Environmentally benign or green chemical techniques are growing in importance in academic and industrial research laboratories. Such chemistry has been slow to appear in teaching laboratories due, in part, to a lack of published material on this subject. We have been developing experiments for use in a green organic chemistry course, and present here the methods by which we selected, tested and optimized experiments for this course. As an example, we present a laboratory experiment for the synthesis of adipic acid that was developed from the primary literature. This synthesis utilizes green reagents (hydrogen peroxide as the oxidant), solvents (water) and methods (phase transfer catalysis, catalyst recycling). It provides students a first hand example of environmentally benign synthesis by demonstrating reuse of a product, synthesis using a non-hazardous solvent, elimination of deleterious by-products, and use of a recyclable catalyst.
Poster presentation in the Division of Chemical Education (General Posters)
Accurate measurement of electron transfer (ET) rates requires precise control of the distance between electron donor and acceptor. Measurement of ET through peptides is therefore complicated by the inherent conformational flexibility of proteins. We have developed a peptide-containing alkanethiol thin film model system that allows for the measurement of ET through different peptide fragments (1-3 amino acids in length) whose confirmations are constrained within a molecular assembly that is covalently attached to a gold electrode. We will present evidence from X-ray photoelectron spectroscopy, infra-red spectroscopy, contact angle measurements, and electrochemical experiments that these peptide-containing films possess the requisite order for accurate measurement of ET. We have recently synthesized two families of peptide-containing alkanethiols with pendant redox probes and will present electrochemical characterization of a series of these films containing one through three amides. Initial investigations suggest that the ET rate constant for amide material is higher than for alkanes.
Oral presentation in the Division of Inorganic Chemistry (Electron Transfer session)
The novel electronic properties (e.g., Coulomb blockade) of nanometer scale assemblies of metal nanoparticles make them potentially useful in nanoelectronic devices and extremely sensitive chemosensors. To date, no straightforward and reproducible methods are available for the fabrication of low-dimensional nanoparticle assemblies. Our method for nanofabrication of linear nanoparticle arrays involves the assembly of functionalized metal nanoparticles onto rigid biomolecular scaffolds cast upon an insulating substrate and bridged between narrowly spaced electrodes. Our previous investigations of unpatterned nanoparticle thin films provided clear evidence of Coulomb blockade at room temperature, but the response was unstable over time. In this paper we present a wet chemical approach to preparing one- and two-dimensional arrays of gold nanoparticles assembled onto a polypeptide (poly-L-lysine) scaffold layer. The assembly process provides a simple, chemical method to immobilize the particles and is found to stabilize the electrical response (Coulomb blockade) of the array compared with unpatterned samples.
To be presented in two different poster sessions:
(1) Division of Inorganic Chemistry Poster Session II: Organometallics, Ziegler-Natta, Catalysts, Materials, General
(2) Sci-Mix
Larger scale synthetic methods are needed if nanoparticles are to become important building blocks in the production of a wide range of technologically useful materials. We have developed a unique biphasic synthesis for triphenylphosphine stabilized gold nanoparticles that safely and easily produces gram quantities of nanoparticle material. Here we will present the synthetic scheme, characterization of the material, and comment on the implication of the synthesis on theories of nanoparticle formation and growth. Characterization of the nanoparticle products utilizes electron microscopy and powder X-ray diffraction for size analysis, with X-ray photoelectron spectroscopy and thermogravimetric analysis used to determine elemental composition. We will show the utility of this material in ligand exchange chemistry through the synthesis of thiol-stabilized derivatives for study in nanoelectronic materials.
To be presented in two different poster sessions:
- (1) Division of Colloid and Surface Chemistry: Session on Surfactants, Colloids, and Applications
- (2) Sci-Mix