Method for the synthesis of nanoparticles of heterometallic nanocomposite materials

Abstract

A simple one pot sol-gel method for the synthesis of bi-metal nanostructures is based on non-noble metals (Fe, Co and Sn) and titanium. The method involves the synthesis of mixed metal nanoscale composites using low cost precursors which allow for the synthesis of desired nanocomposite materials with self-scarifying titanium or silica supports. The procedure does not require any surfactant or any need for pH controlled step. Applicants' method involves the in-situ generation of precursors and their simultaneous entrapment in a gel. This simple one pot synthesis allows for the synthesis of homogenous size, shape and distribution of targeted nanostructures. Further, this method can be applied for the preparation of various nanocomposite materials using different choices of metals and self-scarifying supports. Applicants also show that Pd, the noble metal based nanocomposite is feasible.

Claims

1. A sol-gel method for synthesizing nanoparticles of heterometallic nanocomposite materials, the method comprising: preparing a reaction solution comprising a first mass of tetrahydrofuran (THF), a second smaller mass of trifilic acid (TFC), a metallic precursor M(X).sub.n, wherein M is a metal selected from the group consisting of Fe, Sn, Ni, Mn, Co, Pb, Pt, Pd, and mixtures thereof, and further wherein X is selected from the group consisting of halides and organic ligands, and a titanium precursor, a silicon precursor, or a mixture thereof; exposing the reaction solution to reaction conditions sufficient to induce polymerization of the THF; maintaining the reaction conditions for a reaction time sufficient to allow the reaction solution to form a gel; heating the gel to a calcination temperature; and maintaining the gel at the calcination temperature for a calcination period sufficient to obtain M.sub.xTi.sub.yO.sub.z.TiO.sub.2 nanocomposites, M.sub.xTi.sub.yO.sub.z.SiO.sub.2 nanocomposites, or mixtures thereof.

2. The method for synthesizing nanoparticles of heterometallic nanocomposite materials according to claim 1, wherein: the metallic precursor is ferrocene (Fe(C.sub.5H.sub.5).sub.2) and the titanium precursor is titanium isopropoxide; the reaction solution is stirred for the reaction period of 2 hours to form the gel; the gel is heated to the calcination temperature of 500 C. at a temperature ramp rate of of 4 C. per minute and held at the calcination temperature for a calcination period of 2 hours to form an iron-containing nanocomposite product iron titanite at titania (Fe.sub.xTi.sub.yO.sub.z.TiO.sub.2).

3. The method for synthesizing nanoparticles of heterometallic nanocomposite materials according to claim 1, wherein: the metallic precursor is palladium(II) nitrate hydrate Pd(NO.sub.3).sub.2.xH.sub.2O and the titanium precursor is Ti isopropoxide; the gel is heated to the calcination temperature of 450 C. at a temperature ramp rate of 4 C. per minute; and maintained at the calcination temperature for a calcination period of 2 hours to produce a palladium-containing nanocomposite product palladium titanate at titania (Ti.sub.4Pd.sub.2O.TiO.sub.2).

4. The method for synthesizing nanoparticles of heterometallic nanocomposite materials according to claim 1, wherein: the metallic precursor is tin chloride (SnCl.sub.2) and the titanium precursor is Ti isopropoxide; the reaction solution is stirred for the reaction period of 2 hours to form the gel; the gel is is heated to the calcination temperature of 400 C. at a temperature ramp rate of 3 C. per minute; and held at the calcination temperature 400 C. for a calcination period of 2 hours to produce a tin-containing nanocomposite product (Sn.sub.0.39Ti.sub.0.61O.sub.2.TiO.sub.2).

5. The method for synthesizing nanoparticles of heterometallic nanocomposite materials according to claim 1, wherein: the metallic precursor is cobalt acetyalacetonate and the titanium precursor is Ti isopropoxide; the reaction solution is stirred for the reaction period of after 2 hours to form the gel; and the gel is heated to the calcination temperature of 500 C. and held at the calcination temperature for a calcination period of 2 hours to obtain a cobalt containing nanocomposite product (CoTiO.sub.3.TiO.sub.2).

6. The method for synthesizing nanoparticles of heterometallic nanocomposite materials according to claim 1, wherein: the metallic precursor is ferrocene (Fe(C.sub.5H.sub.5).sub.2) and the titanium precursor is titanium isopropoxide; the reaction solution is stirred for the reaction time of 2 hours to form the gel; the gel is heated to the calcination temperature of 500 C. at a temperature ramp rate of 4 C. per minute; and the gel is maintained at the calcination temperature for a calcination period of 4 hours to obtain an iron-containing nanocomposite product iron titanium oxide at titania (Fe.sub.1.696Ti.sub.0.228O.sub.3.TiO.sub.2).

7. The method for synthesizing nanoparticles of heterometallic nanocomposite materials according to claim 1, wherein: the metallic precursor includes both nickel acetylacetonate and ferrocene and the titanium precursor is titanium dioxide; the reaction solution is stirred for the reaction period of 2 hours to form the gel; the gel is heated to the calcination temperature of 500 C. at a temperature ramp rate of 3 C. per minute; and maintained at the calcination temperature for a calcination period of 3 hours to obtain a nickel and iron-containing nanocomposite product Trevorite at titania (Ni.sub.1.43Fe.sub.1.7O.sub.4.TiO.sub.2).

8. The method for synthesizing nanoparticles of heterometallic nanocomposite materials according to claim 1, wherein: the metallic precursor is ferrocene and the titanium precursor is titanium isopropoxide; the reaction solution further comprising a silicon precursor, mesoporous silica (SiO.sub.2); the gel is heated to the calcination temperature of 450 C. at a temperature ramp rate of 4 C. per minute; and held at at the calcination temperature for a calcination period of 2 hours to obtain an iron-containing nanocomposite product iron titanite at silica (Fe.sub.xTi.sub.yO.sub.z.SiO.sub.2).

9. A sol-gel method for synthesizing heterometallic nanoparticles, the method comprising: preparing a reaction solution comprising a first mass of tetrahydrofuran (THF), a second smaller mass of trifilic acid (TFC), and a first metallic precursor M1(X).sub.n, wherein M1 is a metal selected from the group consisting of Fe, Sn, Ni, Mn, Co, Pb, Pt, Pd, and mixtures thereof, and further wherein X is selected from the group consisting of halides and organic ligands, a second metallic precursor M2(X).sub.n, wherein M2 is a metal selected from the group consisting of Fe, Sn, Ni, Mn, Co, Pb, Pt, Pd, and mixtures thereof, wherein M2 is different than M1, and further wherein X is selected from the group consisting of halides and organic ligands, and exposing the reaction solution to reaction conditions sufficient to induce polymerization of the THF; maintaining the reaction conditions for a reaction time sufficient to allow the reaction solution to form a gel; heating the gel to a calcination temperature; and maintaining the gel at the calcination temperature for a calcination period sufficient to obtain M1.sub.xM2.sub.yO.sub.z nanoparticles.

10. The method for synthesizing heterometallic according to claim 9, wherein: the first metallic precursor is nickel acetylacetonate; the second metallic precursor is ferrocene; and the resulting nanoparticles are Ni.sub.xFe.sub.yO.sub.z.

11. The method for synthesizing heterometallic nanoparticles according to claim 9, wherein: the first metallic precursor is manganese acetate and the second metallic precursor is ferrocene; the reaction solution was sonicated for 10 minutes and then stirred for a reaction time of 2 hours to form the gel; the gel was then heated to the calcination temperature of 500 C. at a temperature ramp rate of 4 C. per minute; the gel was held at the calcination temperature for a calcination period of 2 hours to obtain a manganese and iron containing product ((Mn.sub.xFe.sub.y)O.sub.z).

Description

DESCRIPTION OF THE DRAWINGS

(1) The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

(2) FIG. 1, metal compounds, as precursors of metal composite materials were added in tetrahydrofuran (THF) and polymerization of THF was initiated by the addition of a small quantity of trifilic acid (TFC) as shown in FIG. 1. No other oxidizing, reducing agent or any surfactant was required. Slow polymerization of THF was allowed out at room temperature. Once gel was formed by reaction, the mixture was transferred into crucibles and crucibles transferred into a furnace. The temperature was then raised to 500 C. at a rate of 4 C. per minute and held at that temperature for 2 hours.

(3) ##STR00002##
Wherein M=Fe, Sn, Co, Pb or any other metal, X=halide, or any organic ligand such as acetylacetonate and pentadienyl. Similarly, Metal-Silicon nanocomposites were prepared;

(4) FIG. 2A illustrates the XRD patterns of the various nanocomposites calcined at 500 C. for 2 hours;

(5) FIG. 2B illustrates SEM micrographs of Fe.sub.9TiO.sub.15.TiO.sub.2 nanocomposite showing highly porous architecture;

(6) FIG. 3A illustrates an elemental mapping;

(7) FIG. 3B illustrates an EDS spectrum of Fe.sub.9TiO.sub.15.TiO.sub.2;

(8) FIG. 4A illustrates the elemental mapping;

(9) FIG. 4B illustrates an EDS spectrum of Ti.sub.4Pd.sub.2O.TiO.sub.2 nanocomposite;

(10) FIG. 5 illustrates HRTEM images of Fe.sub.9TiO.sub.15.TiO.sub.2 nanocomposite;

(11) FIG. 6 illustrates HRTEM images of Ti.sub.4Pd.sub.2O.TiO.sub.2 nanocomposite;

(12) FIG. 7 illustrates Fe-catalysed reduction of nitroarenes to anilines: Reaction conditions: 0.5 mmol nitroarene, 5-7 mg catalysts, 2.5 mmol hydrazine hydrate, 2 mL THF, 15-20 h, 100 C. Yields we determined using n-hexadecane standard; and

(13) FIG. 8 illustrates current density (I)-vs Time (s) characteristics of the (a) Ti.sub.4Pd.sub.2O photocathode, (b) Sn.sub.0.6Ti.sub.0.61O.sub.2 (c) Fe.sub.9TiO.sub.15 (d) CoTiO.sub.3 photoanodes recorded at 0 V in an 1 M aqueous K.sub.2SO.sub.4 electrolyte solution.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

EXAMPLES

(14) Applicants' methods can be applied for the preparation of a variety of nanocomposite materials with different choices of metals combinations and self-scarifying supports. Nanostructures prepared by these methods were homogeneous with well control over size and shape. These methods are highly reproducible and allow the synthesis of nanocomposites of desired combination even for composites not synthesized before in their nano-form. This could be a breakthrough for different applications in nanotechnology including but not limited to catalysis, water splitting, fuel cells, super-capacitors charge storage and sensing applications.

(15) Metal precursors which are soluble in tetrahydrofuran (THF) are best suited for this method. Once a homogenous solution is made polymerization is initiated with trifilic acid (TFC) and allowed till the formation of a gel which is then decomposed and calcined at optimized temperatures. Following are few examples for nanocomposites prepared by this method.

Example 1

(16) Synthesis of Fe.sub.9TiO.sub.15.TiO.sub.2 (Iron titanate). Ferrocence Ferrocene (1 g, 5.37 mM) was dissolved in 5 mL of THF, in a 20 mL glass bottle. TFC (0.2 mL, 22.6 mM) was added dropwise and slowly followed by dropwise addition of Titanium isopropoxide (1.80 L, 0.59 mM). The reaction mixture was left on stirring for 2 hours. A gel was formed which was transferred to a crucible. The crucible containing all reaction mixture was placed in a muffle furnace. The furnace was heated to 500 C. at a rate of 4 C. per minute and kept at 500 C. for 2 hours. A solid yellow product Fe.sub.9TiO.sub.15.TiO.sub.2 was obtained which was characterized by XRD (FIG. 2A) and tested as catalyst for nitroarenes reduction to nitroamines.

Example 2

(17) Synthesis of Fe.sub.9TiO.sub.15.SiO.sub.2 (Iron titanate at silica). Ferrocene (1 g, 5.37 mM) was dissolved in 5 mL of THF, in a 20 mL glass bottle. 0.5 g of mesoporous silica (SiO.sub.2) was added as an external support, TFC (0.2 mL, 22.6 mM) was added dropwise and slowly followed by dropwise addition of Titanium isopropoxide (1.628 mL, 5.37 mM). The reaction mixture was left on stirring for 2 hours. A gel was formed which was transferred to a crucible. The crucible containing all reaction mixture was placed in a muffle furnace. The furnace was heated to 500 C. at a rate of 4 C. per minute and kept at 500 C. for 2 hours. A solid yellow product Fe.sub.9TiO.sub.15.TiO.sub.2 was obtained which was characterized and tested as catalyst for nitroarenes reduction to nitroamines.

Example 3

(18) Synthesis of Ti.sub.4Pd.sub.2O. TiO.sub.2 (Titanium palladium oxide at titania). Pd(NO3)xH2O (0.2 g, 0.8 mM) was dissolved in 5 mL THF followed by dropwise addition of TFC (0.2 mL, 22.6 mM) and slow addition of Ti isopropoxide (1.314 mL, 4.335 mM) at the end. The reaction mixture was stirred for 2 hours, transferred to a crucible and placed in a muffle furnace. The temperature in the furnace was raised to 450 C., at a rate of 4 C. per minute, and held for 2 hours. A solid brown product Ti.sub.4Pd.sub.2O.circle-solid.TiO.sub.2 was obtained and characterized by XRD (FIG. 2A).

Example 4

(19) Synthesis of Sn.sub.0.39Ti.sub.0.61O.circle-solid.TiO.sub.2 (Titanium Tin Oxide at titania). SnCl.sub.2 (0.5 g, 2.2 mM) and Ti isopropoxide (6.6 mM, 2.0 mL) were dissolved in 5 mL THF and its polymerization was initiated by adding 0.2 mL (22.6 mM) of TFC Like in all other experiments, the reaction mixture was stirred for 2 hours, transferred in a crucible and placed in the furnace, heated to 400 C., at 3 C. per minute, and held for 2 hours. A clay white product was obtained. XRD of Sn.sub.0.39Ti.sub.0.61O.sub.2.circle-solid.TiO.sub.2 is shown in FIG. 2A.

Example 5

(20) Synthesis of CoTiO.sub.3.circle-solid.TiO.sub.2 (Cobalt titanium perovskite at titania). Cobalt acetyalacetonate (0.5 g, 1.944 mM) was dissolved in 5 mL THF, 0.2 mL (22.6 mM) of TFC was slowly added followed by dropwise addition of Ti isopropoxide (9.72 mM, 2.94 mL). After 2 h of stirring, reaction mixture was placed in a furnace, heated to 500 C. and held at this temperature for 2 hours. The product obtained was characterized by XRD (FIG. 2A).

Example 6

(21) Synthesis of (Mn.sub.2.88Fe.sub.0.12)O.sub.4 (Hausmannite). Manganese acetate (0.5 g, 2.04 mM) was added in 5 mL THF. Manganese acetate was partially soluble in THF, however, after addition of 0.2 mL (22.6 mM) of TFC it became completely soluble. Ferrocene (0.085 mM, 0.015 g) was also added in the same solution and reaction mixture was sonicated for 10 mins followed by stirring for 2 hours. The reaction mixture was heated to 500 C., at a rate of 4 C., and calcined for 2 hours before slowly cooling it down. XRD of (Mn.sub.2.88Fe.sub.0.12)O.sub.4 is represented in FIG. 7.

Example 7

(22) MnFeO.sub.3 (Bixbyite). MnFeO.sub.3 pervoskite was synthesized by dissolving manganese acetate (0.5 g, 2.04 mM), TFC (0.2 mL, 22.6 mM) and ferrocene (0.38 g, 2.04 mM,) in 5 mL THF as described in the previous experiment. The reaction mixture was heated to 500 C., at a rate of 4 C., and calcined for 2 hours. The product was characterized by XRD (FIG. 7).

Example 8

(23) Synthesis of Fe.sub.1.696Ti.sub.0.228O.sub.3.circle-solid.TiO.sub.2 (Iron Titanium Oxide at titania). Ferrocene (1 g, 5.37 mM) was dissolved in 5 mL of THF, in a 20 mL glass bottle. TFC (0.2 mL, 22.6 mM) was added dropwise and slowly followed by dropwise addition of Titanium isopropoxide (1.80 L, 0.59 mM). The reaction mixture was left on stirring for 2 hours. A gel was formed which was transferred to a crucible. The crucible containing all reaction mixture was placed in a muffle furnace. The furnace was heated to 500 C. at a rate of 4 C. per minute and kept at 500 C. for 4 hours. XRD of Fe.sub.1.696Ti.sub.0.228O.sub.3.circle-solid.TiO.sub.2 is shown in FIG. 7.

Example 9

(24) Synthesis of Ni.sub.1.43 Fe.sub.1.7O.sub.4 (Trevorite), and Ni.sub.1.43Fe.sub.1.7O.sub.4. TiO.sub.2 (Trevorite at titania) nanocomposites. For Ni.sub.1.43 Fe.sub.1.7O.sub.4 synthesis, Nickel acetylacetonate (1.946 mM, 0.5 g) and ferrocene (1.946 mM, 0.36 g) were dissolved in 5 mL of THF followed by addition of TFC (0.2 mL, 22.6 mM). The reaction mixture was stirred for 2 hours and resulting gel was transferred to a crucible and placed in a muffle furnace. The furnace was heated to 500 C. at a rate of 3 C. per minute and kept at 500 C. for 3 h. Ni.sub.1.43Fe.sub.1.7O.sub.4. TiO.sub.2 nanocomposite was synthesized by repeating the above procedure after adding 0.5 g of TiO.sub.2 in the reaction mixture. XRD (FIG. 7) and Rietveld (RIR) analysis (FIG. 8) showed the successful synthesis of nanocomposites in the desired ratios.

(25) While the invention has been defined in accordance with its preferred embodiments, it should be recognized that changes and modifications may be made therein without departing from the scope of the appended claims.