FABRICATION OF THE SURFACE CONTROLLED QUANTUM DOTS ALLOWING THE SIZE ADJUSTMENT AND THEREOF

Abstract

The synthesis of quantum dots, whose surface and quantum dot size can be controlled as desired, can be stored in different solvents or solid without prolonged degradation, agglomeration and can be transferred to water from organic solvents by means of phase transfer reaction which means can be made water-soluble. The optical properties are related to the production of quantum dots, the size of the quantum dots is controlled with surface. Obtained quantum dots are ready to produce in large amounts and can take places of sensors, nanomaterial applications, florescent applications.

Claims

1-7. (canceled)

8. A method for fabricating quantum dots comprising: ensuring that the quantum dots are quantum sizes by using different reagents; slowing growth of the quantum dots in a controlled manner wherein the quantum dots can be stored for long periods, synthesising the quantum dots through radiation in the visible region, so that the quantum dots are size-adjustable and surface-controlled, wherein; the dots are obtained through mixing the different reagents in different ratios as solids and through reflux of products at different temperatures, and different reagents are be made through dissolving solids separately in solvents, and further comprising heat treating the quantum dots by mixing the different reagents with each other, wherein large amounts of size controlled dots in a precise range or close to the specified range, which can be stored for long periods of time, are transferred from organic solvents to water and become water-soluble through phase transfer reaction, and can radiate in the visible region.

9. The method of claim 8, further comprising; dissolving the separate solid structures used for mixing in the solvents, and using different proportions of the solvent with different amounts of the solids, wherein the mixture of the compounds prepared separately in solvents with each other are exposed to reflux in atmospheric environments, and are heat treated at between 50° C. and 90° C. and for 30 minutes to 5 days.

10. The method of claim 8, wherein the solvents are one of long chain fatty acids, saturated or unsaturated carboxylic acid structures with carbon number 6-20, solvents with small carbon numbers such as methanol, ethanol, propanol, isopropanol or trace amounts of different solvents or mixtures with water.

11. The method of claim 8, further comprising obtaining single quantum dots using at least one of alkalinity forming metals Na, Li, K or Rb; hydroxides; or long chain carboxylate derivatives of general transition elements, wherein reflux is realized for certain periods in an initiator metal complex basic solution, wherein the initiator metal complex is a long chain metal initiator, and the size of the quantum dots is developed based on the different agents having different properties that are added into the solvent.

12. The method of claim 9, wherein the solution used for a synthesis process contains solvents in the range of 50-75%, an initiator metal ester in the range of 10-25%, and a pH adjuster in the range of 0.1-5%.

13. The method of claim 8, further comprising transforming the quantum dots from hydrophobic to hydrophilic by attaching a starting ligand to the surface during synthesis.

14. The method of claim 8, further comprising using UV-Vis spectroscopy to calculate the surface properties of the quantum dots, whose growth characteristics can be followed to realize growth characteristics.

Description

FIGURES TO HELP DESCRIBE THE INVENTION

[0012] FIG. 1: NMR Long carboxylate chains onto the synthesized quantum dots

[0013] FIG. 2: FTIR Peaks of the long carboxylate chains on quantum dots

[0014] FIG. 3: TEM image of agglomeration free quantum dots

[0015] FIG. 4: XRD Crystalline features of the synthesized quantum dots

DETAILED DESCRIPTION OF THE INVENTION

[0016] In this detailed description, the present invention is described in such a way that the size-controlled and surface-controlled quantum particles can be produced without any negative effect on production.

[0017] In this invention quantum particle sizes (between 1-8 nm) can be controlled as desired, also can be stored without change in size and emission in different solvents or solid without long-term degradation without agglomeration, and can be transferred to water from organic solvents and made water-soluble at any time.

[0018] With the present invention, it is ensured that the particle size is controlled within a precise range with controlled features. The particles are round and generally fabricated by thermodynamic control. Since surface modification is automatically provided at the end of this method, its optical properties are also under control. Quantum dots can be produced in alcoholic solutions or partially aqueous solutions if desired. The added amount of water helps to increase the size of the quantum dots to be obtained.

[0019] The quantum particles obtained are free from agglomeration as evidenced by TEM (Transmission Electron Microscopy) analysis. This is because the used starting ligand used is properly attached to the surface during the synthesis and provides a steric effect when growth ends. By this steric effect, quantum dots do not show agglomeration when compared to other quantum dots of the same size. Thus, phase transfer is possible after the dots are obtained. Quantum dots, which are hydrophobic in nature can be converted into hydrophilic and it can be stored in long terms. It is demonstrated that the obtained quantum dots do not show agglomeration at the rate monitored for 1 year. After storage, only the desired composition is revealed by atomic analysis. In this way, the crystal structure; inclusion of other atoms is prevented.

[0020] Synthesis conditions can be performed in the desired environment. Generally, processes are performed with atmospheric environments and relatively low temperatures (room temperature or 90° C.). In addition, it has been proved by XRD studies that the crystal structure is more clear as the temperature increases. The solvent in the medium is usually alcohol based, which contains small numbers of carbon. In this way, extremely reactive and extreme basic environments can be prepared. If desired, reagents can be added together or separately. As the temperature increases, all components dissolve better, so the initial stages of nucleation can be under control.

[0021] If we evaluate the ratios of the reagents used, the different reagent ratios create different starting solution characters and contribute to the particle growth. Highly basic environments can be directed as desired in the first 15-60 minutes, which is called as chaotic period. For this reason, basic initiators in different proportions are added to the metal complex, which is generally used as the beginning. Alcohols or alcohol mixtures can be used as reaction environments. The addition of small amounts of water increases the growth rate. It is observed that monodispersity is generally provided in all cases.

[0022] In order to obtain single atom and oxygen containing quantum dots, the starting metal complex is usually refluxed for a certain of period of time in the basic medium. Basic forming metals can generally be used as Na, Li, K and even Rb hydroxides. Long chain carboxylate derivatives of common transition elements can be used as metal initiators. Preferably long chain ones are preferred. When different agents with different properties (Lewis acid or some) are added into the solvent, the quantum sizes can be developed and controlled based on proportions.

[0023] The reaction steps can be monitored by a suitable method. PL or UV-Vis spectroscopy is vastly utilized because they are quite easy methods for detection. As the reaction time increases and quantum dots grow, small quantities of samples provide important information about quantum dot development and particle size. Emission wavelengths or absorption wavelenghts can usually be detected for the reaction steps by increasing emission of wavelengths in PL spectroscopy. After the synthesis of quantum dots is finished, cold separation can be performed and the sample can be dried by removing solvent molecules at relatively low temperatures.

[0024] In this invention, generally, long chain fatty acids, for example, hexadecanoic acid, oleic acid, as well as saturated or unsaturated carboxylic acid structures with carbon numbers of 6-20 are used. In addition to this content, small amounts of methanol, ethanol, propanol, isopropanol and solvents such as different solvents or mixtures are used with water. In these environments, Mg (OH) 2, Ba (OH) 2 are used as examples of alkali metal bases and other strong base structures. Metal salt structures, especially Ti, Cr, Mn, Zn, especially transition metals, can be used here for doping of different atoms. Different time and shape results can be observed due to valence electron structures and d orbital contents.

[0025] The ratios of reagent amounts and the amounts of metal salts used specifically for the synthesis process and also to control the particle size in a variable manner. For example, ratios by weight for the synthesis process; [0026] Solutions: in the 50-75% range, [0027] Initiator metal carboxylate: 10-25%, [0028] The pH adjuster is in the range of 0.1-5%.

[0029] In this process, the compositions vary depending on the properties of the product to be obtained.

[0030] In the present invention, solid materials are used for the mixture. The input materials are in powder form and are mixed with solvents in a subsequent processes. Solid structures are dissolved separately in solvents to obtain products. If desired, they can be mixed at the same time. This dissolving process can enable different amounts of solvent to be used separately with different amounts of solids. Particularly, the compounds prepared in the solvent are mixed with each other and reflux should be performed at 50° C. or other different temperatures varying till 90° C. and reflux can be continued for different timelines like 30 minutes to 5 days.

[0031] As can be seen in FIG. 1, quantum particles can be obtained agglomeration free with initial ratios and can be stored without agglomeration for a longtime due to the surface protection.

[0032] Due to the nature of the invention, the side effects of agglomeration and sticking together quantum dots with deviated fluorescence features are eliminated. Especially considering the size of the quantum dots, it allows to synthesize quantum dots that can be stored for a long time and radiate in the visible region with deep control.

[0033] It is clear that a skilled person in the chemistry/material technology can demonstrate the novelty of the invention using similar embodiments and/or apply it to other areas of similar purpose. It is therefore clear that such embodiments will be produced based on the similar innovation technique.