title: Aerosolized droplet mediated self-assembly of photosynthetic pigment analogues and deposition onto substrates.
abstract: Self-assembled photosynthetic molecules have a high extinction coefficient and a broad absorption in the infrared region, and these properties can be used to improve the efficiency of solar cells. We have developed a single-step method for the self-assembly of synthetic chlorin molecules (analogues of native bacteriochlorophylls) in aerosolized droplets, containing a single solvent and two solvents, to synthesize biomimetic light-harvesting structures. In the single-solvent approach, assembly is promoted by a concentration-driven process due to evaporation of the solvent. The peak absorbance of Zn(II) 3-(1-hydroxyethyl)-10-phenyl-13(1)-oxophorbine (1) in methanol shifted from 646 nm to 725 nm (∼ 80 nm shift) after assembly, which is comparable to the shift observed in the naturally occurring assembly of bacteriochlorophyll c. Although assembly is thermodynamically favorable, the kinetics of self-assembly play an important role, and this was demonstrated by varying the initial concentration of the pigment monomer. To overcome kinetic limitations, a two-solvent approach using a volatile solvent (tetrahydrofuran) in which the dye is soluble and a less volatile solvent (ethanol) in which the dye is sparingly soluble was demonstrated to be effective. The effect of molecular structure is demonstrated by spraying the sterically hindered Zn(II) 3-(1-hydroxyethyl)-10-mesityl-13(1)-oxophorbine (2), which is an analogue of 1, under similar conditions. The results illustrate a valuable and facile aerosol-based method for the formation of films of supramolecular assemblies.
authors.affiliation: Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Vivek B
authors.initials: VB
authors.lastname: Shah
authors.forename: Pratim
authors.initials: P
authors.lastname: Biswas
mesh_terms: D000336:Aerosols; D010788:Photosynthesis; D010860:Pigments, Biological / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry
chemical_list: D000336:Aerosols; D010860:Pigments, Biological; D012997:Solvents