Characterization of Palladium Nanoparticles by Using X-ray Reflectivity, EXAFS, and Electron Microscopy

Journal Article · Sun Jan 01 04:00:00 EST 2006 · Langmuir

DOI:https://doi.org/10.1021/la052686k· OSTI ID:914111

Sun, Y; Frenkel, A; Isseroff, R; Shnobrun, C; Forman, M; Shin, K; Koga, T; White, H; Zhang, L

We compared the characteristics of dodecanethiolate palladium nanoparticles synthesized by two different techniques, a one-phase method and a two-phase method. From transmission electron microscopy (TEM), we determined that the particle sizes were 46 {+-} 10 Angstroms and 20 {+-} 5 Angstroms for the one- and two-phase particles, respectively. Electron diffraction confirmed that their structure was face-centered cubic (fcc). The lattice constant a{sub 0} was 3.98 {+-} 0.01 Angstroms and 3.90 {+-} 0.01 Angstroms for the one- and two-phase particles, respectively. High-resolution TEM (HRTEM) showed that the one-phase particles had an ordered core surrounded by a disordered shell structure, while the two-phase particles appeared to be crystalline throughout. The particles were also analyzed with extended X-ray absorption fine structure (EXAFS). A cuboctahedral fcc model was used to fit the data, which implied particle sizes of less than 10 Angstroms for both the one- and two-phase particles. The discrepancy between the two techniques was attributed to the presence of a disordered phase, which we presumed was composed of Pd-S compounds. Compared with the bulk palladium, lattice expansion was observed in both one- and two-phase particles by electron diffraction, HRTEM, and EXAFS. At the air/water interface, a uniform film that produced surface pressure/area isotherms could only be obtained from the two-phase particles. The one-phase particles did not wet the water surface. X-ray reflectivity data indicated that the Langmuir monolayer of the two-phase particles was only 13 Angstroms thick. TEM revealed the diameter of the particles in this layer to be 23 Angstroms; hence the particles assumed an oblate structure after spreading. EXAFS examination of a stack of 750 Langmuir monolayers indicated far fewer Pd-S compounds, which may have dissolved in the water. The data were consistent with a model of a monolayer of truncated cuboctahedron Pd particles that were 7 Angstroms thick and 19 Angstroms in diameter.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 914111
• Report Number(s): BNL--78679-2007-JA
• Journal Information: Langmuir, Journal Name: Langmuir Vol. 22; ISSN LANGD5; ISSN 0743-7463
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
FCC LATTICES
NANOSTRUCTURES
ORDER PARAMETERS
ORGANOMETALLIC COMPOUNDS
PALLADIUM COMPLEXES
PALLADIUM SULFIDES
PARTICLE SIZE
THICKNESS
WETTABILITY
national synchrotron light source