Claims:. A method for synthesis of nano plant nutrients comprises step of:
a) an aqueous solution of plant nutrient is prepared by dissolving plant nutrient in water;
b) an aqueous solution of natural polymer is prepared by dissolving the natural polymer in acetic acid;
c) adding drop-wise the aqueous solution of step a) to the solution of step b) to form a mixed solution; and
d) mixing the mixed solution at rpm in range of 50 to 500 for 15-20 minutes for uniform mixing at room temperature and atmospheric pressure.

2. The method as claimed in claim 1, wherein the natural polymer is chitosan.
3. The method as claimed in claim 1, wherein the molecular weight of the chitosan polymer is varied from 5000 Da to 3,10,000 Da.
4. The method as claimed in claim 1, wherein the plant nutrient and natural polymer is present in ratio from 0.67 to 550.
5. The method as claimed in claim 1, wherein the natural polymer concentration is in range from 0.1% to 1.5% wt./v.
6. The method as claimed in claim 1, wherein the concentration of acetic acid is varied from 0.5% to 10% wt./v.
7. The method as claimed in claim 1, wherein the method optionally comprises of crosslinking agent selected from STPP, polyacrylic acid based polymer or alike.
8. A nano-plant nutrient composition comprising plant nutrient coated with natural polymer, wherein the natural polymer is chitosan.
9. The nano- plant nutrient composition as claimed in claim 8, wherein the plant nutrient is present in an amount 1% to 25% of the total weight of the nano- plant nutrient composition.
10. The nano- plant nutrient composition as claimed in claim 8, wherein the size of the nanoparticle is in the range of 1-1000 nanometers.
11. The nano- plant nutrient composition as claimed in claim 8, wherein the nano- plant nutrient is an aqueous solution.
12. The nano- plant nutrient composition as claimed in claim 8, wherein the plant nutrient is diammonium phosphate (DAP).
, Description:FIELD OF THE INVENTION
[0001] The present invention relates to a method for synthesis of nano plant nutrients for improving the bioavailability of macro and micronutrients to plants.

BACKGROUND OF THE INVENTION
[0002] Plants require certain essential nutrients for normal functioning and growth. Nutrient levels outside the amount required for normal functioning and growth may cause overall crop growth and health to decline due to either a deficiency or a toxicity. Nutrient deficiency occurs when an essential nutrient is not available in sufficient quantity to meet the requirements of a growing plant. Toxicity occurs when a nutrient is in excess of plant needs and decreases plant growth or quality.
[0003] Commercial fertilizers contain macronutrients and micro nutrients that are essential for plant growth and macronutrients are used by plants in relatively large amounts. As defined herein primary macronutrients are nitrogen (N), phosphorous (P) and potassium (K) while calcium (Ca), magnesium (Mg) and sulphur (S) are secondary macronutrients. All six nutrients are important for plant growth.
[0004] As defined herein, micronutrients required in small amounts for plant growth are boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), molybdenum (Mo) and selenium (Se).
[0005] Nitrogen, phosphorus and potassium (NPK), which are required in large amounts for plants, are not always adequately available in natural soils to support the sustained growth of plants. Therefore, these macronutrients (NPK) are often needed to be applied externally through fertilizer.
[0006] Fertilizers, particularly synthetic fertilizers have a major potential to pollute soil, water and air; in recent years, many efforts were done to minimize these problems by agricultural practices and the design of the new improved fertilizers. Water soluble conventional fertilizers typically result in a large amount of macronutrients being lost by leaching and evaporation. Conventional fertilizers are generally applied on the crops by either spraying or broadcasting. However, one of the major factors that decide the mode of application is the final concentration of the fertilizers reaching to the plant. In practical scenario, very less concentration (much below to minimum desired concentration) reaches to the targeted site due to leaching of chemicals, drift, runoff, evaporation, hydrolysis by soil moisture, and photolytic and microbial degradation. It has been estimated that around 40-70% of nitrogen, 80-90% of phosphorus, and 50-90% of potassium content of applied fertilizers are lost in the environment and could not reach the plant, which causes sustainable and economic losses.
[0007] Hence, there remains a need for improvement in fertilizer to provide essential plant nutrient for agricultural application without causing or limiting environmental hazard.
[0008] Nanotechnology is an enabling technology. Metallic, oxide and semiconductor nanoparticles have properties entirely different from their bulk. Due to their unusual optoelectronic and physico-chemical properties, they find application in electronics, sensing, catalysis, paints, solar cells, etc. There are numerous manuscripts in the public domain that demonstrate this fact. Polymer nanoparticles are a different class of nanoparticles, which have the ability to entrap different entities. The objective of using polymer nanoparticles is to exploit the small size and its ability to penetrate tissue; and has been extensively used in pharma to design anti-cancer nano-drugs. The present invention is using this ability of polymer nanoparticles to entrap molecules as delivery vehicles inside plants.

SUMMARY OF THE INVENTION
[0009] The present invention provides a method for synthesis of nano plant nutrients and providing important plant nutrient for agricultural application without causing or limiting environmental hazard. The present invention provides a nano- plant nutrient composition encapsulating diammonium phosphate (DAP) or NPK plant nutrient or secondary micronutrient compounds to provide an economical and readily available source imminently suitable for correcting macronutrient and micronutrient deficiencies in plant life growing at such sites.
[0010] In embodiment of the present invention a method for synthesis of nano plant nutrients composition using natural polymer and in the absence of cross-linking agent, comprises step of:
a) an aqueous solution of plant nutrient is prepared by dissolving plant nutrient in water;
b) an aqueous solution of natural polymer is prepared by dissolving the natural polymer in acetic acid;
c) adding drop-wise the aqueous solution of step a) to the solution of step b) to form a mixed solution; and
d) mixing the mixed solution at rpm in range of 50 to 500 for 15-20 minutes for uniform mixing at room temperature and atmospheric pressure.
[0011] In another embodiment of the present invention the natural polymer is chitosan with the molecular weight of the chitosan polymer is varying from 5000 Da to 3,10,000 Da.
[0012] In yet another embodiment of the present invention the ratio of percent plant nutrient: percent natural polymer by weight is in the range from 0.67 to 550 and the natural polymer concentration is varied from 0.1% to 1.5% wt./v.
[0013] In yet another embodiment of the present invention the concentration of acetic acid is varied from 0.5% to 10% wt./v.
[0014] In yet another embodiment of the present invention the method optionally comprises of crosslinking agent selected from STPP, polyacrylic acid based polymer or alike.
[0015] In yet another embodiment of the present invention disclosed is a nano-plant nutrient composition comprising plant nutrient coated with natural polymer, wherein the natural polymer is chitosan wherein the plant nutrient is present in an amount 1% to 25% of the total weight of the nano-plant nutrient composition.
[0016] In yet another embodiment of the present invention the size of the nanoparticle is in the range of 1-1000 nanometers.
[0017] In yet another embodiment of the present invention the nano-plant nutrient is an aqueous solution.
[0018] In yet another embodiment of the present invention plant nutrient is diammonium phosphate (DAP).

BRIEF DESCRIPTION OF THE FIGURES
[0019] Figure 1 is a schematic diagram of process for the formation of plant nutrient nanoparticles.
[0020] Figure 2 is a High Resolution Transmission Electron Microscopy (HR-TEM) images of DAP nanoparticles. High resolution image on right (top) shows the atomic arrangement of DAP. The Selected Area Electron Diffraction (SAED) pattern (bottom right) shows the crystalline nature of the nanoparticles.

[0021] Figure 3 is Field Emission Scanning Electron Microscope (FESEM) image and particle size distribution.
[0022] Figure 4 shows the dynamic light scattering data. This gives the hydrodynamic diameter of the nanoparticles. Data for zeta potential is also shown.

DESCRIPTION OF THE INVENTION
[0023] The following detailed description is presented to enable any person skilled in the art to make and use the invention. For purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that these specific details are not required to practice the invention. Descriptions of specific applications are provided only as representative examples. The present application is not intended to be limited to the embodiments shown, but is to be accorded the widest possible scope consistent with the principles and features disclosed herein.
[0024] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed method and compositions belong. It must be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to “a plant nutrient” includes “one or more” plant nutrients or a “plurality” of such nutrients. With respect to the teachings in the present application, any issued patent, pending patent application or patent application publication described in this application is expressly incorporated by reference herein.
[0025] Similarly, the words "comprise," "comprises," and "comprising" are to be interpreted inclusively rather than exclusively. Likewise, the terms "include," "including" and "or" should all be construed to be inclusive, unless such a construction is clearly prohibited from the context. However, the embodiments provided by the present disclosure may lack any element that is not specifically disclosed herein. Thus, a disclosure of an embodiment defined using the term "comprising" is also a disclosure of embodiments "consisting essentially of’ and "consisting of’ the disclosed components. Where used herein, the term "example," particularly when followed by a listing of terms, is merely exemplary and illustrative, and should not be deemed to be exclusive or comprehensive. Any embodiment disclosed herein can be combined with any other embodiment disclosed herein unless explicitly indicated otherwise.
[0026] As used herein, the term “nanoparticle” refers to any particle having an average diameter of less than 1000 nanometers (nm). In some embodiments, nanoparticles have an average diameter of less than 300 nm, less than 100 nm, less than 50 nm, less than 25 nm, less than 10 nm or less than 5 nm. In some embodiments, each nanoparticle has a diameter of less than 300 nm, less than 100 nm, less than 50 nm, less than 25 nm, less than 10 nm or less than 5 nm.
[0027] As used herein, the terms “nanoparticle formulation” or “nanoparticle composition” are used interchangeably with reference to any substance that contains at least one nanoparticle. In some embodiments, a nanoparticle formulation is a uniform collection of nanoparticles. Nanoparticle formulation could contain nanoparticles having diameters in a range from 1 nm to 1000 nm, 5nm to 500 nm, 5 nm to 300 nm, 5 nm to 100 nm, 5 nm to 50 nm or below 5 nm. The nanoparticle formulation could also have a bi-modal size distribution where some particles could lie in a range of 1-50 nm and remaining could lie in the range of 50 nm to 1000 nm.
[0028] According to the embodiments herein, the term plant nutrient means mineral nutrients which include the broad class of macronutrient and micronutrient. The macronutrient further includes primary nutrient such as nitrogen (N), phosphorous (P) and potassium (K) and secondary nutrients such as calcium (Ca), magnesium (Mg) and sulfur (S). While micronutrients includes boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn).
[0029] Fertilizer can comprise any suitable plant nutrient, such as, for example, nitrates, urea, potashes, phosphate fertilizers such as mono-ammonium phosphate (MAP), diammonium phosphate (DAP), single superphosphate, triple superphosphate, potassium phosphates, calcium phosphates and combinations thereof. Micronutrients can comprise boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), chlorine (CI), cobalt (Co), sodium (Na), nickel (Ni), selenium (Se), and combinations thereof. Micronutrients can be in the form of discrete particles or platelets, and can optionally be incorporated into a natural polymer matrix.
[0030] In the present invention the term fertilizer and plant nutrient are used interchangeably.
[0031] Di-ammonium Phosphate (NH4)2HPO4 popularly known as DAP is a preferred plant nutrient because it contains both Nitrogen and Phosphorus which are primary macro-nutrients and part of 18 essential plant nutrients. Fertilizer grade DAP Contains 18% Nitrogen and 46% Phosphorus (P2O5). Phosphorus is an essential nutrient along with Nitrogen and plays a vital role in the development of new plant tissues and the regulation of protein synthesis in crops. DAP provides the phosphorus nutrition throughout crop growth and development cycle, as well as fulfils crops initial requirement of Nitrogen. DAP is manufactured by reacting Ammonia with Phosphoric acid under controlled conditions in fertilizer plants.
[0032] DAP has an alkaline pH and suspend in soil quickly to release phosphate and ammonium for the plants. DAP is applied to the soil considering important factors such as placement, proportion and time of crop cycle. DAP can be applied either during pre-sowing cultivation, tilling or during sowing of crops. The dosage should be as per the crop and soil (As per general recommendation for the State). It is advised not to use DAP on standing crops. It should be applied near the seeds as the DAP dissolves in the soil and provides temporary alkalization of the pH of the soil thus helping in better absorption of fertilizers in the early crop growth cycle. The DAP must not be used to close to the roots as the release of the ammonium can damage the seedlings and the plant roots, and damage occurs when the pH is higher than 7. DAP is an excellent source of Nitrogen that will gradually be converted into nitrate by the soil bacteria so a rise in pH is the temporary effect. The benefits of DAP fertilizers includes high yield, high in nutrients value, does not have side effects as it is broken down by the soil bacteria, high content of Nitrogen and Phosphorous needed for the plants is provided by DAP, cost-effective and high growth in plants brings in high profits.
[0033] According to the embodiments herein, natural polymers refer to such as agar, starches, alginates, chitosan, and cellulose. Natural polymers are commercially viable in field-based agricultural applications as they are cheap, readily available and biodegradable. The preferred natural polymer for the purpose of the present invention is chitosan.
[0034] Chitosan is obtained from chitin which is considered as the second most abundant naturally occurring polysaccharides next to cellulose found in the planet. Chitin and cellulose feature prominent biochemical similarities found in the plant cell walls which include linear polysaccharide chain and are neutrally charged. However, unlike cellulose, chitin provides mechanical, physical and structural stability. Structurally, chitin is composed of repeating unit of saccharide monomer of N-acetylglucosamine while cellulose consists of a linear chain of several hundred to thousands of β linked d-glucose units. After deacetylation of chitin, chitosan is obtained which is composed of a linear polymer consisting of two sub-units, d-glucosamine and N-acetyl-d-glucosamine linked together by glycosidic bonds. The presence of this amine group facilitates structural modifications and synthesis of functional derivatives. Chitin is basically present in arthropods exoskeleton materials such as crab, shrimp and some fungi. Commercially, chitosan is prepared by demineralization of chitin using acids followed by a deproteinization with a base.
[0035] Now, chitosan and its oligosaccharides have gained wide prospects in agricultural application, biomedicine and biotechnology due to their biocompatibility, biodegradability and bioactivity. Chitosan-treated solids will contain residual chitosan that is bonded to the solids and be included in any subsequent plant nutrient or other products made from those solids, in an amount equivalent to the weight of a few insects in several pounds of fertilizer. Chitosan’s bonding properties discourage plant nutrient runoff, inhibiting a key problem with plant nutrient use.
[0036] In an embodiment of the present invention the first step in the process of the present invention is to prepare aqueous solution of plant nutrient by dissolving it in water. Second step involves preparation of solution of natural polymer chitosan by dissolving it in acetic acid. It is followed by drop wise addition of aqueous solution of plant nutrient to solution of chitosan. After complete addition of plant nutrient solution to chitosan solution, the resultant mixture is stirred for sufficient time to ensure homogeneous solution. The homogenously mixed chitosan-plant nutrient solution is stirred for sufficient time for uniformly mixing and dissolution. The resultant solution formed is colloidal dispersion of nanoparticles of plant nutrients. The pH of colloidal suspension is in range of 4 to 7.
[0037] In the prior art, synthesis of chitosan nanoparticle has been documented. Typically, chitosan powder is dissolved in acetic acid to make a chitosan solution that has a concentration of 0.1-1.5% wt./v.. To this solution varying concentration of a cross-linking agent sodium triphosphate (STP), (also known as sodium tripolyphosphate (STPP), or simply tripolyphosphate (TPP)) is added. The phosphate groups of this molecule cross-link the amine groups in the chitosan polymer causing collapse or folding of the chitosan polymer to give spherical nanoparticles. These nanoparticles act as template for entrapment or immobilization of different entities. For agri-applications, one such example is that of urea entrapment in chitosan nanoparticles. This is an ex-situ process (first step being synthesis of chitosan nanoparticles and second step being immobilization of urea molecules). As per the definition of nanoparticles, either the active ingredients (e.g. urea) needs to be in the nano form (nano crystal) or, it can be loaded onto a nanoparticle carrier (such as chitosan nanoparticles in the present invention) and still be termed as nano-urea. The Chitosan used in present invention is obtained from Sigma Aldrich and is a commercial chemical. However, any person skilled in the art can obtained the same from other commercial resources.
[0038] During an industrial process, STPP can easily leach out to the environment and pollute the water bodies causing eutrophication. Use of STPP in detergents is the biggest cause of eutrophication. Additionally, nano plant nutrient prepared using STPP can enter into food chain. Organic form of phosphate is naturally present in body (DAP is absorbed by plants and converted into organic form of phosphate). Inorganic forms of phosphate such as STPP elevate phosphate levels in serum and could lead to cardiovascular problems. Furthermore, salts of polyphosphate anions are moderately irritating to skin and mucous membranes because they are mildly alkaline.
[0039] In the present invention, the inventors have developed a simple, one-step process for synthesis of nano plant nutrient without the need of cross-linking agent such as STPP, and thus an environmentally and plant friendly process. Besides this, due to the one-step process, the present process saves time and energy.
[0040] Mechanism: The presence of amine groups in the chitosan molecule attracts the negatively charged molecules/ ions in the plant nutrient samples such as diammonium phosphate. DAP dissociates in water to give a negative charge on phosphate group which binds to amine groups of chitosan. The DAP has two units of negative charge which could bind to two different amine groups in the polymer chain which could lead to cross-linking. Presence of individual DAP units can act as a nucleation site for further attachment of DAP units and due to nucleation and growth based on Ostwald ripening, could lead to the formation of DAP nanoparticles or nanocrystals. This nanoparticle, due to the presence of phosphate groups on the surface could lead to the Chitosan-amine group– mediating “capping” or coating of DAP nanoparticle/nanocrystal surface.
[0041] It is important to note here that as per earlier reports, cross linking due to STPP leads to formation of chitosan nanoparticle; whereas in the present invention DAP attachment in absence of STPP, leads to DAP nanocrystal formation and subsequent coating by chitosan. These two mechanisms are different. Figure 1 describes the mechanism of nanoparticle formation in the present invention.
[0042] Thus, from the foregoing description, it will be apparent to one of the person skilled in the art that many changes and modifications can be made thereto without departing from the scope of the invention as set forth in the description. Accordingly, it is not intended that the scope of the foregoing description be limited to the description set forth above, but rather that such description be construed as encompassing such features that reside in the present invention, including all the features and embodiments that would be treated as equivalents thereof by those skilled in the relevant art.
[0043] The embodiments of the present invention are more particularly described in the following examples that are intended as illustrations only, since numerous modifications and variations within the scope of the present invention will be apparent to those of skilled in the art. Unless otherwise noted, all parts, percentages and ratios reported in the following examples are on a weight basis and all reagents used in the examples were obtained or are available from the chemical suppliers.

[0044] Example 1: Process for formation of Nano-DAP using natural polymer chitosan
[0045] To illustrate the process of the present invention DAP is taken as plant nutrient. The first step involves preparation of solution of chitosan. 0.5g Chitosan (Molecular weight – 1,90,000-3,10,000 Da) is taken and dissolved in 10% acetic acid and was stirred on for approximately 24 hours for complete mixing of chitosan solution. 10% acetic acid solution is prepared by dissolving 10 ml glacial acetic acid in 90 ml of distilled water.
[0046] 11 g of DAP powder is taken in a beaker and dissolved in 20 ml of distilled water. Then DAP solution is added drop-wise to 80 ml of the chitosan solution. After complete addition the resultant mixture is stirred for 30 minutes to ensure homogeneous solution. The resultant solution formed is colloidal dispersion of nanoparticles. It is observed that nanoparticles of DAP are in range of around 1-200 nm.
[0047] Figure 2 shows High resolution Transmission electron microscopy (HRTEM) images recorded for nano DAP obtained from Example 1. HRTEM is carried out by using JEOL JEM 2100 plus. The dark dots in the image are nanoparticles clearly showing the ultra-small size of the present invention nano DAP (size range 5-30 nm). The high-resolution image clearly shows the atomic arrangement of DAP. The selected area electron diffraction (SAED) with concentric rings and dots clearly show the presence of crystalline form of nanoparticles; more particularly can be termed as nano crystal of DAP.

[0048] Figure 3 shows the Field emission scanning electron microscopy (FESEM) image as well as particle size analysis of nano DAP obtained from Example 1. SEM is carried out by using FEI Nova NanoSEM 450 instrument.
[0049] Figure 4 shows the dynamic light scattering data which gives the hydrodynamic diameter of the nanoparticles. Dynamic light scattering data which shows a broad particle size distribution. The zeta potential of the particles is + 24 mV as shown in Figure 4 indicates that the nanoparticles are positively charged of nano DAP obtained from Example 1.

[0050] Example 2: Process for synthesis of 1000 lit (1 KL) of Nano-DAP at pilot plant:
1% Chitosan stock solution
10 kg chitosan powder (MW range: 1,90,000-3,10,000 Da) is added to 2 KL reactor. To this, 100 lit of glacial acetic acid is added and the solution stirred for 1 hour. Post this, 900 litres of demineralized water is added and the entire solution is stirred for a period of 24 hours.
DAP stock solution: To a 1 KL reactor, 200 litres of demineralized water is added. To this, 110 kg of commercial bulk grade powdered DAP is added (P2O5 content can range from 46% to 52%).
Nano DAP reaction: To the main reactor, 420 litres of 1% Chitosan stock solution (prepared above) is added and stirring is started. To this solution, 42 litres of glacial acetic acid is added and the entire solution is further stirred for 15 minutes. To this, 338 litres of demineralized water is added and the solution is further stirred for 15 more minutes. After this, entire quantity of the DAP stock solution is added drop wise to this solution. To increase the rate of addition the DAP solution is added through a spray nozzle atomizer. Air and liquid are fed to the spray nozzle and rate of addition in the form of atomized spray can vary from 0.1 L per minute to 1 litre per minute or more. After complete addition, the stirring is continued for another 1 hour. Resultant solution formed is turbid looking colloidal dispersion of nano DAP. Subsequently, standard formulating agents are added to this nano DAP solution to make the final formulation. The product is further bottled directly and can be shipped to the market after packaging.

[0051] Example 3: Process for synthesis of nano DAP using varying concentration of DAP
1) 1% DAP
a) 0.5% Chitosan stock solution is prepared by dissolving 0.5 grams of chitosan powder in 10 mL glacial acetic acid and further diluting by deionized water to 100 mL total volume under stirring. The solution is further stirred for 24 h before use.
b) In a beaker, 0.25g of DAP powder is dissolved in 5mL distilled water.
c) Then 5mL DAP solution is added drop-wise to 20mL 0.5% chitosan stock solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 1% DAP and 0.4% Chitosan.
2) 5% DAP
a) 0.5% Chitosan stock solution is prepared by dissolving 0.5 grams of chitosan powder in 10 mL glacial acetic acid and further diluting by deionized water to 100 mL total volume under stirring. The solution is further stirred for 24 h before use.
b) In a beaker, 1.25g of DAP powder is dissolved in 5mL distilled water.
c) Then 5mL DAP solution is added drop-wise to 20mL chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 5% DAP and 0.4% Chitosan.
3) 15% DAP
a) 0.5% Chitosan stock solution is prepared by dissolving 0.5 grams of chitosan powder in 10 mL glacial acetic acid and further diluting by deionized water to 100 mL total volume under stirring. The solution is further stirred for 24 h before use.
b) In a beaker, 3.75g of DAP powder is dissolved in 10mL distilled water.
c) Then 10mL DAP solution is added drop-wise to 15mL chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 15% DAP and 0.4% Chitosan.
4) 21% DAP
a) 0.5% Chitosan stock solution is prepared by dissolving 0.5 grams of chitosan powder in 10 mL glacial acetic acid and further diluting by deionized water to 100 mL total volume under stirring. The solution is further stirred for 24 h before use.
b) In a beaker, 5.25g of DAP powder is dissolved in 10mL distilled water.
c) Then 10mL DAP solution is added drop-wise to 15mL chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 21% DAP and 0.4% Chitosan.
5) 25% DAP
a) 0.5% Chitosan stock solution is prepared by dissolving 0.5 grams of chitosan powder in 10 mL glacial acetic acid and further diluting by deionized water to 100 mL total volume under stirring. The solution is further stirred for 24 h before use.
b) In a beaker, 6.25g of DAP powder is dissolved in 10mL distilled water.
c) Then 10mL DAP solution is added drop-wise to 15mL chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 25% DAP and 0.4% Chitosan.
For higher concentrations of DAP solubility issues were observed due to high concentration and limiting solubility of DAP and more time is required for complete dissolution.

[0052] Example 4: Process for synthesis of nano DAP using varying concentration of initial chitosan concentration:
It was observed that dissolving chitosan in higher quantities is a challenge and higher than 1.5% chitosan solution is very viscous and could lead to variation in nanoparticle properties and is practically not easy.
1) 0.1% Chitosan
a) In a beaker, 11g of DAP powder is dissolved in 20mL distilled water.
b) 1% Chitosan stock solution is prepared in 10% acetic acid by weighing 1 g of Chitosan and dissolving in 10 mL glacial acetic acid and further addition of 90 mL of demineralized water. This solution is stirred for 12-24 hrs. Further, 8mL of 1% chitosan solution is taken in a beaker and to this, 72mL acetic acid-water solution is added and mixed uniformly resulting in final concentration of chitosan to be 0.1% and final volume to be 80mL.
c) Then 20mL DAP solution is added drop-wise to 80mL 0.1% chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11% DAP and 0.08% Chitosan.
2) 0.25% Chitosan
a) In a beaker, 11g of DAP powder is dissolved in 20mL distilled water.
b) 1% Chitosan stock solution is prepared in 10% acetic acid by weighing 1 g of Chitosan and dissolving in 10 mL glacial acetic acid and further addition of 90 mL of demineralized water. This solution is stirred for 12-24 hrs. Further, 20 mL of 1% chitosan solution is taken in a beaker and to this, 60 mL acetic acid-water solution is added and mixed uniformly resulting in final concentration of chitosan to be 0.25% and final volume to be 80mL.
c) Then 20mL DAP solution is added drop-wise to 80mL 0.25% chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11% DAP and 0.2% Chitosan.
3) 0.5% Chitosan
a) In a beaker, 11 g of DAP powder is dissolved in 20mL distilled water.
b) 1% Chitosan stock solution is prepared in 10% acetic acid by weighing 1 g of Chitosan and dissolving in 10 mL glacial acetic acid and further addition of 90 mL of demineralized water. This solution is stirred for 12-24 hrs. Further, 40 mL of 1% chitosan solution is taken in a beaker and to this, 40 mL acetic acid-water solution is added and mixed uniformly resulting in final concentration of chitosan to be 0.5% and final volume to be 80mL.
c) Then 20mL DAP solution is added drop-wise to 80mL 0.5% chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11% DAP and 0.4% Chitosan.
4) 0.5% Chitosan in dilute acetic acid
For all above reactions, 10% acetic acid is used. This example demonstrates nano DAP synthesis using 1% acetic acid.
a) In a beaker, 11 g of DAP powder is dissolved in 20mL distilled water.
b) 1% Chitosan stock solution is prepared in 1% acetic acid by weighing 1 g of Chitosan and dissolving in 1mL glacial acetic acid and further addition of 99 mL of demineralized water. This solution is stirred for 12-24 hrs. Further, 40 mL of 1% chitosan solution is taken in a beaker and to this, 40 mL acetic acid-water solution is added and mixed uniformly resulting in final concentration of chitosan to be 0.5% and final volume to be 80mL.
c) Then 20mL DAP solution is added drop-wise to 80mL 0.5% chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11% DAP and 0.4% Chitosan.
5) 1% Chitosan
a) In a beaker, 11g of DAP powder is dissolved in 20mL distilled water.
b) 1% Chitosan stock solution is prepared in 10% acetic acid by weighing 1 g of Chitosan and dissolving in 10 mL glacial acetic acid and further addition of 90 mL of demineralized water. This solution is stirred for 12-24 hrs. 80 mL of this solution is used as is in the next step without further dilution.
c) Then 20mL DAP solution is added drop-wise to 80mL 1% chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11% DAP and 0.8% Chitosan.
6) 1.25% Chitosan
a) In a beaker, 11g of DAP powder is dissolved in 20mL distilled water.
b) 1.25% Chitosan stock solution is prepared in 10% acetic acid by weighing 1.25 g of Chitosan and dissolving in 10 mL glacial acetic acid and further addition of 90 mL of demineralized water. This solution is stirred for 12-24 h, resulting in final concentration of chitosan to be 1.25 % and final volume to be 100 mL. 80 mL of this solution is used as is in the next step without further dilution.
c) Then 20mL DAP solution is added drop-wise to 80mL 1.25% chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11% DAP and 1% Chitosan.
7) 1.5% Chitosan
a) In a beaker, 11g of DAP powder is dissolved in 20mL distilled water.
b) 1.5 % Chitosan stock solution is prepared in 10% acetic acid by weighing 1.5 g of Chitosan and dissolving in 10 mL glacial acetic acid and further addition of 90 mL of demineralized water. This solution is stirred for 12-24 h, resulting in final concentration of chitosan to be 1.5 % and final volume to be 100 mL. 80 mL of this solution is used as is in the next step without further dilution.
c) Then 20mL DAP solution is added drop-wise to 80mL 1.5% chitosan solution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11% DAP and 1.2% Chitosan.

[0053] Example 5: Process for synthesis of nano DAP by addition of cross-linking agent (STPP) to chitosan by in-situ process (addition of STPP immediately after addition of DAP)
STPP is a common cross-linking agent for the synthesis of chitosan nanoparticles. In the present invention STPP’s cross-linking properties is used to form chitosan-DAP-nanoparticles. The STPP concentration has been varied from 0.25 % to 10% and Chitosan has also been varied from 0.25% to 1%. Below example demonstrates this at a particular concentration of 0.5% Chitosan and 0.5% STPP.
a) 0.5% Chitosan solution is prepared by dissolving 0.5 grams of chitosan powder in 10 mL glacial acetic acid and further diluting by deionized water to 100 mL total volume under stirring. The solution is further stirred for 24 h before use. 20 mL of this solution is used for further studies.
b) In a beaker, 4 g of DAP powder is dissolved in 10mL distilled water.
c) Then DAP solution is added drop-wise to 20mL 0.5% chitosan solution prepared in step 1. The solution is stirred on magnetic stirrer for uniform mixing.
d) Finally, 6mL of 0.5% STPP solution is added dropwise to 30mL of DAP-chitosan solution.
e) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11 % DAP and 0.4 % Chitosan.

[0054] Example 6: Process for synthesis of nano DAP by addition of cross-linking agent (STPP) to chitosan by ex-situ process (first formation of nanoparticles of Chitosan and then addition of DAP)
a) 1% Chitosan solution is prepared in 10% acetic acid by weighing 1 g of Chitosan and dissolving in 10 mL glacial acetic acid and further addition of 90 mL of demineralized water. This solution is stirred for 12-24 hrs. 20 mL of this solution is used as is in the next step without further dilution.
b) Firstly, 4mL of 1% STPP solution is added dropwise to 20mL of 1% chitosan solution and the solution is stirred for 15 mins.
c) To the above solution, 24mL DAP solution (prepared by dissolving 5.4 grams of DAP in demineralized water) is added.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11 % DAP and 0.4 % Chitosan.

[0055] Example 7: Process for synthesis of nano DAP using cross-linking agent Sokolan PA25 (polyacrylic acid) as chitosan-cross linking agent:
a) 0.5% Chitosan solution is prepared by dissolving 0.5 grams of chitosan powder in 10 mL glacial acetic acid and further diluting by deionized water to 100 mL total volume under stirring. The solution is further stirred for 24 h before use. 10 mL of this solution is used for further studies.
b) In a beaker, 2.147g of DAP powder is dissolved in 5mL distilled water.
c) Then DAP solution is added drop-wise to 10mL 0.5% chitosan solution. The solution is stirred on magnetic stirrer for uniform mixing.
d) Finally, 4mL of 0.1% Sokalan PA-25 solution is added dropwise to 15mL of DAP-chitosan solution.
e) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles.

[0056] Example 8: Process for synthesis of nano DAP by varying the molecular weight of Chitosan:
1) Chitosan oligosaccharides with Mol. Wt. ~ 5000 Da: Low molecular weight chitosan is typically referred as chitosan oligosaccharides. These are commercially available in 10% or 20% concentrated liquid forms. These can also be prepared in laboratory using nitric acid treatment of chitin or chitosan.
a) In a beaker, 2.5mL chitosan oligosaccharide is added to 97.5 mL distilled water to make final concentration as 0.5%.
b) In a beaker, 10g of DAP powder is dissolved in 20mL distilled water.
c) Then 20mL DAP solution is added drop-wise to 80mL 0.5% chitosan oligosaccharide solution and the solution is stirred for 15 mins.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 11% DAP and 0.4% Chitosan.
2) Chitosan with Mol. Wt. in the range 3,800-20,000 Da:
a) In a beaker, 10g of DAP powder is dissolved in 20mL distilled water.
b) 0.2% Chitosan solution is prepared in 0.5 % acetic acid by weighing 0.2 g of Chitosan and dissolving in 100 mL 0.5% acetic acid. This solution is stirred for 12-24 hrs.
c) Then 20mL DAP solution is added drop-wise to 80mL 0.2% chitosan solution and the solution is stirred for 15 mins.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 10% DAP and 0.16% Chitosan.
3) Chitosan with Mol. Wt. in the range ~ 50,000-1,90,000 Da:
a) In a beaker, 10g of DAP powder is dissolved in 20mL distilled water.
b) 0.2% Chitosan solution is prepared in 0.5 % acetic acid by weighing 0.2 g of Chitosan and dissolving in 100 mL 0.5% acetic acid. This solution is stirred for 12-24 hrs.
c) Then 20mL DAP solution is added drop-wise to 80mL 0.2% chitosan solution and the solution is stirred for 15 mins.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 10% DAP and 0.16% Chitosan.
4) Chitosan with Mol. Wt. in the range ~ 1,90,000-3,10,000 Da
a) In a beaker, 10g of DAP powder is dissolved in 20mL distilled water.
b) 0.2% Chitosan solution is prepared in 0.5 % acetic acid by weighing 0.2 g of Chitosan and dissolving in 100 mL 0.5% acetic acid. This solution is stirred for 12-24 hrs.
c) Then 20mL DAP solution is added drop-wise to 80mL 0.2% chitosan solution and the solution is stirred for 15 mins.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nano-particles which has a final concentration of 10% DAP and 0.16% Chitosan.

[0057] Example 9: Process for synthesis of nano urea using chitosan and cross-linking agent STPP:
a) In a beaker, 10g of urea powder is dissolved in 20mL distilled water.
b) 0.5 % Chitosan solution is prepared by dissolving 0.5 grams of Chitosan in 100 mL 10% acetic acid. To this solution, 0.6 mL of ammonium hydroxide solution (25-30% concentrated) is added under stirring.
c) Then urea solution is added drop-wise to 80mL of this 0.5% chitosan solution. The solution is kept on magnetic stirrer for uniform mixing and dissolution.
d) After complete addition, the mixture is stirred for 30 mins and 2 mL 10% STPP is added and the mixture further stirred for 15 minutes.
e) The resultant solution formed is colloidal dispersion of urea nano-particles which has a final concentration of 8.3% urea and 0.4% Chitosan.

[0059] Example 10: Synthesis of nano monoammonium phosphate (MAP) using chitosan
a) 0.5 % Chitosan solution is prepared by dissolving 0.5 grams of Chitosan in 100 mL 10% acetic acid.
b) In a beaker, 10g of MAP powder is dissolved in 20mL distilled water.
c) Then MAP solution is added drop-wise to 80mL 0.5% chitosan solution. The solution is kept on magnetic stirrer for uniform mixing and dissolution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of MAP nano-particles which has a final concentration of 10% MAP and 0.4% Chitosan.

[0060] Example 11: Synthesis of nano dipotassium phosphate (DKP) using Chitosan
a) 0.5 % Chitosan solution is prepared by dissolving 0.5 grams of Chitosan in 100 mL 10% acetic acid.
b) In a beaker, 10g of DKP powder is dissolved in 20mL distilled water.
c) Then DKP solution is added drop-wise to 80mL 0.5% chitosan solution. The solution is kept on magnetic stirrer for uniform mixing and dissolution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of DKP nano-particles which has a final concentration of 10% DKP and 0.4% Chitosan.

[0061] Example 12: Synthesis of nano Ammonium sulphate using Chitosan
a) 0.5 % Chitosan solution is prepared by dissolving 0.5 grams of Chitosan in 100 mL 10% acetic acid.
b) In a beaker, 10g of Ammonium sulphate powder is dissolved in 20mL distilled water.
c) Then this ammonium sulphate solution is added drop-wise to 80mL 0.5% chitosan solution. The solution is kept on magnetic stirrer for uniform mixing and dissolution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of ammonium sulphate nano-particles which has a final concentration of 10% ammonium sulphate and 0.4% Chitosan.

[0062] Example 13: Synthesis of nano potassium sulphate using Chitosan
a) 0.5 % Chitosan solution is prepared by dissolving 0.5 grams of Chitosan in 100 mL 10% acetic acid.
b) In a beaker, 10g of potassium sulphate powder is dissolved in 20mL distilled water.
c) Then this potassium sulphate solution is added drop-wise to 80mL 0.5% chitosan solution. The solution is kept on magnetic stirrer for uniform mixing and dissolution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of potassium sulphate nano-particles which has a final concentration of 10% potassium sulphate and 0.4% Chitosan.

[0063] Example 14: Synthesis of nano magnesium sulphate using Chitosan
a) 0.5 % Chitosan solution is prepared by dissolving 0.5 grams of Chitosan in 100 mL 10% acetic acid.
b) In a beaker, 10g of magnesium sulphate powder is dissolved in 20mL distilled water.
c) Then this magnesium sulphate solution is added drop-wise to 80mL 0.5% chitosan solution. The solution is kept on magnetic stirrer for uniform mixing and dissolution.
d) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of magnesium sulphate nano-particles which has a final concentration of 10% magnesium sulphate and 0.4% Chitosan.

[0064] Example 15: Synthesis of nano NPK blend using chitosan
A. Nano-(NH4)2SO4 nano-particles:
a) In a beaker, 10g of ammonium sulphate powder is dissolved in 20mL distilled water.
b) Then ammonium sulphate solution is added drop-wise to 80mL chitosan solution. The solution is kept on magnetic stirrer for uniform mixing and dissolution.
c) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nanoparticles.

B. Nano-MAP nano-particles:
a) In a beaker, 10g of MAP powder is dissolved in 20mL distilled water.
b) Then MAP solution is added drop-wise to 80mL chitosan solution. The solution is kept on magnetic stirrer for uniform mixing and dissolution.
c) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nanoparticles.

C. Nano-K2SO4 nano-particles:
a) In a beaker, 10g of potassium sulphate powder is dissolved in 20mL distilled water.
b) Then potassium sulphate solution is added drop-wise to 80mL chitosan solution. The solution is kept on magnetic stirrer for uniform mixing and dissolution.
c) After complete addition, the mixture is stirred for 30 mins and the resultant solution formed is colloidal dispersion of nanoparticles.

• Once all nano-particles are formed individually, 20mL of nano-MAP solution is added to 20mL nano-urea solution and finally 20mL nano-K2SO4 solution is added to nano-urea solution.
• The resultant solutions are stirred on magnetic stirrer for 30 mins for homogeneous mixing of the solutions.

[0065] From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the scope of the novel concepts of the present invention. It is to be understood that no limitations with respect to the specific embodiments illustrated is intended or should be inferred. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.