XAFS at Eu-L-3 edge and UV-VUV excited luminescence of europium doped strontium borophosphate prepared in air

The local structure and the valences of europium in SrBPO5:Eu prepared in air were checked by means of XAFS at Eu-L-3 edge. From the EXAFS results, it was discovered that the doped europium atoms were nine-coordinated by oxygen atoms and the distances of bond Eu-O were 2.42 Angstrom in the host. From the XANES data, it was found that the divalent and trivalent europium coexisted in the matrix. The emission spectra excited by VUV or UV exhibited a prominent broad band due to the 4f(6)5d-4f(7) transition of Eu2+ ions, which indicated that the trivalent europium ions were reduced in air in the matrix at high temperature by the defects [V-Sr]" formed by aliovalent substitution between Sr2+ and Eu3+ ions. The VUV excitation spectra in 100-200 nm range showed that the matrix had absorption bands with the maxima at about 130 and 150 nm, respectively.

VUV excited luminescence of europium activated calcium borophosphate prepared in air

XAFS (EXAFS and XANES) at Eu-L-3 edge were used to determine the local structure and the valences of europium in CaBPO5:Eu prepared in air. The results of EXAFS showed that the doped europium atoms were nine-coordinated by oxygen atoms and the distances of bond Eu-O were 2.39 Angstrom in the host lattice. XANES at Eu-L-3 edge exhibited that Eu2+ and Eu3+ coexisted in the matrix. The luminescent spectrum of the material excited by VUV at 147 nm presented a similar spectrum with that excited by f-f transition of Eu2+ at 396 nm and f-d transition of Eu2+ at 312 nm. The broad emission band due to both 4f(6)5d - 4f(7) transition of EU2+ and f - f transition of Eu3+ could be observed in emission spectra, which indicated that the trivalent europium ions were reduced in air in the matrix at high temperature by the defects [V-Cn]" formed by aliovalent substitution between Ca2+ and Eu3+ ions. The UV excitation spectrum showed the typical f-f transition of Eu3+ and f-d transition of Eu2+. The bands with the maxima at about 113 and 158 nm in VUV excitation spectrum were assigned to originate from the absorption of the host lattice.

Study on the integrated membrane processes of dehumidification of compressed air and vapor permeation processes

Blend modified polyimide (PI) hollow fiber membranes were used in vapor permeation for gas phase dehydration of ethanol. Dry air sweeping operation was used and the dry air was supplied by a dehumidification membrane module of compressed air. An integrated membrane process was composed. The effects of some factors, such as the modification of membrane materials, the humidity and current velocity of sweeping air, the operation temperature, on the efficiency of dehydration were discussed.

Matrix effects in flow injection-inductively coupled plasma mass spectrometry

Matrix effects in now injection (FI) inductively coupled plasma mass spectrometry has been studied,and the results have been compared with those of continuous nebulization. The matrix element As and nu with higher ionization potential ( > 9eV) have enhancement effect on the analyte signal,and the heavier the analyte mass, the smaller the enhancement effects by Fl. The matrix elements Cu, In, Li, Na and Pb with lower ionization potential have suppression effect on the analyte signal. The heavier the matrix element mass, the more severe the suppression effects. The heavier the analyte mass, the smaller the suppression effects. The higher ionization potential of analyte, the more severe the suppression effects. Compared with continuous nebulization, the degree of suppression effect is smaller and the degree of the enhancement effect is larger by Fl.

Determination of ascorbic acid by flow injection chemiluminescence suppression method

chemiluminescence suppression method for the determination of ascorbic acid based on Luminol-KIO4-H2O2-ascorbic acid system was established. The linear range for ascorbic acid is 1.0 x 10(-7) similar to 1.0 x 10(-5) mol/L and the detection limit is 6.0 x 10(-8) mol/L. The relative standard deviation (n = 11) is 1.0% for 8.0 x 10(-7) mol/L ascorbic acid. The method has been used to determine the content of ascorbic acid in tablets and injections with satisfactory results.

Fullerenes-extracted soot: a new adsorbent for collecting volatile organic compounds in ambient air

Fullerenes-extracted soot (FES) is the by-product of fullerenes production. Retention characteristics at different temperatures for 17 volatile organic compounds (VOCs) on FES are measured. The adsorption and desorption efficiencies for VOCs on FES adsorbent tubes range from 40.8 to 117%, most of them being 100+/-20%. The values are compared with Tenax GR, an adsorbent commonly used in environmental analysis. FES can be used as an adsorbent of low cost to collect VOCs in environmental samples. (C) 2000 Elsevier Science B.V. All rights reserved.

Preparation of borates doped with divalent rare earth ions (RE2+) in air and spectroscopy of divalent rare earth ions (RE2+ = Sm, Eu, Tm, Yb)

The spectroscopic feature of divalent Sm2+, Eu2+, Tm2+ and Yb2+ is discussed in this paper. Especially the spectroscopic properties of some berates containing tetrahedral BO4 group such as SrB4O7, SrB6O10 and BaB8O13 doped with these divalent ions are reported. When the divalent alkaline earth ion in these berates is replaced partially by the above trivalent rare earth ion, the charge carried in the produced defects can be used as reductant to reduce the doped rare earth ion into divalent state at high temperature even in air. Therefore, a convenient and safe method is provided to prepared phosphors doped with these divalent rare earths.

Characteristics in frequency domain by inductively coupled plasma atomic emission spectrometry with charge injection detection

The charactesistics of two-dimension spectra obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES) with charge injection detection (CID) in frequency domain were studied in the present paper. The measurement spectra were Fourier transformed and the frequency distribution of the spectra was obtained. Results showed that the spectra in frequency domain could he divided into two parts:high frequency and low frequency signals. The later stood for measurement spectra and the former for background and noises. However, the high frequecny signals could not be smoothed simply to reduce noises because the background was deteriorated even though the spectral signal did not change significantly.

The reduction of RE3+ in SrB6O10 prepared in air and the luminescence of SrB6O10 : RE2+ (RE=Eu, Sm, Tm)

The reduction of RE3+ to RE2+ (RE=Eu, Sm and Tm) in SrB6O10 prepared in air by high-temperature solid state reaction was observed. The luminescent properties of Eu2+ and Tm2+ show f-d transition and Sm2+ shows f-f transition at room temperature. Three crystallographic sites for Sm2+ in matrix are available. Vibronic transition of D-5(0)-F-7(0) of Sm2+ was studied. The coupled phonon energy about 108 cm(-1), was determined: from the vibronic transition. Due to the thermal population from D-5(0) level, (D1-FJ)-D-5-F-7 (J=0, 1, 2) transitions of Sm2+ were observed at room temperature. A charge compensation mechanism is proposed as a possible explanation.

A study on the mechanism of the abnormal reduction of Eu3+ -> Eu2+ in Sr2B5O9Cl prepared in air at high temperature

This paper reports a new observation of the abnormal reduction of Eu3+ --> Eu2+ in Sr2B5O9Cl when prepared in air at high temperature. A model based on the nature of substitution defects is proposed to explain this abnormal reduction. Electrons, which reduced the Eu3+ ions, are created by the substitution of cations first and then transferred to the target Eu3+ ions via tetrahedral berate anion groups. Codoping experiments are designed and performed. The results of these experiments support the model proposed. (C) 1999 Academic Press.