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11.
Nielsen CB Johnsen M Arnbjerg J Pittelkow M McIlroy SP Ogilby PR Jørgensen M 《The Journal of organic chemistry》2005,70(18):7065-7079
[reaction: see text] The synthesis and characterization of water-soluble singlet oxygen sensitizers with a phenylene-vinylene motif is presented. The principal motivation for this study was to better understand specific features of a water-soluble molecule that influence the photosensitized production of singlet oxygen upon nonlinear, two-photon excitation of that molecule. To achieve water solubility, sensitizers were synthesized with ionic as well as nonionic substituents. In the ionic approach, salts of N-methylated pyridine, benzothiazole, and 1-methyl-piperazine moieties were used, as were aryl-substituted sulfonic acid moieties. In the nonionic approach, aryl-substituted triethylene glycol moieties were used. Selected photophysical properties of the compounds synthesized were determined, including singlet oxygen quantum yields. Of the molecules examined, the most efficient singlet oxygen sensitizers had triethylene glycol units as the functional group that imparted water solubility. Molecules containing the ionic moieties did not make singlet oxygen in appreciable yield nor did they efficiently fluoresce. Rather, for these latter molecules, rapid charge-transfer-mediated non-radiative processes appear to dominate excited state deactivation. 相似文献
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H. J. Byrne L. Akselrod C. Thomsen A. Mittelbach S. Roth 《Applied Physics A: Materials Science & Processing》1993,57(4):299-302
The resonant Raman scattering of C60 crystallites is monitored as a function of excitation intensity at 514.5 nm. At low intensities, a strong line at 1468 cm–1 is observed. No feature at 1459 cm–1 is observable. With increasing intensities, the 1468 cm–1 line shifts continuously and reversibly to lower frequencies. The mode softening is nonlinearly dependent on the input intensity and is accompanied by a nonlinear increase in the Raman intensity. The spectral changes are discussed in terms of a nonlinear reduction in force constant and increase in bond polarisability as a result of an increased intermolecular delocalisation of the -electron cloud. The nonlinear changes are associated with the nonlinear luminescence and photoconductive response observed in fullerenes and are contrasted to the irreversible phototransformation recently discussed. 相似文献
16.
A method for semi-automatic background estimation in energy-dispersive x-ray fluorescence spectra is outlined. Two cubic splines were investigated and the spline called the Butland interpolant was chosen for further investigation. Prior to the calculation of the spline, peak regions are set up, and suitable knots are defined outside the peak regions. To set up the peak regions, an automatic peak-search routine and a calibration equation are used. For a given peak, the latter relates the full width at half maximum (FWHM) to the peak centre. In turn, the size of the peak regions are defined by the FWHM multiplied by a constant given by the user. The method was tested on several types of spectra. It was found that the optimal size of the peak region decreased with increasing peak density. Reproducibility tests showed that the standard deviation of the summation of counts within a peak region and after background subtraction was less than would be expected from the counting statistics. 相似文献
17.
H. Flyger J. Fenger E. Lund Thomsen E. Lewin S. E. Gryning E. Lyck 《Fresenius' Journal of Analytical Chemistry》1976,282(4):297-300
Summary Pertinent, previous studies of the oxidation of SO2 in the atmosphere are briefly reviewed. A project dealing with the conversion in the plume from an oil-fired power station is described in greater detail. Measurements were performed from an aircraft and included continuous registration of NOx, SO2 and ozone concentrations. The possibility of using NOx as an internal tracer is discussed; also the use of the inert tracer SF6 is treated and a special detector for the continuous registration of SF6 in relative concentrations down to 10–6 ppm is described. Preliminary results indicate a half-life for SO2 in the plume of about half an hour.
Umsetzung von Schwefeldioxid in der Atmosphäre
Zusammenfassung Einschlägige frühere Studien über die Oxidation von SO2 in der Atmosphäre werden kurz diskutiert. Ein Projekt zum Studium der Umwandlung im Abrauch eines ölbefeuerten Kraftwerkes wird im Detail beschrieben. Die Messungen wurden mit Hilfe eines Flugzeuges vorgenommen und schließen die kontinuierliche Aufzeichnung von NOx-, SO2- und Ozon-Konzentrationen ein. Die Möglichkeit der Verwendung von NOx als interner Indicator wird diskutiert. Außerdem wird der Gebrauch des inerten Indicators SF6 behandelt und ein spezieller Detektor für die kontinuierliche Aufzeichnung von SF6 mit relativen Konzentrationen bis herunter auf 10–6 ppm beschrieben. Vorläufige Ergebnisse deuten auf eine Halbwertszeit von SO2 im Abrauch von etwa 30 min hin.
Presented at the 6th Annual Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria 相似文献
18.
Watt A Thomsen E Meredith P Rubinsztein-Dunlop H 《Chemical communications (Cambridge, England)》2004,(20):2334-2335
We report a simple one pot process for the preparation of lead sulfide (PbS) nanocrystals in the conjugated polymer poly (2-methoxy-5-(2'ethyl-hexyloxy)-p-phenylene vinylene)(MEH-PPV), and we demonstrate electronic coupling between the two components. 相似文献
19.
Methods are described for the selective bromine-lithium exchange reaction of bromine-substituted calix[4]arenes with either n-BuLi or t-BuLi in THF. Quenching of the lithiated calix[4]arenes with MeOH, D(2)O, CH(3)SSCH(3), B(OCH(3))(3), DMF, or CO(2) as electrophiles resulted in 5-monosubstituted, 5,17-disubstituted, or 5,11,17,23-tetrasubstituted calix[4]arenes with H, D, SCH(3), B(OH)(2), CHO, or COOH functionalities. 相似文献
20.
Measurement of neutral sugars in glycoproteins as dansyl derivatives by automated high-performance liquid chromatography 总被引:3,自引:0,他引:3
Automated high-performance liquid chromatography was used to analyse dansylhydrazine derivatives of neutral sugars in unfractionated acid hydrolysates of four well-characterized glycoproteins: fetuin, ovalbumin, alpha-1-acid glycoprotein and bovine submaxillary mucin. After a simple single-step derivatization at 65 degrees C the sugar derivatives in protein hydrolysates chromatographed as single peaks on reversed-phase C18 columns. The isocratic solvent consisted of 20% (v/v) aqueous acetonitrile containing 0.01 M formic acid, 0.04 M acetic acid and 0.001 M triethylamine. The triethylamine significantly increases the sugar peak height at 254 nm. Repeated automatic sample injection without deterioration of column performance or interference from dansyl hydrazine is not possible with published methods, but was achieved by cleaning the column between each analysis with a solvent of 20% (v/v) acetonitrile and 80% (v/v) methanol. Hydrolysis with 2 M trifluoroacetic acid is superior to 2 M hydrochloric acid for both sugar recovery and convenience but must continue for 6-8 h at 105 degrees C to ensure complete sugar release. We confirmed that mannose is present in most preparations of human high-molecular-weight salivary glycoproteins, and also examined purified bovine skin proteodermatan sulphate. p-Nitrophenylhydrazine derivatives of neutral sugars are readily produced, but do not chromatograph as successfully as the dansyl derivatives while phenylhydrazine derivatives are not easily produced at 65 degrees C. Further development of the method should be possible by producing other hydrazine derivatives of neutral sugars. 相似文献