排序方式: 共有49条查询结果,搜索用时 15 毫秒
21.
Liao Y Eichinger BE Firestone KA Haller M Luo J Kaminsky W Benedict JB Reid PJ Jen AK Dalton LR Robinson BH 《Journal of the American Chemical Society》2005,127(8):2758-2766
A series of novel nonlinear optical (NLO) chromophores 1-4 incorporating the ferrocenyl (Fc) group as an electron donor and 2-dicyanomethylene-3-cyano-4-methyl-2,5-dihydrofuran (TCF) derivatives as electron acceptors are presented. The use of a constant Fc donor and varied acceptors and bridges makes it possible to systematically determine the contribution of the conjugated bridge and the acceptor strength to chromophore nonlinear optical activity. The X-ray crystal structures of all four chromophores allow for the systematic investigation of the structure-property relationship for this class of molecules. For example, the crystal structures reveal that both cyclopentadienyl groups in the ferrocenyl donor contribute to the electron donating ability. The first-order hyperpolarizabilities beta of these chromophores, measured by hyper-Rayleigh scattering (HRS) relative to p-nitroaniline are reported. These beta values are compared to those calculated by density functional theory (DFT). The excellent agreement between the theoretical and experimental beta values demonstrates that a linear relation exists between the hyperpolarizability and the bond length alternation. An electrooptic coefficient, r(33), of approximately 25 pm/V at 1300 nm, for compound 4, incorporated into a polymer matrix, is competitive with organic chromophores. Moreover, this r(33) is more than 30 times larger than the previously reported value for an organometallic chromophore in a poled polymer matrix. This work not only underscores the potential for Fc donor moieties, which have been underutilized, but also demonstrates that experimental characterization and theoretical simulations are now congruent, viable methods for assessing potential performance of NLO materials. 相似文献
22.
Shi Z Davies J Jang SH Kaminsky W Jen AK 《Chemical communications (Cambridge, England)》2012,48(63):7880-7882
The AIE properties of two trifluoromethyl substituted distyrylbenzene model compounds were compared. The fluorescence quantum efficiency of these molecules can be modulated by tuning their subtle solid-state intermolecular interactions. 相似文献
23.
Schlamminger S Choi KY Wagner TA Gundlach JH Adelberger EG 《Physical review letters》2008,100(4):041101
We used a continuously rotating torsion balance instrument to measure the acceleration difference of beryllium and titanium test bodies towards sources at a variety of distances. Our result Deltaa(N),(Be-Ti)=(0.6+/-3.1)x10(-15) m/s2 improves limits on equivalence-principle violations with ranges from 1 m to infinity by an order of magnitude. The E?tv?s parameter is eta(Earth,Be-Ti)=(0.3+/-1.8)x10(-13). By analyzing our data for accelerations towards the center of the Milky Way we find equal attractions of Be and Ti towards galactic dark matter, yielding eta(DM,Be-Ti)=(-4+/-7)x10(-5). Space-fixed differential accelerations in any direction are limited to less than 8.8x10(-15) m/s2 with 95% confidence. 相似文献
24.
Giddings AD Khalid MN Jungwirth T Wunderlich J Yasin S Campion RP Edmonds KW Sinova J Ito K Wang KY Williams D Gallagher BL Foxon CT 《Physical review letters》2005,94(12):127202
We report a large tunneling anisotropic magnetoresistance (TAMR) in (Ga,Mn)As lateral nanoconstrictions. Unlike previously reported tunneling magnetoresistance effects in nanocontacts, the TAMR does not require noncollinear magnetization on either side of the constriction. The nature of the effect is established by a direct comparison of its phenomenology with that of normal anisotropic magnetoresistance (AMR) measured in the same lateral geometry. The direct link we establish between the TAMR and AMR indicates that TAMR may be observable in other materials showing room temperature AMR and demonstrates that the physics of nanoconstriction magnetoresistive devices can be much richer than previously thought. 相似文献
25.
In tonal languages, there are potential conflicts between the FO-based changes due to the coexistence of intonation and lexical tones. In the present study, the interaction of tone and intonation in Cantonese was examined using acoustic and perceptual analyses. The acoustic patterns of tones at the initial, medial, and final positions of questions and statements were measured. Results showed that intonation affects both the FO level and contour, while the duration of the six tones varied as a function of positions within intonation contexts. All six tones at the final position of questions showed rising FO contour, regardless of their canonical form. Listeners were overall more accurate in the identification of tones presented within the original carrier than of the same tones in isolation. However, a large proportion of tones 33, 21, 23, and 22 at the final position of questions were misperceived as tone 25 both within the original carrier and as isolated words. These results suggest that although the intonation context provided cues for correct tone identification, the intonation-induced changes in FO contour cannot always be perceptually compensated for, resulting in some erroneous perception of the identity of Cantonese tone. 相似文献
26.
Effective in-device r33 of 735 pm/V on electro-optic polymer infiltrated silicon photonic crystal slot waveguides 总被引:1,自引:0,他引:1
We design and fabricate a 320?nm slot for an electro-optic (E-O) polymer infiltrated silicon photonic crystal waveguide. Because of the large slot width, the poling efficiency of the infiltrated E-O polymer (AJCKL1/amorphous polycarbonate) is significantly improved. When coupled with the slow light effect from the silicon photonic crystal waveguide, an effective in-device r(33) of 735?pm/V, which to our knowledge is a record high, is demonstrated, which is ten times higher than the E-O coefficient achieved in thin film material. Because of this ultrahigh E-O efficiency, the V(π)L of the device is only 0.44?V?mm, which is to our knowledge the best result of all E-O polymer modulators. 相似文献
27.
Chiral molecular triangles and squares containing the Pt(diimine) metallocorners were synthesized and characterized, and used as the triplet MLCT luminophore in highly efficient light-emitting devices. 相似文献
28.
Increased open circuit voltage in fluorinated benzothiadiazole-based alternating conjugated polymers
Zhang Y Chien SC Chen KS Yip HL Sun Y Davies JA Chen FC Jen AK 《Chemical communications (Cambridge, England)》2011,47(39):11026-11028
Small band-gap conjugated polymers based on monofluoro- and difluoro-substituted benzothiadiazole were developed. Highly efficient polymer solar cells (PCE as high as 5.40%) could be achieved for devices made from these polymers. 相似文献
29.
The synthesis of M(II)(2) complexes (M(II)=Co, Mn) with terminal hydroxo ligands has been achieved utilizing a dinucleating ligand containing a bridging pyrazolate unit and appended (neopentyl)aminopyridyl groups. Structural studies on the complexes revealed that the M(II)-OH units are positioned in a syn-configuration, placing the hydroxo ligands in close proximity (ca. 3 ? apart), which may be a prerequisite for water oxidation. 相似文献
30.
Nanostructured TiO(2)(B) thin films were found to have strong and fast chemiresistive response to nitro-aromatic and nitro-amino explosives recently. In this study, the effects of dipole moment and electron deficiency of the analyte molecules on the chemiresistive response are explored to understand the details of molecular interactions of analytes with the sensor surface which lead to charge depletion and the chemiresistive effect. It was found that the speed of the response is dominated by the polarity of the analytes and molecules with larger dipole moments produce faster responses. The degree of the response was found to be dominated by the electron deficiency of the analytes and molecules with greater electron deficiency produce stronger chemiresistive responses. 相似文献