硫化镉胶粒界面自由基反应动力学的ESR研究

用电子自旋共振波谱方法研究了半导体超微粒子表面光诱导电子转移所引发的底物的次级自由基反应动力学过程．结果表明，用含有水溶性草酸盐的硫化镉（ＣｄＳ）胶体体系产生的ＣＯＯ－·离子基，可以较方便地引发其它自由基反应，并根据已知的由ＤＭＰＯ捕捉ＣＯＯ－·的反应速度常数数据，去计算ＣＯＯ－·基与其它可产生稳定自由基的化合物进行反应的速度常数值，从而在此基础上发展了一种研究自由基反应动力学的行之有效的简便的新途径和新方法，可以较广泛地应用于其它凝聚相的自由基反应动力学体系的研究．

Photocatalytic activity of Fe-doped diopside

UV-visible light induced photocatalytic degradation of methylene blue (MB) over Fe-doped diopside was investigated. The structure, composition, morphology and absorption property of UV-visible light of as-prepared samples were characterized using XRD, SEM, FTIR and UV-vis DRS. The experimental results show that doping Fe3+ induced the formation of some new species in diopside, and promoted light adsorption property of diopside in UV-visible region. Photochemical reactivity of Fe-doped diopside obviously depended on the content of doping Fe3+. The diopside with 1.848% Fe3+ exhibited the superior photocatalytic activity with 95% degradation of MB under UV-visible light for 3 h. The photocatalytic degradation kinetics of MB over all samples showed the first-order reaction nature.

Photochemical reactions of poly(3-butoxythiophene-2,5-diyl) with chloroform

Photochemical reactions of poly(3-butoxythiophene-2,5-diyl) with chloroform under irradiation with light were studied. The reactions were separately carried out under air, oxygen, and nitrogen. The obtained results showed that this reaction belongs to the pseudo-first-order reaction with a rate constant kobs of 1.4×10?5 s?1 at room temperature. The presence or absence of air, oxygen, and nitrogen did not have obvious effects on the reaction rate under irradiation with light.

Recent progress in production and usage of hydrogen peroxide

Hydrogen peroxide has attracted increasing interest as an environmentally benign and green oxidant that can also be used as a solar fuel in fuel cells.This review focuses on recent progress in production of hydrogen peroxide by solar-light-driven oxidation of water by dioxygen and its usage as a green oxidant and fuel.The photocatalytic production of hydrogen peroxide is made possible by combining the e^(-)and 4e-oxidation of water with the e^(-)reduction of dioxygen using solar energy.The catalytic control of the selectivity of the e^(-)vs.4e-oxidation of water is discussed together with the selectivity of the e^(-)vs.4e-reduction of dioxygen.The combination of the photocatalytic e^(-)oxidation of water and the e^(-)reduction of dioxygen provides the best efficiency because both processes afford hydrogen peroxide.The solar-light-driven hydrogen peroxide production by oxidation of water and by reduction of dioxygen is combined with the catalytic oxidation of substrates with hydrogen peroxides,in which dioxygen is used as the greenest oxidant.

Solar-heating boosted catalytic reduction of CO_(2） under full-solar spectrum

Catalytic converting CO2 into fuels with the help of solar energy is regarded as‘dream reaction’,as both energy crisis and environmental issue can be mitigated simultaneously.However,it is still suffering from low efficiency due to narrow solar-spectrum utilization and sluggish heterogeneous reaction kinetics.In this work,we demonstrate that catalytic reduction of CO2 can be achieved over Au nanoparticles(NPs)deposited rutile under full solar-spectrum irradiation,boosted by solar-heating effect.We found that UV and visible light can initiate the reaction,and the heat from IR light and local surface-plasmon resonance relaxation of Au NPs can boost the reaction kinetically.The apparent activation energy is determined experimentally and is used to explain the superior catalytic activity of Au/rutile to rutile in a kinetic way.We also find the photo-thermal synergy in the Au/rutile system.We envision that this work may facilitate understanding the kinetics of CO2 reduction and developing feasible catalytic systems with full solar spectrum utilization for practical artificial photosynthesis.

Laser Ablation Atomic Beam Apparatus with Time-Sliced Velocity Map Imaging for Studying State-to-State Metal Reaction Dynamics

We report a newly constructed laser ablation crossed molecular beam apparatus, equipped with time-sliced velocity map imaging technique, to study state-to-state metal atom reaction dynamics. Supersonic metal atomic beam is generated by laser vaporization of metal rod, and free expansion design without gas flow channel has been employed to obtain a good quality of metal atomic beam. We have chosen the crossed-beam reaction Al＋O2 to test the performance of the new apparatus. Two-rotational-states selected AIO（X^2∑＋, v=0, N and N＋I4） products can be imaged via P（N） and R（N＋14） branches of the Av=l band at the same wavelength, during （1＋1） resonance-enhanced multi-photon ionization through the AIO（D2E＋） intermediate state. In our experiment at 244.145 nm for simultaneous transitions of P（15） and R（29） branch, two rings in slice image were clearly distinguishable, corresponding to the AiO（v=0, N=IS） and AIO（v=0, N=29） states respectively. The energy difference between the two rotational levels is 403 cm^-1. The success of two states resolved in our apparatus suggests a better collisional energy resolution compared with the recent research study [J. Chem. Phys. 140, 214304 （2014）].

Research on the Mechanism of Accelerator for Photocurable Resin in 3D Printing

The photopolymerization kinetics of cycloaliphatic epoxide and oxetane with accelerators were investigated with Real-time Fourier transform infrared spectroscopy(RT-FTIR).The consumption rates of epoxy group and oxetane group as a function of time were obtained by monitoring of the absorption peaks in the 789 cm-1 and 981 cm-1.The effect of accelerators type and the accelerating mechanism were discussed.In general,benzyl alcohol and its analogues with electron-donating substituents are useful accelerators for the cationic polymerization of cycloaliphatic epoxide and oxetane.Activated monomer mechanism and free-radical chain-induced decomposition of onium salt cationic photoinitiator account for the observed accelerating effect on the polymerization rate.

Kinetics of Oxidation of Lactose with Photochemically Generated Radicals

Lactose milk sugar is found only in the milk of mammals. In order to understand the mechanism of oxidation of lactose, a systematic kinetic study of oxidation of lactose with photochemicaUy generated radicals was carried out. The reaction has a first order dependence on chloramine-T as well as on substrate. The reaction is catalysed by H＋ ions as well. On the basis of kinetic results and product analysis a probable mechanism were suggested.

Imaging Reaction Dynamics of Y+SO2

The reaction dynamics of yttrium atoms with sulfur dioxide molecules at a high collision energy of 36 kcal/mol was studied using time-sliced velocity map ion imaging,crossed molecular beam and laser-ablation method.The product YO was detected via multiphoton ionization at various wavelengths in the region of 482-615 nm.The slice images of YO show a broad velocity distribution and forward-backward peaking angular distribution.The forward scattering signal is stronger than its backward distribution.This indicates that the reaction proceeds via an intermediate complex and the lifetime of the intermediate state is less than one rotational period.The formation of complex suggests that electron transfer occurs in the oxidation reaction.

Advanced Techniques for Quantum-State Specific Reaction Dynamics of Gas Phase Metal Atoms

One of the themes of modern molecular reac tion dynamics is to charac terize elementary chemical reactions from“quan tum state to quan tum stat e”,and the study of molecular reaction dynamics in excited states can help test the validi ty of modern chemical t heories and provide met hods to cont rol chemical reactions.The subject of this review is to describe the recent experimental techniques used to study the reaction dynamics of metal atoms in the gas phase.Through these techniques,information such as the internal energy distribution and angular distribution of the nascent products or the three-dimensional stereodynamic reactivity can be obtained.In addition,by preparing metal at oms wi th specific exci ted elec tronic states or orbi tal arrangemen ts,information about the reactivity of the electronic states enriches the relevant understanding of the electron transfer mechanism in metal reaction dynamics.

Adsorption Reaction Dynamics of Systems Lysozyme and Nanodiamond/Nanosilica at pH=7-13

Adsorption reactions between surfaces of nanodiamond and nanosilica with diameter of 100 nm prepared as suspension solutions of 0.25μg/μL and lysozyme molecule with different concentrations of 7 mmol/L PPBS at pH=7, 9, 11, and 13 have been investigated by fluores- cence spectroscopy. Adsorption reaction constants and coverages of lysozyme with different concentrations of 0-1000 nmol/L under the influences of different pH values have been ob- tained. Helicities and conformations of the adsorbed lysozyme molecules, free spaces of every adsorbed lysozyme molecule on the surfaces of nanopartieles at different concentrations and pH values have been deduced and discussed. The highest adsorption capabilities for both sys- tems and conformational efficiency of the adsorbed lysozyme molecule at pH=13 have been obtained. Lysozyme molecules can be prepared, adsorbed and carried with optimal activity and helicity, with 2 and 10 mg/m2 on unit nanosurface, 130 and 150 mg/g with respect to the weight of nanoparticle, within the linear regions of the coverages at around 150-250 nmol/L and four pH values for nanodiamond and nanosilica, respectively. They can be prepared in the tightest packed form, with 20 and 55 mg/m2, 810-1680 and 580-1100 mg/g at threshold concentrations and four pH values for nanodiamond and nanosilica, respectively.

Studies of Photocatalytic Kinetics on the Degradation of Bisphenol A （BPA） by Immobilized ZnO Nanoparticles in Aerated Photoreactors

The photocatalytic kinetics of BPA （4, 4＇-isopropylidenediphenol）, a representative endocrine disruptor, was explored using immobilized ZnO nanoparticles as a photocatalyst in a laboratory scale photocatalytic reactor. The conditions of photocatalytic degradation were optimized. Direct photocatalytic degradation of BPA was undertaken in an aqueous solution containing ZnO nanoparticles under the optimized experimental conditions. The effects of various factors, such as initial BPA concentrations, initial pH values and various anions （CI, NO3, COa2, SO42-, HCO3＂） were investigated. In the case of the nanoparticles derived films, the photocatalytic efficiency was found not to be remarkably related with the calcination temperature employed in the coating process. Screen-printed ZnO nanoparticles films obtained in the optimal processing conditions showed that the photocatalytic activity is comparable to ZnO nanoparticles in aqueous suspensions. Over 90% degradation efficiency of BPA was achieved under the optimum conditions. The degradation rates in all photocatalytic experiments were linear with the degradation efficiencies of BPA by regression analysis （r ≥ 0.99）. The results showed that the degradation kinetics of BPA in the reactor with immobilized nano-ZnO film as photocatalyst was in agreement with a pseudo-first order rate law.

Photochemistry of Potassium Ferrocyanide and its Reaction with Uridine 5′-monophosphate in Aqueous Solution under Ultraviolet Irradiation

The photochemical reaction of potassium ferrocyanide(K_(4)Fe(CN)_(6))exhibits excitation wavelength dependence and non-Kasha rule behavior.In this study,the excited-state dynamics of K_(4)Fe(CN)_(6) were studied by transient absorption spectroscopy.Excited state electron detachment(ESED)and photoaquation reactions were clarified by comparing the results of 260,320,340,and 350 nm excitations.ESED is the path to generate a hydrated electron(e^(−)_(aq)).ESED energy barrier varies with the excited state,and it occurs even at the first singlet excited state(^(1)T_(1g)).The ^(1)T_(1g) state shows∼0.2 ps lifetime and converts into triplet[Fe(CN)_(6)]4−by intersystem crossing.Subsequently,3Fe(CN)_(5)]^(3-)appears after one CN−ligand is ejected.In sequence,H2O attacksFe(CN)_(5)]^(3-)to generate[Fe(CN)_(5)H_(2)O]^(3−)with a time constant of approximately 20 ps.The ^(1)T_(1g) state and e−aq exhibit strong reducing power.The addition of uridine 5′-monophosphate(UMP)to the K_(4)Fe(CN)_(6) solution decrease the yield of e−aq and reduce the lifetimes of the e−aq and ^(1)T_(1g) state.The obtained reaction rate constant of ^(1)T_(1g) state and UMP is 1.7×10^(14)(mol/L)^(−1)·s^(−1),and the e−aq attachment to UMP is∼8×10^(9)(mol/L)^(−1)·s^(−1).Our results indicate that the reductive damage of K_(4)Fe(CN)_(6) solution to nucleic acids under ultraviolet irradiation cannot be neglected.

Surface Photocatalysis-TPD Spectrometer for Photochemical Kinetics

A surface photocatalysis-TPD apparatus devoted to studying kinetics and mechanism of pho- tocatalytic processes with various signal crystal surfaces has been constructed. Extremely high vacuum （-0.2 nPa） in the ionization region is obtained by using multiple ultrahigh vacuum pumps. Compared with similar instruments built previously by others~ the H2, CH4 background in the ionization region can be reduced by about two orders of magnitude, and other residual gases in the ionization region can be reduced by about an order of magnitude. Therefore, the signal-to-noise ratio for the temperature programmed desorption （TPD） and time of flight （TOF） spectra is substantially enhanced, making experimental studies of pho- tocatalytic processes on surfaces much easier. In this work, we describe the new apparatus in detail and present some preliminary studies on the photo-induced oxygen vacancy defects on TiO2（110） at 266 nm by using the TPD and TOF methods. Preliminary results suggest that the apparatus is a powerful tool for studying kinetics and mechanism of photochemical processes.

Effects of Fluorescent Pair on the Kinetics of DNA Strand Displacement Reaction

Fluorescent labels are widely used in the characterizations of DNA-based reaction network operations.We systematically studied the effects of commonly used fluorescent pairs on thermal stabilities of signal-substrate duplex and the strand displacement kinetics.It is demonstrated that the modifications of duplex with fluorescent pairs stabilize DNA duplex by up to 3.5°C,and the kinetics of DNA strand displacement circuit is also evidently slowed down.These results highlight the importance of fluorescent pairs towards the kinetic modulation in designing nucleic acid probes and complex DNA dynamic circuits.

The roles of heterogeneous chemical processes in the formation of an air pollution complex and gray haze

Urban and regional air pollutions are characterized by high concentrations of secondary pollutants such as photo-oxidants （mainly ozone） and fine particulate matter, which are formed through chemical reactions of the primary pollutants emitted from various sources. The accumulation of these pollutants under stagnant meteorological conditions results in the formation of gray haze, reducing visibility and causing major impacts on human health and climate. In an air pollution complex, the co- existence of high concentrations of primary and secondary gaseous and particulate pollutants provides a large amount of reac- tants for heterogeneous reactions on the surface of fine particles; these reactions change the oxidizing capacity of the atmos- phere, as well as chemical compositions along with the physicochemical and optical properties of particulate matter, thereby accelerating formation of the air pollution complex and gray haze. Using in situ technologies, such as diffuse reflectance infra- red Fourier-transform spectroscopy and single-particle Raman spectroscopy, we systematically investigated the reaction kinet- ics and mechanisms of gaseous pollutants （i.e., NO2, SO2, 03, and formaldehyde） on the surfaces of the major components of atmospheric particles such as CaCO3, kaolinite, montmorillonite, NaC1, sea salt, A1203, and Tit2. We found that the main re- action products were sulfate, nitrate, or formate, which can change the hygroscopicity and light extinction parameters of those particles significantly. By analyzing the reaction kinetics of these heterogeneous reactions, we identified synergetic mechanisms of the three ternary reaction systems, ,i.e., NOE-particles-H2O, SO2-particles-O3, and organics/SO2-particles-UV illumination. These synergetic mechanisms can provide experimental and theoretical bases for understanding the feedback mechanisms and nonlinear processes in the formation of an air pollution complex and gray haze.

In-depth study on aminolysis of poly(ε-caprolactone): Back to the fundamentals

The aminolysis can effectively introduce primary amine （- quent surface fiiofunctionalization reactions. However, less NH2） groups onto polyester materials, enabling a variety of subse- attention has been paid to the basic knowledge of aminolysis reac- tion in terms of reaction kinetics and its influences on materials properties. In this study, taking the widely used poly（e-caprolactone） （PCL） as a typical example, the influences of diamines and solvent property on the surface -NH2 density are firstly assessed by using X-ray photoelectron spectroscopy （XPS） and colorimetric analysis. Results show that smaller dia- mine molecules and nonpolar alcohols could accelerate the reaction. The reaction kinetics with 1,6-hexanediamine is further investigated as a function of temperature, reaction time, and diamine concentration. During the initial stage, the reaction shows a 1^st order kinetics with the diamine concentration and has an activation energy of 54.5 kJ/mol. Ionization state of the -NH2 groups on the PCL surface is determined, revealing that the pKa of -NH3^＋ （〈5） is much lower than that of the corresponding diamine molecules in solution. After aminolysis, surface hydrophilicity of PCL membrane is significantly enhanced, while surface elastic modulus and average molecular weight are decreased to some extent, and others such as weight, surface mor- phology and bulk mechanical strength are not apparently changed. The introduced -NH2 groups are found to be largely lost at 37 ℃, but can be mostly maintained at low temperature.

Progress in femtochemistry and femtobiology

Femtoscience offers a unique way to understand the dynamics in physics, chemistry and biology. This subject focuses on the process happening at femto-to pico-second time scale by femtosecond optical methods. Widely used in chemistry it reveals chemical reactions, including bond breaking, forming, and stretching, which happens at an ultrafast time scale. Femtoscience is also important in the biological system, for example, light harvesting system and vision system. Femtoscience in physics is also widely used, but it is not studied in this paper. Instead, we report new advances in femtochemistry and femtobiology, including structural dynamics, coherent control, enzyme function dynamics and hydration in the protein system. We also introduce attosecond science, focusing on electron dynamics at an extreme short time scale.

Mechanistic study and kinetic properties of the CF_3CHO+Cl reaction

Theoretical investigations have been carried out on the mechanism and kinetics for the reaction of CF 3 CHO + Cl using duallevel direct dynamics method. The potential energy surface information was obtained at the MCQCISD/3//MP2/cc-pVDZ level and the kinetic calculations were done using variational transition state theory with interpolated single-point energy (VTST-ISPE) approach. The calculated results show that the reaction proceeds primarily via the H-abstraction channel, while the Cl-addition channel is unfavorable due to the higher barriers. The improved canonical variational transition-state theory (ICVT) with the small-curvature tunneling correction (SCT) was used to calculate the rate constants. The theoretical rate constants at room temperature are in general agreement with the experimental values. A three-parameter rate constant expression was fitted over a wide temperature range of 200-2000 K.