TWI555234B - Light emitting device comprising anisotropic metal nanoparticles-dielectric core-shell nanostructures - Google Patents

Description

Light-emitting device comprising anisotropic metal nanoparticle-dielectric core-shell nanostructure [Cross-Reference to Related Applications]

The present application claims priority to Korean Patent Application No. 10-2014-0087616, filed on Jan. 11, 2014, to the Korean Intellectual Property Office, and the entire contents of 35 U.SC119, the entire contents of which are This is hereby incorporated by reference.

The present invention relates to a light-emitting device comprising an anisotropic metal nanoparticle-dielectric core-shell nanostructure; in particular, a light-emitting device having improved emission efficiency, which can be introduced into a metal nanoparticle by induction The luminescent material emission of the illuminating device of the surface plasma resonance phenomenon is enhanced.

Light-emitting diodes (LEDs) that attract attention as new next-generation light sources have many advantages over current light sources such as incandescent, halogen or fluorescent lamps, including high luminous efficiency and response. Fast, long life, miniaturized, and unlike fluorescent lamps, it is preferably used as a friendly source of mercury-free environment. As a result, LEDs can be used in a variety of applications, from signal, display, communications, portable terminals or the automotive industry to the general lighting industry.

In particular, white LEDs are used in backlight units and vapors for LCD TVs or notebooks. Headlights or similar, and based on the reduction of general lighting and incandescent lamp management policies, the lighting market is expected to continue to grow rapidly.

In general, white LEDs can be implemented by a combination of multiple LED wafers that emit light having different monochromatic wavelengths, or a combination of an LED wafer and a single or multiple component luminescent material. The former (the white LED is realized by a combination of a plurality of LED chips) is incapable of achieving color reproducibility and high-purity white light because the operating voltages applied to the respective wafers do not coincide and the output of each wafer changes with the ambient temperature. Therefore, white LEDs are generally fabricated by coating a luminescent material and a polymer encapsulating film on an LED wafer having a near-ultraviolet or blue-light monochromatic wavelength. In order to achieve high color purity white LEDs, LED chips are used in combination with a single luminescent material or a plurality of luminescent materials having red, green, and yellow emission wavelengths.

That is to say, the luminescent material in the white LED acts as a blue light (or near-ultraviolet light) generated by absorbing the LED wafer, and converts the light into red, green, blue or yellow light having a long wavelength, which is the essence of the luminescent material. . Thus white light is achieved by the emitted light of the LED wafer that is not absorbed by the luminescent material.

The overall light efficiency of white LEDs is one of the important factors representing the performance of LEDs. Therefore, in order to achieve a white LED having high brightness and low power consumption, it is necessary to increase the light conversion efficiency of the luminescent material. Further, in order to achieve a white LED of high color purity, two or more luminescent materials are required.

That is, it is helpful to provide a luminescent material that has an absorption wavelength of a suitable spectrum that overlaps the emission wavelength of the LED wafer. Furthermore, in order to achieve white light, the emission wavelength should be in the range of visible light having a relatively long wavelength. In addition, a luminescent material having a high internal quantum efficiency is preferably used.

However, the absorption and emission properties of the luminescent material are properties determined at the stage of synthesizing or preparing the luminescent material, and it is quite difficult to prepare a luminescent material having a controllable absorption and emission wavelength and high quantum efficiency.

The present invention provides a light-emitting device having improved emission efficiency by inducing excitation and emission enhancement of a luminescent material, which can be introduced into a light-emitting device using surface plasma resonance phenomena of metal nanoparticles.

The above and other objects of the present invention will be described or illustrated in the following description of the preferred embodiments.

According to one aspect of the present invention, a light-emitting device comprising an anisotropic metal nanoparticle-dielectric core-shell nanostructure and a light-emitting material is provided. An anisotropic metal nanoparticle-dielectric core nanostructure comprising an anisotropic metal nanoparticle having an aspect ratio capable of forming two or more surface plasma resonance bands, and coated on a metal A dielectric shell on the surface of the nanoparticle.

As described above, according to the present invention, in a light-converting light-emitting device implemented by a combination of a light-emitting device having an emission wavelength in a near ultraviolet light or a visible light region and a light-emitting material, two or more surface plasma resonance bands are in the same Time can induce excitation enhancement and emission enhancement of the luminescent material by introducing an anisotropic metal nanoparticle-dielectric core-shell nanostructure into the luminescent layer. In addition, since the metal-dielectric core-shell nanostructure can keep the luminescent material at a certain interval from the thickness of the dielectric shell and the metal nanoparticle, it is expected that local electric field enhancement occurs on the surface of the metal nanoparticle, thereby causing the luminescence The enhancement of the phosphorescence intensity of the material is maximized. In addition, the dielectric shell of the anisotropic metal nanoparticle-dielectric core-shell nanostructure maintains the shape and appearance ratio of the anisotropic metal nanoparticles in the light-emitting device, and the high-temperature heat is locally in the light-emitting device. The energy generated from the excitation luminescent material to the surface of the metal nanoparticles is generated, thereby preventing quenching of the luminescent material. Therefore, a light-emitting device having improved emission efficiency and durability can be achieved.

Further, according to the present invention, in order to achieve a high color purity white light LED, a plurality of luminescent materials having different absorption and emission wavelengths can be used. In such cases, two or more surface plasma strips of the anisotropic metal nanoparticles are controlled to optimize spectral overlap with the luminescent material absorption and emission wavelengths. Thereby, emission enhancement of the luminescent material is simultaneously performed and a light-converting illuminating device having improved color purity and brightness is provided.

Therefore, according to the present invention, an anisotropic metal nanoparticle-dielectric core-shell nanostructure is used, and an illumination device having improved light conversion efficiency can be used in various fields, including self-signal, display, communication, portable terminal or Automobiles and other industries to the general lighting industry.

The above and other features of the present invention will become more apparent from the detailed description of the preferred embodiments of the invention, wherein: FIG. 1a schematically shows an anisotropic metal nanoparticle-dielectric core. a composite of a shell nanostructure and a luminescent material combined with each other, and FIG. 1b schematically illustrates the principle of introducing a composite to a light-emitting layer by a light-emitting device having improved emission efficiency; FIG. 2a is a diagram showing YAG phosphor powder. Excitation, absorption, and emission spectra, and Figure 2b shows the excitation, absorption, and emission spectra of indium phosphide (InP)/zinc sulfide (ZnS) quantum dots; Figure 3a shows the gold nano column Transmissive electron microscopy (TEM) image, each gold nano column has a transverse plasma belt and a longitudinal plasma belt of 512 nm and 855 nm; Figure 3b shows the transmission of a gold-silver core shell nano column Electron microscopic image, each gold-silver core nano column has a transverse plasma belt and a longitudinal plasma belt of 450 nm and 600 nm, and Fig. 3c shows a penetrating electronic display of a gold-silver core shell nano column. Micro-image, each gold-silver core-shell nano column has a transverse plasma belt of 450 nm and 565 nm and a longitudinal plasma belt; Figure 4a shows gold The ultraviolet-visible spectrum of the nanocolumn, each of the gold nano columns has a transverse plasma belt and a longitudinal plasma belt of 512 nm and 855 nm; and Fig. 4b shows the ultraviolet-visible spectrum of the gold-silver core nano column. Each gold-silver core nano column has a transverse plasma band and a longitudinal plasma band of 450 nm and 600 nm, and FIG. 4c shows the ultraviolet-visible spectrum of the gold-silver core nano column, each gold - Silver core shell nano columns have transverse plasma strips and longitudinal plasma strips of 450 nm and 565 nm; Figure 5a schematically shows the absorption, excitation and emission wavelengths and anisotropy of YAG phosphors in blue LED wafers The spectral overlap between the surface plasma bands of the metallic nanoparticles, and Figure 5b schematically illustrates the absorption, excitation and excitation of the indium phosphide/zinc sulfide quantum dots in the blue LED wafer. The spectral overlap between the emission wavelength and the surface plasma zone of the anisotropic metal nanoparticles; Figure 6 shows the transmission electrons of the anisotropic metal nanoparticles-dielectric core nanostructures Microimage; FIG. 7 is a graph showing an emission spectrum of a solution containing an anisotropic metal nanoparticle-dielectric core-shell nanostructure and a luminescent material introduced therein together; FIG. 8a is a diagram showing a metal nanosphere - a transmission electron micrograph of the dielectric core-shell nanostructure, and FIG. 8b shows the ultraviolet-visible spectrum of the metal nanosphere-dielectric core nanostructure; FIG. 9 is a diagram showing a graph of the emission spectrum of a metal nanosphere-dielectric core-shell nanostructure and a solution of a luminescent material introduced therein; FIG. 10 is a diagram showing the introduction of an anisotropic metal nanoparticle containing a dielectric-free shell a pattern of an emission spectrum of a solution of the luminescent material therein; and FIG. 11 is a schematic diagram showing an illuminating device having improved emission efficiency by using an anisotropic metal nanoparticle-dielectric nucleocapsid nanostructure and two One or more different luminescent materials are introduced together to the luminescent layer.

Hereinafter, a light-converting light-emitting device according to the present invention will be described which is implemented by a combination of a light-emitting device having an emission wavelength of near-ultraviolet light or visible light and a light-emitting material having absorption and emission wavelengths in the visible light region. The light-converting light-emitting device is characterized in that an anisotropic metal nanoparticle-dielectric core-shell nanostructure is introduced into the light-emitting layer.

In general, LED wafers and luminescent materials should have high emissivity in order to achieve white LEDs with low power consumption and high brightness through a combination of LED chips and yellow light-emitting materials having near-ultraviolet or blue-light wavelengths.

To overcome the disadvantages, the emissivity of the LED wafer and the luminescent material can be improved using localized surface plasma resonance of the metal nanoparticles.

Here, local surface plasma resonance refers to the interaction between metal nanoparticles and light. If light (h ν ) is applied to the metal nanoparticle or nanostructure, collective oscillation occurs along the electric field of the light injected by the free electrons on the surface of the metal nanoparticle, thereby forming a surface plasmonic and in the metal nano A very strong local electric field is formed around the particles. Here, if the luminescent material is present around the metal nanoparticles, since the electric field is locally formed around the metal nanoparticles, the excitation enhancement (E _ex ) is increased by increasing the light absorption, so that the phosphorescence (PL) intensity of the luminescent material can be increased. . Furthermore, the emission enhancement (E _em ) of the luminescent material, that is, the increase in the quantum efficiency inherent to the luminescent material, can be expected by the interaction between the excited luminescent material and the surface plasmonics. As described in the following equation (1), in the case where the luminescent material is located around the metal nanoparticles, the radiant attenuation (γ _rad ) path of the luminescent material is less than the non-radiative attenuation (γ _{non). -rad} ) Large path, thereby increasing quantum efficiency (γ _rad + γ _M-rad >> γ _non-rad ) (Chemical Reviews, 2011 , 111 , 3888; Nature Materials, 2010 , 9 , 193; Analyst, 2008 , 133 , 1308).

That is, the total enhancement (E _total ) of the luminescent material based on the surface plasmonics of the metal nanoparticle particles can be expressed as the product of excitation enhancement (E _ex ) and emission enhancement (E _em ), as described in equation (2). .

E _total =E _ex ×E _em ...(2)

Therefore, based on the surface plasmonics of metal nanoparticles, in order to maximize the enhancement of the phosphorescence intensity of the luminescent material, it is important to perform excitation enhancement (E _ex ) and emission enhancement (E _em ) at the same time by The absorption and emission wavelength of the luminescent material is effectively controlled by overlapping with the surface plasmonics of the metal nanoparticles (Nano Letters, 2007 , 7 , 690; Applied Physics Letters, 2008 , 93 , 53106).

For example, when the absorption wavelength of the luminescent material overlaps with the plasma ribbon, the light absorption increases, so that the excitation enhancement (E _ex ) of the luminescent material is expected. When the emission wavelength of the luminescent material overlaps with the plasma strip, the rate of radiation decay increases due to the coupling of the excitation luminescent material to the surface plasmon to increase quantum efficiency, such that emission enhancement (E _em ) is expected. Therefore, if the absorption and emission spectra of the surface of the metal nanoparticle particles and the luminescent material are appropriately overlapped, the excitation enhancement and emission enhancement of the luminescent material can be simultaneously performed, thereby maximizing the enhancement of the phosphorescence intensity.

In the present invention, an anisotropic metal nanoparticle-dielectric core-shell nanostructure having an aspect ratio capable of forming a double plasma resonance band is used. That is to say, the plasma ribbon is formed at a position where the emission wavelength of the LED chip and the absorption wavelength of the luminescent material are formed by using a double plasma resonance band, and the remaining plasma resonance bands are formed in a region of the emission wavelength of the luminescent material, thereby simultaneously Excitation (absorption) enhancement and emission enhancement are performed, and eventually the enhancement of phosphorescence intensity is maximized.

In general, a metal nanoparticle having a single surface plasma tape is prepared by a solution process in a bottom-up manner, or a nanoparticle obtained by etching a metal film from a top-down manner and distributed on a substrate is used. structure. However, to achieve both excitation enhancement and emission enhancement of the luminescent material, it is quite difficult to maximize the enhancement of phosphorescence intensity. For example, if a spherical nanostructure (nanosphere) is used in a white LED using an LED chip having a near-ultraviolet or blue-light wavelength and a yellow light-emitting material such as Yttrium Aluminum Garnet (YAG) The surface plasma belt of the nanosphere is generally formed in a region of 400 nm to 500 nm, and the near ultraviolet or blue wavelength of the LED wafer effectively overlaps with the absorption wavelength of the yellow light emitting material, resulting in an increase in absorption of the yellow light emitting material. So that the excitation enhancement system can be expected. However, since the emission wavelength of the yellow light-emitting material and the surface plasma belt of the nanostructure do not effectively overlap each other, an increase in internal quantum efficiency (that is, emission enhancement) may not be expected, so that the enhancement of the phosphorescence intensity cannot be maximized. .

However, if the gold nanoparticles are used in the same white LED, the surface plasma strip is formed in a region of 500 nm to 600 nm, so that the emission wavelength of the yellow light-emitting material and the surface plasma belt of the gold nanoparticle can effectively overlap each other. An increase in the internal quantum efficiency (i.e., emission enhancement) described above can be achieved. However, the surface plasma strip of the gold nanoparticles may not be associated with the LED wafer The near ultraviolet or blue wavelengths effectively overlap such that it is difficult to achieve an excitation enhancement by increasing the absorption of the luminescent material.

In order to implement white LEDs of high color purity, two or more blue, green, red or yellow luminescent materials having different emission wavelengths can be used. However, in this case, the use of metal nanoparticle or nanostructures forms a single surface plasma belt, making it difficult to achieve simultaneous emission enhancement of different luminescent materials. Therefore, it is quite difficult to achieve a light-converting light-emitting device having high color purity and brightness.

At the same time, in order to induce the emission enhancement of the luminescent material using the surface plasma resonance of the metal nanoparticle, the position of the luminescent material and the metal nanoparticle, and the distance between the luminescent material and the metal nanoparticle should be considered, and The spectrum overlaps. That is, by locally increasing the electric field formed around the metal nanoparticles, in order to maximize the enhancement of the phosphorescence intensity, it is necessary to ensure a proper distance between the metal nanoparticles and the luminescent material.

For example, in the case where the metal nanoparticle and the luminescent material are in close proximity to each other, that is, a distance of 5 nm or less, the luminescent material may be quenched by the transfer of energy from the excited luminescent material to the surface of the metallic nanoparticle. . However, in the case where the metal nanoparticle and the luminescent material are located apart from each other, that is, at a distance of 1 μm or more, the luminescent material may not be able to reach an electric field formed on the surface of the metal nanoparticles, and it is difficult to achieve an enhancement of the phosphorescence intensity.

If the anisotropic metal nanoparticle-dielectric core-shell nanostructure is applied according to the present invention, the metal-dielectric core-shell nanostructure can maintain a fixed interval between the luminescent material and the metal nanoparticle at a dielectric shell thickness. It is expected that local electric field enhancement occurs at the surface of the metal nanoparticle, thereby providing a light-emitting device having enhanced phosphorescence intensity.

In addition, the dielectric shell of the anisotropic metal nanoparticle-dielectric core-shell nanostructure can maintain the shape of the anisotropic metal nanoparticle in the local high-temperature heat generating device, and suppress the energy from The excitation luminescent material is transferred to the surface of the metal nanoparticle, thereby preventing the luminescent material from being quenched, and a light-emitting device having improved emission efficiency and durability is implemented.

The present invention induces anisotropic metal nanoparticles by having an appearance ratio - The dielectric core-shell nanostructures together enhance the emission of the luminescent material introduced into the illuminating device, providing a luminescent device with improved emission efficiency and durability.

The anisotropic metal nanoparticle-dielectric core-shell nanostructure used in the present invention relates to a structure having nanometer-sized metal particles having an appearance ratio of a horizontal axis and a vertical axis, constituting a core and surrounding in a shell form A dielectric material of a metal particle core.

The anisotropic metal nanoparticles may comprise a metal such as silver, gold, aluminum, copper, lithium, palladium, platinum or alloys thereof. According to the light-emitting device of the present invention, the metal species used as the source material of the anisotropic metal nanoparticles can be selected in consideration of spectral overlap, and the appearance ratio can be obtained by the position of the light-emitting device according to the wavelength of the light-emitting device, the absorption and emission wavelength of the light-emitting material. The position is adjusted by the type of metal selected.

For example, in order to enhance the phosphorescence intensity of the luminescent material having the absorption and emission wavelengths in the ultraviolet light region, it is advantageous to use aluminum nanoparticle having a plasma belt in the ultraviolet region, or a metal other than aluminum and aluminum. alloy. Meanwhile, in order to enhance the phosphorescence intensity of the luminescent material having the absorption and emission wavelengths in the visible light region, silver or gold nanoparticles having a surface plasma belt in the visible light region, or silver or gold and other metals may be advantageously used. alloy.

Non-isotropic metal nanoparticles can generally be prepared by a bottom-up process or a top-down process. According to the former method, a metal precursor, a reducing agent, and an interfacial surfactant are mixed to prepare a solution. According to the latter method, the nanoparticles can be prepared by etching a metal film (for example, by electron beam lithography). From the viewpoint of manufacturing cost, a bottom-up method is preferably applied. The anisotropic metal nanoparticles are used to form a nanocolumn by preparing a metal seed and then growing the metal seed into an anisotropic column. Here, the appearance of the nanocolumn can be controlled using parameters (including seed size, relative ratio of metal seed to metal precursor, pH of solution, temperature, etc.) during the preparation of the nanocolumn. Alternatively, after preparing the nanocolumn, the nanocolumn can be etched, or a metal precursor can be added to regrind. Techniques for preparing anisotropic metal nanoparticles and controlling the aspect ratio are well known in the art, and the specific preparation of the anisotropic metal nanoparticles is described by way of examples.

The nanoparticle preferably has a lateral dimension between 1 nm and 1 μm, and a longitudinal dimension between 1 nm and 1 μm, and more preferably a lateral dimension between 10 nm and 40 nm, and a longitudinal dimension. It is in the range between 10 nm and 400 nm. Further, the anisotropic metal nanoparticles have an aspect ratio of between 1.1 and 10. Under the foregoing range, the nanoparticles exhibit a relatively high scattering rate, which is advantageous for achieving an emission enhancement of the luminescent material.

In the anisotropic metal nanoparticle-dielectric core-shell nanostructure, examples of the dielectric material may include cerium oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), and titanium dioxide (TiO ₂ ). ), magnesium oxide (MgO), zirconium dioxide (ZrO ₂ ), lead oxide (PbO), boron trioxide (B2O ₃ ), calcium oxide (CaO) and barium oxide (BaO), which can be based on dielectric materials The refractive index and optical properties are used.

According to the anisotropic metal nanoparticle-dielectric core-shell nanostructure of the present invention, the dielectric shell preferably has a thickness ranging between 1 nm and 1 μm in consideration of a strong electric field on the surface of the metal nanoparticles. If the thickness of the dielectric shell is less than the above range, the position of the metal nanoparticles and the luminescent material are too close to each other, causing quenching. If the thickness of the dielectric shell is larger than the above range, the light-emitting device may be located at an electric field generated from the surface of the metal nanoparticles, so that the enhancement of the phosphorescence intensity is difficult to achieve.

In the present invention, a luminescent material refers to an organic or inorganic material comprising semiconductor quantum dots capable of expressing fluorescence or phosphorescence according to an emission mechanism. However, the invention is not limited to those luminescent materials listed herein. In order to achieve a high color purity white LED, a single luminescent material or a plurality of luminescent materials may be used.

In the present invention, the luminescent material may comprise a combination of a semiconductor LED having a near ultraviolet or blue emission wavelength and a luminescent material having a longer emission wavelength than the LED.

In the present invention, a nitrogen-containing semiconductor emitting near-ultraviolet light or blue light can be used for the light-emitting device. In addition, various light-emitting devices that emit red light and green light can be used.

In the present invention, when the light-emitting layer of the light-emitting device is formed, the anisotropic metal nanoparticle-dielectric core-shell nanostructure and the light-emitting material may be simply mixed, or a composite having a combination of a light-emitting material and a nanostructure. It can be introduced to form a light-emitting layer. In the case of forming a complex, The optical material can always be located in an enhanced electric field around the anisotropic metal nanoparticles, which is beneficial for achieving an increase in phosphorescence intensity.

According to the light-converting light-emitting device of the present invention, in order to achieve an appropriate spectral overlap between the emission wavelength of the light source of the light-emitting device, the absorption and emission wavelength of the light-emitting material, and the surface plasma tape of the non-isotropic metal nanoparticles or the nanostructure The surface plasma tape can be adjusted by controlling the appearance ratio of the anisotropic metal nanoparticles. That is, the surface plasma tape can be adjusted by controlling the aspect ratio of the anisotropic metal nanoparticles, and as the aspect ratio increases, the longitudinal band moves toward the longer wavelength region. There is no significant change in the lateral band compared to the longitudinal band. Therefore, the plasma belt is preferably adjusted by controlling the composition, size, and appearance ratio of the anisotropic metal nanoparticles according to the spectrum of the LED wafer constituting the light-converting white light-emitting device and the luminescent material. In detail, based on the longitudinal and transverse axes of the anisotropic metal nanoparticles, two or more surface plasma resonance bands are controlled to extend to the near ultraviolet region, the visible region, and the near infrared region. The spectral overlap between the near-ultraviolet or blue wavelength of the source and the absorption and emission wavelengths of the luminescent material is optimized, thereby simultaneously effecting excitation enhancement and emission enhancement of the luminescent material.

Further, core-shell nanoparticles prepared using two or more different metals may be used as the nanoparticle of the present invention to provide an emission wavelength of a light source of the light-emitting device, absorption and emission wavelengths of the light-emitting material, and anisotropy. A suitable spectral overlap between the metal nanoparticle or the surface plasma strip of the nanostructure.

The light-emitting layer can be formed by introducing two or more kinds of anisotropic metal nanoparticle-dielectric core-shell nanostructures having different double plasma resonance bands together with a light-emitting material.

In addition, the present invention can also provide a light-converting light-emitting device comprising an anisotropic metal nanoparticle having a surface overlapping with an emission wavelength of a light source of the light-emitting device or an absorption and emission wavelength of the light-emitting material. A plasma strip, and another surface plasma strip that overlaps the emission wavelength of the luminescent material. The lateral surface plasma strip of the core-shell nano-pillar overlaps with the emission wavelength of the LED wafer, so that the luminescent material can effectively absorb the excitation light of the LED wafer, and excitation enhancement can be achieved. In addition, the emission wavelength of the luminescent material and the longitudinal surface plasma strip of the core-shell nano column are suitably Overlap, and an increase in internal quantum efficiency (ie, excitation enhancement) is achievable. Thus, excitation enhancement and emission enhancement of the luminescent material can be performed at the same time, thereby maximizing the enhancement of phosphorescence intensity.

When a plurality of different luminescent materials are used for the luminescent layer, the present invention provides a light-converting illuminating device comprising two or more surface electric charges overlapping with absorption and emission wavelengths of two or more luminescent materials having different emission wavelengths An anisotropic metal nanoparticle or nanostructure of the plasma resonance band.

In the present invention, in view of the scattering efficiency and the absorption efficiency calculated from the extinction spectrum of the anisotropic metal nanoparticles, it is preferred to use nano particles having a scattering efficiency higher than the absorption efficiency. In this case, the size and appearance ratio of the anisotropic metal nanoparticles are determined by the scattering efficiency and the absorption efficiency for the nanoparticle extinction because the scattering of the metal nanoparticles generally corresponds to the phosphorescence intensity of the luminescent material. Enhance related. In the case of nanospheres, the scattering efficiency is proportional to the sixth power (r ⁶ ) of the radius of the nanoparticle, and the absorption efficiency is related to the quenching of the luminescent material and three times the radius of the nanoparticle (r) The square (r ³ ) is proportional. Therefore, the use of an anisotropic metal nanoparticle having a high scattering ratio facilitates the emission enhancement of the luminescent material. For this purpose, the anisotropic metal nanoparticles preferably have a lateral dimension between 1 nm and 1 μm, and a longitudinal dimension between 1 nm and 1 μm, and more preferably have a lateral dimension between 10 nm and The range between 40 nm, and the range of the longitudinal dimension between 10 nm and 400 nm. Further, the anisotropic metal nanoparticles have an aspect ratio of between 1.1 and 10. Under the foregoing range, the nanoparticles exhibit a relatively high scattering rate, and the double plasma resonance band can be controlled in the visible light region, which is advantageous for achieving emission enhancement of the luminescent material.

In the following, examples of the embodiments of the present invention will be described in detail with reference to the accompanying drawings, which can be easily implemented by those skilled in the art.

1a and 1b are schematic views for explaining the concept of a light-converting white light-emitting device having improved emission efficiency using an anisotropic metal nanoparticle-dielectric core-shell nanostructure according to the present invention. Specifically, FIG. 1a schematically shows an anisotropic metal nanoparticle. A composite of a sub-dielectric core-shell nanostructure and a luminescent material combined with each other, and FIG. 1b schematically illustrates the principle of introducing a composite to a light-emitting layer by a light-emitting device having improved emission efficiency. The light-converting white light-emitting device may comprise a substrate or an LED chip, a luminescent material and an anisotropic metal nanoparticle-dielectric composite and a transparent polymer matrix.

In FIG. 1a, the blue light (or near-ultraviolet light) generated from the LED wafer is absorbed by the luminescent material and converted into red, green, blue or long-wavelength yellow light radiation that is not absorbed by the luminescent material, thereby implementing the LED. The wafer emits white light of color. For example, white light can be performed by using a combination of a non-organic phosphor having a yellow emission wavelength (such as YAG or citrate) and a blue and yellow emission wavelength of a blue (or near-ultraviolet) LED.

Further, with the recently required high color purity light-emitting device, semiconductor quantum dots having various radiation colors of red, green, and blue are used. For example, a technique for implementing a higher color purity white LED has been proposed as a luminescent material by introducing YAG or citrate-based yellow non-organic phosphor powder.

In the present invention, among commercially available luminescent materials, YAG phosphor powder and indium phosphide/zinc sulfide quantum dot system are used as luminescent materials satisfying the above conditions, and various luminescent materials can be used regardless of the kind of materials used.

Herein, the absorption, excitation and emission characteristics of the luminescent material will now be briefly described with reference to FIG. Figure 2a is a graph showing the excitation and emission spectra of a YAG phosphor with a maximum absorption peak at 450 nm and a maximum emission peak at 540 nm. Figure 2b is a graph showing the absorption and emission spectra of indium phosphide/zinc sulfide quantum dots, where the absorption system starts from 600 nm or less, the emission system increases significantly from 400 nm, and the maximum emission peak position is at 630 nm.

In the present invention, a double plasma resonance phenomenon of anisotropic metal nanoparticles is used to carry out a white LED having improved emission efficiency. That is to say, in order to implement a white LED based on a blue LED chip, a plasma strip of non-isotropic metal nanoparticles is designed and synthesized to make the absorption, excitation and emission wavelength of the luminescent material and the emission wavelength of the blue LED chip. Have room The effect spectrum overlaps.

The anisotropic metal nanoparticles may comprise a metal such as silver, gold, aluminum, copper, lithium, palladium, platinum, and alloys thereof. According to the light-emitting device of the present invention, the source metal species of the anisotropic metal nanoparticles can be selected in consideration of spectral overlap. The source metal species of the non-isotropic metal nanoparticles can be selected according to the position of the emission wavelength of the light-emitting device and the position of the absorption and emission wavelengths of the light-emitting material, thereby adjusting the aspect ratio.

3 is a transmission electron micrograph of anisotropic metal nanoparticles having two or more surface plasma strips in the near-ultraviolet, visible, and near-infrared regions. Figure 4 is a graph showing the ultraviolet-visible spectrum of a corresponding transmission electron microscope image.

Specifically, FIG. 3a illustrates a transmission electron micrograph of a gold nano column synthesized by gold seed crystal growth with an added gold precursor, and FIGS. 3b and 3c are illustrated by gold-based A gold-silver core-shell nanocolumn synthesized by a nano-pillar seed crystal and a silver precursor added thereto. In Figures 3b and 3c, the black portion represents the gold core and the portion surrounding the gold core is the silver shell. In this context, the thickness of the silver shell can be controlled by controlling the relative ratio of the gold nanorods that become nuclei to the silver precursor. As the amount of silver precursor added increases, the thickness of the silver shell gradually increases from Figure 3b to that shown in Figure 3c.

4 is a graph showing the ultraviolet-visible spectrum of the anisotropic metal nanoparticles corresponding to the transmission electron micrograph shown in FIG. 3. Specifically, FIG. 4a illustrates the ultraviolet-visible spectrum of the gold nano column corresponding to the transmission electron micrograph shown in FIG. 3a. The Jinnai column has a transverse band (T-band) and a longitudinal band (L-band) at 512 nm and 855 nm, respectively. Figure 4b shows the ultraviolet-visible spectrum of the gold nano column corresponding to the transmission electron micrograph shown in Figure 3b. Each gold-silver core-shell nanocolumn has a transverse plasma zone and a longitudinal plasma zone at 450 nm and 600 nm, respectively. Figure 4c shows the ultraviolet-visible spectrum of a gold nanocolumn column corresponding to the transmission electron micrograph shown in Figure 3c. Each nanocolumn has a transverse plasma belt and a longitudinal plasma belt at 450 nm and 565 nm, respectively. That is to say, the surface plasma belt of the nanoparticle can be controlled by adjusting the relative ratio of the gold nano column to the silver precursor.

That is, as shown in Figure 4a, the surface of the plasma column from the gold nano column is used as the crystal As the amount of silver precursor added increases, the surface plasma band of the nanoparticle gradually moves toward the short wavelength region, and finally forms in the visible region and can be accurately controlled.

In an embodiment of the invention, the spectral overlap between the absorption, excitation, and emission wavelengths of the LED wafer and the luminescent material and the surface plasma strip of the metal nanoparticle is provided, using a gold-silver core-shell nanostructure as an example, The viewpoint of the present invention is not limited to this.

Figure 5 is a schematic illustration of the spectral overlap between the absorption, excitation and emission wavelengths of the LED wafer and the luminescent material and the surface plasma strip of the anisotropic metal nanoparticles.

As shown in FIG. 5a, in order to improve the emission efficiency of a light-emitting device including a blue LED chip and a YAG phosphor, an anisotropic metal nanoparticle is applied. In this case, a gold-silver nanometer column which can effectively overlap the spectrum of the blue LED chip and the YAG phosphor powder as shown in Fig. 4c is preferably used.

As shown in FIG. 5b, in a light-emitting device comprising a blue LED chip and an indium phosphide/zinc sulfide quantum dot, the spectrum of the blue LED chip and the indium phosphide/zinc sulfide quantum dot shown in FIG. 4b is preferably used. Effectively overlapping gold and silver nano columns.

Alternatively, as shown in Figure 5, the respective combination between each LED wafer, luminescent material, and anisotropic metal nanoparticles provides only an illustration of an embodiment for spectral overlap optimization. An increase in emission efficiency can be expected by a combination of different luminescent materials and non-isotropic metal nanoparticles.

In the present invention, in order to improve the emission efficiency of the light-emitting device, before the non-isotropic metal nanoparticles and the light-emitting material are introduced into the light-emitting layer, the surface of the anisotropic metal nanoparticles is coated with a dielectric material, thereby manufacturing a non- Isotropic metal nanoparticle-dielectric core-shell nanostructure.

The nanostructure allows the luminescent material and the metal nanoparticle to be maintained at a fixed interval in the thickness of the dielectric shell, whereby the local electric field of the luminescent material on the surface of the metal nanoparticle is enhanced and the enhancement of phosphorescence intensity is maximized. In addition, the dielectric shell of the nanostructure can maintain the shape of the anisotropic metal nanostructure in a light-emitting device that locally generates high-temperature heat, and suppress the transfer of energy from the excitation luminescent material to the surface of the metal nanoparticle, thereby Prevent the luminescent material from quenching.

In the anisotropic metal nanoparticle-dielectric core-shell nanostructure, examples of the dielectric material may include ceria, alumina, titania, magnesia, zirconium dioxide, lead oxide, and trioxide. Boron, calcium oxide and cerium oxide can be used depending on the refractive index and optical properties of the dielectric material.

Figure 6 is a diagram showing a transmission electron micrograph of an anisotropic metal nanoparticle-dielectric core nanostructure. Specifically, FIGS. 6a and 6b illustrate a gold-silver-ceria core shell nanostructure having a surface of a nanoparticle coated with a ceria shell and using the gold and silver shown in FIGS. 3b and 3c. Nano column. The method of forming the anisotropic metal nanoparticle-dielectric core-shell nanostructure will be described with reference to the illustrated examples.

As shown in Fig. 6, the black portion represents the gold core, the gray portion around the gold core represents the silver shell, and the relatively gray portion around the silver shell represents the ceria shell.

The non-isotropic metal nanoparticle-dielectric core-shell nanostructure can be simply mixed with the luminescent material of the luminescent layer to be introduced into the illuminating device, or with the luminescent material to be introduced as a composite of the nanostructure and the luminescent material. Form combination (see Figure 1b).

As shown in Figure 1a, the composite of the nanostructure and the luminescent material refers to the product of the non-covalent bond interaction between the anisotropic metal nanoparticle-dielectric core-shell nanostructure and the luminescent material.

That is, the surface of the nanostructure is modified with a decane or titanate coupling agent containing a functional group such as an amine group, a thiol, and an epoxy compound, and then mixed with a luminescent material, thereby forming an anisotropic The metal nanoparticle-composite of a dielectric core-shell nanostructure and a luminescent material combined with each other.

For example, the nanostructured cerium oxide surface is modified with a decane coupling agent having an amine group such as 3-aminopropyltrimethoxysilane (APTMS), such that The surface of the cerium oxide is decanolated, and a complex is formed by a non-covalent bond to the surface of the luminescent material (for example, YAG fluorescing powder or indium phosphide/zinc sulfide quantum dot) via a combination of an amine group and a nanostructure.

Further, the surface of the luminescent material may be first modified with a decane or titanate coupling agent. In this case, the composite of the nanostructure and the luminescent material can be manufactured in the same manner as described above.

In the case where the composite is formed in this manner, the luminescent material can always be located in a strong electric field around the anisotropic metal nanoparticles, which is advantageous for the enhancement of the phosphorescence intensity.

The coupling agent has a structure of a decane coupling agent [R _n SiX _4-n ] or a titanate coupling agent [R _n TiX _4-n ] comprising at least two different reaction groups, and the X system is selected from the group consisting of an alkoxy group and a decyloxy group. One or more hydrolyzable functional groups of the group consisting of an amine group and a chlorine group, the R system comprising one or more non-hydrolyzable functional groups composed of an amine group, a thiol and an epoxy compound, and n An integer between 1 and 3.

Further, as with the shell of the anisotropic metal nanoparticles-dielectric core-shell nanostructure, the coupling agent may also separate the luminescent material and the anisotropic metal nanoparticles from each other by a predetermined distance.

Figure 7 is a graph showing the emission spectrum of a solution comprising an anisotropic metal nanoparticle-dielectric core-shell nanostructure and a luminescent material introduced therein together. Specifically, FIG. 7 illustrates an emission spectrum of a complex solution comprising an anisotropic metal nanoparticle-dielectric core-shell nanostructure and a luminescent material combined with each other. Here, the excitation wavelength band used for combination with the blue LED chip is fixed at 442 nm.

Figure 7a is a graph showing the emission spectrum of a solution having the combination of the anisotropic metal nanoparticles-dielectric nanostructure and YAG phosphor shown in Figure 6b. In this paper, the phosphorescence intensity (indicated by the solid line) introduced into the nanostructure is increased at the maximum emission peak (ie, 550 nm) of the YAG phosphor compared to the phosphorescence intensity (indicated by the dotted line) in which the nanostructure is not introduced. 2.6 times. Figure 7b is an emission spectrum of a solution having the combination of the anisotropic metal nanoparticles-dielectric nanostructure and the indium phosphide/zinc sulfide quantum dots shown in Figure 6a. In this paper, the phosphorescence intensity (indicated by the solid line) introduced into the nanostructure is the maximum emission peak of the indium phosphide/zinc sulfide quantum dot (ie 630 nm) compared to the phosphorescence intensity (indicated by the dashed line) without the introduction of the nanostructure. The system is increased by about 2.4 times.

At the same time, in the case of using isotropic metal nanospheres, isotropic metal nanoparticles The ball behaves differently than the non-isotropic metal. Figure 8a is a transmission electron micrograph of a metal nanosphere-dielectric core-shell nanostructure, in which the black portion represents the gold nanosphere and the relatively bright portion around the gold nanosphere represents the ceria shell. . Unlike non-isotropic metal nanoparticles, Figure 8b shows a single plasma strip of metal nanosphere at about 530 nm. The method for forming the metal nanosphere-dielectric core-shell nanostructure will be described in detail through comparative examples.

Figure 9 is a graph showing the emission spectrum of a solution containing a composite of a metal nanosphere-dielectric core-shell nanostructure and a luminescent material combined with each other (as shown in Fig. 8), which is represented by unequal It is produced by the same method of coupling the nanoparticles to the luminescent material. Here, the excitation wavelength is fixed at 442 nm to compare with the case of using an anisotropic nanostructure.

Figure 9a is a graph showing the emission spectrum of a solution having an isotropic metal nanoparticle-dielectric nanostructure and YAG phosphor powder combined with each other as shown in Figure 8a. Unlike Figure 7a, the phosphorescence intensity of the YAG phosphor did not change significantly, and when the nanostructure was introduced, the phosphorescence intensity (indicated by the dashed line) was slightly reduced at the maximum emission peak of the YAG phosphor (i.e., 550 nm). As confirmed by the use of indium phosphide/zinc sulfide quantum dots in Fig. 9b, when a nanostructure was introduced, the phosphorescence intensity (indicated by the solid line) was slightly reduced at about 630 nm as shown in Fig. 9a.

That is to say, isotropic metal nanospheres are generally used for excitation enhancement or emission enhancement of luminescent materials. The enhancement of the phosphorescence intensity of the luminescent material can be expected by appropriately adjusting the material, size, shape, the excitation properties of the nanoparticles used, the absorption of the plasma band on the surface of the luminescent material, the spectral overlap with the emission wavelength, or the overlap with the excited spectrum. .

Meanwhile, even if an anisotropic metal nanoparticle having the same shape is used, the emission is carried out through the composite comprising the anisotropic metal nanoparticle-dielectric core-shell nanostructure and the luminescent material shown in FIG. The reinforcement is not expected unless the distance between the metal nanoparticles and the luminescent material is properly adjusted. Figure 10 is a graph showing the emission spectrum of a composite solution comprising an anisotropic metal nanoparticles (as shown in Figure 3) without a dielectric shell and a luminescent material introduced together. Here, the excitation wavelength is fixed at 442 nm for comparison with the use of an anisotropic metal nanoparticles-dielectric core-shell structure and a luminescent material. Detailed experimental methods will be described in detail through comparative examples.

Figure 10a is a graph showing the emission spectrum of a solution having an emission spectrum of a solution in which the anisotropic metal nanoparticles and YAG phosphors shown in Figure 3c are combined with each other. As confirmed in Fig. 10a, the phosphorescence intensity is reduced at the maximum emission peak (i.e., 550 nm) of the dielectric-free shell YAG phosphor. Figure 10b is a graph showing the emission spectrum of a solution having an emission spectrum of a solution in which the anisotropic metal nanoparticles shown in Figure 3b and the indium phosphide/zinc sulfide quantum dots are combined with each other. As confirmed in Fig. 10b, the phosphorescence intensity (indicated by the solid line) is decreasing at about 630 nm as shown in Fig. 10a.

That is, in the case of using an anisotropic metal nanoparticles coated with a dielectric-free ceria shell, the luminescent material may be quenched by the transfer of energy from the excited luminescent material to the surface of the metal nanoparticles. Therefore, in order to prevent quenching of the luminescent material when the luminescent material emission enhancement is optimized, the anisotropic metal nanoparticles-dielectric core-shell nanostructure shown in Fig. 6 is advantageously used.

A luminescent material that can be used with a light-converting white light-emitting device, whether of an organic or inorganic luminescent material, can comprise a luminescent material that enhances phosphorescence intensity enhancement, including semiconductor quantum dots. In order to achieve a high color purity white LED, a single luminescent material or a plurality of luminescent materials may be used. In the light-converting white light-emitting device, the luminescent material may use a nitrogen-containing semiconductor material that emits near-ultraviolet light or blue light. In addition, various luminescent materials capable of emitting red light, green light, and the like can also be used.

In order to fabricate a light-converting white light-emitting device with enhanced emission efficiency using an anisotropic metal nanoparticle-dielectric core-shell nanostructure, a synthetic anisotropic metal nanoparticle-dielectric nanostructure and luminescence The material is mixed with a light transmissive polymer (eg, polymethyl methacrylate, epoxy compound, or epoxy resin) to form a film, and the film is on a near-ultraviolet or blue LED wafer. Alternatively, in order to manufacture a light-converting white light emitting device, the mixed solution may be uniformly applied to the LED wafer, which will be described in detail by way of example.

As shown in FIG. 1b, in the case where a white LED is implemented by a combination of a near-ultraviolet light or a blue LED chip and a yellow light-emitting material, gold-silver-cerium oxide nanoparticles and a light-emitting material are dispersed on the light-emitting layer. In a transparent polymer substrate. Herein, the anisotropic metal nanoparticles are not limited to the gold-silver core-shell nanostructure, and are used to form two or more kinds of near-ultraviolet light. Or the metal nanoparticle of the surface plasma zone of the visible light region may be used as an anisotropic metal nanoparticle. Meanwhile, in the case of implementing a high color purity white LED, a plurality of luminescent materials having different emission wavelengths may be introduced into the luminescent layer.

In this case, as shown in FIG. 11, the luminescent material can be prepared by preparing an anisotropic metal nanoparticle-dielectric core-shell nanostructure and a composite of green light-emitting quantum dots, or an anisotropic metal naphthalene. A rice particle-dielectric core-shell nanostructure and a complex of red-emitting quantum dots are formed. Alternatively, the luminescent layer can be prepared by a composite of a metal nanoparticle-dielectric core-shell nanostructure and a yellow-light-emitting inorganic phosphor, or a metal nanoparticle-dielectric core-shell nanostructure. Formed with a composite of red light-emitting quantum dots. In a manner similar to that shown in Figure 1b, a high color purity white LED with improved emission efficiency can be fabricated by forming white LEDs.

example Example 1: Synthesis of anisotropic metal nanoparticles

Anisotropic metal nanoparticles having an aspect ratio are synthesized to form a gold nano column for controlling a surface plasma belt. First, synthesize gold seeds. For this purpose, sodium borohydride (NaBH ₄ ) (0.01 M, 0.6 ml) was added to tetrachloroalloy acid (HAuCl ₄ ) (0.01 M, 0.25 ml) and cetyltrimethylammonium bromide (CTAB) (0.1 M) , 9 ml) in a mixed solution. Stirring was then vigorously carried out for 2 minutes and the resultant was stored in an incubator maintained at 29 ° C for 2 hours. Next, a gold nano column growth solution was prepared. Ascorbic acid (0.1M) was stirred when a mixed solution of tetrachloroalloy (0.01 M, 2 ml), silver nitrate (AgNO ₃ ) (0.01 M, 0.4 ml) and cetyltrimethylammonium bromide (0.1 M, 40 ml) was stirred. An aqueous solution of 0.32 ml) and hydrogen chloride (1.0 M, 0.8 ml) was sequentially added to the mixed solution. While the mixed solution was continuously stirred, 0.01 ml of the prepared seed solution was added to the resultant. After stirring for another 10 seconds, the stirring was stopped and stored in an incubator maintained at 29 ° C for 6 hours.

In order to accurately control the double plasma resonance band in the visible light region, a gold-silver core-shell nanostructure is synthesized. The gold nano column solution was centrifuged at 10,000 rpm for 30 minutes, the upper layer fluid was poured off, the precipitate layer was collected, and the collected precipitate layer was redispersed in a solution of cetyltrimethylammonium chloride (CTAC) (0.08 M, 40 ml). 10 ml of gold nano column solution is added to silver nitrate (0.01M, In 2 ml) and an aqueous solution of ascorbic acid (0.1 M, 0.5 ml), the resultant was then undisturbed in an oil bath maintained at 80 ° C for 3 hours, thereby synthesizing the gold-silver core-shell nanostructure shown in Fig. 3b. In the reaction, the addition of an aqueous solution of silver nitrate (0.01 M, 3 ml) and ascorbic acid (0.1 M, 0.5 ml) resulted in the synthesis of the gold-silver core-shell nanostructure shown in Fig. 3c. The thickness of the silver shell can be adjusted by adjusting the amount of silver nitrate added. The gold-silver nano-column solution was centrifuged at 8000 rpm for 30 minutes, the upper layer fluid was poured off, the precipitate layer was collected, and the collected precipitate layer was redispersed in the tri-distilled water.

Example 2: Synthesis of anisotropic metal nanoparticles - dielectric core-shell nanostructure

A 0.1 wt% gold-silver anisotropic nano column aqueous solution synthesized in Example 1 was prepared. A mixed solution for coating cerium oxide, 10 μl of a thiol propane-triethoxy decane (MPTMS) solution and 1 ml of ethanol was added to a gold-silver anisotropic column solution, followed by stirring for 2 hours. A sodium citrate solution (2.0 M, 40 μl) was added to the mixed solution and stirred at room temperature for 24 hours, thereby synthesizing a gold-silver-ceria core-shell nanostructure.

The gold-silver-niobium oxide nanoparticle solution was centrifuged at 5000 rpm for 30 minutes, the upper layer fluid was poured off, the precipitate layer was collected, and the precipitate layer was collected and redispersed in ethanol.

Example 3: Preparation of an anisotropic metal nanoparticle-composite of a dielectric core-shell nanostructure and a light-emitting device and evaluation of emission properties

20 μl of 3-aminopropyl-trimethoxydecane was added to the ethanol solution containing the gold-silver-ceria core-shell nanoparticles dispersed in Example 2, followed by stirring at room temperature for 24 hours and centrifuging at 5000 rpm. After 30 minutes, the upper layer fluid was poured off, the precipitate layer was collected, and the precipitate layer was collected and then dispersed in a tetrahydrofuran (THF) solvent.

YAG phosphor powder or indium phosphide/zinc sulfide quantum dots were added to the resultant solution and stirred for 2 hours. Here, the amount of YAG phosphor powder or indium phosphide/zinc sulfide quantum dots may be added in the range of 0.001 wt% and 50 wt%.

In order to analyze the change in the phosphorescence intensity of the mixed solution, the light is used to excite the fluorescent light. Spectrum. To analyze the emission of the solution, a cadmium cadmium laser was used as the excitation source, and the excitation wavelength was fixed at 442 nm.

A solution containing gold-silver-niobium dioxide nanoparticles and a solution containing no gold-silver-niobium oxide nanoparticles were excited at 442 nm to measure the emission spectrum and observe changes in phosphorescence intensity. The emission spectrum as shown in Figure 7 was then measured. As shown in Fig. 7, the introduction of a solution containing nanoparticle according to the present invention exhibits a higher emission efficiency than a solution containing no nanoparticle.

Comparative Example 1: Synthesis of spherical isotropic metal nanoparticles

In order to synthesize a gold nanosphere, a gold seed crystal is first prepared. For this purpose, sodium borohydride (0.01 M, 0.6 ml) was added to a mixed solution of tetrachloroalloy acid (0.01 M, 0.25 ml) and cetyltrimethylammonium bromide (0.1 M, 7.5 ml). Stirring was then vigorously carried out for 2 minutes and the resultant was stored in an incubator maintained at 29 ° C for 2 hours. Next, a gold nanoparticle growth solution was prepared. An aqueous solution of ascorbic acid (0.1 M, 3.8 ml) was stirred and added to a mixed solution of tetrachloroalloy acid (0.01 M, 0.8 ml), cetyltrimethylammonium bromide (0.1 M, 6.4 ml) and water (32 ml). While the mixed solution was continuously stirred, the synthetic seed solution was diluted 10-fold, followed by the addition of 0.06 ml of the diluted solution. After stirring for another 10 seconds, the stirring was stopped and stored in an incubator maintained at 29 ° C for 6 hours, thereby synthesizing the gold nanoparticles shown in Fig. 8a.

Comparative Example 2: Synthesis of spherical isotropic metal nanoparticles - dielectric core-shell nanostructure

An aqueous solution of 0.1 wt% of gold nanoparticles synthesized in Comparative Example 1 was prepared. For the coating of cerium oxide, a mixed solution of 10 μl of a thiol propane triethoxy decane (MPTMS) solution and 1 ml of ethanol was added to the gold nanoparticle solution, followed by stirring for 2 hours. A sodium citrate solution (2.0 M, 40 μl) was added to the mixed solution and stirred at room temperature for 24 hours, thereby synthesizing a gold-ceria core-shell nanostructure.

The gold-cerium oxide nanostructure solution was centrifuged at 10,000 rpm for 30 minutes, the upper layer fluid was poured off, the precipitate layer was collected, and the precipitate layer was collected and redispersed in ethanol.

Comparative Example 3: Preparation of a spherical isotropic metal nanoparticle-composite of a dielectric core-shell nanostructure and a light-emitting device and evaluation of emission properties

20 μl of 3-aminopropyl-trimethoxydecane was added to the ethanol solution containing the 0.1 wt% gold-ceria core-shell nanostructure synthesized in Comparative Example 2, followed by stirring at room temperature for 24 hours and at 10,000 rpm. After centrifugation for 30 minutes, the upper layer fluid was poured off, the precipitate layer was collected, and the precipitate layer was collected to be dispersed in a tetrahydrofuran solvent. YAG phosphor powder or indium phosphide/zinc sulfide quantum dots were added to the resultant solution and stirred for 2 hours. Here, the amount of YAG phosphor powder or indium phosphide/zinc sulfide quantum dots may be added in the range of 0.001 wt% and 50 wt%.

In order to analyze the change in the phosphorescence intensity of the mixed solution, a photoexcited fluorescence spectrum was used. To analyze the emission of the solution, a cadmium cadmium laser was used as the excitation source, and the excitation wavelength was fixed at 442 nm.

A solution containing gold-niobium dioxide nanoparticles and a solution containing no gold-niobium oxide nanoparticles were excited at 442 nm to measure the emission spectrum and observe changes in phosphorescence intensity. The emission spectrum as shown in Figure 9 was then measured.

Comparative Example 4: Preparation of a composite of non-dielectric shell anisotropic metal nanoparticles and a light-emitting device and evaluation of emission properties

The aqueous solution containing the dispersion of the non-isotropic metal-niobium oxide nanoparticles synthesized in Example 1 was centrifuged at 10,000 rpm for 30 minutes, the upper layer fluid was poured off, the precipitate layer was collected, and the precipitate layer was collected and then dispersed in a tetrahydrofuran solvent.

YAG phosphor powder or indium phosphide/zinc sulfide quantum dots were added to the resultant solution and stirred for 2 hours. Here, the amount of YAG phosphor powder or indium phosphide/zinc sulfide quantum dots may be added in the range of 0.001 wt% and 50 wt%.

In order to analyze the change in the phosphorescence intensity of the mixed solution, a photoexcited fluorescence spectrum was used. To analyze the emission of the solution, a cadmium cadmium laser was used as the excitation source, and the excitation wavelength was fixed at 442 nm.

A solution containing gold-niobium dioxide nanoparticles and a solution containing no gold-niobium oxide nanoparticles were excited at 442 nm to measure the emission spectrum and observe changes in phosphorescence intensity. The emission spectrum as depicted in Figure 10 is then measured.

As is apparent from the examples and comparative examples, according to the present invention, in the case of using a metal nanosphere or a metal nano column using a non-core-shell structure, the use of an anisotropic metal nanoparticle is used, which has two types. In the case of an anisotropic metal nanoparticle-dielectric core-shell nanostructure of an appearance ratio of a plurality of surface plasma resonance bands, excitation enhancement and emission enhancement of the luminescent material can be induced simultaneously. In addition, since the metal-dielectric core-shell nanostructure can maintain the luminescent material and the metal nanoparticle at a fixed interval in the thickness of the dielectric shell, local electric field enhancement can be expected on the surface of the metal nanoparticle. Further, the shape of the anisotropic metal nanoparticles can be maintained within the core-shell structure, thereby achieving a light-emitting device having improved emission efficiency and durability.

While the invention has been shown and described with reference to the embodiments of the embodiments of the invention The present invention is therefore to be considered in all respects of

Claims (17)

A light-emitting device comprising: an anisotropic metal nanoparticle-dielectric core-shell nanostructure, comprising an anisotropic metal nanoparticle having the ability to form two or more surface plasma resonance bands An aspect ratio, and a dielectric shell coated on the surface of the metal nanoparticle; and a luminescent material; wherein the anisotropic metal nanoparticles form two or more surface plasma resonance bands having a spectrum in which the absorption and emission wavelengths of the luminescent material overlap with the emission wavelength of the light source of the illuminating device; one of the surface plasmon resonance bands overlaps with an emission wavelength of a near-ultraviolet light or a blue light source, and the other The emission wavelengths of the materials overlap. The illuminating device of claim 1, wherein the anisotropic metal nanoparticles have two or more kinds of nanoparticles of different metals present in a core-shell structure. The illuminating device of claim 1, wherein the anisotropic metal nanoparticles are metal nano columns, each of the metal nano columns having different lengths on the vertical axis and the horizontal axis. The illuminating device of claim 1, wherein the anisotropic metal nanoparticles are an alloy of two or more different metals. The illuminating device of claim 1, wherein the anisotropic metal nanoparticles comprise one or more groups selected from the group consisting of silver, gold, aluminum, copper, lithium, palladium, platinum, and alloys thereof. group. The illuminating device according to claim 1, wherein the anisotropic metal nanoparticles have a lateral dimension in a range between 1 nm and 1 μm, and a longitudinal dimension in a range between 1 nm and 1 μm. The illuminating device of claim 1, wherein the anisotropic metal nanoparticles have an appearance ratio between 1.1 and 10. The light-emitting device of claim 1, wherein the non-isotropic metal nanoparticle-dielectric core-shell nanostructure dielectric material comprises one or more selected from the group consisting of cerium oxide and A group consisting of alumina, titania, magnesia, zirconium dioxide, lead oxide, boron trioxide, calcium oxide, and cerium oxide. The light-emitting device of claim 1, wherein the dielectric shell of the anisotropic metal nanoparticle-dielectric core-shell nanostructure has a thickness between 1 nm and 1 μm. The illuminating device of claim 1, wherein the anisotropic metal nanoparticle-dielectric core nanostructure is combined with the luminescent material on a surface thereof to form a luminescent layer, or the luminescent material. The surface is combined with the anisotropic metal nanoparticle-dielectric core-shell nanostructure to form a light-emitting layer. The light-emitting device of claim 1, wherein one of the surface plasma resonance bands of the anisotropic metal nanoparticles is formed in a region of 300 nm to 480 nm, and the other is formed at 500 nm to 700 nm. region. The illuminating device of claim 1, wherein the anisotropic metal nanoparticle-dielectric nucleocapsid nanostructure comprises two or more kinds of anisotropic metal nanoparticles-dielectric Nuclear shell nanostructure. The illuminating device of claim 1, wherein the surface of the dielectric shell or the surface of the luminescent material in the anisotropic metal nanoparticle-dielectric core nanostructure comprises at least two A decane coupling agent or a titanate coupling agent having different functional groups is modified. The illuminating device according to claim 13, wherein the decane coupling agent has a structure of [RnSiX4-n], the titanate coupling agent has a structure of [RnTiX4-n], and the X system is selected from the group consisting of an alkoxy group, One or more of the group consisting of a decyloxy group, an amine group, and a chlorine group, the R group comprising one or more functional groups composed of an amine group, a thiol, and an epoxy compound, and the n series is 1 An integer between 3 and 3. The illuminating device of claim 1, wherein the illuminating device comprises two or more luminescent materials, and two or more anisotropic metal nanoparticles-dielectric nucleocapsid nanoparticles structure. The illuminating device of claim 1, wherein the illuminating device comprises a luminescent layer, And the luminescent layer is composed of a coating composition comprising the anisotropic metal nanoparticle-dielectric nanostructure, the luminescent material, and polymethyl methacrylate, epoxy compound, oxime resin or a mixture thereof Formed. The illuminating device of claim 1, wherein the luminescent material is an organic material having a fluorescent or phosphorescent property, a semiconductor quantum dot material, an inorganic material, or a combination thereof.