CN103776856B - The characterizing method of a kind of organic molecule monocrystal material and application thereof - Google Patents

Abstract

The present invention provides a method for characterizing organic small molecule single crystal materials and its application. The method includes 1) using dielectric materials and organic semiconductor materials to sequentially form a dielectric layer and an organic semiconductor nano-film on a support network, and the organic semiconductor The thickness of the nano film is 0.8-8nm; 2) annealing the product obtained in step 1) under anhydrous and oxygen-free conditions, so that the organic semiconductor nano film is converted into an organic single crystal nano material; 3) the step 2) obtained The product was observed under a transmission electron microscope, and the size, surface roughness and crystallinity of the organic single crystal nanomaterial were measured. The method of the present invention prepares nanocrystals under conditions of relatively low temperature and normal pressure, and the resulting product is generated in situ on the carrier grid without the need for crystal retransfer steps, and the crystal grains will not be polluted or damaged during the single crystal formation process, and can be directly Used for electron microscope observation and characterization. The method of the invention is also particularly beneficial for the analysis of different intermediate states during the formation of nanocrystals.

Description

A Characterization Method and Application of Organic Small Molecule Single Crystal Material

technical field

The invention relates to a characterization method and application of an organic small molecule single crystal material, in particular to an electron microscope characterization method of a nanoscale organic small molecule single crystal material and the application of the method in studying the structure of an organic single crystal nano material.

Background technique

The analysis of the aggregation state or crystal structure of organic small molecule materials can provide the necessary material basis for further research on the electron transport properties of organic solids and the preparation of organic optoelectronic devices. This is because the crystal structure of an organic molecule directly reflects the way the molecules are packed, and the arrangement of the molecules will directly affect the electronic density of states (such as the nonlocal nature of electrons in π bonds). In the existing literature and patents, there are many methods for growing organic crystals, which are divided into chemical methods and physical methods. Organic crystals have poor stability and low mechanical strength, so single crystal samples are easily damaged during the crystal transfer process, making structural analysis extremely difficult. At present, crystals prepared by physical methods are used for microstructure analysis, especially for nanocrystals. Because the crystals are firmly bonded to the substrate and the crystal size is too small, the sample transfer process is very difficult, and the sample cannot be completely transferred. Adhere to the copper grid, and then put it into the sample chamber of the transmission electron microscope for structural observation or electron diffraction characterization; the nanocrystals prepared by chemical methods can have a complete structure and better adhere to the copper grid, but the crystals are accompanied by impurities in the solution. Characterization and Analysis.

Contents of the invention

The purpose of the present invention is to propose a simple and feasible characterization method for transmission electron microscope analysis of organic nanocrystal structure.

The invention provides a characterization method and application of an organic small molecule single crystal material, characterized in that the method comprises:

1) Using dielectric materials and organic semiconductor materials to sequentially form a dielectric layer and an organic semiconductor nano-film on the carrier grid, the thickness of the organic semiconductor nano-film is 0.8-8nm;

2) annealing the product obtained in step 1) under anhydrous and oxygen-free conditions to convert the organic semiconductor nanofilm into an organic single crystal nanomaterial;

3) Observe the product obtained in step 2) under a transmission electron microscope, and measure the size, surface roughness and crystallinity of the organic single crystal nanomaterial.

The present invention has the following advantages relative to the prior art:

The invention proposes an organic small molecule nano single crystal suitable for transmission electron microscope characterization, especially a pentacene nano crystal material. Nanocrystals are prepared under lower temperature and normal pressure conditions, and the resulting products are generated in situ on the grid, without the need for crystal retransfer steps, and the crystal grains will not be polluted or damaged during the single crystal formation process, and can be directly used for transmission electrons Microscopic observation and characterization. According to needs, it can also help researchers to conduct a detailed analysis of different intermediate states during the formation of nanocrystals (which can be achieved by controlling the annealing temperature and/or time). After annealing for a certain period of time under an inert gas protection environment, the required characterization samples can be obtained. During the characterization process, the crystals can be kept intact, and a complete nanocrystalline grain structure can be obtained, which can accurately reflect the structural information of the sample to be analyzed, and has certain universality. The characterization method of the invention solves the disadvantage that the complete morphology and structure of the organic nanocrystals prepared by physical methods cannot be obtained, and also avoids the influence of foreign impurities due to the preparation conditions of the organic nanocrystals prepared by chemical methods.

Other features and advantages of the present invention will be described in detail in the following detailed description.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is the structural representation of tube furnace for material preparation;

Figure 2 is an atomic force microscope photo of pentacene thin film;

Fig. 3 is the scanning electron micrograph of the pentacene single crystal nano single crystal material on the copper net of modification;

Fig. 4 is the electron transmission electron micrograph of pentacene nano-single crystal material;

Fig. 5 is the electronic diffraction pattern photo of pentacene nano-single crystal material;

Fig. 6 is the transmission electron micrograph of the intermediate state in the formation process of pentacene nano-single crystal material;

Fig. 7 is an electron diffraction pattern photo of the intermediate state during the formation process of the pentacene nano-single crystal material.

detailed description

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

The invention provides a method for characterizing organic small molecule single crystal materials, characterized in that the method comprises:

1) Using dielectric materials and organic semiconductor materials to sequentially form a dielectric layer and an organic semiconductor nano-film on the carrier grid, the thickness of the organic semiconductor nano-film is 0.8-8nm;

2) annealing the product obtained in step 1) under anhydrous and oxygen-free conditions to convert the organic semiconductor nanofilm into an organic single crystal nanomaterial;

3) Observe the product obtained in step 2) under a transmission electron microscope, and measure the size, surface roughness and crystallinity of the organic single crystal nanomaterial.

According to the present invention, the dielectric material can be a variety of high-molecular polymers or inorganic materials conventional in the art that can withstand high temperatures (at least 140°C without deformation). The material is one of SiO ₂ , polycarbonate, polystyrene, polyimide and polymethyl methacrylate.

According to the present invention, the organic semiconductor material may be an organic small molecule material commonly used in the field with a biphenyl structure, preferably pentacene. The inventors of the present invention have found that the method of the present invention can characterize various characteristics of pentacene nano-single crystal materials particularly well.

According to the present invention, the carrier net can be various conventionally used carrier nets in this field, which can be obtained commercially, but preferably, the carrier net is copper mesh, nickel mesh, molybdenum mesh, gold mesh and nylon mesh One of.

According to the present invention, forming the dielectric layer on the carrier is mainly to form a smooth surface with low roughness. Therefore, the method for forming the dielectric layer can be various conventional methods. Preferably, the method of forming the dielectric layer The method is a spin coating method, a magnetron sputtering method and a self-assembly method.

The thickness of the dielectric layer can be selected within a wide range, as long as the electron beam of the transmission electron microscope used can penetrate the sample to form a clear image.

According to the present invention, the method for forming the organic semiconductor nano-film is preferably a vacuum evaporation coating method. The conditions of the vacuum evaporation coating can be selected under a wide range of conditions, but preferably, the conditions of the vacuum evaporation coating include a deposition rate of 0.001-0.05nm/s, and a vacuum degree of 1× ^10-5-1 ×10 ^-7 mbar, the temperature of the grid with the dielectric layer formed during deposition is 20-30°C, and the deposition time is 30-300s.

According to the present invention, during the annealing process, the molecules in the nano-film migrate, that is, the molecules that originally formed the nano-film are reunited, so that the nano-film changes from the original two-dimensional film structure to the three-dimensional crystal Structural transformation, forming small-sized grains (the whole process does not break away from the surface of the dielectric layer). Therefore, the annealing can be carried out under a wide range of conditions, as long as the nanofilm can be converted into an organic single crystal nanomaterial, preferably, the annealing is carried out under anhydrous and oxygen-free conditions and a temperature of 60-140 ℃ for 20-360min, preferably under anhydrous and anaerobic conditions and a temperature of 80-120℃ for 20-360min, more preferably anhydrous and anaerobic conditions and a temperature of 100-120℃ for 60-120min. The present invention can control the temperature and/or time of annealing to obtain nanomaterials in different intermediate states and then observe them with a transmission electron microscope, which is very beneficial to the study of different intermediate states in the process of nanocrystal formation, not only does not require retransfer steps, It is also possible to preserve the complete crystal structure. Wherein, the anhydrous and oxygen-free means that the water content in the reactor is less than 0.5ppm, and the oxygen content is less than 0.05ppm. The method of realizing anhydrous and oxygen-free is well known to those skilled in the art, so it will not be repeated here.

The purpose of the present invention can be achieved as long as the annealing is carried out under anhydrous and oxygen-free conditions. Considering that pure annealing conditions can further improve the quality of nanoscale organic small molecule single crystal materials, preferably, the annealing step is performed in an inert atmosphere , wherein, the inert gas may be the same as the above-mentioned inert gas fed into the reactor (such as Ar and/or N ₂ ).

According to the present invention, for the method of observing under the transmission electron microscope in step 3), since the method of transmission electron microscopy is well known to those skilled in the art, the operating method of using transmission electron microscopy for characterization can refer to the instruction manual of the electron microscope, here No longer.

The invention also provides the application of the above method in studying the structure of the organic single crystal nanometer material. The method of the invention can obtain more accurate characterization results for the characterization of the organic small molecule nano-single-crystal material, and provides a better solution for the structure analysis of the organic nano-single-crystal material.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way if there is no contradiction. The combination method will not be described separately.

In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. In the following examples, pentacene is a commercially available raw material (powder, 97%, purchased from Aldrich Chemical Company); the copper grid is a commercially available electron microscope special copper grid (with support film); the concentration of polystyrene during spin coating is 0.5% by weight; the morphology of the film was characterized by an atomic force microscope (Nanoscope IIIa MultiMode, Veeco Company); the nanocrystal structure was characterized by a transmission electron microscope (Tecnai G2F20U-TWIN, FEI Company).

Figure 1 is a schematic diagram of the tube furnace used in the test; the tube furnace used in the test is the SK ₂ -4-10A type produced by Tianjin Electric Furnace Factory, equipped with a quartz tube that can be evacuated and filled with gas, and its structure schematic diagram is as follows Figure 1: The quartz tube is located inside the resistance furnace, the temperature of the resistance furnace is controlled by the temperature controller KSY-5-12A, the evaporation source is placed in the center of the resistance furnace, and the annealed product is placed at a suitable temperature; the protective gas flows along the evaporation source to The direction of the product after annealing goes into the quartz tube.

Example 1

(1) Put the copper grid into an organic solvent such as alcohol and let it stand, then take it out and dry it in a vacuum chamber. After drying, decorate a layer of polystyrene on the copper grid with a thickness of 20nm by spin coating, and then put it into an oven for vacuum drying at a drying temperature of 80°C; put the modified copper grid into an evaporation apparatus for vacuum evaporation For coating, the temperature at the copper grid is controlled at 20°C, the thermal evaporation temperature of pentacene powder is 122°C, the deposition rate is 0.001nm/s, the vacuum degree is 1×10 ^-7 mbar, and the deposition thickness of pentacene is 0.8nm film;

(2) After putting the modified copper mesh deposited with 0.8nm pentacene thin film into the quartz tube, seal the quartz tube, evacuate it with a mechanical pump to below 10Pa, and then fill it with protective gas (inert gas argon) to Normal pressure, then evacuated to below 10Pa, and then filled with protective gas to normal pressure, and so on repeatedly, to ensure that there is no oxygen and water vapor in the quartz tube as much as possible; after filling the protective gas for the last time, wait until the pressure in the quartz tube is normal , keep the protective gas (inert gas argon) flowing at a rate of 50 sccm. The temperature of the tube furnace was raised to 120° C. and then kept warm. After 20 minutes of heat preservation, the pentacene single crystal nanomaterial formed on the grid can be obtained;

(3) The obtained pentacene thin film and pentacene single crystal nanomaterial were observed under a transmission electron microscope, and Figures 2 to 5 were obtained.

Figure 2 is an AFM topography image of a 0.8nm pentacene film deposited on the surface of a copper grid modified with a polymer dielectric layer. The prepared film is composed of disc-shaped particles. The film with this morphology is conducive to the subsequent nanocrystals Formation.

Figure 3 is the SEM image of the annealed 0.8nm pentacene thin film, which shows that the shape of the obtained nanocrystals is complete, and there are many samples that can be used for structural analysis.

Figure 4 and Figure 5 are the TEM morphology and SAED diffraction patterns of the obtained pentacene single crystal micron material, respectively. TEM topography showing the shape of the grains of the sample used for analysis and reported in literature (NorthrupJ.E.;Tiago M.T.;Louie S.G., Phys.Rev.B 2002,66,121404(R)(1-4).) The crystal grains are similar without damage; the SAED diffraction pattern clearly shows the single crystal characteristics of the crystal structure, without the influence of impurities.

The results show that the commercially available copper mesh is modified by polymer firstly, and then the pentacene film is deposited, and then annealed to obtain nanomaterials, and the obtained nanomaterials are characterized as pentacene by transmission electron microscope SAED. Nano single crystal, the shape of the single crystal is the same as the equilibrium shape of the pentacene crystal reported in the literature, and the size, surface roughness and crystallinity can be easily characterized.

Example 2

(1) Put the copper grid into an organic solvent such as alcohol and let it stand, then take it out and dry it in a vacuum chamber. After drying, decorate a layer of polystyrene on the copper grid with a thickness of 100nm by spin coating, and then put it into an oven for vacuum drying at a drying temperature of 80°C; put the modified copper grid into an evaporation apparatus for vacuum evaporation For coating, the temperature at the copper grid is controlled at 30°C, the thermal evaporation temperature of pentacene powder is 122°C, the deposition rate is 0.05nm/s, the vacuum degree is 1×10 ^-5 mbar, and the thickness of the deposited pentacene film is 8nm ;

(2) After putting the modified copper mesh deposited with 8nm pentacene film into the quartz tube, seal the quartz tube, evacuate it to below 10Pa with a mechanical pump, and then fill it with protective gas (inert gas argon) to normal pressure, then evacuated to below 10Pa, and then filled with protective gas to normal pressure, and so on, so as to ensure that there is no oxygen and water vapor in the quartz tube as much as possible; Keep the protective gas (inert gas argon) flowing at a rate of 50 sccm. The temperature of the tube furnace was raised to 80° C. and then kept warm. After 360 minutes of heat preservation, the pentacene single crystal nanomaterial formed on the grid can be obtained;

(3) The obtained pentacene film and pentacene single crystal nanomaterials were observed under a transmission electron microscope, and crystals with complete morphology and structure could be observed.

Example 3

(1) Put the copper grid into an organic solvent such as alcohol and let it stand, then take it out and dry it in a vacuum chamber. After drying, decorate a layer of polystyrene on the copper grid with a thickness of 50nm by spin coating, and then put it into an oven for vacuum drying at a drying temperature of 80°C; put the modified copper grid into an evaporation apparatus for vacuum evaporation For coating, the temperature at the copper grid is controlled at 25°C, the thermal evaporation temperature of pentacene powder is 122°C, the deposition rate is 0.01nm/s, the vacuum degree is 1×10 ^-7 mbar, and the deposition thickness of pentacene is 1.2nm film;

(2) After putting the modified copper mesh deposited with 0.8nm pentacene thin film into the quartz tube, seal the quartz tube, evacuate it with a mechanical pump to below 10Pa, and then fill it with protective gas (inert gas argon) to Normal pressure, then evacuated to below 10Pa, and then filled with protective gas to normal pressure, and so on repeatedly, to ensure that there is no oxygen and water vapor in the quartz tube as much as possible; after filling the protective gas for the last time, wait until the pressure in the quartz tube is normal , keep the protective gas (inert gas argon) flowing at a rate of 50 sccm. The temperature of the tube furnace was raised to 100° C. and then kept warm. After 60 minutes of heat preservation, the pentacene single crystal nanomaterial formed on the grid can be obtained;

(3) The obtained pentacene film and pentacene single crystal nanomaterials were observed under a transmission electron microscope, and crystals with complete morphology and structure could be observed.

Example 4

Prepare a 0.8nm pentacene thin film according to the method of Example 3, the difference is that the temperature of the tube furnace is raised to 60°C and then kept warm to obtain an intermediate state sample in the process from thin film to single crystal, which can be characterized and analyzed by transmission electron microscope Structural changes. The results are shown in Figure 6 and Figure 7, showing a polycrystalline diffraction pattern.

It can be seen that the method of the present invention is also particularly useful for characterizing intermediate state samples.

The characterization method of the invention can conveniently carry out the transmission electron microscope characterization of the crystal material, the crystals are completely preserved during the characterization process, and the characterization result is true and reliable.

Claims (6)

1. A method for characterizing organic small molecule single crystal materials, characterized in that the method comprises: 1) Utilize dielectric material and organic semiconductor material to form dielectric layer and organic semiconductor nano film successively on carrier net, the thickness of described organic semiconductor nano film is 0.8-8nm, the method for forming described organic semiconductor nano film is vacuum evaporation coating method, the conditions of the vacuum evaporation coating include a deposition rate of 0.001-0.05nm/s, a vacuum degree of 1×10 ^-5 -1×10 ^-7 mbar, and the temperature of the grid with a dielectric layer formed during deposition 20-30℃, deposition time is 30-300s; 2) annealing the product obtained in step 1) under anhydrous and oxygen-free conditions to convert the organic semiconductor nanofilm into an organic single crystal nanomaterial, wherein the annealing conditions include a temperature of 60-140° C. and a time 20-360min; 3) Observing the product obtained in step 2) under a transmission electron microscope, and measuring the size, surface roughness and crystallinity of the organic single crystal nanomaterial. 2. The method of claim 1, wherein the dielectric material is one of _SiO2 , polycarbonate, polystyrene, polyimide, and polymethylmethacrylate. 3. The method of claim 1, wherein the organic semiconductor material is pentacene. 4. The method according to claim 1, wherein the carrier net is one of copper net, nickel net, molybdenum net, gold net and nylon net. 5. The method according to claim 1, wherein the method of forming the dielectric layer is a spin-coating method, a magnetron sputtering method or a self-assembly method. 6. The application of the method described in any one of claims 1-5 in the study of the structure of organic single crystal nanomaterials.