CELL 268 |
| As continuous efforts of the reduction of metal ions on cellulose nanocrystal (CNXL), we have successfully synthesized bimetallic nanoparticles (alloys) on CNXL. Alloys are particularly important in the field of catalysis since they often exhibit better catalytic properties than their monometallic counterparts. Gold is very useful as an alloying metal due to its relatively low reactivity. It was used in conjunction with metals such as Ag, Pd, and Pt. The structure of bimetallic combinations depends mainly on the preparation conditions and the miscibility of the two metal compounds. Co-reduction method of two metal ions using CNXL as a stabilizer produced bimetallic nanostructured particles. Au and Ag have very similar lattice constants and are completely miscible over the entire composition range. Single-phase alloys then can be easily achieved at any desired composition. However, Au/Pd and Au/Pt also produced alloy particles, where Pd or Pt was located on the surface of bimetallic cluster particles. The alloy particles are in the range of 3-10 nm in diameter. The stabilization of bimetallic nanoparticles on CNXL avoids coagulation and precipitation of particles into media. The crystallinity of CNXL was maintained during the reduction of metal ions and no surface oxidation of alloy nanoparticles was observed for months. FE-SEM, TEM, and surface Plasmon resonance (SPR) techniques show that alloy nanoparticles are well-distributed on the surface of CNXL and single crystalline alloys are uniform contrast throughout the particles (Au/Ag), indicating a good atomic level mixing of two metals. We have also observed the formation of 5-hydroxymethyl-2-furaldehyde (HMF), which shows SPR at 283 nm, during the metal ion reduction. The formation of HMF through dehydration of glucose is catalyzed by metal or alloy formed. |
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Nanotechnology: A Fiber Perspective
8:20 AM-11:45 AM, Thursday, April 10, 2008 Morial Convention Center -- Rm. R09, Oral
Division of Cellulose & Renewable Materials |