查找使用阿拉丁产品的科研文献

Dielectric strength of glass fibre fabric reinforced epoxy by nano-Al2O3

Shuang Wang,Yu Chen,Jiale Mao,Cong Liu,Lei Zhang,Yonghong Cheng,Chaoyun Du,Toshikatsu Tanaka

3, 3′-Diaminobenzidine with dual o-phenylenediamine groups: two in one enables visual colorimetric detection of nitric oxide

Yu Haili,Dong Faqin,Chen Jiahui,Li Bowen

Nitric oxide (NO) plays an important role in the generation of smog and ozone. Although great efforts have been made to determine NO by using o-phenylenediamine (OPD)-based fluorescent probes, more simple and reliable colorimetric assays for detection of NO are extremely scarce because a single OPD structure cannot produce enough optical absorption for chromogenesis. In this study, we report an innovative two-in-one visual colorimetric methodology. Commercially available 3,3′-diaminobenzidine (DAB) with two OPD structures in a single molecule is selected as the colorimetric probe, and it reacts with NO via diazo-coupling reaction to generate 1H,3’H-[5,5′]bibenzotriazolyl because of the increase of conjugated double bonds, accompanying a distinct color change from colorless to brownish yellow. This two-in-one colorimetric assay can determine NO at a concentration as low as 3 ppm by the naked eye and 40 ppb by UV-vis spectrometry, which is the lowest limit of detection (LOD) among reported colorimetric assays for NO. Moreover, the present two-in-one visual colorimetric assay also has good selectivity toward NO over other common potential gas interferents such as CO 2 , NO 2 , NH 3 , N 2 , O 2 , and SO 2 . This present study provides a new insight for the design and development of assays for NO. Graphical abstract

Characterization of a caffeoyl-CoA O-methyltransferase-like enzyme involved in biosynthesis of polymethoxylated flavones in Citrus reticulata

Liu Xiaojuan,Zhao Chenning,Gong Qin,Wang Yue,Cao Jinping,Li Xian,Grierson Donald,Sun Chongde

Polymethoxylated flavones (PMFs), which accumulate exclusively in fruit peel of citrus, play important physiological and pharmacological roles but the genetic basis for the methylation of flavonoids has not been fully elucidated in citrus. Here we characterize a caffeoyl-CoA O-methyltransferase-like enzyme, designated CrOMT1. The expression pattern of CrOMT1 was highly correlated with the concentration of the three major PMFs in two different citrus fruit tissues during fruit maturation. Exposure of fruit to UV-B radiation sharply increased the level of CrOMT1 transcripts and also led to the accumulation of three PMFs. The potential role of CrOMT1 was studied by testing the catalytic activity of recombinant CrOMT1 with numerous possible substrates in vitro. The enzyme could most efficiently methylate flavones with neighboring hydroxy moieties, with high catalytic efficiencies found with 6-OH- and 8-OH-containing compounds, preferences that correspond precisely with the essential methylation sites involved in the synthesis of the three naturally occurring PMFs in Citrus reticulata. This indicates that CrOMT1 is capable of in vitro methylation reactions required to synthesize PMFs in vivo. Furthermore, transient overexpression of CrOMT1 increased levels of the three major PMFs in fruit, indicating that CrOMT1 is likely to play an essential role in the biosynthesis of PMFs in citrus.

Surface adsorption configurations of H3PO4 modified TiO2 and its influence on the photodegradation intermediates of gaseous o-xylene

Zhuang Wang,Asad Mahmood,Xiaofeng Xie,Xiao Wang,Hanxun Qiu,Jing Sun

For the oxide-based photocatalysts, polyoxylic acid modification can affect their adsorption/desorption properties and further regulate photocatalytic reaction pathway, which is crucial for enhancing photocatalytic activity and selectivity. Herein, phosphoric acid modified TiO 2 was synthesized by a facile impregnation-calcination method for photocatalytic degradation of gaseous o-xylene. According to FTIR, XPS, and EDS analysis, phosphoric acid was anchored on the surface of TiO 2 successfully. The surface P atomic percentages for PT1 was 2.45%. The as-prepared phosphoric acid modified TiO 2 (PTx) had a photocatalytic performance superior to that of commercial TiO 2 and unmodified TiO 2 (PT0), with increasing by 2.2 times at most. Interestingly, the phosphoric acid molecules strongly adsorbed on anatase TiO 2 surface by forming H–O 2C and =O–Ti 5C chemical bonds according to the first principle calculations, which changed TiO 2 surface properties (specific surface area and surface negative electrostatic field) and further improved adsorption and charge carrier separation and transfer, thus improving the photocatalytic activity. Additionally, according to the intermediates results, the relative abundance of intermediates shows obvious difference. Acetone was detected as the most abundant intermediates during o-xylene degradation for PT0, whereas that was o-methyl benzaldehyde for PT1, which could be ascribed to the difference of surface adsorption configuration of o-xylene. According to the temperature-programmed desorption (TPD) results, the surface modified by phosphoric acid could change the o-xylene adsorption configuration to favor its methyl oxidation (standing configuration), whereas the unmodified surface could be more favorable to the benzene ring-open reaction (lying configuration). This work will deepen the understanding of the relevance of surface modification and surface photocatalytic reaction, which also provides a feasible strategy to improve photocatalytic selectivity.

Effect of Reduction Atmosphere on Structure and Catalytic Performance of PtIn/Mg(Al)O/ZnO for Propane Dehydrogenation

Ming Zhang,Zhen Song,Mengquan Guo,Xiangxiang Li,Yanjun Lin,Lihong Zhang

The effect of reduction atmospheres, H2/N2, C3H8/H2/N2, C3H8and CO, on the structure and propane direct dehydrogenation performance of PtIn/Mg(Al)O/ZnO catalyst derived from ZnO-supported PtIn-hydrotalcite was studied. The physicochemical properties of the as-prepared and used catalytic system were characterized by various characterization methods. The results show that the dehydrogenation performance, especially the stability of the PtIn/Mg(Al)O/ZnO catalyst, was significantly improved along with the change in reduction atmosphere. The highest catalytic activity (51% of propane conversion and 97% propylene selectivity), resistance toward coke deposition, and stability for more than 30 h were achieved with the H2/N2-reduced catalyst. The optimal dehydrogenation performance and coke resistance are mainly related to the high Pt dispersion and In0/In3+molar ratio, strong Pt–In interaction and small metal particle size, depending on the nature of the reduction atmospheres. The reconstruction of meixnerite favors the stability and coke resistance to some extent.Keywords:propane dehydrogenation;reduction atmosphere;coke deposition;meixnerite;PtIn/Mg(Al)O/ZnO

Preparation of W1/O/W2 emulsion to limit the diffusion of Fe3+ in the Fricke gel 3D dosimeter

Wei Zhang,Kaikai Wang,Xiaodan Hu,Xiaohong Zhang,Shuquan Chang,Haiqian Zhang

The irradiation of tumors in radiotherapy requires accurate 3D dosimetry. The Fricke 3D dosimeters, which were considered to be high potential of application in 3D dosimetry, suffer from a reduced temporal integrity of dose distribution caused by Fe 3+ ions diffusion. To overcome the drawback, we firstly synthesized a kind of amphiphilic molecules with critical micelle concentration of 0.45 g/L and hydrophile-lipophile balance value of 10, then prepared multiple emulsions by self-assembling those molecules in Fricke solution under liquid paraffin, and finally obtained Fricke hydrogel embedded with the multiple emulsions. The diffusion coefficient of Fe 3+ ions in the embedded Fricke hydrogel was measured to be 0.17 mm 2 /h. The hydrogel dosimeter exhibits considerable potential for use in dose verification applications.

A ascorbic acid-imprinted poly(o-phenylenediamine)/zeolite imidazole frameworks-67/carbon cloth for electrochemical sensing ascorbic acid

Guo Yufei,Wang Li,Xu Lijuan,Peng Canwei,Song Yonghai

A flexible ascorbic acid (AA)-imprinted poly(o-phenylenediamine) (ploy(o-PD))/zeolite imidazole frameworks-67 (ZIF-67)/carbon cloth (CC) electrode was prepared for electrochemical sensing AA. The flexible AA-imprinted poly(o-PD)/ZIF-67/CC electrode was prepared by growing ZIF-67 on flexible CC, electropolymerization of o-PD with AA on ZIF-67/CC and eluting template molecules AA. The results showed that the spherical ZIF-67 crystals were arranged evenly and firmly on the fibers of CC surface. The diameter of spherical ZIF-67 crystals was approximately 500–600 nm, and the spherical ZIF-67 crystals catalyzed the oxidation of AA well. A layer of poly(o-PD) with AA-imprinted pores was covered on the ZIF-67/CC electrode, so the AA-imprinted poly(o-PD)/ZIF-67/CC electrode exhibited better selectivity toward AA detection and good stability. The molecularly imprinted sensor exhibits high sensitivity, and the sensitivity could reach 959.9 μA/mM −1  cm −2 , the detection limit was 0.019 μM, and the concentration range of AA was 0.057 μM–11.4 0 mM. The AA-imprinted poly(o-PD)/ZIF-67/CC electrode also showed higher stability and repeatability. The results proved that the spherical ZIF-67 crystals were good electrode materials for electrochemical AA biosensors.

Analysis of the binding mechanism between o-phenylenediamine and bovine hemoglobin by molecular spectroscopy and molecular modeling methods

Jian-Li Liu,Yu-Chi Kong,Jing-Yi Miao,Yong-Lin He,Ruo-Chen Bi,Yin He,Xiang-Yu Cao

This study was aimed to reveal the binding mechanism between bovine hemoglobin and o-phenylenediamine by using molecular spectroscopy techniques and molecular modeling methods. The experimental results revealed that the fluorescence quenching mechanism was a combined dynamic and static quenching. The binding constant was (1.17 ± 0.02)×104 L/mol, and only a single binding site exists. The binding distance was 2.46 nm. The binding process was a spontaneous reaction, dominated by hydrophobic forces. The molecular docking simulations have also confirmed the results of the spectroscopic methods. The results reported here may significantly help understanding the interaction mechanism of o-phenylenediamine and hemoglobin.

Synthesis of (Sn,Zn)(O,S) bimetallic oxysulfide catalyst for the detoxification of Cr+6 in aqueous solution

Osman Ahmed Zelekew,Dong-Hau Kuo,Hairus Abdullah

Herein, we report the bimetallic (Sn,Zn)(O,S) oxysulfide nanocatalyst with a facile method. The Sn-based catalyst with the addition of Zn was synthesized with the proportions of 0, 20, 30 and 50% of Zn to Sn precursors for preparation. The catalysts were characterized by XRD , TEM , SEM XPS , and UV–vis instruments. The nanocatalysts were also tested for the detoxification of Cr +6 . The Sn-20 catalyst with 20 M percent of Zn(Ac) 2 ·2H 2 O showed an excellent performance for the induced photocatalytic reduction of Cr +6 under visible light irradiation at room temperature. The complete reduction of Cr +6 was achieved within 80 min by Sn-20 catalyst. However, 85.6, 97, and 94% of Cr +6 reductions were achieved within 80 min under visible light illumination by Sn-0, Sn-30, and Sn-50 catalysts, respectively. Hence, the bimetallic (Sn,Zn)(O,S) oxysulfide nanocatalyst will be a candidate and highly potential material for the detoxification of Cr(VI)-containing polluted water.

C–O Bond Activation in Mononuclear Lanthanide Oxocarbonyl Complexes OLn(η2-CO) (Ln = La, Ce, Pr, and Nd)

Zhen Pu,Jianwei Qin,Xiaoguo Fu,Ruizhi Qiu,Bin Su,Maobing Shuai,Fang Li

Fundamental investigation of metal–CO interactions is of great importance for the development of high-performance catalysts to CO activation. Herein, a series of side-on bonded mononuclear lanthanide (Ln) oxocarbonyl complexes OLn(η2-CO) (Ln = La, Ce, Pr, and Nd) have been prepared and identified in solid argon matrices. The complexes exhibit uncommonly low C–O stretching bands near 1630 cm–1, indicating remarkable C–O bond activation in these Ln analogues. The η2-CO ligand in OLn(η2-CO) can be claimed as an anion on the basis of the experimental observations and quantum chemistry investigations, although the CO anion is commonly considered to be unstable with electron auto-detachment. The CO activation in OLn(η2-CO) is attributed to the photoinduced intramolecular charge transfer from LnO to CO rather than the generally accepted metal → CO π back-donation, which conforms to the traditional Dewar–Chatt–Duncanson motif. Energy decomposition analysis combined with natural orbitals for chemical valence calculations demonstrates that the bonding between LnO and η2-CO arises from the combination of dominant ionic forces (>76%) and normal Lewis “acid–base” interactions. The fundamental findings provide guidelines for the catalyst design of CO activation.

Correlation of o-Ps annihilation properties with catalytic activities of palladium species immobilized on functionalized MCM-41 supports

Baogang Su,Hui Pan,Linbo Li,Linjun Shao,Chenze Qi,Shujing Zhou,Jinjing Li

Design and preparation of highly active and stable supported palladium catalysts have garnered increased attention for their easy separation and reusability. Herein, MCM-41 mesoporous materials functionalized by four different amino functional groups were synthesized by using four commercially available siloxanes and then used to support palladium catalysts. The Fourier transform infrared spectroscopy (FT-IR) was used to analyze the chemical structures of functionalized MCM-41 supports. The thermogravimetric analysis (TGA) and element analysis (EA) were employed to determine the grafting densities of functional groups on MCM-41 supports. The mesoporous structures of functionalized MCM-41 supports and dispersion of palladium species were characterized by high resolution transmission electron microscopy (TEM) and X-ray diffraction patterns (XRD). A study of the materials using positron annihilation lifetime spectroscopy (PALS) reveals the different ortho-positronium ( o -Ps) annihilation properties of the supported palladium species on the four supports. Meanwhile, the catalytic activities of supported palladium species on the four supports were evaluated by the Heck reactions of iodobenzene with n-butyl acrylate. At last, the annihilation properties of the supported palladium species on the four supports were successfully correlated with their catalytic activities. The result suggests a facile method to determine and predict the catalytic activities of supported palladium species by using PALS, which may hold great potential in the preparation of rationally designed and highly active supported palladium catalysts.

α-ketoglutarate ameliorates spinal motor neuron ferroptosis after sacral plexus transection via enhancing PINK1 O‑GlcNAcylation and mitophagy

Hui Han,Sheng Wang,Jiajia Lu,Jing Li,Jinlong Zheng,Yongchuan Li,Hongtao Lu,Aimin Chen

Sacral plexus transection (SPT), mostly caused by high‑energy trauma, induces secondary death of spinal motor neurons in the lumbosacral segments and contributes to poor clinical outcomes after nerve repair. This study aimed to investigate the protective effect of α‑ketoglutarate (AKG) against ferroptosis in spinal motor neurons following SPT and the underlying molecular mechanism. Our results showed that endogenous AKG levels were significantly decreased in the spinal cord of SPT rats and in oxidative stress‑injured motor neurons, accompanied by abnormal expression of core ferroptosis‑related proteins, including downregulated glutathione peroxidase 4 and solute carrier family 7 member 11, upregulated acyl-CoA synthetase long-chain family member 4, as well as Fe2+ overload, malondialdehyde accumulation, and glutathione depletion. Exogenous AKG supplementation markedly reversed these anomalies, suppressed ferroptosis, and improved neuronal survival. Mechanistically, AKG specifically enhanced O-GlcNAcylation at the Thr177 site of PTEN‑induced kinase 1 (PINK1) and suppressed its ubiquitin-mediated degradation, which in turn selectively activated PINK1-PRKN-dependent mitophagy to eliminate damaged mitochondria and sustain mitochondrial homeostasis. Furthermore, downregulation of isocitrate dehydrogenase 1 (IDH1) after SPT was identified as a critical upstream event leading to endogenous AKG depletion. This study systematically elucidates the key role of the IDH1‑AKG‑PINK1 O‑GlcNAcylation ‑mitophagy axis in regulating SPT‑induced ferroptosis in spinal motor neurons, providing novel targets and experimental evidence for neuroprotective therapy of sacral plexus injury.