Conventional bioethanol for transportation fuel typically consumes agricultural feedstocks also suitable for human consumption and requires large amounts of energy for conversion of feedstock to fuel. Alternative feedstocks, optimally those not also in demand for human consumption, and off-grid energy sources for processing would both contribute to making bioethanol far more sustainable than current practices. Cellulosic bioethanol production involves three steps: the extraction of sugars from cellulosic feedstock, the fermentation of sugars to produce ethanol, and the purification of ethanol through distillation. Traditional production methods for extraction and distillation are energy intensive and therefore costly, limiting the advancement of this approach. Here we report an initial demonstration of the conversion of cellulosic feedstock into ethanol by completely off-grid solar processing steps. Our approach is based on nanoparticle-enabled solar steam generation, in which high-efficiency steam can be produced by illuminating light-absorbing nanoparticles dispersed in H 2 O with sunlight. We used solar-generated steam to successfully hydrolyze feedstock into sugars; we then used solar steamdistillation to purify ethanol in the final processing step. Coastal hay, a grass grown for livestock feed across the southern United States, and sugar cane as a control are successfully converted to ethanol in this proof-of-concept study. This entirely off-grid solar production method has the potential to realize the long-dreamed-of goal of sustainable cellulosic bioethanol production.

The optical properties of plasmonic nanoparticles in the size range corresponding to the electrostatic, or dipole, limit have the potential to reveal effects otherwise masked by phase retardation. Here we examine the optical properties of individual, sub-50 nm hollow Au nanoshells (Co-HGNS), where Co is the initial sacrificial core nanoparticle, using single particle total internal reflection scattering (TIRS) spectroscopy. The residual Co present in the metallic shell induces a substantial broadening of the homogeneous plasmon resonance line width of the Co-HGNS, where the full width at half-maximum (fwhm) broadens proportionately with increasing Co content. This doping-induced line broadening provides a strategy for controlling plasmon line width independent of nanoparticle size, and has the potential to substantially modify the relative decay channels for localized nanoparticle surface plasmons.3