Study On The Novel Supramolecule Chemical Sensor Based On Cyclodextrin Derivatives

Supramolecular chemistry is a rising subject. It develops rapidly on the basis of the investigation of crown ethers and hole-type macrocyclic compounds, as well as the investigation of molecular self-assembly process and organic semiconductors and conductors. Supramolecular action is a kind of molecular interaction with molecular recognition ability. It includes Van der Waals and electrostatic interactions, hydrogen-bonding, π-bonding and hydrophobic interaction, which are accompanied by spacial effect. A variety of artificial receptor molecules, such as cyclodextrin (CD), crown ethers, calixarenes and porphyrin, as typical host compounds, have attracted enormous research interest in their molecular recognition. Among them, CDs having an interior hydrophobic cavity and an exterior hydrophilic environment, as a buildup element of second generation supramolecule, can accommodate many organic, inorganic and biological molecules in their toroidal cavity to form stable host-guest inclusion complexes. Therefore, they have been paid much attention by the researchers of supramolecular chemistry. In last twenty years, large numbers of CD compounds have been synthesized, which extend their recognition ability and selectivity for guest molecules. The results indicated that several weak intermolecular forces cooperatively contributed to the molecular recognition process. The size-fitting and complementary geometry between host and guest play an important role in the stability of inclusion complex formed. A lot of experimental methods, such as NMR, X-ray power diffraction, IR, UV-Vis, fluorescence spectroscopy, electrochemical method, thermal analysis, chromatographic analysis and theoretical calculation method, are used to investigate the mechanism of supramolecular action and molecular recognition. At present, as for the study on the CD supramolecular chemistry, not only new CD derivatives have been continually synthesized and the interaction between them and guests have been investigated, but also there are developments in the study on the CD self-assembly behavior on the electrode surface and the construction of supramolecular devices with CDs. In recent years, CD and its derivatives have been applied to design the chemical sensors with molecular selectivity. However, there are some problems existing in this field: (1) there are few reports that CD and its derivatives are actually immobilized on the membranes of the optical sensors; (2) Few CD polymers were reported as applied to the chemical sensor field; (3) The only limited type mechanism of molecular recognition is utilized in the application of CD to chemical sensor. The CD study on the chemical sensor technology is expected to develop in a deep and extensive direction. With respect to the existing problems, the following researches are carried out in the present thesis. (1) An optical sensor for berberine, the basic ingredient of the widely used traditional Chinese medicine Coptis Chinensis, based on its intrinsic fluorescence enhanced by butylated-β-cyclodextrin (HDB-β-CD) immobilized in plasticized poly(vinyl chloride) (PVC) membrane, has been developed (Chapter 2). The proposed sensor was quite distinct from those fluorescent sensors for berberine reported so far which relied upon quenching the fluorescence of the sensing reagent immobilized on membrane by berberine. The response mechanism of optode membrane was discussed in detail from the view of molecular dynamics and the optimum steric configuration of the inclusion complex was presented by molecular dynamics simulation. The analytical performance characteristics of the proposed berberine-sensitive sensor were investigated. The sensor can be applied to the quantification of berberine with a linear range covering from 4.0×10-7 mol?L-1 to 2.0×10-5 mol?L-1 with a detection limit of 8.0×10-8 mol?L-1. The sensor exhibits excellent reproducibility, reversibility and selectivity. The recommended method was successfully used for the determination of berberine in pharmaceutical preparations. (2) A highly selective and sensitive electrochemical sensor based on carboxymethylated β-cyclodextrin polymer (CM-β-CDP) film was fabricated for the determination of dopamine (DA) in the presence of ascorbic acid (AA) (Chapter 3). The electrochemical behavior of DA and AA at the chemically modified electrode was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The response mechanism of CM-β-CDP film for DA was based on the combination of electrostatic and inclusion interaction of CM-β-CDP with DA. This sensor was distinguished from the response mechanism of those charged polymer film modified electrode that only relied upon the electrostatic interaction between charged polymer film and DA (or AA). The CM-β-CDP film showed preferable analytical performance characteristics in catalytic oxidation of DA as compared to the β-cyclodextrin polymer (β-CDP) film. Under optimized conditions, it was feasible for the electrode modified with the CM-β-CDP film to selectively determine DA in the presence of large excess of AA. Linear calibration plot was obtained over the range 8.0×10-7 ~ 6.0×10-5 mol?L-1 with a detection limit (S / N =3) of 2.0×10-7 mol?L-1 in the presence of 1.0×10-3 mol?L-1 AA. This electrochemical sensor showedexcellent sensitivity, repeatability, stability and recovery for the determination of DA. The interference of AA with the determination of DA could be efficiently eliminated. (3) An optical sensor for cetyltrimethylammonium chloride (CTAC), based on the fluorescence quenching of berberine/butylated-β-cyclodextrin (HDB-β-CD) complex immobilized in plasticized poly(vinyl chloride) (PVC) membrane, has been developed, in which berberine served as a sensitive fluorescence indicator probe(Chapter 4). The decrease of fluorescence intensity of berberine/HDB-β-CD complex upon the addition of CTAC was attributed to the formation of an inclusion complex between HDB-β-CD and CTAC, which has been utilized as the basis of the fabrication of a CTAC-sensitive fluorescence sensor. The response mechanism of sensor has been discussed in detail. The analytical performance characteristics of the proposed CTAC-sensitive sensor were investigated. The sensor can be applied to the quantification of CTAC with a linear range covering from 7.0×10-11 mol?L-1 to 4.0×10-9 mol?L-1 with a detection limit of 3.0×10-11 mol?L-1. The sensor exhibits excellent reproducibility, reversibility and selectivity. The recommended method was successfully used for the determination of CTAC in water samples. (4) An electrochemical sensor for cinchonine (CCN) using the β-CD modified poly (N-acetylaniline) (PAA) electrode has been developed, in which 1,4-hydroquinone (HQ) was chosen as a probe(Chapter 5). Complexation of HQ with β-CD modified on the glassy carbon electrode (GCE) was examined by CV. HQ was included in the cavity of β-CD and reversible voltammograms were observed. In the presence of CCN, a competitive inclusion equilibrium with β-CD was established between HQ and CCN, lowering the peak current of HQ. The decrease in the peak current of HQ is directly proportional to the amount of CCN. Linear calibration plot was obtained over the range 4.0×10-6 ~ 8.0×10-5 mol?L-1 with a detection limit (S / N =3) of 2.0×10-6 mol?L-1. From the inhibitory effect of CCN on the inclusion of HQ by β-CD, the apparent formation constant of CCN with the immobilized β-CD was estimated. This electrochemical sensor showed excellent sensitivity, repeatability, stability and recovery for the determination of CCN. The response mechanism of the sensor was discussed in detail. The optimum steric configuration of inclusion complex was presented by molecular dynamics simulation. (5) Multilayered thin films were prepared by a layer-by-layer deposition of sulfonated β-cyclodextrin (s-β-CD) and cationic poly (allylamine hydrochloride) (PAH) on the surface of a quartz slide (Chapter 6). A self-assembled fluorescent host, s-β-CD/neutral red, was formed by the inclusion interaction of neutral red (NR)with the s-β-CD immobilized on the multilayered films. An optical sensor for lithocholic acid (LA), based on the fluorescence quenching of s-β-CD/NR complex immobilized on the multilayered films, has been developed, in which NR served as a sensitive fluorescence indicator probe. The decrease of fluorescence intensity of s-β-CD/NR complex in the presence of LA was attributed to the formation of an inclusion complex between s-β-CD and LA, which has been utilized as the basis of the fabrication of a LA-sensitive fluorescence sensor. The response mechanism of sensor has been discussed in detail. The analytical performance characteristics of the proposed LA-sensitive sensor were investigated. The sensor can be applied to the quantification of LA with a linear range covering from 2.0×10-6 mol?L-1 to 6.0×10-5 mol?L-1 and a detection limit of 1.0×10-6 mol?L-1. The sensor exhibits excellent reproducibility, reversibility and selectivity. (6) An electrochemical sensor modified with multi-walled carbon nanotubes/β-cyclodextrin (MWNTs/β-CD) film was fabricated for the determination of rutin (Chapter 7). The electrochemical behavior of rutin at the chemically modified electrode was investigated by CV. The response mechanism of MWNTs/β-CD film for rutin was based on the inclusion interaction of β-CD for rutin. The MWNTs/β-CD film showed preferable analytical performance characteristics in electrocatalytic oxidation and reduction for rutin compared with the MWNTs film and bare glassy carbon electrode (GCE). A linear calibration plot was obtained covering the range from 4.0×10-7 mol?L-1 to 1.0×10-3 mol?L-1 with a detection limit of 2.0×10-7 mol?L-1. This electrochemical sensor showed excellent sensitivity, selectivity, stability, and recovery for the determination of rutin in urine samples. (7) An optical sensor for mercury ion, based on quenching the fluorescence of the sensing reagent?tetra(p-dimethylaminophenyl)porphyrin (TDMAPP) immobilized in plasticized poly(vinyl chloride) (PVC) membrane, has been developed (Chapter 8). The drastic decrease of fluorescence intensity of TDMAPP was attributed to the formation of a complex between TDMAPP and mercury ion, which has been utilized as the basis of the fabrication of a mercury ion-sensitive fluorescence sensor. The response to mercury ion of proposed sensor was compared with those of 5,10,15,20-tetraphenylporphyrin (TPP) and tetra (N-phenylpyrazole) porphyrin (TPPP). The analytical performance characteristics of the proposed mercury ion-sensitive sensor were investigated. The sensor can be applied to the quantification of mercury ion with a linear range covering from 4.0×10-8 mol?L-1 to 4.0×10-6 mol?L-1 with a detection limit of 8.0×10-9 mol?L-1. The sensor exhibits excellent reproducibility, reversibility and selectivity. The recommended methodwas successfully used for the determination of mercury ion in water samples.