Study On The Fluorescent Chemosensors For Metal Ions Based On Quinoline Derivatives

Improving the selectivity of a sensor is recognized as a difficult problem in the field of chemical sensing technology. The fluorescence sensors were widely investigated owing to high selectivity, excellent sensitivity and low expense. Therefore, searching for novel fluorophores is still a challenge for the analytical research efforts. In this paper, quinoline derivatives were immobilized in the membrane to construct fluorescent sensors for Fe³⁺ and Al³⁺, respectively. And the obtained sensors were used to determine some practical samples with satisfactory results.Electrochemical enzymatic biosensors based on the recognition of specific substrates have the advantages of high sensitivity and nice selectivity as well as easy miniaturization and automation. In the design and fabrication of the electrochemical biosensors the crucial step is how to develop a simple and effective strategy for the construction of sensitive membrane on the electrodes. Carbon nanotube (CNTs), as a kind of nano material, can produce special catalytic action to some materials because of its small particle diameter and large surface area. So they are often used to construct enzymatic biosensors. Tris(2,2'-bipyridyl)ruthenium(II) complex is a high effective mediator. A tris(2,2'-bipyridyl)ruthenium(II)-chitosan-carbon nanotube composite was prepared, where carboxyl tris(2,2'-bipyridyl)ruthenium(II) and carboxyl carbon nanotubes were covalently coupled to chitosan through carbondiimide reagent. We used the composite to embed the GOD to fabricate a GOD biosensor.The details are summarized as follows:1 . In part 1, 2-(2′-hydroxy-phenyl)-4(3H)-quinazolinone(HPQ), a typical compound that exhibits excited state intramolecular proton transfer(ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe³⁺ sensitive optochemical sensor. The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe³⁺ was attributed to the blocking of ESIPT reactions of HPQ and quenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Fe³⁺ in the concentration range 7.1×10^-7—1.4×10^-4 M with a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe³⁺ over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples with satisfactory results.2 . In part 2, 5-formyl-8-hydroxyquinoline is synthesized and used as fluoroionophore for Al³⁺ sensitive optochemical sensor. The fluorescence intensity of the sensor increased with the addition of Al³⁺. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Al³⁺ in the concentration range 7.8×10^-6-1.7×10^-3M with a working pH at 4.98. It shows excellent selectivity for Al³⁺ over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of Al³⁺ in real samples with satisfactory results.3.Carbon nanotube (CNTs), as a kind of nano material, can produce special catalytic action to some materials because of its small particle diameter and large surface area. So they are often used to construct enzymatic biosensors. Considering tris(2,2'-bipyridyl)ruthenium(II) complex is a high effective mediator, a tris(2,2'-bipyridyl)ruthenium(II)-chitosan-carbon nanotubes composite was prepared, where carboxyl tris(2,2'-bipyridyl)ruthenium(II) and carboxyl carbon nanotubes were covalently coupled to chitosan through carbondiimide reagent. We used it to embed the GOD to fabricate a GOD biosensor. The biosensor had a fast response of less than 5 s, and the response current linearly increases with the glucose concentration in the range of 1.0×10^-5—3.1×10^-3 M with a detection limit of 2.5×10^-6M.