Photo-Induced Switching of CO2 Hydrogenation Pathway towards CH3OH Production over Pt@UiO-66-NH2(Co)

It is highly desired to achieve controllable product selectivity in CO₂ hydrogenation. Herein, we report light-induced switching of reaction pathways of CO₂ hydrogenation towards CH₃OH production over actomically dispersed Co decorated Pt@UiO-66-NH₂. CO, being the main product in the reverse water gas shift (RWGS) pathway under thermocatalysis condition, is switched to CH₃OH via the formate pathway with the assistance of light irradiation. Impressively, the space-time yield of CH₃OH in photo-assisted thermocatalysis (1916.3 μmol g_cat⁻¹ h⁻¹) is about 7.8 times higher than that without light at 240 °C and 1.5 MPa. Mechanism investigation indicates that upon light irradiation, excited UiO-66-NH₂ can transfer electrons to Pt nanoparticles and Co sites, which can efficiently catalyze the critical elementary steps (i.e., CO₂-to-*HCOO conversion), thus suppressing the RWGS pathway to achieve a high CH₃OH selectivity.     

Effect of Manganese on Radiation Vulcanization of Natural Rubber

Manganese was added as a promoter to investigate physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films. RVNRL films were prepared by the addition of Mn with the concentration range 0–30 ppm to natural rubber latex and irradiated with various radiation doses (0–20 kGy). Tensile strength, tear strength, and cross-linking density of the irradiated rubber films increased with increasing the concentration of Mn ions as well as radiation doses. In contrast, elongation at break, permanent set, and swelling ratio of the films were decreased under the same conditions. The concentration of Mn ions and radiation doses were optimized and found to be 20 ppm and 12 kGy, respectively. The maximum tensile and tear strengths of irradiated rubber films were observed as 29.12 MPa and 44.78 N/mm, respectively at the optimum conditions. The mechanical properties of the films increased markedly with the addition of Mn until they attained the highest values of 33.88 MPa and 54.77 N/mm, respectively. These enhancements, which reached approximately 20% at the most favorable conditions, can be explained by the effect of transition metals in view of Fajan’s rules regarding the covalent character of ionic bonds and suggest that the higher the difference in charges between cation and anion, the higher the ability to form distortion or polarization of ions.     

Synthesis and Polymerization of N-(L-Menthylcarboxylatomethyl)maleimide

A new type of optically active N-(L-menthylcarboxylatomethyl)maleimide (MGMI) was synthesized from maleic anhydride, glycine, and L-menthol. Radical homopolymerization of MGMI was performed at 50°C for 24 h to give optically active polymer having [α]_D = -57°. Radical copolymerizations of MGMI (M ₁) were performed with styrene (ST, M ₂), methyl methacrylate (MMA, M ₂) in benzene at 50°C. From the results, the monomer reactivity ratios (r ₁, r ₂) and the Alfrey-Price Q, e values were determined as follows: r ₁ = 0.16, r ₂ = 0.006 for the MGMI-ST system; r ₁ = 0.15, r ₂ = 1.65 for the MGMI-MMA system, and Q ₁ = 0.72, e ₁ = 1.59 calculated from the MGMI-MMA system. Anionic homopolymerizations of MGMI were also carried out. Chiroptical properties of the polymers were investigated.     

Old Reagent,New Results: Aromatization of Hantzsch 1,4-Dihydropyridines with Supported Bismuth Nitrate under Microwave Irradiation in Solventless System

Hantzsch 1,4-dihydropyriines were rapidly and efficiently oxidized using bismuth nitrate supported onto silica gel under microwave irradiation.     

Radiation damage by soft β-particles self-irradiation of β-tritiated polystyrene

The effect of self-irradiation of β-tritiated polystyrene under high vacuum at 25°C was studied, and simultaneous random chain scission and cross-linking were observed. Analyses of the gaseous products and the colored polymer residue showed that hydrogen was the only volatile product, while spectroscopic measurements indicated that the coloration was associated with the presence of main-chain double bonds.

G values for hydrogen formation GH₂, cross-linking, G _XL and chain scission, G _CS were obtained as follows: GH₂=0.031; G _CS=0.044; G _XL=0.061. Possible mechanisms of radiation damage are discussed.     

Study of size dependent features of swift heavy ion irradiation in nanosized zinc ferrite

In the present work zinc ferrite nanoparticles of different crystallite size were irradiated with 200 MeV Ag¹⁵⁺ ion beam. The structural and magnetic characterization performed for these samples indicate the presence of size dependent irradiation induced changes in the nanoparticles. The superparamgnetic nanoparticles do not alter their behavior after irradiation; however paramagnetic samples exhibit weak ferrimagnetism in the irradiated specimen. Results obtained from these measurements are in agreement with results obtained from the electron paramagnetic resonance spectroscopy.     

γ辐照引发[Cnmim][NTf2]离子液体变色研究

1-烷基-3-甲基咪唑双三氟甲基磺酰胺型离子液体(C_nmim][NTf₂])被认为是最有希望用于核燃料循环中的分离试剂之一, 虽然其化学结构在辐照过程中变化不大, 但在受到γ辐照后会发生明显的变色, 因此有必要研究该类离子液体的变色原因. 本文以⁶⁰Co为辐照源, 系统研究了辐照后不同C(1)－烷基链长和咪唑环上C(2)位上的H被甲基取代后离子液体的紫外-可见(UV-Vis)吸收光谱行为, 并结合辐照后离子液体荧光光谱和质谱的变化, 分析了导致该类离子液体辐照后颜色加深的原因. 结果表明, 随着咪唑环上C(1)―烷基链长度和剂量增大, 离子液体颜色加深; 而C(2)位上的H被甲基取代后颜色明显变浅. 辐照后咪唑型离子液体的变色主要来自于辐照后产生的烷基侧链含双键的咪唑阳离子, 咪唑阳离子二聚体和含氟咪唑化合物. 此外, γ辐照引起咪唑阳离子易发生π-π堆积, 而聚集态含量增加也会引起颜色加深.     

High-resolution transmission electron microscopy study on reversion of Al2CuMg precipitates in Al–Cu–Mg alloys under irradiation

Image deconvolution analyses showed that reversion of S-Al₂CuMg precipitates occurred in an Al–Cu–Mg alloy during high-resolution transmission electron microscopy observations. A fraction of Mg and Cu atoms in the precipitates diffused into Al matrix due to electron beam irradiation at 300 kV, resulting in structural/chemical reversion of the precipitates. The structural reversion of the S-Al₂CuMg precipitates is closely related with irradiation-induced displacement of atoms. The strong attraction between Cu and Mg atoms might assist the sub-threshold displacement of Cu atoms. One transitional structure is determined to be S′′-Al₁₀Cu₃Mg₃, a precursor of S-Al₂CuMg. Two other transitional structures, Al₃CuMg and Al₁₈Cu₅Mg₅ which have the same lattice parameters of a = c = 0.405 nm as that of S′′-Al₁₀Cu₃Mg₃, but different b values, are suggested.     

Evaluation of radiation damage behavior in polyimide aerogel by infrared camera and photoacoustic spectroscopy

In this work, the optical absorption and thermal properties of polyimide aerogel have been investigated by Infrared Camera, ultraviolet–visible and photoacoustic spectroscopy under low energy proton irradiation. The characterization method of the infrared camera can obtain the optical absorption ratio, and meanwhile get the information of specific heat capacity. Moreover, it can acquire the nature information of damaged area rather than the overall performance. The results show an increase in optical absorption after proton irradiation, which is in good coincidence with Ultraviolet–visible spectroscopy analysis. And the specific heat capacity decreased linearly with proton fluences, which can be attributed to the irradiation damage and carbonization in polyimide aerogel. The Raman spectra suggested the cleavage of chemical bonds and carbonization in polyimide aerogel. This work provides the novel, non-destructive and sensitive methods to characterize irradiation damage of aerogel.     

傅里叶变换红外光谱法研究核辐照对三七总皂苷粉成分的影响

采用傅里叶变换红外光谱(卷积谱)法对经不同剂量y-射线核辐照的三七总皂苷粉进行了对比研究.辐照剂量不高于9kGy时,三七总皂苷粉样品的化学成分几乎没有发生变化;三七总皂苷粉样品经15kGy及以上的辐照剂量辐照后,可能产生新的化学成分;经21kGy的剂量辐照,三七总皂苷粉产生了人参、三七粉所含的普通成分(非三七总皂苷成分...