Source: https://patents.justia.com/patent/9149836
Timestamp: 2019-08-22 22:51:30
Document Index: 6992317

Matched Legal Cases: ['Application No. 201010503565', 'Application No. 201010503565', 'Application No. 94117823', 'Application No. 10', 'Application No. 94117823', 'Application No. 10', 'Application No. 10', 'Application No. 2007', 'Application No. 2007', 'Application No. 2007', 'Application No. 2007', 'Application No. 201010503565', 'Application No. 201010503565', 'Application No. 200580018708', 'Application No. 200580018708', 'Application No. 200580018708', 'Application No. 2', 'Application No. 2005254490', 'Application No. 2005254490', 'Application No. 2005254490', 'Application No. 2005254490', 'Application No. 201010503565', 'Application No. 201010503565', 'Application No. 200580018708', 'Application No. 201010503565', 'Application No. 10', 'Application No. 10', 'Application No. 102120175', 'Application No. 2012103445192', 'Application No. 2012103445192']

US Patent for Compositions and methods for modulation of nanostructure energy levels Patent (Patent # 9,149,836 issued October 6, 2015) - Justia Patents Search
Justia Patents Particulate Matter (e.g., Sphere, Flake, Etc.)US Patent for Compositions and methods for modulation of nanostructure energy levels Patent (Patent # 9,149,836)
Sep 4, 2013 - SanDisk Corporation
Ligand compositions for use in preparing discrete coated nanostructures are provided, as well as the coated nanostructures themselves and devices incorporating same. Methods for post-deposition shell formation on a nanostructure, for reversibly modifying nanostructures, and for manipulating the electronic properties of nanostructures are also provided. The ligands and coated nanostructures of the present invention are particularly useful for close packed nanostructure compositions, which can have improved quantum confinement and/or reduced cross-talk between nanostructures. Ligands of the present invention are also useful for manipulating the electronic properties of nanostructure compositions (e.g., by modulating energy levels, creating internal bias fields, reducing charge transfer or leakage, etc.).
This application is a divisional of U.S. patent application Ser. No. 11/299,299 filed Dec. 9, 2005, which claims priority to and benefit of U.S. Provisional Patent Application Ser. No. 60/635,799, filed Dec. 13, 2004, and is a continuation-in-part of U.S. patent application Ser. No. 11/147,670, filed Jun. 7, 2005, which claims priority to and benefit of the following prior provisional patent applications: U.S. Provisional Patent Application Ser. No. 60/578,236, filed Jun. 8, 2004, U.S. Provisional Patent Application Ser. No. 60/632,570, filed Nov. 30, 2004, each of which is incorporated herein by reference in its entirety for all purposes.
The present invention is in the field of nanotechnology. More particularly, the invention is directed to ligand compositions for use in manipulating the electronic properties of nanostructure compositions (e.g., by modulating energy levels, creating internal bias fields, reducing charge transfer or leakage, etc.), as well as related methods and devices involving the ligand compositions.
Of the synthetic approaches available for preparing nanostructures, top-down patterned approaches such as chemical vapor deposition (CVD) or molecular beam epitaxy (MBE) are commonly used to generate core and core:shell nanostructures. These methods typically yield large and/or disordered and/or low density packing nanoparticles, and require high cost (high temperature, high vacuum) processing steps. Solution based syntheses can also be used to synthesize semiconductor nanocrystals (either cores or core/shells) which are more readily compatible with solution based deposition methods such as spin coating or other evaporation methods. For example, nanostructures comprising CdSe cores (or crystalline cores) with a shell of ZnS can be prepared by solution deposition techniques (see, e.g., Murray et al. “Synthesis and characterization of nearly monodisperse CdE (E=S, Se, Te) semiconductor nanocrystals” J. Am. Chem. Soc. 115: 8706-8715 (1993)). However, nanostructures generated by these and other standard core-shell synthetic techniques typically do not have a thick enough shell to confine a charge in the core to enough degree to prevent charge diffusion to other nanostructures placed within a few nanometers of the first nanostructure.
Accordingly, there exists a need in the art for discrete coated nanostructures that can be easily integrated into various manufacturing processes without further processing. Preferably, the coated nanostructures can be closely packed while maintaining greater quantum confinement than standard CdSe/ZnS core:shell structures.
In addition, the energy levels (electron affinity) of component semiconductor materials are an important consideration for fabrication of semiconductor-containing devices, such as photovoltaic devices, memory storage devices, transistors, and light-emitting and/or light-detecting devices, such as LEDs, phosphors, photo-detectors, and the like. Bulk semi-conductors have inherent valence and conduction bands associated with the specifics of the atomic composition. However, nanocrystals constructed of the same material(s) are thought to differ in energy levels compared to their bulk counterparts, due at least in part to the effects of quantum confinement; the energy levels can also be tuned for a given material, e.g., by variation of the nanocrystal size. Matching appropriate materials and energy level alignment is considered important for optimal device performance. Accordingly, there exists a need in the art for techniques that can be used to match appropriate materials and energy levels.
The present invention meets these and other needs by providing discrete coated nanostructures, ligands for coating discrete nanostructures, devices incorporating the coated nanostructures, and methods for preparing the coated nanostructures. A complete understanding of the invention will be obtained upon review of the following.
The present invention relates to the manipulation of the electronic properties of a nanostructure composition through the use of an associated ligand, preferably a dipole-containing ligand. In one aspect the invention provides methods for modulating an energy level of a nanostructure in the absence of a polymeric matrix. The methods include the steps of a) providing a nanostructure having a first energy level; b) selecting a ligand composition comprising a dipole, wherein the ligand composition has a second energy level as compared to the first energy level of the nanostructure; and c) associating or coupling the ligand composition to a surface of the nanostructure, thereby modulating the energy level of the nanostructure.
In certain embodiments, the first energy level of the nanostructure and the second energy level of the ligand composition are aligned (e.g., there is no change in the band gap upon association of the ligand with the nanostructure). In an alternate embodiment, the nanostructure and ligand composition have differing energy levels. For example, for ligand compositions in which the dipole comprises an electron donating group, coupling of the ligand to the nanostructure increases the level of the highest occupied molecular orbital (HOMO). The electron donating group can comprise, for example, a conjugated aromatic phosphonic acid ligand. Alternately, for ligand compositions in which the dipole comprises an electron withdrawing moiety, the ligand composition can decrease the HOMO level. The electron withdrawing group can comprise, for example, one or more boron atoms or one or more fluorine atoms. Exemplary ligand compositions include, but are not limited to, butyl boronic acid, 4-trimethylsilylphenyl boronic acid, a carborane, a boron derivative of a polyhedral oligomeric silsesquioxane (POSS), trifluoroacetic acid, a SiF derivative, an ammonium carboxylate-modified phosphonic acid, or a spiropyran salt.
The nanostructures employed in the invention can be prepared from any of a number of materials, including semiconducting materials. Exemplary semiconducting nanostructures include, but are not limited to, nanostructures prepared using a first element selected from group II of the periodic table and a second element selected from group VI, as well as those fabricated using a first element selected from group III of the periodic table and a second element selected from group V, and nanostructures prepared using an element selected from group IV. Associating the ligand composition with the surface of the nanostructure optionally comprises performing a ligand exchange or growing the nanostructure in the presence of the ligand composition.
In a related aspect, the invention provides methods for creating an internal bias field, e.g., for extraction of electrons or holes from a nanostructure composition. The methods of the invention include the steps of a) coupling a photoactivatable composition to a surface of a nanostructure, which composition forms a dipole upon activation, and b) activating the composition (e.g., by exposing the coupled ligand:nanostructure composition to a light source) and creating the dipole, thereby forming an internal bias field. Exemplary photoactivatable compositions for use as ligands in the invention include, but are not limited to, light-activated intramolecular salts such as spiropyrans. Coupling the photoactivatable composition to the surface of the nanostructure optionally comprises performing a ligand exchange. Optionally, these methods further include the step of extracting holes or electrons from the nanostructure, e.g., by transporting the electrons or holes toward an electrode. In certain embodiments, the nanostructure is a component of a photovoltaic cell.
In a further aspect, the invention provides methods for reducing charge diffusion among a plurality of nanostructures, such as quantum dots. The methods include the steps of a) coupling a ligand composition comprising an electron withdrawing group to a surface of a member nanostructure (e.g., quantum dot), and b) forming a dipole on the surface of the member nanostructure and increasing the electron affinity of the nanostructure, thereby reducing charge diffusion among the nanostructures. Ligand compositions having electron withdrawing characteristics that can be used in the methods include, but are not limited to, fluorine-containing compositions (e.g., F−SiF and derivatives, fluorine polymers such as polytetrafluoroethylene, etc.), boron-containing compositions (e.g., aryl-boron oligomers and boronic acid compositions), light-activated intramolecular salts such as spiropyrans, and silicon oxide cage complexes such as silsesquioxanes. Preferably, the ligand composition includes a phosphonic acid moiety or other nanostructure binding moiety. The methods are particularly useful in the preparation and use of nanostructures, particularly quantum dots, for use in media utilized for discrete quantized photon (or charge) generation and/or transfer.
The invention also provides ligand compositions for modulating nanostructure energy levels. In one class of embodiments, ligand compositions of the invention include a nonconjugated body structure having a dipole moiety, and a nanostructure binding moiety coupled to the nonconjugated body structure at a first position. Optionally, the nonconjugated body structure includes a second dipole coupled at a second position. Exemplary nonconjugated body structures for use in the ligand compositions include, but are not limited to, fluorine-containing compositions such as those noted above, carboranes and other boron-containing compositions, and light activated intramolecular salts. Exemplary nanostructure binding moieties include, but are not limited to, phosphonic acid, carboxylic acid, amine, phosphine, and thiol moieties.
In another class of embodiments, ligand compositions for modulating nanostructure energy levels have a body structure comprising a light-activated spiropyran salt and a nanostructure binding moiety coupled to the body structure at a first position. Exemplary nanostructure binding moieties include, but are not limited to, phosphonic acid, carboxylic acid, amine, phosphine, and thiol moieties.
In a further class of embodiments, ligand compositions for modulating nanostructure energy levels comprise a body structure comprising a boron-containing oligomer and a nanostructure binding moiety coupled to the body structure at a first position. The boron-containing oligomers optionally are an (AB)n composition, wherein A is an aryl (or other conjugated) moiety and B is a boron atom. In some embodiments, the boron atoms are positioned para to one another, while in other embodiments, the positioning is meta.
In yet another class of embodiments, ligand compositions for modulating nanostructure energy levels comprise a body structure comprising a thiophene moiety and a nanostructure binding moiety coupled to the body structure at a first position. The composition optionally includes a boron atom, e.g., as part of the nanostructure binding moiety (e.g., as part of a boronic acid group).
Nanostructure compositions (e.g., nonpolymeric compositions) comprising a plurality of nanostructures having coupled thereto a plurality of a selected ligand composition are also a feature of the invention, as are devices including such nanostructure compositions.
Before describing the present invention in detail, it is to be understood that this invention is not limited to particular devices or systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used in this specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to “a nanostructure” includes a combination of two or more nanostructures; reference to “a ligand composition” includes mixtures of ligands; reference to “a substituent” includes mixtures of substituents, and the like.
The terms “crystalline” or “substantially crystalline,” when used with respect to nanostructures, refer to the fact that the nanostructures typically exhibit long-range ordering across one or more dimensions of the structure. It will be understood by one of skill in the art that the term “long range ordering” will depend on the absolute size of the specific nanostructures, as ordering for a single crystal cannot extend beyond the boundaries of the crystal. In this case, “long-range ordering” will mean substantial order across at least the majority of the dimension of the nanostructure. In some instances, a nanostructure can bear an oxide or other coating, or can be comprised of a core and at least one shell. In such instances it will be appreciated that the oxide, shell(s), or other coating need not exhibit such ordering (e.g., it can be amorphous, polycrystalline, or otherwise). In such instances, the phrase “crystalline,” “substantially crystalline,” “substantially monocrystalline,” or “monocrystalline” refers to the central core of the nanostructure (excluding the coating layers or shells). The terms “crystalline” or “substantially crystalline” as used herein are intended to also encompass structures comprising various defects, stacking faults, atomic substitutions, and the like, as long as the structure exhibits substantial long range ordering (e.g., order over at least about 80% of the length of at least one axis of the nanostructure or its core). In addition, it will be appreciated that the interface between a core and the outside of a nanostructure or between a core and an adjacent shell or between a shell and a second adjacent shell may contain non-crystalline regions and may even be amorphous. This does not prevent the nanostructure from being crystalline or substantially crystalline as defined herein.
The term “monocrystalline” when used with respect to a nanostructure indicates that the nanostructure is substantially crystalline and comprises substantially a single crystal. Then used with respect to a nanostructure heterostructure comprising a core and one or more shells, “monocrystalline” indicates that the core is substantially crystalline and comprises substantially a single crystal.
A “nanoparticle” is any nanostructure having an aspect ratio less than about 1.5. Nanoparticles can be of any shape, and include, for example, nanocrystals, substantially spherical particles (having an aspect ratio of about 0.9 to about 1.2), and irregularly shaped particles. Nanoparticles can be amorphous, crystalline, partially crystalline, polycrystalline, or otherwise. Nanoparticles can be substantially homogeneous in material properties, or in certain embodiments can be heterogeneous (e.g., heterostructures). The nanoparticles can be fabricated from essentially any convenient material or materials.
FIGS. 5A-5I provide exemplary first coating compositions of the present invention.
FIG. 7 depicts a chemical synthesis scheme for one embodiment of a boron-containing ligand composition of the present invention.
FIG. 8 depicts alternative reaction parameters optionally used in the final synthesis step of a boron-containing ligand composition.
Cross-talk between dots (i.e., signal interference due to electronic interactions between the nanostructures) leads to poor device performance. The present invention, however, provides compositions, methods and devices in which nanostructured charge storage elements are able to be closely packed (e.g., at densities of 1×1010/cm2 or greater, even at a high density, e.g., at 1×1012/cm2 or greater), while preserving or improving quantum confinement, either by controlling the distance between the nanostructures and/or by introducing an insulating or dielectric coating material such as silicon dioxide around discrete nanostructures.
The coatings employed in the compositions of the present invention typically exhibit a first property in their initial (i.e., pre-conversion or pre-cured) state, and a second, differing property in the second, post-conversion or post-curing state. For examples involving coatings having differing electrical properties upon conversion or curing, the first electrical property could include conductivity while the second electric property is nonconductivity (or vice versa). Likewise, the material in the first state may be an electron conductor or a neutral material, while the material in the second state may be a hole conductor. Alternatively, for embodiments relating to optical properties, the first and second optical properties could be opacity and transparency, e.g., to visible light. Alternatively, the first optical property could include light absorption (or transmission or emission) at a first wavelength, while the second optical property comprises light absorption (or transmission or emission) at a second wavelength. Alternatively, for embodiments relating to structural properties, the material in the first state could be a flexible molecule, while the second state could comprise a rigid (porous or solid) shell. In one class of embodiments, the first physical property comprises solubility, e.g., in a selected solvent, while the second electrical property comprises nonconductivity. Conversion of the coating can be accomplished, e.g., by application of heat and/or radiation.
The methods of the present invention include the step of converting or curing the ligand composition to generate a second coating (e.g., in some embodiments, a rigid and/or insulating shell) on the first surface of the ligand-exchanged nanostructure. In a preferred embodiment, the curing step is performed by heating the nanostructure having the ligand composition associated therewith at temperatures that will not degrade or otherwise compromise the nanostructure. For the nanostructure-containing compositions of the present invention, curing is typically achieved at temperatures less than about 500° C. In some embodiments, the heating process is performed between 200-350° C. The curing process results in the formation of the second coating or shell (e.g., a thin, solid matrix on the first surface of the nanostructure). The shell can comprise, for example, an electrically conductive composition, an electrically insulating composition, an optically transparent composition, an optically opaque composition, or even a combination of these features. In a preferred embodiment, the second coating is a rigid insulating shell comprising a glass or glass-like composition, such as SiO2. The curing step is optionally performed by heating the nanostructure in an oxidizing atmosphere.
Other aspects of the present invention provide ligand compositions for use in manipulating the electronic properties of nanostructures, for example, by modulating energy levels, creating internal bias fields, or reducing charge transfer or leakage. Such ligand compositions are optionally, but need not be, convertible coatings such as those noted above. Methods and devices related to the ligand compositions for modulating nanostructure energy levels are also described, as are nanostructures associated with the ligands.
In a preferred embodiment, the plurality of coated nanostructures function as charge storage elements in various high-density data storage applications. Two key requirements for the use of the plurality of coated nanostructures in these applications are the selection of appropriate surface properties, and close packing of the nanostructures in monolayer arrays, optionally well-ordered monolayer arrays. As shown by Bulović and coworkers (Coe et al. “Electroluminescence from single monolayers of nanocrystals in molecular organic devices” Nature 420:800-803 (2002)), hexagonally-packed monolayers of CdSe-type semiconducting nanocrystals can be prepared by taking advantage of phase segregation between aliphatic surfactants on the nanocrystals and aromatic conjugated organic materials deposited on the nanocrystal via spin-coating. However, a composition of nanocrystals embedded into (or on top of) a 40 nm thick organic matrix is not desirable in memory device fabrication processes. Among other issues, the thickness of the (fairly-conductive) organic matrix will not provide enough quantum confinement, and will reduce the read/write efficacy and predictability of the device. Furthermore, the organic layer(s) are not compatible with typical memory fabrication techniques. To this end, coated nanostructures which are more compatible with charge storage applications are provided by the present invention. In a specific preferred embodiment, the plurality of coated nanostructures of the present invention comprise one or more monolayers of nanodots having silsesquioxane or silicate ligand surface ligands. These can be prepared, for example, by various self-assembly methods as described herein; after curing, the resulting nanostructures are insulated by the second coating of silicon dioxide-containing ligands. Among other advantages, the oxide second coating reduces cross-talk between nanostructures.
The ligands employed as first coatings in the compositions, devices and methods of the present invention are prepared as a means by which to generate a second coating having a selected or desired property (or properties). The second coating provides an altered electrical, optical, physical or structural state as compared to the first coating, such as changes in rigidity, solubility, and/or in optical properties (refractive index, emission and/or absorption properties). A variety of coating compositions are considered for use in the present invention. For example, the coating can be an organic composition, such as various polymeric precursors that may be chemically or radiatively converted to altered (second) coating compositions, e.g., through cross-linking, further polymerization, etc. Exemplary organic compositions include, but are not limited to, dendrimer PAMAM (amine dendrimer), amine-(or other nanocrystal binding head group) terminated methyl methacrylate (polymethylmethacrylate precursor), phosphonate head group-containing polymers, carboxylic acid-terminated diene or diacetylene compositions, any heteroatom containing monomer(s) that can be converted to polymers upon chemical, heat or light activation, as well as the ligands described in by Whiteford et al. U.S. patent application Ser. No. 10/656,910, filed Sep. 4, 2003.
Alternatively, the coating is an inorganic composition. Optionally, the coating includes a silicon or silicon oxide moiety. It will be understood by one of skill in the art that the term “silicon oxide” as used herein can be understood to refer to silicon at any level of oxidation. Thus, the term silicon oxide can refer to the chemical structure SiOx, wherein x is between 1 and 2 inclusive. Inorganic coatings for use in the present invention include, but are not limited to, tin oxide, vanadium oxide, manganese oxide, titanium oxide, zirconium oxide, tungsten oxide, and niobium oxide, silicon carbide, silicon nitride, as well as other silicon-containing coatings and/or boron-containing coatings. In some preferred embodiments, the coating comprises a hybrid organic/inorganic composition, such as some embodiments of the silicon oxide cage complexes provided herein. See also the compositions provided in Schubert “Polymers Reinforced by Covalently Bonded Inorganic Clusters” Chem. Mater. 13:3487-3494 (2001); Feher and Walzer “Synthesis and characterization of vanadium-containing silsesquioxanes” Inorg. Chem. 30:1689-1694 (1991); Coronado and Gomez-Garcia “Polyoxometalate-Based Molecular Materials” Chem. Rev. 98:273-296 (1998); Katsoulis “A Survey of Applications of Polyoxometalates” Chem. Rev. 98:359-387 (1998); Muller et al. “Polyoxometalates Very Large Clusters—Nanoscale Magnets” Chem. Rev. 98:239-271 (1998); Rhule et al. “Polyoxometalates in Medicine” Chem. Rev. 98:327-357 (1998); Weinstock “Homogeneous-Phase Electron-Transfer Reactions of Polyoxometalates” Chem. Rev. 98:113-170 (1998); Suzuki “Recent Advanced in the Cross-Coupling Reactions of Organoboron Derivatives with Organic Electrophiles 1995-1998” J. Organomet. Chem. 576:147-168 (1999); Sellier et al. “Crystal structure and charge order below the metal-insulator transition in the vanadium bronze β-SrV6O15” Solid State Sciences 5:591-599 (2003); Bulgakov et al. “Laser ablation synthesis of zinc oxide clusters: a new family of fullerenes?” Chem. Phys. Lett. 320:19-25 (2000); Citeau et al. “A novel cage organotellurate(IV) macrocyclic host encapsulating a bromide anion guest” Chem. Commun., pp. 2006-2007 (2001); Gigant et al. “Synthesis and Molecular Structures of Some New Titanium(IV) Aryloxides” J. Am. Chem. Soc. 123:11623-11637 (2001); Liu et al. “A novel bimetallic cage complex constructed from six V4Co pentatomic rings: hydrothermal synthesis and crystal structure of [(2,2′-Py2NH)2Co]3V8O23” Chem. Commun., pp. 1636-1637 (2001); and “On the formation and reactivity of multinuclear silsesquioxane metal complexes” 2003 Dissertation Thesis of Rob W. J. M. Hanssen, Eindhoven University of Technology.
Exemplary silsesquioxane frameworks are provided in FIG. 1. Silsesquioxanes can be either purchased or synthesized, for example, by hydrolytic condensation of RSiCl3 or RSi(OR)3 monomers (see, for example, Feher et al. J. Am. Chem. Soc. 111:1741 (1989); Brown et al. J. Am. Chem. Soc. 86:1120 (1964); Brown et al. J. Am. Chem. Soc. 87:4313-4323 (1965)). The nature of the caged structures formed during synthesis (e.g., type of polyhedral, closed versus open) can be directed by manipulation of the reaction conditions including solvent choice, pH, temperature, and by the choice of R-group substituent (Feher et al. Polyhedron 14:3239-3253 (1995)). Additional silsesquioxane frameworks (e.g., for derivatization with nanostructure binding moieties) are available from Hybrid Plastics (Fountain Valley, Calif.; on the world wide web at hybridplastics.com).
Typically, the silsesquioxane frameworks are coupled to one or more nanostructure binding moieties prior to use as compositions or in the methods of the present invention. Any of a number of standard coupling reactions known in the art can be used to derivatize the silsesquioxane framework, e.g., with one or more nanostructure binding head groups. See, for example, the reactions described in Feher et al. Polyhedron 14:3239-3253 (1995). Additional information regarding general synthesis techniques (as known to one of skill in the art) can be found in, for example, Fessendon et al. Organic Chemistry, 2nd Edition, Willard Grant Press, Boston Mass (1982); Carey et al. Advanced Organic Chemistry, 3rd Edition, Parts A and B, Plenum Press, New York (1990); and March Advanced Organic Chemistry, 3rd Edition, John Wiley and Sons, New York (1985). Optionally, the standard chemical reactions described therein are modified to enhance reaction efficiency, yield, and/or convenience.
Silsesquioxane compositions for use as first coatings in the present invention include (but are not limited to) the compositions provided in FIGS. 5A-5I and Table 1.
Phosphosilicate ligands are another preferred embodiment for use in the compositions and methods described herein. As depicted in FIG. 2, the phosphate group on the phosphosilicate ligand can be utilized to couple the ligand to a nanostructure. Preferably, phosphosilicate ligands that could be thermally decomposed into SiO2 are utilized in the methods and compositions of the present invention; shells incorporating SiO2 would lead to higher barrier height than ZnS, and potentially higher temperature tolerances during subsequent processing or manufacturing steps. Exemplary phosphosilicate ligands are provided in FIGS. 5A-5B.
Additional ligands having thiol moieties as the nanostructure binding head groups are depicted in FIGS. 5D-5I. It will be evident that certain nanostructure binding groups are preferred for certain nanostructure compositions; for example, ligands having thiol (e.g., aryl thiol) moieties are preferred ligands for certain metal nanostructures (e.g., Pd nanostructures).
In other embodiments of the present invention, the ligand coating used to coat the nanostructures is a polyoxometalate. Polyoxometalates are metal-oxygen cluster anions, typically formed from early transition metals (V, N, Ta, Mo and W) in their highest oxidation state. Numerous derivatives can be prepared from polyoxometalate compositions, including halide, alkoxyl, thiol, phospho, and organosilyl derivatives; for a good review, see Gouzerh et al. Chem. Rev. 98:77-111 (1990). For example, polyoxovandanate derivatives can be used as first coatings in the compositions and methods of the present invention. The first ligands would then be converted to a second coating comprising vanadium oxide, having properties comparable to those of silicon oxides.
The polyoxometalates can be used as a first coating on the nanostructure, and subsequently converted to a second coating having differing properties. Certain polyoxometalates (for example, acid forms of molybdenum and tungsten-based polyoxometalates) have photochromic or electrochromic properties, which can be reduced or altered upon conversion to a second coating (e.g., by treatment with an organic reducing agent, or by exposure to an externally applied electric field (see, e.g., Yamase Chem. Rev. 98:307-325 (1998)).
Optionally, the second ligand includes a catechol functional group, which can be used to tune the electrochemical properties of the second coating. Catechol functional groups for use in the present invention include, but are not limited to, pyrocatechol, salicylic acid, and 2,2-biphenol (see, for example, Gigant et al. J. Am. Chem. Soc. 123:11632-11637 (2001)).
Exemplary compositions for use as the first coating in the present invention are provided in Table 1 below, as well as in FIGS. 5A-51 and 6.
Com- pound 1 Com- pound 2 Com- pound 3 Com- pound 4 Com- pound 5 Com- pound 6 Com- pound 7 Com- pound 8 Com- pound 9 Com- pound 10 Com- pound 11 Com- pound 12 Com- pound 13
Other exemplary compositions for use as the first coating include, but are not limited to, compounds like Compounds I-3, 5-6, and 8-13, but where R is an organic group or a hydrogen atom. For example, R can be a hydrocarbon group. In certain embodiments, R is an alkyl group (e.g., a cyclic alkyl group or a short alkyl group having fewer than 20 or even fewer than 10 carbon atoms), an aryl group, an alkylaryl group, an alkenyl group, or an alkynyl group. For example, in some embodiments, R is an isobutyl group, a methyl group, a hexyl group, a cyclopentyl group, or a cyclohexyl group.
Optionally, the nanostructures are associated with the surface of a substrate, such as a silicon wafer or a TEM grid. In some embodiments, the substrate has been treated with a composition for association with the nanostructures, such as a functionalized self-assembly monolayer (SAM) ligand. Exemplary compositions for functionalizing the substrate surface include a silicon nitride coating, a silane ligand having a nanostructure binding moiety, or other chemical moiety that can provide or accept a proton for hydrogen-bonding to the coated nanostructure (e.g., amine, alcohol, phosphonate, fluorine or other non-carbon heteroatom). For example, the silane ligand can include structures having the formula [X3Si-spacer-binding group(s)] where X is a Cl, OR, alkyl, aryl, other hydrocarbon, heteroatom, or a combination of these groups, and where the spacer is an alkyl, aryl and/or heteroatom combination. Optionally, the structure of the ligand can be responsive to light activation, leading to crosslinking of ligands (e.g., to each other, or the surface of the SAL coated substrate) via inclusion of a photo-crosslinkable group. Exemplary surface ligands for use in the present invention (referred to generically as “SAL” in FIG. 4) are commercially available from Gelest Inc. (Tullytown, Pa.; on the world wide web at gelest.com).
Nanostructures, such as nanocrystals, quantum dots, nanoparticles and the like, can be fabricated by a number of mechanisms known to one of skill in the art. Furthermore, their size can be controlled by any of a number of convenient methods that can be adapted to different materials, and they are optionally washed to remove excess surfactants remaining from their synthesis and/or excess ligands. See, e.g., Scher et al. U.S. patent application Ser. No. 10/796,832, filed Mar. 10, 2004; Scher et al. U.S. Provisional Patent Application Ser. No. 60/544,285, filed Feb. 11, 2004; Scher et al. U.S. Provisional Patent Application Ser. No. 60/628,455, filed Nov. 15, 2004; and Whiteford et al. U.S. Provisional Patent Application Ser. No. 60/637,409, filed Dec. 16, 2004; and references therein.
The nanostructures employed in the nanostructure-containing compositions of the present invention can be fabricated from essentially any convenient materials. For example, the nanocrystals can comprise inorganic materials, e.g., a semiconducting material selected from a variety of Group II-VI, Group III-V, or Group IV semiconductors, and including, e.g., a material comprising a first element selected from Group II of the periodic table and a second element selected from Group VI (e.g., ZnS, ZnO, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, and like materials); a material comprising a first element selected from Group III and a second element selected from Group V (e.g., GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, and like materials); a material comprising a Group IV element (Ge, Si, and like materials); a material such as PbS, PbSe, PbTe, AlS, AlP, and AlSb; or an alloy or a mixture thereof. Metals such as Pd, Pt, Au, Ag, Ni, Fe, Sn, Zn, Ti, Ir, and Co can also be used in the synthesis of nanostructures for use in the present invention, as can metal oxides. Further details regarding nanocrystalline structures for use in the present invention can be found, for example, U.S. patent application Ser. No. 10/656,802, filed Sep. 4, 2003, incorporated herein by reference in its entirety for all purposes.
The methods of the present invention can be used to generate a shell or second coating on any of a number of nanostructures, including, but not limited to, a nanocrystal, a nanodot, a nanowire, a nanorod, a nanotube, a quantum dot, a nanoparticle, a nanotetrapod, a nanotripod, a nanobipod, a branched nanostructure, and the like. Furthermore, the methods of the present invention are not limited to nanostructures prepared by a specific synthetic approach. For example, organometallic solution-based syntheses of Pd, CdSe, CdTe and CdS nanocrystals typically employ various surfactants and/or fatty acids as solubilizing agents (see, e.g., Peng et al. U.S. Patent Publication No. 2002/0066401, Peng et al. U.S. Patent Publication No. 2003/173541, Kim et al. NanoLetters 3:1289-1291 (2003), and Qu et al. NanoLetters 1:333-337 (2001), and references cited therein). Nanostructures prepared using these or other weakly-binding organic compositions can be employed in the methods of the present invention.
In another embodiment, the nanostructures are coupled to or associated with a substrate surface (e.g., a solid phase embodiment rather than in solution). The organic surfactants on the nanostructure surface can be removed in situ, for example, via a low temperature organic stripping process (at temperatures<500° C., and optionally between 200-350° C.). The stripping process is optionally followed by oxidation using, e.g., a reactive oxygen species. The replacement ligand (e.g., the ligand of the first coating) is subsequently applied to the nanostructure by any of a number of techniques known in the art (vapor deposition, spraying, dipping, etc.).
Further details regarding monolayer formation can be found, for example, in Heald et al. U.S. Provisional Patent Application Ser. No. 60/671,134, filed Apr. 3, 2005, incorporated herein by reference in its entirety for all purposes.
After deposition and monolayer formation, the substrate can be thermally annealed to cure the layer of first coating (and thereby form the second layer, which in some embodiments is a rigid insulating shell, on the first surface of the nanostructure). The technique used for the curing step will depend upon the type of ligand composition employed in the method. The curing can be done under inert atmosphere, such as argon or nitrogen, or under oxygen, for example. The temperature of the curing process can be adjusted for the surface ligands. For example, curing the composition can involve heating the nanostructure having the ligand composition associated therewith to form the rigid shell on the nanostructure surface. Heating can be performed in one or more stages, and using various equipment such as a hot plate or quartz furnace (see Yang et al. Proc. Natl. Acad. Sci. 25:339-343 (2001)). In some embodiments, the ligand:nanostructure complex is heated to less than about 500° C., and optionally, to between 200-350° C. Thermal curing of silsesquioxane ligands typically involves heating the silsesquioxane-containing composition to temperatures of less than about 500° C., and preferably less than about 350° C., thereby transforming the cage structures into a network structure. In other embodiments involving silicon-containing ligands, the thermal curing process decomposes the first coating into a second coating of SiO2. Conversion of the first coating to the second coating (or shell) can be monitored, for example, via thermogravimetric analysis using an FTIR spectrometer (see Yang (2001) supra, and references cited therein).
Compositions for Modulating Nanostructure Energy Levels
In one aspect, the present invention is directed toward methods and ligand compositions for manipulating the electronic properties of nanostructure compositions. The ligand-associated nanostructure compositions are preferably employed in the absence of a polymeric matrix, thereby removing a factor that might interfere electronically with the nanostructure, as well as minimizing the organics present in the device. The compositions can be readily incorporated into the manufacturing process of various nanostructure-containing devices, such as those described in Scher et al. U.S. patent application Ser. No. 10/778,009, filed Feb. 11, 2004.
Thus, in one aspect the methods of the invention employ various ligand compositions to alter the energy state of a nanostructure composition. In preferred embodiments, the ligand compositions of the invention include a body structure containing a dipole moiety, and a nanostructure binding moiety coupled to the body structure.
A dipole in essence is a non-uniform charge distribution across a molecule. While dipoles are typically portrayed as a pair of equal and opposite charges within the molecule, the dipole may also arise due to the presence of magnetic poles rather than electric charges (e.g., a defined charge is not necessarily required for the molecule to have a dipole moment). The dipole can be permanent (e.g., due to substantially different electronegativities of constituent atoms) or inducible (e.g., in which the separation of charge occurs, for example, due to exposure to an external factor, such as light).
The process of associating a ligand composition of the invention with a target nanostructure alters the energy levels of the nanostructure, thereby adjusting the electron donor/acceptor ability of the composition. The Fermi level of a solid is the energy level at which the Fermi-Dirac distribution function is equal to 0.5 (e.g., midway between the highest occupied molecular orbital and the lowest unoccupied molecular orbital). Association of two materials (e.g., a nanostructure and a ligand composition) having two differing Fermi levels will result in a contact potential and electron flow as the Fermi levels equilibrate. Thus, it would be highly advantageous to be able to manipulate the relative Fermi levels of the components in a nanostructure composition; how well the energy levels of components in a device align or match are important considerations during the process of component selection and device fabrication.
Energy levels of nanoscale components are different from the energy levels of their non-nanoscale (bulk) counterparts. These differences are due, at least in part, to quantum confinement effects. As provided herein, modulation of the energy levels of nanostructure compositions (beyond that due to quantum confinement effects) is possible by modification of the nanostructure surface using, e.g., the ligand compositions of the invention. Specifically, introduction of dipoles on the nanostructure surface affects the energy levels of the nanostructure. While the invention is not limited to a particular theory, the presence of the charge distribution provided by the dipole is thought to assist in the transport of electrons and/or holes in a manner similar to that described for the use of a forward bias current. In addition, the use of electroactive ligands such as the dipole ligands provided herein optionally improves the solubility, and hence the morphology, of the nanostructure composition; upon appropriate alignment of the energy levels of the ligand, the transportation and/or extraction of charges is not diminished or otherwise affected.
Further energy level adjustment of the dipole ligand with respect to the nanostructure can be accomplished by the addition of electron-donating or electron-withdrawing characteristics to the ligand (either as part of the dipole, or in addition to the dipole). Incorporation of electron donor-type dipole ligands would likely increase the energy level of the highest occupied molecular orbital (HOMO) of the ligated nanostructure composition as compared to the nanostructure sans ligand. Conversely, utilization of ligands having electron-withdrawing constituents (e.g., electron acceptors) would potentially decrease the HOMO level. Through selection of dipole and supplementation of the ligand with electron-donating or electron-withdrawing moieties, the energy levels of a given nanostructure composition can be deliberately modulated and/or matched according to the desired band level alignment of a given device.
Various aspects of the dipole ligand can be altered, depending upon the desired effect upon the nanostructure energy level. For example, the magnitude of the dipole can be adjusted, as can the number of dipoles present within a given ligand (e.g., the multiplicity). A selected ligand composition can be further modified or supplemented with additional chemical constituents, e.g., to manipulate other physical parameters, such as solubility characteristics of the ligand composition. Furthermore, different nanostructure binding moieties can be employed, based upon the composition of the nanostructure to be bound.
Nonconjugated Ligand Compositions
In some embodiments, the invention provides ligand compositions having a nonconjugated body structure containing a dipole moiety, as well as a nanostructure binding moiety coupled to the nonconjugated body structure at a first position. While the elements of the dipole may be conjugated (e.g., to facilitate charge separation), the core of the body structure is not conjugated in these embodiments (e.g., charge is not transferred through or across the body structure).
An exemplary type of nonconjugated body structure for use in the ligand compositions of the invention are carborane compositions. Carboranes are typically icosahedral structures composed of carbon, boron and hydrogen (e.g., C2B10H12). The structures are remarkably stable to both thermal and chemical conditions; however, they can be modified at either the mildly acidic C—H vertices or at the less reactive B-H positions (see, e.g., Jiang et al. Inorg. Chem. 34:3491-3498 (1995); and Zheng et al. Inorg. Chem. 34:2095-2100 (1995)).
Optionally, the carborane-type ligand compositions of the invention include one or more additional substitutions. Exemplary chemical moieties for coupling to the carborane body structure include, but are not limited to, various heteroatoms, alkyl moieties, alkenyl moieties, alkynyl moieties, and aromatic groups. Optionally, a combination of additional substituents can be employed in the ligand composition.
Carborane ligands for use in the present invention can be prepared using conventional chemistries, such as those provided in Li et al. (1991) Inorg. Chem. 30:4866-4868; Zheng et al. (1995) Inorg. Chem. 34:2095-2100; Marshall et al. Organometallics 20:523-533 (2001); Fox et al. J. Material Chem. 12:1301-1306 (2002); and Lee et al. Chem Comm. 2485-2486 (2000).
Exemplary carborane-type ligand compositions include, but are not limited to, the compounds provided in Table 2. The darkened vertices denote the position of carbon atoms within the structure.
Other boron-containing compositions can also be employed as the nonconjugated body structure in the ligand compositions. For example, boron derivatives (e.g., boronic acids) of polyhedral oligomeric silsesquioxanes (POSS), including the silsesquioxanes described above and in U.S. Provisional Patent Application Ser. No. 60/578,236, filed Jun. 8, 2004 can be employed as ligand compositions. These ligand compositions can be prepared, for example, by functionalizing the free hydroxyl groups of the silsesquioxane or other silicon oxide cage complex using a Lewis acid boron, e.g., B(OR)3, where each R is (independently) an alkyl moiety or a hydrogen.
In an alternate embodiment, the nonconjugated body structure for use in the ligand compositions of the invention is a fluorine-containing composition. In some embodiments, the fluorine containing composition includes a silicon monofluoride (SiF) or a SiF derivative. In other embodiments, the ligand composition is trifluoroacetic acid (in which the carboxyl group functions as the nanostructure binding moiety).
In a further embodiment of the invention, the ligand composition includes a nanostructure binding moiety coupled to a light-activated intramolecular salt. One embodiment of this type of ligand is H2O3PCH2CH2CH(NH3+)CH2COO−.
Conjugated Ligand Compositions
In a further aspect, the invention provides various dipole-containing ligand compositions that contain a conjugated body structure. For example, the invention provides ligand compositions for modulating nanostructure energy levels having a body structure comprising a light-activated spiropyran salt, and a nanostructure binding moiety coupled to the body structure (e.g., at a first position). Spiropyrans are photochromic materials that can be converted from a conjugated spirobenzopyran ring structure to an (often colored) merocyanine open-ringed structure.
In another embodiment, the invention provides ligand compositions for modulating nanostructure energy levels having a body structure comprising a boron-containing oligomer, and a nanostructure binding moiety coupled to the body structure (e.g., at a first position). Optionally, the boron-containing oligomer is a composition having the formula (A-B)n, where A is an aryl moiety, and B is a boron atom. In these compositions in which the boron atom alternates with the aryl group, the boron atoms are preferably positioned para, or optionally meta, to one another (e.g., they are not adjacent to one another on an aromatic ring structure). Exemplary aryl moieties for use in the boron oligomeric compositions include, but are not limited to, a benzene, a thiophene, a phenylene, an aniline, and a pyridine.
An exemplary ligand composition includes, but is not limited to, the compound provided in Table 3.
In one embodiment, the ligand composition includes a body structure comprising a thiophene moiety and a nanostructure binding moiety coupled to the body structure at a first position. The body structure optionally comprises a dipole, and the body structure optionally includes two, three, four, or even more thiophene moieties. The ligand optionally comprises a boron atom, e.g., within the nanostructure binding moiety. For example, the nanostructure binding moiety can be a boronic acid group, as in exemplary compound 16.
In addition to the ligand structures provided herein, additional conjugated organic body structures which can be derivatized with dipole elements can be found, e.g., in PCT Publication No. WO2004/022714 and related Whiteford et al. U.S. patent application Ser. No. 10/656,910 and Whiteford et al. U.S. patent application Ser. No. 10/928,625.
Nanostructure Binding Moieties
The energy level modulating ligand compositions of the invention are most effective when physically coupled to the surface of the nanostructure. Attachment can be achieved via a nanostructure binding moiety, e.g., a chemical constituent either naturally part of or added to a selected body structure, which chemical constituent can interact with and bind to or otherwise associate with the nanostructure. Exemplary chemical moieties for use as a nanostructure binding moiety in the methods and compositions of the invention include, but are not limited to, phosphonic acid, phosphinic acid, carboxylic acid, hydroxyl, amine, amine oxide, phosphine, phosphine oxide, phosphonate, phosphonite, carbamate, urea, pyridine, isocyanate, amide, nitro, pyrimidine, imidazole, salen, dithiolene, catechol, N,O-chelate ligand, P,N-chelate ligand, and thiol moieties (or combinations thereof). Alternatively, nitrogen-containing aromatic compounds or heterocycles (e.g., imidazoles, benzoimidazoles, pyridines, pyrimidines, purines, or quinolines) can also be used as nanostructure-binding head group moieties in the compositions of the invention. Additional exemplary nanostructure binding groups have been noted above. (Similarly, any of these nanostructure binding groups can be employed in the other ligands described herein.) Exemplary compounds include, but are not limited to, derivatives of 2-methylpyridine, 3-ethylpyridine, 4-chloropyridine, collidine, dimethylquinoline, and other compounds commonly used as nanostructure growth terminators (see, e.g., Alivisatos et al. U.S. Pat. No. 6,306,736). Optionally, a ligand composition can bear two or more nanostructure binding moieties. Additional information regarding functional groups for associating ligands to nanostructures is provided, e.g., in Whiteford et al. PCT Publication No. WO2004/022714.
Furthermore, a second dipole can optionally be coupled to any of the ligand compositions provided herein. Typically, this second dipole is coupled, e.g., to the nonconjugated or conjugated body structure, at a second position relative to the first position (at which the nanostructure binding moiety is attached).
The present invention also provides nonpolymeric nanostructure compositions having a plurality of nanostructures, wherein each member nanostructure is coupled to a plurality of a selected ligand composition.
Methods for Modulating Nanostructure Energy Levels
In addition to various ligand compositions, the invention also provides methods for modulating an energy level of a nanostructure in the absence of a polymeric matrix. The methods of the invention include the steps of a) providing a nanostructure having a first energy level; b) selecting a ligand composition comprising a dipole, wherein the ligand composition has a second energy level as compared to the first energy level of the nanostructure; and, c) associating or coupling the ligand composition to a surface of the nanostructure, thereby modulating the energy level of the nanostructure.
The “band theory of solids” proposes that the electron energy states of atoms in a solid composition can be envisioned as bands of energy separated by gaps, rather than as discrete energy states (e.g., as seen for free atoms). Conductivity is determined by the availability of electrons in the conduction band, e.g., the lowest unoccupied molecular orbital (LUMO), which in turn is dependent upon the band gap, e.g., the energy necessary for an electron to transition between the valence band, e.g., the highest occupied molecular orbital (HOMO), and the conduction band. In conductive compositions, electrons are readily available since the valence and conduction bands overlap, while in insulators, electrons are not available due to a prohibitively large band gap. However, in semiconductor compositions, the band gap between the HOMO and LUMO is not insurmountable given a moderate input of energy (such as that provided by photon absorbance).
Selecting a Ligand Composition
Association of a ligand composition with the surface of a nanostructure can be used to alter, or modulate, the HOMO and/or LUMO energy levels of the resulting ligand:nanostructure composition, potentially altering the band gap. In addition, the presence of a charge distribution from a dipole within the ligand composition can be used to either assist in the transport of electrons and/or holes.
In some embodiments, the method of the invention is performed using a ligand composition having an energy level that is aligned with the energy level of the nanostructure.
In an alternate embodiment of the methods, modulating the energy level of the nanostructure comprises decreasing the HOMO level of the valence band. This can be achieved using a ligand composition having a dipole that comprises an electron withdrawing moiety. Exemplary dipoles having electron withdrawing characteristics include, but are not limited to, the boron-containing ligands described previously (e.g., carboranes, boron-functionalized polyhedral oligomeric silsesquioxanes, and [aryl-boron]n oligomers). Butyl boronic acid and 4-trimethylsilylphenyl boronic acid can also be used as dipole compositions in the methods of the invention. Dipole ligands with electron-withdrawing characteristics also include light-activated intramolecular salts such as spiropyrans, as well as fluorine-containing compositions, such as trifluoroacetic acid, SiF, and SiF derivatives, as well as ammonium carboxylate-modified phosphonic acids.
In a further embodiment of the methods, modulating the energy level of the nanostructure comprises increasing HOMO level of the nanostructure. This can be achieved, for example, by employing a ligand composition having a dipole comprising an electron donating moiety. Exemplary dipoles having electron donating characteristics include, but are not limited to, conjugated aromatic phosphonic acid ligands such as those provided in PCT Publication No. WO2004/022714, supra.
Associating the Ligand Composition with the Nanostructure
The ligand compositions are coupled to or otherwise associated with to the surface of the nanostructure via the nanostructure binding moiety, or “head group”. Association of the nanostructure binding moiety portion of the dipole ligand composition with the surface of a nanostructure can be achieved by any of a number of approaches known in the art.
Often the nanostructures employed in the methods and compositions of the invention have one or more surfactants (“growth ligands”) associated with the nanostructure surface (e.g., for solubilizing the nanostructure during the synthesis procedure). Typical surfactants employed in nanostructure synthesis include trioctyl phosphine (TOP), trioctyl phosphine oxide (TOPO), hexadecyl phosphonic acid (HDPA), octadecyl phosphonic acid (ODPA), and tri-n-butyl phosphine (TBP), as well as various long chain carboxylic acids (e.g., fatty acids, such as stearic, palmitic, myristic, lauric, capric, caprylic, caproic and butyric acids, as well as other saturated or nonsaturated lipid-like structures).
In some embodiments of the methods, the dipole-containing ligand is coupled to the nanostructure surface by performing a “ligand exchange” with the currently-coupled growth ligand. Since the growth ligand typically has a weaker association with the nanostructure than the dipole-containing ligand, it can be readily exchanged, e.g., by mass action. In one embodiment, exchanging the growth ligand for the ligand composition of the invention involves suspending or dissolving the nanostructures in an organic solvent, and combining the suspended nanostructures with the ligand composition. Solvents that can be used for the exchange process include any that are typically employed in conjunction with nanostructure synthesis and processing, such as toluene, chloroform, chlorobenzene, and the like. The temperature at which the exchanging step is performed will depend upon the ligands involved and may range from room temperature to elevated temperatures equal or greater than 100° C., 200° C., 300° C. and the like. For example, ligands comprising sulfonic acid moieties can be exchanged without substantial heating, and the process optionally can be performed at room temperature.
In another embodiment, the nanostructures are coupled to or associated with a substrate surface (e.g., a solid phase embodiment rather than in solution). The organic surfactants on the nanostructure surface can be removed in situ, for example, via a low temperature organic stripping process (at temperatures<500° C., and optionally between 200-350° C.). The stripping process is optionally followed by oxidation using, e.g., a reactive oxygen species. The replacement ligand (e.g., the dipole-containing ligand) is subsequently applied to the nanostructure by any of a number of techniques known in the art (vapor deposition, spraying, dipping, etc.).
Optionally, the nanostructures can be synthesized or grown in the presence of one or more dipole-containing ligand compositions.
The nanostructures employed in the methods of the invention can be fabricated from essentially any convenient materials and fabricated by a number of mechanisms known to one of skill in the art. For example, the nanocrystals can comprise inorganic materials, e.g., a semiconducting material selected from a variety of Group II-VI, Group III-V, or Group IV semiconductors, and including, e.g., a material comprising a first element selected from Group II of the periodic table and a second element selected from Group VI (e.g., ZnS, ZnO, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, and like materials); a material comprising a first element selected from Group III and a second element selected from Group V (e.g., GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, and like materials); a material comprising a Group IV element (Ge, Si, and like materials); a material such as PbS, PbSe, PbTe, AlS, AlP, and AlSb; or an alloy or a mixture thereof. Metals such as Pd, Pt, Au, Ag, Ni, Fe, Zn, Sn, and Co can also be used in the synthesis of nanostructures for use in the invention. Further details regarding nanocrystalline structures for use in the present invention can be found, e.g., Scher et al. U.S. patent application Ser. No. 10/656,802, filed Sep. 4, 2003, incorporated herein by reference in its entirety for all purposes. Furthermore, nanostructure size can be controlled by any of a number of convenient methods that can be adapted to different materials. See, e.g., Scher et al. U.S. patent application Ser. No. 10/796,832, filed Mar. 10, 2004, and Scher et al. U.S. Provisional Patent Application Ser. No. 60/544,285, filed Feb. 11, 2004. See also references herein.
The type of nanostructure employed is determined in part by the purpose for which it is intended. Nanostructures for use in the methods described herein include, but are not limited to, nanocrystals, nanodots, nanowires, nanorods, nanotubes, nanoparticles, branched nanocrystals, and the like. While any of these nanostructure embodiments can be used in the invention, spherical or nearly spherical nanostructures such as nanodots and/or quantum dots are particularly useful for the generation of nanostructure-based photovoltaic devices. For many embodiments, the diameter (e.g., a first dimension) of the nanodot or quantum dot is less than about 20 nm, or 15 nm, or 10 nm, and optionally less than about 8 nm, 6 nm, 5 nm, or 4 nm. In some embodiments, the nanostructure diameter ranges from about 2 nm to about 4 nm, or optionally less than or equal to about 3.5 nm.
In one preferred embodiment, the methods of the invention employ nanostructures comprising a boron containing ligand composition such as compound 16 and a nanostructure comprising InP or CdSe.
Optionally, the nanostructures are associated with the surface of a substrate, such as a silicon wafer or a TEM grid. Exemplary compositions for functionalizing the substrate surface include a silicon nitride coating, a silane ligand having a nanostructure binding moiety, or other chemical moiety that can provide a proton for hydrogen-bonding to the coated nanostructure (e.g., amine, alcohol, phosphonate, fluorine or other non-carbon heteroatom).
Methods for Electron Sweeping
The present invention also provides methods for creating an internal bias field in a nanostructure composition, e.g., for extraction of electrons or holes. The method includes the steps of coupling a photoactivatable composition to a surface of a nanostructure, which composition forms a dipole upon activation, and activating the composition and creating the dipole, thereby forming an internal bias field.
In some embodiments, the photoactivatable composition includes an intramolecular salt, and optionally a light-activated intramolecular salt. The spiropyran ligands described herein are exemplary light-activated intramolecular salts that can be used in the methods.
Optionally, the method further includes the step of extracting one or more holes or electrons from the nanostructure, e.g., by transporting the electrons or holes toward an electrode. The internal bias fields thus created are particularly useful for nanostructure components of photovoltaic cells.
Methods for Reducing Charge Diffusion
Many of the ligand compositions of the present invention have electron withdrawing characteristics and can be utilized as electron-withdrawing compositions in the present methods (e.g., silicon oxide cage complexes such as silsesquioxanes). In some embodiments, the electron withdrawing composition includes a fluorine atom. For example, fluorine-containing ligand compositions such as F−, SiF, an SiF derivative, or a fluorine polymer such as polytetrafluoroethylene can be employed in the methods. In other embodiments, the ligand composition is a boron-containing composition (e.g., an aryl-boron oligomer or a boronic acid composition). Optionally, the electron withdrawing composition includes a nanostructure binding group, such as a phosphonic acid moiety, phosphonate ester, or other nanostructure binding moiety such as those described herein, for coupling to the nanostructure surface.
Optionally, the first and second properties of the ligand compositions of the present invention are photochromism-related properties (e.g., involving color changes induced in the coating by an incoming stimulus, such as light or other incident electromagnetic radiation). In some embodiments, the electron withdrawing composition comprises a light-activated intramolecular salt, e.g., a spiropyran. Exemplary intramolecular salts for use in the methods and compositions of the present invention include, but are not limited to, HOOCCH2CH(NH(CH3)2)CH2CH2PO3H2. See also Léaustic et al. “Photochromism of cationic spiropyran-doped silica gel” New. J Chem. 25:1297-1301 (2001) and references cited therein.
Additional ligand compositions for use in the methods include, but are not limited to, the silicon oxide cage complexes and silsesquioxane compositions described above and in U.S. Provisional Patent Application Ser. No. 60/578,236, filed Jun. 8, 2004. For example, boron- or other metal-substituted silsesquioxane compositions can be employed in the methods.
The methods for reducing charge diffusion are particularly useful when employed in the productions of compositions for use in discrete quantized photon generation and transfer media, and/or discrete quantized charge storage or charge transfer media. Thus, in one class of embodiments, the plurality of nanodots (or quantum dots or other nanostructures) comprises discrete quantized photon generation and transfer media or discrete quantized charge storage or charge transfer media.
The nanostructure-containing compositions of the present invention are particularly useful for the construction of flash memory constructs. Flash memory is a type of electrically-erasable programmable read-only memory (EEPROM) that can be rapidly erased and reprogrammed Devices utilizing this type of constantly-powered, nonvolatile memory can operate at higher effective speeds than standard EEPROM devices, since the memory is altered in blocks, instead of one byte at a time.
Flash memory typically encodes a single bit per cell, which comprises two transistors (a control gate and a floating gate) separated by a thin oxide layer. The cell is characterized by the specific threshold voltage between the two gates. Electrical charge is programmed/stored on the floating gate, which also controls the two possible voltage levels between the transistors (the on/off status of the cell). Multi-bit technology is also being developed, in which the cells have two or more voltage thresholds (i.e., the voltage across each cell has been divided into greater than two levels). Additional details of nanostructure-based memory devices, transistors, and the like can be found, e.g., in Duan et al. U.S. patent application Ser. No. 11/018,572, filed Dec. 21, 2004.
The present invention provides novel processes for producing heterostructural nanocrystals, e.g., nanocrystals that are comprised of two or more different compositional elements where the different elements together impart useful properties to the nanocrystals. As noted herein, such heterostructures are typically embodied in a core-shell orientation, where a core of a first material is surrounded by a shell of a second material. It is worth noting that the first material can comprise a conductor, a semiconductor, or an insulator (e.g., a dielectric), and the second material can likewise comprise a conductor, a semiconductor, or an insulator (e.g., a dielectric), in any possible combinations (e.g., two conductive materials, a conductive material and an insulator, etc.). The methods of the present invention provide flexibility of processing to allow more facile fabrication of these nanocrystals, as well as manipulation of certain parameters, e.g., sizes in the sub-10 nm range, that were previously not attainable. As a result, it is expected that any application to which typical core-shell nanocrystals were to be put would be a potential application for the compositions of the present invention, e.g., those nanocrystal compositions made in accordance with the processes described herein. In addition, a variety of additional applications will be enabled by the abilities that are gained from these novel processes.
Approximately 20 hours after the addition of ClP(O)(OEt)2, the volatile components were removed by vacuum transfer. The residue was extracted with hexane (3×8 mL) and the volatiles removed again by vacuum transfer. The residue was dissolved in 1.25 mL of toluene and precipitated out of solution as an oil with 6 mL of acetonitrile. The upper phase was discarded and the precipitation process repeated twice. Then the oil was dissolved in 6 mL of THF, 2 mL of toluene and eventually about 6 mL of acetonitrile. The last solvent was added slowly with mixing until the solution turned cloudy. Then the mixture was cooled to −35° C. overnight, which produced some white micro-crystals. The supernatant was removed and the volatile solvents removed by vacuum transfer until at about one third of the original starting volume remained, thus providing a substantial quantity of white micro-crystals. The remaining supernatant was removed leaving the product in the flask. Then the white crystalline product 2 was dried under vacuum until a pressure of <0.010 torr was attained for 1 hour. The product was isolated as white micro-crystals 0.320 g, 0.313 mmol or 27.5% yield. Mass Spec: ESI-TOF(−) m/z 1034 [M-H+ Na], ESI-TOF(+) m/z 1011 [M-H]. NMR 31P {1H} NMR (162 MHz, Tol-d8, 25 C) δ −11.3 (s, 1P).
Nanocrystal-based capacitors can be prepared, e.g., as a demonstration of the feasibility of nanocrystal-based charge storage devices such as flash memory devices. To fabricate such an example device, a silicon wafer with a 3-6 nm thick tunnel oxide layer on it is prepared. Palladium quantum dots having a ligand composition of the invention (e.g., the POSS ligand illustrated in FIG. 5F) associated therewith are prepared by surfactant exchange or by synthesis in the presence of the ligand and suspended in an organic solvent such as toluene. The nanocrystals are then spun or dropped onto the surface of the oxide-coated wafer, wet, and dried down. Excess nanocrystals are rinsed off, leaving basically a monolayer of nanocrystals on the wafer. The wafer is baked in an atmosphere comprising oxygen at 250° C. for 10-30 minutes to cure the ligand composition and form the second coating (e.g., an SiO2 shell). Another oxide layer (e.g., an SiO2 layer) is deposited on the nanocrystals by chemical vapor deposition, and chrome and gold are evaporated onto the oxide layer to form an electrode. The device can then be characterized by measuring CV curves before and after applying program and erase voltages.
Synthesis of Boronic Acid-Containing Ligands
FIG. 7 depicts a chemical synthesis scheme for one embodiment of a boron-containing ligand composition of the present invention. The substituted thiophene tail intermediate was prepared starting with 2,3-dimethoxythiophene 75. The methoxy groups on the substituted thiophene molecule were cyclized in the presence of 2,2-dibutyl-1,3-propanediol 76, p-toluenesulfonic acid and toluene at 150° C. The cyclic substituted thiophene moiety was subjected to a stannylation reaction in the presence of trimethyltinchloride (Me3SnCl) to yield a stannylated substituted thiophene 78.
Di-thiophene-containing body structure 74 was then coupled to two equivalents 78 to form intermediate body structure 79. The boronic acid moiety —B(OH)2 was then added to intermediate 79 to form boron-containing ligand 16.
FIG. 8 depicts two routes to the synthesis of the O-methylated form of boronic acid ligand 16.
The resulting product was analyzed by MALDI-TOF and ESI-TOF mass spectrometry (spectra not shown). A number of boron-containing derivatives are seen, such as those shown in Table 4. Intermediate 79 is also detected by MALDI-TOF MS.
While the foregoing invention has been described in some detail for purposes of clarity and understanding, it will be clear to one skilled in the art from a reading of this disclosure that various changes in form and detail can be made without departing from the true scope of the invention. For example, all the techniques and compositions described above can be used in various combinations. All publications, patents, patent applications, and/or other documents cited in this application are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication, patent, patent application, and/or other document were individually indicated to be incorporated by reference for all purposes.
1. A method for modulating an energy level of a nanostructure in the absence of a polymeric matrix, the method comprising:
providing a nanostructure having a first energy level;
selecting a ligand composition comprising a dipole, wherein the ligand composition has a second energy level as compared to the first energy level of the nanostructure; and,
associating the ligand composition with a surface of the nanostructure, thereby modulating the energy level of the nanostructure.
2. The method of claim 1, wherein the dipole comprises an electron withdrawing group, and wherein modulating the energy level of the nanostructure comprises decreasing a highest occupied molecular orbital (HOMO) level.
3. The method of claim 2, wherein the electron withdrawing group comprises one or more boron atoms.
4. The method of claim 3, wherein the ligand composition comprises butyl boronic acid, 4-trimethylsilylphenyl boronic acid, a carborane, or a boron derivative of a polyhedral oligomeric silsesquioxane (POSS).
5. The method of claim 2, wherein the electron withdrawing group comprises one or more fluorine atoms.
6. The method of claim 5, wherein the ligand composition comprises trifluoroacetic acid or a SiF derivative.
7. The method of claim 2, wherein the ligand composition comprises an ammonium carboxylate-modified phosphonic acid.
8. The method of claim 2, wherein the ligand composition comprises a spiropyran salt.
9. The method of claim 1, wherein the dipole comprises an electron donating group, and wherein modulating the energy level of the nanostructure comprises increasing a HOMO level.
10. The method of claim 9, wherein the electron donating group comprises a conjugated aromatic phosphonic acid ligand.
11. The method of claim 1, wherein the nanostructure comprises a semiconducting material.
12. The method of claim 11, wherein the semiconducting material comprises a first element selected from group II of the periodic table and a second element selected from group VI.
13. The method of claim 11, wherein the semiconducting material comprises a first element selected from group III of the periodic table and a second element selected from group V.
14. The method of claim 11, wherein the semiconducting material comprises an element selected from group IV.
15. The method of claim 1, wherein associating the ligand composition with the surface of the nanostructure comprises performing a ligand exchange.
16. The method of claim 1, wherein associating the ligand composition with the surface of the nanostructure comprises growing the nanostructure in the presence of the ligand composition.
17. A method for creating an internal bias field for extraction of electrons or holes from a nanostructure composition, the method comprising:
coupling a photoactivatable composition to a surface of a nanostructure, which composition forms a dipole upon activation; and
activating the composition and creating the dipole, thereby forming an internal bias field.
18. The method of claim 17, wherein the photoactivatable composition comprises a light-activated intramolecular salt.
19. The method of claim 18, wherein the light-activated intramolecular salt comprises a spiropyran.
20. The method of claim 17, wherein coupling the photoactivatable composition to the surface of the nanostructure comprises performing a ligand exchange.
21. The method of claim 17, wherein activating the composition comprises exposing the coupled ligand:nanostructure composition to a light source.
extracting one or more holes or electrons from the nanostructure.
23. The method of claim 22, wherein extracting the electrons or holes comprises transporting the electrons or holes toward an electrode.
24. The method of claim 17, wherein the nanostructure is a component of a photovoltaic cell.
25. A method for reducing charge diffusion among a plurality of nanostructures, the method comprising:
coupling a ligand composition comprising an electron withdrawing group to a surface of a member nanostructure; and
forming a dipole on the surface of the member nanostructure and increasing the electron affinity of the nanostructure, thereby reducing charge diffusion among the nanostructures.
26. The method of claim 25, wherein the nanostructures are quantum dots.
27. The method of claim 25, wherein the ligand composition comprises one or more fluorine atoms.
28. The method of claim 27, wherein the ligand composition comprises F—, SiF, or a SiF derivative.
29. The method of claim 27, wherein the composition comprises poly(tetrafluoroethylene).
30. The method of claim 25, wherein the composition comprises a light-activated intramolecular salt.
31. The method of claim 30, wherein the composition comprises a spiropyran.
32. The method of claim 25, wherein the composition comprises a silicon oxide cage complex.
33. The method of claim 25, wherein the composition comprises a silsesquioxane.
34. The method of claim 25, wherein the composition comprises a phosphonic acid moiety.
35. The method of claim 25, wherein the plurality of nanostructures comprises discrete quantized photon generation and transfer media.
36. The method of claim 25, wherein the plurality of nanostructures comprises discrete quantized charge storage or charge transfer media.
3514320 May 1970 Vaughan
5938934 August 17, 1999 Balogh et al.
6107008 August 22, 2000 Howell et al.
6563260 May 13, 2003 Yamamoto et al.
6597496 July 22, 2003 Nayfeh et al.
6614069 September 2, 2003 Rosner et al.
6927454 August 9, 2005 Chan et al.
6936484 August 30, 2005 Kanechika et al.
7070472 July 4, 2006 Dean et al.
7186381 March 6, 2007 Penner et al.
7199393 April 3, 2007 Park et al.
7274035 September 25, 2007 Yang et al.
7422790 September 9, 2008 Scher et al.
7501315 March 10, 2009 Heald et al.
7557028 July 7, 2009 Scher et al.
7585564 September 8, 2009 Whiteford
7692218 April 6, 2010 Barron et al.
7723186 May 25, 2010 Purayath et al.
7851784 December 14, 2010 Kastalsky
20010001703 May 24, 2001 Takahashi et al.
20020118369 August 29, 2002 Misewich et al.
20020137235 September 26, 2002 Rohlfing
20020140023 October 3, 2002 Ohba et al.
20020171125 November 21, 2002 Bao et al.
20030039744 February 27, 2003 Fan et al.
20030224286 December 4, 2003 Barclay et al.
20040000427 January 1, 2004 Wang et al.
20040038440 February 26, 2004 Hatori
20040102050 May 27, 2004 Delamarche et al.
20040194295 October 7, 2004 Green
20040228967 November 18, 2004 Leung et al.
20040256667 December 23, 2004 Oikawa et al.
20050139867 June 30, 2005 Saito et al.
20050161666 July 28, 2005 Park et al.
20060148177 July 6, 2006 Kim
20060163646 July 27, 2006 Black et al.
20070293031 December 20, 2007 Chan et al.
20090155967 June 18, 2009 Purayath et al.
20090170725 July 2, 2009 Yamakawa et al.
1195861 October 1998 CN
1320931 April 2001 CN
1034234 July 2003 EP
1386362 January 2007 EP
2000-022129 January 2000 JP
2001-520937 November 2001 JP
2004515782 May 2004 JP
99/01766 January 1999 WO
99/21934 May 1999 WO
0103208 January 2001 WO
0203430 January 2002 WO
0217362 February 2002 WO
0248701 June 2002 WO
02/100867 December 2002 WO
2004/022714 March 2004 WO
2005001573 January 2005 WO
2005017962 February 2005 WO
2005023923 March 2005 WO
2006023037 March 2006 WO
Third Office Action in related Chinese Application No. 201010503565.3 dated Jun. 3, 2013.
Search Report in related Chinese Application No. 201010503565.3 dated May 28, 2013.
Jan. 11, 2013 Reply to Jul. 9, 2012 Office Action & Search Report of related Taiwan Patent Application No. 94117823. English translation only.
Office Action in related Korean Application No. 10-2007-7000514 dated Jan. 31, 2013.
Preliminary Amendment of related U.S. Appl. No. 11/147,670, filed Sep. 15, 2005.
Office Action of related U.S. Appl. No. 11/147,670 mailed Apr. 14, 2006.
May 22, 2006 Reply to Office Action of related U.S. Appl. No. 11/147,670.
Notice of Allowance and Examiner Interview Summary of related U.S. Appl. No. 11/147,670 mailed Jan. 4, 2007.
Preliminary Amendment of related U.S. Appl. No. 11/706,730, filed Feb. 13, 2007.
Preliminary Amendment of related U.S. Appl. No. 11/706,730, filed Mar. 29, 2007.
Preliminary Amendment of related U.S. Appl. No. 11/706,730, filed Apr. 19, 2007.
Office Action of related U.S. Appl. No. 11/706,730 mailed Jan. 9, 2008.
Supplemental Office Action of related U.S. Appl. No. 11/706,730 mailed Apr. 9, 2008.
May 7, 2008 Reply to Supplemental Office Action of related U.S. Appl. No. 11/706,730.
Office Action of related U.S. Appl. No. 11/706,730 mailed Aug. 20, 2008.
Nov. 3, 2008 Reply to Office Action of related U.S. Appl. No. 11/706,730.
Notice of Allowance of related U.S. Appl. No. 11/706,730 mailed May 8, 2009.
International Search Report & Written Opinion of International Patent Application No. PCT/US05/020100 dated Feb. 12, 2008.
Office Action & Search Report of related Taiwan Patent Application No. 94117823 dated Jul. 9, 2012.
Office Action & Search Report of related Malaysian Patent Application No. I20052518 dated Oct. 30, 2009.
Office Action of related Korean Patent Application No. 10-2007-7000514 dated Apr. 23, 2012.
Aug. 23, 2012 Reply to Apr. 23, 2012 Office Action of related Korean Patent Application No. 10-2007-7000514.
Office Action of related Japanese Patent Application No. 2007-527681 dated Aug. 29, 2011.
Dec. 16, 2011 Reply to Aug. 29, 2011 Office Action of related Japanese Patent Application No. 2007-527681.
Office Action of related Japanese Patent Application No. 2007-527681 dated Jun. 19, 2012.
Sep. 18, 2012 Reply to Jun. 19, 2012 Office Action of related Japanese Patent Application No. 2007-527681.
Office Action of related Chinese Patent Application No. 201010503565.3 dated Oct. 26, 2011.
Mar. 2, 2012 Reply to Oct. 26, 2011 Office Action of related Chinese Patent Application No. 201010503565.3.
Office Action of related Chinese Patent Application No. 200580018708.9 dated May 21, 2010.
Sep. 30, 2010 Reply to May 21, 2010 Office Action of related Chinese Patent Application No. 200580018708.9.
Office Action of related Chinese Patent Application No. 200580018708.9 dated Oct. 18, 2011.
Office Action of related Canadian Patent Application No. 2,567,907 dated Feb. 28, 2012.
Office Action of related Australian Patent Application No. 2005254490 dated Aug. 13, 2010.
Dec. 6, 2010 Reply to Aug. 13, 2010 Office Action of related Australian Patent Application No. 2005254490.
Office Action of related Australian Patent Application No. 2005254490 dated Jan. 7, 2011.
Feb. 17, 2011 Reply to Jan. 7, 2011 Office Action of related Australian Patent Application No. 2005254490.
Second Office Action in related Chinese Application No. 201010503565.3 dated Oct. 10, 2012.
Dec. 25, 2012 Response to Oct. 10, 2012 Second Office Action in related Chinese Application No. 201010503565.3.
Dec. 14, 2011 Reply to Oct. 18, 2011 Office Action of related Chinese Patent Application No. 200580018708.9.
Cassagrleau, T. et al., “Contiguous Silver Nanoparticle Coatings on Dielectric Spheres,” Advanced Materials (2002) 14(10):732-736.
Sunahara, K. et al., “New BST-silica suspension coating material for dielectric thin films fabricated at low temperatures” Adv Appl Ceramics (2006) 105(3):153-157.
Fan et al. “Three-Dimensionally Ordered Gold Nanocrystal/Silica Superlattice Thin Films Synthesized via Sol-Gel Self Assembly” Adv. Func. Mat. (2006) 16:891-895.
Lim, et al. “Nonvolatile MOSFET memory based on high density WN nanocrystal layer fabricated by novel PNL (Pulse Nucleation Layer) method” Symp on VLSI Tech Digest of Tech Papers (2005) pp. 190-191.
Fan et al., (2000) “Rapid prototyping of patterned functional nanostructures,” Nature, 405:56-60.
Gerion et al. (2001) “Synthesis and properties of biocompatible water-soluble silica-coated CdSe/ZnS semiconductor quantum dots,” J. Phys. Chem. B, 105:8861-8871.
Giersig et al., (1997) “Direct observations of chemical reactions in silica-coated gold and silver nanoparticles”, Adv. Mater., 9(7):570-575.
Schroedter & Weller (2002) “Ligand design and bioconjugation of colloidal gold nanoparticles” Angew. Chem., 41 (17):3218-3221.
Bruchez et al., (1998) “Semiconductor nanocrystals as fluorescent biological labels” Science 281:2013-2016.
Liz-Marzan et al. (1996) “Synthesis of nanosized-gold-silica core-shell particles,” Langmuir, 12:4329-4335.
Tiwari, S. et al., “A silicon nanocrystals based memory” Appl. Phys. Lett (1996) 68(10:1377-1379).
Yang, C-C. et al. “Characterization of poly(silsesquioxane) by thermal curing” Proc. Natl. Sci. Counc. ROC (2001) 25:339-343.
Response to Restriction Requirement filed Feb. 18, 2010 in U.S. Appl. No. 11/299,299.
Requirement for Restriction/Election mailed Feb. 3, 2010 in U.S. Appl. No. 11/299,299.
Notice of Allowance and Fees Due mailed May 28, 2013 in U.S. Appl. No. 11/299,299.
Notice of Allowance and Fees Due mailed Nov. 9, 2012 in U.S. Appl. No. 11/299,299.
Non-Final Rejection mailed May 10, 2012 in U.S. Appl. No. 11/299,299.
Non-Final Rejection mailed Oct. 27, 2010 in U.S. Appl. No. 11/299,299.
Non-Final Rejection mailed Mar. 30, 2010 in U.S. Appl. No. 11/299,299.
Response mailed Aug. 6, 2012 to Office Action in U.S. Appl. No. 11/299,299.
Response mailed Jun. 9, 2011 to Office Action in U.S. Appl. No. 11/299,299.
Response mailed Jan. 7, 2011 to Office Action in U.S. Appl. No. 11/299,299.
Response mailed Aug. 2, 2010 in Office Action in U.S. Appl. No. 11/299,299.
Aug. 19, 2013 Reply to Jun. 3, 2013 Third Office Action in related Chinese Application No. 201010503565.3.
Final Office Action dated Mar. 17, 2011 in U.S. Appl. No. 11/299,299.
Advisory Action dated Jul. 22, 2011 in U.S. Appl. No. 11/299,299.
Final Rejection dated Aug. 30, 2013 in Korean Application No. 10-2007-7000514.
Brown, J.F. et al. “Preparation and characterization of the lower equilibrated phenylsilsesquioxanes” J. Am. Chem. Soc. (1964) 86:1120.
Chae, D-H et al., “Nanocrystal memory cell using high-density SiGeQuantum Dot Array” J. Kor. Phys. Soc. (1999) 35:S995-S998.
Citeau, H. et al. “A Novel cage organotellurate (IV) macrocyclic host encapsulating a bromide anion guest” Chem. Commun. (2001) pp. 2006-2007.
Corso, D. et al., “Localized Charge storage in nanocrystal memories: feasibility of a multibit cell” (Publication and Publication date unknown).
Drexler, H. et al., “Spectroscopy of quantum levels in charge-tunable InGaAs quantum dots” Phys. Ref. Lett. (1994) 73:2252-2255.
Feher, F.J. et al., “Synthesis and characterization of vanadium-containing silsesquioxanes” Inorg. Chem. (1991) 30:1689-1694.
Gigant, K. et al. “Synthesis and Molecular Structures of Some New Titanium (IV) Aryloxides” J. Am. Chem. Soc. (2001) 123:11623-11637.
Gudiksen, M.S. et al. “Diameter-selective synthesis of semiconductor nanowires” J. Am. Chem. Soc. (2000)122:8801-8802.
Gudiksen, M.S. et al. “Synthetic control of the diameter and length of single cyrstal semiconductor nanowires” J. Phys. Chem. B (2001) 105:4062-4064.
Leaustic, A. et al. “Photochromism of cationic spiropyran-doped silica gel” New J. Chem. (2001) 25:1297-1301.
Manna, L. et al. “Synthesis of Soluble and Processable Rod-,Arrow, Teardrop-, and Tetrapod-Shaped CdSe Nanocrystals” J. Am. Chem. Soc. (2000) 122:12700-12706.
Morales, A.M. et al., “A laser ablation method for the synthesis of crystalline semiconductor nanowires” Science (1998) 279:208-211.
Puntes, V.F. et al. “Colloidal nonocrystal shape and size control: The case of cobalt” Science (2001) 291:2115-2117.
Rhule, J.T. et al. “Polyoxometalates in Medicine” Chem. Rev. (1998) 98:327-357.
Appeal filed Oct. 2, 2013 in related Korean Application No. 10-2007-7000514.
Office Action dated Aug. 8, 2014 in counterpart Taiwan Patent Application No. 102120175.
Supplementary European Search Report dated Nov. 21, 2013 in counterpart European Patent Application No. EP 05784268.
Carroll et al., “Electrostatic self-assembly of structured gold nanoparticle/polyhedral oligomeric silsesquioxane (POSS) nanocomposites”, Journal of Materials Chemistry, vol. 14, No. 4, Jan. 1, 2004.
Chua et al, “In Situ Characterization of Methylsilsesquioxane Curing”, J. Electrochem. Soc., vol. 145, No. 11, Nov. 1, 1998.
Van Der Vlugt et al., “POSSphites-monophosphites derived from incompletely condensed silsequioxanes”, Tetrahedron Letters, Pergamon, GB, vol. 44, No. 45, Nov. 3, 2003.
Communication dated Dec. 17, 2013 in counterpart European Patent Application No. EP 05784268.
Response to Office Action filed Mar. 18, 2015 in counterpart Chinese Patent Application No. 2012103445192.
Office Action dated Sep. 3, 2014 in counterpart Chinese Patent Application No. 2012103445192.
Patent Publication Number: 20140017396
Inventors: Jeffery A. Whiteford (Belmont, CA), Mihai A. Buretea (San Francisco, CA), Jian Chen (Mountain View, CA), William P. Freeman (San Mateo, CA), Andreas Meisel (San Francisco, CA), Linh Nguyen (San Jose, CA), J. Wallace Parce (Palo Alto, CA), Erik C. Scher (San Francisco, CA)
Application Number: 14/018,260
International Classification: B05D 5/12 (20060101); C07F 5/02 (20060101);