| Organic fluorescent sensors show an important application in the areas such as environmental and biochemistry detections,because of their easy synthesis,rapid fluorescence response,high sensitivity and good selectivity.There are a lot of fluorescent sensors used for determination of heavy metal ions,however,few fluorescent sensors used for determination of NO2-have reported yet.In this paper,two kinds of rhodamine derivatives?named as RbH and R6GH?were used as fluorescent sensors to detect NO2-.The main contents are as follows:1.Preparation of rhodamine derivativesTwo kinds of rhodamine rhodamine B hydrazine?named as RbH?and rhodamine 6G hydrazine?named as R6GH?were prepared as?upconversion?fluorescent probes.Their structures were characterized by nuclear magnetic resonance hydrogen spectrum and mass spectrometry.And their optical properties were investigated by ultraviolet absorption spectrum and fluorescence spectrum.Since RbH and R6GH possess spiro-lactam structures that decrease the delocalization bond and result in molecular no color and no fluorescence in the visible regions.2.Fluorescence detecting to NO2-In acidic buffer solution,rhodamine B hydrazine?RbH?interacts with NO2-ion,which can induce the spiro-lactam of RbH be opened.This fact results in the red fluorescence emission located at 580 nm?coming from rhodamine B?under the excitation of 500 nm.Importantly,the red fluorescence intensity increases linearly with the concentration of NO2-ion?[NO2-]?.The invesitigatin of selectiveity shows that rhodamine B hydrazine?RbH?has no fluorescent response to common anions meanwhile it displays good fluorescent response to ClO-and NO2-.Also,the investigation of sensitivity shows that the detection limit to NO2-can reach to 4×10-8 M.3.Upconversion fluorescence detecting to NO2-It was found that in acidic solution of DMF/H2O,rhodamine B hydrazine?RbH?possesses upconversion fluorescence response only to NO2-.The reaction between RbH and NO2-can induce spiro-lactam of RbH be opened,which results in relative fluorescence intensity increases linearly with the[NO2-],under excitation of 634 nm.The invesitigatin of selectiveity shows that rhodamine B hydrazine?RbH?displays only one fluorescent response to NO2-within 16 kinds of commom ions.Also,the investigation of sensitivity shows that the detection limit to NO2-can reach to 7×10-7 M.4.Fluorescence detecting to glutamate acid and aspartic acidThe spiro-lactam structures of rhodamine 6G hydrazide?R6GH?and rhodamine B hydrazine?RbH?can be opened by glutamate acid and aspartic acid in the mixed solution of DMF/H2O.In the same conditons,the other 18 kinds of?-aminoacids have almost no response with the fluorescent probes?RbH and R6GH?.The experiment confirmed that the two amino acids interact with the probe molecules and can induce the spiro-lactam be opened,color changes obviously and fluorescence intensity increases linearly.Thus,the identification response of glutamate and aspartic acid was realized,and their detection limits can reach 7×10-88 M and 1×10-7 M. |
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