Papers by Author: He Sun Zhu

Abstract: Boron carbide nanobelts have been synthesized successfully by carbothermal growth method. Boron oxide, activated carbon, gallium oxide and sodium chloride in the molar ratios of 1: 5: 0.03: 0.2 were used as raw materials. The width and thickness of the nanobelts range from 1 to 10 μm, and 80 to 150 nm respectively. The length is up to 50–200 μm. Diffraction peaks in the XRD pattern can be indexed to rhombohedral boron carbide with lattice parameters of a=5.616Å, c=12.067 Å. SAED pattern recorded along [ 010 ] zone axis shows (104 ) growth direction. A vapor–liquid–solid (VLS) growth process on the active catalyst surface is supposed to interpret the growth mechanism of as–synthesized nanobelts.

Abstract: A novel prosthesis using silk fibroin with blending heparin and sulfonated silk fibroin was studied. Anticoagulation activities of heparin/silk fibroin and sulfonated silk fibroin/silk fibroin vascular and mechanical property results showed that heparin/silk fibroin and sulfonated silk fibroin/silk fibroin vascular could meet the requirement of small caliber grafts. This study indicated that silk fibroin could be used for developing tissue engineering biological vascular grafts that could use for human coronary or low extremity artery bypasses.

Abstract: Tetramethylpyrazine(TMPZ) is an active ingredient of a Chinese herbal medicine Chuanxiong (Liqusticum wallichii Franchat). In order to enhance its stability and delivery in vivo TMPZ-capped poly(ethylene glycol) conjugate was designed and synthesized efficiently by the condensation reaction of 2-cardoxyl-3, 5, 6-trimethylpyrazine (TMPZCOOH) with PEG(M=2000) in the presence of dicyclohexylcarbodiimide (DCCI). The TMPZ-PEG conjugate obtained was then purified by gel filtration chromatography (SephadexG-15 column,1.6×100cm; eluent: distilled water) and characterized by FTIR, UV spectra. FTIR (KBr): 2868cm-1(CH2), 1718cm-1(C=O), 1455cm-1 (-C=N-), 1113cm-1(O-CH2-CH2). The degree of end-capping of TMPZ per PEG molecules was estimated to be 87% from UV absorbance at 294nm. The anticoagulant activity of the conjugate was evaluated by in vitro coagulation time test. The result showed that the activated partial thromboplastin time (APTT) of the TMPZ-PEG conjugate is nearly equal to that of blank plasma in our experiment conditions, this behavior is similar to that of TMPZ. But TMPZCOOH, one of the main metabolic products of TMPZ in vivo, exhibited more potent anticoagulant activity than TMPZ and TMPZ-PEG, its APTT is even larger than the maximum clotting time set by the instrument. It is also found that APTT of the conjugate increased as the time of the sample stayed in water bath at 37°C. This is probably because the ester bond between TMPZCOOH and PEG hydrolyzed during the stay time and released the free TMPZCOOH.

Abstract: The silk fibroin blend membranes were prepared by adding a small amount of poly (vinyl alcohol) (PVA) and heparin. By controlling the preparation conditions, the tensile strength and elongation at break reached to 8.86 MPa and 231.8%, respectively. Meanwhile the in vitro antithrombogenecity significant increased. The clot times (APTT, TT and PT) all exceeded the measurement limit of clot detection instrument. It is expectable using these natural materials to prepare small caliber vessel.

Abstract: The citric acid (CA) was added to the silk fibroin and Polyvinyl Alcohol (PVA) copolymer system. The blending 4% PVA was for improving the mechanical properties of the silk fibroin films. Citric acid amount varies from 0.5% to 2% of weight. The antithrombogenecity was characterized by in vitro clot time of prothrombin time (PT), the Activated partial thromboplastin time (APTT) and thrombin time (TT). The mechanical properties of the blending films were measured and the tensile strength and breaking elongation of films reached to 25.3MPa and 102%. The anticoagulant property results indicated that APTT and TT prolonged significantly, but PT has no effective change. We discussed the relationship between the structure and properties and proposed an anticoagulant mechanism.

Abstract: Carbon nitride films were grown on Si substrates by a microwave plasma chemical vapor deposition method, using mixture of N2, CH4 and H2 as precursor. Scanning electron microscopy shows that the films consisted of a large number of hexagonal crystallites. The dimension of the largest crystallite is about 3 µm. The X-ray photoelectron spectroscopy suggests that nitrogen and carbon in the films are bonded through hybridized sp2 and sp3 configurations. The X-ray diffraction pattern indicates that the major part of the films is composed of α-, β-, pseudocubic C3N4 and graphitic C3N4. The Raman peaks match well with the calculated Raman frequencies of α- and β-C3N4, revealing the formation of the α- and β-C3N4 phase.

Abstract: Silicon carbon nitride (SiCN) films have been deposited on silicon wafers by microwave plasma chemical vapor deposition (MPCVD). Gas mixture of H2, CH4, N2, and SiH4 was used as precursors, in which the flow rate of N2 was changed. X-ray photoelectron spectroscopy (XPS) and micro-Raman spectroscopy were employed to characterize the composition and bonding structures, while field-emission scanning electron microscopy were used to investigate the microstructure of the films. With increasing the flow rate of N2 from 50 sccm to 300 sccm, the SiCN films changed from amorphous to nanocrystalline. Characteristic current-voltage measurements indicate a low turn-on field of 10.8 V/µm. Field emission current density of 4.5 mA/cm2 has been observed at 20 V/µm.

Abstract: Nanorods of a compound semiconductor, BiOCl, have been prepared from BiCl3 solutions containing a nonionic surfactant, t-octyl-(OCH2CH2)xOH, x=9, 10 (Triton X-100). Powder X-ray diffraction (XRD) pattern indicated that the product was pure tetragonal phase bismoclite (BiOCl). The product was also characterized by the techniques of scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscope (TEM). The as-obtained BiOCl nanorods possess mean diameters less than 40nm and lengths ranging in 160-400nm. Selected area electron diffraction (SAED) pattern showed the single-crystal nature of as-prepared BiOCl nanorods. The growth mechanism of BiOCl nanorods has also been proposed.