A METHOD OF MAKING SILVER-IRON TITANATE NANOPARTICLES AND USES THEREOF

Abstract

High quality silver-iron titanate nanoparticles are synthesized using an ilmenite source. The silver-iron titanate nanoparticles were characterized using various analytical techniques. As compared to prior art methods, the disclosed methods provide for the simple, cost-effective synthesis of relatively high-quality silver-iron titanate nanoparticles. The silver-iron titanate nanoparticles can be used in a variety of important agricultural, industrial, and hygienic uses, including in the important area of plant tissue culture explant sterilization.

Claims

1. A method of synthesizing AgFeTiO.sub.3 nanoparticles comprising: a. providing an ilmenite source and a concentrated acid in a microwave digester vessel, wherein the ratio of ilmenite to acid is between 1:10 and 1:30; b. applying microwave radiation to the vessel for at least one hour; c. separating the resulting acidic solution from the vessel; d. adding a base to the separated acidic solution to form a mixture; e. stirring said mixture; f. aging said mixture for at least one hour to form an aged mixture; g. washing the resulting aged mixture with a dilute acid to form an acid washed mixture; h. adding a water-soluble silver compound to the acid washed mixture to create a silver liquid mixture; i. sonicating the silver liquid mixture; j. drying the sonicated silver liquid mixture to obtain a dried product; k. grinding the dried product; and l. calcinating the ground dried product at between 200 C. and 700 C. for at least 0.5 hours.

2. The method of claim 1 wherein the ilmenite source is Sri Lankan beach sand.

3. The method of claim 1 wherein the AgFeTiO.sub.3 nanoparticles are doped with another metal chosen from the group of Cu, Au, Pt, Zn, Ni, and Mn.

4. A method of sanitizing a plant comprising: a. applying AgFeTiO.sub.3 nanoparticles to the plant; b. activating the applied AgFeTiO.sub.3 nanoparticles using a visible light source.

5. The method of claim 4 wherein the plant is washed before the AgFeTiO.sub.3 nanoparticles are applied.

6. The method of claim 5 wherein the plant is washed with a surfactant.

7. The method of claim 4 wherein the AgFeTiO.sub.3 nanoparticles are applied in a solution.

8. The method of claim 4 wherein the sanitized plant is a plant node for use in tissue culture.

9. The method of claim 8 wherein the AgFeTiO.sub.3 nanoparticles kill plant node microbes without damaging plant growth.

10. The method of claim 8 wherein the plant node is placed in an agar medium after sanitization.

11. The method of claim 4 wherein the AgFeTiO.sub.3 nanoparticles are reused to sanitize another plant.

12. The method of claim 4 wherein the sole sanitation agent is AgFeTiO.sub.3 nanoparticles activated by a visible light source.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1 is a process flow diagram of the AgFeTiO.sub.3-40 synthesizing process, according to an example embodiment;

[0048] FIG. 2 is a Powder X-ray diffraction (PXRD) pattern of Sri Lankan Ilmenite (Beach sand), according to an example embodiment;

[0049] FIG. 3 is a Powder X-ray diffraction of synthesized AgFeTiO.sub.3-40 via HCl acid leaching, according to an example embodiment;

[0050] FIG. 4 shows Scanning Electron Microscopy (SEM) images of the synthesized AgFeTiO.sub.3-40, according to an example embodiment;

[0051] FIG. 5 shows energy dispersive X-ray (EDS) mapping of synthesized AgFeTiO.sub.3-40, according to an example embodiment;

[0052] FIG. 6 shows Fourier Transmission Infrared Spectroscopy (FTIR) of synthesized AgFeTiO.sub.3-40, according to an example embodiment;

[0053] FIG. 7 shows X-ray photoelectron spectroscopy (XPS) spectra of (A) synthesized AgFeTiO.sub.3-40 (B) Elemental binding energy of AgFeTiO.sub.3-40 according to an example embodiment;

[0054] FIG. 8 shows Band gap and UV-Vis DRS spectra of synthesized AgFeTiO.sub.3-40 according to an example embodiment;

[0055] FIG. 9 is a bar graph of Dracaena sanderiana plant nodes survived percentage of using Clorox solution, according to an example embodiment;

[0056] FIG. 10 is a bar graph of Dracaena sanderiana ornamental plant nodes survived after using synthesized AgFeTiO.sub.3-40, according to an example embodiment;

[0057] FIG. 11 is plant nodes of Dracaena sanderiana survived after sterilizing from (A) 10% Clorox, (B) (I) 1.sup.st wash, (II) 2.sup.nd wash and (III) 3.sup.rd wash from AgFeTiO.sub.3-40, according to an example embodiment;

[0058] Table 2 is an X-ray Fluorescent Spectroscopy (XRF) data of synthesized AgFeTiO.sub.3-according to an example embodiment;

[0059] Table 3 is an Energy Dispersed Spectroscopy (EDS) data of data of synthesized and AgFeTiO.sub.3-40 according to an example embodiment; and

[0060] Table 4 is a Chemical composition of prepared agar media, according to an example embodiment.

TABLE-US-00002 TABLE 2 Material Element Weight % AgFeTiO.sub.3-40 Ag 2.96 Fe 50.98 Ti 43.45

TABLE-US-00003 TABLE 3 Material Element Weight % Error % AgFeTiO.sub.3-40 Ag 2.72 31.67 Fe 35.51 4.59 Ti 34.09 3.45 O 26.98 12.39 Cl 0.61 45.36

TABLE-US-00004 TABLE 4 Required Amount in 500 volume from ml stock stock for 1 L Chemicals solution (mg) agar media Macro Ammonium Nitrate (NH.sub.4NO.sub.3) 16500 50 ml Potassium Nitrate (KNO.sub.3) 19000 Potassium Phosphate (KH.sub.2PO.sub.4) 1700 Magnesium Sulphate (MgSO.sub.47H.sub.2O) 3700 Calcium Chloride (CaCl.sub.22H.sub.2O) 4400 Micro-I Boric Acid (H.sub.3BO.sub.3) 620 5 ml Manganese Sulphate (MnSO.sub.47H.sub.2O) 2230 Zinc Sulphate (ZnSO.sub.47H.sub.2O) 860 Micro-II Potassium Iodide (KI) 83 5 ml Sodium Molybdate (Na.sub.2MoO.sub.42H.sub.2O) 25 Cupric Sulphate (CuSO.sub.45H.sub.2O) 2.5 Cobalt Chloride (CoCl.sub.26H.sub.2O) 2.5 Ferrous Source Na.sub.2EDTA2H.sub.2O 372 5 ml Ferrous Sulphate (FeSO.sub.47H.sub.2O) 278 Organics Glycine 200 5 ml Niacin 50 PyridoxineHCl 50 ThiamineHCl 10 Vitamin Myo-Inositol 100 mg/L 100 mg Fungicide folicur tebuconazole EW 250 g/L 5 l Other Ingredients White Sugar 30 g Agar powder 4.5 g

DETAILED DESCRIPTION

[0061] The following description provides detailed embodiments of various implementations of the invention described herein. After reading this description, it will become apparent to one skilled in the art how to implement the invention in various alternative embodiments and applications. However, various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only and not limitation. As such, the detailed description of embodiments should not be construed to limit the scope or the breadth of the invention.

Example 1: Process of Synthesizing AgFeTiO.SUB.3.-40

[0062] With reference to FIG. 1, in an example embodiment, approximately 5.00 g of Ilmenite was added to Teflon vessels in a microwave digester (e.g., ETHOS EASY, Milestone, Italy, 1800 W). Between about 10 and 15 ml of concentrated HCl (12.1 M) was then added to each of the ten vessels containing Ilmenite. In this example embodiment, the vessels were then sealed with Teflon caps, inserted into the vessel holder, and inserted into the reactor chamber. In various embodiments, the microwave reactor was run using between about 250 W to 300 W at a 90 bar pressure for about 1 hour. The temperature of about 110 C. was maintained during this time. In an example embodiment, generated HCl gas was emitted via a non-corrosive gas tube connected to the reactor. In an example embodiment, after removing the vessels from the chamber, the liquid fraction was carefully separated from solid Ilmenite and poured into a borosilicate glass bottle. The collected lixivium (filtrate) was utilized to synthesize AgFeTiO.sub.3-nanoparticles.

[0063] In this example embodiment, this separated acidic solution (about 100 ml from the 10 vials) was neutralized with 5 M NaOH (aq) via drop-wise addition (rate=0.5 ml/min) to the mixture with vigorously stirring and boiling by using a magnetic stirrer at 150 C. in a 1 L beaker. The pH was adjusted to 10 by adding NaOH continuously to the lixivium, which was determined using pH paper. The brown color particles were formed when pH reached up to 8; excess NaOH was added to the obtained complete brown color solution (pH=10). After that, the mixture was stirred for another 4 hours to obtain a well-homogenized solution. In other embodiments of this example, the mixture was stirred for 2 hours, 1 hour, 30 minutes, and 15 minutes. Then solution was then aged at room temperature (e.g. aging for 1 hour, aging for 4 hours, aging for 12 hours, aging for 24 hours, etc.). During aging brown solid particles separated from the liquid and settled at the bottom of the beaker. After that, excess NaOH was carefully removed without disturbing the brown residue. The following reactions indicated in equation 1-7 occurred in the acid-base reaction step.

H+(aq)+OH(aq).fwdarw.H.sub.2O(l)(1)

TiO.sup.2+(aq)+2H.sub.2O(l).fwdarw.H.sub.2TiO.sub.3(s)+2H.sup.+(aq)(2)

TiO.sup.2+(aq)+2NaOH(aq).fwdarw.Na.sub.2TiO.sub.3(s)+2H.sup.+(aq)(3)

Fe.sup.3+(aq)+3NaOH(aq).fwdarw.Fe(OH).sub.3(s)+3Na.sup.+(aq)(4)

TiO.sup.2+(aq)+Fe.sup.3+(aq)+2H.sub.2O(l).fwdarw.FeTiO.sub.3(s)+4H.sup.+(5)

3Ti.sup.4+(aq)+2Fe.sup.3+(aq)+9H.sub.2O(l).fwdarw.Fe.sub.2Ti.sub.3O.sub.9(s)+18H.sup.+(aq)(6)

Na.sub.2TiO.sub.3(s)+H.sup.+(aq).fwdarw.TiO.sup.2+(aq)+OH.sup.(aq)+2Na.sup.+(aq).fwdarw.Ti(OH).sub.4(s)(7)

[0064] In this example embodiment, the mixture was then washed with dilute (0.1 mol/dm.sup.3) HNO.sub.3 100 ml and 400 ml of distilled water. This step was repeated until Cl.sup. ions were removed from the solid particles. Removal of the Cl.sup. ions was confirmed using 2% silver nitrate (AgNO.sub.3) solution. At the final wash, the white color residue was not formed with 2% AgNO.sub.3, and it confirmed solids were free from Cl.sup. ions, and a maximum volume of 200 ml was obtained after the washing step. This Cl.sup. free brown precipitate was utilized to prepare AgFeTiO.sub.3-40 nanoparticles.

[0065] In this example embodiment, a silver solution was made from dissolving AgNO.sub.3 25 mg in 100 ml distilled water. AgFeTiO.sub.3-40 nanoparticles were synthesized by mixing 40% volume fractions (silver concentration equal to 100 mg/L) to the Cl.sup. free brown precipitate. The samples were then ultrasonicated for about 30 min by using a sonicator (e.g., GT Sonic-3L, 45 kHz, 30 C., ultrasonic power of 100 W). Sonicated liquid mixtures were then dried at about 105 C. in a hot air oven for between about 6 and 8 hours to remove water. Ultimately, the dried solid was ground to fine particles using a mortar and a pestle, calcined at 400 C. for 2 hours to obtain AgFeTiO.sub.3-40. In other example embodiments, the calcination step took place at temperatures between 200 C. and 700 C. for between 0.5 and 5 hours. During the calcination step, the following reactions occurred (equations 8-12).

Ti(OH).sub.4(s)TiO.sub.2(s)+2H.sub.2O(l)(8)

H.sub.2Ti.sub.3O.sub.7(s)3TiO.sub.2(s)+H.sub.2O(l)(9)

2Fe(OH).sub.3(s)Fe.sub.2O.sub.3(s)+3H.sub.2O(l)(10)

4Ag.sup.+(aq)+O.sub.2(g)2Ag.sub.2O(s)(11)

Ag.sup.+(aq)+FeTiO.sub.3(s)AgFeTiO.sub.3(s)(12)

[0066] Characterization of Synthesized AgFeTiO.sub.3-40

[0067] FIG. 2 is the powder X-ray diffraction (PXRD) pattern obtained using the Rigaku Ultima-IV XRD machine for Sri Lankan Ilmenite. It shows, Ilmenite (FeTiO.sub.3), Magnetite (Fe.sub.3O.sub.4), Hematite (Fe.sub.2O.sub.3), Rutile (TiO.sub.2), Pseudorutile (Fe.sub.2Ti.sub.3O.sub.9), Quartz (SiO.sub.2), and Zircon (ZrSiO.sub.4). This PXRD analysis suggests that the Sri Lankan Ilmenite sample not pure with various other minerals also present in the Ilmenite. The PXRD patterns of the product obtained for AgFeTiO.sub.3-40, as shown in FIG. 3. According to the FIG. 3 identified peaks in the diffractogram clearly emphasize the presence of the Anatase (TiO.sub.2), synthesized Ilmenite (FeTiO.sub.3), Hematite (Fe.sub.2O.sub.3), Pseudorutile (Fe.sub.2Ti.sub.3O.sub.9), Silver oxide (Ag.sub.2O), Silver chloride (AgCl), and metallic Ag. The EDX data confirm minor Ag metal, AgCl, Ag.sub.2O, and Ti, Fe, 0 elements in the photocatalyst (FIG. 5 & Table 2).

[0068] FIG. 4 shows a Scanning Electron Microscopy (SEM) image (Carl ZEISS EVO 18 Research) of the synthesized AgFeTiO.sub.3-40 solid particles. FIG. 4 shows the morphology of the product AgFeTiO.sub.3-40. Furthermore, FIG. 4 shows nanoparticles present in the large surface area of a particle.

[0069] Ag decorated FeTiO.sub.3 is observed in the EDX elemental mapping image taken by using Element EDAX analyzer is shown in FIG. 5. While areas related to Ag are not observed in the product (FIG. 5). Only a very minor amount of Ag is present in the FeTiO.sub.3 solids, approximately 2.72% oxygen in the EDX analysis. Both graphs show the nominal amount of Chloride (Cl.sup.) ions in the particles. That confirms the presence of AgCl identified in the XRD pattern in the AgFeTiO.sub.3-40 product.

[0070] The Cl.sup. present in the solids was not completely removed vial the simple acid washing steps. Thus some AgCl with Ag ions was formed by following reaction (13):

Ag.sup.+(aq)+Cl.sup.(aq).fwdarw.AgCl(s)(13)

[0071] FIG. 6 shows FTIR analysis of synthesized AgFeTiO.sub.3-40. FTIR experiments were carried out to characterize AgFeTiO.sub.3-40 using Thermo Scientific Nicolet S10 with the attenuated total reflectance (ATR) method. Few characteristic peaks are observed in the 520-600 cm.sup.1 region, the TiOTi bonds in FeTiO.sub.3 solids. In the IR spectrum, the peak at 3230 cm.sup.1 is attributed to the OH stretching vibration peaks. The peaks appear at 1634 cm.sup.1, which corresponds to the OH bending vibration.

[0072] FIG. 7(A & B) shows that X-ray Photoelectron Spectroscopy (XPS) analysis was done using Thermo Scientific ESCALAB. In the present study, XPS is used to investigate the surface properties of synthesized AgFeTiO.sub.3-40. Major peaks are observed for synthesized AgFeTiO.sub.3-40 at 711.24 eV for Fe (2p.sub.3/2), 724.18 eV for Fe (2p.sub.1/2), 529.90 eV for O (1 s), 458.60 eV for Ti (2p.sub.3/2), 198.90 eV for Cl (2p.sub.3/2) and 284.72 eV for C (1 s). Ag to synthesized FeTiO.sub.3 particles Ag peaks also appeared in AgFeTiO.sub.3-40 a pronounced peak is observed at 367.30 eV for Ag (3 d.sub.5/2), indicating the silver presence as oxides, chloride and Ag.sup.0 (s) as well.

[0073] FIG. 8 shows UV-Vis DRS analysis using PerkinElmer Lambda 365 UV-Vis spectrometer for synthesized Ag FeTiO.sub.3-40 nanoparticles. UV-Vis diffuse reflectance spectra (UV-Vis DRS) prepared for synthesized Ag FeTiO.sub.3-40 data using the Kubelka-Munk method. The plotting of [(R)hv].sup.n as a function of photon energy, n=2 used to obtain the direct band gap energy (E g) of AgFeTiO.sub.3-40, which corresponds to the value of E.sub.g extrapolated to =0, where F(R) is the Kubelka-Munk function. Calculated band gap energies of synthesized AgFeTiO.sub.3-40 is 2.80 eV. The presence of metallic impurities in the final product may significantly affect the band gap of AgFeTiO.sub.3-40 from the UV absorption to the visible range. Absorption edges for synthesized AgFeTiO.sub.3-40 samples are located at 728 nm. The UV-Vis absorption spectrum is calculated from diffuse reflectance and Fe oxide (Hematite) in the sample matrix leading to a significant red shift of optical response towards the visible light due to reduced band gap energy.

[0074] Table 2 is the XRF analysis (HORIBA Scientific XGT-5200) showed that AgFeTiO.sub.3-40 contain Ag 2.96%, Ti 43.45% and Fe 50.98%. XRF results confirms the presence in Ag in the AgFeTiO.sub.3-40 material which proves the EDS analysis (Table 2).

[0075] Table 3 is the elemental analysis data based on energy dispersive X-ray spectroscopy (EDX data) of the product AgFeTiO.sub.3-40. The EDX data obtained confirm that there is a high percentage of Ti 34.09%, Fe 35.51%, O 26.98% and minor Ag 2.72% in AgFeTiO.sub.3-40 and Cl.sup. present in sample.

[0076] Table 4 indicates the chemical composition of modified agar media for tissue culture experiment. An agar medium was prepared by addition of necessary volume and mass of mention chemicals in table 3. Afterward, agar medium was poured into 200 tubes and utilized for a tissue culture test. In some embodiments, a minor amount of Fungicide (folicur tebuconazole) was also added to prevent endophyte fungus from growing in the cultured tubes. The fungicide inhibits the growth spores and mycelium of the endophyte fungus.

Example 2: Sterilization of Dracaena sanderiana Plant Nodes

[0077] In an exemplary embodiment, Dracaena sanderiana ornamental plant stem segments (Nodes) were sterilized using AgFeTiO.sub.3-40 nanoparticles as follows. First, the plant was washed. In an exemplary embodiment liquid soap (about 10 drops) and water were used to rinse the nodes via shaking at about 180 RPM for about 30 minutes. Then, the soapy water was drained off and the nodes were washed with sterilized water 3 times. Next, about 20 mg of AgFeTiO.sub.3-40 was added to 100 ml of sterilized water and stirred (Speed=600 RPM) for about 30 minutes with direct visible light (50 W Warm white light) with the height of about 50 cm and intensity about 8500-9000 lux. After that, the explant was inoculated and cultured as described in Table 3 with 10 explants in every culture tube. Afterwards inoculated tubes were stored between 15 and 25 C. and 1500 lux fluorescent light, illumination 12 h/d for 31 days. The results are presented in FIG. 10.

[0078] A comparison with a common prior art method using Clorox is presented in FIG. 9, which shows the survival statistics for plant nodes washed in a 10% Clorox solution. In that comparison Clorox washing method, the disinfection process is done using the following methods of soaking disinfection: (1) Plant nodes were washed in 100 ml volume of 10% Clorox solution for 15 minutes with two drops of liquid soap by shaking the mixture with the speed of 180 RPM. The solution was then discarded. (2) Another 10% Clorox 100 ml volume soaked for 15 minutes, shaken, and the solution is discarded. (3) The plant nodes were then rinsed with sterilized water for 3 times. After that, explants were inoculated and cultured using the component provided in Table 3 with 10 explants for every culture tube. Afterwards, the inoculated tubes were stored for 31 days between 15 and 25 C. with a 1500 lux fluorescent light, illumination 12 h/d. The results are shown in FIG. 9.

[0079] After one month, results show 90% of plants nodes survived by sterilizing from AgFeTiO.sub.3-40 for 2 washing cycles (FIG. 11(B)-(I-II)), which means; out of 20 plant nodes, 18 nodes survived, and 60% of plant nodes survived a 3.sup.rd washing (FIG. 11(B)-(III)). This means that out of 10 nodes, 6 nodes survived. In the comparison prior art Clorox sterilizing technique, only 50% of plant nodes survived at one month (FIG. 11(A)). This suggests that the Clorox method was unable to eradicate fungus/bacteria for half of cultured nodes (5 nodes). Thus, suggest present invention is a more reliable sterilizing method compared with the Clorox solution. Moreover, the tissue culture industry might be benefitted due to this innovation because of less contamination obtained from bacteria and fungus growth in cultured media. Accordingly, this innovation can be useful for fungus and bacterial attacks in tissue culture technology without using toxic chemicals like mercury chloride. This high success rate will lead to save considerable amount of expenditure and time.

[0080] Although the various embodiments have been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be clear to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present disclosure, are contemplated thereby, and are intended to be covered by the following claims.

[0081] Many modifications and other embodiments set forth herein will come to mind to one skilled in the art to which these disclosures pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosures are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.