Study On Electrochemical Sensors Based On Supramolecular Recognition Of β - Cyclodextrin

Electrochemical method has received considerable attention in the determination of analytes. The electrochemical method has shown great advantages, such as simple operation, low cost, and in situ detection, compared with the traditional detection methods, such as high performance liquid chromatography, fluorescence, capillary electrophoresis. Furthermore, electrochemical method also has some advantages, such as stablity, rapidity, sensitivity. Therefore, it becomes an important tool for trace detection of hazardous substances in many areas. In the present study, by combining the merits of β-cyclodextrin (P-CD)(high supermolecular recognition and enrichment capability) and some nanomaterials (e.g. graphene, multiwalled carbon nanotube)(high electrical conductivity and electrocatalytic activity), we developed electrochemical sensors for determination of phenols and cholesterol by using β-CD and other new materials. The obtained results are summarized as follows:(1) Graphene was synthesized by chemical reduction of graphene oxide. A highly sensitive and selective electrochemical sensing platform was developed based on a new bridged bis(β-cyclodextrin) non-covalently functionalized graphene (Bβ-CD/GN) nanohybrids for detection of p-nitrophenol. The prepared graphene was characterized by UV-vis spectrum, X-ray diffraction spectrum, Raman spectrum. The host-guest molecular recognition capacity between Bβ-CD and guest was investigated. A linear response range of0.1to100.00M for p-nitrophenol with a low detection limit of0.5M (S/N=3) was obtained by using the method. The proposed sensor can be used to determine p-nitrophenol in the practical water samples. This work provides a promising electrochemical sensing platform for monitoring environmental pollutants.(2) A ultrasensitive electrochemical senor for simultaneous determination of three phenols (p-AP, p-CP and p-NP) was constructed by using the disulfide linked cyclodextrin dimer (CD-SS-CD) functionalized multiwalled carbon nanotube. The prepared nanocomposite was characterized by fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The molecular recognition capacity between CD-SS-CD and phenols was also investigated. The three phenols detection limits were0.0042M,0.028M and0.048M (S/N=3), which were lower than those in the reported papers. Moreover, the proposed senor was ultrasensitive and has the potential to be used for the determination of p-AP, p-CP and p-NP in waste water samples, which is suggested a promising method for monitoring environmental pollutants.(3) Gold nanoparticles/carboxylic silicon carbide nanohybrids (Au-CSiC) were synthesized via a chemical reduction method. Gold nanoparticles were uniformly monodispersed on the suface of carboxylic silicon carbide. The thiol β-cyclodextrin (SH-CD) and ethylenediamine β-cyclodextrin (NH2-β-CD) were grafted on the surface of nanohybrids by Au-S bond and amido bond, respectively. The prepared nanohybrids was characterized by fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis. A ultrasensitive electrochemical senor based on the prepared nanocomposite for simultaneous detection of o-nitrophenol (o-NP) and p-nitrophenol (p-NP) was developed. The linear response ranges were0.01-5.00μM and5-150μM with the detection limits were0.019μM for o-NP and0.023μM for p-NP, respectively. The proposed senor has many advantages, such as good selectivity, stability and reproducibility, which was successfully applied to the detection of o-NP and p-NP in water samples with satisfactory results, demonstrating it is a promising method for selective detection of environmental pollutants with practical application value.(4)Graphene was prepared by chemical reduction method and characterized by fourier transform infrared spectroscopy and the modificated electrode was characterized by transmission electron microscopy and electrochemical impedance. Poly(N-acetylaniline)(PNAAN1) and β-CD were covalently bound on the electrode surface. A sensitive and selective electrochemical approach for cholesterol sensing based on a competitive host-guest recognition between-cyclodextrin-CD) and signal probe/target molecules using-CD/PNAANI/graphene-modified electrode was developed. A linear response range of1.00to50.00M for cholesterol with a low detection limit of1.168 M (S/N=3) was obtained by using the indirectly method. The developed detection method is important as it does not use any enzyme or antibody for detection selectivity and sensitivity. Besides, it is simple, fast and sensitive, compared with the traditional methods. The sensor was successfully applied to the detection of cholesterol in serum sample with satisfactory results, indicating it is a promising method for cholesterol detection in clinical examination with practical application value.