Development of FRET-based dual-excitation ratiometric fluorescent pH probes and their photocaged derivatives

Dual-excitation ratiometric fluorescent probes allow the measurement of fluorescence intensities at two excitation wavelengths, which should provide a built-in correction for environmental effects. However, most of the small-molecule dual-excitation ratiometric probes that have been reported thus far have shown rather limited separation between the excitation wavelengths (20-70 nm) and/or a very small molar absorption coefficient at one of the excitation wavelengths. These shortcomings can lead to cross-excitation and thus to errors in the measurement of fluorescence intensities and ratios. Herein, we report a FRET-based molecular strategy for the construction of small-molecule dual-excitation ratiometric probes in which the donor and acceptor excitation bands exhibit large separations between the excitation wavelengths and comparable excitation intensities, which is highly desirable for determining the fluorescence intensities and signal ratios with high accuracy. Based on this strategy, we created a coumarin-rhodamine FRET platform that was then employed to develop the first class of FRET-based dual-excitation ratiometric pH probes that have two well-resolved excitation bands (excitation separations>160 nm) and comparable excitation intensities. In addition, these pH probes may be considered as in a kind of "secured ratioing mode". As a further application of these pH probes, the dual-excitation ratiometric pH probes were transformed into the first examples of photocaged dual-excitation ratiometric pH probes to improve the spatiotemporal resolution. It is expected that the modular nature of our FRET-based molecular strategy should render it applicable to other small-molecule dual-dye energy-transfer systems based on diverse fluorescent dyes for the development of a wide range of dual-excitation ratiometric probes with outstanding spectral features, including large separations between the excitation wavelengths and comparable excitation intensities.     

Sr2MgSi2O7∶Tb3+，Li+荧光粉的合成和发光机理

采用高温固相法合成Sr2-mMg1-nSi2O7∶mTb3+,nLi+(m=0.03~0.50,n=m)系列荧光粉。使用X射线衍射仪和荧光光谱仪对样品的物相和发光性质进行了表征。在377 nm紫外光激发下,荧光粉的发射光谱呈多谱带发射,主峰位于490 nm,542 nm,590 nm和613 nm处,分别对应于Tb3+的5D4→7FJ(J=6,5,4,3)跃迁发射。调节Tb3+离子掺杂浓度,可实现荧光粉的发光颜色从蓝到白、黄、绿的可调发射;名义组成为Sr1.95Mg0.95Si2O7∶0.05Tb3+,0.05Li+的荧光粉在紫外光(377 nm)激发下发白光,其色坐标(0.322,0.317)接近纯白光(0.33,0.33),是一种潜在的LED用单基质白光荧光粉。     

Synthesis,Spectra and Crystal Structure of Tetrakis(Triphenylarsine Oxide)Iron(III)-μ-Oxo-Tribromoiron(III) Tetrabromoferrate(III)-Acetonitrile

The oxidation of triphenylarsine with dioxygen in reaction systems containing some iron compound and Br^- anions in acetonitrile leads to the formation of a novel unsymmetrical oxo-bridged diiron(III) complex [(OAsPh₃)₄ Fe(μ-O)FeBr₃]⁺ [FeBr₄]^- ·CH₃CN, where OAsPh₃ is triphenylarsine oxide. The title complex is also formed by direct reaction of iron(III) bromide and OAsPh₃ with dioxygen in acetonitrile solution. The crystal structure of the complex was solved by X-ray diffraction techniques. The cation contains two unsymmetrical species with an Fe-O-Fe bond angle of 159.2(2)°; one iron atom is pentacoordinated by four OAsPh₃ ligands and a γ-oxo ligand which connects the tetracoordinated Fe atom with the FeBr₃O chromophore. Structural parameters and IR spectra of similar complexes are compared and discussed.     

Micronalytical Application Or A Kissinger Type Thin Layer Cell Polarized By Lsv,Npv and Dpv Excitation

Abstract

Three methods were tried and proven to be useful for the polarization of a thin layer cell. the main advantage of making the measurements with Kissinger type cells filled with quiescent solution is that less than 50, uL sample can be measured. the sensitivity is apparently the highest by using NPV, but its application is not advised because of the relatively high charging current content of the signal.

DPV is an excellent method both from the point of view of its sensitivity (at high E it is superior) and very good selectivity as well.

The LSV method proved to be good one and the simplest method when reversible systems must be measured. the steady state limiting current gives a possibility to carry out measurements with high sensitivity, and a 1x10(-7)M/dm³ lower detection limit was found by applying it.

The optimization procedure left chances for further refinements when computerized insturments were used. the sigmoid type current at the LSV technique certainly would give better selectivity, when the digital first derivative of the curve is used.     

Collisional Energy Transfer of Highly Vibrationally Excited Polyatomic Molecules. The Effect of Excited Molecule Complexity

Collisional relaxation was probed by CO₂ laser activated delayed fluorescence. The experimental information was adopted to determine the average energies transferred per collision (ΔE) from highly vibrationally excited polyatomic molecules to parent collider. The values of (ΔE) decreased with increasing the number of atoms in the excited molecules in line: biacetyl, acetophenone, benzophenone, antraquinone. The dependences of (ΔE) on the number of factors such as: 1) the average vibrational energy residing in the vibrational modes of excited molecules; 2) the potential of intermolecular interaction; 3) the reduced mass, and others were analyzed in details. The general interplay was noticed between (ΔE) and the molecular parameters which determined the increasing interaction strength and the decreasing energy transfer efficiency due to the adiabatic constraints on the energy transfer.     

Multiexcitation Raman Spectroscopy in Identification of Chinese Jade

The high-fluorescence background of jade creates a great impact on the Raman spectra measurements that impedes their application in jade analysis and treatment, particularly with ancient jade. The five most important materials of Chinese ancient jade are amphibole, serpentine, turquoise, agate/chalcedony, and anorthite-zoisite (Dushan jade). This study comparatively analyzed the Raman spectra of different wavelengths' excitation light sources (514.5 nm, 632.8 nm, 785 nm) in identifying these Chinese jades, and this article discusses the most applicable ones to the analysis of different jade materials. The results show that although 632.8 nm He-Ne laser is appropriate for turquoise jades, generally speaking, Raman spectra produced by the 785 nm semiconductor laser and the 632.8 nm He-Ne laser are better for most kinds of jades than the spectra produced by the 514.5 nm argon ion laser, and both of them can be effectively used jointly in research by nondestructive phase analysis of Chinese ancient jade.     

In Situ Measurement of Excitation Intensity for Fluorescence Excitation Spectroscopy

It is argued that the double-beam method for the automatic correction of fluorescence excitation spectra, which proved to be a great boon in the days of analog instrumentation, has become, after the advent of digital techniques for acquiring and manipulating spectral data, more of a hindrance than a help; the benefits of reverting to a single beam device and making in situ measurement of the excitation intensity are pointed out.     

The Excitation Temperatures of Nonmetal Atoms and the OH Temperatures in Microwave-Induced Plasma

Abstract

The excitation temperatures of nonmetal atoms and the OH molecule temperatures have been measured in argon MIP, operating under atmospheric pressure at different experimental conditions. Atoms of Ar I, P I and H have been used as thermometric species. The rotational and vibrational temperatures have been obtained from the OH A²Σ⁺ - X²? band spectra. The ^SR₂₁ ratational lines have been used for the first time for the temperature measurements. The energy distributions observed here are discussed.     

Thermal Emission Spectrum of the Cobalt Monobromide Molecule

ABSTRACT

The thermal emission spectrum of the CoBr molecule has been photographed for the first time in the spectral region 4200–6000 Å using the high-temperature excitation technique and the 2-meter plane grating spectrograph (PGS-2). The spectrum has been recorded at a reciprocal linear dispersion of 7.3 Å/mm. About 203 red degraded and line-like bands have been recorded, out of which 172 are entirely new. The observed bands have been classified into 31 systems, of which 23 are entirely new. The vibrational analyses have been carried out using band head measurements and the Deslandre table. The ground state of the CoBr molecule is found to be ³Φ with the vibrational constants 318.3, 329.5, and 332.7 cm^?1.