Search results for "MOLECULE"
showing 10 items of 5162 documents
Multi-photon imaging of amine-functionalized silica nanoparticles.
2012
A convenient and simple strategy for preparing water soluble, photoluminescent functionalized silica nanoparticles (M-dots) in the absence of fluorophores or metal doping is demonstrated. These M-dots can be used for bioimaging using one and two-photon microscopy. Because of their high photostability, low toxicity and high biocompatibility compared with Lumidot™ CdSe/ZnS quantum dots, functionalized silica particles are superior alternatives for current bioimaging platforms. Moreover, the presence of a free amine group at the surface of the M-dots allows biomolecule conjugation (e.g. with antibodies, proteins) in a single step for converting these photoluminescent SiO(2) nanoparticles into …
Solution processable 2-(trityloxy)ethyl and tert-butyl group containing amorphous molecular glasses of pyranylidene derivatives with light-emitting a…
2015
Abstract Small organic molecules with incorporated 4 H -pyran-4-ylidene (pyranylidene) fragment as the π-conjugation system which bonds the electron acceptor fragment (A) with electron donor part (D) in the molecule – also well known as derivatives of 4-(dicyano-methylene)-2-methyl-6-[p-(dimethylamino)styryl]-4H-pyran ( DCM ) laser dye-have attracted considerable attention of scientists as potential new generation materials for organic photonics and molecular electronics due to their low-cost fabrication possibility, flexibility and low-weight. Six glassy derivatives of 4 H -pyran-4-ylidene (pyranylidene) with attached bulky 2-(trityloxy)ethyl and tert -butyl groups are described in this re…
Single molecule spectroscopy of multichromophoric assemblies
2003
We have investigated multichromophoric assemblies composed of a variable number of chromophores by single molecule spectroscopy. Specific spectral signatures have allowed to distinguish at the single molecule level between molecular dimers representing strong and weak electronic dipole-dipole coupling. By using fluorescence excitation spectroscopy at low temperature, the sharp purely electronic zero-phonon lines of single chromophores within a single dendrimer containing four chromophores could be isolated in the frequency domain.
Influence of Outer-Sphere Anions on the Photoluminescence from Samarium(II) Crown Complexes.
2021
Three samarium(II) crown ether complexes, [Sm(15-crown-5)2]I2 (1), [Sm(15-crown-5)2]I2·CH3CN (2), and [Sm(benzo-15-crown-5)2]I2 (3), have been prepared via the reaction of SmI2 with the corresponding crown ether in either THF or acetonitrile in good to moderate yields. The compounds have been characterized by single crystal X-ray diffraction and a variety of spectroscopic techniques. In all cases, the Sm(II) centers are sandwiched between two crown ether molecules and are bound by the five etheric oxygen atoms from each crown ether to yield 10-coordinate environments. Despite the higher symmetry crystal class of 1 (R3c), the samarium center resides on a general position, whereas in 2 and 3 …
Parity violation energy of biomolecules - III: RNA
2006
The energy of parity-violation associated with a typical DNA double helix is estimated with ab initio techniques. It is shown that weak-nuclear interactions do not favor the formation of the double helices found in nature. Possible implications regarding the potential effect of parity-violation interactions on the evolution of biological homochirality are discussed.
Structure and dynamics of amorphous polymers: computer simulations compared to experiment and theory
2004
This contribution considers recent developments in the computer modelling of amorphous polymeric materials. Progress in our capabilities to build models for the computer simulation of polymers from the detailed atomistic scale up to coarse-grained mesoscopic models, together with the ever-improving performance of computers, have led to important insights from computer simulations into the structural and dynamic properties of amorphous polymers. Structurally, chain connectivity introduces a range of length scales from that of the chemical bond to the radius of gyration of the polymer chain covering 2–4 orders of magnitude. Dynamically, this range of length scales translates into an even larg…
KINETICS OF POLYMER EJECTION FROM CAPSID CONFINEMENT: SCALING CONSIDERATIONS AND COMPUTER EXPERIMENT
2012
We investigate the ejection dynamics of a flexible polymer chain out of confined environment by means of scaling considerations and Monte Carlo simulations. Situations of this kind arise in different physical contexts, including a flexible synthetic polymer partially confined in a nanopore and a viral genome partially ejected from its capsid. In the case of cylindric confinement the entropic driving force which pulls the chain out of the pore is argued to be constant once a few persistent lengths are out of the pore. We demonstrate that in this case the ejection dynamics follows a [Formula: see text]-law with elapsed time t. The mean ejection time τ depends nonmonotonically on chain length…
Intensities and electronic transition strengths of seven Te2 visible and i.r. band systems
1992
Abstract We present an experimental study of relative intensity distributions in the laser-flourescence spectra of the AO+u-XO+g, AO+u-X1g, AO+u-b1∑+g, A1-u-X1-g, BO+u-XO+g, BO+u-X1g, and BO+u-b1∑+g systems of the 130Te2 molecule. Effective internuclear potentials have been determined by applying the RKR-procedure and accounting for rovibronic interaction. Franck-Condon factors and r-centroids have been calculated and tabulated. By combining expiremental results and calculations, we obtain the dependence of the electronic transition strength on internuclear distance in the r-centroid approximation. Normalization over the lifetimes of the rovibronic levels of the excited electronic states en…
Polymer dynamics in time-dependent periodic potentials.
2008
Dynamics of a discrete polymer in time-dependent external potentials is studied with the master equation approach. We consider both stochastic and deterministic switching mechanisms for the potential states and give the essential equations for computing the stationary state properties of molecules with internal structure in time-dependent periodic potentials on a lattice. As an example, we consider standard and modified Rubinstein-Duke polymers and calculate their mean drift and effective diffusion coefficient in the two-state non-symmetric flashing potential and symmetric traveling potential. Rich non-linear behavior of these observables is found. By varying the polymer length, we find cur…
Counterion-Mediated Crossing of the Cyanine Limit in Crystals and Fluid Solution: Bond Length Alternation and Spectral Broadening Unveiled by Quantum…
2020
Absorption spectra of cyanine⊕·Br⊖ salts show a remarkable solvent dependence in non/polar solvents, exhibiting narrow, sharp band shapes in dichloromethane but broad features in toluene; this chan...