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排序方式: 共有6175条查询结果,搜索用时 46 毫秒
61.
Gustavo Pereira Saito Ana Carolina Lanfredi Matsumoto Renata Pires Assis Iguatemy Loureno Brunetti Marco Aurlio Cebim Marian Rosaly Davolos 《Molecules (Basel, Switzerland)》2021,26(8)
Excessive UV solar radiation exposure causes human health risks; therefore, the study of multifunctional filters is important to skin UV protective ability and also to other beneficial activities to the human organism, such as reduction of reactive oxygen species (ROS) responsible for cellular damages. Potential multifunctional filters were obtained by intercalating of ferulate anions into layered simple metal hydroxides (LSH) through anion exchange and precipitation at constant pH methods. Ultrasound treatment was used in order to investigate the structural changes in LSH-ferulate materials. Structural and spectroscopic analyses show the formation of layered materials composed by a mixture of LSH intercalated with ferulate anions, where carboxylate groups of ferulate species interact with LSH layers. UV-VIS absorption spectra and in vitro SPF measurements indicate that LSH-ferulate systems have UV shielding capacity, mainly UVB protection. The results of reactive species assays show the ability of layered compounds in capture DPPH•, ABTS•+, ROO•, and HOCl/OCl− reactive species. LSH-ferulate materials exhibit antioxidant activity and singular optical properties that enable their use as multifunctional filters. 相似文献
62.
Muhammad Asif Ayesha Aziz Anh Quang Dao Abdul Hakeem Haitao Wang Shuang Dong Guoan Zhang Fei Xiao Hongfang Liu 《Analytica chimica acta》2015
We report a facile and green method for the fabrication of new type of electrocatalysts based on MnO2 nanoparticles incorporated on MgAl LDH P-type semiconductive channel and explore its practical applications as high-performance electrode materials for electrochemical biosensor. A series of MgAl layered doubled hydroxide (LDH) nanohybrids with fixed Mg/Al (M2+/M3+ atomic ratio of 3) and varied amount of MnCl2.4H2O are fabricated by a facile co-precipitation method. This approach demonstrates the combination of distinct properties including excellent intercalation features of LDH for entrapping nanoparticles and high loading of MnO2 nanoparticles in the host layers of LDH. Among all samples, Mn5–MgAl with 0.04% loaded manganese has a good crystalline morphology. A well-dispersed MnO2 nanoparticles encapsulated into the host matrix of hydrotalcite exhibit enhanced electrocatalytic activity towards the reduction of H2O2 as well as excellent stability, selectivity and reproducibility due to synergistic effect of good catalytic ability of MnO2 and conductive MgAl LDH. Glass carbon electrode (GCE) modified with Mn5–MgAl possesses a wide linear range of 0.05–78 mM, lowest detection limit 5 μM (S/N = 3) and detection sensitivity of 0.9352 μAmM−1. This outstanding performance enables it to be used for real-time tracking of H2O2 secreted by live HeLa cells. This work may provide new insight in clinical diagnosis, on-site environmental analysis and point of care testing devices. 相似文献
63.
臭氧氧化结合湿法喷淋对玻璃窑炉烟气同时脱硫脱硝实验研究 总被引:2,自引:0,他引:2
采用臭氧氧化结合湿法喷淋对模拟玻璃窑炉烟气开展了同时脱硫脱硝实验研究.采用不同溶液(NaOH、Na2S)进行了喷淋实验.结果表明,保证溶液pH值在10以上,NaOH浓度对NOx脱除效率无影响,SO2的存在促进了NOx吸收.当O3/NO物质的量比为1.6、溶液NaOH浓度为0.5%时,NOx脱除效率可达70%,SO2脱除效率在99%以上.往喷淋液中添加Na2S,NOx脱除效率随Na2S浓度增加而提高,SO2的存在对NOx脱除效率无影响.当O3/NO物质的量比为1.2、溶液中NaOH浓度为0.5%、添加剂Na2S浓度为0.6%时,NOx脱除效率可达70%,SO2脱除效率在95%以上.60 min长时间运行实验证明,模拟烟气中的NOx经碱液和添加剂吸收后主要以NO-2的形式存在于喷淋液中,且NOx脱除效率不随溶液pH值的变化而变化. 相似文献
64.
Utilization of Active Ni to Fabricate Pt–Ni Nanoframe/NiAl Layered Double Hydroxide Multifunctional Catalyst through In Situ Precipitation 下载免费PDF全文
Dr. Liangfeng Luo Haiyuan Lu Prof. Gang Zhou Prof. Weixin Huang Prof. Xun Hong Prof. Yuen Wu Prof. Yadong Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(38):13181-13185
Integration of different active sites into metallic catalysts, which may impart new properties and functionalities, is desirable yet challenging. Herein, a novel dealloying strategy is demonstrated to decorate nickel–aluminum layered double hydroxide (NiAl–LDH) onto a Pt–Ni alloy surface. The incorporation of chemical etching of Pt–Ni alloy and in situ precipitation of LDH are studied by joint experimental and theoretical efforts. The initial Ni‐rich Pt–Ni octahedra transform by interior erosion into Pt3Ni nanoframes with enlarged surface areas. Furthermore, owing to the basic active sites of the decorated LDH together with the metallic sites of Pt3Ni, the resulting Pt–Ni nanoframe/NiAl–LDH composites exhibit excellent catalytic activity and selectivity in the dehydrogenation of benzylamine and hydrogenation of furfural. 相似文献
65.
Dr. Kimiaka C. Guérard Vincent Hamel Dr. Amandine Guérinot Cloé Bouchard‐Aubin Prof. Sylvain Canesi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18068-18071
A rapid route to 5,5‐ and 5,6‐ bicyclic systems is provided by an 1,3‐alkyl‐shift process mediated by a hypervalent iodine reagent on aromatics. The structures obtained contain several unsaturations with different behaviors and reactivities. Such diversity allows further elaborations for the rapid formation of compact systems present in a variety of natural products. The potential for further transformations has been demonstrated by performing a double Michael addition. This cyclization process is regio‐ and stereoselective due to the presence of a former benzylic substituent. Furthermore, an extension of this approach has been accomplished on indole derivatives. 相似文献
66.
Topochemical Transformations of CaX2 (X=C,Si, Ge) to Form Free‐Standing Two‐Dimensional Materials 下载免费PDF全文
Saied Md. Pratik A. Nijamudheen Prof. Dr. Ayan Datta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18454-18460
Topochemical transformations of layered materials CaX2 (X=Si, Ge) are the method of choice for the high‐yield synthesis of pristine, defect‐free two‐dimensional systems silicane and germanane, which have advanced electronic properties. Based on solid‐state dispersion‐corrected calculations, mechanisms for such transformations are elucidated that provide an in‐depth understanding of phase transition in these layered materials. While formation of such layered materials is highly favorable for silicane and germanane, a barrier of 1.2 eV in the case of graphane precludes its synthesis from CaC2 topochemically. The energy penalty required for distorting linear acetylene into a trans‐bent geometry accounts for this barrier. In contrast it is highly favorable in the heavier analogues, resulting in barrierless topochemical generation of silicane and germanane. Photochemical generation of the trans‐bent structure of acetylene in its first excited state (S1) can directly generate graphane through a barrierless condensation. Unlike the buckled structure of silicene, the phase‐h of CaSi2 with perfectly planar silicene layers exhibits the Dirac cones at the high symmetry points K and H. Interestingly, topochemical acidification of the cubic phase of calcium carbide is predicted to generate the previously elusive platonic hydrocarbon, tetrahedrane. 相似文献
67.
由摩尔比分别为1:2和1:8的NiCl2·6H2O和Na2B4O7·10H2O作为反应物, 合成两种非晶态镍硼酸盐, 同时通过水热法合成β-Ni(OH)2. 化学分析和热重-微商热重法(TG-DTG)分析结果确定两种非晶态镍硼酸盐的分子组成分别为NiO·0.8B2O3·4.5H2O和NiO·B2O3·3H2O. 激光拉曼(Raman)实验结果表明镍硼酸盐样品中主要存在的硼氧阴离子为B3O3(OH)52-和B2O(OH)62-. 同步辐射扩展X射线吸收精细结构(EXAFS)方法对样品进行结构解析, 通过数据拟合给出样品中Ni 原子周围近邻配位原子种类、配位数以及原子间距离. 用不同晶体结构作为标准对两种非晶态镍硼酸盐进行拟合的结果表明, 样品中Ni 原子周围局域结构与Ni3B2O6晶体(ICSD No.31387)中的吻合较好. Ni 原子周围配位原子为O、B和Ni, 对于NiO·0.8B2O3·4.5H2O, 配位数分别为5.7、3.8和3.8, 配位距离分别为0.208、0.263 和0.311 nm; 对于NiO·B2O3·3H2O, 配位数分别为6.0、4.0 和4.0, 配位距离分别为0.207、0.262和0.310 nm. 相似文献
68.
69.
采用共沉淀法制备性能优异的层状材料锌铬水滑石(ZnxCr-LDHs, x=2, 3, 4), 并探究各种因素对吸附酸性红14(AR14)的影响。XRD、ICP、FTIR及BET表征结果表明:合成的ZnxCr-LDHs晶型良好且稳定, 具备介孔结构。实验结果表明:最佳吸附剂为Zn3Cr-LDHs, 比表面积为101 m2·g-1, 对AR14的最大吸附容量为484.63 mg·g-1。同时, 降低溶液pH值和提高溶液温度均可促进AR14的吸附。该吸附过程分别符合准二级动力学模型和Freundlich等温吸附模型。结合Materials Studio 5.5软件模拟, 推测该吸附机理主要以表面吸附为主, -SO3-基团是反应点。 相似文献
70.
用共沉淀法制备油酸钾改性的Zn2+、Al 3+层状双氢氧化物(Zn/Al-LDH),以环己酮为溶剂,用溶液插层法制备了Zn/Al层状双氢氧化物-聚氯乙烯(PVC)纳米复合物。采用傅里叶红外(FT-IR)、X-射线衍射(XRD)、透射电镜(TEM)对复合材料的结构及形貌进行了表征,并用热分析仪、万能试验机和紫外分光光度计研究了复合物的热稳定性能、拉伸性能和紫外吸收性能。结果表明:Zn/Al-LDH纳米片层无序分散在PVC基体中;Zn/Al-LDH对PVC低温时的骨干脱氯化氢有促进作用;与PVC膜相比,复合膜的分解温度降低,高温碳化温度升高,复合膜的拉伸强度及断裂伸长率得到提高,在300~380nm具有一定的紫外吸收性能。 相似文献