Chunli Bai

Investigation of the interaction between acridine orange and bovine serum albumin

The results from the measurement of the fluorescence spectrum showing the binding characteristics of acridine orange (AO) and bovine serum albumin (BSA) are reported. It was found that the equilibrium constant k=4848.64 l mol(-1), and the number of binding sites n=0.82. Based on the mechanism of the Forster energy transference, the transfer efficiency of energy and distance between the acceptor AO and BSA were found. The interaction between AO and BSA have been verified as consistent with the static quenching procedure and the quenching mechanism is related to the energy transfer.

The observation of the local ordering characteristics of spermidine-condensed DNA: atomic force microscopy and polarizing microscopy studies.

Condensation of DNA by multivalent cations can provide useful insights into the physical factors governing the folding and packaging of DNA in vivo. In this work, local ordered structures of spermidine-DNA complexes prepared from different DNA concentrations have been examined by using atomic force microscopy (AFM) and polarizing microscopy (PM). Two types (I and II) of DNA condensates, significantly different in sizes, were observed. It was found that for extremely dilute solutions (DNA concentrations around 1 ng/microl or below), the DNA molecules would collapse into toroidal structures with a volume equivalent to a single lambda-DNA (type I). In relatively dilute solutions (DNA concentrations between 1 and 10 ng/microll), a significantly larger structure of multimolecular toroids (circular and elliptical, type II) were formed, which were constructed by many fine particles. Measurements show that the average diameter of these fine particles was similar to the outer diameter of the monomolecular toroids observed in extremely dilute solutions, and the thickness of the multimolecular toroids had a distribution of multi-layers with height increments of 11 nm, indicating that the multimolecular toroidal structures have lamellar characteristics. Moreover, by enriching the DNA-spermidine complexes in very diluted solution, branch-like structures constructed by subunits were observed by using AFM. The analysis of the pellets in polarizing microscopy reveals a liquid-crystal-like pattern. These observations suggest that DNA-spermidine condensation could have multiple stages, which are very sensitive to the DNA and spermidine concentrations.

The gas sensitivity of a metal-insulator-semiconductor field-effect-transistor based on Langmuir–Blodgett films of a new asymmetrically substituted phthalocyanine

Abstract Langmuir–Blodgett (LB) films of an amino-tri- tert -butyl-phthalocyanine (AmBuPc) were fabricated as the semiconductor thin layer for a metal-insulator-semiconductor field-effect-transistor (MISFET). The gas sensitivity of the low-conducting LB films MISFET was measured in a NO 2 atmosphere at different concentration. The results showed that the gas concentration and the drain-source current of the AmBuPc gas sensor satisfy Langmuir adsorption isotherm.

Molecular Superlattices Induced by Alkyl Substitutions in Self-Assembled Triphenylene Monolayers

The configuration of the superlattices, formed from liquid-crystalline molecules on a graphite surface, are controllable through their alkyl substituents. This control may be attributed to the interplay of molecular steric interaction and the 2 D crystallization of alkyl chains. Two such lattices, as observed by STM, are shown in the accompanying graphic (C12- and (inset) C14-substituted molecules).

Controllable AuPt bimetallic hollow nanostructures

We describe a facile procedure for one step, large-scale synthesis of AuPt bimetallic hollow tube-like 1-D nanomaterials and hollow nanospheres, which can be easily manipulated by merely changing the concentration of citric acid.

Self-assembled two-dimensional hexagonal networks

A new compound, 1,3,5-tris(carboxymethoxy)benzene, which forms infinite two-dimensional hexagonal networks, has been synthesized. Its self-assembly behavior at gas–solid interfaces has been studied by scanning tunneling microscopy.

Atomic Force Microscopy Analysis of Intermediates in Cobalt Hexammine-Induced DNA Condensation

Abstract The packaging pathway of cobalt hexammine-induced DNA condensation on the surface of mica was examined by varying the concentration of Co(NH3)6 3+ in a dilute DNA solution and visualizing the condensates by atomic force microscopy (AFM). Images reveal that cobalt hexammine-induced DNA condensation on mica involves well-defined structures. At 30 μM Co(NH3)6 3+, prolate ellipsoid condensates composed of relatively shorter rods with linkages between them are formed. At 80 μM Co(NH3)6 3+, the condensed features include toroids with average diameter of ∼240 nm as well as U-shaped and rod-like condensates with nodular appearances. The results imply that the condensates, whether toroids, U-shaped or rod-like structures have similar intermediate state which includes relatively shorter rod-like segments. The average size of the condensed toroids after incubated at room temperature for 5 h (∼240 nm) is much larger than that incubated for 0.5 h (∼100 nm). The results indicate that the condensation of DNA by Co(NH3)6 3+ is a kinetic-controlled process.

Direct observation of C60 LB film with scanning tunneling microscopy

Abstract We report the direct imaging of monolayer LB film of C 60 . The LB film was prepared onto an Au(100) surface by the vertical dipping method for scanning tunneling microscopy (STM) measurements. Ordered arrays of C 60 molecules and close-packed molecular aggregation in the film are shown on the STM images. The calculated diameters along two mutually perpendicular directions in the arrays are 0.635±0.013 and 0.572±0.024 nm, respectively. Our results demonstrate that the molecular shape of C 60 is easily compressed into an ellipsoid while forming the LB film.

Photoinduced organic nanowires from self-assembled monolayers

The self-assembled diacetylene molecular monolayer was prepared on highly oriented pyrolitic graphite and observed by scanning tunneling microscopy. Upon applying ultraviolet irradiation, the self-assembled conjugated polydiacetylene nanowires resulting from photoinduced topochemical reaction of diacetylene molecules were obtained. Control of the spacings between nanowires was achieved by a simple coadsorption method. The result presented here may supply a general method to obtain spacing-controllable organic nanowires.

Progress of Nanoscience and Nanotechnology in China

Nanoscience and nanotechnology has been attracting wide attention and is becoming an active frontier area. Chinese scientists have followed with the main stream interest in the development of Nanoscience and nanotechnology since its initial stage. In the present paper, the achievements and present status of China in relative researches such as nanomaterials, nanodevices and characterization of nanostructure are described.