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357 results on '"Zhu, Hesun"'

49. Preparation of non-woven mats from all-aqueous silk fibroin solution with electrospinning method

Author

Cao Chuanbao, Ma Xilan, Tang Yin, Zhu Hesun, and Chen Chen

Subjects
chemistry.chemical_classification, Materials science, Aqueous solution, Polymers and Plastics, fungi, Organic Chemistry, Stress–strain curve, technology, industry, and agriculture, Fibroin, Polymer, Electrospinning, Random coil, Differential scanning calorimetry, chemistry, Materials Chemistry, Fourier transform infrared spectroscopy, Composite material
Abstract

In the present study, we successfully prepared non-woven mats from stable regenerated silk fibroin aqueous solution at high concentration. Scanning electronic microscope (SEM) was used to observe the morphology of the fibers. The structure of the fibers was characterized using Fourier transform infrared (FTIR), wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The mechanical tests were also performed. In the as-spun fibers, silk fibroin was present in a random coil conformation, the stress and strain at break were 0.82 MPa and 0.76%, respectively, while after methanol treatment, the silk fibroin was transformed into a β-sheet-containing structure, the stress and strain at break increased to 1.49 MPa and 1.63%, respectively. This study provided an option for the electrospinning of silk fibroin without using organic solvent or blending with any other polymers, which may be important in tissue engineering scaffold preparation.

Published
2006

50. Surface atomic structures of Fe2O3nanoparticles coated with cetyltrimethyl ammonium bromide and sodium dodecyl benzene sulphonate: an extended x-ray absorption fine-structure study

Author

Li Qian-Shu, Wu Zhonghua, Guo Lin, and Zhu Hesun

Subjects
Ammonium bromide, Extended X-ray absorption fine structure, Absorption spectroscopy, Inorganic chemistry, Analytical chemistry, Oxide, Nanoparticle, Condensed Matter Physics, chemistry.chemical_compound, chemistry, Nanocrystal, Particle, General Materials Science, Absorption (chemistry)
Abstract

Fe2O3 nanoparticles coated with sodium dodecyl benzene sulphonate (DBS) or cetyltrimethyl ammonium bromide (CTAB) were prepared by using a microemulsion method in the system water/toluene. The nanoparticles were characterized by means of transmission electron microscopy and average particle sizes of 5.0 nm and 6.0 nm were found for DBS-modified and CTAB-modified nanoparticles respectively. The local atomic structures of these iron(III) oxide nanoparticles were probed by using the extended x-ray absorption fine-structure technique. Fe K absorption spectra were collected at beam line 4W1B of Beijing Synchrotron Radiation Facility. A structural model was proposed for describing their atomic structures. The Fe-O bond length at the surface of DBS-coated Fe2O3 nanoparticles was found to be similar to that in bulk Fe2O3, but there was about 0.04 A expansion for the CTAB-coated Fe2O3 nanoparticles. On the basis of the model proposed in this paper, the thicknesses of the surface layers were estimated to be 0.5 nm and 0.7 nm, respectively, for the DBS-coated and CTAB-coated Fe2O3 nanoparticles. The anharmonicity of the atomic vibration and the asymmetry of atom-pair distribution were found to be larger at the surface of the nanoparticles than in the bulk material, while the Debye-Waller factors are almost the same for the surface and the core parts of the nanoparticles. It can be concluded that the atomic structure of the nanoparticle surface is ordered, but the atom-pair distribution is asymmetric.

Published
1999

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