Feifei Xin

Switchable and orthogonal self-assemblies of anisotropic fibers

Anisotropic and well-defined β-cyclodextrin (β-CD) and sodium laurate (SL) gel fibers, with tetragonal and lamellar packing modes respectively, were combined to generate orthogonal and switchable assemblies for the first time. Through controlling the inclusion–exclusion processes between β-CD and SL by changing external stimuli, β-CD gel fibers, SL gel fibers and their coexistence states can be easily tailored. Different assembled states exhibited versatile morphologies and microstructures, which were detected by microscopy and X-ray scattering measurements. Furthermore, controllable assemblies provide facile ways to control the mechanical properties of the hybrid gels. The orthogonal self-assembly with self-sorting properties would enable this system to attract interest in material science.

Sensitive fluorescent vesicles based on the supramolecular inclusion of β-cyclodextrins withN-alkylamino-l-anthraquinone

Self-assembly fluorescent vesicles were designed and prepared based on the supramolecular interaction of cyclodextrins and N-alkylamino-l-anthraquinone (n-AQ). As the guest molecules, n-AQs with alkyl lengths ranging from C0 to C18 were synthesised by the direct reaction of alkylamine with l-nitroanthraquinone in N,N-dimethylformamide. Transmission electron microscopy (TEM), scanning electron microscopy, dynamic light scattering and epi fluorescence microscopy were employed to study the vesicle system in detail. The formation mechanism of the vesicles was suggested based on the results of TEM observation, UV spectrum, fluorescence spectrum, 1H NMR and simulation in the software Materials 4.3. The fluorescent vesicles show sensitive and multi-responsive properties to external stimuli. Based on these properties, we tried to use the vesicle as a new kind of fluorescence staining material for living cells. The vesicles can effectively stain the human breast cancer cells (MCF-7) and mice mononuclear macrophages (REW-264.7). This paper provides a better understanding in the design and preparation of drug delivery, biomaterials and intelligent materials.

Multi-responsive supramolecular organogel with a crystalline-like structure

A multi-responsive cyclodextrin-based organogel with a crystalline-like structure is first reported. An amount of β-cyclodextrin (β-CD) and lithium chloride (LiCl) was added into N,N-dimethylformamide (DMF), and the system obtained could transform instantly from a transparent solution into a gel state by introducing ethylene diamine (EDA), and then the gel could turn into another precipitate-like gel by undergoing a heating-cooling process. Among a series of aliphatic amines, only EDA was found to be able to induce the gel formation. Both the gels possess crystalline-like structures in their morphology with sheet-like layers, in a highly-ordered channel-type packing mode, which were proved by OM, SEM, XRD, and FT-IR measurements. Furthermore, the gel could respond to H(+) and Cu(2+) by transforming into an amorphous precipitate. This research may pave the way for the design of novel smart materials.

Vesicles Prepared from Inclusion Complexes Between Cyclodextrins and Ethyl Benzoate

Ethyl benzoate was found to complex with cyclodextrins in formation of vesicles for the first time. These vesicles were characterized by transmission electron microscopy and dynamic light scattering. The complex stoichiometry, the stability constant and conformations of ethyl benzoate · cyclodextrins in aqueous solution were investigated by ultraviolet and nuclear magnetic resonance analyses. The vesicle system was prepared without complicated synthesis. This kind of vesicles prepared by cyclodextrin inclusion complexes could be applied in many fields.

Fluorescent Vesicular Particles Assembled by Inclusion Complexes Between Cyclodextrins and BPB

Vesicular particles based on inclusion complexes between BPB and γ-HB-β-CDs were prepared and characterized for the first time. The morphologies and sizes were confirmed by transmission electron microscopy (TEM), scanning electron microscope (SEM), and dynamic light scattering (DLS). Particularly, these vesicular particles exhibiting clearly fluorescent dots observed by laser confocal scanning microscopy (LCSM) could be alternative candidates as fluorescent probes and labels being applied to cellular staining, labeling, bio-mimicking and drug delivery. The ultraviolet, fluorescence, and nuclear magnetic resonance (NMR) measurements confirmed the existence of stable 1:1 BPB-γ-HB-β-CD complexes in the system. The vesicular particles were assumed to be constructed by orderly self-aggregates of these inclusion complexes.

A facile method to construct dual-responsive organogels with color changes

A novel organogel that is dually responsive to pH and Li+ was facilely constructed from mixtures of β-cyclodextrin, thymolphthalein and sodium formate in N,N′-dimethylacetamide. Acidity (pH) can trigger a color change of the organogels between a transparent colorless state and a dark-blue state due to the presence of thymolphthalein. It is interesting that Li+ could decompose the gel system while Na+ and K+ do not disturb the gelatinous state. Scanning electron microscopy (SEM) images show that these organogels are composed of fibrous structures. These organogels possess relatively high viscoelasticity indicated by rheology measurements. A mechanism for the gel formation is proposed based on the results of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The systems could be expected to act as non-liquid materials for sensing with the naked eye.

Transformation from a heat-set organogel to a room-temperature organogel induced by alcohols

A unique transformation from a heat-set organogel to a room-temperature organogel induced by ethanol (EtOH) was reported here. When the system containing β-cyclodextrin, 4,4′-isopropylidenediphenol, N,N-dimethylacetamide and LiCl was heated to the gelling temperature (Tgel), a heat-set organogel would be formed. In contrast, a semitransparent organogel (room-temperature organogel) could be obtained by injecting EtOH into the system at ambient temperature. In this transformation process, EtOH played a role in the formation of hydrogen bonds, which was critical for the self-assembly. The influence of other guest molecules, solvents and alcohols on this transformation was also investigated. These organogels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, thermal gravity analysis and differential thermal gravity. Further, the formation mechanism of the organogels was proposed based on the above measurements.

N-(Ferrocenylmethyl)-dodecan-1-amine.

The title compound, [Fe(C5H5)(C18H32N)], was synthesized by the amination of ferrocenecarbaldehyde. In the complex, the two cyclopentadienyl (Cp) rings are almost parallel with a dihedral angle of 1.36 (8)°, and are separated by a centroid–centroid distance of 3.299 (2) Å. In the crystal, adjacent molecules are linked into a one-dimensional supramolecular structure via weak C—H⋯π interactions between the Cp ring H atom and the Cp ring.

2-Isopropyl-3-methyl­quinoxaline 1,4-dioxide

In the title compound, C12H14N2O2, the quinoxaline ring system and the C atoms of the methylene and methyl substituents lie on a mirror plane. The crystal packing is stabilized by weak π–π interactions [centroid–centroid distance = 3.680 (7) Å].