This patent, makes mention of fully dissolved solutions of solvated fullerenes, graphene, or polymers of fullerenes (i.e. SWNTs), at mg/mL loadings in cyclic terpene, cyclic triterepenes, lactones, fatty acid alcohols, and specific terpene alcohols, following processing consisting of ultrasonication, and ultracentrifugation processing. Another embodiment is for colloidal solutions of fullerenes, graphene, and fullerene polymers (i.e. SWNTs) in cyclic terpene, cyclic triterepenes, lactones, fatty acid alcohols, and specific terpene alcohols, at weight percent loadings following ultrasonication processing. Uses include oil-energy, biological, and electrical-thermal applications.
1. Background of the Invention:
Buckminster-Fullerenes are C60, they are carbon allotropes, which are spherical molecules, also termed buckyballs, composed entirely of carbon. C60 are truncated icosahedrons with a closed-cage structure composed of 20 hexagons and 12 pentagons, and are characterized via mass spectrometry, UV-Visible spectrometry, gas chromatography, and other optical methods.
The structure of buckminster-fullerenes C60 reveals a carbon atom at the vertices of each polygon, and a bond along each polygon edge. This produces a van der Waals diameter of about 1.01 nanometer (nm) or 10.1 Angstrom, per molecule. The nucleus diameter of the C60 molecule is 0.71 nm or 7.1 Angstrom, yielding two bond lengths and 6:6 ring bonds between the two hexagons, and double bonds, which are shorter than the 6:5 bonds between the hexagon and a pentagon. This produces an average bond length of 0.14 nm (1.4 Angstroms), with each carbon structure being covalently bonded to 3 others, thereby producing sp2 hybridization. Since the carbon atoms have 6 electrons, this provides C60 with an electronic structure of u2.4. C60 is not superaromatic since it avoids double bonds in the pentagonal rings, this provides it with poor electron delocalization, allowing it to be an electron deficient alkene that reacts readily with electron rich species.
The exception stability of C60 is due to the geodesic and electronic bonding factors in the non-planar structure. A carbon atom needs 8 electrons in its outer shell to be stable, and it must be covalently bonded to 3 other atoms, leading to 7 electrons in its outer shell. However, one unbounded electron on every carbon atom is free to float around, on all the compound's atoms. Since electrons carry charge, their free electron movement within C60 , its nanometer size, and icosahedral symmetry, and overall geometry provide it with some exceptional electronic structural properties. This also provides C60 with unique physical, chemical, thermal, and electronic properties. C60's high electron affinity of 2.5 eV leads to enhanced reactivity to carbon-carbon double bonds such as alkenes, arenes, free radicals, and/or allows nucleophilic attack by lone pair electrons. C60 can act as a free radical sponge or radical scavenger for the purpose of inactivation of free radicals, which occurs by sacrificing double bonds, or dimer formation.
The fullerene C60 has a conjugated electronic structure, that allows for a high intermolecular interaction. The molecular packing of the crystalline C60 structures controls its solvation properties. Aromatic solvents such as polar aromatic hydrocarbons, and terpenes, lactones, fatty acid alcohols, or other molecules with similar conjugated structures and high intermolecular interactions will allow for unique electron-donor packing of aromatic molecules, which favor solvation.
Carbon nanotubes, namely single-walled carbon nanotubes are of the fullerene structural family, and are allotropes of carbon with cylindrical nanostructures, note that these can often have fullerene capped ends. The carbon nanotubes have novel properties due to their 1-dimensional (1-D) and sp2 orbital hybridization, which provides them with chemical bonds that are similar to graphite. The strong van der Waals forces of carbon nanotubes allows them to align into roped structures, with diameters close to 1 nm, leading to a one-atom thick structure that is a graphene cylindrical sheet. The wrapping of the graphene sheet is commonly represented by pairs of indices (n, m) termed chiral vectors. These (n, m) indices are integers that denote the number of unit vectors along the two directions in the honeycomb crystal lattice of graphene. If m 32 0 these denotes zigzag structure, while n=m leads to armchair, or otherwise, chiral. The diameter of a carbon nanotube is calculated from the (n, m) indices, whereby a typical 1 nm diameter is found for single walled carbon nanotubes. Exotic electrical and thermal properties are found in single-walled carbon nanotubes, and these result from the band gap structure, which can vary from zero to about 2 eV. The electrical properties of carbon nanotubes can show metallic or semiconducting behavior, this is due to the symmetry and unique electronic structure of graphene. For example, if n=m metallic behavior results, or if n−m is a multiple of 3 then the nanotube is semiconducting and possesses very small band gap, otherwise it is a moderate semiconductor. Curvature effects in small diameter carbon nanotubes can of course affect the unique electrical, optical, and thermal properties. Of critical importance is the ability of separating semiconductor and metallic tubes of certain chiralities, and their solvation in solvents that have minimal environmental and human exposure liabilities. While some solvation methods are known these are not suitable for large-scale processing. Most of these solvation methods require density-gradient ultracentrifugation of surfactant wrapped nanotubes, with separation of semiconducting-metallic tubes occurring due to minute changes in density. These notably small density differences, can in turn, separate nanotubes based on diameter, and semiconducting properties. Still other methods use chromatographic, gel electrophoresis, or DNA or macromolecular complexation. Nevertheless current applications of single-walled carbon nanotubes are limited due to their lack of solubility, toxicity, environmental liabilities, and efficient and large-scale processing.
Graphene is the basic structural element of carbon allotropes such as fullerenes and carbon nanotubes, and can be considered a type of flat polycyclic aromatic hydrocarbon. The structure of graphene is a one-atom thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. The carbon-carbon bond is 0.142 nm, which are stacked together to form a graphite layer with an interplanar spacing of 0.335 nm. Graphene can therefore be described as a flat monolayer of carbon atoms that is tightly packed into a two-dimensional honeycomb lattice. This lattice serves as the basic building block for graphitic materials of other dimensionalities. The graphene can therefore be wrapped up into 0-D fullerenes, rolled into 1-D nanotubes, or stacked into 3-D graphite. More accurately, graphene is best described as an infinite alternate polycyclic aromatic hydrocarbon composed of six-membered carbon rings. Graphene shows semi-metal or zero-gap semiconductor properties, and shows exceptionally high electron mobility at room temperature, with the lowest resistivity occurring at room temperature. A unique high opacity for an atomic monolayer of graphene is known, leading to its exotic optical properties, as well unique band gap values, which create unique spin-orbit interactions, quantum Hall effects, and exceptionally high electrical and thermal conductivities. Currently the dispersion of graphene is quite difficult, often requiring chemically processed or unique functionalizations that allow for dispersions in some polar aromatics. Still other chemical modifications are possible following treatment with strong acids leading to oxidation, and exfoliation, and an oxidized graphene structure. However this strongly aggressive chemical processing and caustic use of solvents can present time constraint and human and environmental exposure issues. Still other methods employ hydrogenation of graphene, which alters its chemical and electrical properties. While graphene has many exceptional properties, which are often desirable in electrical and thermal applications, its solubility and time-consuming processing, and functionalization can often limit its use.
A limited number of solvents have been used to dissolve fullerenes, graphene, and polymers of fullerenes such as carbon nanotubes. These true solutions of fullerenes, graphene, and SWNTs, can be made from either strong aggressive acids, aromatic halogenated hydrocarbons, or toxic aromatic hydrocarbon based solvents that present human and environmental exposure liabilities.
Terpenes are hydrocarbon solvents resulting from the combination of several isoprene units, these can be monoterpenes, sesquiterpenes, diterpenes, and/or triterpenes, with some being linear, while others being cyclical in nature. Within these groups there are other families and grouped subcategories, these differ based on their structural or chemical functional groups, some of the ones used in this formulation include monoterpene cyclic ethers, terpene alcohols, associated fatty acid alcohols, cyclic terpenes, associated lactones, cyclic triterpenoid saponins, and cyclic triterpenoid steroidal saponins. This disclosure also employs lactones, which are internal cyclic monoesters, and fatty acid alcohols, which are aliphatic carboxylic acids.
2. Description of Related Art
Colloidal dispersions, emulsions, or other aggregate based solutions have been extensively disclosed and noted in the literature. U.S. Pat. No. 5,612,021; U.S. Pat. No. 7,708,903, and some provisional patents have mainly discussed solubilizing fullerenes into small clusters through the use of aromatic solvents, these make use of clustered fullerenes in terpene-based solvents for cosmetic or refrigerant use.
However, as for the terpene and saponin disclosures to formulate SWNTs in previously published patents, it should be noted that these often fail to mention the specific class of terpenes, and/or type of saponins, or specific structural types, that were used to provide clustered dispersions, leading to a generic use of terpene, terpenoid, or saponin. This presents a complication, given that there are thousands of terpenes, as such using IUPAC or CAS, or chemical family structural names is desired, and should be required.
Previously published patents or disclosures also do not discuss dissolved fullerenes or solutions of fullerenes in cyclic terpenes, where the dissolved solutions or true solutions refer to a lack of aggregates and/or clustering. Some disclosed and published patents have made use of functionalized fullerenes and/or additives such as dispersants, or surfactants, however, while these may increase solubility, these derivatized fullerenes can reduce the conjugation of the molecules and often create steric hindrances leading to decreased reactivities and overall functionalities. The type of saponin dispersants and/or surfactants may also pose an environmental or human exposure liability, very few are nontoxic, which is often not desired.
This patent, solely makes mention of cyclic terpene, cyclic triterepenes, lactones, fatty acid alcohols, and specific terpene alcohols, and their ability to provide dispersions at weight percent loadings using ultrasonication processing, or fully dissolved cyclic based terpene solutions of fullerenes, graphene, or polymers of fullerenes (i.e. SWNTs), at mg/mL loadings following processing consisting of ultrasonication, and ultracentrifugation of at least 325,000 g (RCF) that being 48,609 RPM for 1 hour, or 120,00 g (RCF) that being 29,537 RPM for 4 hours, or a preferred 462,700 g (RCF) that being 58,000 RPM for 1 hour.
The solubilized solutions of fullerenes, graphene, or polymer fullerenes (i.e. SWNTs) in either cyclic terpenes, or cyclic triterepenes, or lactones, or fatty acid alcohols, and/or specific terpene alcohols or combinations thereof, underwent ultrasonication and ultracentrifugation processing steps. The ultracentrifuged, solvated, cluster free solutions could then be characterized using FTIR, UV-Visible spectroscopies, mass spectrometry, and/or other optical methods to accurately and precisely determine the concentration.
This patent also discusses colloidal dispersions of fullerenes, graphene, or polymers of fullerenes (i.e. SWNTs) in cyclic terpenes, cyclic triterepenes, lactones, fatty acid alcohols, and specific terpene alcohols at weight percent loadings, that underwent processing consisting of ultrasonication, and ultracentrifugation at least 325,000 g (RCF) that being 48,609 RPM for 1 hour, or 120,00 g (RCF) that being 29,537 RPM for 4 hours, or a preferred 462,700 g (RCF) that being 58,000 RPM for 1 hour.
Following the ultracentrifugation processing, the colloidal dispersions could undergo optical characterization using FTIR, UV-Visible spectroscopies, mass spectrometry, and/or other optical methods.
Since this patent avoids chemical functionalization, oxidation, or derivitization of the fullerenes, graphene, or polymerized fullerenes (i.e. SWNTs), and/or clustering for the dissolved solutions at the mg/mL loadings this allows for higher enhanced chemical reactivity, meaning electron-donor and molecular packing of solvent-molecule interactions, which allows for true solvation n solvents that have decreased environmental and human exposure liabilities (toxicity).
The ultrasonication strengths and ultracentrifugation speeds are critical for this work as it differentiates this disclosure from other existing published patents and literature.
Colloidal dispersions of fullerenes, graphene, or polymers of fullerenes (i.e. SWNTs) at weight percent loadings, or solutions of 1 mg/mL to 100 mg/mL of fullerenes, graphene, or polymers of fullerenes; in monoterpene cyclic ethers, terpene alcohols, fatty acid alcohols, cyclic terpenes, cyclic triterpene species, lactones, and/or cyclic triterpenoid steroidal species, and/or combinations thereof, result after processing consisting of ultrasonication, and ultracentrifugation of at least 325,000 g (RCF) that being 48,609 RPM for 1 hour, or 120,00 g (RCF) that being 29,537 RPM for 4hours, or a preferred 462,700 g (RCF) that being 58,000 RPM for 1 hour. Following the ultrasonication and/or ultracentrifugation processing, the colloidal dispersions could undergo optical characterization using FTIR, UV-Visible spectroscopies, mass spectrometry, and/or other optical methods.
Monoterpene cyclic ethers are chosen from: 1, 4 cineole, 1, 8 cineole, cineole, eucalyptol, or combinations thereof.
Terpene alcohols or fatty acid alcohols are chosen from: linalool, oleyl alcohol, oleic acid, terpineol, or combinations thereof.
Cyclic terpenes are chosen from: α-terpinene, cinene, or combinations thereof.
Lactones are chosen from: γ-Dodecalactone, γ-octalactone.
Cyclic Triterpenoid saponins used are described as: Consisting of a 30-carbon atom hydrophobic core of the Δ12-oleanone type and aglycone sapogenin moiety bound to hydrophilic glucose such as Quillaja Saponin consisting of quillaic acid and glucuronic acid, with a sapogenin content of no less than 10%, with preferred 20-35% sapogenin content, or calendula saponin with an oleanolic acid genin, with a sapogenin content of no less than 10%.
Cyclic triterpenoid steroidal saponins used are described as: Consisting of at least 27 carbon atoms in cyclic form, and an aglycone sapogenin that is a choline steroid, with a sapogenin content of no less than 10%, with preferred 30-60% sapogenin content, such as yucca Schidigera saponin.
Visual inspection of the cyclic terpene, alcohol, lactone,-based solutions will evidence a color change following full dissolution and solvation of fullerene, graphene, fullerene-polymers (i.e. SWNTs). The color of the solvent being clear, and changing to red, purple, maroon, or gray upon solvation of the fullerene, graphene, or fullerene-polymers (i.e. SWNTs). Optical characterization of these color changes which are intrinsic to solvated fullerene, graphene, fullerene-polymer (SWNTs) is evident in spectral features of these solutions, and common to solvents that contain double bonds, C═C in their structure, which likewise is present in the fullerene, graphene, and fullerene-polymers (i.e. SWNTs).
The similar structures of the cyclic terpenes, terpene alcohols, fatty acid alcohols, lactones, cyclic triterpenoid saponins, and cyclic triterpenoid steroidal saponins, to fullerenes, graphene, and fullerene polymers (i.e. SWNTs), their C═C conjugated structures, degree and/or number of conjugated bonds, and strong polarizability is responsible for the increased solvation abilities. Further the conjugated electronic structures of these molecules allows for a high intermolecular interaction for molecular solid crystals. The molecular packing in the crystal lattice and dense mode of the fullerenes, graphene, and fullerene polymers (i.e. SWNTs), allows the crystalline structures to solvate with aromatic solvents such as aromatic hydrocarbons and cyclic terpenes, lactones, fatty acid alcohols, or other molecules that have similar conjugated or high intermolecular interactions, which confer unique electron-donor packing of aromatic molecules. The combination of polarization forces, degree and number of C═C conjugated bonds, intermolecular interactions, allows for greater molecular packing, and controls the solubility values for both the fullerenes, graphene, and fullerene-polymers (i.e. SWNTs), which is based on the number of C═C bonds present, and available contact area. This allows for full solvation, which are noted following ultrasonication, and ultracentrifugation processing, yielding true solutions, which allow for optical and mass spectrometry characterization.
Other patents and journal articles have referred to electrolyte, polar, and/or ionic liquids work quite well to solvate fullerene polymer species such as SWNTs, graphene, and fullerenes, due to their ability to donate ions and/or neutralize ionized molecules enhancing the t-electron density interactions between aromatic molecules and neighbors. Electrolytes, polar, and/or ionic liquids also posses delocalized charge and poorly coordinated ionic species which can prevent stable crystal lattice packing conformations in the aromatic solutes. Furthermore free electrolyte based solvents such THF, DMF, and DMSO can also posses excess charge on their surface allowing for a closer approach with the fullerene, SWNT, graphene surfaces due to nonspecific electrostatic forces. Nonspecific adsorption of these electrolyte-to-solute species will then favor dissolution, often through an electric double layer type state. The only drawback to these systems is their environmental and human exposure liabilities, mostly in terms of toxicity.
In order for solvation to occur in monoterpene cyclic ethers, cyclic terpenes, cyclic triterpenoid species, cyclic triterpenoid steroidal species, terpene alcohols, fatty acid alcohols, lactones, and/or combinations thereof; or hydrocarbon electrolytes, and polar solvents; an accessible surface area (ASA) of the solute must be readily available to the solvent. For van der Waals surfaces such as a fullerenes, graphene, or fullerene polymers (i.e. SWNTs) this solvent ASA must be taken into account in addition to the increased surface area of the molecules. Increased surface areas of carbon-based nanoparticles allows for enhanced storage of ions, radicals, and electrolyte species for any given volume. This increased surface area together with the ASA of the van der Waals solids (fullerenes, graphene, SWNTs) will allow some control over the solvation, and colloidal properties of the system.
Solvents will collide with solutes, thereby changing the energetics of the system. Often this causes temperature changes, which can aid the dipole, dielectric, miscibility, and vapor pressure properties of both the solvents and solute, to enhance solvation. Dispersive forces also become relevant as these are electrostatic in nature, resulting from random charge fluctuations, and not the permanent electrical charges often present in some molecules. Since the collective nature of the aromatic rings confers notoriously strong intermolecular forces between hydrocarbon/graphitic/aromatic species these properties become highly important for colloids and/or solutions.
Charge resonance stabilized charge distributions, resonance, and delocalization naturally impart aromatic molecules with high stabilities and high intermolecular forces. C60, graphene, and SWNT like molecules have short-range screening properties and long-range anti-screening properties due to their dipole and electron confined structures (1-dimensional or 2-dimensional respectively). At very short distances the Coulomb interactions can be screened while at larger distances they are anti-screened. Such behavior induces polarization and increased repulsion between two charges. It is therefore the distance of the solvents coupled with the similar intermolecular forces and desired vapor pressure, which is important, not position. This optimal distance is what determines the attraction or repulsion of some solvents and molecules.
The solubility values for both the fullerenes, graphene, and fullerene-polymers (i.e. SWNTs), are also based on the number conjugated carbon bonds present, and available contact area. The hydrophobic nature of these molecules, intermolecular forces, density, vapor pressure, and their short versus long-range nature, coupled with density changes, can enhance repulsion or attraction. If the close approach distance is not optimal then repulsion is favored. However, at some optimal distances, if the intermolecular forces are similar and the vapor pressures of the solvent favor the nucleation of the vapor phase. Cavities within the ASA and bubbles will ensue, which favor cavitation processes due to bridging forces, nucleation, and coalescence of cavitation bubbles. This allows for the solvent properties to exceed the long-range van der Waals forces of the solute molecules rendering solvation. Under increased temperatures and cavitation then the solvation of the fullerene, SWNTs, and graphene molecules is favored.
Still in other cases the conjugated electronic structures of the solvent molecules allows for a high intermolecular interaction. The molecular packing of the solvents and the dense modes of the fullerene, SWNT, graphene crystal lattices allows for solvation with some aromatic hydrocarbons and cyclic terpenes, lactones, fatty acid alcohols. Solvation occurs in molecules that have conjugated or high intermolecular interactions, which allow for unique electron-donor packing configurations. The degree and number of C═C conjugated bonds ASA, and intermolecular interactions, allow for greater molecular packing, and controls the solubility values for both the fullerenes, graphene, and fullerene-polymers (i.e. SWNTs). This is why full solvation of cyclic terpenes, terpene alcohols, fatty acid alcohols, lactones, cyclic triterpenoid saponins, and cyclic triterpenoid steroidal saponins, and fullerenes, graphene, and fullerene polymers (i.e. SWNTs) is noted following ultrasonication, and ultracentrifugation processing. In other cases supersaturation values of the fullerenes, graphene, and fullerene polymers (i.e. SWNTs) yields colloidal solutions, which also allow for optical and mass spectrometry characterization.