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101.
A.?Costela I.?García-Moreno C.?Gómez O.?GarcíaEmail author R.?Sastre 《Applied physics. B, Lasers and optics》2004,78(5):629-634
The effect on the lasing photostability of Rhodamine 6G (Rh6G), and the rigidity of a hybrid inorganic-organic matrix by controlled addition of di-, tri- and tetrafunctionalized alkoxides has been evaluated. The dye was incorporated into hybrid matrices of (2-hydroxyethyl methacrylate) (HEMA) or vol/vol copolymers of methyl methacrylate (MMA) and HEMA with different weight proportions of polycondensated dimethyldiethoxysilane (DEOS), methyltriethoxysilane (TRIEOS), and tetraethoxysilane (TEOS). The laser samples were transversaly pumped at 534 nm at 5.5 mJ/pulse and up to a 10 Hz repetition rate. The dependence of the laser photostability on organic-inorganic composition, pH of the medium, and thermal treatment of the samples was studied. Good stability, with a drop of the initial laser output of only 13% after 10000 pump pulses at 10 Hz in a thermally postcured (HEMA-15 wt%TRIEOS) matrix was obtained. Careful control of the synthesis process is required to reach the necessary photostability for a solid-state dye laser based on hybrid matrices to become competitive with liquid dye lasers. PACS 81.05.Lg; 81.05.Zx; 81.20.Fw; 42.55.Mv; 42.55.Rz; 42.60.Lh; 42.62.b; 42.70a; 42.70-Hj; 42.70.Jk 相似文献
102.
A. Costela I. García-Moreno C. Gómez O. García R. Sastre 《Applied physics. B, Lasers and optics》2002,75(8):827-833
We report on the laser action of rhodamine 6G (Rh6G) incorporated into new hybrid organic–inorganic monolithic materials.
The synthesis of these materials proceeded via the simultaneous sol-gel process of the inorganic part (tetraethoxysilane or
tetramethoxysilane) and the free-radical polymerization of an organic monomer part (2-hydroxypropyl methacrylate, 2-hydroxyethyl
methacrylate and a 1:1 v/v copolymer of this monomer with methyl methacrylate). The wt. % proportion of the alkoxide was systematically
varied in each organic formulation, and the effect of each organic–inorganic composition on the lasing properties of Rh6G
was evaluated. The laser samples were transversely pumped and the influence on the laser action of dye concentration, pump
wavelength and pump repetition rate was analyzed. Lasing efficiencies of up 26% and good stabilities, with a 90% drop in the
initial laser output of up to 12000 pump pulses at 2.5 Hz, were obtained when the samples were pumped at 355 nm with 5.5 mJ/pulse
from the third harmonic of a Q-switched Nd:YAG laser.
Received: 31 July 2002 / Revised version: 14 October 2002 / Published online: 20 December 2002
RID="*"
ID="*"Corresponding author. Fax: +34-91/564-4853, E-mail: ogarcia@ctp.csic.es 相似文献
103.
J. L. Mateo P. Bosch F. Catalina R. Sastre 《Journal of polymer science. Part A, Polymer chemistry》1992,30(5):829-834
A photocalorimetric study of butyl and lauryl acrylates (BA and LA) polymerization photoinitiated by several benzophenone derivatives is reported. Molecular weight measurements and end-chain group analysis of the samples are also described and the results are compared with those obtained by dilatometric technique. The role played by the long methylene chain in lauryl acrylate is discussed 相似文献
104.
The protonation constants of 1,2-benzenedicarboxylic acid (phthalic acid) at 25 °C in NaCl and CaCl2 (ionic strengths ranging from 0.1 to 2 mol kg−1) were determined potentiometrically, and the results were analyzed by means of Pitzer equations. The values of the logarithm of the first and second dissociation constants ranged from 2.730 and 4.948 (in 0.101 mol kg−1 NaCl) to 2.449 and 3.984 (in 0.624 mol kg−1 CaCl2), respectively. Tabulated interaction parameters for the inorganic species involved along with salting coefficients estimated from literature allowed the calculation of new interaction parameters for the phthalate-Na+/Ca2+ systems. The specific ion interaction model considered seems to account for the influence of the formation of weak complexes of phthalate with calcium ions on the equilibrium constants. 相似文献
105.
The dissociation equilibria of di(2,4,4-trimethylpentyi) phosphinic acid, mono(2,4,4-trimethylpentyl) phosphinic acid, di(n-octyl)phosphinic acid and mono(n-octyl)phosphinic acid have been studied in ethanol-water mixtures by potentiometric titration at 25 degrees C. These data have been analysed both graphically numerically using the program LETAGROP-ZETA. The obtained pK(a) values have been correlated with the corresponding values in water, determined both indirectly by means of extraction measurements and by estimation using the suitable Hammett equation. 相似文献
106.
A study of the conformation of a series of anancomeric axial and equatorial 2-aryloxy-2-thio-1,3,2λ5-dioxaphosphinanes 2-12 in solution and solid state is reported. In accord to the stereoelectronic theory, aryl thiophosphates substituted with electron-withdrawing (EW) groups will tend to occupy axial positions in chair ring conformations due to the stabilizing endo-anomeric (nπO-σP-X*) hyperconjugative interaction. The antiperiplanar orientation of the orbitals involved in the stereoelectronic interaction is a requirement that is fulfiled in the axial series of compounds when the ring adopts a chair conformation. Therefore, in the equatorial series of thiophosphates, the axial seeking characteristics of aryloxy-EW groups might render the molecule with distortion of the chair conformation. An opposite trend is anticipated for the less axial seeking aryl thiophosphates substituted with electron releasing (ER) groups. A detailed analysis of the 3JHH, 3JPH and 3JCP coupling constants allowed us to conclude that there is no contribution of high energy twist-boat conformations in the equatorial thiophosphates substituted with aryl-EW groups in solution. In consequence, single chair conformations were found in solid state for aryl thiophosphates in both configurations. X-ray geometrical analysis of bond distances and bond angles supports clearly the participation of hyperconjugative endo-anomeric (nπO-σP-OAr*) effect in the stabilization of axial series of compounds and the participation of endo-anomeric (nπO-σPS*) effect in the stabilization of the equatorial thiophosphates in chair conformations. 相似文献
107.
Salvador Ordó?ez Eva Díaz Fernando V. Díez Herminio Sastre 《Reaction Kinetics and Catalysis Letters》2007,90(1):101-106
The deactivation of the Pd/Al2O3 catalyst used for the hydrodechlorination of tetrachloroethylene (TTCE) is caused by both the carbonaceous deposits and by
the hydrogen chloride produced in the reaction. In this work, several regeneration procedures have been tested, concluding
that the best procedure is the leaching with ammonia, followed by calcinations and reduction. This procedure leads to an important
recovery of the initial activity. The catalyst regenerated with this treatment is even less prone to deactivation that the
fresh catalyst. 相似文献
108.
Hossein Kamran Haghighi Mehdi Irannajad Agustin Fortuny Ana Maria Sastre 《Chemical Papers》2018,72(4):955-970
A mathematical model was developed for the germanium-facilitated transport from a medium containing tartaric acid using Alamine 336 as a carrier. Modeling was carried out based on the extraction constant (K ext) obtained from the liquid–liquid extraction (LLX) modeling. The LLX data were achieved from experiments with conditions being Alamine 336 concentrations of 0.1–10% v/v from a solution containing about 1.378 mmol/L Ge (100 mg/L) and tartaric acid as an anionic complexant. The LLX model was attained using the equilibrium-based procedure and fitted to extraction experimental data for various carrier concentrations. This model presented an accurate extraction constant (K ext = 0.02) used in the facilitated transport modeling. The flat sheet supported liquid membrane (FSSLM) experiments were conducted in the condition of 1.378 mmol/L Ge (100 mg/L), tartaric acid concentration of 2.760 mmol/L, 1 M HCl as a stripping phase and various Alamine 336 concentrations in the range of 0–35% v/v. The FSSLM model was developed according to the Fick’s law, the diffusional transport, and equilibrium equations. According to the model, mass transfer and diffusion coefficients for various concentrations of the carrier were found. In addition, the calculated and experimental values had a good correlation with together showing the validity of the model. This model can be used in the further process simulation such as hollow fiber SLMs. 相似文献
109.
Sorption of n-hexane on monodimensional pure silica SSZ-35, CIT-5, ZSM-12, and ZSM-22 zeolites with different pore dimension and on recently synthesized ITQ-29 was studied by IR spectroscopic and computational chemistry methods. Heats of sorption of n-hexane on these zeolites was determined experimentally from the temperature dependence of the intensity of IR bands of sorbed hexane as well as from theoretical calculations. Calculations have shown the different orientations of sorbed hexane molecules inside zeolite channels, which depend on the type of zeolite and loading. At high loadings, ordering of hexane inside the channels is observed due to optimization of sorbate-sorbate and sorbate-zeolite interaction energies. Such ordering is responsible for the increase of the sorption energy. A decrease of the sorption energy upon increasing the pore dimension of zeolite was observed, in agreement with results previously published in the literature. Effects of pore diameter of zeolites and ordering of molecules inside zeolite channels on the sorption energy of hexane are discussed. 相似文献
110.
F. R. Diaz L. H. Tagle F. Garcia R. Sastre M. Conde J. L. Mateo F. Catalina 《Journal of polymer science. Part A, Polymer chemistry》1990,28(12):3499-3511
Several models of monomers, homopolymers, and copolymers containing a photosensitizer group, 4-nitro-1-naphthyl-carbamoyl (NNC), have been synthesized. Synthetic methods are described, in addition to two routes for copolymers preparation. First, the radical copolymerization between monomers with the photosensitizer group built-in and comercial monomers such as styrene and methyl acrylate and, second, polymer modification by nucleophilic reaction between carbonyl group polymer supported and nitro-naphthyl amine. All products were characterized and one of the resulting soluble polymeric photosensitizer and its model compound, were tested as triplet energy donors against trans- stilbene and their Stern–Volmer constants were determined. Results show that the sensitizer efficiency is closer to that of the well known benzophenone sensitizer and higher than that of the acetophenone, while the sensitizer efficiency disminished when the chromophore is bonded to the polymer. 相似文献