Fang Zuo

A Novel Approach to Molecular Recognition Surface of Magnetic Nanoparticles Based on Host–Guest Effect

A novel route has been developed to prepared β-cyclodextrin (β-CD) functionalized magnetic nanoparticles (MNPs). The MNPs were first modified with monotosyl-poly(ethylene glycol) (PEG) silane and then tosyl units were displaced by amino-β-CD through the nucleophilic substitution reaction. The monotosyl-PEG silane was synthesized by modifying a PEG diol to form the corresponding monotosyl-PEG, followed by a reaction with 3-isocyanatopropyltriethoxysilane (IPTS). The success of the synthesis of the monotosyl-PEG silane was confirmed with1H NMR and Fourier transform infrared (FTIR) spectroscopy. The analysis of FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the immobilization of β-CD onto MNPs. Transmission electron microscopy (TEM) indicated that the β-CD functionalized MNPs were mostly present as individual nonclustered units in water. The number of β-CD molecules immobilized on each MNP was about 240 according to the thermogravimetric analysis (TGA) results. The as-prepared β-CD functionalized MNPs were used to detect dopamine with the assistance of a magnet.

Redox-responsive Inclusion Complexation between β-Cyclodextrin and Ferrocene-functionalized Poly(N-isopropylacrylamide) and its Effect on the Solution Properties of this Polymer

Ferrocene-functionalized polymers (poly(NIPAM/FCN)) and their β-CD (β-Cyclodextrin) complex have been prepared. The inclusion complexation between them was investigated by several techniques, including 1H NMR spectra, cyclic voltammetry, UV–vis spectra and dynamic light scattering measurements. The results showed that β-CD could interact with the reduced ferrocene side groups and hardly affect the oxidized form. Thus a redox-responsive inclusion complexation system based on β-CD and poly(NIPAM/FCN) was obtained. In addition, the effect of this inclusion complexation on the solution properties of this polymer was also investigated. LCST (lower critical solution temperature) increased and the viscosity decreased upon addition of β-CD into the reduced polymer solution due to the disruption of the hydrophobic interaction between the ferrocene side groups by the inclusion complexation. Yet LCST and viscosity of the oxidized polymer solution changed slightly, which resulted from the weak interaction exerted by β-CD.

Temperature/Light Dual‐Responsive Inclusion Complexes of α‐Cyclodextrins and Azobenzene‐Containing Polymers

Three kinds of photoresponsive copolymers with azobenzene side chains were synthesized by radical polymerization of N‐4‐phenylazophenylacrylamide (PAPA) with N‐isopropylacrylamide (NIPAM), N,N‐diethylacrylamide (DEAM) or N,N‐dimethylacrylamide (DMAM) respectively. Their structures were characterized by FT‐IR, 1H‐NMR and UV/Vis spectroscopy. Their reversible photoresponses were studied with or without α‐cyclodextrin (α‐CD), which showed that both the copolymers and their inclusion complexes with α‐CD underwent rapid photoisomerization. The lower critical solution temperature (LCST) of the copolymers and their inclusion complexes with α‐CD were investigated by cloud point measurement, which showed that the LCST of three kinds of copolymers increased largely after adding α‐CD. After UV irradiation on the solutions of copolymers and their inclusion complexes, the LCST of the copolymers increased slightly with the absence of α‐CD, while decreased largely with the presence of α‐CD. Furthermore, the LCST reverted to its originality after visible light irradiation. This change of LCST could be reversibly controlled by UV and visible light irradiation alternately. In particular, in the copolymer of PAPA and DMAM, the reversible water solubility of the inclusion complexes could be triggered by alternating UV and visible light irradiation.

Green and Facile Synthesis of Gold Nanoparticles Stabilized by Chitosan

A green and facile method has been developed to prepare gold nanoparticles (Au NPs) coated by chitosan in aqueous solutions. Herein, Au NPs capped with chitosan which acted as both the reducing and stabilizing agents were prepared through a two-step route at low temperature. HAuCl4 and chitosan initially reacted for 6 h at room temperature, and subsequently the mixture reacted for another 1 hour at 35°C. Ultraviolet visible spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction spectroscopy results confirmed the presence of Au NPs. Transmission electron microscopy indicated that the nanoparticles were dispersed individually. The analysis of thermogravimetric analysis and Fourier transform infrared spectroscopy showed that chitosan was capped on the surface of Au NPs.