Cyclodextrin-Assembled Nano-Interfaces And Their Molecular Recognition Properties Study

The fundamental process of life is a series of molecular recognition at the nanoscale interface, therefore, the study of molecular recognition and mechanism of action at the nanoscale interface is important for exploration of the biological phenomena at the molecular level. The combination of the excellent properties of nanomaterials and the molecular recognition ability of host molecules to design intelligent sensing system is an active line of research, and has contributed to creating a variety of efficient, sensitive, convenient sensing system. Cyclodextrins (CDs) are a class of cyclic oligosaccharides, has a unique structure and molecular recognition characteristics. On the basis of reviewing the molecular recognition properties of CDs and their applications in chemical sensors, this thesis is focused on fabricating novel and efficient CD-functionalized nano-interfaces and exploring their potential applications in molecule recognition.The main contents are shown as following:1. The unique structure and characteristics of cyclodextrin were introduced. The properties and application of semiconductor quantum dots, metal nanoparticles, and nanochannel were outlined. On the basis of the above review we put forward our design ideas and research topics.2. A simple, rapid sonochemical procedure for the preparation of highly fluorescent and water-soluble CdSe/ZnS quantum dots (QDs) usingα-,β-, andγ-CD as surface-coating agents was reported. The functional QDs retained the excellent optical properties of QDs and engaging molecular recognition ability of CDs. These receptor-modified QDs afforded a very sensitive detection system for analysis of phenol isomers. It was found that theα-CD-QDs andβ-CD-QDs were selectively sensitive toward p-nitrophenol and 1-naphthol, respectively. Under optimal conditions, the relative fluorescence intensities ofα-CD-QDs andβ-CD-QDs both decreased linearly with increasing p-nitrophenol and 1-naphthol in the concentration range of 0.01-100μM, with the corresponding detection limits (3σ) of 7.92×10-9 M and 4.83×10-9 M, respectively. However, the sensitivity toward other phenols, including o-nitrophenol, m-nitrophenol, 2-naphthol, o-cresol, m-cresol and p-cresol, were negligible. The results showed that the CD-QDs had a good specificity and excellent anti-disturbance ability.3. A novel chiral fluorescence sensor based on quantum dots was constructed using CD as chiral selector. CDs, with a capability of chiral recognition, were introduced on the surface of CdSe/ZnS QDs by using a simple and convenient sonochemical approach. It has been demonstrated that the CD-QDs can carry out highly enantioselective fluorescent recognition of tyrosine and methionine. Within a certain concentration range, one enantiomer of the chiral amino acids can increase the fluorescence intensity of the CD-QDs, whereas the other enantiomer scarcely influences the fluorescence. Such unusually high enantioselective responses make these CD-QDs very attractive as fluorescent sensors in determining enantiomeric compounds.4. A new colorimetric method base on the surface plasmon resonance of silver nanoparticles (Ag NPs) was demonstrated for determination of rare earth (RE) ions in aqueous solution with high sensitivity and selectivity. A well-stable and dispersed Ag NP probe was synthesized using theβ-cyclodextrin/4,4'-dipyridine (β-CD/4-DPD) supramolecular inclusion complex system as a stable ligand. The recognition ability ofβ-CD/4-DPD-modified Ag NPs for RE ions could be realized by monitoring the UV-vis spectra and color changes of the Ag NPs solution before and after addition of various RE ions. In the presence of Yb3+, Yb3+-induced assembly of theβ-CD/4-DPD-modified Ag NPs to form chainlike supramolecular aggregates, gives a distinct color change from yellow to red and dramatic increase in the absorbance intensity at-610 nm. However, the addition of other RE ions, including Pr3+, Nd3+, Sm3+and Eu3+, no changes in the UV-vis spectra and color of Ag NPs were observed.5. A simple enantioselective sensing nanodevice based on a single conical nanochannel was fabricated in a PET membrane. Chiral recognition elements (β-CD molecules) were incorporated into the channel by directly exploiting the carboxyl groups generated during the track-etching process. The modified nanochannel provided a novel sensing platform to discriminate chiral His based on rectified ionic currents. This successful study is a potential step toward the ability to simulate the process of chiral recognition in living organisms. The artificial nanochannel systems offer real promise for preparing practical chiral-sensing devices that could be employed in a biological environment.