Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-02-02
2001-02-13
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S340000, C525S360000, C525S383000, C525S384000, C526S265000
Reexamination Certificate
active
06187871
ABSTRACT:
TECHNICAL FIELD
The present invention pertains to stable electron acceptor compositions which have efficient and sustained photoinduced charge separation states.
BACKGROUND OF THE INVENTION
Solar energy can be used and stored by the efficient production of long-lived photo-induced charge separation—a state achieved in photosynthetic systems by the formation of a long-lived radical pair. A number of artificial systems have been reported that efficiently undergo photochemical charge transfer, unfortunately, the thermal back electron transfer often proceeds at an appreciable rate, limiting the utility of these systems. What is needed is a systems which has very efficient photoinduced charge transfer, and forms a charge-separated state which is long lived in air. The charge separation in these systems typically involves a redox reaction between a photo excited donor and a suitable acceptor, resulting in the production of radical ion pairs illustrated by the formula:
D+hv→D* (1a)
D*+A→A
−
+D
+
(1b)
D
+
+A
−
→D+A (2)
The cation and anion generated in this way are better oxidants and reductants, respectively, than either of the neutral ground-state molecules. To harvest the light put into this system, the oxidizing and reducing power of the photo-generated species must be used before the electrons are transferred back (equation 2) generating the starting materials. It is desirable to control this photochemically unproductive thermal fast back electron transfer reaction. One method has been to incorporate the donors and acceptors into solid matrices.
The individual components in the charge separated state have the appropriate potentials to carry out the reduction and oxidation of water. Unfortunately, these direct reactions are kinetically limited, such that catalysts are required to overcome the kinetic barriers. Colloidal platinum particles are ideal catalysts for the reduction of water to give H
2
. In systems used for photoreduction of water, the close contact of high potential radicals formed in the compounds and Pt particles is advantageous, because electron transfer from reduced viologen to Pt particles should compete effectively with back electron transfer. These platinum particles may be present in the reaction solution, incorporated into the structure of the compositions, or both.
Compounds which can carry out reduction reactions, using hydrogen gas as their reducing equivalents, are useful as catalysts for the conversion of mixtures of hydrogen and oxygen to hydrogen peroxide. Hydrogen peroxide is a very large volume chemical. The United States annual production is greater than 500 million lbs. Several processes have been patented for the production of hydrogen peroxide, which depend on the two following reactions. The goal is to promote reaction (3) and retard reaction (4):
H
2
+O
2
→H
2
O
2
(3)
H
2
O
2
+H
2
→2H
2
O (4)
A number of catalysts for this conversion have been reported including both homogeneous and heterogeneous catalysts.
The compositions of the present invention are capable of producing a sustained photoinduced charge separation state which renders the compositions useful in solar energy conversion and storage. In addition, the compositions permit reduction of various metal ions to produce the zero-valence metal in colloidal form entrapped in the matrices of the compositions. These latter matrices containing the zero-valence metal have a variety of uses such as in the decomposition of water to yield hydrogen gas and the sensing of oxygen. In addition, the zero-valence metal matrices can be used in catalysis, as for example in the production of hydrogen peroxide and the oligomerization of methane to form higher hydrocarbons.
SUMMARY OF THE INVENTION
The present invention provides multi-layered compositions having a plurality of parallel “pillars” comprising divalent electron acceptor moieties with a phosphonate or arsenate at each end. Each layer of parallel pillars is separated by a layer of a group (IVA), (IVB), (IIIA) or (IIIB) metal or a lanthanide.
The complex can further comprise particles of at least one Group VIII metal at zero valence entrapped within each layer of the complex. The complexes can also incorporate “stalactites” and “stalagmites” of capped arsonato or phosphonato ligands interspersed with the pillars providing a series of interstices about each electron accepting group.
The complexes are useful for the conversion and storage of solar energy and as catalysts for reduction reactions, for example, the production of hydrogen peroxide from oxygen and hydrogen gases, the production of H
2
gas from water, and the reduction of ketones to form alcohols.
REFERENCES:
patent: 3380928 (1968-04-01), Hughes et al.
patent: 3501447 (1970-03-01), Pieper et al.
patent: 5344891 (1994-09-01), Kawabata et al.
patent: 5573882 (1996-11-01), Larson et al.
Tang Xiaozhang
Thompson Mark E.
Lipman Bernard
Nissim Stuart H.
The Trustees of Princeton University
Woodbridge Richard C.
Woodbridge & Associates P.C.
LandOfFree
Electron acceptor compositions on polymer templates does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electron acceptor compositions on polymer templates, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electron acceptor compositions on polymer templates will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2594593