Search results for "Absorption"
showing 10 items of 2701 documents
Exploring the co-loading of lidocaine chemical forms in surfactant/phospholipid vesicles for improved skin delivery
2015
Abstract Objectives The present study was aimed at targeting the skin to deliver lidocaine loaded in surfactant/phospholipid vesicles tailored for improved local delivery. The influence of different formulation parameters was explored to maximise drug efficacy. Methods The vesicles were prepared using a mixture of soy lipids (Phospholipon 50) and a surfactant with penetration-enhancing properties (Oramix CG110, Labrasol, Labrafac PG or Labrafac CC), and loaded with lidocaine. The formulations were analysed in detail by cryo-TEM, SAXS, Turbiscan Lab, and tested in permeation experiments through new born pig skin, as a function of the chemical form and concentration of lidocaine (i.e. free ba…
Excited State Tuning of Bis(tridentate) Ruthenium(II) Polypyridine Chromophores by Push-Pull Effects and Bite Angle Optimization: A Comprehensive Exp…
2013
The synergy of push-pull substitution and enlarged ligand bite angles has been used in functionalized heteroleptic bis(tridentate) polypyridine complexes of ruthenium(II) to shift the (1) MLCT absorption and the (3) MLCT emission to lower energy, enhance the emission quantum yield, and to prolong the (3) MLCT excited-state lifetime. In these complexes, that is, [Ru(ddpd)(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd-NH2 )(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd){(MeOOC)3 -tpy}][PF6 ]2 , and [Ru(ddpd-NH2 ){(EtOOC)3 -tpy}][PF6 ]2 the combination of the electron-accepting 2,2';6',2''-terpyridine (tpy) ligand equipped with one or three COOR substituents with the electron-donating N,N'-dimethyl-N,N'-dipyridin-2-ylpyridin…
Relaxation Dynamics of Cr(acac)3 Probed by Ultrafast Infrared Spectroscopy
2007
Ultrafast infrared spectroscopy is used to probe the dynamics of Cr(acac)3 upon ligand field (400 nm) and charge transfer state (345 nm) excitation. At both pump wavelengths, the ground state absorption bands are strongly bleached at zero delay, and new broad transient absorption bands appear red shifted from the bleached bands. Recovery of ground state bleach is dominated by a fast time constant (15 ps), while a small percentage recovers within 760−900 ps. Despite the extensive studies on Cr(acac)3 photophysics, the fast recovery of the ground state as a major channel is reported here for the first time. As a general result, the present communication emphasizes the great value of ultrafast…
Magnetic ordering in an (Fe0.2Cr0.8)1.5[Cr(CN)6] Prussian blue analogue studied with synchrotron radiation based spectroscopies
2018
The appearance of magnetic order in the (Fe0.2Cr0.8)1.5[Cr(CN)6]·15H2O Prussian blue analogue at low temperature has been investigated by means of synchrotron radiation-based X-ray absorption spectroscopy and X-ray magnetic circular dichroism. With the help of ligand field multiplet analysis we have been able to identify the oxidation states of the metallic cations present in the sample and their evolution with temperature. Our experiments reveal that the appearance of ferromagnetic order is triggered by the transformation of CrIII cations to CrII high-spin caused by a transfer of electrons from the Fe to the Cr resulting in an increase of the magnetic interactions within the (Cr, Cr) subla…
Low-temperature optical absorption of nickel fluosilicate crystals
1964
Abstract The vibronic absorption spectrum of the Ni++ ion in an electric field of trigonal (nearly cubic) symmetry at temperatures down to 4°K is reported and analysed in terms of ligand field and vibronic theory. The positions, widths, shapes and strengths of the bands are satisfactorily explained, together with their associated fine structures. In particular, the complex structure of the red band is well explained in detail as a consequence of the mutual perturbation of the 1E and 3T4 levels, which strongly modifies the vibronic coupling and results in two fairly narrow bands, each showing resolved vibrational structure, superposed on a broad band. A Trees correction term, αL(L+1), helps …
Excited-state lifetimes of [Fe (bipy)3]2+ and [Fe(phen)3]2+
1990
Abstract In the low-spin [Fe(bipy)3]2+ (bipy = 2,2′,bipyridine) and [Fe(phen)3]2+ (phen = 1,10-phenanthroline) complexes an excited high-spin 5T2 ligand field state can be populated by irradiating into the 1MLCT absorption band at 530 nm. The lifetimes of this excited state at low temperatures are reported for [Fe(bipy)3]2+ doped into [Zn(bipy)3] (PF6)2 and [Zn(bipy)3] (BF4)2 and for [Fe(phen)3]2+ and [Fe(bipy)3]2+ embedded in the ion exchange polymer Nafion. For [Fe(bipy)3]2+ in [Zn(bipy)3](PF6)2 the observed lifetimes decrease from 1600 ns at 10 K to 14 ns at 125 K.
Spectroscopic investigations of matrix effects induced by silicate xerogels prepared by the sol-gel method on the entrapped Cr(NCS) 6 3− ions
1999
Abstract Time- and temperature-resolved electronic absorption end emission spectra of silicate xerogels made via the sol-gel technique and doped with K 3 [Cr(NCS) 6 ] have been obtained. These results, along with excited states lifetime measurements, document an unexpected colour change of the entrapped chromium complex from violet to green. By varying the conditions of the doped xerogels preparation, it has been shown that the observed colour transition can not be attributed to ligand exchange with NH 3 or water molecules. On the other hand, the oxygen-rich network of silicate xerogels might be responsible for the observed behaviour. It has been shown that dimethylsulfoxide (DMSO), while d…
Light Dark Matter Search with Ionization Signals in XENON1T
2019
We report constraints on light dark matter (DM) models using ionization signals in the XENON1T experiment. We mitigate backgrounds with strong event selections, rather than requiring a scintillation signal, leaving an effective exposure of (22±3) tonne day. Above ∼0.4 keVee, we observe <1 event/(tonne day keVee), which is more than 1000 times lower than in similar searches with other detectors. Despite observing a higher rate at lower energies, no DM or CEvNS detection may be claimed because we cannot model all of our backgrounds. We thus exclude new regions in the parameter spaces for DM-nucleus scattering for DM masses mχ within 3–6 GeV/c2, DM-electron scattering for mχ>30 MeV/c2, a…
Absorption and Scattering Microscopy of Single Metal Nanoparticles.
2006
Several recently developed detection techniques opened studies of individual metal nanoparticles (1-100 nm in diameter) in the optical far field. Eliminating averaging over the broad size and shape distributions produced by even the best of current synthesis methods, these studies hold great promise for gaining a deeper insight into many of the properties of metal nanoparticles, notably electronic and vibrational relaxation. All methods are based on detection of a scattered wave emitted either by the particle itself, or by its close environment. Direct absorption and interference techniques rely on the particle's scattering and have similar limits in signal-to-noise ratio. The photothermal …
A theoretical insight into the photophysics of psoralen
2006
Psoralen photophysics has been studied on quantum chemistry grounds using the multiconfigurational second-order perturbation method CASPT2. Absorption and emission spectra of the system have been rationalized by computing the energies and properties of the low-lying singlet and triplet excited states. The S1 ππ* state has been determined to be responsible of the lowest absorption and fluorescence bands and to initially carry the population in the photophysical processes related to the phototherapeutic properties of psoralen derivatives. The low-lying T1 ππ* state is, on the other hand, protagonist of the phosphorescence, and its prevalent role in the reactivity of psoralen is suggested to b…