Nanoparticles, nanosponges, methods of synthesis, and methods of use

Abstract

We disclose novel metallic nanoparticles coated with a thin protective carbon shell, and three-dimensional nano-metallic sponges; methods of preparation of the nanoparticles; and uses for these novel materials, including wood preservation, strengthening of polymer and fiber/polymer building materials, and catalysis.

Claims

1. A method for making metallic-core carbon-shell nanoparticles, said method comprising the steps of: (a) impregnating biological fibers with a solution of metal ions in an aqueous or non-aqueous solvent; (b) removing the solvent, while leaving at least some of the metal ions impregnated in the fibers; and (c) heating the metal-ion-impregnated fibers in an inert atmosphere or in a vacuum to a temperature that carbonizes at least some of the fibers, that does not vaporize most of the carbon, that reduces at least some of the metal ions to metal particles in a zero oxidation state, and that causes a carbon shell to form around and to completely enclose most of the zero-oxidation-state metal particles; wherein no reducing agent is present during the reduction step, other than said biological fibers themselves; and wherein the reduction of the metal ions to metal particles in a zero oxidation state, and the formation of the carbon shell around the zero-oxidation state metal particles occur simultaneously.

2. A method as recited in claim 1, wherein the solution of metal ions comprises a metal salt, a metal hydroxide, metal ions complexed by inorganic ligands or metal ions complexed by organic ligands.

3. A method as recited in claim 1, wherein the biological fibers are selected from the group consisting of cellulose, hemi-cellulose, lignin, cotton, rayon, flax, linen, jute, ramie, sisal, hemp, milkweed, straw, bagasse, hardwood, softwood, lepidopteran silk, hair, wool, spider silk, sinew, and catgut.

4. A method as recited in claim 1, wherein the metal ions are selected from ions of the group consisting of Group IIA metals (Be, Mg, Ca, Sr, Ba, Ra); Group IIIA metals or semi-metals (B, Al, Ga, In, Tl); Group IVA metals or semimetals (Si, Ge, Sn, Pb); Group VA metals or semi-metals (As, Sb, Bi); Group VIA semi-metals (Te, Po); Group IIIB metals (Sc, Y, La, Ac); Group IVB metals (Ti, Zr, Hf): Group VB metals (V, Nb, Ta); Group VIB metals (Cr, Mo, W); Group VIIB metals (Mn, Tc, Re); Group VIII metals (Fe, Co, In, Ru, Rh, Pd, Os, Ir, Pt); Group IB metals (Cu, Ag, Au); Group IIB metals (Zn, Cd, Hg); Lanthanides (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu); and Actinides (Th, Pa, U, Np, Pu, Am).

5. A method as recited in claim 1, wherein the metal ions are selected from ions of the group consisting of Cu, Ag, In, and Gd.

6. A method as recited in claim 1, wherein the metal ions comprise copper ions.

7. A method as recited in claim 1, wherein said heating step occurs in a vacuum.

8. A method as recited in claim 1, wherein said heating step occurs in an inert atmosphere.

9. A method as recited in claim 8, wherein the inert atmosphere is nitrogen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A depicts an SEM image of a carbonized cotton fiber impregnated with Cu.

(2) FIG. 1B depicts a TEM image of Cu nanoparticles in the carbonized cotton fiber.

(3) FIG. 1C depicts a TEM image of a single Cu-core Carbon-shell nanoparticle.

(4) FIG. 1D depicts a nanoparticle as depicted in FIG. 1C at higher magnification.

(5) FIG. 1E depicts an electron diffraction pattern of a Cu-core carbon-shell nanoparticle.

(6) FIG. 1F depicts a higher magnification of a carbonized cotton fiber impregnated with Cu.

(7) FIG. 2A depicts a TEM image of Cu nanoparticles in carbonized rayon.

(8) FIG. 2B depicts a TEM image of Cu nanoparticles as depicted in FIG. 2A in carbonized rayon at higher magnification.

(9) FIG. 2C depicts a TEM image of Cu nanoparticles as depicted in FIG. 2B in carbonized rayon at higher magnification.

(10) FIG. 3A depicts a micrograph of the surface of cellulose.

(11) FIG. 3B depicts a micrograph of the pores in cellulose.

(12) FIG. 4A depicts a TEM image of Ag nanoparticles in carbonized cotton fiber.

(13) FIG. 4B depicts a TEM image of Ag nanoparticles in carbonized cotton fiber at higher magnification.

(14) FIG. 5A depicts the amount of Cu-core carbon-shell nanoparticles taken into pine branches immersed in a slurry of Cu nanoparticles.

(15) FIG. 5B depicts the amount of Cu-core carbon-shell nanoparticles taken into pine branches immersed in a slurry of Cu nanoparticles.

(16) FIG. 6 depicts a TEM image of Gd nanoparticles in carbonized cotton fiber.

(17) FIG. 7A depicts an SEM image of a Cu-Sponge.

(18) FIG. 7B depicts an SEM image of a Cu-Sponge at higher magnification.

(19) FIG. 7C depicts an SEM image of a Cu Sponge at higher magnification.

(20) FIG. 8A depicts an SEM image of a Ag-Sponge.

(21) FIG. 8B depicts an SEM image of a Ag-Sponge at higher magnification.

(22) FIG. 9 depicts a graph of concentration of Cu in leachate vs. leaching time for leaching of Cu-core carbon-shell nanoparticles from wood.

(23) FIG. 10 depicts weight loss of wood due to termites as a function of treatment.

(24) FIG. 11 depicts mortality of termites as a function of treatment.

(25) FIG. 12A depicts the loading of copper in samples tested for decay and leaching.

(26) FIG. 12B depicts the loading of copper in samples tested for termites.

(27) FIG. 13 depicts weight loss of wood due to T. versicolor (decay) as a function of treatment.

(28) FIG. 14 depicts weight loss of wood due to Irpex lacteus (decay) as a function of treatment.

MODES FOR CARRYING OUT THE INVENTION

(29) The general method for producing novel metal-core carbon-shell nanoparticles comprises soaking a natural fibrous material with a solution containing metal ions, removing the solvent, and then carbonizing the impregnated fibers at a temperature sufficient to generate metallic cores encased in carbon shells.

(30) In a prototype example, we used cotton fiber as template, which was soaked in a copper sulfate solution and then extra solvent was removed. Next, we carbonized the copper-impregnated cotton fiber by heating it to between about 200 C. and about 400 C., with a preferred temperature of about 350 C. Carbonization may be carried out between a few seconds and about 3 hours, with a preferred carbonization time of about 2 hours. Carbonization may be carried out in an inert atmosphere, for example under nitrogen, or in vacuum. Carbonization may also be conducted in other non-oxidizing gases such as He, Ne, Ar, Kr, or Xe. In addition, carbonization may be carried out in reducing atmospheres, for example H.sub.2, CH.sub.4, etc. While not preferred, carbonization also may be carried out in an atmosphere that contains limited amounts of oxygens or other oxidizing agents, if the amounts do not adversely affect the results. While not wishing to be bound by this theory, it appears that carbonization can transform oxygen into CO, which is reducing, or into CO.sub.2, which is non-oxidizing. The preferred atmosphere for carbonization is under nitrogen. The time and temperature for carbonization depend on metal ions and fibers used.

(31) Copper-core carbon-shell nanoparticles (CCCSNs) were formed during the carbonization processes without requiring further treatment. CCCSNPs appeared to be uniformly distributed throughout the carbon matrix generated during the carbonization. FIGS. 1A, 1B, 1C, 1D and 1F depict electron micrographs of fabricated copper-core carbon-shell nanoparticles made through the present invention. FIG. 1E depicts an x-ray diffraction pattern of a copper-core carbon-shell nanoparticle. FIG. 1A depicts an SEM image that shows the carbonized cotton fiber (carbon black) with many nanoparticles on its surface; FIG. 1B depicts a TEM image demonstrating that the nanoparticles were distributed throughout the carbonized cotton fiber. FIG. 1C depicts a copper core with a carbon shell surrounding it. As can be seen from FIGS. 1C and 1D, the copper core appeared to be about 50-60 nm in diameter, and the carbon shell appeared to be about 5 nm thick, respectively. FIG. 1C depicts a nanoparticle as depicted in FIG. 1D at lower magnification. FIG. 1E depicts electron diffraction pattern of Cu-core carbon-shell nanoparticle as depicted in FIG. 1C. This electron diffraction pattern indicated that the copper is in a Cu.sup.0 metallic state. FIG. 1F depicts a higher magnification of carbonized cotton fiber as depicted in FIG. 1B.

(32) This invention may be carried out using almost any metal that forms soluble ions in either aqueous or non-aqueous solvents, except that group IA metals (Li, Na, K, Rb, and Cs) may be too electropositive. Silver-core carbon-shell nanoparticles, nickel-core carbon-shell nanoparticles, and gadolinium-core carbon-shell nanoparticles have all been successfully made. FIGS. 4A and 4B show electron micrographs of Ag-core carbon-shell nanoparticles at different magnifications. FIG. 6 shows an SEM micrograph of the Gd core/shell prototype.

(33) Nickel-core carbon-shell nanoparticles were generated using the same method as described above for copper, using NiSO.sub.4 as the source of Ni, except the carbonization temperature was 380 C.

(34) Silver-core carbon-shell nanoparticles were generated using the same method as described above for copper, except silver nitrate was used as the source of silver, and the carbonization temperature was 180 C.

(35) Galladium-core carbon-shell nanoparticles were made using the same method as described for the Cu version except GdCl.sub.3 was used as the Gd source, and the carbonization temperature was 350 C.

(36) While not wishing to be bound by this theory, it appears that the carbonization temperature correlated roughly with the melting point of the metal.

(37) Cu-core carbon-shell materials have been successfully used to protect wood against decay.

(38) Gd-core carbon-shell materials may be used, for example, in NMR image enhancement, energy-efficient magnetic refrigeration, and data storage. Other lanthanum-group metals, including Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu also may be used to form MCCSN materials, and these materials also should be useful for similar purposes.

(39) Alternatively, the present invention may be used to make three-dimensional nano-metallic sponges. The process is generally similar to that for making the core/carbon shell nanoparticles, but the metal ion-impregnated natural fibers are heated to a higher temperature, to a point where carbon is vaporized, and the metal nanoparticles just start to sinter and connect to one another to form nano-sponge structures. The fiber skeleton acts as a frame/template to make tube-like nano-sponges, which have a far greater surface area/volume ratio than most prior nanoparticle structures. We have made three-dimensional nano-metallic structures, which exhibited high surface area, and which typically had particle sizes less than 10 m, and preferably less than 50 nm, and more preferably less than 10 nm, as estimated from SEM micrographs. The metal typically existed in a low oxidation state, and in a preferred embodiment, the metal was in a zero oxidation state. Pore sizes of the metallic sponges were typically less than 100 m, and preferably less than 100 nm, and more preferably less than 10 nm, as estimated from SEM micrographs. The sponges may exist without a carbon coating. The sponges may comprise a mixture of metals.

(40) Prototype nano-metallic sponges have been made by soaking natural fibers in a metal ion solution as previously described, followed by carbonizing the impregnated fibers at elevated temperature in an inert atmosphere (or under vacuum). A somewhat higher temperature is used to form nano-metallic sponges than the core/shell nanoparticles. We have found that for copper a preferred temperature for forming core/shell nanoparticles is about 350 C., and a preferred temperature for forming nano-metallic sponges is about 450 C. For silver, the corresponding temperatures are about 180 C. and about 280 C., respectively.

(41) FIGS. 7A, 7B, and 7C depict electron micrographs of Cu/C nano-metallic sponges at different magnifications; FIGS. 8A and 8B depict electron micrographs of Ag/C nano-metallic sponges at different magnifications. In both cases, note the tubular shapes, the high porosity walls, and the high surface areas. Nano-metallic sponges may be used in catalysis.

Example 1

(42) The surface of the cellulose fiber is rough (FIG. 3A) and contains pores of diameter of 30-70 nm (FIG. 3B). These nanopores may allow reactant molecules to penetrate into inner cavities. When cellulose fibers were immersed in aqueous CuSO.sub.4, copper ions were readily impregnated into the cellulose fibers through the pores. Though not wishing to be bound by this theory, most of the incorporated Cu.sup.++ ions appeared to be bound to cellulose macromolecules, probably via electrostatic (e.g., ion-dipole) interactions, with the electron-rich oxygen atoms of polar hydroxyl and ether groups of cellulose.

Example 2

(43) Cotton fiber was soaked in a copper sulfate solution. After the cotton was saturated, then extra solvent was removed. Carbonization was carried out at about 350 C. under nitrogen for about two hours. The copper nanoparticles and the encapsulating carbon shells appeared to have been formed simultaneously during carbonization. As fabricated, the CCCSNPs were uniformly distributed throughout the carbon based matrixes. FIGS. 1A, 1B, 1C, 1D, and 1F depict micrographs of fabricated copper-carbon core-shell nanoparticles made through the present invention. FIG. 1A depicts an SEM image that shows the carbonized cotton fiber (carbon black) with many nanoparticles located on its surface; FIG. 1F depicts a higher magnification of that depicted in FIG. 1A. FIG. 1B depicts a TEM image demonstrating that the nanoparticles formed through the entire carbonized cotton fiber; FIGS. 1C and 1D depict TEM micrographs of a nanoparticle encased in a carbon shell. These micrographs show a core of about 50-60 nm in diameter and a carbon shell of about 5 nm. FIG. 1E depicts an x-ray diffraction pattern for nanoparticle depicted in FIGS. 1C and 1D. This pattern confirms that the copper remained as Cu.sup.0.

Example 3

(44) The total copper concentration in the material made according to Example 2 was measured to be about 25 Wt %. It was clear from the TEM micrograph (See FIG. 1B) that the particles had generally spherical shapes, and that a majority of them appeared to have an average diameter value about 20-50 nm, although some particles were as small as one or two nanometers in diameter.

(45) After the carbonized material was pulverized into micrometer to sub-micrometer sized particles, it was uniformly dispersed into both polar and non-polar solvent, for example water, aqueous acids, aqueous bases, salt solutions and cooking oil. After being immersed in water at ambient environment over three months, the nanoparticles still retained a reduced copper core structure with no sign of deterioration. The powder, characterized by FTIR, also showed that the shells of the CCCSN particles retained a number of organic functional groups. This property will be useful in functionalizing the carbon layer.

Example 4

(46) Cotton fiber was soaked in a AgNO.sub.3 solution. After the cotton was saturated, then extra solvent was removed. Carbonization was carried out at about 180 C. in nitrogen for about two hours. FIGS. 4A and 4B depict electron micrographs of the carbon-encased silver nanoparticles, at different magnifications.

Example 5

(47) Cotton fiber was soaked in a NiSO.sub.4 solution. After the cotton was saturated, then extra solvent was removed. Carbonization was carried out at about 380 C. in nitrogen for about two hours. The resulting nanoparticles contained carbon encased Ni, but the nanoparticles were difficult to distinguish with electron microscopy.

Example 6

(48) Cotton fiber was soaked in a GdCl.sub.3 solution. After the cotton was saturated, then extra solvent was removed. Carbonization was carried out at about 350 C. in nitrogen for about two hours. FIG. 6 depicts a micrograph of Gadolinium encased nanoparticles.

Example 7

(49) The processes described in Examples 2, 4, and 6 were repeated using rayon fibers, wood fibers and cotton paper. All other reagents and conditions were the same. FIGS. 2A, 2B and 2C depict a micrograph of Cu in rayon.

Example 8

(50) The process described in Examples 2, 4, and 6 have been used to make nanoparticles from a solution containing multiple metals, for example Cu and Ag. It appears that a CuAg mixture was formed.

Using Copper Based Preservatives for Wood Protection

Example 9

(51) The novel nanoparticles may be introduced into wood in the same general manner as other wood preservatives, e.g., pressure treatment. It is believed that this is the first report of using carbon-coated copper nanoparticles in the treatment of wood to protect against insects, mold, or decay.

(52) There are several advantages to using CCCSNPs as wood preservatives. The cellulose source may be derived from bio-based renewable raw materials. Smaller amounts of Cu ions will be released in the environment due to the carbon encapsulation and lower metal loading. The material may be made at a competitive cost. The product is dispersible in both water and oil. The novel form of copper is compatible with existing wood treating processes in industry.

Example 10

(53) Copper is toxic to marine life, particularly in the +1 or +2 oxidation state. One of the advantages of CCCSNP powder is that the encased copper will remain as metallic copper. We tested the stability of the CCCSNP by immersing the particles in a variety of solvents as listed in Table 1.

(54) TABLE-US-00001 TABLE 1 Experimental design for chemical stability tests in designated solvents No. of Solvent Condition Tests 1. water (pH = 7) and (pH = 2) 1, 5, 10, 20, 30, 40, 50, 60, 90 days 36 (t = 25 C. & 40 C.) 2.3% wt NaCl (pH = 7) and 1, 5, 10, 20, 30, 40, 50, 60, 90 days 36 (pH = 2) (t = 25 C. & 40 C.) 3. Hexane 1, 5, 10, 20, 30, 40, 50, 60, 90 days 18 (t = 25 C. & 40 C.) Total Number of tests 90

(55) For all conditions tested (Table 1), we found that the copper remained stable as metallic copper, Cu.sup.0.

Example 11

(56) A suspension of 1% CCCSNP in water was used to treat wood samples using a standard vacuum and pressure treatment, otherwise similar to that commonly used in wood treatment plants. The treated samples were subsequently challenged with Formosan subterranean termites (Coptotermes formosanus Shiraki) using the AWPA El-jar test standard. The results showed that the novel materials greatly inhibited termite attacks on the treated samples.

Example 12

(57) CCCSNP was combined with other biocides to form various preservative systems to deal with both copper-resistant and non-copper resistant fungi. Such co-biocides may include, for example, quat, tebuconazole (C.sub.16H.sub.22ClN.sub.3O), RH287, and others known in the art. Tebuconazole and RH287 were formulated into emulsions to mix with the CCCSNP.

Example 13

(58) Commercial #2 grade 24 lumber from southern pine (Pinus spp.) and western spruce (Pica spp.) were cut into 48-inch long samples. The ends of each sample were coated with a commercial lumber sealer such as ANCHORSEAL by UC Coatings Corporation a lumber end paint type by Cloverdale Paint. The samples were pressure-treated based as shown below in Table 2.

(59) TABLE-US-00002 TABLE 2 Experimental design on pressure-treatments with CCCSN solution Variable Condition Treatments 1. Wood Species Southern Pine and Western 2 Spruce 2. Treatment Pressure (PSI) 120 and 160 2 3. CCCSN-Based systems Quat, Azole, and RH287 3 4. Concentration (wt %) 0 (control), 1, 2, and 5% 4 5. Treating Process 30-minute vacuum at 30-inch 1 Hg and 60-minute pressurizing at target pressure level Total Number of Treatments 48

(60) A Twin-X x-ray preservative analyzer (Model 54-C-TX01Oxford Instruments Analytical Ltd.) was used to analyze copper loading in CCCSNP powder and in treated lumber. For treated lumber, small thin wood slices, taken from various depths for each treated panel, were examined. The samples were ground into powder (40-mesh) and analyzed for copper. CCCSNP powder distribution and the copper penetration profile as the function of treatment conditions and wood morphology were determined by environment scanning electron microscopy (ESEM) with X-ray microanalysis. Micro-distribution of copper was also determined using scanning electron microscopy (SEM) with X-ray microanalysis. X-ray surface mapping and line scan provided the distribution surface elements as well as morphology information. X-ray image-chemical analyzer (EDAX) analysis showed copper within the wood; however, detail analysis will require higher Cu loadings in the wood. Micro-distribution of the copper within the wood, especially along the board thickness will be determined in the future.

Example 14

Leaching Tests

(61) Water leaching experiments were conducted according to AWPA leaching standard E11-97 [AWPA 2001c]. CCCSNP treated wood samples (19.0-mm cubes) were compared to Alkaline Copper Quaternary (ACQ)-treated samples. The samples were subjected to AWPA leaching procedures over a total 14 day period. Leachate was removed at designated intervals. The total copper content in the leachate was analyzed as a function of time by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The method has a detection limit of about 0.1 mg/l, which is generally reproducible within 8% for all analytes. The percent of copper leached is shown in Table 3 below and in FIG. 9. Group B, D, E, and H are described in Table 4. As can be seen the CCCSNPs were retained in the wood substantially better than the standard copper formulation, ACQ.

(62) TABLE-US-00003 TABLE 3 Copper concentration in the leachate as a function of leaching time measured ICP technique. Copper Concentration (ppm) Time Control, Untreated B (Hours) ACQ Wood group D-group E-group H-group 6 23.28 0.016 17.51 6.37 22.00 23.72 30 27.34 0.005 7.02 3.06 14.94 13.79 78 18.91 0.011 1.52 0.92 3.99 3.42 126 11.23 0.006 0.79 0.45 2.28 0.79 174 9.77 0.003 0.59 0.37 0.48 0.27 222 7.38 0.003 0.27 0.22 0.19 0.14 270 4.22 0.01 0.31 0.19 0.16 0.42 318 5.67 0.00 0.24 0.12 0.11 0.04 366 6.31 0.01 0.22 0.11 0.10 0.06

Example 15

Termite Resistance Tests

(63) Five matched samples for each treatment condition, five ACQ treated samples and five untreated southern pine controls, were used in No-Choice Laboratory Termite Tests according to a modified AWPA standard El-97 [AWPA 2001a]. FIG. 12B depicts the loadings of copper for the termite tests. Prior to each test, the blocks were oven-dried at 105 C. for 24 hours, and sample weight (W.sub.1) and dimensions were measured. Each test bottle (80 mm diameter100 mm height) was autoclaved for 30 minutes at 105 kPa and dried. Autoclaved sand (150 g) and distilled water (30 mL) were added to each bottle. Finally, four hundred termites (360 workers and 40 soldiers) were added to opposite sides of the test block in the container. All containers were maintained at room temperature for 4 weeks. The bottle cap was placed loosely. After testing, each bottle was dismantled. Live termites were counted, and test blocks were removed and cleaned. Each block was oven-dried again at 105 C. for 24 hours to determine the dry sample weight (W.sub.2). From the measurements, sample weight loss [(W.sub.1W.sub.2)/W.sub.1] and termite mortalities were determined. The tested samples were ranked visually by five people on a scale of 1-10, with 10 as no damage and 1 as complete destruction. Table 4 below shows the results of this test. In the table both percent mortality and weight loss are given as well as a statistical ranking based on the Ducan protocol. Groups with different letters, for example A or B, indicate that the value in the table associated with one letter is statistically different from the value in the table associated with another letter. A group with two letters, for example CD, indicates the value in the table cannot be distinguished from either of the groups with those letters. For example CD could not be distinguished from a group designated C or from a group designated D. By both weight loss and termite mortality it was clear that CCCSNP is effective against termites. FIG. 10 depicts the loss of wood as a function of treatment. FIG. 11 depicts termite mortality as a function of treatment.

(64) TABLE-US-00004 TABLE 4 Summary of Termite Test Results Copper loading Mortality Sample Weight Damage rate Rate Loss Rating Group (kg/m.sup.3) (%) (%) (0-10) Group A 0.50 32.50% BC 8.75% B 6.5 B Group B 0.74 42.30% C 2.80% A 8.3 CD Group C 0.41 38.40% BC 2.25% A 8.4 CD Group D 0.51 34.90% BC 1.90% A 8.8 D Group E 0.62 22.20% AB 11.33% B 6.4 B Group F 0.73 25.85% BC 3.35% A 8.3 CD Group G 0.48 30.05% BC 4.07% A 7.8 C Group H 0.65 33.71% BC 4.33% A 8.1 CD ACQ Control 3.67 21.89% AB 2.05% A 9.9 E Wood Control 0.01 9.04% A 32.09% C 1.0 A
Note that at a Cu loading for the ACQ control was about five to nine times the Cu loading for the Cu-core carbon-shell nanoparticles, while the effectiveness for termite control was about the same or better for the CCCSNP-impregnated wood at a far lower loading of copper.

Example 16

Flake Preparation

(65) Commercial dry southern pine and mixed hardwood flakes were obtained. Part of the flakes were sprayed with an CCCSNP-based mixture (also including quat, tebuconazole, and RH287, based on solid wood tests) to achieve target copper loading levels around 0.25 and 0.45 wt %. The mixed flakes were used for making a composite wood product with incorporated CCCSNP.

(66) Panel Manufacture.

(67) Experimental panels were manufactured using treated and control flakes according to the following conditions:

(68) TABLE-US-00005 TABLE 5 Experimental design for strand board manufacturing with CCCSN-treated flakes. Variable Condition Treatments 1. Wood Species Southern Pine and mixed hardwoods 2 2. Panel Density (g/cm.sup.3) 0.70 1 3. Copper loading 0.25 wt %, 0.45 wt % 2 4. Resin Content (%) 4.5% of dry wood weight 1 5. Panel Size 24 24 0.5-inch 1 6. Panel Structure Single-layer random-formed 1 7. Replication Three each 3 Total Number of Treatments 12

(69) The flakes and panels described above will be made. For each condition, the target amount of wood, resin, CCCSNP, and wax (used as a binder) will be weighed and mixed in a blender. Liquid resin and wax will be forced through two separate air-assisted nozzles, causing fine droplets to be sprayed into the blender with wood flakes. The CCCSNP powder will be added by a third air-assisted nozzle at about 40 PSI pressure. These conditions are similar to those used in a conventional process for loading zinc borate into wood. The blended wood flakes will then be removed and formed into mats. The mats will be hot-pressed into panels (1 minute closing and 5 minutes curing) using a 200-ton hot press. It is expected that such panels will be resistance to termites, mold and decay.

Example 17

(70) As shown in Table 6, selected weights of CCCSNP were mixed with 1000 ml of water. Wood samples were placed in a 2000 ml plastic container, which were evacuated to about 27 mm-Hg for 30 minutes. The treating slurries were then introduced into the containers. The assembly, comprising wood and treating slurry, was then pressurized to 130 PSI (0.9 MPa) for about 60 minutes. After pressure was released, samples were removed, and then dried at about 80 C. to a constant weight. The treated samples were stored in plastic bags for subsequent testing.

(71) TABLE-US-00006 TABLE 6 Formulation of the treating solution with 1000 ml water. Amount of Amount of Amount of Group CCCSNP Quaternary EDTA Group A 10 g 0 g 0 g Group B 20 g 0 g 0 g Group C 10 g 6 g 0 g Group D 20 g 6 g 0 g Group E 20 g 0 g 15 g Group F 20 g 6 g 15 g Group G 10 g 6 g 0 g Group H Mixture of Groups A-G

Example 18

(72) CCCSNP-treated wood samples (19 mm cubes) prepared as described in Example 17 were tested for resistance to decay/leaching. These results were compared with commercial ACQ-treated wood samples of the same size. Three random samples were selected from each group. Samples were hammer-milled to 20-mesh. The powder was then digested in a sulfuric acid (42.5 ml)-water (200 ml) solution for three days. The digested solution was then filtered and diluted to 500 ml with water and analyzed for Cu content by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The copper concentration (kg/m.sup.3) was calculated for each group based on measured sample volume and total copper content. FIG. 12A depicts the loading of copper for several of the samples.

Example 19

(73) The decay resistance of CCCSNP-treated wood samples was tested according to AWPA standard E10-01 [AWPA 2001b]. White fungi, Trametes versicolor or Irpex lacteus, were used in the test. The culture media were sterilized at 105 kPa for 30 minutes at 105 C. and cooled before inoculation. 100 g of silt loam screened through a No. 6 sieve were placed in each bottle, which was loosely capped and autoclaved twice at 105 kPa for 30 minutes at 105 C. After the bottles cooled, untreated southern pine wood feeder strips were placed on top of the soil in each bottle. Each feeder strip was then inoculated at diagonally opposite corners. Each inoculated bottle was be incubated at 25 C. and 75% humidity until the feeder strip was heavily colonized by test fungus. The test blocks were then placed on the surface of a feeder strip colonized with fungus, one in each bottle. The testing time for both white rot fungi was 16 weeks. After the test, the test blocks were removed, cleaned, and oven-dried. Sample weight loss was calculated and analyzed. FIGS. 13 and 14 show the results of these tests. FIG. 13 depicts weight loss due to decay from Trametes versicolor. FIG. 14 depicts weight loss from decay due to Irpex lacteus. Clearly the CCCSNPs are effective against these decays. Further, as can be seen from FIG. 12A, the copper loading for the AQC standard sample is 5-10 times that of the CCCSNPs. Thus, on a per weight basis the CCCSNPs are more effective than the commercial standard.

Example 20

Wood/Natural Fiber-Polymer Composites (WNFPC)

(74) Melt-blending and compression molding methods were used to manufacture the Wood/Natural Fiber-Polymer Composites (WNFPC) with CCCSNP additive. During melt-blending, high density poly-ethylene (HDPE) pellets were loaded into a Haake Rheomix 600 blender set at 165 C. and 60 RPM blender speed. After HDPE melting, CCCSNPs were added to the melt. In one embodiment wood fiber (40-mesh particle size) was added to the mix. In another embodiment bagasse fiber was added to the mix. A mixing period of 10 minutes was used to mix all components completely (i.e., the mixing torque reached stable conditions). The blend was cooled and removed from the blender.

(75) The blends with various compositions were then used to make impact and tensile/dynamic mechanical analysis (DMA) test panels (4- and 1-mm thick, respectively) using compression molding. For each sample, the molding set was pressed at 175 C. and 30-ton compression force for 5 minutes, and then cooled to room temperature while maintaining the pressure. The target density was 1.0 g/cm.sup.3. The test panels were conditioned prior to cutting of test samples. Test samples were machined and tested for tensile strength, impact strength, and dynamic modulus. See Table 7. These data show the ease with which the CCCSNPs may be included during fabrication of composites. Further, the composites containing CCCSNPs showed improved impact strength and tensile strength as compared to control composites, while dynamic modulus appears to be about the same as the control for most formulations tested. These composites are expected to be resistant against termites and decay just as impregnated wood was.

(76) TABLE-US-00007 TABLE 7 Summary of test data on wood/natural fiber polymer composites Composition Dynamic Tensile Impact Formulation Wood Bagasse Modulus Strength Strength Number HDPE Fiber Fiber CCCSNP (MPa) (MPa) (KJ/m.sup.2) 01 100% 0% 0% 0% 1543 27.37 3.96 02 98.5% 0% 0% 1.5% 1545 29.31 4.57 03 70.0% 0% 30% 0% 2348 23.22 3.74 04 68.5% 0% 30% 1.5% 2875 30.37 4.98 05 70.0% 30% 0% 0% 2474 19.97 3.02 06 68.5% 30% 0% 1.5% 2183 20.35 3.37

Example 21

Application to Trees

(77) Four freshly cut pine branches, about 0.5 inches in diameter, were placed in glass tubes with one branch per tube. The tubes contained CCCSNP slurries at weight percentages of 0.0%, 0.5%, 1%, and 2%. The branches were kept in these tubes for about 10 days, after which they were removed and sacrificed. The wood was examined with ICP. FIG. 5A depict the concentration of Cu in the tree branch as a function of distance from the bottom of the branch. Data from the branch inserted in the 2% slurry showed a concentration of about 25 ppm Cu at about 2 inches from the bottom. The Cu concentration decreased as a function of distance from the base, and was detected at about 5 ppm at about 12 inches from the base.

Example 22

(78) Two rose bushes were planted in standard nursery soil. One was watered with 1.5% slurry of CCCNSP, and the other bush was watered with pure water. After about three weeks we sacrificed the plants and determined the copper content as a function of distance from the trunk bottom using ICP. The first approximate 2 inch of the plant was in the soil. FIG. 5B depicts the concentration of Cu in the rose bush stem as a function of distance from the bottom of the plant. A peak in Cu concentration occurred at about 6 from the tree bottom. The concentration of Cu at its maximum was about 4.3 ppm.

Example 23

(79) Different fibers (cotton, wood, bagasse, etc.) will be used to generate core-shell nanoparticles. As-harvested fibers will be compared to pre-treated (de-greased) fibers in terms of the resulting core-shell structure, particle size distribution, and particle density within the fiber, to determine whether the benefits of de-greasing justify the costs for use in the novel process.

Example 24

(80) For some uses it will be useful to separate and collect the core-shell nanoparticles from the carbon matrix. For other uses, such as wood preservation, separation may not be necessary. In wood preservation, retaining the carbon matrix may actually be beneficial, both to better absorb other compounds that may also be helpful in wood protection, and also to help disperse the nanoparticles more uniformly through the wood structure. The carbon matrix comprises the black carbon residue compounds from the carbonized fibers. The carbon shell comprises the carbon layer(s) that are closely bonded to a metal nanoparticle core, typically with a thickness of a few nanometers. We have seen in TEM observations that the carbon shell on the copper nanoparticle surface has a different microstructure from carbon in the matrix. The FTIR results showed that there were substantial quantities of carbohydrate molecules in the carbon matrix but not in the shells. These differences may be exploited to separate core/shell nanoparticles from the matrix by chemical means, physical means, or both.

(81) Separation methods include: (1) pulverizing the carbonized fibers with embedded nanoparticles to a fine powder, and screening the resulting powder from 100 m to sub-m to determine an optimal screen size for separation; in general, it is expected that finer powders and finer screens will yield better results, but may take more effort; (2) mixing the powder with an organic solvent such as acetone, so that the core/carbon shell nanoparticles start to separate from the carbon matrix, with stirring if needed. Preferably, the density and viscosity of the solvent are such that the carbon matrix with remain suspended, while the metal core nanoparticles will settle; (3) using ultrasonic, magnetic, centrifuge, or mechanical stirring will increase the separation speed and reduce the time needed for separation. Because acoustically cavitated bubbles produce high pressures, high pressure gradients, and fluid motion, this technique also may accelerate the separation processes; (4) separation may also be accomplished by applying a vacuum over a suspension containing a mixture of nanoparticles and carbon. Nanoparticles are expected to be pulled into the vacuum and collected directly with an air filter system. The carbon matrix phase will be examined by Energy Dispersive Spectroscopy (EDS) X-Ray Microanalysis and TEM to determine quantitative separation ratios and size effects on separation, respectively.

Example 25

Mold Tests

(82) Mold testing will also be conducted following the testing procedures in AWPA Standard Method of Evaluating the Resistance of Wood Product Surfaces to Mold Growth. Molds and their spores will include: Aureobasidium pullulans (d. By.) Arnaud ATCC 9348; Aspergillus niger v. Tiegh. ATCC 6275; Penicillium citrinum Thom ATCC 9849; and Alternaria tenuissima group (Kunze) Wiltshire Ftk 691B. The collected inocula will be dispersed in distilled water and distributed on potting soil in the mold chambers. The mold chambers will be left in warm humid conditions for more than two weeks prior to placing in the samples. The temperatures and humidity of the room will be periodically checked. The mold chamber will be kept at 25 C. and 100% humidity. Samples will be rated every 2 weeks for a total of 5 rating periods following the rating system in the AWPA proposed standard.

Definition

(83) As used in the specification and claims, unless context clearly indicates otherwise, a biological fiber means a native plant fiber, a native animal fiber, a chemicallyor physicallymodified plant fiber, or a chemicallyor physicallymodified animal fiber. If the native fiber is chemically or physically modified, then its structure should retain sites that are effective as centers for promoting the formation of metallic core-carbon shell nanoparticles. The term biological fiber does not include synthetic fibers, regardless of composition or chemical or structural similarity, that are not derived from native plant fibers or native animal fibers. Examples of fibers that are not considered biological fibers include the various synthetic nylons and polyesters.

(84) The complete disclosures of all references cited in this specification are hereby incorporated by reference. In the event of an otherwise irreconcilable conflict, however, the present specification shall control.