Enhanced enzymatic hydrolysis of poplar bark by combined use of gamma ray and dilute acid for bioethanol production

Pretreatment of poplar bark with a combination of sulfuric acid (3%, w/w, H₂SO₄) and gamma irradiation (0–1000 kGy) was performed in an attempt to enhance enzymatic hydrolysis for bioethanol production. The yields of reducing sugar were slightly increased with an increasing irradiation dose, ranging from 35.4% to 51.5%, with a 56.1% reducing sugar yield observed after dilute acid pretreatment. These results clearly showed that soluble sugars were released faster and to a greater extent in dilute acid-pretreated poplar bark than in gamma irradiation-pretreated bark. When combined pretreatment was carried out, a drastic increase in reducing sugar yield (83.1%) was found compared with individual pretreatment, indicating the possibility of increasing the convertibility of poplar bark following combined pretreatment. These findings are likely associated with cellulose crystallinity, lignin modification, and removal of hemicelluloses.     

ChemInform Abstract: Synthesis,Structure, and Electronic Structure of CsAgGa2Se4.

The new title compound is prepared from a mixture of AgGaSe₂ (obtained from the elements at 900 °C, 2 d) and CsI in the molar ratio 1:2 (silica tube, Ar, 800 °C, 48 h).     

Effect of temperature on the morphologies and electrochemical properties of polyaniline-gold fibrillar nanocomposites

The polyaniline-gold (PANI-AuNPs) fibrillar nanocomposites were prepared via a simple one-pot synthesis route in ethylene glycol (EG) medium. The morphology of PANI-AuNPs was characterized by transmission electron microscopy (TEM), and their electrochemical properties were studied by CV, TAF and EIS measurement using an electrochemical workstation. The results show that the morphology of nanocomposites can be controlled by changing the temperature. The diameter of PANI-AuNPs composite nanofiber reduce from about 80 to 30 nm, and the size of AuNP also reduce from about 20 to 4 nm, with the rise of synthesized temperature. When the synthesized temperature is 10°C, the distribution of AuNPs is the best, and the amount of AuNPs dispersed in PANI is the most, as well as the electrochemical performance of PANI-AuNPs is the most excellent.     

High diastereoselective synthesis of spiro-isoxazolonechromans via domino oxa-Michael/1,6-addition reactions of ortho-hydroxyphenylsubstituted para-quinone methides with unsaturated isoxazolones

A mild Et₃N-catalyzed novel domino oxa-Michael/1,6-addition reaction of ortho-hydroxyphenylsubstituted p-QMs and unsaturated isoxazolones is described. Various new spiro-isoxazolonechromans were obtained in good yields (up to 89%) with excellent diastereoselectivities (>99:1 dr). The structure of the new compound 3a was determined by single crystal X-ray analysis.     

Study on phenomenological curing model of epoxy resin for prediction of degree of cure

Curing course of Huntsman 1564/3486 epoxy resin system was studied under dynamic and isothermal curing conditions by differential scanning calorimetry technique. The autocatalytic cure kinetic model was established to describe the curing behaviour. A new modified phenomenological curing model based on the Olivier??s model was proposed to predict the relationship between the degree of cure and the couple of time and temperature. Then, the degree of cure was calculated by both the kinetic model and the modified Olivier??s model. A comparison of the results calculated with the experimental data show that the modified Olivier??s model is more accurate in the later stage of the curing course, especially at high temperatures. The modified Olivier??s model is simple and easy to use, could be applied to predict the degree of cure at isothermal temperatures well in engineering.     

Theoretical studies on electronic structures and spectroscopic properties of a series of novel β-diketonate Os(II) complexes

The geometries, electronic structures, and spectroscopic properties of a series of [Os^(II)(CO)₃(tfa)(acac(X)₂)] (tfa = trifluoroacetate; acac = acetoylacetonate; X = H (1), CF₃ (2), C₆H₅ (3), and C₁₀H₇ (4)) complexes have been investigated theoretically. The ground and excited state geometries were optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. The optimized geometry structural parameters agreed well with the corresponding experimental results. As indicated in this paper, the highest occupied molecular orbitals were dominantly localized on the Os atom, ctfa (abbv. of CO and tfa), and acac ligand for 1 and 2, acac ligand and X substituent for 3 and 4, while the lowest unoccupied molecular orbitals were mainly composed of acac ligand and X substituent. Under the time-dependent density functional theory (TDDFT) level with the polarized continuum model (PCM), the absorption and phosphorescence in CH₂Cl₂ media were calculated based on the optimized ground- and excited-state geometries, respectively. The calculated results show that the lowest energy absorptions at 317 (1), 342 (2), 377 (3), and 420 nm (4) are attributed to a change of ππ*/MLCT mixing transition to pure ππ* transition for 1–4, while their phosphorescence emission have similar transition properties. This indicates that the absorption and emission transition characters could be altered by adjusting the π electron-donating ability.