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91.
Srnová-Sloufová I Vlcková B Snoeck TL Stufkens DJ Matĕjka P 《Inorganic chemistry》2000,39(16):3551-3559
Excitation profiles of SERS (surface-enhanced Raman scattering) and/or SERRS (surface-enhanced resonance Raman scattering) spectral bands of two forms of a Ag-bpy (bpy = 2,2'-bipyridine) surface complex and of [Ru(bpy)3]2+ on Ag nanoparticle (hydrosol) surfaces were determined from the spectra excited in the 458-600 nm region and are reported together with the FT-SERS spectra of the Ag-bpy surface complex and FT Raman spectra of [Ru(bpy)3] Cl2. Seven of the observed 11 fundamentals as well as their first overtones and combination bands are selectively enhanced in SERS of the Ag-bpy surface complex formed in the Ag colloid/HCl/bpy system. The profiles of these bands show a common maximum at approximately 540 nm. The selectively enhanced bands of the Ag-bpy surface complex have nearly the same wavenumbers as those enhanced in the SERRS and resonance Raman spectra of [Ru(bpy)3]2+ upon excitation close to the 453 nm maximum of its MLCT absorption band. Moreover, the intensity patterns of the bpy vibrations of the two species match both in resonance (541 nm excitation for Ag-bpy, 458 nm for [Ru(bpy)3]2+) and in off-resonance (458 and 1064 nm for Ag-bpy, 1064 nm for [Ru(bpy)3]2+). The distinct band shapes of the excitation profiles of the selectively enhanced vibrational modes of the Ag-bpy surface complex, as well as the observation of overtones and combination bands in the SERS spectra upon excitation into this "band", are interpreted in terms of a charge-transfer resonance contribution to the overall SERS enhancement. In view of the near-coincidence of the vibrational modes coupled to the resonant electronic transition of Ag-bpy with those coupled to the MLCT transition of [Ru(bpy)3]2+, the resonant electronic transition is tentatively assigned to a Ag metal to bpy (pi*) CT transition. 相似文献
92.
D. Levy F. Del Monte J.M. Otón G. Fiksman I. Matías P. Datta M. López-amo 《Journal of Sol-Gel Science and Technology》1997,8(1-3):931-935
Photochromic-doped sol-gel materials have been prepared by adding a spiropyran photochromic dye to a solution of ethoxy silane monomers containing non-reacting ethyl radicals. After polymerization, normal photochromism (i.e., colored material upon UV irradiation) is obtained in the resulting matrix. The sol-gel matrix hinders the organic molecule rotations, thus giving two stable states, which can be reversibly switched by UV and green-blue irradiation respectively.If these materials are attached to optical fibers, the properties of the light throughput may be modified. Simple fiber-optic/photochromic devices made of two optical fibers placed in a V-groove removable connector have been prepared. Once cured, these devices behave as optically addressed variable delay generators. The same devices can be used for preparing simple optical switches and routing systems. 相似文献
93.
A Nexus between Theory and Experiment: Non‐Empirical Quantum Mechanical Computational Methodology Applied to Cucurbit[n]uril⋅Guest Binding Interactions
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Jiří Hostaš Dr. David Sigwalt Marina Šekutor Haresh Ajani Dr. Matúš Dubecký Prof. Jan Řezáč Dr. Peter Y. Zavalij Dr. Liping Cao Christian Wohlschlager Prof. Kata Mlinarić‐Majerski Prof. Lyle Isaacs Prof. Robert Glaser Prof. Pavel Hobza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17226-17238
A training set of eleven X‐ray structures determined for biomimetic complexes between cucurbit[n]uril (CB[7 or 8]) hosts and adamantane‐/diamantane ammonium/aminium guests were studied with DFT‐D3 quantum mechanical computational methods to afford ΔGcalcd binding energies. A novel feature of this work is that the fidelity of the BLYP‐D3/def2‐TZVPP choice of DFT functional was proven by comparison with more accurate methods. For the first time, the CB[n] ? guest complex binding energy subcomponents [for example, ΔEdispersion, ΔEelectrostatic, ΔGsolvation, binding entropy (?TΔS), and induced fit Edeformation(host), Edeformation(guest)] were calculated. Only a few weeks of computation time per complex were required by using this protocol. The deformation (stiffness) and solvation properties (with emphasis on cavity desolvation) of cucurbit[n]uril (n=5, 6, 7, 8) isolated host molecules were also explored by means of the DFT‐D3 method. A high ρ2=0.84 correlation coefficient between ΔGexptl and ΔGcalcd was achieved without any scaling of the calculated terms (at 298 K). This linear dependence was utilized for ΔGcalcd predictions of new complexes. The nature of binding, including the role of high energy water molecules, was also studied. The utility of introduction of tethered [‐(CH2)nNH3]+ amino loops attached to N,N‐dimethyl‐adamantane‐1‐amine and N,N,N′,N′‐tetramethyl diamantane‐4,9‐diamine skeletons (both from an experimental and a theoretical perspective) is presented here as a promising tool for the achievement of new ultra‐high binding guests to CB[7] hosts. Predictions of not yet measured equilibrium constants are presented herein. 相似文献
94.
Ben Andrews Mat Langford James McCoy 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2013
We consider compact, embedded hypersurfaces of Euclidean spaces evolving by fully non-linear flows in which the normal speed of motion is a homogeneous degree one, concave or convex function of the principal curvatures, and prove a non-collapsing estimate: Precisely, the function which gives the curvature of the largest interior ball touching the hypersurface at each point is a subsolution of the linearized flow equation if the speed is concave. If the speed is convex then there is an analogous statement for exterior balls. In particular, if the hypersurface moves with positive speed and the speed is concave in the principal curvatures, the curvature of the largest touching interior ball is bounded by a multiple of the speed as long as the solution exists. The proof uses a maximum principle applied to a function of two points on the evolving hypersurface. We illustrate the techniques required for dealing with such functions in a proof of the known containment principle for flows of hypersurfaces. 相似文献
95.
Palou Martin T. Kuzielová Eva Žemlička Matúš Tkácz Jakub Másilko Jiří 《Journal of Thermal Analysis and Calorimetry》2019,138(6):4155-4165
Journal of Thermal Analysis and Calorimetry - The combined effect of temperature and vapor pressure on hydration reactions of three different types of Portland cements was studied using a... 相似文献
96.
97.
In several previous papers we have argued for a global and non-entropic approach to the problem of the arrow of time, according
to which the “arrow” is only a metaphorical way of expressing the geometrical time-asymmetry of the universe. We have also
shown that, under definite conditions, this global time-asymmetry can be transferred to local contexts as an energy flow that
points to the same temporal direction all over the spacetime. The aim of this paper is to complete the global and non-entropic
program by showing that our approach is able to account for irreversible local phenomena, which have been traditionally considered
as the physical origin of the arrow of time. 相似文献
98.
Mat Mohamad Nur Hidayat Asmuin Nor Zelawati Md Basir Md Faisal Abbas Tehseen Mohd Kasihmuddin Mohd Shareduwan Goodarzi Marjan 《Journal of Thermal Analysis and Calorimetry》2021,143(3):2343-2354
Journal of Thermal Analysis and Calorimetry - In this paper, a numerical study was performed to examine the effect of divergent nozzle length of single-hose dry ice blasting on the development of... 相似文献
99.