Viral-templated Palladium Nanocatalysts.
Yang, Cuixian.
2013
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Abstract: Despite recent progress on nanocatalysis, there exist several
critical challenges in simple and readily controllable nanocatalyst synthesis including the
unpredictable particle growth, deactivation of catalytic activity, cumbersome catalyst
recovery and lack of in-situ reaction monitoring. In this dissertation, two novel
approaches are presented for the fabrication of viral-templated... read morepalladium (Pd)
nanocatalysts, and their catalytic activities for dichromate reduction reaction and Suzuki
Coupling reaction were thoroughly studied. In the first approach, viral template based
bottom-up assembly is employed for the Pd nanocatalyst synthesis in a chip-based format.
Specifically, genetically displayed cysteine residues on each coat protein of Tobacco
Mosaic Virus (TMV) templates provide precisely spaced thiol functionalities for readily
controllable surface assembly and enhanced formation of catalytically active Pd
nanoparticles. Catalysts with the chip-based format allow for simple separation and in-situ
monitoring of the reaction extent. Thorough examination of synthesis-structure-activity
relationship of Pd nanoparticles formed on surface-assembled viral templates shows that Pd
nanoparticle size, catalyst loading density and catalytic activity of viral-templated Pd
nanocatalysts can be readily controlled simply by tuning the synthesis conditions. The
viral-templated Pd nanocatalysts with optimized synthesis conditions are shown to have
higher catalytic activity per unit Pd mass than the commercial Pd/C catalysts. Furthermore,
tunable and selective surface assembly of TMV biotemplates is exploited to control the
loading density and location of Pd nanocatalysts on solid substrates via preferential
electroless deposition. In addition, the catalytic activities of surface-assembled
TMV-templated Pd nanocatalysts were also investigated for the ligand-free Suzuki Coupling
reaction under mild reaction conditions. The chip-based format enables simple catalyst
separation and reuse as well as facile product recovery. Reaction condition studies show
that the solvent ratio played an important role in the selectivity of the Suzuki reaction,
and that a higher water/acetonitrile ratio significantly facilitated the cross-coupling
pathway. Meanwhile, in-depth characterizations including Atomic Force Microscopy (AFM),
Grazing Incidence Small Angle X-ray Scattering (GISAXS), Inductively Coupled Plasma Optical
Emission Spectrometry (ICP-OES) and X-ray Photoelectron Spectroscopy (XPS) were carried out
for these chip-based viral-templated Pd nanocatalysts. In the second approach,
catalytically active TMV-templated Pd nanoparticles are encapsulated in readily exploited
polymeric microparticle formats. Specifically, small (1~2 nm), uniform and highly
crystalline palladium (Pd) nanoparticles are spontaneously formed along (TMV) biotemplates
without external reducing agents. The as-prepared Pd-TMV complexes are integrated into the
hybrid poly(ethylene glycol)(PEG)-based microparticles via replica molding (RM) technique
in a simple, robust and highly reproducible manner. The Pd-TMV complex structure was
characterized by Transmission Electron Microscopy (TEM). The hybrid Pd-TMV-PEG
microparticles are examined to have high catalytic activity, recyclability and stability
through dichromate reduction. Combined these findings represent a significant step toward
simple, robust, scalable synthesis and fabrication of efficient biotemplate-supported Pd
nanocatalysts in readily deployable polymeric formats with high capacity in a
well-controlled manner. These two simple, robust and readily controllable approaches for
the fabrication of viral-templated Pd nanocatalysts, in both chip-based and
hydrogel-encapsulated formats, can be readily extended to a variety of other nano-bio
hybrid material synthesis in other catalytic reaction systems.
Thesis (Ph.D.)--Tufts University, 2013.
Submitted to the Dept. of Chemical and Biological Engineering.
Advisor: Hyunmin Yi.
Committee: Jerry Meldon, Maria Flytzani-Stephanopoulos, Terry Haas, and Byeongdu Lee.
Keywords: Chemical engineering, Nanotechnology, and Materials Science.read less - ID:
- m900p625s
- Component ID:
- tufts:22049
- To Cite:
- DCA Citation Guide EndNote
