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41.
The nonlinear refractive index n2 of silica fiber (24 m) and erbium-doped fiber (10 m) is measured to within an accuracy of 5% by use of time-delayed photorefractive beam coupling of intense 53-ps, 1.064-microm pulses that experience self-phase modulation in the fibers. The resultant induced grating autocorrelation response yields a value of n2/A(eff) and a calibration standard for the fiber. A phase shift of the order of 0.19pi can be detected and is limited only by laser amplitude fluctuations. A unique advantage of this technique is its ability to measure n2 accurately in short lengths (z < or = 25 m) of fiber, whereas other approaches typically use much longer lengths of fiber (z > or = 100 m). 相似文献
42.
Both hydrophobic and hydrophilic room-temperature ionic liquids can be separated from aqueous solutions with relatively low-pressure gaseous carbon dioxide. 相似文献
43.
Abstract— Semimethylene blue was generated by reductive quenching of triplet methylene blue, 3MBH2+, with diphenylamine at pH 0.62–3.4. A Q-switched ruby laser flash-photolysis-kinetic spectro-photometric apparatus was used to characterize the absorption spectrum of semimethylene blue from 350 to 900 nm and a number of physical constants at 25°C with μ= 0.4 M and Cl? as the anion. The specific rate of quenching of 3MBH2+ by DPA is 2.8 × 109M?1 s?1 in 5% EtOH-95% water and 1.2×109M?1 s?1 in 50 v/v% aq. CH3CN. Corresponding efficiencies of net electron transfer are, respectively, 0.15 and 0.62. Spectral characteristics in 5% EtOH are, for MBH22±, λmax= 375 nm, ε375= 9000 M?1 cm?1; λmax= 880 nm, ε880= 12700 M?1 cm?1; for MBH±, λmax= 410 nm, ε410= 9800 M?1 cm?1, λmax= 880 nm, ε880= 33000 M?1 cm?1; for MBH± in 50 v/v% AN, λmax= 400 nm, ε400= 11000 M?1 cm?1 and λmax= 880 nm,ε880= 39000 M?1 cm?1. The pKa of MBH22ε calculated from the pH dependence of the absorption spectrum is 1.86 × 0.04 in 5% EtOH and 1.15 in 50 v/v% AN. Rate constants, kdecay, for reaction DPAH±+ with MBH22ε and MBH± in 5% EtOH are, respectively, 3.9 × 109 and 9.5 × 109M?1 s?1. The value of pKa of MBH22ε calculated from the dependence of kdecay on pH is 1.75 in 5% EtOH. 相似文献
44.
Medha Rele Sudhir Kapoor Shweta Hedge Sergej Naumov Tulsi Mukherjee 《Research on Chemical Intermediates》2006,32(7):637-645
Many photo-physical studies have been reported for the detection of Hg2+ ions. Here we present the effect of Hg
2
2+
ions on the absorption and fluorescence of indole-2-carboxylic acid (I2C). Experimental evidence, supported by density functional
theory B3LYP/LANL2DZ/PCM, for the formation of a I2C-Hg
2
2+
complex, is reported for the first time. It was observed that I2C forms a ground-state complex with Hg
2
2+
ions in a ratio of 3:1. The possibility of I2C to be used as a selective novel chemical sensor for the spectrophotometric
detection of mercurous ions is described. 相似文献
45.
Vaisakh Mohan A. Nijamudheen Sudhir Kumar Das Prabhat K. Sahu Usha Pallabi Kar Dr. Abdur Rahaman Dr. Moloy Sarkar 《Chemphyschem》2012,13(17):3882-3892
A new multi‐component chemosensor system comprising a naphthalimide moiety as fluorophore is designed and developed to investigate receptor–analyte binding interactions in the presence of metal and non‐metal ions. A dimethylamino moiety is utilized as receptor for metal ions and a thiourea receptor, having acidic protons, for binding anions. The system is characterized by conventional analytical methods. The absorption and fluorescence spectra of the system consist of a broad band typical for an intramolecular charge transfer (ICT). The effects of various metal‐ion additives on the spectral behavior of the present sensor system are examined in acetonitrile. It is found that among the metal ions studied, alkali/alkaline earth‐metal ions and transition‐metal ions modulate the absorption and fluorescence spectra of the system. As an additional feature, the anion signaling behavior of the system in acetonitrile is studied. A decrease in fluorescence efficiency of the system is observed upon addition of fluoride and acetate anions. Fluorescence quenching is most effective in the case of fluoride ions. This is attributed to the enhancement of the photoinduced electron transfer from the anion receptor to the fluorophore moiety. Hydrogen‐bond interactions between the acidic NH protons of the thiourea moiety and the F? anions are primarily attributed to the fluoride‐selective signaling behavior. Interestingly, a negative cooperativity for the binding event is observed when the interactions of the system are studied in the presence of both Zn2+ and F? ions. NMR spectroscopy and theoretical calculations are also carried out to better understand the receptor–analyte binding. 相似文献
46.
Photochemical α-bromination of ketones using N-bromosuccinimide: a simple, mild and efficient method
Aromatic and aliphatic carbonyl compounds undergo facile bromination with N-bromosuccinimide under UV-vis irradiation to give the corresponding α-brominated ketones in good yields, at low temperatures (30 °C), without any catalyst, catalyst support or radical initiator and within a short time. 相似文献
47.
AbstractChitosan (CS) is being used for fabrication of low cost, biocompatible materials that have applicability in fields such as agriculture, biotechnology and environment. In Environmental research, one of the applications of CS based hydrogel composites are in form of biosorbents for eviction of toxic dyes, heavy metals and nutrients from effluent streams. The adsorption potential could be attributed to the reactive functional groups existing on the surface of CS. CS based materials can also be employed for oil/water separation, as a fertilizer carrier, in Microbial fuel cells as Electrolyte membrane and as Electrochemical/Biosensors for detecting and analyzing few environmental pollutants such as pesticides. The earlier review papers on the subject matter have concentrated mainly on dye and heavy metal removal without giving details of its utility in the field of electrochemistry and agriculture. Though the biopolymer holds numerous applications, it has not been discussed extensively. Thus, an attempt has been made to elucidate the current and potential applications of CS hydrogels and composites based on the efficacy it has shown in areas of removal of organic and inorganic contaminants such as dyes, heavy metals and nutrients, in agriculture, oil and water separation, Microbial Fuel cells and Electrochemical/Biosensors.
- HIGHLIGHTS
Chitosan based hydrogel composites could be extensively used in the field of Environment Technology.
The composites act as effective biosorbents for dye, heavy metal and nutrient removal because of the functional groups present on Chitosan’s surface.
These can also be effectively used for oil/water separation and also as a fertilizer/pesticide carrier for their slow release.
Chitosan based electrolytes can become a promising ecofriendly substitute for synthetic polymers in fuel cells.
These biopolymers have also been researched upon as electrochemical/biosensors in recent years for detecting environmental pollutants.
48.
Spectroscopic studies on the mode of interaction of an anticancer drug with bovine serum albumin 总被引:3,自引:0,他引:3
The mechanism of interaction of vinblastin sulphate (VBS) with bovine serum albumin (BSA) has been reported. Association constant for VBS-BSA binding was found to be 3.146+/-0.06 x 10(4) M(-1). Stern-Volmer analysis of fluorescence quenching data showed that the fraction of fluorophore (protein) accessible to the quencher (drug) was close to unity indicating thereby that both tryptophan residues of BSA are involved in drug-protein interaction. The rate constant for quenching, greater than 10(10) M(-1) S(-1), indicated that the drug-binding site is in close proximity to tryptophan residues of BSA. Binding studies in the presence of an hydrophobic probe, 8-anilino-1-naphthalein-sulphonic acid, sodium salt (ANS) indicated that there is hydrophobic interaction between VBS and probe and they do not share common sites in BSA. Thermodynamic parameters obtained from data at different temperatures showed that the binding of VBS to BSA involves predominant hydrophobic forces. The effects of some additives and paracetamol on binding of VBS-BSA have also been investigated. The CD spectrum of BSA in presence of VBS shows that the binding of VBS leads to change in the helicity of BSA. 相似文献
49.
50.
In this study, it is demonstrated that silver nanoparticles can be transferred from formamide to chloroform using oleic acid as a phase transfer agent with a transfer efficiency of 90–95%. The silver nanoparticles are initially formed as an organosol by the reduction of silver ions with formamide. On aging the complex, the particles self-assemble to form an ordered close-packed two-dimensional array of silver nanocrystals when dissolved in CHCl3. The size distribution of the colloidal silver particles after transfer in different solvents remains almost the same. On the basis of IR spectroscopy, we discuss the adsorption of oleic acid over the silver particles. 相似文献