Effects of Y(Ⅲ) Ions on the Fluorescence Properties of Ce(Ⅲ) Ion and the Organic Ligands in the Complex

The enhancement effects of Y ( Ⅲ) ions on the fluorescence of Ce ( Ⅲ) in Ce ( Ⅲ)-Y ( Ⅲ)-PMMA (polymethylmethacrylate ) or Ce ( Ⅲ)-Y ( Ⅲ)-PVC (polyvinyl chloride ) complex systems were observed. The influence of Y ( Ⅲ) ions on the emission spectra of PMMA ligands in PMMA-Y ( Ⅲ) and the fluorescent enhance- ment of Y( Ⅲ) on Ce( Ⅲ) emission in PMMA-Ce-Y by Y( Ⅲ) ion were studied. It was also of interest to note that when Y ( Ⅲ) ions were added into PMMA and into bpy(bipyridine ) , respectively , the emission spectrum of PMMA ligands was split into fine structure bands by Y ( Ⅲ) , and the fluorescence intensities of bpy ligands in bpy-Y ( Ⅲ) complexes were considerably increased.

Structure Effect on K Shell Fluorescence Parameters at Bis-4-Bromobenzyl-1,2,4-Triazol-3-Ones

In this study;the effect of the electron density over the Br atoms raising with increasing number of CH_2 group using the results of the K X-ray cross-sections and average fluorescence yields of bromine in quaternary-imidazole ring.In the experimental set-up,50 mCi ^(241) Am source and a collimated Ultra-LEGe detector were used.The electron density on the Br atoms raises according to the number of the CH_2 groups on the contrary of the inductive effect.The decreasing of the X-ray fluorescence parameters is interested with the increasing the electron density of Br atoms.

Effects of water chemistry and concentrations of dissolved organic matter on its fluorescence characteristics and molecular conformation

Previous studies showed that water chemistry and concentrations of dissolved organic matter (DOM) could affect its molecular conformation and binding characteristics with hydrophobic organic contaminants (HOCs). However, the conformational change of DOM resultant from water chemistry and concentrations of DOM was not extensively investigated; therefore, the contradictory reports regarding the binding property with HOCs were available in literature. In this study, the effects of ionic strength, pH and DOM concentrations on the fluorescence properties of two humic acids (HA), namely Fluka HA and Amherst HA, were investigated by three-dimensional excitation-emission matrix fluorescence spectroscopy (3DEEM) and steady-state fluorescence polarization (FP) techniques. The results not only corroborated previous observations obtained by other investigators, but revealed some new information about the fluorescence properties and molecular conformation of the humic acids under different water chemistry and DOM concentration conditions, which could shed light on its binding mechanisms and binding properties with HOCs.

Influence enhancement effect of bi-frequency ultrasonic irradiation by TA fluorescence method

Based on a previous research of cavitation effect under bi-frequency ultrasound irradiation, this paper studies bi-frequency irradiations with similar experimental settings. The additional irradiation sources with frequencies of 1.04MHz, 0.8MHz and 1.7MHz are individually combined with the main ultrasonic irradiation source with frequency of 28kHz to form bi-frequency ultrasonic irradiation. The intensity of 28kHz irradiation was fixed at 12.5W/cm^2, while the intensity of the ultrasound at the other three frequencies is varied from1 W/cm^2 to 18 W/cm^2. It turns out that under the influence of the bi-frequency irradiation, the fluorescence intensity is obviously greater than the sum of those at individual frequencies. So the frequency of the additional sonication strikingly influences the fluorescence enhancement effect. For example, the fluorescence enhancement effect of 1.04MHz is stronger than that of 1.7MHz, and the enhancement effect of 0.8MHz is further stronger than that of 1.04MHz. Under the sonic intensity of (7.9)W/cm^2, the fluorescence intensity of 1.04MHz is approximately twice that of 1.7MHz while the fluorescence intensity of 0.8MHz is approximately 1.5 times that of 1.04MHz.

Magnetic field effect on the fluorescence properties of two metal(Ⅱ) complexes based on 1,3,5-triazine-2,4,6-triyltrithio-tri-acetate

Two metal (Ⅱ) complexes based on 1,3,5-triazine-2,4,6-triyltrithio-tri-acetate exhibit similar (6,3)-connected 2D layer with kgd topology. Negative and positive magnetic field effects (MFEs) on the fluorescence properties of the Mn(Ⅱ) and Zn(Ⅱ) complexes are observed, respectively.

STUDIES ON FLUORESCENCE ENHANCING EFFECT AND ALKALINE DEGRADATION MECHANISM OF DOXYCYCLINE AND METHACYCLINE

Degradation reaction of doxycycline or methacycline was carried out in KOH solution and intense fluorescence was obtained.A degradation mechanism of doxycycline or methacycline was suggested.

The study of fluorescence characteristics and biochemical composition of a marine diatom Thalassiosira pseudonana 3H in light and dark cyclesI. The effects of nutrients

The effects of nutrients on the fluorescence characteristics and biochemical composition of marine diatom Thalassiosira pseudonana 3H in light and dark cycles were investigated with continuous culture. The results show that with the increase of nutrient deficiency, the ratio of enhanced fluorescence to fluorescence (Fd/F), cellular chloropyll-a and protein content of the algae decline, but the fluorescence yield (F/Chl) , DCMU enhanced fluorescence yield (Fd/Chl) , cellular carbohydrate content, carbohydrate/Chl, protein/Chl, carbohydrate/protein increase. The changing amplitude of each parameter is different at different nutrition status, sampling time and different light intensity.

Quantitative energy-dispersive X-ray fluorescence analysis for unknown samples using full-spectrum least-squares regression

The full-spectrum least-squares(FSLS) method is introduced to perform quantitative energy-dispersive X-ray fluorescence analysis for unknown solid samples.Based on the conventional least-squares principle, this spectrum evaluation method is able to obtain the background-corrected and interference-free net peaks, which is significant for quantization analyses. A variety of analytical parameters and functions to describe the features of the fluorescence spectra of pure elements are used and established, such as the mass absorption coefficient, the Gi factor, and fundamental fluorescence formulas. The FSLS iterative program was compiled in the C language. The content of each component should reach the convergence criterion at the end of the calculations. After a basic theory analysis and experimental preparation, 13 national standard soil samples were detected using a spectrometer to test the feasibility of using the algorithm. The results show that the calculated contents of Ti, Fe, Ni, Cu, and Zn have the same changing tendency as the corresponding standard content in the 13 reference samples. Accuracies of 0.35% and 14.03% are obtained, respectively, for Fe and Ti, whose standard concentrations are 8.82% and 0.578%, respectively. However, the calculated results of trace elements (only tens of lg/g) deviate from the standard values. This may be because of measurement accuracy and mutual effects between the elements.

EPR Effect of Amphiphilic Copolymer Micelles Observed by Fluorescent Imaging

Enhanced permeation and retention（EPR） targeting effect of rhodamine B labeled PEG-b-P（LA-co-DHP） [PEG：poly（ethylene glycol）;LA：L-lactide;DHP：2,2-dihydroxylmethyl-propylene carbonate] micelles（RhB-micelles） was observed in H22 liver cancer bearing mice.The RhB-micelles were prepared by conjugating rhodamine B with the DHP units of amphiphilic block copolymer PEG-b-P（LA-co-DHP） followed by subsequent self-assembling of the conjugate.The parent copolymer PEG-b-P（LA-co-DHP） was synthesized by ring-opening copolymerization of LA and DHP with PEG as macroinitiator and diethyl zinc（ZnEt2） as catalyst.The micelles have a spherical shape and the average diameter is ca.50 nm by TEM（transmission electron microscope） or 80 nm by DLS（dynamic light scattering）.Their in vitro cell uptake experiment by CLSM（confocal laser scanning microscopy） and flow cytometry showed preferential internalization of micelles by MCF-7 human breast cancer cells to free RhB.The in vivo tests by live animal imaging and ex vivo excised organ imaging showed that after vena tail injection,free RhB molecules were distributed in the whole body through the circulation system and then gradually metabolized and excreted and there was no preferential partition in tumor bed from the beginning to the end.But the RhB-micelles were preferentially distributed to the tumor bed so that their concentration（fluorescent intensity） in tumor bed got the level of the liver at a certain time point between 1 and 6 h and reached a maximum relative intensity at around 12 h,indicating an obvious EPR effect of RhB-micelles in H22 liver cancer.

Fluorescence and Photosensitizing Behavior of N-(p-Phenoxyphenyl)methacrylamide and Its Polymer

A novel acrylic monomer bearing aromatic ethereality group N-(p -phenoxy-phenyl) methacrylamide(MAPOA) was synthesized and polymerized. The fluorescence spectra of MAPOA and its polymer were studied, showing that the polymer displays a stronger fluorescence than its monomer at the same chromophore concentration. The fluorescence of P(MAPOA) was quenched by adding electron deficiency monomers such as MMA, AN etc .. It is another example of showing the 'fluorescence structural self-quenching effect' as we reported previously, from which it is demonstrated again that this phenomenon is not an accidental one but a common effect for acrylic monomers bearing electon-donating chromophores. The photopolymerization of AN sensitized by MAPOA and P(MAPOA) was studied. The kinetic equation of the polymerization was obtained and represented as follows: R _p∝ 0.38 × 0.78 , R _p∝ 0.33 × 0.71 The overall activation energies were determined to be E_ a =24\^22 kJ/mol(MAPOA) and E_ a =26\^31 kJ/mol respectively. The fluorescence analysis of the resulted P(AN) showed that the sensitizer also entered into the P(AN) chains. A mechanism of the formation of a charge transfer complex and free radical initiation was suggested for the photopolymerization of AN sensitized by MAPOA and P(MAPOA).

Solvent-Induced Symmetry-Breaking Charge Transfer in an Octupolar Triphenylamine Derivative Resolved with Transient Fluorescence Spectroscopy

The excited-state symmetry-breaking charge transfer (SBCT) dynamics in quadrupolar or octupolar molecules without clear infrared markers is usually hard to be tracked directly. In this work, on the basis of the evolution of instantaneous emission dipole moment obtained by femtosecond transient fluorescence spectroscopy, we presented a real-time characterization of the solvent-induced SBCT dynamics in an octupolar triphenylamine derivative. While the emission dipole moment of the octupolar trimer in weakly polar toluene changes little during the excited-state relaxation, it exhibits a fast reduction in a few picoseconds in strongly polar tetrahydrofuran. In comparison with the uorescence dynamics of dipolar monomer, we deduced that the emitting state of the octupolar trimer in strongly polar solvent, which undergoes solvent-induced structural uctuation, changes from exciton-coupled octupolar to excitation localized dipolar symmetry. In weakly polar solvent, the octupolar symmetry of the trimer is largely preserved during the solvation stabilization.

Dual-parameter Correlation Analysis of the Fluorescence Data of 1-Methyl-2-formyl-5-substituted Pyrrole(4-nitrophenyl)hydrazones

By using 1-methyl-2-formyl-5 -Y-substituted pyrrole (4-nitrophenyl)hydrazones as a model for nitrogen-containing heterocyclic aromatic compounds, the emission wavelength [lambda(max(em))] values df their fluorescence spectra have been measured. Correlation results show that the Delta E-em values are mainly affected by polar effects, but spin-delocalizatin effects also exist.

Compact and robust dual-color linearly polarized illumination source for three-photon fluorescence imaging

The miniaturized femtosecond laser in near infrared-Ⅱregion is the core equipment of threephoton microscopy.In this paper,we design a compact and robust illumination source that emits dual-color linearly polarized light for three-photon microscopy.Based on an all-polarizationmaintaining passive mode-locked fiber laser,we shift the center wavelength of the pulses to the 1.7m band utilizing cascade Raman effect,thereby generate dual-wavelength pulses.To enhance clarity,the two wavelengths are separated through the graded-index multimode fiber.Then we obtain the dual-pulse sequences with 1639.4 nm and 1683.7 nm wavelengths,920 fs pulse duration,and 23.75 MHz pulse repetition rate.The average power of the signal is 53.64mW,corresponding to a single pulse energy of 2.25 nJ.This illumination source can be further amplified and compressed for three-photon fluorescence imaging,especially dual-color three-photon fluorescence imaging,making it an ideal option for biomedical applications.

Mutual effects between a gliding arc discharge and a premixed flame

Mutual effects between a gliding arc(GA)discharge at atmospheric pressure and a premixed CH_(4)/air flame were experimentally investigated.Effects of the flame on the GA were studied using simultaneous measurements of the current,the voltage,and the instantaneous images of the plasma columns.The GA in the flame has a thicker and more diffusive plasma column,and it is more frequently ignited at a smaller breakdown voltage than that in the air.The GA extension velocity and the gliding velocity in the flame are larger than those in the air.The electrode voltage drop of the GA discharge in the flame is about 160 V,whereas that in the air is about 220 V.Compared with the GA in the air,the different features of the GA in the flame can be explained by high-temperature,weakly ionized,and species-abundant environment that are generated by the premixed CH_(4)/air flame.Effects of the gliding arc discharge on the premixed flames were demonstrated using planar laser-induced fluorescence of hydroxyl radicals(OH)and formaldehyde(CH_(2)O).OH and CH_(2)O can be formed in the CH_(4)/air mixture in the presence of the GA due to kinetic effects,and the increase of OH and CH_(2)O shows the great potential of the GA for combustion enhancement.

The Fluorescence spectra of Iron-arene complex photo initiator

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Construction of Cox7a2 fluorescent vector and its effect on cytochrome C oxidase activity in mouse Sertoli cell line TM4

Objective To construct Cox7a2 fluorescent vector and study its effect on cytochrome C oxidase ( COX) activity in mouse Sertoli cell line TM4. Methods The coding region of CoxTa2 was amplified from mouse Sertoli cell line TM4 by RT-PCR. PCR product was

An ultra-sensitive dual-mode imaging system using metal-enhanced fluorescence in solid phantoms

In this study, we developed a highly sensitive dual-mode imaging system using gold nanoparticles （GNPs） conjugated to various fluorophores in solid phantoms. The system consists of fluorescence-lifetime imaging microscopy （FLIM） for surface imaging, diffusion reflection （DR） for deep-tissue imaging （up to 1 cm）, and metal-enhanced fluorescence （MEF）. We detected quenching in the fluorescent intensity （FI） for the conjugation of both gold nanospheres （GNS） and gold nanorods （GNRs） to Fluorescein, which has an excitation peak at a wavelength shorter than the surface plasmon resonance （SPR） of both types of GNPs. Enhanced FI was detected in conjugation to Rhodamine B （RhB） and Sulforhodamine B （SRB）, both with excitation peaks in the SPR regions of the GNPs. The enhanced FI was detected both in solution and in solid phantoms by the FLIM measurements. DR measurements detected the presence of GNRs within the solid phantoms by recording the dropped rates of light scattering in wavelengths corresponding to the absorption spectra of the GNRs. With the inclusion of MEF, this promising dual-mode imaging technique enables efficient and sensitive molecular and functional imaging.

Anneal and Concentration Effect on PL Properties of Sol-Gel Derived Eu^(3+) Doped SiO_2 Glass

Eu3+ doped SiO2 nano-crystalline glasses were prepared by sol-gel method. The broad peak of XRD pattern indicates an amorphous SiO2 matrix. The affection of anneal time and anneal temperatures on photoluminescence (PL) properties of SiO2 glass under different Eu doping concentration were studied systematically. It is found that the optimized anneal time is about 3 h. The excitation spectra of 2% Eu3+ doped SiO2 glass powder were measured under various anneal temperatures, and the optimized anneal temperature is observed around 700℃. The fluorescence-quenching effect can be observed in the emission spectra when the annealing temperature exceeds 700℃. The emission spectra of different molar ratio dopants were measured at an annealed temperature of 500℃, and the concentration-quenching phenomenon has also been observed in SiO2 glass powder when the molar ratio of Eu3+ ion exceeds 3% . The result shows that the PL intensity approaches its maximum when the molar ratio of Eu3+ ions in the sample is about 3% . In addition, a comparatively stronger emission spectrum at wavelength of 703 nm which is corresponding to the energy transition 5D0→7F4 of Eu ions is also obtained.

Spectroscopic study of local thermal effect in transparent glass ceramics containing nanoparticles

Local thermal effect influencing the fluorescence of triply ionized rare earth ions doped in nanocrystals is studied with laser spectroscopy and theory of thermal transportation for transparent oxyfluoride glass ceramics containing nanocrystals. The result shows that the local temperature of the nanocrystals embedded in glass matrices is much higher than the environmental temperature of the sample. It is suggested that the tempera,ture-dependent thermal energy induced by the light absorption must be considered when the theory of thermal transportation is applied to the study of local thermal effect.

Effects of Hydrogen-bonding Interaction and Polarity on Emission Spectrum of Naphthalene-Triethylamine in Mixed Solvent

The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethyl-amine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene(band A, 329 nm) and the emission band of the exciplex(band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hydrogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethylamine to the excited naphthalene on the relative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding(or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hydrogen-bonding interaction quantitatively.