Fluorescence Spectra Analysis of N-n-Octyl Oyridine Acetate Ionic Liquid in Different Solvents
TIAN Peng1, XIAO Xue-song1, SU Gui-tian1, DUAN Han-feng1，JIN Yao-dong1, SONG Yang-yang1, HUANG Tao2, ZHANG Hang1*
1. College of Chemistry and Chemical Engineering, Shenyang Normal University, Shenyang 110034, China
2. College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China
Abstract：Ionic liquids have attracted extensive attention in the chemical industry and related fields due to their unique properties such as low melting point, negligible vapor pressure, wide electrochemical window, high thermal stability and good electrical conductivity. Ionic liquids have low vapor pressure and do not cause air pollution, but that does not mean they are completely environmentally friendly. Most ionic liquids are soluble in water and may enter the aquatic environment through accidental leaks or sewage. Hydrofluoric acid and phosphoric acid are easily formed in the aqueous solution of commonly used ionic liquids [BMIM][PF6] and [BMIM][BF4], which have certain corrosive properties. Therefore, classifying ionic liquids as green solvents also requires data on their toxicity, ecotoxicity studies of metabolism and degradation, or their impact on the environment. Therefore, the detection method of ionic liquid in different solvents is very important. The spectral analysis method of ionic liquid is simple and accurate. Ionic liquids are insoluble with many organic solvents to form homogeneous, stable solutions. The fluorescence detection method has the advantages of high sensitivity, good selectivity, wide linear range and less interference. We have studied the fluorescence spectra of OP-OAc ionic liquid in water, ethanol, acetonitrile and acetic acid. The study results show as follows: the fluorescence intensity of OP-OAc ionic liquid in different solvents is Iacetic acid＞Iacetonitrile＞Iethanol＞Iwater; the order of maximum emission wavelength is λem, water＞λem, ethanol＞λem, acetonitrile＞λem, acetic acid; their maximum emission wavelength is redshifted relative to the excitation wavelength; the fluorescence intensity of OP-OAc ionic liquid in water is highly correlated with its concentration, as the experiment shows that the fluorescence intensity of OP-OAc ionic liquid increases with the addition of methanol, ethanol and acetonitrile, the fluorescence intensity of OP-OAc ionic liquid is the strongest when the ratio of solvent to water is 8∶2, and the fluorescence intensity decreases suddenly when the ratio of solvent exceeds 80%; the fluorescence intensity of OP-OAc ionic liquid in water is the highest when pH 10, and the fluorescence intensity is the lowest at pH 14.
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