Energy‐resolved electron‐yield XAS studies of nanoporous CoAlPO‐18 and CoAlPO‐34 catalysts

Energy‐resolved electron‐yield X‐ray absorption spectroscopy is a promising technique for probing the near‐surface structure of nanomaterials because of its ability to discriminate between the near‐surface and bulk of materials. So far, the technique has only been used in model systems. Here, the local structural characterization of nanoporous cobalt‐substituted aluminophosphates is reported and it is shown that the technique can be employed for the study of open‐framework catalytically active systems. Evidence that the cobalt ions on the surface of the crystals react differently to those in the bulk is found.     

Preprocessed barley,rye, and triticale as a feedstock for an integrated fuel ethanol-feedlot plant

Rye, triticale, and barley were evaluated as starch feedstock to replace wheat for ethanol production. Preprocessing of grain by abrasion on a Satake mill reduced fiber and increased starch concentrations in feedstock for fermentations. Higher concentrations of starch in flours from preprocessed cereal grains would increase plant throughput by 8–23% since more starch is processed in the same weight of feedstock. Increased concentrations of starch for fermentation resulted in higher concentrations of ethanol in beer. Energy requirements to produce one L of ethanol from preprocessed grains were reduced, the natural gas by 3.5–11.4%, whereas power consumption was reduced by 5.2–15.6%.     

Complex dynamics of a chemostat with variable yield and periodically impulsive perturbation on the substrate

In this paper, we consider the dynamic behaviors of a mathematical chemostat model with variable yield and periodically impulsive perturbation on the substrate. The microbial growth rate is the Monod function and the variable yield coefficient δ(S) is quadratic (1 + cS ²). Using Floquet theory and small amplitude perturbation method, we establish the condition under which the boundary periodic solution is globally asymptotically stable. Moreover, the permanence of the system is discussed in detail. Finally, by means of numerical simulation, we demonstrate that with the increasing of the pulsed substrate in the feed the system exhibits the complex dynamics.      

IM-5分子筛在Ni-Cu催化剂甲烷热裂解制氢反应中的作用研究

甲烷热裂解制氢并生成高附加值的纳米碳材料,被认为是极具发展前景的氢气生产途径,但高性能催化剂的研发仍存在诸多挑战.我们选择多种载体(TS-1、 IM-5、 Y、介孔SiO₂、 γ-Al₂O₃、 CNTs),采用浸渍法制备Ni-Cu负载催化剂,通过低温N2吸附-脱附、 XRD、 SEM和H₂-TPR等系列表征方法对样品进行分析,考察不同载体对催化剂甲烷裂解制氢和纳米碳材料的影响.实验结果发现,分子筛载体独特的孔道结构有利于金属颗粒的分散,能有效避免反应中界面效应导致的催化剂失活,可提高催化剂反应活性并延长反应寿命,也显著提高了其碳产率.其中以IM-5分子筛为载体的催化剂表现最佳,在反应温度为700℃时, NiCu/IM-5催化剂甲烷转化率高达80%,氢气选择性达100%,反应400 min后活性未见明显降低. NiCu/IM-5催化剂碳产率高达1 446 g_C/g_cat,是NiCu/SiO₂催化剂的5.7倍, NiCu/γ-Al     

Chalcogen Effect of Atom Substitution on the Properties of Tris(2,4,6-trichlorophenyl)methyl(TTM) Radical

Luminescent open-shell organic radicals have recently been regarded as one of the most potential materials in organic light-emitting diodes(OLEDs). Herein, we have synthesized two new organic radicals, namely tris{4-[4-(tert-butyl)phenoxy]-2,6- dichlorophenyl}methane radical(TTM-O) and tris(4-{[4-(tert-butyl)- phenyl]thio}-2,6-dichlorophenyl)methane radical(TTM-S), by the substitution of chalcogen atom elements at the para position of conventional tris(2,4,6-trichlorophenyl)methyl(TTM) radical moiety. Interestingly, both TTM-O and TTM-S exhibited significantly enhanced photostability compared with the unsubstituted TTM radical parent. Moreover, the chalcogen atom also had a crucial impact on the photoluminescence quantum yield(PLQY) of the radicals, i.e., the PLQY of TTM-S was greatly enhanced compared to TTM radical while TTM-O was nearly non-emissive. Particularly, TTM-S showed intense PLQY of 37.54% and 185-fold longer photostability than that in cyclohexane solution of TTM.     

Syntheses of octasubstituted zinc azaphthalocyanines with thiophene or thiophene combined with sulfanyl,amino or imido substituents: Influence of the substituents on photochemical and photophysical properties

Several octasubstituted zinc azaphthalocyanines (ZnAzaPcs) of the tetrapyrazinoporphyrazine type have been synthesized as potential sensitizers for photodynamic therapy (PDT). Octasubstituted complexes, with thiophen-2-yl, thiophen-3-yl or benzo[b]thiophen-3-yl peripheral groups, were synthesized and characterized. Octa(thiophen-2-yl) ZnAzaPc is a better singlet oxygen producer and has a red shifted UV absorption Q-band compared to both thiophen-3-yl and benzo[b]thiophen-3-yl substituted ZnAzaPcs. Thus, the thiophen-2-yl substituent is better suited for our purpose. Unsymmetrically substituted ZnAzaPcs were synthesized by cyclotetramerisations of pyrazine-2,3-dicarbonitriles attached to one thiophen-2-yl group and one alkylsulfanyl, thiomorpholinyl or imide group. Constitutional isomers were detected by NMR spectroscopy for some of these complexes. Compared to unsubstituted ZnAzaPc, red shifted Q-bands were observed for all these complexes, due to the presence of thiophen-2-yl groups. The least promising complexes are ZnAzaPcs with thiomorpholine or imide peripheral substituents, i.e. where the peripheral substituents are attached to the macrocycle through nitrogen atoms. Low singlet oxygen quantum yields (Φ_Δ) and also low fluorescence quantum yields (Φ_F) were observed for these ZnAzaPcs. In the case of combined thiophen-2-yl and alkylsulfanyl substituents, the values of Φ_Δ were the highest and reached values of approximately 0.69.     

Influence of quantum dot's quantum yield to chemiluminescent resonance energy transfer

The resonance energy transfer between chemiluminescence donor (luminol-H₂O₂ system) and quantum dots (QDs, emission at 593 nm) acceptors (CRET) was investigated. The resonance energy transfer efficiencies were compared while the oil soluble QDs, water soluble QDs (modified with thioglycolate) and QD-HRP conjugates were used as acceptor. The fluorescence of QD can be observed in the three cases, indicating that the CRET occurs while QD acceptor in different status was used. The highest CRET efficiency (10.7%) was obtained in the case of oil soluble QDs, and the lowest CRET efficiency (2.7%) was observed in the QD-HRP conjugates case. This result is coincident with the quantum yields of the acceptors (18.3% and 0.4%). The same result was observed in another similar set of experiment, in which the amphiphilic polymer modified QDs (emission at 675 nm) were used. It suggests that the quantum yield of the QD in different status is the crucial factor to the CRET efficiency. Furthermore, the multiplexed CRET between luminol donor and three different sizes QD acceptors was observed simultaneously. This work will offer useful support for improving the CRET studies based on quantum dots.