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An Aminosalicylic Acid-based Schiff Base as a Fluorescent Switch and Its Analytical Application

Author: LiuWeiZhou
Tutor: ChenFang
School: Huazhong University of Science and Technology
Course: Analytical Chemistry
Keywords: Fluorescent molecular switch Schiff base Iron Citrate Logic gate
CLC: O621.2
Type: Master's thesis
Year: 2011
Downloads: 69
Quote: 0
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Abstract


A fluorescent molecular switch was a molecule that whose fluorescent intensity could be reversibly shifted between two states just like enhancement or quenching. The fluorescent intensity might be shifted between the states in response to changes in pH, light, temperature, metal ions and so on. Fluorescent molecular switche had be widely interested as chemical analysis method due to its convenient in determination, high sensitivity and short response time. An salicylic acid-based schiff base was synthesized and the fluorescent switch properties were studied in this paper. The work in this paper mainly includes two parts as follow:First, 2-hydroxy-4-（pyridin-2-ylmethyleneamino） benzoic acid （PA） was synthesized with 2-pyridylaldehyde and 4-aminosalicylicacid. The product was identified by IR spectra and LC-MS. It was demonstrated that Fe3+ could selectively quench the fluorescence of PA in acidic aqueous solution, whereas other metal ions such as Zn2+, Cu2+, Ni2+, Co2+, Mn2+, Cr3+ and Fe2+ can’t. In addition, the fluorescent intensity of PA could be reversibly tuned by ligand （just like EDTA） or reductant （just like hydroxylamine hydrochloride）. Thus PA could perform the "OFF-ON" function of fluoresce emission intensity and could be used as a double control fluorescent molecule switch. In the addition, they could executed one excellent logic operation, which integrated one OR logic gates.Second, PA, which showed high specificity for Fe3+ recognition, could be used as a fluorescent molecular probe. The results indicated that the fluorescence intensity of PA at 392 nm could be significantly quenched by Fe3+, and the fluorescence intensity was in proportion to the concentration of Fe3+. Under the optimum conditions, the linear range for the determination was 4.0×10-7 to 6.5×10-6 mol L-1, and the detect limit was 4.8×10-8 mol L-1. The proposed method was successfully applied to assay Fe3+ in milk powders with good recovery rate （93.0105%）. While citrate added to the PA-Fe3+ system, the fluorescence of PA recovered. These might because that citrate had stronger coordinating ability to Fe3+, it would prohibit the formation of PA-Fe3+ complex. And the fluorescence intensity of PA-Fe3+-citrate system was in proportion to the concentration of citrate. Based on that, a novel fluorescence enhance method was established for citrate detection, and the detect limit and linear range are 2.2×10-7 mol L-1 and 2.0×10-6 to 2.0×10-5 mol L-1, respectively. This method was simple, practical, sensitive, and it was selective and successfully applied to determination of citrate in soft drink. The fluorescence enhancement and quenching mechanisms were also discussed in the text.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Properties of organic compounds
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