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Pd and Ag Nanoparticles

Principal Investigator:
Professor Dan Buttry, Dept of Chemistry/Biochemistry, ASU

Graduate Students:
Koski, Kristie Lamb, Tim
Singh, Poonam
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MST Fellows:
Cheeney, Mary, North H.S. PUHSD
Purington, Robert, Saint Mary's High School, Phoenix
Turley, Keri, Westwood H.S., Mesa
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Introduction

Produce and characterize Pd nanoparticles using H2Pd2Cl4, ATP as ligand, NaBH4 as reductant.
Use UV-Vis Spectrometry and Atomic Force Microscopy to characterize the nanoparticles
We are also sythesizing Ag nanoparticles using the same wet chemistry process (different proportions) with Ag nitrate. We are placing these AgNP into agarose gels of various concentrations to find the best system to use. We have used the AFM and UV-VIS to analyze these particles - and Brillouin scattering with the laser set-up.We would like to determine the surface tension of the outer particles of the AgNP.

Synthesis

Nanoparticles are solid, typically precious metal crystals. Their diameters are of the range of 1 to 100 x 10-9 meters (1 to 100 nM). Practical use is s catalysts in fuel cells and catalytic elements of biological sensors, or batteries, partly because they offer very high catalytic activity per mass of precious metal, which can drastically cut capital costs. Theoretical interest is because, in small sizes (1 to 10 nM), quantum-mechanical effects may become significant, the entire particle may act as a single atom with synchronized electronic energy bands (surface plasmon bands).

This research is: production (synthesis), and characterization of palladium (Pd) nanoparticles (nP’s) in acidic, aqueous solution, both of the particles and their kinetics and stability.

Pd nP’s are synthesized by the following protocol:

Provide 10 milli Molar solution of the metal ion with a variable amount of adenosine triphosphate (ATP) in 3.5 ml of 18 MΩ-cm water. Mole ratios of metal to ATP vary from 1:0.1 up to 1:20. The water solution is made partly with ml syringe and partly with µL syringes. Chemical solutions are added with µL syringes. So acidic chloride salt of the metal, and ATP are added to water and stirred magnetically for 30 minutes. This is to match existing literature protocol.

Thereafter, the reductant, sodium borohydride (NaBH4) is weighed to provide a known molarity solution, and specific mole ratios of reductant to metal are established by addition of the solution with µL syringes, the mole ratios of metal to reductant, approx. 1:10, 1:20, 1:30. This causes a color change of the solution immediately on addition. The literature states that ATP ligand moderates and limits the growth of the metal crystal nP's and prevents clumping. Reaction could be:

H2PdCl4 -> 2H+ + Pd2+ + 4Cl- ; pH around 1-2, and

NaBH4 -> Na+ + BH4- both in aqueous solution

The borohydride is a hydride ion donor. The hydride ion gives up its electron (is oxidized) while the metal ion gains back and electron (is reduced to the metal).

Mechanism not shown, net equation:

2H- + Pd+2 -> H2(g) + Pd(m)

The particles are allowed to grow over hours or days and then characterized by UV-Vis spectrophotometry or Atomic-Force-Microscopy (AFM), or such other methods (Brillion laser scattering) as may show whether nP's formed.

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