AU2020102586A4 - A process for synthesis of zinc oxide nano-particles - Google Patents
A process for synthesis of zinc oxide nano-particles Download PDFInfo
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Abstract
A PROCESS FOR SYNTHESIS OF ZINC OXIDE NANO
PARTICLES
The present invention relates to a green process using a benign solvent for
5 synthesis of zinc oxide nano-particles. The process comprising providing an
alkali solution and a capping agent, followed by admixing obtain a first
admixture thereof, sonicating the first admixture, adding a zinc containing
compound to the first admixture to obtain a second admixture, stirring and
sonicating the second admixture to obtain a reaction product, wherein the zinc
10 containing compound is added at a predetermined flow rate in a drop wise
manner, at a predetermined temperature, at a predetermined sonicating
frequency, and at a predetermined stirring speed, separating the reaction
product to obtain a solid product, washing the solid product with a fluid
medium to obtain a washed solid product, separating the washed solid product
15 to obtain a wet powder, removing the fluid medium from the wet powder to
obtain a dry powder comprising zinc oxide nano-particles.
FIG. 3(b)
1/4
FIG. 1(a) FIG. 1(b)
FIG. 2(a) FIG. 2(b)
Description
1/4
FIG. 1(a) FIG. 1(b)
FIG. 2(a) FIG. 2(b)
The present invention relates to zinc oxide nano-particles, and in particular to a process for synthesis of zinc oxide nano-particles, wherein the process is a green process as it employs benign solvent.
Nano-technology is growing every day rapidly as it finds numerous applications in multiple fields. One of the nano-particle which is of significance is zinc oxide nano-particle. Zinc oxide nano-particle is a "green" material that is biocompatible, biodegradable, and non-toxic for medical applications and environmental science.
Further, zinc oxide also finds application as a semiconductor material due to its wide band-gap energy of about 3.37 eV and large excitation binding energy of about 60 meV at room temperature. Still further, zinc oxide is of significance and finds promising applications in nanoscale devices, short wavelength light emitter, piezoelectric materials, optoelectronics, transparent conductors, field emission displays, solar cells, transducers, and all types of sensors. Additionally, zinc oxide is also a very effective photo-catalyst which can be applied to medical disinfection and in remediation of environmental pollutants.
At present, there exists a number of processes for synthesizing zinc oxide nano-particles. More specifically, due to large number of diverse type of applications, it is desired to synthesize zinc oxide nano-particles having multi-functional, complex, and tailor-made morphologies. One of such morphology of the zinc oxide nano-particles is zinc oxide nano-flowers. Other morphologies or shapes of zinc oxide nano-particles include nano wires, nano-belts, nano-rings, nano-tubes, nano-donuts, nano-propellers, self assembled nano-sheets, self-assembled nano-rods and different shaped nan flowers to mention a few.
These varied morphologies of the zinc oxide nano-particles are achieved by employing various processes for synthesizing the zinc oxide nano-particles. Various processes for synthesis of the zinc oxide nano-particles are known in the art, which includes, precipitation, micro-emulsion, solvothermal, chemical vapor deposition, hydrothermal method, sol-gel method, and electro-deposition.
However, these conventional processes have one or more disadvantages associated with them.
Some disadvantages of the conventional processes include that they employ strong reducing agents, use of non-aqueous solvents, require harsh reaction conditions, require long reaction time, consume high amount of energy, and need precise control of numerous process parameters.
Thus, there is felt a need for overcoming one or more drawbacks associated with the conventional processes for synthesis of zinc oxide nano-particles. More particularly, there is a need to provide a process for synthesizing the zinc oxide nano-particles which is environmentally friendly, and economic.
Some of the objects of the presently disclosed invention, of which at the minimum one object is fulfilled by at least one embodiment disclosed herein are as follows:
An object of the present invention is to provide an alternative, which overcomes at least one drawback encountered in the existing prior art;
Another object of the present invention is to provide a process for synthesizing zinc oxide nano-particles;
Still another object of the present invention is to provide a process for synthesizing zinc oxide nano-particles which are having nano-flower like morphology; and
Yet another object of the present invention is to provide a process for synthesizing zinc oxide nano-particles which is environmentally friendly, is simple, and is economic.
Other objects and benefits of the present invention will be more apparent from the following description which is not intended to bind the scope of the present invention.
The present invention discloses a process for synthesis of zinc oxide nano particles, wherein the process is a green process as it employs benign solvent.
In accordance with an embodiment of the present invention, the process comprising the steps of providing an alkali solution having a predetermined concentration, providing a capping agent, admixing the alkali solution and the capping agent having a predetermined ratio of the capping agent to the alkali solution to obtain a first admixture thereof, sonicating the first admixture, adding a zinc containing compound to the first admixture to obtain a second admixture, stirring and sonicating the second admixture to obtain a reaction product, wherein the zinc containing compound is added at a predetermined flow rate in a drop wise manner, at a predetermined temperature, at a predetermined sonicating frequency, and at a predetermined stirring speed, separating the reaction product to obtain a solid product, washing the solid product with a fluid medium to obtain a washed solid product, separating the washed solid product to obtain a wet powder, removing the fluid medium from the wet powder to obtain a dry powder comprising zinc oxide nano particles.
In accordance with an embodiment of the present invention, the alkali solution is sodium hydroxide solution, the predetermined concentration of the alkali solution is in the range of 0.2 M to 0.6 M, preferably the predetermined concentration is 0.4 M.
In accordance with an embodiment of the present invention, the capping agent is L-Histidine.
In accordance with an embodiment of the present invention, the first admixture is placed in a water bath, which being in contact with a source of ultra-sonic energy, and the predetermined sonicating frequency is in the range of 10 kHz to 30 kHz, preferably 22 kHz.
In accordance with an embodiment of the present invention, the predetermined ratio of the capping agent to the alkali solution is in the range of 0.01 to 0.1, preferably the predetermined ratio is 0.05.
In accordance with an embodiment of the present invention, the second admixture is stirred at a stirring speed in the range of 100 rpm to 400 rpm, preferably at 200 rpm.
In accordance with an embodiment of the present invention, the predetermined flow rate is in the range of 0.1 millilitre/minute to 5 millilitre/minute, preferably the predetermined flow rate is 1 millilitre/minute.
In accordance with an embodiment of the present invention, the predetermined temperature is in the range of 20 °C to 50 °C, preferably the predetermined temperature is 30 °C.
In accordance with an embodiment of the present invention, the sonication of the second admixture is carried out for a time period in the range of1 minute to 30 minutes, preferably 15 minutes.
In accordance with an embodiment of the present invention, the predetermined stirring speed is in the range of 100 rpm to 400 rpm, preferably at 200 rpm.
In accordance with an embodiment of the present invention, the step of separation of the reaction product is done by centrifugation at 5000 rpm for 5 minutes.
In accordance with an embodiment of the present invention, the fluid medium is a mixture of distilled water and ethanol, wherein the ratio of water to ethanol is 1:1.
In accordance with an embodiment of the present invention, the step of separation of the washed solid product is done by centrifugation at 5000 rpm for 5 minutes.
In accordance with an embodiment of the present invention, the fluid medium is removed from the wet powder by heating the wet powder at 60 °C for 12 hours.
In accordance with an embodiment of the present invention, the zinc oxide nano-particles have a size in the range of 1 nm to 10 nm.
The present invention will now be described with the help of the accompanying drawing, in which:
FIG. 1(a) illustrates a scanning electron microscope image of the zinc oxide nano-particles, and FIG. 1(b) illustrates the scanning electron microscope image of the zinc oxide nano-particles at higher magnification, which were obtained by employing the process of the present invention and with 5 mL/min flow rate of zinc acetate dihydrate;
FIG. 2(a) illustrates a scanning electron microscope image of the zinc oxide nano-particles, and FIG. 2(b) illustrates the scanning electron microscope image of the zinc oxide nano-particles at higher magnification, which were obtained by employing the process of the present invention and with 1 mL/min flow rate of zinc acetate dihydrate;
FIG. 3(a) illustrates a scanning electron microscope image of the zinc oxide nano-particles, and FIG. 3(b) illustrates the scanning electron microscope image of the zinc oxide nano-particles at higher magnification, which were obtained by employing the process of the present invention and with 1 mL/min flow rate of zinc acetate dehydrate;
FIG. 4 illustrates a scanning electron microscope image of the zinc oxide nano-particles, which were obtained by employing the process of the present invention and with 0.5 mL/min;
FIG. 5 (a), and 5(b) illustrates scanning electron microscope images of the zinc oxide nano-particles at lower and higher magnifications, respectively, which were synthesized by employing the normal precipitation process as described in the example 2;
FIG. 6(a), and FIG. 6(b) illustrates scanning electron microscope images of the zinc oxide nano-particles at lower and higher magnifications, respectively, which were synthesized by reverse homogeneous precipitation (RHP) process in accordance with the embodiments of the present invention;
FIG. 7(a), and FIG. 7(b) illustrates scanning electron images of the zinc oxide nano-particles at lower and higher magnifications, respectively, which were synthesized by the RHP process but without employing ultra-sound or without performing the ultra-sonication step; and
FIG. 8(a), and FIG. 8(b) illustrates scanning electron images of the zinc oxide nano-particles at lower and higher magnifications, respectively, which were synthesized by the RHP process along with sonication step (as described herein above with reference to example 1).
All the terms and expressions, which may be technical, scientific, or otherwise, as used in the present invention have the same meaning as understood by a person having ordinary skill in the art to which the present invention belongs, unless and otherwise explicitly specified.
In the present specification, and the claims, the articles "a," "an," and "the" include plural references unless the context clearly dictates otherwise.
The term "comprising" as used in the present specification and the claims will be understood to mean that the list following is non-exhaustive and may or may not include any other extra suitable features or elements or steps or constituents as applicable.
Further, the terms "about" or "approximately" used in combination with ranges relating to sizes of parts, or any other physical properties or characteristics, are meant to include small variations that may occur in the upper and/or lower limits of the ranges of the sizes.
The present invention relates to zinc oxide nano-particles, and in particular to a process for synthesis of zinc oxide nano-particles, wherein the process is a green process as it employs benign solvent.
In accordance with an embodiment of the present invention, a process for the synthesis of zinc oxide nano-particles is disclosed, wherein the process includes the following steps, which are described herein below:
In accordance with the present invention an alkali solution having a predetermined concentration is provided. In accordance with an embodiment of the present invention, the alkali solution is sodium hydroxide solution. In accordance with an embodiment of the present invention, the predetermined concentration of the alkali solution is in the range of 0.2 M to 0.6 M. In one preferred embodiment, the predetermined concentration of the alkali solution is 0.4 M.
In accordance with the present invention, a capping agent is provided. In accordance with one embodiment of the present invention, the capping agent is L-Histidine. In accordance with one embodiment the concentration of the capping agent is in the range of 0.01 M to 0.03 M. In one preferred embodiment, the concentration of the capping agent is 0.02 M.
The alkali hydroxide solution and the capping agent are then admixed in a predetermined ratio of the capping agent to the alkali solution to obtain a first admixture thereof. In accordance with one embodiment of the present invention, the predetermined ratio of the capping agent to the alkali solution is in the range of 0.01 to 0.10. In a preferred embodiment, the predetermined ratio of the capping agent to the alkali solution is 0.05. Preferably, the first admixture is kept in a reactor such as a glass reactor, and the glass reactor is placed in a water bath, wherein the temperature of the water bath is controlled using a temperature controller. A source of ultra-sound is provided which is coupled suitably to the water bath, such that the first admixture can be sonicated.
In the next step, the first admixture so obtained is sonicated using the source of ultra-sound at a predetermined frequency and at a pre-determined power of the ultra-sound. In accordance with one embodiment of the present invention, the predetermined frequency of the ultra-sound is in the range of 10 kHz to 30 kHz. In one preferred embodiment, the predetermined frequency of the ultra-sound is 22 kHz. Further, in accordance with one embodiment of the present invention, the pre-determined power of the ultra-sound is in the range of 50 Watts to 300 Watts. In one preferred embodiment, the pre determined power of the ultra-sound is 100 Watts. In another preferred embodiment, the pre-determined power of the ultra-sound is 200 Watts.
In accordance with an embodiment of the present invention, a zinc containing compound is added to the first admixture to obtain a second admixture. In a preferred embodiment the zinc containing compound is added to the first mixture at predetermined flow rate and in a drop wise manner at a predetermined temperature, at a predetermined sonicating frequency, and at a predetermined stirring speed. The second admixture is stirred and sonicated to obtain a reaction product. In contrast to the conventional processes, wherein the alkali solution is added to the zinc containing compound (also referred to as normal precipitation herein), in the present application, zinc containing compound is added to the alkali solution in drop wise manner (referred to as reverse homogeneous precipitation herein). This step of adding the zinc containing compound to the alkali solution in drop wise manner provides an advantage that the zinc oxide nano-particles so synthesized are having a particle size distribution which is narrow. In accordance with one embodiment of the present invention, the zinc oxide nano-particles have a size in the range of 1 nm to 10 nm. Further, the use of ultra-sonic or ultra sound in addition to the controlled addition of the zinc containing compound to the alkali solution along with the pre-determined concentrations aid in generation of a synergistic effect, which facilitates in control of the size of the zinc oxide nano-particles along with the morphology of the zinc oxide nano particles.
In accordance with one embodiment of the present invention, the second admixture is stirred at a stirring speed in the range of 100 rpm to 400 rpm. In a preferred embodiment, the second admixture is stirred at 200 rpm.
In accordance with one embodiment of the present invention, the predetermined flow rate of the zinc containing compound which is being added to the alkali solution is in the range of 0.1 millilitre/minute to 5 millilitre/minute. In one preferred embodiment, the predetermined flow rate of the zinc containing compound which is being added to the alkali solution is 1 millilitre/minute.
In accordance with one embodiment of the present invention, the predetermined temperature at which the water bath and hence the reactants in the reactor are maintained is in the range of 20 °C to 50 °C. In one preferred embodiment, the predetermined temperature is 30 °C.
In accordance with one embodiment of the present invention, the zinc containing compound is zinc acetate dihydrate (Zn (CH 3 CO 2 ) 2 , 2H20).
In accordance with one embodiment of the present invention, the sonication of the second admixture is carried out for a time period in the range of 1 minute to 30 minutes. In one preferred embodiment, the sonication of the second admixture is carried out for a time period of 15 minutes.
In the next step, the reaction product so obtained is separated to obtain a solid product. In accordance with one embodiment of the present invention, the step of separation of the reaction product is done by centrifugation. In one embodiment the centrifugation is carried out at 5000 rpm for 5 minutes.
The solid product so obtained is then washed with a fluid medium to obtain a washed solid product. In accordance with one embodiment of the present invention, the fluid medium is a mixture of distilled water and ethanol. In one embodiment, the ratio of water to ethanol is 1:1.
The fluid medium is then removed from the washed solid product to obtain a wet powder. The step of removal of the fluid medium is carried out by known methods such as centrifugation. In one embodiment the washed solid product is centrifuged at 5000 rpm for 5 minutes to obtain the wet powder.
The wet powder is then freed of any fluid medium contained in it to obtain dry powder comprising zinc oxide nano-particles. In accordance with an embodiment of the present invention, the fluid medium is removed from the wet powder by heating the wet powder at 60 °C for 12 hours. The temperature and the time period of drying the wet powder depends on the amount of fluid medium contained in the wet powder.
The present invention is now described with reference to the following examples, wherein the examples are provided for a clear understanding of the process of the present invention and not for limiting the scope thereof.
InA
Examples:
Example 1 (in accordance with the embodiments of the present invention):
Experimental setup:
The experimental setup comprised of a glass reactor of 50 mL capacity and having an internal diameter of 4 cm. The glass reactor was equipped with a four-blade turbine impeller. The glass reactor was immersed in an ultra sonication water bath, which was maintained at desired temperature (30°C) with an accuracy of 5°C. The glass reactor was positioned at a distance of 2.54 cm above the bottom of the water bath where highest cavitation intensity was achieved. The reaction temperature was controlled with the help of a temperature controller. The glass reactor was also equipped with a dropping funnel to provide a controlled flow of reactants. The agitation was provided by means of an electric motor having provision for speed control (agitation speed 200 rpm).
In accordance with the present invention, the process involves reverse homogeneous precipitation (RHP), wherein an acidic solution of metal salt was added drop wise to a basic solution of alkaline aqueous solution, in contrast to normal precipitation process wherein an alkaline aqueous solution is added to solution of metal salt, which has a disadvantage that it allows a large pH window and lead to formation of nano-particles of irregular size distribution.
The process of synthesizing the zinc oxide nano-particles included the following steps:
Step 1: providing a solution of sodium hydroxide (0.4 M);
Step 2: providing L-histidine as capping agent (0.2 M);
1 1
Step 3: admixing the solution of sodium hydroxide and L-histidine in the glass reactor to obtain a first admixture thereof;
Step 4: sonicating the first admixture using the ultra-sonicator at 22 kHz and 100 watts;
Step 5: adding the zinc acetate dihydrate to the first admixture in a drop wise manner with control flow. The total volume was maintained at 50 mL and 1:2 reactant ratio of zinc acetate dihydrate to sodium hydroxide (0.2:0.4M). was maintained.
Step 6: Ultra-sound irradiation was started (100 W, 22 kHz, 100 % duty cycle) at the time of beginning of addition of zinc acetate dihydrate, and kept for 15 minutes.
The reactions were carried out at different conditions as summarized in Table 1 herein below. Zinc acetate dihydrate reacts with sodium hydroxide instantaneously forming white precipitation (the reaction product).
Step 7: The obtained precipitate (reaction product) was centrifuged at 5000 rpm for 5 min for removal of the by-product, wherein the by-product is sodium acetate which is formed is benign to obtain a solid product.
Step 8: The solid product so obtained after centrifugation was washed with a mixture of demonized water and ethanol (in 1:1 ratio) to obtain washed solid product.
Step 9: The washed solid product was then centrifuged at 5000 rpm for 5 min to remove the fluid medium or the mixture of deionized water and ethanol to obtain a wet powder.
Step 10: The wet powder so obtained was dried in hot air oven at 60°C for 12 hours to obtain a powder of zinc oxide nano-particles having nano-flower like morphology.
(This procedure holds good for Runs 1, 2, 3, 4, 6, and 8. Run 7 was performed with all steps same as mentioned herein above, but, the step of ultra sonication was not performed).
TABLE 1
1 50 0.2 10 1 5 0.4 40 0.5 - 0.02 200 22 100 15
2 50 0.2 10 1 1 0.4 40 0.5 - 0.02 200 22 100 15
3 50 0.2 15 0.66 1 0.4 35 0.57 - 0.02 200 22 100 15
4 50 0.2 15 0.66 0.5 0.4 35 0.57 - 0.02 200 22 100
50 0.2 35 0.28 - 0.4 15 1.33 1 0.02 200 - - 15
6 50 0.2 15 0.66 1 0.4 35 0.57 - - 200 22 100 15
7 50 0.2 35 0.28 - 0.4 15 1.33 1 0.02 200 - - 15
8 50 0.2 15 0.66 1 0.4 35 0.57 - - 200 22 100 15
R-Run
T- Total volume (mL) ZAD - Zinc Acetate dihydrate A -Amount (mole) V- Volume (mL) C - Concentration (mole-) F- Feeding rates (mL/min) SH- Sodium hydroxide HI - Histidine (mole) AS - Agitation speed (rpm) USF - Ultra-soundfrequency(kHz) USP - Ultra-soundpower (watts)
T'- Time (min) 50 % Duty cycle
*1 % glycoside
Example 2 (comparative example - not in accordance with the embodiments of the present invention - Run 5):
For comparative study, Normal Precipitation (NP) was carried out in which an aqueous solution of sodium hydroxide (15 mL, 0.2 M) was fed drop wise with control flow (lmL/min) into zinc acetate solution (35mL, 0.4 M). Further, Sonochemical Normal Precipitation (SNP) was also carried out (Run 6) in a manner as described herein above with reference to example 1.
Ultra-sound irradiation was started at the time of addition of aqueous solution of sodium hydroxide. Total volume was maintained of 50 mL and 1:2 reactant ratio of zinc acetate to sodium hydroxide (0.2:0.4M) for all the experimental conditions.
Zinc Acetate dihydrate reacts instantaneously with sodium hydroxide, in this reaction sodium hydroxide in reagent was in excess. Therefore, to determine the reaction time, sodium hydroxide which remained in excess was titrated. For this purpose, sodium hydroxide was standardized against oxalic acid (0.1 M) and the titration was carried for samples which were drawn at 5 minutes time interval up to 60 minutes to determine the concentration of reactant in excess. Concentration of sodium hydroxide in excess in a reaction with zinc acetate dihydrate was determine by calculating molarities of various samples for different reaction sets and from these values optimum reaction time 15 minutes was determined and 100 % duty cycle was maintained.
The so obtained zinc oxide nano-particles in example 1 were characterized for various parameters.
Run 1: (5 mL/min): FIG. 1(a) illustrates a scanning electron microscope image of the zinc oxide nano-particles, and FIG. 1(b) illustrates the scanning electron microscope image of the zinc oxide nano-particles at higher magnification, which were obtained by employing the process of the present invention and with 5 mL/min flow rate of zinc acetate dehydrate. It is evident
1 A from FIG. 1(a), and FIG. 1(b) that the zinc oxide nano-particles were mono dispersed.
Run 2: (1 mL/min): FIG. 2(a) illustrates a scanning electron microscope image of the zinc oxide nano-particles, and FIG. 2(b) illustrates the scanning electron microscope image of the zinc oxide nano-particles at higher magnification, which were obtained by employing the process of the present invention and with 1 mL/min flow rate of zinc acetate dihydrate. It is evident from FIG. 2(a), and FIG. 2(b) that the zinc oxide nano-particles have flower like morphology.
Run 3: (1 mL/min): FIG. 3(a) illustrates a scanning electron microscope image of the zinc oxide nano-particles, and FIG. 3(b) illustrates the scanning electron microscope image of the zinc oxide nano-particles at higher magnification, which were obtained by employing the process of the present invention and with 1 mL/min flow rate of zinc acetate dihydrate. It is evident that due to decreased concentration and flow rate of zinc ions, the zinc oxide nano-particles having morphology which was between flower-like and snow flake like morphology was observed.
Run 4: (0.5 mL/min): FIG. 4 illustrates a scanning electron microscope image of the zinc oxide nano-particles, which were obtained by employing the process of the present invention and with 0.5 mL/min, wherein fine snow flake like zinc oxide nano-particles were obtained, which confirms that the flow rate and lower concentration of zinc acetate contributes for such fine structure.
Run 5: FIG. 5 (a), and 5(b) illustrates scanning electron microscope images of the zinc oxide nano-particles at lower and higher magnifications, respectively, which were synthesized by employing the normal precipitation process as described in the example 2 herein above, wherein the alkali aqueous solution is added to the aqueous zinc acetate dihydrate solution. It is
IC evident from the FIG. 5(a), and FIG. 5(b) that the zinc oxide nano-particles obtained are having large size and non-uniform shape, which is not desired.
Run 6: FIG. 6(a) and FIG. 6(b) illustrates scanning electron microscope images of the zinc oxide nano-particles at lower and higher magnifications, respectively, which were synthesized by the reverse homogeneous precipitation (RHP) process in accordance with the embodiments of the present invention, wherein the acidic solution of zinc acetate dihydrate is added in drop wise manner to the sodium hydroxide solution, in contrast to the conventional normal precipitation process. From FIG. 6(a), and FIG. 6(b) it is clear that the zinc oxide nano-particles exhibit distinguishable organized clusters with average particle size of 401.52 nm and 70 nm diameter. This is attributed to the RHP process, wherein it is anticipated that the RHP process leads to gradual change in pH when zinc acetate dihydrate is added in drop wise manner (at 1 mL/min flow rate) slowly forming zinc hydroxide as Zn 2 dissolved in the aqueous solution of zinc acetate dihydrate reacts with dispersed OH- ions in aqueous solution of NaOH.
Run 7: Without ultra-sound: FIG. 7(a), and FIG. 7(b) illustrates scanning electron images of the zinc oxide nano-particles at lower and higher magnifications, respectively, which were synthesized by the RHP process but without employing ultra-sound or without performing the ultra-sonication step. From FIG. 7(a), and FIG. 7(b) it is clear that no fine nano-particles are obtained.
Run 8: With ultra-sound: FIG. 8(a), and FIG. 8(b) illustrates scanning electron images of the zinc oxide nano-particles at lower and higher magnifications, respectively, which were synthesized by the RHP process along with sonication step (as described herein above with reference to example 1). From FIG. 8(a), and FIG. 8(b) it is clear that flower-like morphology of the zinc oxide nano-particles is achieved and compared to FIG. 7(a), and FIG. 7(b).
I1C
Thus, this sufficiently proves that sonication does affect the formation of zinc oxide nano-particles, and its morphology.
The presently disclosed invention, as described herein above, provides several technical advances and advantages including, but not limited to, a process for synthesizing zinc oxide nano-particles, wherein the process:
- is a green process;
- is employs benign solvents;
- is does not produce hazardous waste;
- is economic;
- is energy efficient as the process is carried out at room temperature and atmospheric pressure;
- employs less harmful reactants;
- produces less harmful by-products which can be easily recycled as they are bio-degradable; and
- is less time consuming.
1 17
Claims (5)
1. A process for synthesis of zinc oxide nano-particles, said process comprising the following steps:
- providing an alkali solution having a predetermined concentration;
- providing a capping agent;
- admixing said alkali solution and said capping agent having a predetermined ratio of said capping agent to said alkali solution to obtain a first admixture thereof;
- sonicating said first admixture;
- adding a zinc containing compound to said first admixture to obtain a second admixture;
- stirring and sonicating said second admixture to obtain a reaction product, wherein said zinc containing compound is added at a predetermined flow rate in a drop wise manner, at a predetermined temperature, at a predetermined sonicating frequency, and at a predetermined stirring speed;
- separating said reaction product to obtain a solid product;
- washing said solid product with a fluid medium to obtain a washed solid product;
- separating said washed solid product to obtain a wet powder;
- removing said fluid medium from said wet powder to obtain a dry powder comprising said zinc oxide nano-particles.
2. The process as claimed in claim 1, wherein said alkali solution is sodium hydroxide solution, and wherein said predetermined concentration of said alkali solution is in the range of 0.2 M to 0.6 M, preferably said predetermined concentration is 0.4 M.
3. The process as claimed in claim 1, wherein said capping agent is L Histidine.
4. The process as claimed in claim 1, wherein said first admixture is placed in a water bath, which being in contact with a source ofultra-sonic energy, and said predetermined sonicating frequency is in the range of 10 kHz to 30 kHz, preferably, the step of sonicating said first mixture is carried out at a frequency of 22 kHz.
5. The process as claimed in claim 1,
- wherein said predetermined ratio of said capping agent to said alkali solution is in the range of 0.01 to 0.10, preferably said predetermined ratio is 0.05;
- wherein said second admixture is stirred at a stirring speed in the range of 100 rpm to 400 rpm, preferably at 200 rpm;
- wherein said predetermined flow rate is in the range of 0.1 millilitre/minute to 5 millilitre/minute, preferably said predetermined flow rate is 1 millilitre/minute;
- wherein said predetermined temperature is in the range of 20°C to 50
°C, preferably said predetermined temperature is 30 °C;
- wherein the sonication of said second admixture is carried out for a time period in the range of 1 minute to 30 minutes, preferably 15 minutes;
- wherein said predetermined stirring speed is in the range of 100 rpm to 400 rpm, preferably at 200 rpm;
- wherein the step of separation of said reaction product is done by centrifugation at 5000 rpm for 5 minutes; and
- wherein said fluid medium is a mixture of distilled water and ethanol, wherein the ratio of water to ethanol is 1:1;
- wherein the step of separation of said washed solid product is done by centrifugation at 5000 rpm for 5 minutes;
- wherein said fluid medium is removed from said wet powder by heating said wet powder at 60 °C for 12 hours; and
- wherein said zinc oxide nano-particles have a size in the range of 1 nm to 10 nm.
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| IN202021021014 | 2020-05-19 |
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| AU2020102586A4 true AU2020102586A4 (en) | 2020-11-19 |
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2020
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