METHOD FOR PRODUCING GOLD NANOPARTICLES IN PLANTS AND GOLD NANOPARTICLES PRODUCED

Abstract

The present invention relates to the field of nanotechnology, more specifically to the production of gold nanoparticles (AuNPs) from plant extracts derived from leaves, stems, seeds, flowers, fruits or latex from plant species such as Colliguaja salicifolia, Pittosporum Undulatum, Acca sellowiana, Ugni molinae and Colliguaja integerrima, in which naturally occurring biocatalysts are possessed by these plants. The invention also relates to the gold nanoparticles obtained from said plants as well as to said natural biocatalysts.

Claims

1. Method to obtain gold nanoparticles from plants, said method comprised the steps of: a) obtaining an extract from the plant; b) heating said extract; c) eliminating the insoluble material from said extract; d) mixing under appropriate conditions the extract soluble material with a substrate comprising a gold salt; and e) Recovering the gold nanoparticles from said mixture.

2. Method according to claim 1, wherein said extract from a plant is an aqueous extract.

3. Method according to claim 2, wherein the aqueous extract is obtained by maceration from any part of the plant selected from seeds, steams, flowers, leaves, fruits, latex or a combination thereof.

4. Method according to claim 1, wherein said extract is heated until boiling between 1 and 10 minutes.

5. Method according to claim 1, wherein the insoluble material is eliminated by filtration.

6. Method according to claim 1, wherein said gold salt is HAuCl.sub.4.3H.sub.2O.

7. Method according to claim 1, wherein said appropriate conditions include continuously mixing the soluble extract with the substrate comprising the gold salt for 0.5 to 12 hours, at a temperature between 25-27° C.

8. Method according to claim 1, wherein the gold nanoparticles are recovered from said mixture by means of a step selected from low speed centrifugation and sedimentation on standing of the mixture for at least 1 hour.

9. Method according to claim 1, wherein said plant is selected from the group consisting of Colliguaja salicifolia, Pittosporum undulatum, Acca sellowiana, Ugni molinae and Colliguaja integerrima.

10. Gold nanoparticles obtained from Colliguaja salicifolia, Acca sellowiana, Pittosporum undulatum, Ugni molinae, or Colliguaja integerrima.

11. Gold nanoparticles according to claim 10, Pittosporum undulatum and having a spheroidal geometry and a diameter between 5 nm and 10 nm.

12. Gold nanoparticles according to claim 10, obtained from Ugni molinae and having a triangular, cubic, hexagonal, polyhedral, or spheroidal geometry and a diameter of about 5 nm and 200 nm.

13. Gold nanoparticles according to claim 10, obtained from Colliguaja integerrima and having a triangular, pentagonal, hexagonal, polyhedral, or spheroidal geometry and a diameter between 10 nm and 150 nm.

14. A biocatalyst for obtaining gold nanoparticles from plants selected from the group consisting of phenolic compounds triterpenoids, sesquiterpene glucosides, monoterpenes, diterpenes, alkanes, and vitamin C.

15. The biocatalyst of claim 14, wherein the phenolic compounds include flavonoids and tannins.

16. Gold nanoparticles according to claim 10 obtained from Colliguaja salicifolia which have a triangular, pentagonal, hexagonal, polyhedral, or spheroidal geometry and a diameter between 10 nm and 100 nm.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0035] FIG. 1. Represents the UV-visible spectrum from AuNPs synthesized from the Colliguaja salicifolia leaves vegetable extract. (.box-tangle-solidup.) curve generated by AuNPs suspension. (.square-solid.) curve generated by the HAuCl.sub.4 substrate. () curve generated by the leave extract from Colliguaja salicifolia.

[0036] FIG. 2. Represents the UV-visible spectrum from AuNPs synthesized from the Pittosporum undulatum seeds extract: (.box-tangle-solidup.) curve generated by AuNPs suspension. (.square-solid.) curve generated by the HAuCl.sub.4 substrate. () curve generated by the extract of Pittosporum undulatum seeds.

[0037] FIG. 3. Represents the UV-visible spectrum from the synthesized AuNPs from the Pittosporum undulatum leaves extract. (.box-tangle-solidup.) curve generated by AuNPs suspension. (.square-solid.) curve generated by the HAuCl.sub.4 substrate. () curve generated by the extract of Pittosporum undulatum leaves.

[0038] FIG. 4. Represents the UV-visible spectrum from the synthesized AuNPs from the Feijoa pericarpium from Acca sellowiana vegetable extract. (.box-tangle-solidup.) curve generated by AuNPs suspension. (.square-solid.) curve generated by the HAuCl.sub.4 substrate. () curve generated by the extract of Feijoa from Acca sellowiana pericarpium.

[0039] FIG. 5. Represents the UV-visible spectrum from the synthesized AuNPs from the Feijoa mesocarp from Acca sellowiana vegetable extract. (.box-tangle-solidup.) curve generated by AuNPs suspension. (.square-solid.) curve generated by the HAuCl.sub.4 substrate. () curve generated by the Feijoa mesocarp from Acca sellowiana extract.

[0040] FIG. 6. Represents the UV-visible spectrum from the synthesized AuNPs from the Ugni molinae fruits vegetable extract. (.box-tangle-solidup.) curve generated by AuNPs suspension. (.square-solid.) curve generated by the HAuCl.sub.4 substrate. () curve generated by the Ugni molinae fruits vegetable extract.

[0041] FIG. 7. Represents the UV-visible spectrum from the synthesized AuNPs from the vegetable extract of Colliguaja integerrima leaves. (.box-tangle-solidup.) curve generated by AuNPs suspension. (.square-solid.) curve generated by the HAuCl.sub.4 substrate. () curve generated by the Colliguaja integerrima leaves vegetable extract.

[0042] FIG. 8. Shows a microphotograph of AuNPs from the Coffiguaja salicifolia leaves vegetable extract taken at a magnification of 60.000× using tetrachloroauric acid as a substrate. The bar at the right lower side represents 200 nm.

[0043] FIG. 9. Shows a microphotograph of AuNPs from the Pittosporum undulatum seeds vegetable extract taken at a magnification of 60.000× using tetrachloroauric acid as a substrate. The bar at the right lower side represents 200 nm.

[0044] FIG. 10. Shows a microphotograph of AuNPs from the Pittosporum undulatum leaves vegetable extract, taken at a magnification of 60.000× using tetrachloroauric acid as a substrate. The bar at the right lower side represents 200 nm.

[0045] FIG. 11. Shows a microphotograph of AuNPs from the Feijoa pericarpium from Acca sellowiana extract, taken at a magnification of 60.000× using tetrachloroauric acid as a substrate. The bar at the right lower side represents 200 nm.

[0046] FIG. 12. Shows a microphotograph of AuNPs from the Feijoa mesocarp from Acca sellowiana extract, taken at a magnification of 60.000× using tetrachloroauric acid as a substrate. The bar at the right lower side represents 200 nm

[0047] FIG. 13. Shows a microphotograph of AuNPs from the Ugni molinae fruits extract, taken at a magnification of 87.000× using tetrachloroauric acid as a substrate. The bar at the right lower side represents 200 nm.

[0048] FIG. 14. Shows a microphotograph of AuNPs from the Colliguaja integerrima leaves extract, taken at a magnification of 87.000× using tetrachloroauric acid as a substrate. The bar at the right lower side represents 200 nm.

DETAILED DESCRIPTION OF THE INVENTION

[0049] Hereinafter the invention will be described in detailed making emphasis in examples of use of the different vegetable species previously listed. It must be understood that said examples are illustrative and are intended to provide a better understanding of the details of the invention, but do not limit the scope thereof.

EXAMPLES

Example 1: Vegetable Extract Preparation

[0050] To obtain the vegetable extract the following steps were followed: [0051] for Colliguaja salicifolia, 4 g of leaves or stems are weighted. [0052] for Pittosporum undulatum, 4 g of seeds, leaves, stems or fruits are weighted. [0053] for Acca sellowiana, 4 g of pericarpium, mesocarp, stems, leaves, seeds or flowers are weighted. [0054] for Ugni molinae 4 g of fruits, stems, leaves, seeds or flowers are weighted. [0055] for Colliguaja integerrima 4 g of leaves or stems are weighted.

[0056] In all cases, the selected parts are washed with distilled water and then macerated in a mortar to separate the liquid from the solid fraction. 100 mL of distilled water are added to the later fraction and heat is applied until boiling. Both samples, the liquid fraction obtained by maceration and the resulting from the heating at 100° C., are filtrated to eliminate the insoluble particles and are stored to later use.

[0057] Alternatively, to obtain the extract, 500 μL of latex from Colliguaja salicifolia or from Colliguaja integerrima are diluted until reaching 100 mL with distilled water. The mixture is heated until boiling, filtered to eliminate the insoluble particles, and used immediately or conveniently stored.

Example 2: Production of Metallic Nanoparticles

[0058] Metallic nanoparticle synthesis was performed adding the corresponding metallic substrate directly over the solution containing the molecules from the vegetable extract. In this case, to form the gold nanoparticles (AuNPs) tetrachloroauric acid trihydrate (HAuCl.sub.4.3H.sub.2O) was used. The proportion of reactants used was 1:4, adding 200 μL of extract and 800 μL of 1 mM solution of metallic substrate and completing a 1 mL volume.

Example 3: Characterization of Metallic Nanoparticles

a) Visual Characterization

[0059] Initial determination of nanoparticle formation was performed watching the color change of the solution containing the vegetable extract and the corresponding metallic substrate. When AuNPs formation happens, the solution turns purple-violet, characteristic color of the nanoparticle formation.

[0060] When mixing the Colliguaja salicifolia vegetable extract with tetrachloroauric acid, the AuNPs formation was detected by the color change from yellow-greenish to violet-purplish, characteristic of the AuNPs presence.

[0061] On the other hand, when mixing the Pittosporum undulatum seed or fruit extract with tetrachloroauric acid, AuNPs formation was detected by the color change from yellow to dark violet, while, with the leaves or stems extracts, the color change was from light yellow to dark pink, typical colors of AuNPs presence.

[0062] Additionally, when mixing the pericarpium or mesocarp extract from the Acca sellowiana fruit with tetrachloroauric acid, AuNPs formation was detected by the color change from light yellow to violet, characteristic of the AuNPs presence.

[0063] Furthermore, when mixing the Ugni molinae fruits extract with tetrachloroauric acid, the AuNPs formation was detected by the color change from pale pink to violet, characteristic of the AuNPs presence.

[0064] When mixing the Colliguaja integerrima vegetable extract with tetrachloroauric acid, AuNPs formation was detected by the color change from light yellow to bluish violet, characteristic of the AuNPs presence.

b) UV-Visible Spectroscopy

[0065] This technique was used to perform the samples qualitative analysis, as the absorbance peak or maximum of the particulate material suspension, can be related with the nanoparticle shape and size. This is possible because different metals nanoparticles have a maximum peak of absorbance in the UV-Visible spectrum with a wavelength (λ) characteristic of each one of them. In the case of AuNPs, a peak with a maximum absorbance between 500 and 550 nm is obtained.

[0066] In FIG. 1 a UV-Visible absorption peak for the AuNPs obtained using the Colliguaja salicifolia vegetable extract. The band of the surface plasmon resonance for the AuNPs formed by the Colliguaja salicifolia vegetable extract was obtained at 530 nm, showing a clear absorbance peak at this wavelength, while the curves obtained with the substrate or with the vegetable extract do not present absorbance variations in the range of the determined wavelengths.

[0067] In FIG. 2 it is possible to observe the UV-Visible spectrum for the AuNPs obtained using the Pittosporum undulatum seeds or fruits extract. The band of surface plasmon resonance for the AuNPs formed by the Pittosporum undulatum fruits or seeds extract was obtained at 560 nm. On the other hand, in FIG. 3 the UV-visible absorption spectrum for the AuNPs obtained using the Pittosporum undulatum leaves or stems extract. In this case, the spectrum shows a maximum absorbance of 530 nm. In both cases very defined absorbance peaks are observed at these wavelengths. The control curves obtained with the substrate or with the vegetable extract, do not presented absorbance variations in the range of the determined wavelengths.

[0068] In FIGS. 4 and 5 it is possible to observe the UV-visible absorption spectra for the AuNPs obtained from the pericarpium and mesocarp of the Acca sellowiana fruit extract, respectively. The surface plasmon resonance bands for the AuNPs formed by the Acca sellowiana pericarpium and mesocarp fruit extract were obtained at 540 and 550 nm, respectively, observing a clear absorbance peak at these wavelengths, while the curves obtained with the substrate or the vegetable extract, did not present absorbance variations in the range of the determined wavelengths.

[0069] In FIG. 6 it is possible to observe the UV-visible absorption spectrum of AuNPs obtained using the Ugni molinae fruits extract. The surface plasmon resonance band for the AuNPs formed by the Ugni molinae fruits extract was obtained at 530 nm, showing a clear absorbance peak at this wavelength, while the curves obtained with the substrate or the vegetable extract do not show absorbance variation in the range of the determined wavelengths. Similar results were obtained with Ugni molinae seeds, leaves, flowers and stems extracts.

[0070] In FIG. 7, it is possible to observe a UV-Visible spectrum for the AuNPs obtained using a Colliguaja integerrima leaves extract. The surface plasmon resonance band for the AuNPs formed by the Colliguaja integerrima leaves extract was obtained at 560 nm, observing a clear absorbance peak at this wavelength.

[0071] In FIGS. 1 to 7 it is possible to additionally observe that the UV-visible absorption curves obtained with the substrate or the vegetable extract, do not present absorbance variation in the range of the considered wavelengths:

[0072] The previous results confirm that the extracts obtained from Colliguaja salicifolia, Pittosporum undulatum, Acca sellowiana, Ugni molinae or Colliguaja integerrima species catalyze the synthesis of AuNPs, when tetrachloroauric acid is used as a substrate, in the used reaction conditions.

c) Transmission Electronic Microscopy

[0073] This technique was used to visualize the geometric shape and to determine the size of the metallic nanoparticles. It was also used to make an approximate estimation of the MNPs size distribution. To do so, nanoparticle solution aliquots are deposited over 200 mesh copper grids with formvar and carbon. Gold nanoparticle suspensions were observed in a Philips Tecnai 12 Bio Twin transmission electronic microscopy at 80 kV.

[0074] In FIG. 8 it is possible to observe the nanoparticles obtained using the Colliguaja salicifolia extract. These nanostructures present a great diversity in shapes and sizes. It is possible to observe triangular, pentagonal, hexagonal, polyhedral and spheroidal nanoparticles with a size ranging from about 10 to 100 nm in diameter.

[0075] In FIG. 9 it is possible to observe the AuNPs produced with the Pittosporum undulatum seeds or fruits extract. These nanoparticles are very homogeneous in shape and size. Most of them were visualized as spheroid structures with an approximate size between 5 to 10 nm in diameter. In contrast to the above, in FIG. 10 it is possible to observe the AuNPs obtained with the Pittosporum undulatum leaves and stems extract. In this case the nanostructures were more diverse in shape and size, observing triangular, polyhedral and spheroidal AuNPs with a size range from about 5 to 100 nm in diameter.

[0076] In FIGS. 11 and 12 it is possible to observe the AuNPs produced with pericarpium and mesocarp extract, respectively, from Acca sellowiana fruit. It is noted a great diversity in shapes and sizes. It is possible to observe triangular, pentagonal, hexagonal, polyhedral and spheroidal nanoparticles with a size ranging from about 10 to 100 nm in diameter.

[0077] In FIG. 13 it is possible to observe the AuNPs obtained using the Ugni molinae fruit extract. A great diversity of shapes and sizes can be observed. It is possible to visualize triangular, cubic, hexagonal, polyhedral and spheroidal nanoparticles with a size ranging from about 5 to 200 nm in diameter.

[0078] Lastly, in FIG. 14 it is possible to observe the AuNPs obtained using the Colliguaja integérrima leaves extract. A great diversity in shape and size is observed. It is possible to visualize triangular, pentagonal, hexagonal, polyhedral and spheroidal nanoparticles with a size ranging from about 10 to 150 nm in diameter.

[0079] The results from the transmission electronic microscopy confirm the ability of the Colliguaja salicifolia, Pittosporum undulatum, Acca sellowiana, Ugni molinae or Colliguaja integérrima de vegetable extract to catalyze the gold nanoparticles synthesis from HAuCl.sub.4.