共查询到20条相似文献,搜索用时 15 毫秒
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V. V. Ryl'kov 《Theoretical and Experimental Chemistry》1969,5(3):224-226
Analytic expressions are derived for the rate constants of some two-quantum photochemical reactions. The limits of application of the approximations are discussed. It is shown that the quantum yield in two-photon sensitization (second photon absorbed by a molecule in a triplet state) is independent of the sensitizer when the substrate concentration is high. The concept of quantum yield for a nonlinear reaction is discussed.We are indebted to V. E. Kholmogorov for guidance in this work and to our colleagues for discussion of the results. 相似文献
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Photochemical reactions in the solid state can be scaled up from a few milligrams to 10 grams by using colloidal suspensions of a photoactive molecular crystal prepared by the solvent shift method. Pure products are recovered by filtration, and the use of H(2)O as a suspension medium makes this method a very attractive one from a green chemistry perspective. Using the photodecarbonylation of dicumyl ketone (DCK) as a test system, we show that reaction efficiencies in colloidal suspensions rival those observed in solution. [reaction: see text] 相似文献
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Landgraf S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(10):2029-2048
Semiconductor light sources, like laser diodes or ultrabright light emitting diodes, are widely used in optical spectroscopy. In this presentation an overview of applications in photochemistry is given. Since the beginning of the 1990s an increasing number of publications with the application of semiconductor light sources appeared. Three different techniques were used: single photon counting with short pulses, phase-modulation fluorometry using a conventional modulation spectrometer, or a lock-in amplifier. Using continuous wave laser diodes in the visible region, which are available from 690 to 630 nm (and, recently, down to 400 nm), a new compact fluorescence spectrometer was developed in our laboratory. Using the phase fluorometric method, measurements down to 100 ps are now possible. Values can be measured in steps of 10 ps with good reproducibility using a high-frequency signal generator and a GHz digital storage oscilloscope. Several investigations have been carried out applying this technique including time-resolved detection of crude oil as an example for possible practical applications. 相似文献
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A. C. Bhasikuttan A. V. Sapre L. V. Shastri 《Journal of photochemistry and photobiology. A, Chemistry》1995,90(2-3):177-182
The reactions of two triphenyl methane (TPM) dyes—crystal violet (CV+) and malachite green (MG+)—with N3• and OH• radicals were studied by pulse radiolytic kinetic spectrophotometry. The rate constants for the reaction of the cationic dyes (D+) with N3• are (9.0±0.6)×109 and (3.0±0.2)×109 dm3 mol−1 s−1 respectively and those for the reaction with OH• are obtained as (8.0±0.6)×109 and (1.1±0.1)×109 dm3 mol−1 s−1 respectively. The transient spectra resulting from the oxidation of the dyes were characterized. The time-resolved spectra indicate that the reaction with OH• radicals initially generates an adduct which subsequently dissociates to form the radical dication D•2+. The D•2+ species decay by further reaction with the parent dye. 相似文献
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A simply fabricated microfluidic device using a green organic light emitting diode (OLED) and thin film interference filter as integrated excitation source is presented and applied to fluorescence detection of proteins. A layer-by-layer compact system consisting of glass/PDMS microchip, pinhole, excitation filter and OLED is designed and equipped with a coaxial optical fiber and for fluorescence detection a 300 microm thick excitation filter is employed for eliminating nearly 80% of the unwanted light emitted by OLEDs which has overlaped with the fluorescence spectrum of the dyes. The distance between OLED illuminant and microchannels is limited to approximately 1 mm for sensitive detection. The achieved fluorescence signal of 300 microM Rhodamine 6G is about 13 times as high as that without the excitation filter and 3.5 times the result of a perpendicular detection structure. This system has been used for fluorescence detection of Rhodamine 6G, Alexa 532 and BSA conjugates in 4% linear polyacrymide (LPA) buffer (in 1 x TBE, pH 8.3) and 1.4 fmol and 35 fmol mass detection limits at 0.7 nl injection volume for Alexa and Rhodamine dye have been obtained, respectively. 相似文献
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The appearance of malachite green dye absorption following photoionization of malachite green leucocyanide has been examined using picosecond flash photolysis. The rate of absorption increase depends upon solvent viscosity and exhibits a two-step behavior in viscous glycerol solutions. 相似文献
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N - [2,2,2,-Trifluoro - 1 - trifluoromethyl(ethylidene)] - thiocarboxamides react with tetracyanoethylene to give [4,4, - bis(trifluoromethyl) - 4H - 1,3,5 - thiadiazin - 2 - yl]ethylenetricarbonitriles and 1,2 - bis[4,4 - bis(trifluoromethyl) - 4H - 1,3,5 - thiadiazin - 2 - yl]ethylenedicarbonitriles. The spectral data of the new compounds are discussed (IR, 1H NMR, 19F NMR and 13C NMR). 相似文献
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Namiki K Sakamoto A Murata M Kume S Nishihara H 《Chemical communications (Cambridge, England)》2007,(44):4650-4652
A 3-ferrocenylazobenzene monolayer on an ITO electrode exhibits reversible azobenzene isomerization using a single green light source, assisted by electrochemical control of the ferrocene redox state. 相似文献
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Methanol-swollen Nafion beads were used as microreactors to control the photochemical reaction pathways. Product selectivity in three unimolecular reactions, namely, the photo-Fries rearrangement of naphthyl esters, Norrish Type I reaction of 1-phenyl-3-p-tolyl-propan-2-one and Norrish Type I and Type II reactions of benzoin alkyl ethers were examined. The influence of cations over the photodimerization of acenaphthylene and cross-photodimerization between acenaphthylene and N-benzyl maleimide included within Nafion were also examined. The photochemical behaviors of the above substrates were significantly altered within Nafion compared with their solution photochemistry. Of particular interest, the product distributions were found to depend on the counter cations of Nafion. 相似文献
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Rabie Abdelrahman M. Abukhadra Mostafa R. Rady Ahmed M. Ahmed Sayed A. Labena Ahmed Mohamed Hussein S. H. Betiha Mohamed A. Shim Jae-Jin 《Research on Chemical Intermediates》2020,46(3):1955-1973
Research on Chemical Intermediates - Nano-ZnO and Co–ZnO supported algae (Sargassum species) were synthesized as a novel composite of promising photocatalytic activities in decolorization of... 相似文献
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The fluorescence kinetics and polarization anisotropy of the triphenylmethane dye malachite green were measured as a function of solvent viscosity. The relationshp between the relaxation kinetics and the solvent viscosity was investigated in order to obtain information on the effect of enviromnental changes on the orientational order of dye molecules in solution. It was found that the fluorescence lifetimes follow an η dependence for 1 < η < 60 P, η dependence for 60 P < η < 1000 P and approach a constant for η > 1000 P. The dependence of the fluorescence decay rates on the solvent viscosity was fit to k = 5 × 1010η? + 5 × 108 s?1. The fluorescence polarization anisotropy term, R(0), was also measured as a function of solvent viscosity. A marked decrease in R(0) was observed at a viscosity of 1000 P. For η < 1000 P, R(0) was found to be close to the expected value for a random distribution of molecules, 0.4; and for η > 3000 P, R(0) was measured to be ≈0.11. This small value of R(0) may indicate a nonrand The observed change of the polarization anisotropy with increasing viscosity indicates that the dye molecules become ordered at higher viscosities. This may arise through the formation of a long range order due to lack of rotational deexcitation of the malachite green dye molecules at high viscosities. 相似文献
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P. P. Levin N. L. Zaichenko A. S. Tatikolov A. I. Shienok L. S. Kol’tsova I. M. Shcherbakova O. Yu. Os’kina I. R. Mardaleishvili A. O. Ait A. A. Berlin 《High Energy Chemistry》2016,50(4):259-265
Using the method of microsecond flash photolysis with UV and visible light, the spectral and kinetic characteristics of intermediate products of photolysis in toluene and methanol solutions of a new biphotochromic compound have been studied, in which two photochromic moieties, spironaphthoxazine and azomethine, are linked to each other in such a way that there is conjugation between π-electronic systems of the moieties in the ground state of the molecule. Two intermediate products have detected, whose relative efficiency of formation substantially depends on the solvent and the wavelength of excitation light. 相似文献
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Ferraz RC Fontana CR Ribeiro AP Trindade FZ Bartoloni FH Baader JW Lins EC Bagnato VS Kurachi C 《Journal of photochemistry and photobiology. B, Biology》2011,103(2):87-92
The photodynamic therapy (PDT) is a combination of using a photosensitizer agent, light and oxygen that can cause oxidative cellular damage. This technique is applied in several cases, including for microbial control. The most extensively studied light sources for this purpose are lasers and LED-based systems. Few studies treat alternative light sources based PDT. Sources which present flexibility, portability and economic advantages are of great interest. In this study, we evaluated the in vitro feasibility for the use of chemiluminescence as a PDT light source to induce Staphylococcus aureus reduction. The Photogem? concentration varied from 0 to 75 μg/ml and the illumination time varied from 60 min to 240 min.The long exposure time was necessary due to the low irradiance achieved with chemiluminescence reaction at μW/cm2 level. The results demonstrated an effective microbial reduction of around 98% for the highest photosensitizer concentration and light dose. These data suggest the potential use of chemiluminescence as a light source for PDT microbial control, with advantages in terms of flexibility, when compared with conventional sources. 相似文献
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Luminescence measurements after laser pulse excitation are reported for the dye malachite green in solutions of different viscosity with a time resolution of 10 ps. 相似文献
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The standard tungsten-halogen light source used in a commercial evaporative light scattering detector (ELSD) was replaced
with a 180 W xenon arc lamp. The xenon arc lamp possesses a broader spectrum in the UV region than the halogen source. The
influence of the UV transmittance of five selected solvents was studied with a size-exclusion chromatography column. This
solvent parameter was not observed to influence the ELSD response between the two light source settings. With the solvents
studied, better sensitivity was obtained with the xenon arc lamp than the halogen lamp. This high-energy source was applied
to ceramide III analysis with an octadecyl-grafted silica column and methanol:tetrahydrofuran 97:3 as the mobile phase, and
the sensitivity of the quantification of ceramide III increased 16-fold for injected amounts of 14∼140 ng. The molecular species
in a sample of naturally occurring ceramides was analyzed using two C18 columns at 40 °C and gradient elution from 100% acetonitrile
to 100% isopropanol in 30 min. The increased ELSD sensitivity achieved when using the xenon arc lamp allowed both the minor
and major ceramide species to be observed, in contrast to the results achieved when the halogen lamp was used, where the increased
photomultiplier voltage needed to observed the signals from the minor species caused the signals from the major ceramide species
to occur above the detector response window. 相似文献
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研究以双特异性核酸适配体A3作为传感探针、纳米金(AuNPs)为指示剂、NaCl溶液为聚集诱导剂,构建了一种新型的免标记AuNPs比色生物传感器,可实现水产品中孔雀石绿(MG)和无色孔雀石绿(LMG)的同步、快速、可视化检测。该方法的检测原理是核酸适配体A3对MG和LMG有双特异性识别能力,可作为MG和LMG理想的识别受体。它可通过静电作用吸附到AuNPs表面,保护AuNPs并抑制高盐溶液诱导的聚集,AuNPs溶液颜色不变,即为红色;当加入靶标MG或LMG后,该核酸适配体能够与靶标特异性结合,并从AuNPs表面上解离,AuNPs失去保护作用而在高盐溶液诱导下发生聚集,溶液颜色由红变蓝。根据颜色变化,可通过肉眼定性或通过光谱仪定量分析MG和LMG的残留量。该方法首先将50μL的核酸适配体A3(终浓度150 nmol/L)与150μL的AuNPs(终浓度1.25 nmol/L)混合,室温孵育6 min。随后加入50μL待测液,室温孵育30 min。最后加入50μL NaCl(终浓度150 mmol/L), 4 min后观察溶液颜色变化,并分别测定MG和LMG在520 nm和650 nm下的... 相似文献
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P. P. Levin N. L. Zaichenko A. I. Shienok L. S. Kol’tsova I. R. Mardaleishvili A. S. Tatikolov 《High Energy Chemistry》2011,45(2):147-151
Spectral and kinetic characteristics of photolysis products in methanol of the photobifunctional compound, whose molecule
contains the photochromic spironaphthopyran fragment as well as the hydroxynaphthylmethylenimine fragment in which intramolecular
proton transfer can occur in the ground and excited states of the molecule, were studied by the method of nanosecond laser
photolysis with excitation with light of wavelengths 337, 430, and 470 nm. The relative quantum yields of the formation of
different photoproducts and their kinetic characteristics were measured. The dependence of the relative yield of the photoproducts
of different nature on the wavelength of excitation light was revealed. 相似文献