注入热焓法测定萃取磷酸中三氧化硫

以钡离子与硫酸根离子沉淀反应的热效应为基础，通过测定孤立体系中的温度变化，建立了测定萃取磷酸中三氧化硫的注入热焓法，该法在４．０－３２．０ｇ／Ｌ范围内可准确测定ＳＯ３的含量，相对标准偏差为１．８％；标准加入回收率为９８％－１０３％。     

Spiro-configured bifluorenes: highly efficient emitter for UV organic light-emitting device and host material for red electrophosphorescence

[structure: see text] Remarkable UV OLED devices using novel spiro-configured bifluorenes as UV emitters have been successfully achieved with external quantum efficiencies up to 2.6-3.1% and emission wavelengths as short as 370 nm. In addition, these large-gap materials have been shown to be effective hosts for red phosphorescent emitters in phosphorescent OLEDs. This result represents the first example that pure hydrocarbon molecules can serve as an efficient host for red electrophosphorescence devices.     

A highly regio- and stereoselective nickel-catalyzed ring-opening reaction of alkyl- and allylzirconium reagents to 7-oxabenzonorbornadienes

[Reaction: see text]. An efficient method for the synthesis of cis-2-alkyl- or allyl-1,2-dihydronaphthalenes via a nickel-catalyzed highly regio- and stereoselective ring-opening addition of alkyl- or allylzirconium reagents to 7-oxabenzonorbornadienes is described. Treatment of 7-oxabenzonorbornadienes 1a-c with various alkylzirconium reagents 2a-j (Cp2ZrClCH2CH2R: R = tert-butyl, n-butyl, n-pentyl, -(CH2)3CH=C(CH3)2, -SiMe3, -CH2SiMe3, -(CH2)3Br, cyclopentyl, cyclohexyl, and benzyl) in the presence of NiBr2(dppe) and Zn powder in dry THF at 50 degrees C afforded the corresponding cis-2-alkyl-1,2-dihydronaphthalene derivatives 3a-m in good yields. In addition, allyl zirconium reagents 4a-c also underwent ring-opening reactions with 1a and 1c to give 5a-d in very good yields. The alkylative ring-opening products from 7-oxabenzonorbornadiene can be further converted to naphthalene derivatives 6a-c, via an acid-mediated dehydration, in good to excellent yields. A possible mechanism for the present catalytic reaction was proposed.     

Biosorption of copper(II) and zinc(II) from aqueous solution by Pseudomonas putida CZ1

To study Pseudomonas putida CZ1, having high tolerance to copper and zinc on the removal of toxic metals from aqueous solutions, the biosorption of Cu(II) and Zn(II) by living and nonliving P. putida CZ1 were studied as functions of reaction time, initial pH of the solution and metal concentration. It was found that the optimum pH for Zn(II) removal by living and nonliving cells was 5.0, while it was 5.0 and 4.5, respectively, for Cu(II) removal. At the optimal conditions, metal ion biosorption was increased as the initial metal concentration increased. The adsorption data with respect to both metals provide an excellent fit to the Langmuir isotherm. The binding capacity of living cells is significantly higher than that of nonliving cells at tested conditions. It demonstrated that about 40-50% of the metals were actively taken up by P. putida CZ1, with the remainder being passively bound to the bacterium. Moreover, desorption efficiency of Cu(II) and Zn(II) by living cells was 72.5 and 45.6% under 0.1M HCl and it was 95.3 and 83.8% by nonliving cells, respectively. It may be due to Cu(II) and Zn(II) uptake by the living cells enhanced by intracellular accumulation.     

Lewis acid mediated reactions of aldehydes with styrene derivatives: synthesis of 1,3-dihalo-1,3-diarylpropanes and 3-chloro-1,3-diarylpropanols

[reaction: see text] The reactions of aryl aldehydes with styrene derivatives, mediated by various boron Lewis acids, were investigated. 1,3-Dihalo-1,3-diarylpropanes were obtained in high yields with boron trihalides, while 3-chloro-1,3-diarylpropanols were obtained in good to excellent yields with phenylboron dichloride. Reactions involving nonenolizable aliphatic aldehydes, trans-cinnamaldehyde, and beta-substituted styrenes were also investigated for the first time.     

Electric-field-induced patterns in thin polymer films: weakly nonlinear and fully nonlinear evolution

A thin polymer melt on a substrate can be unstable to an electric field normal to the interface, a phenomenon that can be harnessed as a patterning technique with a range of potential applications. Motivated by the variety of patterns observed in experiments for polymers under both unpatterned and patterned masks, we describe here, from theoretical and numerical analyses, how nonlinear effects govern the growth of the instability and determine the final patterns. In particular, we discuss the nonlinear growth in terms of interactions among different Fourier modes and show that the second- and third-order nonlinearities favor the growth of hexagonal patterns under a featureless mask, in agreement with experimental observations. Also, numerical simulations based on the fully nonlinear model validate the prediction of the weakly nonlinear analysis: hexagonal patterns do emerge under an unpatterned mask. Furthermore, in one-dimensional simulations, we demonstrate the energetic evolution of this patterning process and reveal several "kinetically stable structures" along the path to the thermodynamically stable state. Two-dimensional simulations allow us to study the effects of both mask patterns and the initial film thickness. Generally, patterns on the mask guide the growth such that the pattern conforms to the geometric shapes. Interestingly, a small cylindrical protrusion at the center of the mask can produce exactly the same pattern as a large, flat, circular protrusion. The initial film thickness or the thickness ratio of the polymer layer to the air gap plays an important role in determining the final pattern formed. Finally, we demonstrate, by two simple examples, that the simulations can provide insights on "smart" mask designs for producing large areas of well-ordered patterns.     

Study on the formation of the ketonic defects in the thermal degradation of ladder-type poly(p-phenylenes) by vibrational spectroscopy

We have investigated the thermal degradation in air by Fourier transform infrared spectroscopy of a ladder-type copolymer containing fluorene units in the backbone (Me-LPF), to reveal the formation of the ketonic defects. As thermal treatment of Me-LPF film at 200 degrees C in air proceeds, a new group of complex absorption bands due to degradation products arises in the range between 1800 and 1600 cm(-1). The observed overlapping bands were separated and assigned by utilizing the second-derivative IR spectral analysis, which can narrow the peak width to one-third of the originals and thereby eases the analysis. The degraded products were assigned as fluorenone (1718 cm(-1)) and benzophenone (Ar-(C=O)-Ar) (1665 cm(-1)), formed by the oxidation of the backbone, and acylphenone (Ar-(C=O)-R) (1685 cm(-1)) from the side chain. The fluorenone was found to be the major component among the degraded products in the main chain, and the time and temperature dependence indicated that the oxidation is a kind of autocatalytic radical-chain process. The oxidation can reach a very high degree (approximately 30% for 6 h oxidation at 240 degrees C estimated by absorption of the alkyl). Our results suggest the possibility of the oxidation of the 9-bialkylfluorene sites. We propose that the degradation of the alkyl in the side chain can help the radicals to propagate in the chain reaction.     

Relaxation dynamics of 2,7- and 3,6-distyrylcarbazoles in solutions and in solid films: mechanism for efficient nonradiative deactivation in the 3,6-linked carbazole

We performed time-resolved spectral investigations of two distyrylcarbazole derivatives, 2,7- and 3,6-distyrylcarbazole (2,7-DPVTCz and 3,6-DPVTCz, respectively), in dilute toluene solution and in solid films mixed with poly(methyl methacrylate) (PMMA). The lifetime of 2,7-DPVTCz in its excited state in solution is approximately 100 times as great as that of 3,6-DPVTCz, consistent with their photophysical nature. The former shows intense emission, but the latter is nearly nonfluorescent in a free environment. Moreover, the lifetime of 3,6-DPVTCz in its excited state increased also approximately 100 times when the molecule was encapsulated in a 3,6-DPVTCz/PMMA solid film, indicating that intramolecular motion of the molecule significantly affects the observed relaxation dynamics in a confined environment. Calculations on the excited states indicate that an efficient intersystem crossing is activated upon twisting of the bridged C-C single bond in a free 3,6-linked carbazole; such efficient deactivation is impractical in 2,7-linked carbazole or for 3,6-linked carbazole in a PMMA matrix. Information obtained from experiments on femtosecond fluorescence enables us to distinguish crucial relaxation processes in the excited state for a profound understanding of the details of vibrational and electronic relaxations of 3,6-DPVTCz in solution.     

Cluster size effects on CO oxidation activity, adsorbate affinity, and temporal behavior of model Au(n)/TiO2 catalysts

Model catalysts were prepared by deposition of size-selected Au(n) (n = 1-7) on rutile TiO2(110), and characterized by a combination of electron spectroscopy, ion scattering, temperature-programmed desorption, and pulse-dosing mass spectrometry. CO oxidation activity was found to vary strongly with deposited cluster size, with significant activity appearing at Au3. Activity is not obviously correlated with affinity for CO, or with cluster morphology, but is strongly correlated with the clusters' ability to bind oxygen (during O2 exposure) on top of the gold. The temporal dependence of CO2 evolution in reaction of O2 pre-exposed samples with CO pulses shows an interesting cluster size dependence. For Au5 and Au6, the peak CO2 production is coincident with the peak CO flux, but for Au3, Au4, and Au7, there are significant induction periods for CO2 evolution. In addition, it is observed that some of the most active cluster sizes have the slowest CO2 evolution rates. Several mechanistic scenarios capable of accounting for the observations are laid out.     

Novel approach to synthesizing hydrophobically associating copolymer using template copolymerization: the synthesis and behaviors of acrylamide and 4-(omega-propenoyloxyethoxy) benzoic acid copolymer

Hydrophobically associating copolymers of acrylamide (AM) with a small amount of 4-(omega-propenoyloxyethoxy) benzoic acid (PEBA, <2.5%) were synthesized by template copolymerization in the presence of poly(allylammonium chloride) (PAAC) as a template in an aqueous medium. These template copolymers exhibited remarkable thickening properties due to the effective hydrophobic association, which were similar to those copolymers with a multiblock structure obtained by the micellar process. The pH of the reaction medium and the molecular weight of the template strongly influenced the thickening properties of the products. In the experimental range, the higher the PEBA content, the larger the thickening capacity of these hydrophobic copolymers. The aggregate behaviors of these copolymers were studied by fluorescence, transmission electron microscopy (TEM), and light scattering techniques. The apparent critical interpolymer aggregate concentration (cac) of the copolymer solution was about 0.5 g/dL. As the concentration of the copolymer became higher than the cac, the aggregates changed their morphology from small hollow spheres to big flower-shaped aggregates. All the above results indicated that the template copolymerization gave access to a very simple and powerful means for the preparation of hydrophobically associating copolymers and other functional polymer materials.