阅读说明：本技术 一种磁性异质体纳米材料及其制备方法 (Magnetic heteroplasmon nano material and preparation method thereof ) 是由 许月阳 薛建明 朱法华 刘瑞江 王宏亮 柏源 徐振 蔡彦吟 石丽娜 于 2021-10-09 设计创作，主要内容包括：本发明属于无机非金属纳米复合材料制备技术领域,具体涉及一种异质体纳米片及其制备方法。本发明公开了一种原料组合物,包括三价铁盐和磷酸二氢盐,其中三价铁离子和磷酸根离子摩尔比(2-6):1,将原料组合物制成溶液经水热反应和还原剂煅烧后,获得Fe-(3)O-(4)/α-Fe-(2)O-(3)磁性异质体纳米片,本发明水热煅烧制备磁性异质体纳米片的原料来源广泛,成本低廉,工艺流程简单,操作简便,对所需设备要求不高,所得产品形态规则,产率高,适于工业化规模生产,饱和磁化强度达31-51emu/g,具有广泛的应用。(The invention belongs to the technical field of preparation of inorganic nonmetal nano composite materials, and particularly relates to a heterogeneous nanosheet and a preparation method thereof. The invention discloses a raw material composition, which comprises ferric iron salt and dihydric phosphate, wherein the molar ratio of ferric iron ions to phosphate ions is (2-6):1, the raw material composition is prepared into a solution, and the solution is subjected to hydrothermal reaction and calcination by a reducing agent to obtain Fe 3 O 4 /α‑Fe 2 O 3 Magnetic heteroplasmon nanosheets, hydrothermal process of the inventionThe magnetic heteroplasmon nanosheet prepared by calcination has the advantages of wide raw material source, low cost, simple process flow, simple and convenient operation, low requirement on required equipment, regular shape of the obtained product, high yield, suitability for industrial mass production, saturation magnetization of 31-51emu/g and wide application.)

1. A raw material composition for synthesizing a magnetic heteroplasmon nano-material is characterized by comprising ferric salt and dihydrogen phosphate, wherein the molar ratio of ferric ions to phosphate ions is (2-6): 1.

2. The feed composition of claim 1, wherein the ferric salt comprises ferric chloride or/and ferric nitrate, and the dihydrogen phosphate comprises one or more of ammonium dihydrogen phosphate, sodium dihydrogen phosphate, or potassium dihydrogen phosphate.

3. A method for preparing magnetic heteroplasmon nano-materials using the raw material composition of claim 1 or 2, comprising the steps of:

s1, dissolving ferric iron salt and dihydric phosphate in a solvent according to the molar ratio of (2-6) to 1 of ferric iron ions and phosphate ions, and preparing a precursor solution at room temperature;

s2, carrying out hydrothermal reaction on the precursor solution, and separating a primary product;

s3 adding a reducing agent into the primary product, and carrying out temperature programming to 450-700 ℃ for calcination for 2-8 h.

4. The method for preparing magnetic heteroplasmon nanomaterial according to claim 3, wherein the precursor solution in step S1 uses water as solvent.

5. The method for preparing magnetic heteroplasmon nanomaterial according to claim 3 or 4, wherein the hydrothermal reaction in step S2 is carried out in a hydrothermal kettle at a temperature of 200 ℃ and 220 ℃ for a constant temperature of 12-24 h.

6. The method for preparing magnetic heteroplasmon nanomaterial according to any of claims 3-5, wherein in step S2, the mixture is ultrasonically mixed with absolute ethanol or ionized water and undergoes hydrothermal reaction to obtain solid, and the solid is centrifuged at 10000rad/min for 5-6 times (5-10 min each) in 5000-.

7. The method for preparing magnetic heteroplasmon nanomaterial according to any of claims 3-6, wherein the reducing agent in step S3 comprises polyvinylpyrrolidone (PVP).

8. The method for preparing magnetic heteroplasmon nanomaterial according to any of claims 3-7, wherein the mass ratio of the primary product to the reducing agent in step S3 is 1 (2-8).

9. The magnetic heteroplasmon nanosheet material is characterized by being nanosheet, and the molecular formula is Fe₃O₄/α-Fe₂O₃The composition is prepared from the raw material composition of claim 1 or 2 or the preparation method of any one of claims 3 to 8.

10. The magnetic heteroplasmon nanoplatelet of claim 9, wherein the average diameter of the magnetic heteroplasmon nanoplatelet is 153-292nm and the average thickness is 29-44 nm.

Technical Field

The invention belongs to the technical field of preparation of inorganic nonmetal nano composite materials, and particularly relates to a magnetic heteroplasmon nano material and a preparation method thereof.

Background

In recent years, research on nanoscience and nanotechnology has been greatly developed. Due to the unique physical and chemical properties of the nano material, including surface effect, catalytic performance, dielectric confinement, quantum effect and the like, the nano material has wide application in the aspects of ecological environment, biomedicine, electronic information, engineering application, photoelectricity and the like. The crystal form, the particle size and the morphology of the material have great influence on the performance of the material. Because the specific surface area of the nano material with the sheet structure is higher, the structure characteristics enable the nano material to expose more active sites, and the reaction performance is improved.

Iron oxide is a transition metal oxide which is non-toxic, harmless and widely present in the natural environment. Wherein, alpha-Fe₂O₃Has low biotoxicity, high corrosion resistance and excellent thermodynamic stability, thereby having potential research value. However, alpha-Fe₂O₃Is weak, which limits to some extentIt has a wide range of research and applications. To overcome this limitation, Fe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nanoplates were prepared. The nano sheet has controllable magnetic size, is not easy to agglomerate, is safe and environment-friendly, and has high catalytic performance and good biocompatibility.

The particle size and morphology of the nano iron oxide can be regulated and controlled by different synthesis methods at present, including hydrolysis method, coprecipitation method, hydrothermal method, solvothermal method, ionic liquid-assisted synthesis method, thermal decomposition method, combustion oxidation method and sol-gel method. However, it is reported that Fe is produced₃O₄/α-Fe₂O₃The magnetic heteroplasmon nano-sheet has few documents, and the preparation method is complex, long in period and high in cost, needs a surfactant or a toxic solvent, and is not beneficial to industrial production.

The prior Chinese patent document CN111847524 discloses Fe₃O₄/Fe₂O₃Magnetic heteroplasmon nanotube and its preparation method by controlling reducing sugar and alpha-Fe₂O₃The proportion of the nanotube, the calcination temperature and the calcination time are controlled; the product has stronger magnetism, regular shape and good stability, and is not easy to agglomerate, but the preparation of Fe by adopting metal salt and other more original materials is only reported₃O₄/α-Fe₂O₃The report of magnetic heteroplasmon nanometer, prior art CN105417517 discloses that soluble iron salt and metal ion-free phosphorus source solution are adopted, polyvinylpyrrolidone is used as surfactant to prepare iron phosphate material, but the prepared iron phosphate material is of a tremella type and is difficult to reach an ideal form.

Disclosure of Invention

Therefore, the technical problem to be solved by the present invention is to overcome the Fe in the prior art₃O₄/α-Fe₂O₃The defect of the preparation process of the magnetic heteroplasmon nano-sheet is that the Fe is prepared by adopting a hydrothermal calcination method₃O₄/α-Fe₂O₃The magnetic heteroplasmon nanosheet overcomes the defects of long period, high cost and the like of the existing preparation method, and provides the magnetic heteroplasmon nanosheet which is simple and convenient to operate, low in cost, green and environment-friendly and capable of realizing large-scale industrial productionFe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nano-sheet and its preparation method.

The details are as follows:

the invention discloses a raw material composition for synthesizing a magnetic heteroplasmon nano material, which comprises ferric salt and dihydric phosphate, wherein the molar ratio of ferric ions to phosphate ions is (2-6): 1.

Further, the ferric salt comprises ferric chloride or/and ferric nitrate, and the dihydrogen phosphate comprises one or more of ammonium dihydrogen phosphate, sodium dihydrogen phosphate or potassium dihydrogen phosphate.

The invention also discloses a method for preparing the magnetic heteroplasmon nano material by using the raw material composition, which comprises the following steps:

s1, dissolving ferric iron salt and dihydric phosphate in a solvent according to the molar ratio of (2-6) to 1 of ferric iron ions and phosphate ions, and preparing a precursor solution at room temperature;

s2, carrying out hydrothermal reaction on the precursor solution, and separating a primary product;

s3 adding a reducing agent into the primary product, and carrying out temperature programming to 450-700 ℃ for calcination for 2-8 h.

Further, in step S1, the precursor solution uses water as a solvent.

Further, the hydrothermal reaction in the step S2 is carried out in a hydrothermal kettle, the temperature is maintained at 200-220 ℃, and the constant temperature time is 12-24 h.

Further, in step S2, anhydrous ethanol or ionized water is adopted to be ultrasonically mixed uniformly and then subjected to hydrothermal reaction to obtain a solid, and the solid is centrifuged at 10000rad/min for 5-6 times (5-10 min each time) to obtain a primary product.

Further, the reducing agent in step S3 includes polyvinylpyrrolidone (PVP).

Further, the mass ratio of the primary product to the reducing agent in the step S3 is 1 (2-8).

The invention also discloses a magnetic heteroplasmon nanosheet material, which is nanosheet-shaped, and has a molecular formula of Fe₃O₄/α-Fe₂O₃From the above-mentioned raw material composition orThe preparation method is used for preparing the medicine.

Furthermore, the average diameter of the magnetic heteroplasmon nano-sheet is 153-292nm, and the average thickness is 29-44 nm.

The technical scheme of the invention has the following advantages:

1. the invention discloses a raw material composition which comprises ferric iron salt and dihydric phosphate, wherein the molar ratio of ferric iron ions to phosphate ions is (2-6):1, the source is wide, the price is low, and the raw material composition is green and environment-friendly.

2. The invention also discloses a preparation method for preparing the magnetic heteroplasmon nano material, and Fe is prepared by adopting a hydrothermal calcination method₃O₄/α-Fe₂O₃The magnetic heteroplasmon nanosheets are prepared from only trivalent ferric salt, dihydric phosphate and polyvinylpyrrolidone (PVP) as raw materials for the first time, and the preparation method and the process have novel steps and are simple and convenient to operate; the requirement on required equipment is not high, the efficiency is high, and the process is easy to control; in the whole process flow, polyvinylpyrrolidone (PVP) is used as a reducing agent, so that the process is safe; the reaction process can prepare nano-sheets with different sizes by controlling three parameters of the proportion of ferric salt and dihydric phosphate, the hydrothermal temperature and the hydrothermal time, and can prepare Fe with different performances by controlling the consumption of polyvinylpyrrolidone (PVP), the calcination temperature and the calcination time₃O₄/α-Fe₂O₃A magnetic heteroplasmon nanoplatelet; the product has uniform distribution, regular shape, strong magnetism and difficult agglomeration. In addition, Fe prepared by the method₃O₄/α-Fe₂O₃The magnetic heteroplasmon nano-sheet has larger specific surface area, and is beneficial to better applying the magnetic heteroplasmon nano-sheet to the research of ecological environment.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 shows Fe prepared in example 1₃O₄/α-Fe₂O₃X-ray diffraction pattern and alpha-Fe of magnetic heteroplasmon nanosheet₂O₃Standard PDF card (JCPDS No.89-0596) and Fe₃O₄A standard PDF card (JCPDS No.75-0449) comparison graph;

FIG. 2 shows Fe prepared in example 1₃O₄/α-Fe₂O₃Scanning electron microscope photos of the magnetic heteroplasmon nano-sheet, wherein the size of the scale in the graph is 100 nm;

FIG. 3 is Fe prepared in example 2₃O₄/α-Fe₂O₃And (3) a transmission electron microscope photo of the magnetic heteroplasmon nanosheet, wherein the scale size in the graph is 100 nm.

Detailed Description

The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.

The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps and conditions described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.

Example 1

0.541g (2.001mmol) of ferric trichloride hexahydrate and 0.094g (0.602mmol) of sodium dihydrogen phosphate dihydrate are weighed and added into 80mL of deionized water, and the mixture is stirred until the mixture is completely dissolved to obtain a precursor solution. Placing the precursor solution in a hydrothermal kettle, heating to 220 deg.C, maintaining the temperature for 24 hr, cooling to room temperature, adding deionized water into the obtained product, ultrasonically mixing, centrifuging at rotation speed of 10000rad/min for 6 times, 5min each time, removing supernatant, transferring the product to a vacuum drying oven to obtain initial product, weighing 0.4g polyvinylpyrrolidone (PVP) and dried 0.2g initial productAdding the materials into a crucible, uniformly mixing, calcining the crucible in a programmed temperature control furnace at 600 ℃ for 4h, and taking out the solid in the crucible when the temperature of the programmed temperature control furnace is reduced to room temperature to obtain Fe₃O₄/α-Fe₂O₃A magnetic heteroplasmon nanoplatelet; prepared Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 260nm, the average thickness is 36nm, and the saturation magnetization is 38 emu/g.

Fe prepared under the conditions described in this example₃O₄/α-Fe₂O₃X-ray diffraction pattern and alpha-Fe of magnetic heteroplasmon nanosheet₂O₃Standard PDF card (JCPDS No.89-0596) and Fe₃O₄The comparison graph of the standard PDF card (JCPDS No.75-0449) is shown in FIG. 1; as can be seen from the figure, most of the diffraction peak positions and alpha-Fe of the product₂O₃The standard PDF card diffraction peak positions correspond to each other; at the same time, Fe₃O₄/α-Fe₂O₃The diffraction peak proportion of the magnetic composite nano rod at two diffraction angles of 33 degrees and 35.6 degrees is obviously higher than that of the standard Fe₂O₃The diffraction intensity ratio of (2) is small, and the Fe at 35.7 DEG is also shown₃O₄The presence of diffraction peaks.

Fe prepared under the conditions described in this example₃O₄/α-Fe₂O₃The scanning electron micrograph of the magnetic heteroplasmon nanosheet is shown in fig. 2; by statistical analysis, Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 260nm, and the average thickness is 36 nm.

Example 2

0.541g (2.001mmol) of ferric trichloride hexahydrate and 0.038g (0.330mmol) of ammonium dihydrogen phosphate are weighed and added into 80mL of deionized water, and stirred until complete dissolution is achieved, so as to obtain a precursor solution. Placing the precursor solution in a hydrothermal kettle, heating to 220 deg.C, maintaining the temperature for 24 hr, cooling to room temperature, adding alcohol to the obtained product, ultrasonically mixing, centrifuging at rotation speed of 10000rad/min for 6 times, 5min each time, removing supernatant, transferring the product to a vacuum drying oven, weighing 0.2g polyvinylpyrrolidone (PVP) and dried 0.1g solidAdding into a crucible, mixing, calcining at 600 deg.C for 2 hr, and taking out the solid to obtain Fe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nanoplatelets. Prepared Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 153nm, the average thickness is 44nm, and the saturation magnetization is 51 emu/g.

Fe prepared under the conditions described in this example₃O₄/α-Fe₂O₃The transmission electron micrograph of the magnetic heteroplasmon nanosheet is shown in fig. 3; by statistical analysis, Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 153nm, and the average thickness is 44 nm.

Example 3

0.541g (2.001mmol) of ferric trichloride hexahydrate and 0.051g (0.443mmol) of ammonium dihydrogen phosphate are weighed and added into 80mL of deionized water, and stirred until complete dissolution is achieved, so that a precursor solution is obtained. Placing the precursor solution in a hydrothermal kettle, heating to 220 ℃, keeping the temperature for 24h, cooling to room temperature, adding deionized water or alcohol into the obtained product, ultrasonically mixing, centrifuging at a rotation speed of 10000rad/min in the centrifuging step for 5 times, 10min each time, removing supernatant, transferring the product into a vacuum drying oven, weighing 0.6g of polyvinylpyrrolidone (PVP) and 0.1g of dried solid, adding the mixture into a crucible, mixing, placing the crucible in a programmed temperature control furnace, calcining at 600 ℃ for 6h, and taking out the solid in the crucible when the temperature of the programmed temperature control furnace is reduced to room temperature to obtain Fe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nanoplatelets. Through statistical analysis, prepared Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 198nm, the average thickness is 40nm, and the saturation magnetization is 41 emu/g.

Example 4

0.541g (2.001mmol) of ferric trichloride hexahydrate and 0.156g (0.999mmol) of sodium dihydrogen phosphate dihydrate are weighed and added into 80mL of deionized water, and the mixture is stirred until the mixture is completely dissolved to obtain a precursor solution. Putting the precursor solution into a hydrothermal kettle, and heating to 220 DEGKeeping the temperature at 24h, cooling to room temperature, adding deionized water or alcohol into the obtained product, mixing by ultrasonic wave, centrifuging at 10000rad/min in the centrifuging step, centrifuging for 6 times, 5min each time, removing supernatant, transferring the product into a vacuum drying oven, weighing 0.8g polyvinylpyrrolidone (PVP) and 0.1g dried solid, adding into a crucible, mixing, calcining at 600 ℃ for 8h in a programmed temperature control furnace, and taking out the solid in the crucible when the temperature of the programmed temperature control furnace is reduced to room temperature to obtain Fe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nanoplatelets. Through statistical analysis, prepared Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 292nm, the average thickness is 29nm, and the saturation magnetization is 31 emu/g.

Example 5

0.541g (2.001mmol) of ferric trichloride hexahydrate and 0.082g (0.603mmol) of potassium dihydrogen phosphate are weighed and added into 80mL of deionized water, and stirred until the solution is completely dissolved, thus obtaining a precursor solution. Placing the precursor solution in a hydrothermal kettle, heating to 200 ℃, keeping the temperature for 24h, cooling to room temperature, adding deionized water or alcohol into the obtained product, ultrasonically mixing, centrifuging at 10000rad/min in the centrifuging step for 6 times, 5min each time, removing supernatant, transferring the product into a vacuum drying oven, weighing 0.4g of polyvinylpyrrolidone (PVP) and 0.1g of dried solid, adding the mixture into a crucible, mixing, placing the crucible in a programmed temperature control furnace, calcining at 450 ℃ for 4h, and taking out the solid in the crucible when the temperature of the programmed temperature control furnace is reduced to room temperature to obtain Fe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nanoplatelets. Through statistical analysis, prepared Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 257nm, the average thickness is 37nm, and the saturation magnetization is 33 emu/g.

Example 6

0.541g (2.001mmol) of ferric trichloride hexahydrate and 0.082g (0.603mmol) of potassium dihydrogen phosphate are weighed and added into 80mL of deionized water, and stirred until the solution is completely dissolved, thus obtaining a precursor solution. Placing the precursor solution in a hydrothermal kettle, heating to 210 ℃, keeping the temperature for 24h, cooling to room temperature, and obtaining the productAdding deionized water or alcohol, ultrasonically mixing, centrifuging at 10000rad/min for 6 times and 5min each time in the centrifuging step, removing supernatant, transferring the product into a vacuum drying oven, weighing 0.4g polyvinylpyrrolidone (PVP) and 0.2g of dried solid, adding into a crucible, mixing, calcining at 700 deg.C for 4h, and taking out the solid to obtain Fe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nanoplatelets. Through statistical analysis, prepared Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 262nm, the average thickness is 38nm, and the saturation magnetization is 39 emu/g.

Example 7

0.541g (2.001mmol) of ferric trichloride hexahydrate and 0.104g (0.666mmol) of sodium dihydrogen phosphate dihydrate are weighed and added into 80mL of deionized water, and the mixture is stirred until the mixture is completely dissolved to obtain a precursor solution. Placing the precursor solution in a hydrothermal kettle, heating to 220 ℃, keeping the temperature constant for 12h, cooling to room temperature, adding deionized water or alcohol into the obtained product, ultrasonically mixing, centrifuging at a rotation speed of 10000rad/min in the centrifuging step for 6 times, centrifuging for 5min each time, removing supernatant, transferring the product into a vacuum drying oven, weighing 0.3g of polyvinylpyrrolidone (PVP) and 0.05g of dried solid, adding the mixture into a crucible, mixing, placing the crucible in a programmed temperature control furnace, calcining at 600 ℃ for 4h, and taking out the solid in the crucible when the temperature of the programmed temperature control furnace is reduced to room temperature to obtain Fe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nanoplatelets. Through statistical analysis, prepared Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 276nm, the average thickness is 33nm, and the saturation magnetization is 35 emu/g.

Example 8

0.541g (2.001mmol) of ferric trichloride hexahydrate and 0.104g (0.666mmol) of sodium dihydrogen phosphate dihydrate are weighed and added into 80mL of deionized water, and the mixture is stirred until the mixture is completely dissolved to obtain a precursor solution. Placing the precursor solution in a hydrothermal kettle, heating to 220 deg.C, keeping the temperature for 18h, cooling to room temperature, adding deionized water or alcohol into the obtained product, and performing ultrasonic treatmentMixing, centrifuging at rotation speed of 10000rad/min for 6 times, each time for 5min, removing supernatant, transferring the product into a vacuum drying oven, weighing 0.5g polyvinylpyrrolidone (PVP) and 0.1g solid after drying, adding into a crucible, mixing, calcining at 600 deg.C in a programmed temperature control furnace for 4h, and taking out the solid to obtain Fe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nanoplatelets. Through statistical analysis, prepared Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 283nm, the average thickness is 32nm, and the saturation magnetization is 40 emu/g.

Example 9

0.541g (2.001mmol) of ferric trichloride hexahydrate and 0.104g (0.666mmol) of sodium dihydrogen phosphate dihydrate are weighed and added into 80mL of deionized water, and the mixture is stirred until the mixture is completely dissolved to obtain a precursor solution. Placing the precursor solution in a hydrothermal kettle, heating to 220 ℃, keeping the temperature for 24h, cooling to room temperature, adding deionized water or alcohol into the obtained product, ultrasonically mixing, centrifuging at 10000rad/min in the centrifuging step for 6 times, 5min each time, removing supernatant, transferring the product into a vacuum drying oven, weighing 0.7g of polyvinylpyrrolidone (PVP) and 0.1g of dried solid, adding the mixture into a crucible, mixing, placing the crucible in a programmed temperature control furnace, calcining at 600 ℃ for 4h, and taking out the solid in the crucible when the temperature of the programmed temperature control furnace is reduced to room temperature to obtain Fe₃O₄/α-Fe₂O₃Magnetic heteroplasmon nanoplatelets. Through statistical analysis, prepared Fe₃O₄/α-Fe₂O₃The average diameter of the magnetic heteroplasmon nano-sheet is 281nm, the average thickness is 32nm, and the saturation magnetization is 43 emu/g.

It is to be understood that the above examples are illustrative only for the purpose of clarity of description and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.