Near unity quantum yield of light-driven redox mediator reduction and efficient H2 generation using colloidal nanorod heterostructures.

The advancement of direct solar-to-fuel conversion technologies requires the development of efficient catalysts as well as efficient materials and novel approaches for light harvesting and charge separation. We report a novel system for unprecedentedly efficient (with near-unity quantum yield) light-driven reduction of methylviologen (MV(2+)), a common redox mediator, using colloidal quasi-type II CdSe/CdS dot-in-rod nanorods as a light absorber and charge separator and mercaptopropionic acid as a sacrificial electron donor. In the presence of Pt nanoparticles, this system can efficiently convert sunlight into H(2), providing a versatile redox mediator-based approach for solar-to-fuel conversion. Compared to related CdSe seed and CdSe/CdS core/shell quantum dots and CdS nanorods, the quantum yields are significantly higher in the CdSe/CdS dot-in-rod structures. Comparison of charge separation, recombination and hole filling rates in these complexes showed that the dot-in-rod structure enables ultrafast electron transfer to methylviologen, fast hole removal by sacrificial electron donor and slow charge recombination, leading to the high quantum yield for MV(2+) photoreduction. Our finding demonstrates that by controlling the composition, size and shape of quantum-confined nanoheterostructures, the electron and hole wave functions can be tailored to produce efficient light harvesting and charge separation materials.

[1]  U. Banin,et al.  Multiexciton engineering in seeded core/shell nanorods: transfer from type-I to quasi-type-II regimes. , 2009, Nano letters.

[2]  M. Hoffman,et al.  Quantum yield of formation of methylviologen radical cation in the photolysis of the Ru(bpy)32+/methylviologen/EDTA system , 1984 .

[3]  J. Wachtveitl,et al.  Ultrafast charge separation in multiexcited CdSe quantum dots mediated by adsorbed electron acceptors. , 2009, Journal of the American Chemical Society.

[4]  T. Lian,et al.  Wave function engineering for efficient extraction of up to nineteen electrons from one CdSe/CdS quasi-type II quantum dot. , 2012, Journal of the American Chemical Society.

[5]  A Paul Alivisatos,et al.  Air-Stable All-Inorganic Nanocrystal Solar Cells Processed from Solution , 2005, Science.

[6]  N. Lewis,et al.  Powering the planet: Chemical challenges in solar energy utilization , 2006, Proceedings of the National Academy of Sciences.

[7]  K. Honda,et al.  Measurement of the extinction coefficient of the methyl viologen cation radical and the efficiency of its formation by semiconductor photocatalysis , 1982 .

[8]  Liberato Manna,et al.  Synthesis, properties and perspectives of hybrid nanocrystal structures. , 2006, Chemical Society reviews.

[9]  A. Alivisatos,et al.  Structural and electronic study of an amorphous MoS3 hydrogen-generation catalyst on a quantum-controlled photosensitizer. , 2011, Angewandte Chemie.

[10]  T. Lian,et al.  Light-Driven, Quantum Dot-Mediated Regeneration of FMN To Drive Reduction of Ketoisophorone by Old Yellow Enzyme , 2012 .

[11]  Xiaogang Peng,et al.  Size-dependent dissociation pH of thiolate ligands from cadmium chalcogenide nanocrystals. , 2005, Journal of the American Chemical Society.

[12]  C. Larabell,et al.  Quantum dots as cellular probes. , 2005, Annual review of biomedical engineering.

[13]  P. Kamat,et al.  Photocatalytic events of CdSe quantum dots in confined media. Electrodic behavior of coupled platinum nanoparticles. , 2010, ACS nano.

[14]  A. Harriman,et al.  Metal phthalocyanines and porphyrins as photosensitizers for reduction of water to hydrogen , 1982 .

[15]  E. Weiss,et al.  Simultaneous determination of the adsorption constant and the photoinduced electron transfer rate for a CdS quantum dot-viologen complex. , 2011, Journal of the American Chemical Society.

[16]  J. Moser,et al.  Multielectron storage and hydrogen generation with colloidal semiconductors. , 1983, Proceedings of the National Academy of Sciences of the United States of America.

[17]  Bruce A. Parkinson,et al.  Photoelectrochemical pumping of enzymatic CO2 reduction , 1984, Nature.

[18]  Peter Lindblad,et al.  Biomimetic and microbial approaches to solar fuel generation. , 2009, Accounts of chemical research.

[19]  M. Grätzel,et al.  Hydrogen evolution from water induced by visible light mediated by redox catalysis , 1979, Nature.

[20]  Kuppuswamy Kalyanasundaram,et al.  Photophysics, photochemistry and solar energy conversion with tris(bipyridyl)ruthenium(II) and its analogues , 1982 .

[21]  T. Lian,et al.  Wave function engineering for ultrafast charge separation and slow charge recombination in type II core/shell quantum dots. , 2011, Journal of the American Chemical Society.

[22]  M. Graetzel,et al.  Projection, size factors, and reaction dynamics of colloidal redox catalysts mediating light induced hydrogen evolution from water , 1979 .

[23]  Dewey Holten,et al.  Probing electronic communication in covalently linked multiporphyrin arrays. A guide to the rational design of molecular photonic devices. , 2002, Accounts of chemical research.

[24]  I. Willner,et al.  Characterization of palladium-.beta.-cyclodextrin colloids as catalysts in the photosensitized reduction of bicarbonate to formate , 1989 .

[25]  Itamar Willner,et al.  Electron-Transfer Communication in Glutathione Reductase Assemblies: Electrocatalytic, Photocatalytic, and Catalytic Systems for the Reduction of Oxidized Glutathione , 1994 .

[26]  J. Luther,et al.  Semiconductor quantum dots and quantum dot arrays and applications of multiple exciton generation to third-generation photovoltaic solar cells. , 2010, Chemical reviews.

[27]  A. Lever,et al.  Ruthenium(II) tris(bipyrazyl) dication: a new photocatalyst , 1980 .

[28]  A. Harriman,et al.  Photosensitised reduction of water to hydrogen using water-soluble zinc porphyrins , 1981 .

[29]  G. Rainò,et al.  Probing the wave function delocalization in CdSe/CdS dot-in-rod nanocrystals by time- and temperature-resolved spectroscopy. , 2011, ACS nano.

[30]  Monica Nadasan,et al.  Synthesis and micrometer-scale assembly of colloidal CdSe/CdS nanorods prepared by a seeded growth approach. , 2007, Nano letters.

[31]  Albert D. Dukes,et al.  Band Edge Recombination in CdSe, CdS and CdSxSe1−x Alloy Nanocrystals Observed by Ultrafast Fluorescence Upconversion: The Effect of Surface Trap States , 2008 .

[32]  Xiaogang Peng,et al.  Experimental Determination of the Extinction Coefficient of CdTe, CdSe, and CdS Nanocrystals , 2003 .

[33]  J. Schneider,et al.  Photocatalytic generation of hydrogen from water using a platinum(II) terpyridyl acetylide chromophore. , 2006, Journal of the American Chemical Society.

[34]  S. Sakaki,et al.  Methylviologen-pendant iron porphyrins as models of a reduction enzyme: six-electron reduction of nitrobenzene to anilineElectronic supplementary information (ESI) available: time-courses of reduction, UV-VIS spectral changes, cyclic voltammograms, EPR spectra, conversion and yield percentages for t , 2003 .

[35]  J. Storhoff,et al.  A DNA-based method for rationally assembling nanoparticles into macroscopic materials , 1996, Nature.

[36]  M. Kovalenko,et al.  Prospects of colloidal nanocrystals for electronic and optoelectronic applications. , 2010, Chemical reviews.

[37]  H. Gest,et al.  A NEW PROCEDURE FOR ASSAY OF BACTERIAL HYDROGENASES , 1956, Journal of bacteriology.

[38]  Kurz,et al.  Ultrafast carrier dynamics in semiconductor quantum dots. , 1996, Physical review. B, Condensed matter.

[39]  T. Ebbesen.  Interference of hydrogen with the electron transfer to colloidal platinum catalyst and consequences for photochemical water reduction , 1984 .

[40]  A. Paul Alivisatos,et al.  Photocatalytic Hydrogen Production with Tunable Nanorod Heterostructures , 2010 .

[41]  M. Grätzel,et al.  Hydrogen Evolution from Water by Visible Light, a Homogeneous Three Component Test System for Redox Catalysis , 1978 .

[42]  M. Graetzel,et al.  Ultrafine and specific catalysts affording efficient hydrogen evolution from water under visible light illumination , 1981 .

[43]  Lin-wang Wang,et al.  Electronic structures of the CdSe/CdS core-shell nanorods. , 2010, ACS nano.

[44]  Prashant V Kamat,et al.  Beyond photovoltaics: semiconductor nanoarchitectures for liquid-junction solar cells. , 2010, Chemical reviews.

[45]  I. Willner,et al.  Electron-transfer communication between a redox polymer matrix and an immobilized enzyme: activity of nitrate reductase in a viologen-acrylamide copolymer , 1990 .

[46]  A. Harriman,et al.  Viologen/platinum systems for hydrogen generation , 1982 .

[47]  P. Vignais,et al.  Occurrence, classification, and biological function of hydrogenases: an overview. , 2007, Chemical reviews.

[48]  F. García-Santamaría,et al.  Suppressed auger recombination in "giant" nanocrystals boosts optical gain performance. , 2009, Nano letters.

[49]  M. Takeuchi,et al.  Photochemical Evolution of H2 in the System Methyl Viologen/MnII-meso-Tetraphenylporphyrintrisulfonic Acid/Mercaptoethanol/Hydrogenase† , 1982 .

[50]  M. Grätzel,et al.  A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films , 1991, Nature.

[51]  T. Lian,et al.  Controlling charge separation and recombination rates in CdSe/ZnS type I core-shell quantum dots by shell thicknesses. , 2010, Journal of the American Chemical Society.

[52]  T. Moore,et al.  Mimicking photosynthetic solar energy transduction. , 2001, Accounts of chemical research.

[53]  M. Bruchez,et al.  Immunofluorescent labeling of cancer marker Her2 and other cellular targets with semiconductor quantum dots , 2003, Nature Biotechnology.