The growth of Cr-doped rutile TiO₂(110) homoepitaxial single crystal thin films was investigated using pulsed laser deposition (PLD) method. Surface morphology and electronic structure were characterized using scanning tunneling microscopy/spectroscopy (STM/STS), X-ray and ultraviolet photoemission spectroscopy (XPS/UPS). The optical absorption spectra were measured using ultravioletvisible (UV-Vis) absorption spectroscopy. From STM images, we observed that the atomic flat TiO₂(110)-(1×1) surface maintained at Cr doping concentration of 6% (atomic ratio), indicating a negligible effect of the Cr dopants on the surface morphology. The Cr doped ruteile TiO₂(110) film showed higher tunneling conductance than undoped rutile single crystal. XPS and UPS spectra indicated that Cr atoms bond to lattice O, exhibiting an +3 oxidation state of +3 and introducing an impurity state above the valence band maximum by 0.4 eV. The UV-Vis absorption spectrum of the Cr doped film showed an absorbance extended to ~650 nm, in a visible light range, which was consistent with the UPS spectra. Using the Cr-doped TiO₂ films, the dissociation of methanol molecules was only observed under the UV light illumination (wavelength shorter than 430 nm), however, the dissociation reaction was not observed under the visible light illumination (wavelength longer than 430 nm). Our results suggest that the monodoping by Cr element may not be sufficient to promote the visible light photoactivity of rultile TiO₂(110) surface.

Tremendous progress has been made in non-contact atomic force microscopy (NC-AFM) recently. The spatial resolution of NC-AFM imaging and spectroscopy of individual molecules on surfaces has reached true atomic resolution and bond differentiation level. Combination of NC-AFM with other scanning probe techniques can open a new way for materials, physics, chemistry, and biochemistry studies. In this review, we first introduce the basic principle of NC-AFM and qPlus sensor. The interaction force at atomic scale and precise measurement of short-range force are discussed. We summarize the recent advances in structural determination of organic molecules, chemical identification, electronic structure, and atomic manipulation at the atomic scale. In addition, we also discuss the application of Kelvin probe force microscopy (KPFM) in measurement of local contact potential difference (LCPD). Finally, perspectives and challenges in NC-AFM techniques are presented.

n-Decane is a component of commonly used fuels, but so far studies into its pyrolysis mechanism are rare and the few existing mechanisms are inconvenient to use owing to their large scales. A small-scale chemical kinetic model (Mech33) for describing the process of n-decane pyrolysis containing 33 species and 75 elementary reactions was constructed. Based on partial equilibrium and quasi-steady state assumptions through sensitivity analysis, a smaller kinetic model (Mech22) containing 22 species and 59 reactions was developed from Mech33. Simulations of n-decane pyrolysis using these two models were compared with experimental data from flow reactor and shock tube over a wide range of temperatures and pressures. The results showed that Mech33 and Mech22 could reproduce the process of n-decane pyrolysis well and accurately predict the concentrations profile of main products, and finally provide valuable chemical kinetic models for engineering simulations when coupled with computational fluid dynamics (CFD).

We investigated the field-dependent magnetic properties of chiral alanine crystals, especially associated with the electronic orbital motions. Based on the chirality of the zwitterionic model (⁺NH₃-C(CH₃)H-CO₂^-), and the helicity of the lattice structure of peptide bond in proteins, when an external field of +5 T was applied parallel to the preferred axis c(z) of the N⁺H…O^- hydrogen bond in D-alanine, the electron spin-flip manifested emergent paramagnetism at 297.6 K. Because the spin magnetic dipole moment of hydrogen in L-alanine was originally aligned antiparallel to the field, the electron spins flipped firstly perpendicular to the field then manifested paramagnetism at 303.9 K. The magnetic field of 5 T split a degenerate energy level in the paramagnetic state of chiral alanine. Furthermore, the spin-orbital separation of the quasi-one dimensional N⁺H…O^- hydrogen bond in the crystal lattice provided evidence for the hallmark of one-dimensional physics.

Calorimetry is a direct experimental method that can be used to study the thermodynamics of weak interactions between surfactant molecules, allowing the energetic parameters of such interactions to be obtained. In this work, a nano-isothermal titration calorimeter with a thermostat (TAM III) was used to evaluate the thermodynamic behavior of molecular self-assemblies of single and mixed surfactants in aqueous solution. Electrical calibration of this instrument showed that its precision is better than ±0.09%. The accuracy of the system was tested by measuring the reaction heat of tris-hydroxymethylaminomethane (Tris), employed often as a calorimetric standard substance, with hydrochloric acid. The resulting value ((-47.48±0.12) kJ·mol^-1) agreed well with that in the literature. We then determined the critical micelle concentration (cmc) and enthalpy of micellization for dodecyltrimethylammonium bromide (DTAB) with a“head-and-tail”structure, which were consistent with reported values, as well as reliable results for sodium cholate (NaC) with a rigid steroid skeleton composed of hydrophilic and hydrophobic surfaces. Furthermore, for the mixed system of oppositely charged surfactants (DTAB/NaC), the mixed cmc and enthalpy of mixed micellization were also obtained in NaC- and DTAB-rich regions. A stronger synergistic effect was observed between the two types of surfactants in the NaC-rich region than in the DTAB-rich one. Conductivity measurements allowed the thermodynamic behavior of the mixed system (DTAB/NaC) to be discussed in detail.

Four isostructural heterobinuclear Zn-Ln (Ln=Eu or Tb) complexes are prepared through the self-assembly of benzimidazole derivatives 2-(2-hydroxy-3-methoxyphenyl)benzimidazole (HL¹) or 2-(5-bromo-2-hydroxy-3-methoxyphenyl)benzimidazole (HL²) with Zn(CH₃COO)₂·2H₂O and Eu(NO₃)₃·6H₂O or Tb(NO₃)₃·6H₂O). The complexes are characterized by single-crystal X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, elementary analysis, and electrospray ionization mass spectrometry (ESIMS). Three of the complexes form single crystals, while the fourth is polycrystalline. UV-Vis absorption, excitation and emission spectra of the Tb³⁺-based complexes reveal strong, characteristic luminescence from Tb³⁺ with emissive lifetimes in the microsecond range. Therefore, Tb³⁺ has been sensitized from the excited state of the ligands because of effective intramolecular energy transfer. The Eu³⁺ complexes do not show characteristic emission because of deactivation by a different pathway.

The mechanisms of the Reduning injection on the influenza virus were studied by computer methods at the molecular level, including docking and network analysis. A neuraminidase (NA) activity assay was used to verify the predicted results in vitro. Results show that most of the compounds in the Reduning injection exhibit od drug-like properties. The mechanism of the Reduning injection may be that it affects viral entry, RNA synthesis, or viral release, which limits influenza virus replication. Potential active molecules of the Reduning injection were found by analyzing the network parameters of compound-target interaction networks. The experimental results suggest that of the potential active molecules, luteolin displayed significant inhibitory activity toward the influenza A virus, while quercetin proved less effective, which supports the predicted results.

Density functional theory (DFT) calculations have been performed to explore the molecular structure, electronic structure, and O－H bond dissociation enthalpy of myricetin. Possible antioxidation mechanisms between lipid peroxide radical CH₃OO· and myricetin have been discussed. DFT calculations at the M06-2X/6-31++G(d,p) level indicated that the 4'-OH group of myricetin is the most active site on the basis of the stability of dehydrogenated myricetin radicals, O－H bond dissociation enthalpy, and hydrogen abstraction activation barrier, as well as kinetic data for myricetin determined at different temperatures. The relatively high activity of the 4'-OH site can be ascribed to weak hydrogen-bonding interactions between the oxygen radical of the reactive OH group and the adjacent OH group in the B-ring, which is retained upon ing from free myricetin to reactant complex to product according to atoms in molecule (AIM) analysis. The hydrogen-bond helps to stabilize the electronic deficiency generated on the oxygen radical during the hydrogen abstraction reaction. All calculations are in agreement with the structure-activity relationship previously established for myricetin by considering its antioxidant activity. Present calculations provide theoretical basis for the designing new antioxidants.

The structural, electronic, and magnetic properties of Ti_nO₂ and Ti_nO₂^- (n=1-10) clusters are studied using density functional theory with the B3LYP hybrid density functional. The calculated geometries show that the two dissociative oxygen atoms remain on the surface of pure Ti_n clusters and do not change the geometry of Ti_n much. The two oxygen atoms exist in the vicinity of Ti_nO₂ clusters, exhibiting an O-Ti-O connection in Ti_nO₂. The geometries of the lowest-energy neutral and anionic clusters are similar. Stability analyses reveal that Ti_nO₂ clusters are highly stable, especially TiO₂ and Ti₇O₂ clusters. In addition, the ionization potentials, electron affinities, electron detachment energies, and energy gaps of the systems are carefully investigated. On the basis of their optimized structures, we discuss the magnetic properties of the two systems. Charge transfer occurs from Ti to O atoms, mainly between Ti-3d, Ti-4s, and O-2p orbitals of Ti_nO₂ clusters. Antiferromagnetic ordering is dominant in the two systems. The magnetic moment of Ti_nO₂ is clearly dominated by the localized 3d electrons of Ti atoms, and the two oxygen atoms contribute a very small amount of spin in Ti_nO₂ clusters.

The geometries of the ground and excited states of titanium dioxide, ¹A₁, ¹B₂, ³B₂, ¹B₁, ³B₁, ¹A₂ and ³A₂, have been optimized using Møller-Plesset second-order perturbation theory, density functional theory B3LYP, and time-dependent density functional theory TD-B3LYP methods. ¹A₁, ¹B₂, ³B₂, ¹B₁ and ³B₁ have bent structures, while ¹A₂ and ³A₂ have symmetrical linear structures. The bond angles of ¹B₂, ³B₂, ¹B₁ and ³B₁ correlate directly with the magnitudes of the corresponding bond dipole moments. Vertical and adiabatic excitation energies have been computed with complete active space self-consistent field (CASSCF) CASSCF(6,6), CASSCF(8,8), multi-reference configuration interaction (MRCI), and TD-B3LYP. For ¹B₂、³B₂ and ¹B₁, the excitation energies calculated with MRCI/CASSCF(6,6) are much closer to the experimental values than the results calculated using other methods. For excited states ³B₁, ¹A₂ and ³A₂, excitation energies calculated with CASSCF(6,6), CASSCF(8,8), MRCI, and TD-B3LYP are almost consistent with theoretical results available in the literature. Dipole moments of the ground and excited states have been computed with B3LYP and TD-B3LYP. The calculated dipole moments of ¹A₁ and ¹B₂ agree well with experimental data. The atomic charges of TiO₂ in ground and excited states have been calculated with the atomic dipole moment corrected Hirshfeld population method. This calculation revealed that changes of dipole moments from the ground state to the excited states are related to electron transfer from the oxygen atom to the titanium atom. During the above calculations, the influences of the basis sets cc-pVDZ, cc-pVTZ, and cc-pVQZ were also investigated.

A heptamethine cyanine dye containing an organoselenium functional group is a near-IR fluorescent probe that operates based on photoinduced electron transfer (PET). This probe can be used for highly sensitive and selective monitoring of peroxynitrite under physiological conditions. In this paper, the photophysical properties and PET mechanism of the probe molecule were investigated by time-dependent density functional theory (TD-DFT) calculations. The results indicated that the excitation in the fluorophore involves an electron transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). The HOMO level of the recognizer moiety increased in energy above that of the HOMO occupied with a single electron of the fluorophore, leading to transfer of one electron to the heptamethine cyanine moiety, which quenched the fluorescence emission. After the Se moiety was oxidized, the HOMO level of the recognizer moiety decreased in energy, the PET process was prevented, and the fluorescence emission was recovered. It was further proposed that the PET was contributed to by the p electron of the nitrogen atom in the aniline moiety of the probe. The PET efficiency is regulated by the oxidation and reduction events of the organoselenium moiety, resulting in“on-off”fluorescence emission.

The activity of a pyromellitimide-bridged polyphthalocyanine Fe(II) catalyst for O₂ reduction is studied by density functional theory calculations. Three model molecules with different polymerization degrees are designed to investigate O₂-reduction electrocatalytic reactivity. The molecular and electronic structures of the models and their O₂-complexes are optimized with BP86 functional and SVP basis sets. The central Fe atom in the catalyst binds O₂ by a double bond followed by a charge transfer to reduce O₂. This study indicates that the catalyst has potential for O₂-reduction electrocatalytic activity. The calculated frontier molecular orbitals and stabilities of the O₂-complexes demonstrate that catalysts with a higher polymerization degree and stronger electron-withdrawing groups will have higher activities for O₂ reduction. O₂-reduction activity of the catalyst is achieved via an electrocatalytic cycle.

Para-xylene is an important petrochemical that can be produced by the methylation of toluene. Here, the mechanism of toluene methylation with dimethyl carbonate (DMC) or methanol catalyzed by H-ZSM-5 was studied using the“our own N-layered integrated molecular orbital+molecular mechanics” (ONIOM) in combination with density functional theory (DFT) methods. The adsorption of reactants and desorption of products are considered, and the structures of important intermediates and transition states are described. Computational rate constants are used to estimate the kinetic activity of toluene methylation reactions. The reaction mechanism of toluene methylation with DMC and that with methanol catalyzed by H-ZSM-5 differ. Toluene methylation with DMC involves full decomposition of DMC prior to methylation to form xylene isomers. In contrast, methanol is more active than DMC as the methylation reagent in toluene methylation. The stepwise and concerted paths of toluene methylation with methanol have similar intrinsic activation energies. At 773 K, the stepwise path has a higher rate constant than the concerted one. For toluene methylation with both reagents, para-xylene formation is kinetically preferred, whereas meta-xylene is the lowest-energy product. The results of our calculations agree well with experimental observations.

A simple galvanostatic electrodeposition method was used to synthesize an active Ni-Sn electrode on a Cu foil substrate. Characterization by high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) revealed that the crystal structures of the deposited films transformed from amorphous structures composed of Ni crystal embryos and amorphous Ni-Sn to Ni₃Sn₄/ Ni₃Sn₂ mixed crystals with increasing Sn content. Scanning electron microscope (SEM) images indicated that the amorphous Ni-Sn electrode possessed a smooth surface with uniform distribution of small particles, whereas the Ni₃Sn₄/Ni₃Sn₂ mixed crystalline electrode exhibited a rough surface composed of lamellar structures. The polarization curves measured in 1 mol·L^-1 NaOH solution at 25℃ indicated that the amorphous Ni-Sn electrode showed a smaller overpotential (85 mV) and better electrocatalytic performance for hydrogen evolution than the mixed crystalline electrode. Electrochemical impedance spectroscopy (EIS) results showed that the hydrogen evolution reaction occurs on the Ni-Sn alloy electrode under a mixture of Volmer and Heyrovsky control. The higher activity of the amorphous Ni-Sn electrode was attributed to the faster charge transfer and electrochemical adsorption and desorption rates of hydrogen atoms compared with those on the mixed crystalline electrode.

Nano-WO₃ modified carbon nanotube supported Pt nanoparticles (Pt/WO₃-CNTs) with uniform dimension were prepared by impregnated precipitation method, and Pt nanoparticles were loaded on the surface of WO₃-CNTs by means of microwave-assisted glycol method. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) reveal that the Pt nanoparticles have a face-centered cubic crystal structure and are highly dispersed on the surface of WO₃-modified CNTs with a narrow size distribution between 3 and 5 nm. X-ray photoelectron spectroscopy (XPS) shows that more metallic Pt is present on Pt/ WO₃-CNTs than on Pt/CNTs catalyst. Compared with the Pt/CNTs catalyst without WO₃ modification, the Pt/ WO₃-CNTs composite catalyst not only shows relative large electrochemical active surface area, high catalyst activity toward methanol electro-oxidation, but also exhibits very high stability with apparent antiposion tolerance to the incomplete oxidized species during methanol oxidation.

Microporous carbon was prepared using a novel procedure based on a zinc(II)-organic coordination polymer. The polymer was prepared through the coordination interaction of zinc ions with tartaric acid, and then it was introduced into the open networks of resorcinol/formaldehyde (R/F) resol using hydrogen-bonding interactions. The R/F resol and zinc-organic coordination compound system copolymerized to produce an R/F and zinc-organic coordination copolymer. The copolymer was then heat-treated at 950℃ to decompose and evaporate zinc to fabricate microporous carbon materials. The carbon materials possessed relatively regular large micropores, with a specific surface area of up to 1260 m²·g^-1 and a total pore volume of 0.63 cm³·g^-1. The resultant microporous carbon materials were used as supercapacitor electrodes, exhibiting an equivalent series resistance of 0.46 Ω, and ideal capacitive behavior with a rectangular shape in cyclic voltammograms. Galvanostatic charge/discharge measurements of the carbon materials gave a specific capacitance of 196 F·g^-1 at a current density of 1 A· g^-1 and 137 F·g^-1 at a large current density of 10 A·g^-1. A high retention of 98% was measured for the long-term cycling stability (~1000 cycles) of the mesoporous carbon. Overall, the microporous carbon materials exhibited very od electrochemical performance. This study highlights the potential of well-designed microporous carbon materials as electrodes for diverse supercapacitor applications.

In the present work, NiCo₂O₄ nanowires grown directly on carbon fibers self-organize into a nanoflower morphology. The materials are prepared by hydrothermal treatment and subsequent low-temperature annealing. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) results reveal a hierarchical three-dimensional mesoporous structure, which facilitates ion transport and electronic conduction for fast redox reactions. As a result, the electrode achieves a respectable specific capacitance of 1626 F·g^-1 at 1 A·g^-1 and high rate capability (65% retention at 10 A·g^-1), so it shows promise for application in supercapacitors.

LiFePO₄/C composite was prepared by two-step synthesis route, with LiH₂PO₄ and FeC₂O₄· 2H₂O as starting materials. In the process, the carbon sources polyvinyl alcohol (PVA) and glucose were added in a stepwise fashion. The well-crystallized LiFePO₄/C composite with homogeneous small particles was obtained after reacting at 700℃ for 4 h. This composite had a discharge specific capacity of 157.3 mAh·g^-1 at 0.1C rate and 138.4 mAh·g^-1 at 1C rate. On the basis of carbon coating modification, Nb-ion-doped LiFe_1-xNb_xPO₄/C (x=0.005, 0.01, 0.015, 0.02) composites were prepared. The optimized LiFe_0.99Nb_0.01PO₄/C cathode displayed a discharge specific capacity 160.5 mAh·g^-1 at 0.1C discharge rate, 136.0 mAh·g^-1 at 5C and maintained 134.8 mAh·g^-1 after 50 cycles, showing od rate properties and cycling stability. Cyclic voltammetry (CV) measurements indicated that aliovalent dopant substituting on the Fe sites can reduce the resistance of Li ion diffusion in the electrode process, increase phase transformation kinetics during cycling, and enhance the reversibility of LiFePO₄ electrodes.

Poly(aryl ether ketone)/sulfated poly(vinyl alcohol) (S-SPAEK/SPVA) composite membranes with different mass fractions of SPVA were prepared by solution casting using highly sulfonated side-chaintype sulfonated poly(aryl ether ketone) and sulfated poly(vinyl alcohol) as raw materials. Fourier transform infrared (FTIR) spectroscopy confirmed the structure of the S-SPAEK/SPVA composite membranes. Scanning electron microscope (SEM) images showed that SPVA was uniformly dispersed in an S-SPAEK polymer matrix. The uptake and swelling behavior, water retention capacity, methanol permeability, and proton conductivity of the composite membrane were investigated systematically. The performance testing of the composite membranes revealed that thermal stability and water absorption and retention capabilities were improved by introduction of SPVA. The methanol permeability of S-SPAEK/SPVA composite membranes decreased as the content of SPVA increased because the hydroxyl groups could effectively obstruct diffusion of methanol molecules. The methanol diffusion coefficients of the composite membranes decreased from 7.9×10^-7cm²·s^-1 for S-SPAEK/SPVA5 to 1.3×10^-7 cm²·s^-1 for S-SPAEK/SPVA30; considerably lower than 11.5×10^-7 cm²·s^-1 for the pure S-SPAEK membrane. The water absorption and retention capabilities increased as the numbers of hydrophilic groups increased by introduction of SPVA. As a result, the proton conductivity of the composite membranes increased with increasing water absorption and retention capabilities according to the Vehicle and Grotthuss mechanisms. The flexible chain segment of SPVA interacted strongly with the pendant chain of S-SPAEK, aiding hydrophilic/ hydrophobic separation, and improving the proton conductivity of the composite membranes. The proton conductivity of the S-SPAEK/SPVA30 composite membrane reached 0.071 and 0.095 S·cm^-1 at 25 and 80℃, respectively. These results show that S-SPAEK/SPVA composite membranes are promising for application in direct methanol fuel cells.

Fe₃O₄ nanoparticles with a highly symmetric octadecahedral nanobox structure were fabricated using β-cyclodextrin as a protection agent. A series of composites (CM-1-CM-4) of polyethylene glycol (PEG) and Fe₃O₄ nanoparticles with different initial mass ratios were prepared using a colloid process. We found that the shape of the composites depended on the amount of Fe₃O₄ nanoparticles. In particular, the melting process of PEG was not only influenced by the presence of Fe₃O₄ nanoparticles, but also by their amount. We also noticed that the crystallinity of PEG lowered upon compositing with Fe₃O₄ nanoparticles, and decreased as the amount of Fe₃O₄ nanoparticles increased with the exception of CM-4. Interestingly, the degradation of PEG was affected by the Fe₃O₄ nanoparticles, leading to the appearance of different degradation products. Like the initial Fe₃O₄ nanoparticles, the Fe₃O₄ components in the composites exhibited typical soft ferromagnetism but possessed much lower saturation magnetizations. X-ray photoelectron spectroscopy (XPS) experiments revealed that electronic shift occurred from iron to oxygen. The resulting decrease in the electronic density of iron explained the observed decrease in saturation magnetizations of the composites. The composites induced strong surface-enhanced Raman scattering of organic dyes that depended on the amount of Fe₃O₄ nanoparticles in the composite. This study contributes to the development of composite materials combining polymers with inorganic nanoparticles.

The rheological behavior of carboxylate gemini surfactant O,O'-bis(sodium 2- tetradecylcarboxylate)-p-dibenzenediol (referred to as C₁₄Φ₂C₁₄) with a concentration of 140 mmol·L^-1 in aqueous solution in the presence of 100 mmol·L^-1 NaBr was investigated by frequency sweep and steady rate sweep measurements. The solution showed the characteristics of a Maxwell fluid with a single stress relaxation time at low shear frequencies. Analysis by the living polymer model indicated that C₁₄Φ₂C₁₄ formed long (3.6-6.8 μm) wormlike micelles at 25℃, which were observed by cryo-transmission electron microscopy (cryo-TEM). The micelles were entangled with each other, resulting in a very viscous solution (the zero-shear viscosity was as high as 1.10×10⁴ Pa·s) that looked like a gel. On raising the temperature to 70℃, the relative viscosity was still as high as 1.8×10⁴, which is very rare for anionic wormlike micelle systems. The flow activation energy (E_a) was estimated to be (141±5) kJ·mol^-1. The size distribution of C₁₄Φ₂C₁₄ was determined by dynamic light scattering. Large aggregates with a size of ~100 nm were observed at low concentrations of 5-10 mmol·L^-1. These large aggregates readily transformed into rodlike and then wormlike micelles as the surfactant concentration increased.

Column and batch adsorptions of As(V) on TiO₂ particles were conducted to investigate the influence of adsorption mode on metastable-equilibrium adsorption. Under the same thermodynamic conditions, a fixed amount of As(V) was added to both column and batch adsorption systems. Batch adsorption achieved equilibrium more quickly than column adsorption, and the equilibrated adsorption capacity of 0.42 mg·g^-1 for the batch adsorption system was considerably greater than 0.25 mg·g^-1 determined for the column adsorption system. Moreover, the adsorption irreversibility of the batch adsorption system was weaker than that of the column adsorption system. This indicated that the change of adsorption reaction mode (i.e., kinetic processes) could result in different metastable-equilibrium adsorption states under the same thermodynamic conditions. The discrepancy of adsorption behavior between column and batch adsorption systems should be caused by their different liquid film diffusion coefficients and total mass transfer coefficients, as well as different microscopic metastable-equilibrium adsorption states.

To investigate the adsorption properties and roles of different feed gases in the selective catalytic reduction by ammonia (NH₃-SCR), the adsorption sites, strength, and amount as well as reaction rates of NH₃ and NO_x (a mixture of NO and NO₂) on exchanged Cu/SAPO-34 (chabazite zeolite) catalyst were studied. Transient response, temperature programmed desorption (TPD), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments were performed to characterize the catalyst. Transient response experiments showed that NH₃ was adsorbed by the catalyst. TPD and DRIFTS indicated that NH₃ can be adsorbed at both Br?nsted and Lewis acid sites to form various NH₃ adsorption species that show different SCR activities. The adsorption rate of NH₃ by Cu²⁺ cations was the fastest and the adsorption bond strength of NH₃-Cu²⁺ was the strongest between NH₃ and the Cu/SAPO-34 catalyst. NO_x can be oxidized and stored as nitrates and nitrites on the Cu catalyst. The intermediate species formed at Cu active sites during the NH₃-SCR reaction are discussed, allowing SCR reaction mechanisms to be inferred.

An SrB₂O₄/SrCO₃composite catalyst is synthesized by the simple sol-gel method. Reduction of carbon dioxide into methane in the presence of water is used to evaluate the photocatalytic activity of the composite catalyst. SrB₂O₄/SrCO₃exhibits better photocatalytic performance than TiO₂(P25) and SrB₂O₄ under irradiation with UV light. The crystalline structure, crystallite size, and the BET surface areas of the resultant photocatalysts are studied via the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherms. The energy levels of the SrB₂O₄/SrCO₃ photocatalyst are determined from characterization with UV-Vis diffuse reflectance absorption spectra, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) measurements. The heterojunction formed at the SrB₂O₄/SrCO₃interface efficiently promotes photogenerated carrier separation and increases the use of photogenerated carriers in photocatalytic reactions at the solid/liquid interface, resulting in high photocatalytic activity under UV light.

Single crystals of anatase TiO₂ with exposed (001) and (101) facets were synthesized by a hydrothermal method. We carried out photocatalytic reduction reactions to deposit noble metals (Au, Ag, and Pt) and photocatalytic oxidation reactions to deposit metal oxides (PbO₂ and MnO_x) on the surface of TiO₂. The deposited anatase TiO₂ samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) to study the roles of the two facets of anatase TiO₂ in photocatalytic reactions. The noble metals were selectively deposited on the exposed (101) facet, while metal oxides were selectively deposited on the exposed (001) facet. This result indicated that photogenerated electrons and holes mainly accumulated on the (101) and (001) facets, and then took part in photocatalytic reduction and oxidation reactions, respectively. These results also suggested that the simultaneous exposure of the two facets could facilitate charge separation. Therefore, it was proposed that the simultaneous exposure of two facets with different functions will be a new strategy to effectively promote photocatalytic reaction.

The asymmetric hydrogenation of aromatic ketones catalyzed by cinchona- and triphenylphosphine (tpp)-modified Ir/SiO₂ was studied. The heterogeneous enantioselective hydrogenation of heterocyclic ketones using a supported iridium catalyst was also investigated. Different analytical techniques, including inductively coupled plasma-atomic emission spectroscopy (ICP-AES), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), the Brunauer- Emmett-Teller (BET) method, infrared (IR) spectroscopy, ³¹P solid state nuclear magnetic resonance (NMR) spectroscopy, homogeneous- heterogeneous comparison experiment, conventional filtering test, and mercury poisoning experiment, were used to characterize the catalytic system. HRTEM, XPS, and the BET method clearly characterized the catalytic system. IR and ³¹P solid state NMR spectra provided useful information about the interactions between modifier, metal, and stabilizer. The homogeneous-heterogeneous comparison experiment, conventional filtering test, and mercury poisoning experiment clearly showed the differences between supported, and homogeneous catalysts. In addition, the effects of different stabilizers, modifiers, iridium content, solvents, and base additives on the asymmetric hydrogenation of aromatic ketones were investigated in detail. The results showed that cinchona alkaloids positively modified the Ir/ SiO₂ catalyst. Under the optimum conditions, the hydrogenation enantioselectivities of acetophenone and its derivatives were 52%-96%. The enantioselectivities of the hydrogenation products of 4-acetopyridine, 2-acetothiophene, and 2-acetofuran reached 74%, 75%, and 63%, respectively.

We prepared few-layer graphene samples by liquid-phase exfoliation in ethanol. By controlling the solvent temperature, sonication time and power, and centrifugation speed and time, we fabricated several-layer graphene from highly oriented pyrolytic graphite (HOPG). The obtained supernatant was added dropwise onto freshly cleaved mica surfaces. Nanotribological study of the samples under high vacuum by atomic force microscope (AFM) showed that frictional force decreased as the number of monolayers (ML) of graphene increased, and their frictional coefficient remained constant when the sample was thicker than about 4 ML. When the coverage reached 7 ML, the frictional coefficient was close to zero. In wear experiments, 2-ML graphene exhibited better wear resistance than the 4-ML sample and had no dependence on directional friction. We also measured the adhesion force of samples containing different numbers of layers of graphene and the mica surface, and found that substrate adhesion is not the main reason for the wear resistance properties of 2-ML graphene. Compared with single-layer graphene, the low friction coefficient of few-layer graphene makes it promising for application in areas such as data storage devices, nanoelectromechanical systems, and anti-wear coatings.

Nanoporous silicon nitride membranes are fabricated by combining polystyrene colloidal lithography with Micro-Electro-Mechanical Systems, and then freestanding bilayer lipid membranes are constructed across the nanopores by the vesicle method. The topography and mechanical properties of the freestanding bilayer lipid membranes are investigated using the imaging and force curve modes of variable-temperature atomic force microscopy (AFM). The fluidity and self-repair of the freestanding bilayer lipid membranes are observed by AFM, which gives enough freestanding area for further investigations. Force curve measurements demonstrate that both breakthrough and adhesion forces decrease as the temperature increases; i.e., the mechanical stability of freestanding bilayer lipid membranes decreases as the temperature rises. The breakthrough force of freestanding bilayer lipid membranes is smaller than that of supported membranes. Moreover, the adhesion force of freestanding bilayer lipid membranes varies in the opposite manner to that of supported membranes.

Stainless steel (AISI 316L) is commonly used as a material in medical devices. Modification of the metal surface with bioactive molecules and/or nanoparticles to develop next-generation smart biomaterial, e.g., cardiovascular stents, has recently attracted great attention. The present work investigated adsorption of antibodies and enzymes on micro/nanoporous 316L stainless steel compared with that on smooth and ld-coated stainless steel surfaces. The experimental results showed that the micro/nanoporous stainless steel surface produced by electrochemical erosion can adsorb a large amount of proteins (antibodies or horse radish peroxidase (HRP)), with comparable or better results than the sputtered- ld surface. Washes with surfactants (e.g., 10% bull serum albumin (BSA) or 0.2% Tween 20 solution) did not remove the enzymes/antibodies. In contrast, pretreatment of the metal plates with 5% Tween 20 halved antibody adsorption but did not affect adsorption of HRP. The wettability of the porous metal surface coated with proteins depended on the protein species and amount of protein adsorbed. The protein-coated porous surface was hydrophilic (water contact angle<50°), which should make it biocompatible. The proteins on the micro/nanoporous stainless steel surface retained their high biological activity; in particular, micro/nanoporous stainless steel stents modified with an anti-CD34 antibody using the present method can effectively and selectively capture KG-1 cells. Our work provides a basis for developing novel polymer-free, smart, economic biomaterials with stainless steel for biomedical applications.

The microscopic structure and properties of the interfacial regions in nanocomposites considerably affect the dielectric properties such as dielectric constant, dielectric loss, and breakdown strength. In this paper, we developed a method based on electrostatic force microscopy (EFM) to characterize the structures and the dynamic dielectric responses of the interfaces in TiO₂/epoxy nanocomposites. The nanometer-scale resolution of EFM enabled direct detection of the temperaturedependent dielectric response associated with the molecular dipoles of the epoxy chains at the interface between TiO₂ nanoparticles and epoxy matrix. In addition, different interfacial effects were obtained by the surface modification of TiO₂ nanoparticles. The EFM images showed that the investigated interfacial regions around the two types of TiO₂ nanoparticles exhibited different dielectric loss responses.