Showing papers by "Hua Zhang published in 1999"

Monitoring the Electrochemical Transformation of an Azobenzene-Terminated Alkanethiolate Monolayer at Gold by Chemical Force Microscopy

Abstract: Chemical Force Microscopy (CFM) was used to study the electrochemical behavior of azobenzene-terminated self-assembled monolayers (SAMs). Both the gold-coated AFM tip and the gold-coated silicon substrate were modified with a 4-((N-(2′-mercapto-ethyl)-amino) carbonyl) azobenzene monolayer. For such a system, only when the reduction/oxidation reaction of azobenzene group occurs, the adhesion force between the tip and sample shows a drastic change, demonstrating the ability of CFM in monitoring the electrochemical transformation of an azobenzene group.

The 6-(10-Mercaptodecoxyl)quinoline Self-Assembled Monolayer on Gold: Spectroscopy and Wettability Investigation.

Abstract: A self-assembled monolayer (SAM) with an exposed basic group has been generated by the adsorption of a novel quinoline derivative 6-(10-mercaptodecoxyl)quinoline (MDQ) on a gold surface. The structure and surface properties of the SAMs of MDQ were characterized by ellipsometry, reflection absorption FTIR (RA-IR), and contact angle titration. It was found that the quinoline moiety of MDQ forms an ordered layer on the top of the film and the alkyl chain exhibits a packing density similar to that of a monolayer of decanethiol. The molecular orientation of MDQ in SAMs was evaluated by RA-IR spectroscopy which indicates that the alkyl chain exhibits a tilting angle of 24 ± 4° with respect to the surface normal and a twisting angle of 50 ± 5° around its axis. Contact angle titration in the pH range between 2 and 12 illustrates that the surface of SAM of MDQ is less hydrophilic for acidic solution than for basic solution, which is in contrast with the previous reports on SAMs that basic groups are located at the ends of the molecules.

Chemical Force Titration of Conjugated Pyridyl Group-Terminated Self-Assembled Monolayers

Abstract: Chemical force microscopy (CFM) was used to follow the dissociation process of 4-mercapt-opyridine (4-MP) self-assembled monolayers (SAMs) on gold. The force probe was an Au-coated Si3N4 tip modified with 4-MP SAM. The adhesion force between tip and substrate was found to be a function of solution pH. The pK1/2 value of surface pyridyl groups of 4-MP SAM obtained from force titration curve was 5.4, remarkably different from the conventional contact angle titration result (pK1/2=3.3). This difference is believed to arise from the difference in spatial resolution of two approaches. The force titration would probe the local dissociation properties of surface groups, while the contact angle titration reflects the average dissociation properties underneath the water droplet.

Relationship between serum fibrosis markers and fibrosis quantitative analysis of liver tissue

Abstract: OBJECTIVE To study relation of serum fibrosis markers with quantitative analysis of liver tissue. METHODS We studied the area of reticular fibrin, collagen fibrin and elasticity fibrin in 77 patients with chronic liver disease using color image analysis system. RESULTS From S0 to S4, the area of three kinds of liver fibrosis were all escalate, especially collagen fibrosis. Prominent differences existed between S3 and S2, S2 and S1, S1 and S0. There was a good correlation between the serum fibrosis markers and area of collagen fibrosis of liver tissue, r = 0.70775(HA), 0.59402(CIV), 0.52593(LN), 0.52198 (hPCIII). CONCLUSIONS Serum fibrosis markers have affirmative value to help diagnose liver fibrosis.

Serological character of hepatitis E virus mutants

Abstract: OBJECTIVE 64 sera with serologically negative nonA-E were tested for HEV RNA and their serological characteristics were studied. METHODS HEV RNA was tested by a reverse transcriptase PCR(RT-PCR) and the positive PCR products were cloned and sequenced. Of 15 patients positive for HEV RNA, 6 were followed up and tested for anti-HEV. RESULTS 15 of them(23.4%) were HEV RNA positive. 9 of the 15 HEV sequences have 95% homology and the remaining 6 have only 80% homology as compared with the Chinese HEV strain at the nucleotide level. Of 15 patients positive for HEV RNA, 6 were followed up. 3 of 4 patients infected with typical HEV had anti-HEV seroconversion 1 month after infection and 2 patients infected with HEV mutants were persistently negative for anti-HEV 1 or 3 months after infection. CONCLUSION The Commercial anti-HEV EIA Kit can not detect HEV mutants.

Sol-Gel Derived Titaniajormosil Composite Thin Films For Optical Waveguide Applications

Abstract: We report the preparation of sol-gel waveguide films based on a newly developed recipe to incorporate organic molecules into the inorganic sol-gel glass matrix. The film was derived from a sol that has a higher titanium content in an organically modified silane (ORMOSIL), namely, y-Glycidoxypropyltrimethoxysilane. We have shown that using spin-coating and low temperature baking, a single coating layer can have a thickness of more than 1.5 μm. When such a single layer film is deposited on a microscope glass slide or a piece of silicon with a buffercladding layer, it is able to support the guiding of optical waves. We have characterized the film using scanning electron microscopy, atomic force microscopy, X-ray diffractometry, thermal gravimetric analysis. differential thermal analysis and Fourier transform infrared spectroscopy and have studied the properties of the waveguide film, including the microstructural properties. the chemical bonding properties, and the optical properties. Based on these experimental results, we found that a heat-treatment at a temperature slightly below 200°C is necessary to attain a dense pore-free film. It has also been noted that a purely inorganic and crack-free silica-titania film can be obtained after baking the titania-ORMOSIL composite film at 500°C or higher.

A Novel Organic Complex Thin Film for Rewritable Optical Storage

Abstract: Erasable optical storage on an organic complex thin film m-nitrobenzal malononitrile and diamine benzene (m-NBMN/DAB) has been demonstrated High contrast pattern can be produced by 780 nm laser pulses and can be erased by heating The static optical recording characteristics were studied by the homemade static characterizer, and the structural properties of the thin films were investigated by the high resolution scanning electron microscope (HRSEM) and transmission electron microscope (TEM)