Influence of solvent quality on surface forces between polystyrene layers adsorbed onto mica

Abstract

(about 40 nm) and small size (about 10 nm). The particle size in o-xylene was about 20 nm, while that in p-xylene was about 75 nm. In valeric acid, dimethyl sulfoxide, and caproic acid, relatively larger palladium particles were obtained in the range 60-100 nm. Thus, the fact that relatively larger particles are prepared in organic solvents whose boiling points are much higher than that of methyl isobutyl ketone indicates the nucleation of palladium seems not to proceed rapidly, but the nuclear growth occurs in an organic solvent with a higher boiling point, resulting in a larger particle size of palladium. Since very stable palladium particles were obtained in methyl isobutyl ketone, the effect of concentration of P d ( a ~ a c ) ~ on the particle size of palladium was studied in methyl isobutyl ketone where the concentration of Pd(acac)2 was between 0.1 and 1.0 mmol dn~-~ . Figure 2 shows that the average diameter of palladium is nearly independent of the concentration of P d ( a ~ a c ) ~ and ranges between 8 and 10 nm. The effect of refluxing time on the particle size of palladium was also studied. Figure 3a shows that the average diameter of palladium is almost constant in all the refluxing times studied. Further, Figure 3b shows that the absorbance of palladium particles in methyl isobutyl ketone increases with an increase of the refluxing time, suggesting that the number of palladium particles increases since the particle diameter is almost constant over a whole refluxing time. It is concluded from the above results that the thermal decomposition of P d ( a ~ a c ) ~ in methyl isobutyl ketone gives relatively monodispersed palladium particles whose stability is considerably high. The particle diameter ranges between 8 and 10 nm. Further, it is also expected that many organo precious metal particles can be prepared in organic solvents from decomposition of their corresponding organic complexes.