High PL quantum efficiency of poly(phenylene vinylene) systems through exciton confinement

Photoluminescence (PL) quantum efficiency is a key issue in designing successful light-emitting polymer systems. Exciton relaxation is strongly affected by exciton quenching at nonradiative trapping centers and the formation of excimers. These factors reduce the PL quantum yield of light-emitting polymers. In this work, we have systematically investigated the effects of exciton confinement on the PL quantum yield of an oligomer, polymer, and alternating block copolymer (ABC) PPV system. Time-resolved and temperature-dependent luminescence studies have been performed. The ABC design effectively confine photoexcitations within the chromophores, preventing exciton migration and excimer formation. An unusually high (PL) quantum yield (above 90%) in the solid state is reported for the alternating block copolymer PPV, as compared to that of similar to 30% of the polymer and oligomer model compounds. (C) 2000 Elsevier Science S.A. All rights reserved.

Effect on the property of the photoinduced carrier transport of CdS as sensitizer for TiO2 nanoparticulate thin films

The TiO2 nanoparticle thin films have been sensitized in situ with CdS nanoparticles. The SPS measurement showed that large surface state density was present on the TiO2 nanoparticles and the surface state can be efficiently decreased by sensitization as well as selecting suitable heat treatment, Both the photocurrent response and the charge recombination kinetics in TiO2 thin films were strongly influenced by trapping/detrapping of surface states. The slow photocurrent response of TiO2 nanoparticulate thin films upon the illumination was attributed to the trap saturation effects, The semiconductor sensitization made the slow photoresponse disappeared and the steady-state photocurrent value increased drastically, which suggested that the sensitization of TiO2 thin films with CdS could get a better charge separation and provide a simple alternative to minimize the effect of surface state on the photocurrent response.

Photosensitization of TiO2 nanoparticulate thin film electrodes by CdS nanoparticles

Surface photovoltage spectra (SPS) measurements of TiO2 show that a large surface state density is present on the TiO2 nanoparticles and these surface states can be efficiently decreased by sensitization using US nanoparticles as well as by suitable heat treatment. The photoelectrochemical behavior of the bare TiO2 thin film indicates that the mechanism of photoelectron transport is controlled by the trapping/detrapping properties of surface states within the thin films, The slow photocurrent response upon the illumination can be explained by the trap saturation effect. For a TiO2 nanoparticulate thin film sensitized using US nanoparticles, the slow photocurrent response disappears and the steady-state photocurrent increases drastically, which suggests that photosensitization can decrease the effect of surface states on photocurrent response.

Spectrometric investigation on the thermooxidative degradation of ethylene oxide and tetra-hydrofuran co-polyether

The thermooxidative degradtion of ethylene oxide and tetra-hydrofuran (EO-THF) co-polyether has been studied by electron spin resonance (ESR), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The initial degradation site was found to be at the a-carbon of the ether bond. Two free radicals which derived from dehydrogenation and oxygen addition were successfully detected by spin-trapping technique which used alpha -phenyl-N-tert-butyl nitrone(PBN) as spin trap. Both FT-IR and NMR have been used to follow structural changes of the copolyether during degradation. Nearly 20 product fragments including formate, carbonate, methyl, alcohol, methylene-dioxy, hydroperoxide and semiformal have been characterized by D-1 and D-2 NMR. The thermooxidtion of co-polyether preferred to occur on the THF units especially at the alternating linkage of EO and THF. Antioxidant (BHT) not only retarded the thermooxidation but also modified the degradation products with less ester and methylene-dioxy groups hut more hydroxyl and methyl groups.

An ESR study on (OH)-O-center dot-radical scavenging activity of water-soluble fullerenols

Water-soluble polyhydroxylated fullerene derivatives (fullerenol) were synthesized, and their scavenging ability for (OH)-O-.-radical was studied by the combination of ESR spectroscopy and spin-trapping technique with phenyl-t-butyl-nitrone. It was found that fullerenols showed an excellent efficiency in eliminating (OH)-O-. free radicals generated by UV photolysis of H2O2. At an applied fullerenol concentration of 0, 3 mg/mL in the final solution, a radical scavenging efficiency of approximate 95% was achieved, revealing the potential use of these compounds as novel potent free radical scavengers in biological systems.

Mass spectrometric evidence for the generation of benzyne from benzoyl peroxide in thermolysis

Benzoyl peroxide gave rise to benzoic acid (at m/z 122) in its electron impact mass spectrum, and its perdeuterated counterpart produced perdeuterobenzoic acid, C6D5CO2D, at m/z 128 under the same conditions, An intramolecular hydrogen abstraction is proposed for the formation of benzoic acid from the peroxide in thermolysis. As a result of this reaction, benzyne would be generated simultaneously. Anthracene was employed to trap any of the reactive intermediate benzyne. Collision-induced dissociation of the ion of m/z 254 from the mixture of benzoyl peroxide and anthracene indicated that triptycene was obtained by the trapping reaction, therefore confirming that benzyne is generated from benzoyl peroxide in thermolysis.

LUMINESCENCE AND ENERGY MIGRATION IN THE OXYAPATITE CA2GD8(SIO4)6O2 DOPED WITH SEVERAL RARE-EARTH AND MERCURY-LIKE IONS

Energy transfer phenomena have been observed by activating the oxyapatite host-lattice Ca2Gd8(SiO4)6O2 with Eu3+, Tb3+, Dy3+, Sm3+. This is based on the energy migration in the Gd3+ sublattice and trapping by the activators. The trapping efficiency for G

THERMAL-OXIDATION OF POLYPROPYLENE CONTAINING HINDERED PIPERIDINE COMPOUNDS

The thermal oxidation behaviour of polypropylene containing tetramethylpiperidine compounds and corresponding pentamethylpiperidine compounds are compared using air oven aging, oxygen uptake and thermogravimetry. Carbonyl formation, the induction period of oxygen absorption and weight loss have been selected to characterize the degree of oxidation. The results show that the stabilizing effectiveness of pentamethylpiperidines is always higher than that of tetramethyl types. Radical-trapping mechanisms cannot explain this, because large amounts of nitroxyl radicals are formed by the tetramethylpiperidine compounds. The quenching of singlet oxygen appears to be involved in thermal oxidation of polypropylene containing pentamethylpiperidine compounds. Specific hydrogen bonding between pentamethylpiperidines and hydroperoxide may account for their better thermal stabilizing action than tetramethylpiperidines.

Flux and fate of Yangtze river sediment delivered to the East China Sea

Numerous cores and dating show the Yangtze River has accumulated about 1.16 x 10(12) t sediment in its delta plain and proximal subaqueous delta during Holocene. High-resolution seismic profiling and coring in the southern East China Sea during 2003 and 2004 cruises has revealed an elongated (similar to 800 km) distal subaqueous mud wedge extending from the Yangtze River mouth southward off the Zhejiang and Fujian coasts into the Taiwan Strait. Overlying what appears to be a transgressive sand layer, this distal clinoform thins offshore, from similar to 40 in thickness between the 20 and 30 m water depth to < 1-2 in between 60 and 90 m water depth, corresponding to an across shelf distance of less than 100 km. Total volume of this distal mud wedge is about 4.5 x 10(11) m(3), equivalent to similar to 5.4 x 10(11) t of sediment. Most of the sediment in this mud wedge comes from the Yangtze River, with some input presumably coming from local smaller rivers. Thus, the total Yangtze-derived sediments accumulated in its deltaic system and East China Sea inner shelf have amounted to about 1.7 x 10(12) t. Preliminary analyses suggest this longshore and across-shelf transported clinoform mainly formed in the past 7000 yrs after postglacial sea level reached its mid-Holocene highstand, and after re-intensification of the Chinese longshore current system. Sedimentation accumulation apparently increased around 2000 yrs BP, reflecting the evolution of the Yangtze estuary and increased land erosion due to human activities, such as fanning and deforestation. The southward-flowing China Coastal Current, the northward-flowing Taiwan Warm Current, and the Kuroshio Current appear to have played critical roles in transporting and trapping most of Yangtze-derived materials in the inner shelf, and hence preventing the sediment escape into the deep ocean. (c) 2006 Elsevier B.V. All rights reserved.

Sedimentary features of the Yangtze River-derived along-shelf clinoform deposit in the East China Sea

A predominant sigmoidal clinoform deposit extends from the Yangtze River mouth southwards 800 kin along the Chinese coast. This clinoform is thickest (similar to 40m) between the 20 and 30 m isobaths and progressively thins offshore, reaching water depths of 60 and 90 m and distances up to 100 km offshore. Clay mineral, heavy metal, geochemical and grain-size analyses indicate that the Yangtze River is the primary source for this longshore-transported clinoform deposit. Pb-210 chronologies show the highest accumulation rates (> 3 cm/yr) occur immediately adjacent to the Yangtze subaqueous delta (north of 30 degrees N), decreasing southward alongshore and eastward offshore. The interaction of strong tides, waves, the China Coastal Current, winter storms, and offshore upwelling appear to have played important roles in trapping most Yangtze-derived sediment on the inner shelf and transporting it to the south. (c) 2006 Elsevier Ltd. All rights reserved.

An N-shape thermal front in the western South Yellow Sea in winter

An N-shape thermal front in the western South Yellow Sea (YS) in winter was detected using Advanced Very High Resolution Radiation (AVHRR) Sea Surface Temperature data and in-situ observations with a merged front-detecting method. The front, which exists from late October through early March, consists of western and eastern wings extending roughly along the northeast-southwest isobaths with a southeastward middle segment across the 20-50 m isobaths. There are north and south inflexions connecting the middle segment with the western and eastern wings, respectively. The middle segment gradually moves southwestward from November through February with its length increasing from 62 km to 107 km and the southern inflexion moving from 36.2A degrees N to 35.3A degrees N. A cold tongue is found to coexist with the N-shape front, and is carried by the coastal jet penetrating southward from the tip of the Shandong Peninsula into the western South YS as revealed by a numerical simulation. After departing from the coast, the jet flows as an anti-cyclonic recirculation below 10 m depth, trapping warmer water originally carried by the compensating Yellow Sea Warm Current (YSWC). A northwestward flowing branch of the YSWC is also found on the lowest level south of the front. The N-shape front initially forms between the cold tongue and warm water involved in the subsurface anti-cyclonical recirculation and extends upwards to the surface through vertical advection and mixing. Correlation analyses reveal that northerly and easterly winds tend to be favorable to the formation and extension of the N-shape front probably through strengthening of the coastal jet and shifting the YSWC pathway eastward, respectively.

油田高含水期剩余油分布规律研究

After systemic investigation of the techniques，route lines and mechanisms about the remaining oil，the dynamic migration and congregation behavior of the remaining oil are discussed on base of interaction between flowing and enriching of water and oil.After the micro-scope modeling of the fluid flow in porous media and the changes in petrol-physical properties of the flowing system, the characters of fluid fields and the dynamic distribution of oil are discussed, among which the preference-flowing is focused on. Based on the preference-flowing in porous media, the concept of the preference-flowing channels is developed. According to above, heterogeneous distribution of water and oil in the field and dynamic mechanism of remaining oil are all obvious. media can be divided into three kinds, directional, stochastic, arbitrary porous media. The main research results are as following: 1. Treating the characteristic parameters such as permeability, porosity and wettability as regional parameter, the fluid field with high water-cut has been established by geostatistical method, among which the difference of flowing pores and the changes of its petrol-physical properties during flooding are studied. 2. The flow process of water and oil are recurrent in physical simulation experiments, in which the mechanisms and phenomena are caught and analyzed. Fluid flow mechanics in porous media with preference-flowing channels have been studied. 3. The mutual coupling between water and oil is induced and the mathematical evolution equations including this interaction were built. . 4. Through coupling effect between flowing water and oil, the dynamic migration and congregation behavior of remaining oil depend upon this coupling. 5. Coupling between water and oil act as driving force and trapping force for the remaining oil. The coupling model of thesis has been verified by simplified the numerical model and compared results with Ng35 oil reservoir in Gudao oil field, it has important theoretical and application values for improving precision of remaining oil and production performance prediction, and is a new method for studying the mechanics of remaining oil in channeled porous media has been established. Key words：flow field，high water-cut，coupling，dominant flow in porous media，remaining oil

松辽盆地南部大情字井地区CO2埋存体地质格架及储层建模

Increasing attentions have been paid to the subsurface geological storage for CO2 in view of the huge storage capacity of subsurface reservoirs. The basic requirement for subsurface CO2 storage is that the CO2 should be sequestrated as supercritical fluids (physical trapping), which may also interact with ambient reservoir rocks and formation waters, forming new minerals (chemical trapping). In order to the effective, durable and safe storage for CO2, enough storage space and stable sealing caprock with strong sealing capacity are necessitated, in an appropriate geological framework. Up till now, hydrocarbon reservoirs are to the most valid and appropriate CO2 storage container, which is well proven as the favorable compartment with huge storage capacity and sealing condition. The thesis focuses on two principal issues related to the storage and sealing capacity of storage compartment for the Qingshankou and Yaojia formations in the Daqingzijing block, Southern Songliao Basin, which was selected as the pilot well site for CO2-EOR storage. In the operation area, three facies, including deltaic plain, deltaic front and subdeep-deep lake facies associations, are recognized, in which 11 subfacies such as subaqueous distributary channel, river- mouth bar, interdistributary bay, sheet sandbody, crevasse splay and overflooding plain are further identified. These subfacies are the basic genetic units in the reservoir and sealing rocks. These facies further comprise the retrogradational and progradational depositional cycles, which were formed base- level rise and fall, respectively. During the regressive or lake lowstand stage, various sands including some turbidites and fans occurred mostly at the bottom of the hinged slope. During the progradation stage, these sands became smaller in size and episodically stepped backwards upon the slope, with greatly expanded and deeped lake. However, most of Cretaceous strata in the study area, localized in the basin centre under this stage, are mainly composed of grey or grizzly siltstones and grey or dark grey mudstones intercalated with minor fine sandstones and purple mudstones. On the base of borehole and core data, these siltstones are widespread, thin from 10 to 50 m thick, good grain sorting, and have relative mature sedimentary structures with graded bedding and cross- lamination or crossbeds such as ripples, which reflect strong hydrodynamic causes. Due to late diagenesis, pores are not widespread in the reservoirs, especially the first member of Qingshankou formation. There are two types of pores: primary pore and secondary cores. The primary pores include intergranular pores and micropores, and the secondary pores include emposieus and fracture pores. Throat channels related to pores is also small and the radius of throat in the first, second and third member of Qingshankou formation is only 0.757 μm, 0.802 μm and 0.631 μm respectively. In addition, based on analyzing the probability plot according to frequency of occurrence of porosity and permeability, they appear single- peaked distribution, which reflects strong hetero- geneity. All these facts indicate that the conditions of physical property of reservoirs are not better. One reason may be provided to interpret this question is that physical property of reservoirs in the study area is strong controlled by the depositional microfacies. From the statistics, the average porosity and permeability of microfacies such as subaqueous distributary channel, channel mouth bar, turbidites, is more than 9 percent and 1md respectively. On the contrary, the average porosity and permeability of microfacies including sand sheet, flagstone and crevasse splay are less than 9 percent and 0.2md respectively. Basically, different hydrodynamic environment under different microfacies can decide different physical property. According to the reservoir models of the first member of Qingshankou formation in the No. well Hei47 block, the character of sedimentary according to the facies models is accord to regional disposition evolution. Meantime, the parameter models of physical property of reservoir indicate that low porosity and low permeability reservoirs widespread widely in the study area, but the sand reservoirs located in the channels are better than other places and they are the main sand reservoirs. The distribution and sealing ability of fault- fractures and caprock are the key aspects to evaluate the stable conditions of compartments to store CO2 in the study area. Based on the core observation, the fractures widespread in the study area, especially around the wells, and most of them are located in the first and second member of Qingshankou formation, almost very few in the third member of Qingshankou formation and Yaojia formation instead. In addition, analyzing the sealing ability of eleven faults in the three-dimensional area in the study area demonstrates that most of faults have strong sealing ability, especially in the No. well Hei56 and Qing90-27. To some extent, the sealing ability of faults in the No. well Hei49, Qing4-6 and Qing84-29 are worse than others. Besides, the deposition environment of most of formations in the study area belongs to moderately deep and deep lake facies, which undoubtedly take advantage to caprocks composed of mudstones widespread and large scale under this deposition environment. In the study area, these mudstones distribute widely in the third member of Qingshankou formation, Yaojia and Nenjiang formation. The effective thickness of mudstone is nearly ~550m on an average with few or simple faults and fractures. In addition, there are many reservoir beds with widely- developed insulated interbeds consist of mudstones or silty mudstone, which can be the valid barrier to CO2 upper movement or leakage through diffusion, dispersion and convection. Above all, the closed thick mud caprock with underdeveloped fractures and reservoir beds can be taken regard as the favorable caprocks to provide stable conditions to avoid CO2 leakage.

二氧化碳在孔隙咸水层中多相流动数值模拟研究

There has been a growing concern about the use of fossil fuels and its adverse effects on the atmospheric greenhouse and ecological environment. A reduction in the release rate of CO2 into the atmosphere poses a major challenge to the land ecology of China. The most promising way of achieving CO2 reduction is to dispose of CO2 in deep saline aquifers. Deep aquifers have a large potential for CO2 sequestration in geological medium in terms of volume and duration. Through the numerical simulation of multiphase flow in a porous media, the transformation and motion of CO2 in saline aquifers has been implemented under various temperature and hydrostatic pressure conditions, which plays an important role to the assessment of the reliability and safety of CO2 geological storage. As expected, the calculated results can provide meaningful and scientific information for management purposes. The key problem to the numerical simulation of multiphase flow in a porous media is to accurately capture the mass interface and to deal with the geological heterogeneity. In this study, the updated CE/SE (Space and time conservation element and solution element) method has been proposed, and the Hybrid Particle Level Set method (HPLS) has extended for multiphase flows in porous medium, which can accurately trace the transformation of the mass interface. The benchmark problems have been applied to evaluate and validate the proposed method. In this study, the reliability of CO2 storage in saline aquifers in Daqingzi oil field in Sunlong basin has been discussed. The simulation code developed in this study takes into account the state for CO2 covering the triple point temperature and pressure to the supercritical region. The geological heterogeneity has been implemented, using the well known geostatistical model (GSLIB) on the base of the hard data. The 2D and 3D model have been set up to simulate the CO2 multiphase flow in the porous saline aquifer, applying the CE/SE method and the HPLS method .The main contents and results are summarized as followings. (1) The 2D CE/SE method with first and second –order accuracy has been extended to simulate the multiphase flow in porous medium, which takes into account the contribution of source and sink in the momentum equation. The 3D CE/SE method with the first accuracy has been deduced. The accuracy and efficiency of the proposed CE/SE method have been investigated, using the benchmark problems. (2) The hybrid particle level set method has been made appropriate and extended for capturing the mass interface of multiphase flows in porous media, and the numerical method for level set function calculated has been formulated. (3) The closed equations for multiphase flow in porous medium has been developed, adept to both the Darcy flow and non-Darcy flow, getting over the limitation of Reynolds number to the calculation. It is found that Darcy number has a decisive influence on pressure as well as velocity given the Darcy number. (4) The new Euler scheme for numerical simulations of multiphase flows in porous medium has been proposed, which is efficient and can accurately capture the mass interface. The artificial compressibility method has been used to couple the velocities and pressure. It is found that the Darcy number has determinant effects on the numerical convergence and stability. In terms of the different Darcy numbers, the coefficient of artificial compressibility and the time step have been obtained. (5) The time scale of the critical instability for critical CO2 in the saline aquifer has been found, which is comparable with that of completely CO2 dissolved saline aquifer. (6) The concept model for CO2 multiphase flows in the saline aquifer has been configured, based on the temperature, pressure, porosity as well as permeability of the field site .Numerical simulation of CO2 hydrodynamic trapping in saline aquifers has been performed, applying the proposed CE/SE method. The state for CO2 has been employed to take into account realistic reservoir conditions for CO2 geological sequestration. The geological heterogeneity has been sufficiently treated , using the geostatistical model. (7) It is found that the Rayleigh-Taylor instability phenomenon, which is associated with the penetration of saline fluid into CO2 fluid in the direction of gravity, has been observed in CO2 multiphase flows in the saline aquifer. Development of a mushroom-type spike is a strong indication of the formation of Kelvin-Helmholtz instability due to the developed short wavelength perturbations present along the interface and parallel to the bulk flow. Additional key findings: the geological heterogeneity can distort the flow convection. The ascending of CO2 can induce the persistent flow cycling effects. The results show that boundary conditions of the field site have determinant effects on the transformation and motion of CO2 in saline aquifers. It is confirmed that the proposed method and numerical model has the reliability to simulate the process of the hydrodynamic trapping, which is the controlling mechanism for the initial period of CO2 storage at time scale of 100 years.

鄂尔多斯盆地上古生界包裹体研究及天然气成藏特征分析

Based on the study of types, even temperature, the character of age-old fluid and fluid pressure of the reservoir fluid-inclusion in the Upper Paleozoic of Ordos Basin , combining with the diagenesis and character of gas geochemistry, reservoir sequence, cause of the low pressure reservoir formation and formation environment have been studied, the following knows are acquired: Abundant fluid-conclusions have developed in sandstone reservoir in Upper Paleozoic of Ordos Basin,and its kinds is numerous , also taking place some changes such as shrinking rock, cracking, stretching after formation. According to formation cause, fluid inclusion is divided into two types:successive and nonsuccessive inclusion. Nonsuccessive inclusion is further divided into brine inclusion, containing salt crystal inclusion, gaseity hydrocarbon conclusion and liquid hydrocarbon conclusion and so on. The gaseity hydrocarbon conclusion distributes at all the Basin, the liquid hydrocarbon conclusion mainly distributes at the East of Basin, and its two kinds of fluorescence color: blue and buff reflects at least two periods of oil filling and oil source of the different maturity. The study of diagenesis has indicated that five periods of diagenesis correspond to five periods inclusion's growth.The first and second period conclusions mainly distribute at the increasing margin of quartz, little amount and low even temperature, containing little gaseity hydrocarbon conclusion; The third and fourth conclusions are very rich, and having multiplicity forms, gaseity hydrocarbon conclusion of different facies, distributing at the increasing margin and crevice of quartz, its even temperature is between 85℃and 135℃;The fifth inclusion is relatively few ,mainly distributing at vein quartz and calcite, and developing few gaseity hydrocarbon conclusion. The fluid in the inclusion is mainly NaCl brine:low and high salinity brine fluid(containing salt crystal).The former salinity is between 0.18% and 18.55%,and mainly centralized distributing at three sectongs: from 0% to 4%, from 6% to 8%, from 10% to 14%, expressing that the alternation of the underground fluid was not intense, the conservation condition was good in different periods. The trapping pressure of the gaseity hydrocarbon conclusion calculated by PVTsim(V10)simulation is between 21.39 MPa and 42.58MPa,the average is 28.99MPa,mainlydistributes at between 24 MPa and 34MPa,and having a character of gradually lower from early to late time. The pressure of SuLiGe and WuShenQi dropped quickly in early time, and YuLin, ShenMu-MIZhi gas area dropped slowly in early and quickly in late time, ha portrait the change of trapping pressure can be divided into three old-age pressure systems: TaiYuan-ShanXi formation, low ShiHeZi formation and high ShiHeZi-ShiQianFeng formation. In plane, the trapping pressure dropped lowly from south to north in main reservoir period, and this reflects the gas migrating direction in the geohistory period. The analysis of gas component and monnmer hydrocarbon isotope indicates that the gas in Upper Paleozoic of Ordos Basin is coal-seam gas. The gas C_1-C_4 rnonnmer hydrocarbon isotopes has distinct differences in different stratums of different areas, and forming YuLin, SuLiGe and ShenMu-MIZhi three different distributing types. To sum up, gas reservoir combination in Upper Paleozoic of Ordos Basin can be divided into three sets of combination of reservoir formation: endogenesis type, near source type and farther source type,and near source gas combinations of reservoir formation is the main gas exploration area for its high gas filling intensity, large reservoir size.