首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7篇
  免费   1篇
化学   5篇
物理学   3篇
  2022年   1篇
  2020年   2篇
  2018年   1篇
  2016年   1篇
  2013年   2篇
  1972年   1篇
排序方式: 共有8条查询结果,搜索用时 0 毫秒
1
1.
Three banana‐shaped monomers, i.e. 2,7‐naphthalene bis[4‐(4‐allyloxyphenylazo)‐benzoate], 2,7‐naphthalene bis[4‐(4‐allyloxy‐3‐fluorophenylazo)benzoate] and 2,7‐naphthalene bis{4‐[4‐(10‐undecenyloxy)phenylazo]benzoate}, containing azobenzene as side arms, 2,7‐dihydroxynaphthalene as central units and terminal double bonds as polymerisable functional groups, were synthesised and their mesophase behaviour investigated. Polarizing optical microscopy and DSC measurements reveal that all compounds exhibit nematic mesophases. The absorption spectrum of the trans‐azobenzene groups displays a high‐intensity π–π* transition at about 365 nm and a low‐intensity n–π* transition at around 450 nm for all compounds. Hence, photochromism can be achieved by the introduction of the azo linkage to banana‐shaped liquid crystals molecules.  相似文献   
2.
Journal of Cluster Science - In the present study, catechin was successfully grafted in reduced graphene oxide Zinc oxide (rGO/ZnO) nanocomposite by solvent free hydrothermal method. Absorption...  相似文献   
3.
Three paramagnetic CoII macrocyclic complexes containing 2‐hydroxypropyl pendant groups, 1,1′,1′′,1′′′‐(1,4,8,11‐tetraazacyclotetradecane‐1,4,8,11‐tetrayl)tetrakis‐ (propan‐2‐ol) ([Co(L1)]2+, 1,1′‐(4,11‐dibenzyl‐1,4,8,11‐tetraazacyclotetradecane‐1,8‐diyl)bis(propan‐2‐ol) ([Co(L2)]2+), and 1,1′‐(4,11‐dibenzyl‐1,4,8,11‐tetraazacyclotetradecane‐1,8‐diyl)bis(octadecan‐2‐ol) ([Co(L3)]2+) were synthesized to prepare transition metal liposomal chemical exchange saturation transfer (lipoCEST) agents. In solution, ([Co(L1)]2+) forms two isomers as shown by 1H NMR spectroscopy. X‐ray crystallographic studies show one isomer with 1,8‐pendants in cis‐configuration and a second isomer with 1,4‐pendants in trans‐configuration. The [Co(L2)]2+ complex has 1,8‐pendants in a cis‐configuration. Remarkably, the paramagnetic‐induced shift of water 1H NMR resonances in the presence of the [Co(L1)]2+ complex is as large as that observed for one of the most effective LnIII water proton shift agents. Incorporation of [Co(L1)]2+ into the liposome aqueous core, followed by dialysis against a solution of 300 mOsm L?1 produces a CEST peak at 3.5 ppm. Incorporation of the amphiphilic [Co(L3)]2+ complex into the liposome bilayer produces a more highly shifted CEST peak at ?13 ppm. Taken together, these data demonstrate the feasibility of preparing CoII lipoCEST agents.  相似文献   
4.
5.
1H-Benzo[b]pyrrole samples were irradiated in the air with gamma source at 0.969?kGy per hour at room temperature for 24, 48 and 72?h. After irradiation, electron spin resonance, thermogravimetry analysis (TGA) and differential thermal analysis (DTA) measurements were immediately carried out on the irradiated and unirradiated samples. The ESR measurements were performed between 320 and 400?K. ESR spectra were recorded from the samples irradiated for 48 and 72?h. The obtained spectra were observed to be dependent on temperature. Two radical-type centres were detected on the sample. Detected radiation-induced radicals were attributed to R-+?NH and R=?CC2H2. The g-values and hyperfine constants were calculated by means of the experimental spectra. It was also determined from TGA spectrum that both the unirradiated and irradiated samples were decomposed at one step with the rising temperature. Moreover, a theoretical study was presented. Success of the machine learning methods was tested. It was found that bagging techniques, which are widely used in the machine learning literature, could optimise prediction accuracy noticeably.  相似文献   
6.
Four novel nonsymmetric dimers containing azobenzene mesogenic groups were synthesized. The nonsymmetric dimers compounds namely, ethyl 4-[(4-{4-(4-((4-nitrophenyl)diazenyl)phenoxy)alkyloxy}phenyl)diazenyl]benzoate were obtained from the alkylation of ethyl 4-[(4-(4-bromoalkyloxy)phenyl)diazenyl]benzoate with 4-[(4-nitrophenyl)diazenyl]phenol. The mesomorphic properties of the compounds were determined by DSC and polarizing optical microscopy. The first member of the series was nonliquid crystalline while all other homologues display nematic and smectic A phases. The trans-azobenzene groups of the dimers display a high-intensity ππ* transition at about 365 nm and a low-intensity nπ* transition at around 465 nm, therefore, photochromism can be achieved by the introduction of the azo linkage to the dimeric liquid crystalline molecules.  相似文献   
7.
The visible‐light‐accelerated oxo‐azidation of vinyl arenes with trimethylsilylazide and molecular oxygen as stoichiometric oxidant was achieved. In contrast to photocatalysts based on iridium, ruthenium, or organic dyes, [Cu(dap)2]Cl or [Cu(dap)Cl2] were found to be unique for this transformation, which is attributed to their ability to interact with the substrates through ligand exchange and rebound mechanisms. CuII is proposed as the catalytically active species, which upon coordinating azide will undergo light‐accelerated homolysis to form CuI and azide radicals. This activation principle (CuII‐X→CuI+X.) opens up new avenues for copper‐based photocatalysis.  相似文献   
8.
Early studies suggested that FeIII complexes cannot compete with GdIII complexes as T1 MRI contrast agents. Now it is shown that one member of a class of high‐spin macrocyclic FeIII complexes produces more intense contrast in mice kidneys and liver at 30 minutes post‐injection than does a commercially used GdIII agent and also produces similar T1 relaxivity in serum phantoms at 4.7 T and 37 °C. Comparison of four different FeIII macrocyclic complexes elucidates the factors that contribute to relaxivity in vivo including solution speciation. Variable‐temperature 17O NMR studies suggest that none of the complexes has a single, integral inner‐sphere water that exchanges rapidly on the NMR timescale. MRI studies in mice show large in vivo differences of three of the FeIII complexes that correspond, in part, to their r1 relaxivity in phantoms. Changes in overall charge of the complex modulate contrast enhancement, especially of the kidneys.  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号