer adsorption and reaction method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) experiments were performed to characterize the morphology, crystalline phase, and grain size of the CdS quantum dot sensitized ZnO nanorod array electrodes. The effect of CdS deposition cycle number and the precursor concentration were studied by photocurrent-potential characteristics and photocurrent spectra. The results showed that the best photoelectrochemical performance was obtained at 0.1 mol·L^-1 for both Cd²⁺ and S^2- after 15 cycles. Meanwhile, the composite films exhibited a remarkably enhanced photoelectric conversion efficiency compared with the ZnO nanorods array films and with CdS quantum dot electrodes. The monochromatic incident photon-to- electron conversion efficiency (IPCE) was as high as 76% at 380 nm. This may be attributed to the broad light harvesting capability of CdS and the efficient separation of photogenerated carriers on its interface. The reason for this enhancement was further confirmed by a photoluminescent experiment. The results showed that sensitization with CdS quantumdots reduced the recombination of electron and hole pairs resulting in an enhancement in the photocurrent.

The 2μm and 650 nm TiO₂ nanotube (TNT) arrays were fabricated by sonoelectrochemical anodic oxidation in ethylene glycol (TNT-E) and in aqueous solution (TNT-A) electrolytes at 20 V direct voltage. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were used to characterize the crystal phase and surface morphology of the resulting oxide films. UV-Vis diffuse reflectance spectra (UV-Vis DRS), current-time (I-t) curves, Mott-Schottky plots and electrochemical impedance spectroscopy (EIS) were used to investigate their kinetics properties and their electrochemical impedance behavior. The 2 μm nanotubes of TNT-E can help to harvest more light and provide more surface active sites than the 650 nm nanotubes of TNT-A. We found that TNT-E had stronger light absorption than TNT-A after calcination in air at 500 ℃, but the photocurrent density differences between TNT-E and TNT-A was only about 0.05 mA·cm² under UV illumination ((365±15) nm). Since the longer TNT-E tubes can increase the charge transport resistance and decrease the concentration of the reactants on the electrode surface, TNT-E needs to overcome a larger energy barrier and it has a low charge carrier density of 5.31×10²⁰cm^-3. TNT-A with relatively shorter tubes showed a better kinetics property and had a charge carrier density of 9.86×10²⁰ cm^-3.

We investigated the corrosion of steel under defective coatings in 3.5% (mass fraction) NaCl solution by the wire beamelectrode (WBE) and electrochemical impedance spectroscopy (EIS) technique. During the entire coating deterioration process, the EIS diagrams were dominated by the substrate corrosion process of the defect while the coatings and underlying electrochemical processes were“averaged”out. However, according to the current distribution maps plotted using the WBE, EIS responses of the anodic and cathodic regions of the defect and underlying coatings were detected. Initially, the high anodic and cathodic current densities were only monitored at the defect areas and then the cathodic sites spread out beneath the coatings around t2948he defect while the anodic sites remained on the defect. The substrate corrosion initiation and development mechanism of the defect and underlying coatings is discussed based on experimental results.

A polypyrrole(PPy)/9,10-anthraquinone-2-sulfonic acid sodium salt (AQS) composite electrode was prepared by constant-potential electropolymerization using AQS as a counter-ion. Cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) were used to evaluate its capacitance performance. Experimental results show that the AQS dopant results in an improved specific capacitance, increased long-cycle stability, and a wide working potential range compared to that of using ClO^-₄ as the dopant. The PPy/AQS composite electrode has a specific capacitance of 491 F·g^-1 at a CV scan rate of 50 mV·s^-1 within a potential range of -0.6 to 0.6 V in 1 mol·L^-1 KCl, which is 1.5 times more than that with a PPy/ClO^-₄ composite electrode. The improvement in capacitance should be attributed to the od redox performance of AQS and the porous submicron/ nanosized structure of the resulting composite film.

APt/FTOelectrode for dye-sensitized solar cells (DSSC) was prepared by the sputtering (Cu) -displacement (Pt) (SD) method on a conductive glass (FTO) substrate (SD-Pt/FTO). Morphological characterization revealed that the dispersion of Pt particles on the SD-Pt/FTO electrode was significantly improved in comparison with the PY-Pt/FTO electrode prepared by the pyrolysis of Pt salts (PY). Optical current-voltage curves showed that the photoelectric conversion efficiency of DSSC with a SD-Pt/FTO counter electrode increased by 16.5% relative to that with a PY-Pt/ FTO counter electrode. The improvement of DSSC performance with the SD-Pt/FTO electrode is due to its lower electric resistance, and od catalysis resulting from the improved dispersion of Pt particles in the SD process compared with the PY process.

One problem that limits the rate capabilities of lithium-ion batteries is that despite the small size of the nanocrystalline particles in the electrode material, the crystalline structure might collapse during repetitive Li⁺ intercalation and extraction leading to the deterioration of charge and discharge performance under high currents. The prevention of this destruction has been attempted by substituting constituent atoms with other atoms to stabilize the structure in various transition metal oxide systems. In this work, H₂Ti₂O₅·H₂O/Cr₂O₃ compounds with nanotubes morphology were prepared by low temperature alkali-hydrothermal processing from anatase-type TiO₂ with the addition of 5% (w) Cr₂O₃. The crystal structure and morphology of the as-prepared H₂Ti₂O₅·H₂O/Cr₂O₃ nanotubes were investigated by X-ray diffraction and transmission electron microscopy, respectively. Electrochemical lithium insertion cycling tests showed excellent cycling stability and an improved rate capability. The capacity of the first cycle was 288 mAh·g^-1, and over 145 mAh·g^-1 capacity remained after 120 cycles at 150 mA·g^-1. At a current of 1500 mA·g^-1, the capacity of the first cycle was 178 mAh·g^-1. Over 80 mAh·g^-1 capacity remained after 600 cycles at 1500 mA·g^-1; furthermore, the capacity could come back to 150 mAh·g^-1 at 150 mA·g^-1 after 600 cycles at 1500 mA·g^-1, which was close to the result for the cell that was immediately discharged/charged at 150 mA·g^-1. The Cr₂O₃ particles, as the second phase, can improve the structural stability and high-rate capability of the H₂Ti₂O₅·H₂O nanotubes. These novel one-dimensional nanostructured materials may find promising applications in lithium-ion batteries and in electrochemical cells.

Novel sulfonated poly(ether sulfone) (SPES)/phosphotungstic acid (PWA)/silica organic-inorganic composite membranes for application in direct methanol fuel cells (DMFCs) were prepared by doping SiO₂ sol and PWA into SPES matrix. The structure and performance of the obtained membranes were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), etc. Compared with the pure SPES membrane, SiO₂ and PWA doping led to higher thermal stabilities, a higher glass transition temperature (T_g), and higher water uptake. At 20℃ and a fuel cell operating temperature of 80℃, the tensile strength of all the composite membranes was lower than that of the SPES membrane. However, even when the content of SiO₂ was as high as 20% (w), the composite membrane still possessed a higher strength than a Nafion 112 membrane. The morphology of the composite membranes indicated that SiO₂ and PWA were uniformly distributed throughout the SPES matrix, which may facilitate proton transport. The proton conductivity of the composite membrane (SPES-P-S 15%: 15% (w) SiO₂ and 6% (w) PWA) reached 0.034 S·cm^-1, which was similar to that of the Nafion 112 membrane at room temperature. However, methanol permeation through the SPES-P-S 15% composite membrane decreased dramatically and was only one-seventh that of the Nafion 112 membrane. This excellent selectivity of the SPES/PWA/SiO₂ composite membrane points to its potential use as a promising electrolyte for DMFCs.

The stability of alkaline electrolyte membranes is recognized as a key factor that affects their electrochemical applications, especially, in alkaline medium at temperatures above 60℃ and high KOH concentration. In this article, poly(vinyl alcohol)/poly(vinyl pyrrolidone)/KOH (PVA/PVP/KOH) alkaline membranes were succesfully prepared by direct blending and chemical cross-linking modifications. In particular, the molecular structure, thermal stability, chemical stability, oxidative stability, and mechanical strength stability of the composite membranes were studied in detail using fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and alternating current impedance technique. FTIR results indicated that PVP was successfully incorporated into the PVA matrix due to the strong PVP C=O I peak centered at 1672 cm^-1. From the TGA, the increasing concentration of the doped KOH into membranes has little effect on the thermal stability. The homogeneous and compact morphology of the cross-section of the membranes were observed by SEM after conditioned at elevated temperatures and high concentration of KOH(80℃, 10 mol·L^-1). The conductivity of the membrans (1.58×10^-3 S·cm^-1) in 10 mol·L^-1 KOH at 80℃ was 91.5% higher than that in 10 mol·L^-1 KOH at room temperature, which demonstrated the perfect chemical stability of the PVA/PVP alkaline membranes. In addition, the membranes displayed very high oxidative durability. Still 89% and 85% mass of the membrane were retained after 150 h treatment in 3% and 10% H₂O₂ solution at 60℃, respectively. Due to the high dense cross-linkages in polymer matrics, the PVA/PVP/KOH membranes showed od isotropy and conductivity stability in pure water during the measuring time lasted for more than 800 h.

The effect of hydrophobically modified polyacrylamide (HMPAM) on the dilational rheological properties of interfacial films containing acidic components or asphaltenes in petroleum crude oil was investigated by drop shape analysis method. The influence of surface-active component concentration on the dilational rheological behavior was investigated. Experimental results show that the dilational modulus is approximately 100 mN·m^-1 for a 1750 mg·L^-1 HMPAMsolution. This is due to the formation of an interfacial structure by a hydrophobic interaction among HMPAM molecules. As the interfacial film ages, the acidic component molecules adsorb onto the interface and form mixed complexes with the hydrophobic parts of the HMPAMmolecules. These interactions reduce the dilational modulus by a fast exchange process and the elasticity of the structure improves because of an enhanced hydrophobic interaction among the HMPAMmolecules. For asphaltenes, the nature of the interfacial film is controlled by both the structure of HMPAMand the interfacial complex formed by pure asphaltene molecules because of their relatively larger molecular sizes as well as their strong intermolecular interactions, which leads to a slight decrease in the dilational modulus compared with the pure HMPAMsystem.

The interface free energy of a local condensate from the growth and combination of numerous initial condensation nuclei was calculated during its shape changes from an early flat shape to a Wenzel or Cassie state on the super-hydrophobic surface (SHS). The final state of the condensed drop was determined according to whether the interface free energy continuously decreased or it had a minimum value. Our calculations indicate that condensation drops on a surface only with micro roughness display Wenzel state because the interface free energy curve of a condensed drop first decreases and then increases, existing a minimum value corresponding to Wenzel drop. On a surface with appropriate hierarchical roughness, however, the interface energy curve of a condensed drop will constantly decline until it reaches the Cassie state. Therefore, a condensed drop on a hierarchical roughness surface can spontaneously reach the Cassie state. In addition, the states and apparent contact angles of condensed drops on a SHS with different structural parameters were calculated and compared with experimental observations. Results show that the calculated condensed drop states agree well with the experimental results. It can be concluded that micro and nano hierarchical roughness is the key structural factor responsible for sustaining condensed drops in the Cassie state on a SHS.

Interactions between a series of N-alkyl-N,N-di(2-hydroxyethyl)-N-methylammonium bromides with alkyl chain from dodecyl to cetyl and bovine serum albumin (BSA) in Tris-HCl buffer solution (pH=7.1) were studied by fluorescence spectroscopy at 298 K. Effects of the surfactant structure and BSA concentration on the interactions were examined. The interaction mechanism between BSA and surfactants at a relatively low concentration range was discussed using the Stern-Volmer equation and a model of the pseudo association constant. Each of the quaternary ammonium surfactants has a fluorescence quenching effect on BSA and leads to a blue shift of the maximum emission wavelength. The Stern-Volmer quenching constant and the pseudo association constant increase, which indicates that the interactions between surfactants and BSA become stronger, as the hydrophobic chain lengths increase.

Platinum nanoparticles supported by graphene were prepared by the colloid deposition process. The effects of particle size and loading amount of platinum particles on the cataluminescence (CTL) properties of CO have been investigated. The CTL properties and some analysis characteristics of the catalyst on other gas phase systems were explored. The results show that the Pt nanoparticles are well distributed on graphene and a faster catalytic reaction rate is apparent. The smaller particles lead to a higher CTL intensity. When the volume concentration of CO in air is below 40% (φ, volume fraction) the CTL intensity is proportional to the concentration of CO for all the catalysts (0.4%-1.6% (w, mass fraction) Pt). Among them, the catalyst containing 0.8% Pt was found to be the best. However, by increasing the CO concentration the CTL intensity of the catalysts with a low Pt loading (0.4%, 0.8%) decreased while the highly loaded (1.2%, 1.6%) catalysts continued to increase their intensity. Moreover, a higher Pt loading led to a higher CTL intensity. Under certain conditions the catalyst shows od CTL performance for CO oxidation, and ether, methanol as well as toluene show different degrees of response. No response was obtained for carbon dioxide, formaldehyde, glutaraldehyde, acetone, ethyl acetate, chloroform, and water vapor.

The low-temperature selective catalytic reduction of NO with NH₃ (NH₃-SCR) over MnO_x-CeO_x/ACF (activated carbon fiber) modified by Fe, Cu, or V was investigated in the presence of SO₂. The results revealed that the SO₂ tolerance of MnO_x-CeO_x/ACF was not enhanced after Cu and V modification. The addition of Fe to MnO_x-CeO_x/ ACF enhanced its resistance to SO₂ poisoning over the first 6 h in the presence of SO₂, but then deactivated quickly. The samples were analyzed by N₂ adsorption, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT- IR) spectroscopy, and thermogravimetric analysis (TGA).We found that catalyst surface coverage by ammoniumsalts as well asmetallic sulfates and sulfites formed by the reaction between SO₂ and metal oxides in the catalysts was responsible for catalyst deactivation in the presence of SO₂. Sulfur on the surface of the deactivated catalysts was mainly in the form of metallic sulfates and sulfites with 70.4%, 68.9%, 86.3%, and 71.4%(w) on deactivated MnO_x-CeO_x/ACF, Fe- MnO_x-CeO_x/ACF, Cu-MnO_x-CeO_x/ACF, and V-MnO_x-CeO_x/ACF, respectively. A valuable contribution towards understanding the deactivation of catalysts based on MnO_x-CeO_x/ACF for the SCR in the presence of SO₂ was made.

The nature of carbon deposition on a toluene disproportionation and transalkylation catalyst was characterized using thermogravimetry and differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, N₂ adsorption/desorption and NH3-temperature programmed desorption (NH₃-TPD). Result showed that the kinetics of hard coke combustion approximately fitted a first order reaction with respect to the amount of coke and, therefore, most of the coke existed in a monolayer state and the corresponding apparent activation energy was about 110 kJ·mol^-1. There were three kinds of carbon species on the surface of the Cat-1000 catalyst, which presented the catalyst after 1000 h reaction. The C atom fractions in the presence of C—O, C=O, and —C—C— were 22.7%, 9.1%, 68.1%, respectively. The formed carbon species on the Cat-1000 catalyst surface was mostly a graphite structure. The results showed that three quarters of the total carbon deposition on Cat-1000 was hard coke and the rest was soft coke. The specific surface area of the Cat-1000 catalyst decreased obviously compared with the catalyst without reaction (Cat-0). The Cat-1000 had almost unchanged acid intensity as well as high activity and stability. This shows that the cokes mainly deposit on the binder.

Novel CO₂ adsorbents for CO₂ removal were prepared by introducing tetraethylenepentamine (TEPA) into SBA-16 type mesoporous silica using a post-synthetic impregnation method. The properties of the mesoporous materials before and after surface modification were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and N₂ adsorption-desorption. We confirmed that TEPA was loaded onto the surface of the channels in the mesoporous materials. The surface area, pore size, and pore volume of TEPA-loaded SBA-16 decreased with an increase in TEPA loading while its fundamental pore structure was unchanged. The dynamic adsorption of CO₂ onto TEPA-loaded SBA-16 as well as its regeneration property was studied in a packed column. The total adsorption capacity and breakthrough capacity increased when the amount of loaded TEPA increased from 10% to 30% (w). The sample impregnated with 30% TEPA showed the highest breakthrough capacity and total adsorption capacity of about 0.625 and 0.973 mmol·g^-1 at 60℃, respectively. From 60℃ to 80℃, the CO₂ dynamic adsorption behavior of TEPA-loaded SBA-16 was stable. The total adsorption capacity of CO₂ on TEPA-loaded SBA-16 dropped slightly (6.45%) after 20 adsorption-desorption regeneration cycles. Their CO₂ adsorption behavior was also investigated using the deactivation model, which showed an excellent predictive capability for the breakthrough curves.

X-ray photoelectron spectroscopy (XPS) was used to record the Si 2p and valence band spectra for a series of ultrathin SiO₂ on Si substrate with the oxide thickness (d) ranging from 1.45 to 7.2 nm. The thicknesses of these samples were measured precisely in the international key comparison. The results show that the samples with the oxide thickness of d<2 nm have a lower Si 2p binding energy (EB ). This has been attributed to the extra-atomic relaxation provided by both the polarization of the neighboring atoms of SiO₂ and charge transfer from atoms of the Si substrate to the core holes created by photoionization (the screening distance was about (2.5±0.6) nm). The EB of Si 2p increased when d>3 nm and in this case extra-atomic screening was provided by the polarization of the neighboring atoms of SiO₂. The sample with a smaller d showed a higher EB for Si 2p. The valence band structure is also related to the thickness nanosize effect. The samples with d<2 nm show a higher relative peak intensity of the O 2p non-bonding electrons and lower peak intensities for the O 2p—Si 3p and O 2p—Si 3s bonding electrons from SiO₂.

In the reaction center of photosystem I the accessory electron transfer cofactors are two monomeric chlorophyll-a molecules that are ligated to two water molecules. To study the effect of water ligation on the redox potential and vibrational properties of chlorophyll-a, we built three molecular models of water ligation of chlorophyll-a based on the X-ray crystal structure of photosystem I. Then, we systematically calculated the geometries, vibrational frequencies, bond dissociation energies, and redox potentials of these models using density functional theory. The calculations were conducted in the gas phase, water, and a simulated protein environment. In addition, three different basis sets were employed to investigate the influence of the basis set on the calculation results. ¹⁵N, ²H, and ¹³C labeled spectra of the models in the gas phase were also calculated. Our results show that the water ligand causes the Mg ion of chlorophyll-a to move away fromthe center of the porphyrin ring so that the Mg—N bond lengths increase and the Mg centered angles decrease. When a nearby amino acid, asparagine (ASNB591), provides a hydrogen bond to the water that is axial ligand to the chlorophyll-a, these changes increase further. Additionally, the Mg—O bond distance decreases, the dissociation energy increases, and the redox potential also decreases. Furthermore, the redox potentials of the molecules and their bond dissociation energies decrease as the relative dielectric constant of the media and the basis sets increase. However, differences in the frequencies of the corresponding carbonyl groups and the C=C vibrations of the porphyrin ring in the three models are less than 7 cm^-1, and the differences in frequency shift upon isotope labeling between the models are less than 3 cm^-1. These results provide useful information for further studies of the structural and functional properties of chlorophyll-a in the photosynthetic reaction center.

The corrosion inhibition mechanism of four 1-R1-2-undecyl-imidazoline inhibitors (R1: CH₂COOH (A), CH₂CH₂OH (B), CH₂CH₂NH₂ (C), H (D)) for carbon steel against carbon dioxide corrosion was investigated by molecular dynamics simulation, from the aspect of corrosive medium particle (H₂O, H₃O⁺, and HCO^-₃) diffusion to the metal surface hindered by the corrosion inhibitor membrane. The corrosion inhibition performance of these compounds was also evaluated by the theoretical method. The diffusion coefficients in various corrosion inhibitor membranes, the interaction energies between particles and membranes, and the self-diffusion performance of the membranes indicated that the four imidazoline inhibitors could form stable membranes, which could effectively limited the diffusion of corrosive medium particles to the metal surface, in order to inhibit or delay corrosion. With an increase in the polarity of the hydrophilic chain (R1), the ability of the membrane to hinder particle diffusion enhanced. The membrane was better at limiting the diffusion of charged particles (H₃O⁺ and HCO^-₃) than that of a neutral particle (H₂O). Based on the above analysis, we found that theoretically the corrosion inhibition performance of the four imidazoline inhibitors decreased as follows: A>B>C>D, which agrees with previous experimental results.

The adsorption behavior of NOonto a Cu₃Pt (111) surface was studied using a periodic slab model and the PW91 generalized gradient approximation (GGA) within the framework of density functional theory. The calculated results indicated that NO adsorption with N-down on the top-Pt, hcp1, and fcc2 sites resulted in favorable structures with predicted adsorption energies of 101.8, 124.5, and 118.1 kJ·mol^-1, respectively. For adsorption onto the hcp1 and fcc2 sites, N atom from NO formed bonds with Cu₂Pt and Cu₃ clusters, respectively. An analysis of the density of states, charge population, and vibrational frequencies before and after the adsorption showed that electrons transferred from the surface of the alloy to NO and that the N—O bond was elongated and its vibrational frequency was red- shifted. The Cu₃Pt alloy and pure precious metal Pt have similar adsorption properties to NO.

We used density functional theory based on the pseudo-potential plane wave basis set to investigate the electronic structure of the β-LiAsSe₂ crystal with a non-centrosymmetric structure and the optical properties. Our results indicate that for the linear optical properties the birefringence of LiAsSe₂ is very large (>0.5) in the infrared region. The adsorption ability and photoelectric conversion efficiency of long wavelength sunlight for LiAsSe₂ were found to be superior to those of CuInSe₂. Regarding the nonlinear optical (NLO) characteristics, LiAsSe₂ showed a very large NLO second harmonic generation (SHG) response in the infrared region and the SHG coefficient (d₃₃) of LiAsSe₂ is about 836.5 pm·V^-1. However, poor transmission of light in the infrared region is predicted for LiAsSe₂ compared to AgGaSe₂. By an analysis of the band structure, the SHG response of the system could be attributed to transitions from valence bands that were mixed with contributions from Li to the unoccupied bands near the bottom of the conduction bands.

Density functional theory (DFT) was employed to investigate the geometric and electronic properties of a series of hexanuclear binary Ta/Rh clusters. The results show that most of the stable structures of the Ta/Rh mixed clusters have low symmetry and belong to the C₁ or C_s point groups while the [Ta₂Rh₄Cl₄H₈(CN)₆]^4- clusters are highly symmetric (C_2h or C_4v). The energy gaps (△E_H-L) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the mixed clusters are narrow and within 0.52-1.00 eV. A frontier orbital analysis of the mixed clusters clearly shows that the molecular orbitals are mainly composed of the d-orbitals of the skeleton metal atoms. When more rhodium atoms are substituted for tantalum atoms, the Ta—Rh bond has a greater influence on the stable structures of the mixed clusters and the influence of Ta—Ta bond decreases while the Rh—Rh bond has a non-bonding or anti-bonding nature.

The effects of CH₃OH and NH₃ on the hydrolytic deamination mechanism of adenine were studied by density functional theory at the B3LYP/6-311G(d,p) level. The results reveal that a tetrahedral intermediate is formed after a nucleophilic attack by a water molecule. Two intermediates are formed through conformational changes and different pathways are responsible. In pathway a, an assistant molecule takes part in the formation of the transition state and acts as a bridge to transfer a hydrogen atom, while in pathway b the assistant molecule is not involved in the creation of the transition state and acts only as a medium. The adenine takes place an amine-imine tautomerization before the nucleophilic attack under NH₃, which is not the case for the methanol-assisted mechanism. Energy results indicate that the energy barrier of the methanol-assisted adenine deamination is similar to that of the water-assisted reaction while the ammonia-assisted reaction has amuch higher energy barrier compared with the water-assisted reaction.

Hetarylazo chromophores were incorporated into fluorinated polyimide matrices to prepare novel nonlinear optical (NLO) side-chain fluorinated polyimides by the Mitsunobu reaction. Their structures were verified by Fourier transform infrared (FT-IR) spectra, UV-visible (UV-Vis) spectra, ¹H nuclear magnetic resonance (¹H NMR) spectra, and gel permeation chromatography (GPC). Thermal analysis results indicate that the side-chain polyimides have high glass transition temperatures (T_g) between 184 and 188℃ and thermal decomposition temperatures (T_d) up to 322℃. The electro-optic coefficients (γ33) of the side-chain polyimides were measured by a simple reflection technique at 1550 nm. The fluorinated polyimide PI1 containing a benzothiazolylazoaniline chromophore possesses a high electro-optic coefficient of 15 pm·V^-1.

We conveniently removed the Ni-M catalyst components from an as-grown multiwalled carbon nanotube (CNT) using an aqueous HNO₃ solution with strong acidity and oxidizability as a purifying reagent. Some oxygen-containing surface groups were generated at the CNT surface, which converted the hydrophobic surface into a hydrophilic surface. The phase composition and the oxygen-containing surface groups of the CNTs treated by nitric acid were determined and characterized using Boehm's neutralizing titration method and X-ray powder diffraction (XRD), temperature-programmed desorption (TPD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) techniques. The results indicated that the total content of the formed oxygen-containing surface groups was the highest for the CNTs treated with 7.0 mol·L^-1 aqueous HNO₃ at 378 K for 24 h. The content of the three major oxygen-containing surface groups was: carboxyl>lactonic carboxyl>phenolic hydroxyl.

We synthesized a one dimensional (1D) TiO₂ nanowire with a large aspect ratio on non-Ti substrate in NaOH aqueous solution by the hydrothermal treatment of pure titanium films deposited by direct current magnetron sputtering on a flexible stainless steel substrate (50 μm). The samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoelectro- chemical methods. Results show that the density and crystallinity of the titanium film as well as the binding strength between the Ti film and the stainless steel substrate increased with an increase in substrate temperature. The optimum hydrothermal temperature for the formation of the 1D TiO₂ nanowire was 130-150 ℃when the concentration of NaOH was kept at 10 mol·L^-1. TiO₂ nanowires with diameters of 10-30 nm and lengths of up to several microns grow in a crosswise manner and form a 3D network structure. Moreover, linear sweep voltammetry and transient photocurrent response curves indicated that the 1D TiO₂ nanowire film electrode had better photoelectrochemical performance than the TiO₂ nanoparticle electrode. This technique provides a new method for the fabrication of 1D TiO₂ nanowire films on different non-Ti heterogeneous substrates.

Silver tangled nanowires and dendritic structures were readily synthesized in high yield by reducing silver nitrate with different concentrations of ascorbic acid in a polyacrylamide (PAM) aqueous solution at mild conditions (normal temperature and pressure). The structures obtained all have tangled morphology, which is different from the silver nanowires reported previously. The structures of the obtained sliver structures were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and UV-Vis spectroscopy. PAM plays a key role in the formation of these anisotropic nanostructures as the capping agent and as a soft template. During the initial stage, silver nuclei are formed and PAM molecules simultaneously adsorb on their surfaces. Then, small silver particles will collide with each other along the polymer chains leading to the formation of tangled structures. Additionally, a too high concentration of ascorbic acid is unfavorable for the growth of tangled silver nanowires, and dendritic structures are formed. The surface-enhanced Raman scattering (SERS) activity was investigated using p-aminothiophenol (PATP) as a probe molecule. The silver tangled nanowires and dendritic structures show efficient surface enhanced Raman scattering property.

Ce-doped In₂O₃ nanofibers were synthesized by a simple and effective electrospinning method. The morphology and crystal structure of the as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM). The results revealed that the length of the nanofibers can reach several tens of micrometers and the average diameter was about 90 nm. The sensor fabricated from the 4% (w) Ce-doped In₂O₃ nanofibers showed the highest sensitivity to triethylamine. The sensitivity reached 2.6 when the sensor was exposed to 3 μL·L^-1 triethylamine and the response time and recovery time were about 5 and 6 s, respectively. Moreover, od selectivity was also observed in our investigation.

We used aluminum as the cathodic material and an aqueous solution of 3 mol·L^-1 NH₄NO₃ as the electrolyte in our work. Al₂O₃ nanoparticles were fabricated using asymmetrical electrodes during cathodic plasma electrolysis. The morphology and structure of the particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy dispersion (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). We identified cubic Al₂O₃ as the main component. The changes in current and optical emission phenomena during the cathodic plasma electrolysis were also studied. Based on the experimental results, we discuss the mechanisms responsible for particle formation.

We synthesized novel α-Fe₂O₃ nanocrystals (NFO-1) with single crystalline structure. In our synthetic strategy, the morphology and structure can be controlled simultaneously by the choice of inorganic salt (IS) and organic template (OT) in the extremely low precursor concentration reaction system. The evaporation-induced self-assembly (EISA) method was used to accelerate the reaction and to recover the synthesized α-Fe₂O₃ with high yields while preserving its favorable shape and structure. The morphologies and structures of the obtained α-Fe₂O₃ nanocrystals greatly influence their surface functionalization capability. The chemical interaction between NFO-1 and the surface functionalization agent (dopamine) was obviously enhanced because of its special spindle-likemorphology. The synthesis method described in this paper is suitable for the synthesis of other transition metal oxide single nanocrystals as well and we expect that this new route will be useful for the synthesis of novel nanomaterials.

Monodispersed superparamagnetic magnetite (Fe₃O₄) sub-microspheres with controlled grain sizes and diameters were obtained by a facile polyol solvothermal method using sodium citrate as an additive. The results show that citric ions, which strongly coordinate with iron atoms on the surface of magnetite, can be effectively adsorbed onto the surface of Fe₃O₄ nanoparticles. Therefore, the growth of the initially formed Fe₃O₄ nanoparticles is restrained and the electrostatic repulsive force changes. Consequently, both the diameter and the magnetic properties of the resultant Fe₃O₄ sub-microspheres can be easily tuned over a relative large range. Simply changing the concentration of citric or ferric ions can change both the diameter of the Fe₃O₄ nanoparticles which construct the resultant sub-microspheres as building blocks and that of the resultant sub-microspheres in a range of 220 -550 nm, resulting in monodispersed superparamagnetic magnetite sub-microspheres.