RESUMO
To realize the relationship of structure and property, four novel twistacene-functionalized arenes, namely, 1,4-bis(2,7-di-tert-butyl-9,14-bis(4-(tert-butyl)phenyl)dibenzo[de,qr]tetracen-11-yl)buta-1,3-diyne (4), 1,4-bis(3,5,10,12-tetra-tert-butyltribenzo[a,d,g]coronen-16-yl)buta-1,3-diyne (7), 1,4-bis(2,7-di-tert-butyl-9,14-bis(4-(tert-butyl)phenyl)dibenzo[de,qr]tetracen-10-yl)buta-1,3-diyne (10), 1,4-bis(3,5,10,12-tetra-tert-butyltribenzo[a,d,g]coronen-15-yl)buta-1,3-diyne (13), linked with butadiyne as π bridges have been strategically synthesized and characterized. The nonlinear optical properties are detailly examined in solution through the open-aperture Z-scan method in a comparative manner, indicating that molecules 4 and 7 exhibit better nonlinear optical responses than 10 and 13. Among them, 4 and 7 exhibit excellent optical limiting responses with limiting thresholds of 0.17 and 0.19 J/cm2, respectively, being superior to the state-of-the-art material C60. The ultrafast transient absorption test and DFT calculations suggest that the nonlinear absorption mechanisms belong to TPA-induced ESA. In addition, the effective percentage calculated from TD-DFT can provide a brief glance to evaluate the optical limiting performance.
RESUMO
A pair of novel chiral 1-phenylethylamine-modified twistarenes (4 and 11; compound 4 = 9,14-di-tert-butyl-7,16-diphenyl-2-(1-phenylethyl)-1H-benzo[8',9']triphenyleno[2',3':6,7]fluoreno[2,1,9-def]isoquinoline-1,3(2H)-dione) have been synthesized and characterized, and how the solvent component affects the chirality transfer of their self-assembled processes is investigated in mixtures with THF and H2O. The ordered assembly of 11 exhibits circular dichroism response. In addition, both 11a and 11b display positive photoconducting behavior.
RESUMO
Two pairs of isomers of heptagon-embedded helical arenes (3/6 and 10/13) have been strategically prepared, where the molecular structures of 3 and 13 have been identified through single crystal X-ray diffraction analysis. The effect of the heptagon unit on the physical properties of 3, 6, 10, and 13 is investigated in a comparative manner, and the results indicate that the optical enantiomers of 13 obtained from HPLC exhibit promising chiroptical properties.
RESUMO
BACKGROUND Despite an increasing number of published articles on intravoxel incoherent motion (IVIM) in the past decade, almost all have focused on the technique and clinical applications of IVIM, with little attention to the collective knowledge and scientific analysis of this field. The aim of the present study was to construct a knowledge framework and to explore hotspots and emerging trends concerning use of IVIM in humans. MATERIAL AND METHODS The articles concerning IVIM MRI published from 1988 to 2021 were retrieved from the Science Citation Index Expended of the Web of Science Core Collection on 17, August 2021. The downloaded data were imported into Excel 2016 and CiteSpace V for scientometric analysis. RESULTS A total of 921 articles were included in this study and most of them were published since 2012. China (n=392) was the most productive country and the Philips Healthcare (n=46) was the most productive institution. Christian Federau had the largest number of publications (n=18). An article by Andreou A et al (2013) was the most important reference with the most co-citations (n=100) and centrality (0.06). The 5 hotspots in IVIM were perfusion, diffusion-weighted imaging, intravoxel incoherent motion, apparent diffusion coefficient, and magnetic resonance imaging. The 2 frontier topics were "brain perfusion" and "accuracy". According to the clustering of co-citation analysis, "liver", "diffusion weighting", "pancreas", and "brain" were the main research directions. CONCLUSIONS Scientometric analysis of IVIM literature with CiteSpace software can provide researchers with valuable information about knowledge framework, hotspots, and emerging trends concerning IVIM in humans.
