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71.
Frick B Dalnoki-Veress K Forrest JA Dutcher J Murray C Higgins A 《The European physical journal. E, Soft matter》2003,12(Z1):S93-S96
Glass transition studies in free standing polymer films have revealed values of the transition temperature, T(g), which were substantially reduced below the bulk for sufficiently thin films. Here we report on the preparation of two stacks of free standing polystyrene films: 70 films with a thickness of h approximately 107 nm and 140 films with h approximately 55 nm with equivalent total sample thicknesses of approximately 7.5 microm. We have performed the first measurements on such samples using inelastic neutron scattering, and demonstrate that inelastic neutron scattering experiments, performed on the time-of-flight spectrometer IN6 and the backscattering spectrometer IN16 at the Institut Laue-Langevin, are feasible. 相似文献
72.
Ngai KL 《The European physical journal. E, Soft matter》2003,12(1):93-100
Intermolecular coupling plays an important role in determining the dynamics and the mobility of polymeric and non-polymeric glass-formers. The breadth of the dispersion is an indicator of the intermolecular coupling strength. The coupling model relates intermolecular coupling through the breadth of the dispersion to the dynamics of bulk glass-formers. When a glass-former is confined in nanometer pores or in thin films and if there is absence of chemical and physical interactions with the wall, intermolecular coupling is reduced, resulting in an increase of mobility. The coupling model is used to account for such changes of relaxation time of 1) ortho-terphenyl and poly(dimethyl siloxane) confined in nanometer pores, 2) polymer thin film confined between two impenetrable walls from Monte Carlo simulation, and 3) polymer film confined by perfectly smooth and purely repulsive potential acting on the repeat units from molecular-dynamics simulation. The model continues to explain the opposite effects observed when there is an increase of intermolecular coupling due to the presence of chemical or physical interaction with the walls.Received: 1 January 2003, Published online: 8 October 2003PACS:
64.70.Pf Glass transitions - 68.60.Bs Mechanical and acoustical properties - 36.20.-r Macromolecules and polymer molecules 相似文献
73.
74.
Mathieu Le Tacon T.R. Forrest Ch. Rüegg J. Noffsinger A.C. Walters P. Toulemonde N.D. Zhigadlo J.P. Hill D.F. McMorrow 《Journal of Physics and Chemistry of Solids》2011,72(5):523-526
We report measurements of the phonon density of states as probed with inelastic X-ray scattering in SmFeAsO1−xFy powders. An unexpected strong renormalization of phonon branches around 23 meV is observed as fluorine is substituted for oxygen. Phonon dispersion measurements on SmFeAsO1−xFy single crystals allow us to identify the 21 meV A1g in-phase (Sm,As) and the 26 meV B1g (Fe,O) modes to be responsible for this renormalization, and may reveal unusual electron-phonon coupling through the spin channel in iron-based superconductors. 相似文献
75.
Chun‐Kai Wang Xiaozhou Che Yuan‐Chih Lo Ya‐Ze Li Yung‐Hao Wang Stephen R. Forrest Shun‐Wei Liu Ken‐Tsung Wong 《化学:亚洲杂志》2020,15(16):2520-2531
Four new donor‐acceptor‐acceptor’ (D‐A‐A’)‐configured donors, CPNT , DCPNT , CPNBT , and DCPNBT equipped with naphtho[1,2‐c:5,6‐c′]bis([1,2,5]‐thiadiazole) (NT) or naphtho[2,3‐c][1,2,5]thiadiazole (NBT) as the central acceptor (A) unit bridging triarylamine donor (D) and cyano or dicyanovinylene acceptor (A’), were synthesized and characterized. All molecules exhibit bathochromic absorption shifts as compared to those of the benzothiadiazole (BT)‐based analogues owing to improved electron‐withdrawing and quinoidal character of NT and NBT cores that lead to stronger intramolecular charge transfer. Favorable energy level alignments with C70, together with the good thermal stability and the antiparallel dimeric packing render CPNT and DCPNT suitable donors for vacuum‐processed organic photovoltaics (OPV)s. OPVs based on DCPNT : C70 active layers displayed the best power conversion efficiency (PCE)=8.3%, along with an open circuit voltage of 0.92 V, a short circuit current of 14.5 mA cm?2 and a fill factor of 62% under 1 sun intensity, simulated AM1.5G illumination. Importantly, continuous light‐soaking with AM 1.5G illumination has verified the durability of the devices based on CPNT :C70 and DCPNT : C70 as the active blends. The devices were examined for their feasibility of indoor light harvesting under 500 lux illumination by a TLD‐840 fluorescent lamp, giving PCE=12.8% and 12.6%, respectively. These results indicate that the NT‐based D‐A‐A’‐type donors CPNT and DCPNT are potential candidates for high‐stability vacuum‐processed OPVs suitable for indoor energy harvesting. 相似文献
76.
Xue Jiang Dr. Tony Pham Jian-Wei Cao Dr. Katherine A. Forrest Dr. Hui Wang Dr. Juan Chen Prof. Dr. Qiu-Yu Zhang Prof. Dr. Kai-Jie Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9446-9453
Rigid molecular sieving materials are the ideal candidates for gas separation (e. g., C2H2/C2H4) due to their ultrahigh adsorption selectivity and the absence of gas co-adsorption. However, the absolute molecular sieving effect for C2H2/C2H4 separation has rarely been realized because of their similar physicochemical properties. Herein, we demonstrate the absolute molecular sieving of C2H2 from C2H4 by a rigid ultra-microporous metal-organic framework ( F−PYMO−Cu ) with 1D regular channels (pore size of ca. 3.4 Å). F−PYMO−Cu exhibited moderate acetylene uptake (35.5 cm3/cm3), but very low ethylene uptake (0.55 cm3/cm3) at 298 K and 1 bar, yielding the second highest C2H2/C2H4 uptake ratio of 63.6 up to now. One-step C2H4 production from a binary mixture of C2H2/C2H4 and a ternary mixture of C2H2/CO2/C2H4 at 298 K was achieved and verified by dynamic breakthrough experiments. Coupled with excellent thermal and water stability, F−PYMO−Cu could be a promising candidate for industrial C2 separation tasks. 相似文献
77.
Synthesis of a Neutral Mixed‐Valence Diferrocenyl Carborane for Molecular Quantum‐Dot Cellular Automata Applications 下载免费PDF全文
John A. Christie Ryan P. Forrest Dr. Steven A. Corcelli Dr. Natalie A. Wasio Dr. Rebecca C. Quardokus Dr. Ryan Brown Dr. S. Alex Kandel Dr. Yuhui Lu Dr. Craig S. Lent Dr. Kenneth W. Henderson 《Angewandte Chemie (International ed. in English)》2015,54(51):15448-15451
The preparation of 7‐Fc+‐8‐Fc‐7,8‐nido‐[C2B9H10]? (Fc+FcC2B9?) demonstrates the successful incorporation of a carborane cage as an internal counteranion bridging between ferrocene and ferrocenium units. This neutral mixed‐valence FeII/FeIII complex overcomes the proximal electronic bias imposed by external counterions, a practical limitation in the use of molecular switches. A combination of UV/Vis‐NIR spectroscopic and TD‐DFT computational studies indicate that electron transfer within Fc+FcC2B9? is achieved through a bridge‐mediated mechanism. This electronic framework therefore provides the possibility of an all‐neutral null state, a key requirement for the implementation of quantum‐dot cellular automata (QCA) molecular computing. The adhesion, ordering, and characterization of Fc+FcC2B9? on Au(111) has been observed by scanning tunneling microscopy. 相似文献
78.
Sun C Turlington CR Thomas WW Wade JH Stout WM Grisenti DL Forrest WP VanDerveer DG Wagenknecht PS 《Inorganic chemistry》2011,50(19):9354-9364
Alkynyl complexes of the type [M(cyclam)(CCR)(2)]OTf (where cyclam = 1,4,8,11-tetraazacyclotetradecane; M = Rh(III) or Cr(III); and R = phenyl, 4-methylphenyl, 4-trifluoromethylphenyl, 4-fluorophenyl, 1-naphthalenyl, 9-phenanthrenyl, and cyclohexyl) were prepared in 49% to 93% yield using a one-pot synthesis involving the addition of 2 equiv of RCCH and 4 equiv of BuLi to the appropriate [M(cyclam)(OTf)(2)]OTf complex in THF. The cis and trans isomers of the alkynyl complexes were separated using solubility differences, and the stereochemistry was characterized using infrared spectroscopy of the CH(2) rocking and NH bending region. All of the trans-[M(cyclam)(CCR)(2)]OTf complexes exhibit strong Raman bands between 2071 and 2109 cm(-1), ascribed to ν(s)(C≡C). The stretching frequencies for the Cr(III) complexes are 21-28 cm(-1) lower than for the analogous Rh(III) complexes, a result that can be interpreted in terms of the alkynyl ligands acting as π-donors. UV-vis spectra of the Cr(III) and Rh(III) complexes are dominated by strong charge transfer (CT) transitions. In the case of the Rh(III) complexes, these CT transitions obscure the metal centered (MC) transitions, but in the case of the Cr(III) complexes the MC transitions are unobscured and appear between 320 and 500 nm, with extinction coefficients (170-700 L mol(-1) cm(-1)) indicative of intensity stealing from the proximal CT bands. The Cr(III) complexes show long-lived (240-327 μs), structureless, MC emission centered between 731 and 748 nm in degassed room temperature aqueous solution. Emission characteristics are also consistent with the arylalkynyl ligands acting as π-donors. The Rh(III) complexes also display long-lived (4-21 μs), structureless, metal centered emission centered between 524 and 548 nm in degassed room temperature solution (CH(3)CN). 相似文献
79.
A method is described for the analysis of hydrogen, oxygen, nitrogen, methane and carbon monoxide by gas-solid chromatography, using an ionisation method for detection. Accuracies of determination comparable with those of the best katharometers are: attainable, without the need for the high accuracy of flow control or careful thermostatic control associated with katharometers. An ultimate detection level of 0.1 μ1 of s.t.p. gas can be obtained. 相似文献
80.
Yun‐Lei Peng Dr. Tony Pham Pengfei Li Ting Wang Prof. Yao Chen Prof. Kai‐Jie Chen Dr. Katherine A. Forrest Prof. Brian Space Prof. Peng Cheng Dr. Michael J. Zaworotko Prof. Zhenjie Zhang 《Angewandte Chemie (International ed. in English)》2018,57(34):10971-10975
Highly selective separation and/or purification of acetylene from various gas mixtures is a relevant and difficult challenge that currently requires costly and energy‐intensive chemisorption processes. Two ultramicroporous metal–organic framework physisorbents, NKMOF‐1‐M (M=Cu or Ni), offer high hydrolytic stability and benchmark selectivity towards acetylene versus several gases at ambient temperature. The performance of NKMOF‐1‐M is attributed to their exceptional acetylene binding affinity as revealed by modelling and several experimental studies: in situ single‐crystal X‐ray diffraction, FTIR, and gas mixture breakthrough tests. NKMOF‐1‐M exhibit better low‐pressure uptake than existing physisorbents and possesses the highest selectivities yet reported for C2H2/CO2 and C2H2/CH4. The performance of NKMOF‐1‐M is not driven by the same mechanism as current benchmark physisorbents that rely on pore walls lined by inorganic anions. 相似文献