CATALYTIC SURFACES FROM LANGMUIR-BLODGETT-FILMS OF (4,4'-DIISOPROPYLDIBENZYLIDENEACETONE)PALLADIUM(0) AS PRECURSOR .1. STUDY OF THE THERMALCOMPLEX DECOMPOSITION AND FORMATION OF PALLADIUM PARTICLES

A detailed study is presented on Langmuir and Langmuir-Blodgett (LB) f ilms of '-(diisopropyldibenzylideneacetone)palladium(0)(1) and the the rmal decomposition of these LB films under formation of catalytic pall adium particles. Monolayers of 1 at the air-water interface were chara cterized by their rr-A isotherms, while LB film formation was studied using UV-vis spectroscopy. Thermal decomposition was investigated usin g spectroscopic methods (X-ray photoelectron spectroscopy, UV-vis spec troscopy, and attenuated total reflectance infrared spectroscopy) and microscopic methods (scanning force microscopy). It was found that the spreading of cyclohexane solutions of 1 at the air-water interface le ads to stable monolayers, which can be deposited on hydrophobic suppor ts (e.g., silanized quartz, polyarylate) according to the LB technique . Transfer conditions are optimum at a surface pressure of 7.5 mN m(-1 ) and a subphase temperature of 7.5 degrees C. Monolayers are transfer red during the downstroke and upstroke, the transfer ratio being 1. If the LB films are annealed at 100 degrees C or higher, they gradually decompose under formation of palladium particles whose size is control led by time and temperature of the annealing process. For example, ann ealing at 120 degrees C for up to 3 min leads to formation of palladiu m clusters with absorption maxima at 280, 380, and 420 nm, while a the rmal treatment for 10 min or longer favors the growth of metallic pall adium particles with an average diameter of 22 nm. Simultaneously, the ligand molecules are set from the complex and crystallize on the surf ace under formation of large particles with an average diameter of 250 nm.