Sustainable Polysulfides for Oil Spill Remediation: Repurposing Industrial Waste for Environmental Benefit

Crude oil and hydrocarbon fuel spills are a perennial threat to aquatic environments. Inexpensive and sustainable sorbents are needed to mitigate the ecological harm of this pollution. To address this need, this study features a low-density polysulfide polymer that was prepared by the direct reaction of sulfur and used cooking oils. Because both sulfur and cooking oils are hydrophobic, the polymer has an affinity for hydrocarbons such as crude oil and diesel fuel and can rapidly remove them from seawater. Through simple mechanical compression, the oil can be recovered and the polymer can be re-used in oil spill remediation. The polysulfide is unique because it is prepared entirely from re-purposed waste: sulfur is a by-product of the petroleum industry and used cooking oil can be used as a co-monomer. In this way, sulfur waste from the oil industry is used to make an effective sorbent for combatting pollution from that same sector

Transition voltage spectroscopy of porphyrin molecular wires.

Measurements are presented of the current-voltage (I-V) characteristics of individual thiol-tethered porphyrin molecules (isolated in an alkanethiol matrix) and of self-assembled monolayers. In both cases, it is found that I/V(2) displays a minimum at a characteristic "transition voltage" V(m). Repeated measurements of the transition voltage enable both its time development and statistical behavior to be determined. For isolated molecules, the transition voltage shows a multipeaked distribution of values, indicating the presence of a small number of distinct molecular/contact configurations, each having different transport characteristics. For self-assembled monolayers, in contrast, a single-peaked distribution was observed, which is consistent with parallel conduction through many molecules

Comparison of the conductance of three types of porphyrin-based molecular wires: β,meso,β-fused tapes, meso-Butadiyne-linked and twisted meso-meso linked oligomers.

The length dependence of charge transport is evaluated in three families of porphyrin-based wires. Planar edge-fused tapes and alkyne-linked oligomers mediate efficient charge transport with exceptionally shallow distance dependence, whereas the conductances of the twisted singly linked chains decrease steeply with increasing oligomer length. The planar tapes are more conjugated than the alkyne-linked oligomers, but these two types of wires have similar conductance attenuation factors

Conformation and packing of porphyrin polymer chains deposited using electrospray on a gold surface.

Molecular worms: Porphyrin polymers and oligomers are deposited on a Au(111) surface using electrospray deposition and are shown to adopt an arrangement where chains from neighboring molecules are interdigitated. Although the flexible nature of the polymers gives rise to sharp kinks and the crossing of polymer strands (see scheme), a longer correlation length as compared with solvated oligomers is observed. Copyright © 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

Single molecule conductance of porphyrin wires with ultralow attenuation.

A series of thioacetate-terminated butadiyne-linked porphyrin oligomers have been synthesized with one to three porphyrin repeat units. Single molecule electrical scanning tunneling microscopy measurements using the I(s) and I(t) methods were used to determine the molecule conductances for this series of oligomers. The molecular conductance shows an exponential falloff with sulfur-sulfur distance with a remarkably low attenuation factor of beta = (0.04 +/- 0.006) A-1