CN101323781A - Nano fluorescent microspheres and their applications - Google Patents

Abstract

The invention belongs to the technical field of organic polymer materials, and specifically relates to a nano fluorescent microsphere and its application. The nano fluorescent microsphere has a core-shell structure, the shell is a water-soluble polymer, and the core is a polymer with a conjugated luminescent structure. There is a certain degree of cross-linking to play a stable role. Preparations include the preparation of amphiphilic polymers, self-assembly in solvent templates, and emulsion Suzuki polymerization. The nano fluorescent microspheres can be used in the fields of electroluminescent devices, biological detection, fluorescent marking, anti-counterfeiting ink, inkjet printing and the like.

Description

Nano fluorescent microspheres and their applications

technical field

The invention belongs to the technical field of organic polymer materials, and specifically relates to a class of nano fluorescent microspheres and applications thereof.

Background technique

The rapid development of organic/polymer light-emitting devices (Organic/Polymer Light-Emitting Devices, OLED/PLED) has brought a revolutionary change to the field of display technology. The display made of it has the advantages of high image quality, adjustable screen size, low energy consumption, light and thin weight, foldable flexible polymer substrate, and low processing cost. It represents the development trend of the future display technology field.

In 1987, CWTang and others successfully developed an organic light-emitting diode (OLED), using aniline-TPD (triphenyldiamine derivative) as the hole transport layer (HTL), and aluminum and octahydroxyquinoline complex-Alq3 as the light emitting layer. layer (EML). Its working voltage is less than 10V, and its brightness is as high as 1000cd/m ² . In 1990, JH Burroughes and others at the Cavendish Laboratory of the University of Cambridge reported for the first time a polymer thin film electroluminescent device prepared with poly(p-phenylene vinylene) PPV (poly(p-phenylene vinylene), and obtained a blue light driven by a DC bias voltage less than 14V. Green light output, its quantum efficiency is 0.05%.Subsequently, D.Braum and AJHeeger of the University of California reported in 1992 the light-emitting diodes prepared with PPV and its derivatives. Light emission in two colors of orange and yellow. These breakthroughs have made this field a research hotspot in recent years.

From 1987 to the present, OLED technology has developed very rapidly, especially the stability of the device has been greatly improved, basically meeting the practical requirements. Among them, the half-life of green light materials has reached 20,000 to 50,000 hours, and the half-life of blue light materials has also exceeded 30,000 hours. In terms of luminous efficiency, OLED is much higher than the level of plasma display (PDP) and thin film transistor liquid crystal display (TFT-LCD). In terms of device colorization, a variety of schemes have been proposed, including the three-primary color method, the white light plus color filter method, and the blue light energy conversion method, and many companies have launched full-color OLED samples.

Organic electroluminescent devices are carrier double-injection light-emitting devices. The injected electrons and holes recombine in organic matter and are deactivated by radiation to generate light. Therefore, the injection balance of electrons and holes is very important to achieve high luminous efficiency of the device. Now, in order to solve the problem of electron and hole transport balance, people have introduced electron transport layer (ETL) or hole transport layer (HTL) in organic electroluminescent devices to form a multi-layer device structure, and use low power The material of the letter is used to make the cathode. Although these methods can improve the quantum efficiency to a certain extent, there are still many problems. For example, the multilayer device structure has great difficulties in preparation technology, and the low work function material is extremely sensitive to changes in atmospheric pressure and is very difficult to compress. Therefore, in order to develop efficient and stable PLEDs, it is very meaningful to produce polymers with balanced electron-hole transport properties in their intrinsic structure.

In addition, the stability of the electroluminescent material used as the light-emitting layer is also an urgent problem to be solved. Due to the easy crystallization of small molecular organic compounds, it is easy to form black spots in the film after the device is made, thereby reducing the life of the device; while oligomers and polymer materials with amorphous characteristics can avoid this to a certain extent. Therefore, it is necessary to develop a polymer material with high thermal stability. However, some existing polymer electroluminescent materials, such as polyfluorene materials, easily form excimer associations or molecular aggregates in the solid state, resulting in the quenching of their luminescence and the reduction of device efficiency. The spectral stability of the material is also of particular importance. Some studies in recent years have shown that introducing a helical benzofluorene structure into a polymer can improve the thermal stability and spectral stability of the material to a certain extent, and has a very important application prospect in the field of organic/polymer electroluminescent materials.

Contents of the invention

The object of the present invention is to propose a rice fluorescent microsphere with good thermal stability and spectral stability and its application.

The nano fluorescent microsphere proposed by the present invention has a core-shell structure, the shell is a water-soluble polymer, and the core is a polymer with a conjugated light-emitting structure, and has a certain degree of cross-linking. Its structure is shown in Figure 5 .

The size of the microspheres is 20-20000 nm, preferably 20-1000 nm. Said water-soluble polymer is one of polyethoxy ether, polypropoxy ether, polybutoxy ether, polyacrylamide, polycaprolactone and polyisopropylacrylamide.

The said core conjugated luminescent structure polymer is one of thiophene, oligothiophene, fluorene, oligofluorene, triphenylamine, carbazole, substituted benzene, benzothiophene or benzothiazole and the like. For example:

The preparation method of nano fluorescent microsphere of the present invention comprises the synthesis of block polymer, self-assembly in the solvent template and the preparation of nano fluorescent microsphere, and the former can adopt reversible addition-fragmentation chain transfer (RAFT) reaction (see Shown in Figure 1), the latter adopts Suzuki coupling reaction (shown in Figure 2).

The compounds involved in the present invention can be used in the preparation of organic polymer electroluminescent devices, and can also be widely used in other fields, such as biological detection, fluorescent marking, anti-counterfeiting ink and inkjet printing, organic integrated circuits, organic field effect Transistors, organic thin film transistors, organic solar cells, organic laser diodes, etc.

Description of drawings

Figure 1 is a schematic diagram of the synthesis of block copolymers by reversible addition-fragmentation chain transfer (RAFT) reaction.

Figure 2 is a schematic diagram of the Suzuki coupling reaction.

Fig. 3 is the ultraviolet absorption and fluorescence spectrograms of the solution and solid of the model molecule.

Wherein, the solution uses CHCl ₃ as a solvent, and the solution concentration is less than 10 ^-5 mol/L; the fluorescence spectrum is excited by 350nm light.

Fig. 4 is a transmission electron microscope (TEM) photo of nano fluorescent microspheres.

Fig. 5 is a diagram of the core-shell structure of the nano fluorescent microsphere.

Detailed ways

The present invention will be further described below by embodiment, but not limit the scope of the present invention:

1. Preparation of nano fluorescent microspheres:

Embodiment 1, synthetic block copolymer

Accurately take by weighing 33.8mg azobisisobutyronitrile (AIBN), 168.4mg cumyl dithiobenzoate (CDB) and 754.0mg p-bromostyrene, the ratio of the amount of the three substances is 1: 3:20, freeze with liquid nitrogen-vacuumize-fill with nitrogen, repeat 3 times, add 10ml of THF after dehydration under nitrogen atmosphere, fully stir and react at 80°C for 10 hours, add 765.3mg of hydroxyethyl ester to continue the reaction 10 hours. After dialysis, centrifugation, washing and drying, an amphiphilic p-bromostyrene-hydroxyethyl ester block copolymer is obtained.

Example 2, solution template self-assembly

Add 150.0mg p-bromostyrene-hydroxyethyl ester block copolymer, dissolve in 60ml water, then add 16.58g potassium carbonate, stir to dissolve.

Example 3, Emulsion Suzuki Polymerization

Accurately weigh 54.8 mg (0.10 mmol) of 2,7-dibromo-9,9-dioctylfluorene, 2,7-bis(1,3,2-dioxaborolane-diyl)-9, 9Dioctylfluorene 62.0mg (0.11mmol), dissolved in 1ml toluene, after freezing in liquid nitrogen, add 10mg of catalyst Pd(PPh ₃ ) ₄ , freeze in liquid nitrogen-vacuumize-inflate nitrogen, repeat 3 times Stir under avoiding light and nitrogen atmosphere, pass the solution obtained in Example 2 through nitrogen for 5 minutes and isolate the air, extract 20ml of the solution and add it to the reaction system, stir well until the formed emulsion is stable, and react at an oil bath temperature of 80°C After 3 days, polyfluorene nano fluorescent microspheres with a core-shell structure were obtained.

2. Preparation of organic polymer electroluminescent devices:

Example 4, preparation of nano fluorescent microsphere electroluminescence device

After cleaning the indium tin oxide (ITO) transparent conductive glass, the nano fluorescent microspheres are dissolved in THF (2.5%, mass concentration), and evenly coated on the ITO substrate by the spin coating method, and the film thickness is controlled to 150-200nm, and then, Vacuum-evaporated magnesium and aluminum as electrodes can be made into single-layer electroluminescent devices.

After the ITO transparent conductive glass is cleaned, copper phthalocyanine (CuPc) and diamine derivatives (NPB) are sequentially evaporated on it, and then a layer of THF solution of the model compound is evenly coated by the spin coating method, and evaporated after drying and curing. Plating AlQ, then depositing magnesium and silver as electrodes, can be made into a multilayer electroluminescent device with a structure of ITO/CuPc/NPB/nano fluorescent microspheres/AlQ/Mg:Ag.

Embodiment 5, preparation of organic thin film field effect transistor

Indium tin oxide ITO is used as the source and drain, and after the source and drain with a channel length of 50 μm are prepared by photolithography, the nano-fluorescent microspheres are used as the semiconductor layer, and a layer is formed on it by spin coating. layer film, and then vacuum-deposit polytetrafluoroethylene layer and silver electrode in sequence as insulating layer and grid respectively, and organic thin film field effect transistor can be prepared.

Claims (2)

1. A nano fluorescent microsphere, characterized in that the nano fluorescent microsphere has a core-shell structure, the outer shell is a water-soluble polymer, the inner core is a polymer with a conjugated luminescent structure, and the size of the ball is 20-20000 nanometers; wherein: Said water-soluble polymer is one of polyethoxy ether, polypropoxy ether, polybutoxy ether, polyacrylamide, polycaprolactone, polyisopropylacrylamide; The polymer with conjugated light-emitting structure is one of thiophene, oligothiophene, fluorene, oligofluorene, triphenylamine, carbazole, substituted benzene, benzothiophene or benzothiazole. 2. The application of the nano fluorescent microsphere as claimed in claim 1 in the fields of electroluminescent devices, biological detection, fluorescent marking, anti-counterfeiting ink or inkjet printing.

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