The lowest-energy structures and the electronic properties of CdnSn （n = 1 - 8） clusters have been studied by using denslty-functional theory simulating package DMol^3 in the generalized gradient approximation （GGA）. The ring-like structures are the lowest-energy configurations for n = 2, 3 and the three-dimensional spheroid configurations for n = 4 - 8. The three-dimensional structures may be considered as being built from the Cd2S2 and Cd3S3 rings. Compared to the previous reports, we have found the more stable structures for CdnSn（n = 7, 8）. Calculations show that the magic numbers of CdnSn （n = 1-8） clusters are n = 3 and 6. As cluster size increases, the properties of CdnSn clusters tend to bulk-like ones in binding energy per CdS unit and Mulliken atomic charge, obtained by comparing with the calculated results of the wurtzite and zinc blende CdS for the same simulating parameters.
Composite C60-LB films were fabricated by the Langmuir-Blodgett (LB) technique, their micro- structures, micro- and macro-tribological properties were investigated using atomic force microscope/ friction force microscope (AFM/FFM). The results showed that in the confined C60-LB films there were two kinds of structures for the special C60 assembly: grain diameters of one kind were in the range of 150 -230 nm; the other was smaller than 20 nm. Mi- cro-tribological studies showed that topographical images of tiny C60 aggregates (<20 nm) were con- sistent with their frictional ones very well, namely, low friction occurred on tiny C60 aggregates compared with fatty chains LB monolayer, and ‘Micro-rolling effect’ was apparent; but for big large ones frictional forces were relatively high and ‘ratchet mechanism’ was seen apparently. Macro-tribological data proved large C60 aggregates had wear resistance and load-carrying capacities and anti-wear lives for com- posite C60-LB films were prolonged greatly with dis- persibility of C60 improved and its grain diameter re- duced. Tiny C60 aggregates were mainly the lubri- cating agents. Friction coefficients of composite C60-LB films gradually reduced with loads increasing having the same friction coefficient-load relations with boundary lubrication films.
YANG Guanghong ZHANG Xingtang XUN Jun JIANG Xiaohong ZHANG Pingyu DU Zuliang
Titanic acid nanotubes(H_(2)Ti_(2)O_(4)(OH)_(2))were surface-modified with cetyl alcohol through dehydration reaction because of existence of Ti–OH.The modified nanotubes were characterized by transmission electron microscopy(TEM),Fourier Transform Infrared(FT-IR)spectrometry and pho-toluminescence(PL)spectra.The results indicate that the modified nanotubes can be easily dis-persed into organic solvent such as chloroform and toluene in contrast with the unmodified nanotubes,which makes it easier to be assembled by LB technique.Moreover,the Ti-O-CH_(2)(CH_(2))_(14)CH_(3) on the surface of the nanotubes can hinder the adsorption of water and consequently the photoluminescence property of the nanotubes can be stabilized.Even though kept in humid condition or in air for a long time,the modified nanotubes also maintain the special photoluminescence property in the visible region.
